Department of Chemistry

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Open Access
Photophysical and sensorial behaviour of different chromophoric systems comprising electron donor-acceptor units
(University of North Bengal, 2023) Rahman, Ziaur; Das, Sudhir Kumar
Research on developing new electron donor–acceptor (EDA) based molecular systems, which benefit from extended π-conjugation, is a rapidly growing research area. That has resulted in several technological applications, including fluorescent dyes, laser dyes, brightening agents, metal sensors, pH sensors, bio-imaging, organic photovoltaics (OPVs), organic light-emitting diodes (OLEDs), and many more. The photophysical properties of donor (D)-acceptor (A) based molecular systems depend on the substitution pattern and the D-A unit's nature, making them prime derivatives for application in organic photonics. The most frequent method for tuning the photophysical properties of organic compounds is to connect an electron-rich “D” and an electron-deficient “A” group directly or indirectly. The π-linkage between the “D” and “A” units results in a D-π-A type of conjugated molecular system, where the photophysical/electronic properties of D-π-A systems can be tuned by either (i) changing the “D” or “A” unit strength or (ii) varying the π-linker between the “D” and “A” units. A wide range of D-A conjugated systems with varying “D” and “A” units have been developed for various applications in chemistry, physics, materials science, and biology. Because of their superior photophysical characteristics, these are used to develop and create various sensory materials for monitoring biological events and detecting various target analytes. Chemosensors based on photoluminescence are essential among the many approaches and methodologies because they have multiple benefits, such as on-site detection, real-time monitoring with rapid response, innately high sensitivity, and simplicity of handling compared to other techniques. Considering the real benefit of the chromo-fluorogenic EDA system, present thesis explores its practical benefit for detection of various target analytes. A brief summary of each chapter of the present thesis are given below one by one. Chapter 1: This chapter begins with a brief discussion of the EDA system-based chemosensors and then moves to the general principle and working mechanism for designing chemosensors based on different photophysical processes with examples. This chapter deals with the objectives and applications of the present work in the present context of scientific development. Chapter 2: This chapter explores the reversible acidochromic behavior of a benzoxazole-based scaffold (BPP), which is highly sensitive to the acid-base in the liquid and gas phases. With the addition of acid, the solution of BPP changes its color from yellow to pink fuchsia due to the transformation of its imine into quinonoid form. The color change is completely reversible in the presence of the base, confirming the reversible acidochromic behavior of the present BPP system. Further, a paper strips-based test kit has been demonstrated for the practical utility of the present acidochromic BPP to identify a trace amount of acid-base in solution and gas-phase, respectively. The mechanistic aspects of detecting acid-base and colorimetric change in the presence of acid-base have been explored by density functional theoretical investigations and 1H NMR experiments. Moreover, we have constructed a reconfigurable dual-output combinatorial INH/IMP logic gate. Chapter 3: This chapter highlights the investigation of anion interactions and recognition abilities of naphthalene derivative, [(E)-1-(((4-nitrophenyl) imino) methyl) naphthalen-2-ol], (NIMO) by UV–visible spectroscopically and colorimetrically. NIMO shows selective recognition of F− ions colorimetrically, and the naked eye observes a visual color change from yellow to pink. The F− ions recognition is fully reversible in the presence of HSO4− ions. The limit of F− ions detection by NIMO could be possible down to 0.033 ppm-level. A paper strips-based test kit has been demonstrated to detect F− ions selectively by the naked eye, and a smartphone-based method for accurate sample analysis in the non-aqueous medium has also been demonstrated. The pKa value calculation and DFT analysis support spectroscopic behavior to find a correlation with receptor analyte interaction. The optical response of NIMO towards the accumulation of F− ions and, subsequently, HSO4− ions as chemical inputs provide an opportunity to construct INH and IMP molecular logic gates. Chapter 4: In this chapter, a fluorosensor derived from 4-aminophthalimide, ((E)-5-((2-hydroxy benzylidene) amino) isoindoline-1, 3-dione, HID working with excited state intramolecular proton transfer (ESIPT) mechanism is synthesized and employed for the selective recognition of aluminum (Al3+) ions and picric acid (PA) based on 'off-on-off' fluorescence mechanism. The sensor HID shows a turn-on fluorescence response towards Al3+ ions in H2O/DMSO (9:1, V/V) with a rapid response time (2 minutes) and exceptional sensitivity (LOD = 0.77 μM). The binding constant (K) of HID with Al3+ ions is estimated to be 1.32 × 108 M-2. The 1:2 stoichiometries of the complex between HID and Al3+ ions are confirmed through Job's plot and 1H NMR spectral analysis. Al3+ chelated HID complex is further employed to detect explosive nitroaromatic compounds, especially PA. Furthermore, using these two chemically encoded inputs, and corresponding optical output, we constructed the INH molecular logic gate with Al3+ and PA. The HID chemosensor and Al3+ chelated HID complex are also applied to map Al3+ ions and PA in the living cell. The HID chemosensor and Al3+ chelated HID complex's performance toward detecting Al3+ ions, and PA demonstrates that it might be used as a signaling tool for analyzing biological and environmental samples. Chapter 5: This chapter attempts to introduced a photoluminescence ionic liquid and its application for detecting nitro explosives. Due to the rising menace of illicit actions and pollution aroused by explosive nitroaromatic compounds (NACs), the growth of an adept sensor for detecting these NACs is essential. Herein, in this communication, a photoluminescent IL-assimilated group of uniform materials based on organic salt (GUMBOS) and Nano-GUMBOS has been fabricated by integrating pyrene butyrate with a quaternary phosphonium IL (PbIL) via a simple ion exchange process. Neat PbIL shows a bright cyan color photoluminescence under a 365 nm UV lamp irradiation and is employed as photoluminescence security ink and picric acid (PA) detection among the tested NACs. By simple reprecipitation method, we have developed water-suspended crystalline pyrene assimilated nanoparticles, nPbIL, characterized by various analytical techniques. The PbIL-derived water-suspended nanomaterials, nPbIL, display a robust cyan color excimer-like emission, which turns blue (monomeric) due to adding PA over the other related NACs. This ratiometric cyan-to-blue photoluminescence change is due to the displacement of the anionic pyrene moiety of the nPbIL by the picrate anion. The fabricated organo nanosensor is enormously discerning and responsive towards PA with a LOD of 0.77 nM and is superior to many available in the literature. Additionally, a fluorogenic paper strip-based test kit experiment has been demonstrated to detect and quantify PA selectively in aqueous solvents amongst the other tested NACs. The present contribution evokes a novel approach to developing different IL-based chemosensors for detecting and quantifying various target analytes. Chapter 6: This chapter attempts to demonstrate the role of different mimics of G-series nerve agents and their detection method. There is a pressing need for rapid and accurate recognition of hazardous G-series nerve agents in the solution and vapor phases to protect individuals from undesirable wars and terrorist attacks. However, achieving this goal in practice presents significant challenges. This contribution introduces a specific and selective acridine-based fluorogenic sensor, AMA, which exhibits turn-on behavior from cyan to blue photoluminescence under the exposure of a 365 nm UV lamp in response to diethylchlorophosphate (DCP), a mimic of sarin gas, in both liquid and vapor phases, respectively. The mechanism underlying the identification of DCP using AMA has been elucidated through 1H-NMR titration investigation and HRMS analaysis. The fluorgenic, DCP-specific AMA shows an outstanding selectivity, excellent sensitivity, and a broad linear span of 15-38 μM, with an identification limit of 7.9 nM, which is found to be superb than many chemosensors available in the literature without any interference. To facilitate its potential practical applications, we have introduced an AMA-coated test kit utilizing Whatman-41 filter paper, which can be used as a handy and visual photonic device for on-spot identification of DCP as a mimic for sarin gas under the colonial crowding condition of other analogous analytes. Furthermore, we have demonstrated a fluorogenic dip-stick method to detect and quantify the DCP vapor under the exposure of a 365 nm UV lamp. Chapter VII: Finally, a brief summary of the present thesis and the future perspective from the present research work has been delineated in this chapter.
Open Access
Metal free C- H Functionalization: a unique tool for library synthesis of functionalized 4- pyrimidiones
(University of North Bengal, 2023) Roy, Sanjay; Das, Sajal
The Present Thesis entitled as “Metal free C- H Functionalization: a unique tool for library synthesis of functionalized 4-pyrimidiones” has made some efforts to synthesize the diverse 4 pyrimidones with varied functional groups via different approaches and their applications in medicinal and pharmacological domains. Based on different direction and contents of the work; the thesis has been divided into four chapters. Chapter I: describes an introduction to present work, the “A brief review on C-H functionalization/activation and a literature study regarding the synthesis of 4Hpyrido[ 1,2-a]pyrimidin-4-one derivatives” Summarizes a brief review on pyrimidines and it was further subdivided into following points: 1) Origin, background theory, importance and current status of C-H Functionalization. 2) Use of C-H functionalization techniques in selective functionalization of heterocycles. 3) Importance of 4-pyrimidiones and current literature status 4) Different approaches of its synthesis and further derivatization Chapter II: describes “Microwave-assisted straight forward synthesis of 2-substituted alicyclic fused pyrimidone” We have divulged here a metal free- and MW assisted route to tetrahydro-4H-pyrido[1,2- a]pyrimidin-4-one and dihydropyrrolo[1,2-a]pyrimidin-4(6H)-one has been demonstrated by the reaction of aminoacrylates with lactams in presence of phosphorous pentachloride. This transformation comprises of the sequential formation of three new bonds to produce pyrimidone derivatives under mild reaction conditions and this strategy is well compatible for both electron deficient and electron rich amino-acrylates. This method is amenable for gram scale reaction.
Open Access
Assorted interactions of some antibacterial and anticancer drug molecules and ionic liquids prevaling in supramolecular and solution chemistry investigated by experimental and computational apporach
(University of North Bengal, 2023) Sharma, Antara; Roy, Mahendra Nath
Proposed work covers the Supramolecular Host-Guest Inclusion Complexation of some bioactive molecules and the solute-solvent interaction of amino acids (AA) with ionic liquids (ILs) aiming to compare the molecular interaction existing among these different chemical compounds and resulting molecular synergism in solution phase. Supramolecular assemblage has garnered a huge importance during recent years in the field of drug delivery owing to their significant biocompatibility and excellent potential to expand the spectrum of medical application in pharmaceutical industries and biomedical sciences. The spectroscopic techniques confirm the inclusion complex formation of numerous bioactive molecules and their photophysical properties in solution phase. The UV-Visible, 1H NMR and FT-IR spectroscopy along with mass spectrometry studies supports the formation of inclusion complex. Further, SEM and PXRD analysis implements the qualitative aspect for the generation of supramolecular framework. Thermal and photostability of such assembly have been examined through DSC and UV- visible studies. Computational and theoretical molecular modelling studies of this system reaffirms the results observed in the experimental studies. In this study, inclusion of variety of biologically potent molecules such as, Rodanine, Gemcitabine and Nitrofurantoin have been examined. These compounds find significant medicinal applications. Pharmacological aspect is specifically considered to illustrate the biocompatibility of such biologically active molecules. Molecular recognition, controlled release of a drug and sensing field have received the great consideration under host–guest chemistry. Encapsulation of guest molecules in aqueous phase inside the nanocage of host molecules, such as cyclodextrins and several other water-soluble hosts lights up an advanced technique into the field of molecular recognition (inclusion or complexation) owing to extensive non-covalent interactions. The potent pharmacological activity of bioactive compounds often gets influenced through molecular recognition. Supramolecular host-guest chemistry covers a broad aspect related to the inclusion complex formation between the host and the guest molecules. Hydrophobic nanocage of host molecules are very efficient in binding variety of guest molecules. Over the past few decades, the supramolecular assembly has been extensively investigated in several fields including analytical chemistry and drug-delivery. Cyclodextrins (CDs), are the most suitable host compounds owing to their ability for controlled passage of guest molecules after inclusion complex formation thereby increasing bioavailability of the compound. Ionic liquids (IL) or famously known as molten salts at room temperature currently received great consideration in many areas of chemistry by the researchers across the globe. The most significant characteristic of ILs is the “tunability” of various physical and chemical properties by modifying structure. Many reviews have highlighted the different characteristics of ILs and their potential application. ILs are blessed with some exceptional properties as most of them have a negligible vapor pressure, unparalleled thermal and electrochemical stability, low flammability and commending dissolution properties with large variety of organic/inorganic compounds. ILs mainly consist of different category of cations and anions. They found significant applications as biphasic systems for separation, solvents for many synthetic and catalytic applications, lubricants, extensively in lithium batteries, supercapacitors, actuators, substitute for conventional solvents, alternative for reaction media and active pharmaceutical ingredients. However, the most important characteristic associated with ILs is the “tunability” of their structure. They can easily modify their structure to achieve the specific chemical or electrochemical applications. In order to investigate the stability of proteins, (ILs) are generally employed as a novel medium . Amino acids are considered ideal system for investigating the characteristics of proteins. Further denaturation, solvation and dissociation of enzyme are highly affected by the neighbouring environment. The emergence of assorted interactions is conventionally examined by estimation of the apparent molar volume ( v  ), limiting apparent molar volume ( 0 v  ), molar refraction ( M R ), limiting molar refraction ( 0 M R ) viscosity B coefficients obtained from different physicochemical methodologies. This study features the variety of physicochemical characteristics of amino acid in solution of Ionic liquid in water. This work helps in interpretating the behaviour of these compounds in complex structures of proteins. Here we have selected an Ionic liquid as an additive (electrolyte) as they are blessed with various advantages as a function of concentration, temperature, and ambient pressure. Thermodynamic, viscometry, volumetric, refractometric, surface tension measurements have been carried out as these properties are susceptible towards the solute-solute and solute-solvent interaction. Investigation of these properties greatly support to understand the structure and characteristics of solutes in aqueous medium and gives a reliable explanation for the complicated nature of molecular interactions in various biochemical processes occurring in the human body. Therefore, the objective of this thesis is to (1) investigate and understand the significance of supramolecular recognition owing to their diverse range of applications in varied fields such as pharmaceutical, biomedical sciences etc. (2) understand and evaluate the molecular interactions between ionic liquid and various biomolecules in order to manifest the behaviour of these compounds in complex structures of proteins for further application. Summary of work done Chapter I This chapter contains the details of the research work, their objective, scope and applications in the modern science. A detailed discussion about the scope of selecting the biologically active molecules, cyclodextrins, amino acids and ionic liquids have been included. This chapter consist a brief list of all the techniques of investigations i in the research work. Chapter II This chapter consist the review of the previous works reported by scientists and researchers in the field of supramolecular and solution chemistry around the world. This chapter also includes the detail of theories of investigation. The interactive forces existing among the various molecules have been discussed in detail. The underlying theories of investigating techniques, i.e., theory of 1H NMR , FT-IR, Fluorescence, UV-Visible spectroscopy, Mass spectrometry and Thermogravimetric analysis, Powder X-ray Diffraction, Scanning Electron Microscopy, Surface tension study, Molecular docking study, Antibacterial activity study, Cytotoxicity study, CT-DNA interaction study, Photostability study, Surface tension, Conductivity, Density, Viscosity, Refractive index studies have been discussed thoroughly and the importance of this research work also included in this thesis. Chapter III This chapter presents the experimental section. It includes the details of name, structure, physical properties and applications of the biologically active molecules, cyclodextrins, amino acids, ionic liquids and solvents used in the research work. It consists the briefing about the experimental methodologies. Chapter IV This chapter contains of the encapsulation of rhodanine within the cavity of α-cyclodextrin and β- cyclodextrin. This work has been investigated by spectroscopic, physicochemical methods. Job plots using UV-Visible spectroscopy confirms the 1:1 stoichiometry of the host-guest molecular assembly. This observation was again supported by mass spectrometric analysis. UV-Visible spectroscopy has been employed to calculate association constants for the inclusion complexes using Benesi– Hildebrand method. Thermodynamic parameters have been calculated and it ascertains the thermodynamically spontaneity of the overall inclusion processes. 1H NMR and FT-IR investigations illustrates the quantitative insight on the possible mode of encapsulation in inclusion complexes. Thermal stability of rhodanine on inclusion with cyclodextrins has been evaluated by DSC analysis. Computational study further provides the useful understanding on the inclusion mode of rhodanine molecule into the nanocage of cyclodextrins. The surface morphology of the inclusion complexes was investigated by SEM. Photostability and CT-DNA interaction studies are investigated by UV Visible spectroscopy. Finally, the biological activity namely; cytotoxicity and antimicrobial activity of the inclusion complexes were evaluated and a comparative study was carried out with respect to pure rhodanine. Chapter V This chapter presents the study of the host-guest inclusion complex of gemcitabine with β-cyclodextrin, photostability, CT-DNA study and its biological activity. The prepared complex was characterized by numerous physicochemical and spectroscopic methods. Job plot, and mass spectrometric analysis confirms the 1:1 ratio host-guest inclusion complex. Association constant has been determined by Benesi–Hildebrand method. The Gibb’s free energy of binding has been calculated by evaluating the binding constant which confirms the inclusion process is spontaneous. The mode of inclusion was investigated by 1H NMR and FT-IR spectroscopic analysis. PXRD and SEM analysis have been carried to reaffirm the inclusion complex formation. The enhancement in the photo stability of gemcitabine through complexation was investigated by UV-visible spectroscopic analysis. Molecular docking study presented the most preferred site for binding of gemcitabine molecule within the cavity of β-cyclodextrin. The apoptosis and antibacterial activity of the inclusion complex was investigated in detail and subsequently compared with free gemcitabine. Chapter VI This chapter presents the thorough analysis on the diverse molecular interactions of implausible amino acid, L-leucine (AA) in the aqueous solution of Benzyltriethylammoniun chloride (BTEACl), Benzyltributylammoniun chloride (BTBACl) have been carried out by numerous physicochemical techniques such as Density, Refractive index, Viscosity, Electrical conductivity, at four different temperatures ranging from 298.15 K to 318.15 K. 1HNMR and UV-visible analysis were carried out to investigate the solute- solvent interaction. Association constant for L-Leucine-BTBACl system as well as for L-Leucine-BTEACl system were evaluated to understand the diverse intermolecular interactions in the solution phase using UV-vis spectroscopy. Formation of thermodynamic background owing to different interactions occurring in the ternary mixtures were studied by evaluating the free energies of numerous molecular interactions. The source of various interactions is evaluated by calculating the apparent molar volume (ϕV), limiting apparent molar volume (ϕV0), viscosity Bcoefficients, molar refraction (RM), limiting molar refraction (RM0), molar conductivity (Λ) and surface tension (σ)volume, molar refraction, limiting molar refraction, viscosity B coefficients. Furthermore, adsorption energy, molecular electrostatic potential (MESP) maps and reduced density gradient (RDG) obtained by the application of density functional theory (DFT), have been used to determine the type of interactions which are consistent with the experimental observations. Chapter VII This chapter provides the detail analysis and application of supramolecular complexations of a very important antibiotic and a potential acetylcholine esterase inhibitor nitrofurantoin with α and β-cyclodextrins in aqueous medium. The molecular interactions have been investigated using 1HNMR spectroscopic studies, Job plot confirms the 1:1 stoichiometry of host with guest in the inclusion complexes. Binding constants for the formation of inclusion complexes have been determined using Benesi–Hildebrand method with the help of UV-visible spectroscopy. Free energy of binding of nitrofurantoin with cyclodextrins have been calculated from the binding constant value. This information subsequently determines the thermodynamic feasibility of the encapsulation process. PXRD and SEM studies further supports the inclusion complexes formation. Photo stability, CTDNA interaction studies of the inclusion complexes was carried out using UV-visible spectroscopy. Molecular docking study indicates the most preferable binding orientation of nitrofurantoin within the cavity of cyclodextrins. Chapter VIII This chapter contains the concluding remarks related the research works carried out in this thesis.
Open Access
Polydentate ligand based metal complexes for oxidase activity
(University of North Bengal, 2023) Sahin Reja; Das, Rajesh Kumar
Polydentate ligands have been widely studied due to their ability to form stable and efficient metal complexes. In recent years, there has been growing interest in the use of these metal complexes as catalysts for various chemical reactions, including oxidase activity. Oxidases are enzymes that play a crucial role in biological processes such as cellular respiration and metabolism. The development of synthetic metal complexes with oxidase-like activity has the potential to provide alternative catalysts for these important processes. In this abstract, we discuss the design and synthesis of polydentate ligand based metal complexes for oxidase activity. We focus on the use of N, O-chelating ligands that have been shown to form stable and efficient metal complexes. The metal complexes are characterized using various spectroscopic techniques, and their oxidase activity is evaluated using a variety of assays. We also explore the mechanistic aspects of the oxidase activity of these metal complexes and compare their activity to that of natural oxidase enzymes. Overall, the results demonstrate the potential of polydentate ligand based metal complexes as efficient catalysts for oxidase activity. These complexes may provide a viable alternative to natural oxidase enzymes, and their development could lead to the development of new therapeutic agents and industrial catalysts. Polydentate ligands are molecules that possess multiple donor atoms capable of bonding with a central metal ion. Metal complexes of polydentate ligands have gained significant interest in recent years for their potential applications in various fields, including catalysis, drug design, and biotechnology. In particular, metal complexes of polydentate ligands have been shown to exhibit exceptional oxidase activity, making them an attractive candidate for various oxidation-based reactions. Oxidation is an essential process in biological systems, and the use of metal complexes of polydentate ligands in catalyzing oxidation reactions is a promising area of research. The oxidase activity of these metal complexes can be attributed to the presence of redox-active metal centers, which can donate or accept electrons during the oxidation process. The polydentate ligands stabilize the metal ion and enhance its reactivity, resulting in increased catalytic activity. The catalytic activity of polydentate ligand-based metal complexes for oxidase activity is dependent on several factors, including the types of metal ion, the coordination environment, and the ligand structure. The choice of metal ion plays a significant role in determining the catalytic activity of the complex. Transition metals such as copper, iron, and manganese have been extensively studied for their oxidase activity. These metals possess a variable oxidation state, allowing them to undergo redox reactions during the oxidation process. The coordination environment of the metal ion is another critical factor in determining the oxidase activity of the metal complex. The coordination environment influences the electron transfer properties of the metal ion, which in turn affects the catalytic activity of the complex. Ligands that provide a favorable coordination environment, such as chelating ligands, can enhance the catalytic activity of the complex. The structure of the polydentate ligand also plays a crucial role in determining the catalytic activity of the metal complex. The ligand structure can influence the binding affinity of the ligand for the metal ion, as well as the redox properties of the metal ion. Ligands with multiple donor atoms, such as bidentate and tridentate ligands, have been shown to exhibit excellent catalytic activity due to their ability to stabilize the metal ion. Polydentate ligand-based metal complexes have been shown to exhibit oxidase activity in various reactions, including the oxidation of alcohols, amines, and sulfides. These complexes can also catalyze the oxidation of organic compounds under mild conditions, making them attractive for industrial applications. The use of polydentate ligand-based metal complexes in the oxidation of biomolecules, such as DNA and proteins, is an exciting area of research that holds promise for various biotechnological applications. In conclusion, polydentate ligand-based metal complexes have shown exceptional oxidase activity, making them a promising candidate for various oxidation-based reactions. The catalytic activity of these complexes is dependent on several factors, including the choice of metal ion, the coordination environment, and the ligand structure. The use of these complexes in industrial applications and biotechnology holds significant promise and is an exciting area of research for the future. CHAPTER I Chapter I is an introductory one that describes polydentate ligand based metal complexes as efficient catalysts for oxidase activity and their applications in various fields as well as single crystals, their classification and methods of growth. Object and application of the present research work has also been outlined in this chapter. A brief description of the advantages of different type of technique of crystal growth was described. CHAPTER II Chapter II involves the experimental section briefly describing the chemicals and materials used in completing this research. This chapter also describes the novelty behind choice of organic linkers/ligands used in the works embodied in this thesis. This chapter also contains details of the physico-chemical and spectroscopic techniques, viz., single crystal, FTIR spectroscopy, NMR, and EPR, etc., used for the physicochemical characterization of the synthesized complexes. This chapter also describes the theoretical characterization (DFT, etc) of the hybrid complexes. CHAPTER III 2-(3-(Dimethylamino)propyl)isoindoline-1,3-dione (DAPID) has been synthesized and utilized to produce 3-(1,3-dioxoisoindolin-2-yl)-N,N-dimethyl propan-1-aminium perchlorate (DIDAP). Both DAPID and DIDAP were characterized using different spectroscopic techniques. Structure of the DIDAP has been determined using single crystal X-ray diffraction technique. DIDAP found to self assemble in a helical motif in its supramolecular structure with the aid of different hydrogen bonding, Cg···Cg and short interatomic contacts in the solid state. The compound DIDAP exhibited anticancer activity against the human hepatomas cell line (Hep G2) and the activity was further complemented by performing docking study. In addition, the computational studies have also been performed to examine the chemical reactivity of the compound. Shape index and Curvedness surfaces indicated -stacking with different features in opposed sides of the molecule. Fingerprint plot showed C···C contacts with similar contributions to the crystal packing in comparison with those associated to hydrogen bonds. Enrichment ratios for H···H, O···H and C···C contacts revealed a high propensity to form in the crystal. CHAPTER IV N1, N4- Bis(3-(dimethylamino)propyl)succinamide (DAPS) has been synthesized and utilized to produce 3,3'-[succinylbis(diazaneyl)]bis(N,N,N-trimethylpropan-1-ammonium) perchlorate (SAPAP). Both DAPS and SAPAP were characterized using different spectroscopic techniques. Structure of the SAPAP has been determined using single crystal X-ray diffraction technique. The compound SAPAP had excellent anticancer activity against the human colon carcinoma cell line (HT-29), proposing them as a suitable candidate for future anticancer therapies. Docking, Molecular dynamics simulation, pharmacokinetic predictions and ELISA were also employed to evaluate the inhibitory action of the synthesized compound against the said cancer cell line HT-29. CHAPTER V Keeping in mind the importance of oxidase activity it includes a versatile bioinspired metallocatalyst [Cu2L2(OAc)4] (L = 2-(3-(dimethylamino)propyl)isoindoline-1,3-dione), which has been synthesized and characterized as reported. To the best of our knowledge, a very few articles of paddlewheel type complexes have reported behave as catechol oxidase activity and phenoxazinone synthase activity. The EPR, CV, and ESI Mass analyses collectively support that the complex exhibits such activity via oxygen dependant enzymatic radical pathway. Furthermore, these activities are observed under fully aerobic conditions in which 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-amino phenol (2-AP) are used as model substrates. Michaelis-Menten analysis derived from the pseudo first-order reaction kinetics established that this complex shows prominent catalytic activity towards 3,5- DTBC and 2-AP (Kcat 12.0726×103 h-1 and 6.6654×103 h-1). Molecular electrostatic potential (MEP) diagrams and density functional theory (DFT) reveals the charge density region within the complex while growth inhibition (GI50) and molecular docking study exposes substantial dose dependent anti-leukemic activity against Hep-G2 cell line. Moreover, promising anti-bacterial property was also detected on multi-drug resistant E. coli and B. cereus bacteria. CHAPTER VI In this chapter a promising bioinspired metallocatalyst [Cu(L1)2(L2)] (L1 = P-hydroxybenzoic acid, L2= N1,N1-dimethylpropane-1,3-diamine) has been produced and characterized in accordance with reports.. In the octahedron arrangement around the copper ion, the elongation along one axial direction and one equatorial direction results in a distorted geometry. Molecular assembly shows both inter and intra molecular H-bonding along with C-H---π interactions evident from the Hirshfeld surface analysis. The fingerprint plot discloses the relative contribution of percentage of intermolecular contacts (H⋯H, C⋯H and O⋯H) in the complex. To the best of our knowledge, no one has reported catechol oxidase activity and phenoxazinone synthase activity of Cu(II) complexes with P-hydroxy benzoic acid and propyl amine ligands so far. The EPR, CV, and UV analyses collectively support that the complex exhibits such activity via oxygen dependant enzymatic radical pathway. Furthermore, these activities are observed under fully aerobic conditions in which 3,5-di-tert-butylcatechol (3,5-DTBC) and 2-amino phenol (2-AP) are used as model substrates. Michaelis-Menten analysis derived from the pseudo first-order reaction kinetics established that this complex shows extremely high catalytic activity towards 3,5- DTBC and 2-AP (Kcat 1.729×105 h-1 and 0.260×105 h-1). The suggested mechanism has been supported by UV spectra data in which formation of hydrogen peroxide by observing the appearance of spectral band at λmax 353 nm indicates the active participation of molecular oxygen in the catalytic process. CHAPTER VII Future research in the field of polydentate ligand-based metal complexes with a focus on enhancing oxidase activity holds significant promise. These studies may lead to the development of novel ligands, versatile multifunctional complexes, and applications spanning biotechnology, medicine, energy conversion, and industrial processes, offering innovative solutions with broad-reaching implications for various fields.
Open Access
Investigation in solution properties of bio-active solutes and mineral salts prevailing in some aqueous and non-aqueous solvent system
(University of North Bengal, 2012) Roy, Pran Kumar; Roy, Mahendra Nath
Thermo-physical and bulk properties of solutions are very useful to obtain information on the intermolecular interactions and geometrical effects in the systems. Moreover, knowledge of the thermodynamic properties is essential for the proper design of industrial processes. Accurate knowledge of thermodynamic properties of solution mixtures has great relevance in theoretical and applied areas of research. The branch of physical chemistry that studies the change in properties that arise when one substance dissolves in another substance is termed as solution chemistry. It investigates the solubility of substances and how it is affected by the chemical nature of both the solute and the solvent. The mixing of different solute or solvent with another solvent/solvent mixtures gives rise to solutions that generally do not behave ideally. This deviation from ideality is expressed in terms of many thermodynamic parameters, by excess properties in case of liquid-liquid mixtures and apparent molar properties in case of solid-liquid mixtures. These thermodynamic properties of solvent mixtures corresponds to the difference between the actual property and the property if the system behves ideally and thus are useful in the study of molecular interactions and arraangements. In particular, they reflect the interaction that take place between solute-solute, solute-solvent and solvent-solvent species.However, the exact structure of the solvent molecule is not known with certainity. The addition of an ion or solute modifies the solvent structure to an extent whereas the solute molecules are also modified. The extent of ion-salvation is dependent upon the interactions taking place between solute-solute, solute-solvent, solvent-solvent species. The assesment of ion-pairing in these systems is important because of its effect on the ionic mobility and hence on the ionic conductivity of the ions in solution. These phenomenon thus paves the path for research in solution chemistry to elucidate the nature of interaction through experimental studies involving densitometry, viscometry, interferrometry, refractometry and other suitable methods and to interpret the experimental data collected. Caffeine, nicotinamide, resorsinol, glycine, catechol, oxalic acid, tetrabutyl ammonium iodide, tetra pentyl ammonium iodide, tetra hexyl ammonium iodide, tetra heptyl ammonium iodide, N-Cetyl-N,N,N-trimethyl ammonium bromide, DGlucose, D-Mannitol, D-Sucrose, thorium nitrate, sodium molibdate, phosphomolibdic acid, lithim nitrate, potassium nitrate, sodium nitrate, silver sulphate which are considered as solutes, have been chosen in this research work. Nitrobenzene, carbon tetrachloride, 2-Methoxy ethanol, along with water also considered as solvents. These solutes and solvents have wide application in chemical fields and various industries like pharmaceuticals, cosmetics, battery technology, agricultural products etc. In this research work more emphasis have been given to Bio active compounds ("plant bioactives" or "bioactive compounds") they are mainly inherent non-nutrient constituents of food plants and edible mushrooms with anticipated health promoting and toxic effects when ingested. Bioactive compounds derived from plant foods, are of growing interest to the scientific community and food industry because of their putative health-promoting properties. Increasing evidences report beneficial effects of bioactive compounds, particularly against cancers, cardiovascular diseases and diabetes. They may also serve as adjusting factors in human body due to their physiological activity. Most bioactive compounds of natural origin are secondary metabolites, i.e., species-specific chemical agents. Information about food sources, concentrations and intakes of bioactive compounds, as well knowledge of their absorption, metabolism and biological effects, is needed in order to evaluate their potential health benefits. Pharmacological activity is usually taken to describe beneficial effects of bioactive compounds. There is sufficient evidence to recommend consuming food sources rich in bioactive compounds. From a practical perspective, this translates to recommending a diet rich in a variety of fruits, vegetables, whole grains, legumes, oils, and nuts. In the body under physiological conditions, many vital functions are regulated by pulsed or transient release of bioactive substances at a specific time and site. Thus, to mimic the function of living systems, it is important to develop new drug delivery devices to achieve pulsed delivery of a certain amount of a bioactive compound at predetermined time intervals. The ability to deliver bioactive compounds and/ or therapeutic agents to a patient in a palatine or staggered release profile has been a major goal in drug delivery research over the last two decades. Rice bran has been recognized as an excellence source of bioactive compounds, but only a small amount is consumed by humans. The limitation of using rice bran in a food industry is its rough texture and low concentration of bioactive compounds, when incorporated into food products. Various methods have been developed to enhance the level of bioactive components in food materials, including thermal, alkali, acid and chemical treatments. Many bioactive compounds have been discovered. These compounds vary widely in chemical structure and function and are grouped accordingly. Phenolic compounds, including their subcategory, flavonoids, are present in all plants and have been studied extensively in cereals, legumes, nuts, olive oil, vegetables, fruits, tea, and red wine. Many phenolic compounds have antioxidant properties, and some studies have demonstrated favorable effects on thrombosis and tumorogenesis and promotion. One of many phenolics in olives and olive oil is a potent antioxidant. Resveratrol, found in nuts and red wine, has antioxidant, antithrombotic, and anti-inflammatory properties, and inhibits carcinogenesis. Lycopene, a potent antioxidant carotenoid in tomatoes and other fruits, is thought to protect against prostate and other cancers, and inhibits tumor cell growth in animals. Catechol is used mainly as a precursor to pesticides, flavors and fragrances. It is also consumed in the production of pesticides, the remainder being used as a precursor to fine chemicals such as perfumes and pharmaceuticals. Mannitol is used clinically to reduce acutely raised intracranial pressure until more definitive treatment can be applied, e.g., after head trauma. It is also used to treat patients with oliguric renal failure.Glucose circulates in the blood, providing energy to organs, glands, muscles, indeed to every cell Glucose is used in oxidation. More complex sugars have to be changed to glucose first before they can be broken down to release energy in respiration Glucose is a ubiquitous fuel in biology. Caffeine is an alkaloid of methylxanthine family, its main pharmacological properties are a stimulant action on the central nervous system .it also acts as a natural pesticide since it paralyses and kills some of the insects. Organosulfur compounds in garlic and onions, isothiocyanates in cruciferous vegetables, and monoterpenes in citrus fruits, cherries, and herbs have anticarcinogenic actions in experimental models, as well as cardioprotective effects. Sodium Molybdate is used in industry for corrosion inhibition, as it is a nonoxidizing anodic inhibitor. The addition of sodium molybdate significantly reduces the nitrite requirement of fluids inhibited with nitrite-amine, and improves the corrosion protection of carboxylate salt fluids. Phosphomolybdic acid is widely used to stain connective tissues by dyes. It has been found polyvalent phosphomolybdic acid appears to form a bridge between the basic group of the substrate and the basic group of the dye. Oxalic acid and oxalates are useful as reducing agents for photography, bleaching, and rust removal. They are widely used as a purifying agent in pharmaceutical industry, precipitating agent in rare-earth metal processing, bleaching agent in textile and wood industry, rust-remover for metal treatment, grinding agent, waste water treatment. It is used as acid rinse in laundries and removing scale from automobile radiators. Nicotinamide is commonly known as vitamin B. It plays a very important role to maintain the normal function of the digestive systems and cholesterol levels in the human body. The combination of nicotinic acid and nicotinamide is clinically referred to as niacin. Glycine serves as a buffering agent in antacids, analgesics, antiperspirants, cosmetics, and toiletries. Glycine is an intermediate in the synthesis of a variety of chemical products. In summary numerous bioactive compounds appear to have beneficial health effects. I Much scientific research needs to be conducted before we can begin to make science-based dietary recommendations. On the other hand minerals are naturally-occurring elements needed by the body and its vital activities. Each mineral, with its own specific task, even in the small and often minute quantities necessary, is indispensable for important life functions; they are needed for the formation of hormones, enzymes and other body substances. They're generally found in foods in the form of chemical compounds called salts and in water in the form of ion.soluble. Animals need more than salt for proper health and nutrition. Animals need trace mineral supplements. They are needed in very small amounts, or traces, in the diet, and hence their name, "trace minerals. Mineral salts do not usually contain the element carbon and are therefore inorganic (organic compounds always contain carbon).Plant roots absorb individual mineral ions from soil water. Some of the ions travel by diffusion into the root; others are absorbed by active transport. The minerals required in the greatest amounts are those containing the element nitrogen, for example nitrate ions ( or 'nitrates'), which are a key component of inorganic fertilizer. A plant uses nitrates in the production of proteins such as enzymes, so they are important for plant growth. They are often in short supply in the soil, which is why inorganic fertilizers are required. Plants also require magnesium in order to make chlorophyll, the green chemical that absorbs the ei:iergy of sunlight for photosynthesis. Sodium nitrate is used as an ingredient in fertilizers, pyrotechnics, as an ingredient in smoke bombs, as a food preservative, and as a solid rocket propellant, as well as in glass and pottery enamels. Potassium nitrate is a strong oxidizer which burns and explodes with organics. It is used in the manufacture of gunpowder. It is also used in explosives, fireworks, matches, and fertilizers, and as a preservative in foods especially meats. It is sometimes used in medicine as a diuretic. Lithium nitrate is used as an electrolyte for high temperature batteries. It is also used for long life batteries as required, for example, by artificial pacemakers. The solid is used as a phosphor for neutron detection.Quaternary ammonium compounds compounds are used as, Surface-active agents , Solvents , Intermediates, Active Ingredient for Conditioners, Antistatic Agent, Detergent Sanitisers, Softner for textiles and paper products, Phase Transfer Catalyst, Antimicrobials, Disinfection Agents And Sanitizers, Slimicidal Agents, Algaecide, Emulsifying Agents, Pigment Dispersers. The study of these solvents and solutes, in general, are of interest because of their wide use in many industries with interests ranging from pharmaceutical to cosmetic products. Summary of the Works Done CHAPTERI This chapter contains the object and applications of the research work, the solvents and solutes used and methods of investigations. This also involves the summary of the works done associated with the thesis. CHAPTER-II This chapter contains the general introduction of the thesis and forms the background of the present work. A brief review of notable works in the field of ionsolvent interaction has been given. The discussion includes solute-solvent, solutesolute and solvent-solvent interactions of mixed solvent systems and of electrolytes in pure, aqueous, non-aqueous solvent systems at various temperatures in terms of various derived parameters of conductance, density, viscosity, ultrasonic speed, and refractive index. Critical evaluations of different methods on the relative merits and demerits on the basis of various assumptions employed from time to time of obtaining the single ion values and their implications have been made. The molecular interactions are interpreted based on various equations. l., CHAPTER-III This chapter contains the experimental section which mainly involves the structure, source, purification and application of the solvents and solutes used and the details of the experimental methods employed for measurement of the thermodynamic, transport, acoustic and optical properties. CHAPTER-IV This chapter quantifies the Precise measurements on electrical conductances of tetraalkylammonium iodides, R4NI (R = butyl to heptyl) in different mass% (20- 80) of carbon tetrachloride + nitrobenzene at 298.15 K have been performed. Limiting molar conductances ( A0 ), association constants (KA) and co-sphere diameter ( R) for ion-pair formation in the mixed solvent mixtures have been evaluated using the Lee-Wheaton conductivity equation. However, the deviation of the conductometric curves ( A versus ✓c ) from linearity for the electrolytes in 80 mass% of carbon tetrachloride + nitrobenzene indicated triple ion formation and therefore corresponding conductance data have been analyzed by the Fuoss- Kraus theory of triple ions. Limiting ionic molar conductances (A~) have been calculated by the reference electrolyte method along with a numerical evaluation of ion-pair and triple-ion formation constants ( KP ~ KA and Kr); the results have been discussed in terms of solvent properties, configurational theory and molecular scale model. CHAPTER-V In this chapter, Partial molar volumes ( (l) and viscosity B-coefficients for nicotinamide in (0.00, 0.05, 0.10, 0.15, and 0.20) mol.dm-3 aqueous resorcinol solutions have been determined from solution density and viscosity measurements at (298.15, 308.15, and 318.15) Kasa function of the concentration of nicotinamide (NA). Here the relation ¢i = a0 + a1T + a2T2 , has been used to describe the temperature dependence of the partial molar volume ( ¢i) .These results and the results obtained in pure water were used to calculate the standard volumes of transfer ( t1¢i) and viscosity B-coefficients of transfer for nicotinamide from water to aqueous resorcinol solutions to study various interactions in the ternary solutions. The partial molar volume ( ¢S) and experimental slopes obtained from the Masson equation have been interpreted in terms of solute-solvent and solutesolute interactions, respectively. The viscosity data have been analyzed using the Jones-Dole equation, and the derived parameters Band A have also been interpreted in terms of solute-solvent and solute-solute interactions, respectively in the ternary solutions. The structure making or breaking ability of nicotinamide has been discussed in terms of the sign of (c>2¢i I 8T 2 ) p. The activation parameters of viscous flow for the ternary solutions studied were also calculated and explained by the application of transition state theory. CHAPTER-VI Proteins are complex molecules and their behavior in solutions is governed by a combination of many specific interactions. One approach that reduces the degree of complexity and requires less complex measurement techniques is to study the interactions in systems containing smaller biomolecules, such as amino acids and peptides. Some studies have revealed that the presence of an electrolyte drastically affects the behaviors of amino acids in solutions and this fact can be used for their separation and purification. Therefore, in this chapter an attempt has been made to unravel the various interactions prevailing in a amino acid, Glycine in aqueous silver sulphate solutions by volumetric, viscometric study at 298.15, 308.15, 318.15 K. CHAPTER-VII In this chapter Apparent molar volume ( r/Jv) and viscosity B-coefficients were measured for phosphomolybdic acid in aqueous solution of catechol from solution density [p) and viscosity [TJ) at 298.15, 308.15 and 318.lSK at various solute concentrations. The experimental density data were evaluated by Masson equation and the derived data were interpreted in terms of ion-solvent and ion-ion interactions. The viscosity data have been analyzed using Jones -Dole equation and the derived parameters, B and A, have been interpreted in terms of ion-solvent and ion-ion interactions respectively. The structure-making or breaking capacity of the solute under investigation has been discussed in terms of sign of(f/¢i I 8T 2 ) p. The activation parameters of viscous flow were determined and discussed by application of transition state theory. CHAPTER-VIII This chapter presents a study of densities, viscosities and sound speeds have been determined for sodium molybdate in various mole-fractions of aqueous oxalic acid solutions. From the experimental data, apparent molar volume ( ¢v) and viscosity B-coefficients were calculated at 303.15, 313.15 and 323.lSK using Masson equation and Jones - Dole equation respectively. Adiabatic compressibility of different solutions has been determined from measurement of ultrasonic speeds of sound at 303.lSK. Partial molar volumes ( r/Ji) and viscosity B-coefficients (LlB) of transfer from water to aqueous oxalic acid mixtures have been calculated and discussed. The structure-making or breaking capacity of the solute under investigation has been discussed in terms of sign of ( 8 2 r/Ji I 8 T 2 ),, • The activation parameters of viscous flow were determined and discussed by application of transition state theory. CHAPTER-IX This chapter presents a study of Apparent molar volumes ( ¢i) and viscosity B-coefficients for mineral salts in aqueous binary mixture of 2-methoxy ethanol have been estimated from solution density and viscosity measurements at 298.15 K and at various electrolyte concentrations as a function of the concentration of mineral salts. Experimental density data were analyzed using the Masson equation and the derived parameters interpreted in terms of ion-solvent and ion-ion interactions. The viscosity data have been analyzed using the Jones-Dole equation, and the derived parameters B and A have also been interpreted in terms of solutesolvent and solute-solute interactions. CHAPTER-X In this chapter, Apparent molar volumes ( ¢v) and viscosity B-coefficients for some carbohydrates (D-Glucose, D-Mannitol and D-Sucrose) in 0.05%, 0.10%, 0.15%, aqueous cetrimmonium bromide (N-Cetyl-N,N,N-trimethyl ammonium bromide) (C19H42BrN) solutions have been determined from solution density (p) and viscosity (11) measurements at 298.15, 308.15, and 318.15 Kasa function of the concentration of carbohydrates. The standard partial molar volume ( ¢,~) and experimental slopes ( s:) obtained from the Masson equation have been interpreted in terms of solute-solvent and solute-solute interactions, respectively. The viscosity data were analyzed using the Jones-Dole equation, and the derived parameters A and B have also been interpreted in terms of solute-solvent and solute-solute interactions, respectively in the mixed solutions. The relation, ¢i = a0 + a1T + a2T2 , has been used to describe the temperature dependence of the standard partial molar volume ( ¢i ). The structure making or breaking ability of carbohydrates has been discussed in terms of sign of (8 2¢i / 8T 2 ) as well as dB/dT- The activation p J parameters of viscous flow were also determined and were discussed by the application of transition state theory. CHAPTER-XI This chapter contains Apparent molar volumes ( ¢v) and viscosity Bcoefficients for the alkaloid- caffeine in (0.00, 0.03, 0.05 and 0.07) mol · dm-3 aqueous thorium nitrate, Th(N03)4 solutions have been determined from solution density and viscosity measurements at temperatures in the range (298.15 to 318.15) K as function of concentration of caffeine. In the investigated temperature range, the relation:
Open Access
Preparation, characterization of bimetalic nanoparticles soakedon poly-ionic resins and their ctalalytic applications
(University of North Bengal, 2014) Sengupta, Debasish; Basu, Basudeb
The fields of catalysis and nanoscience have been inextricably linked to each other for quite some time. Several inorganic or organic materials like mesoporous silica, zeolites, charcoal, graphene oxides as well as organic polymers have been used either to promote surfacemediated reactions or to immobilize metal nanoparticles for catalytic performance. Both mono- and bi-metallic nanoparticles (NPs) embedded with heterogeneous supports exhibit improved catalytic activity and find applications in several industrial processes. Development of more active, versatile and recyclable catalysts has remained the contemporary challenges in this field of chemistry and catalysis. The present thesis entitled “PREPARATION, CHARACTERIZATION OF BIMETALLIC NANOPARTICLES SOAKED ON POLYIONIC RESINS AND THEIR CATALYTIC APPLICATIONS” has made some efforts to demonstrate new heterogeneous surface-promoted reactions as well as to develop mono- and bi-metallic nanocomposites mainly based on poly-ionic resins and graphene-based carbonaceous materials. These two different heterogeneous supports, either free or embedded with metals, have been utilized in diverse C−C, C−S and S−S bond-forming reactions. The thesis is divided into eight chapters. Chapter I summarizes a brief review on heterogeneous catalysis, nanocomposites and their catalytic applications. Chapter II describes the use poly-ionic resin hydroxide (Amberlyst® A-26(OH)), as an efficient heterogeneous base for the preparation of organic disulfides from alkyl and acyl methyl thiocyanates. Further extension of this protocol has been tested using two different organyl thiocyanates to prepare unsymmetrical disulfides. The present protocol shows the advantage of using the heterogeneous base Amberlyst A-26(OH) over some existing homogeneous bases (NaOH, NH3, K2CO3). The recyclability was also checked. Chapter III delineates a simple procedure for the preparation of poly-ionic amberlite resins embedded with CuO NPs (referred to as CuO@ARF). The as synthesized heterogeneous catalyst CuO@ARF was characterized and successfully applied in C−S cross–coupling reaction under ligand–free and 'on–water' conditions. Low loading of the catalyst, recyclability without leaching and chemoselectivity between aromatic halides are notable features. Further application of the chemoselectivity has been demonstrated in the synthesis of bioactive heterocyclic scaffold phenothiazine. Chapter IV deals with the bi-metallic nanocomposite material. Cationic and macroporous amberlite resins with formate (HCOO¯) as the counter anion (ARF) have been used to prepare a new class of heterogeneous Pd/Cu bimetallic composite nanoparticles (NPs) (Pd/Cu–ARF). The physicochemical characteristics of Pd/Cu−ARF revealed fairly uniform distributions of composite NPs of average size~4.9 nm. The nanocomposite material (Pd/Cu ARF) exhibited high catalytic activity in the Sonogashira cross‒coupling reaction between aryl iodide and terminal alkynes. Heterogeneity of the catalytic activity was evidenced from different tests (hot-filtration and catalyst-poisoning) and the recycling ability of the catalyst was examined for five consecutive runs without any significant loss of activity. Chapter V describes further use of the Pd/Cu bimetallic composite nanoparticles (Pd/Cu ARF) in other cross‒coupling reactions like Suzuki–Miyaura and Mizoroki–Heck reactions. The bi-metallic nanocomposite material was much effective as compared to monometallic Pd–ARF catalyst, as prepared in this laboratory previously. The catalyst was also recyclable for seven consecutive runs with excellent conversions. Chapter VI depicts successful application of graphene oxide (GO) as the metal-free carbocatalysts for (i) sequential dehydration–hydrothiolation reaction from a mixture of secondary aryl alcohols and thiols in toluene and (ii) chemoselective thioacetalization of aldehyde under mild, solvent-free and aerobic conditions. Chapter VII demonstrates the catalytic activity of Ni(0) nanoparticles supported with reduced graphene oxide (Ni/RGO) in Kumada‒Corriu cross‒coupling reaction. A detail study of the catalysis was performed by varying the haloarenes and Grignard reagents. Interestingly, this catalyst was found to be equally active for the oxidative addition to the sp2 C−F bond. The recyclability of the catalyst was examined for six consecutive runs without significant loss of activity. Finally the recovered Ni/RGO was characterized by X-ray diffraction (XRD) and Raman spectroscopy and found to be unaltered. Chapter VIII describes the use of Ni/RGO nanocomposite in C−S cross‒coupling reaction. The catalyst was found to be recyclable for six consecutive runs, as examined.
Open Access
Polydentate ligands and transition metal complexes : photophysics and catalysis
(University of North Bengal, 2013) Pariyar, Anand; Bandyopadhyay, P; Biswas, A
A brief overview of polydentate ligands and their metal complexes, with special emphasis on their photophysical and catalytic behaviour, has been made. In this background, the objective, scope, and application of the present investigation have been described in Chapter I. A series of novel polydentate macrocyclic corrole ligands has been synthesized and described in chapter II. The photophysical properties of the newly synthesized family of substituted nitrophenyl free base A2B-corroles have been studied. The metal ion sensing abilities of the free base ligands are explored. The A2B corroles emerge as efficient polydentate fluorophore system for selective Hg(II) ion detection in solution. Among all the corroles, the free base 10-(tridecyloxyphenyl)- 5,15-bis(nitrophenyl)corrole substituted with a long chain has been found to exhibit the highest Hg(II) sensing ability. High guest count (up to three mercuric ions per corrole) with a high association constant is observed. The experimental evidences show that the emission intensity quenches with the addition of Hg(II) ion, initially via metal coordination and subsequently through exciplex formation. This is the first report of exciplex formation of corroles with mercury ions. The results obtained will help to improve the design of sensors for the direct determination of Hg(II) ions present in ultra low concentration. The synthesis and characterization of new iron complex of 5,10,15 tris- (difluorophenyl)corrole have been described in chapter III. The catalytic properties of newly synthesized 5,10,15-tris(difluorophenyl)iron(IV)chloride complex [(tdfc)FeIVCl] with benign tert-butylhydroperoxide as the terminal oxidant has been evaluated. The [(tdfc)FeIVCl] /t-BuOOH system has been found to efficiently catalyze the oxidation of alkanes, alkenes, alkylbenzene and alcohols at room temperature. The homolytic cleavage of the O-O bond of tert-butylhydroperoxide by the catalyst is observed and the oxygenates have been shown to be derived from organoperoxides. The results clearly indicates that the main role of the iron(IV) corrole complex is the activation of alkyl hydroperoxide rather than oxygen atom transfer (OAT). Selective hydroxylation of unactivated C-H bonds of alkanes has also been realized using catalyst [(tdfc)FeIVCl] with m-chloroperbenzoic acid as the terminal oxidant. Chapter IV describes iron-corrole complex 5,10,15-tris(pentafluorophenyl) iron(IV) chloride [(tpfc)FeIVCl] catalyzed epoxidation of olefins in ionic liquid [BMIM]PF6 medium at room temperature with different terminal oxidants. For the first time, metallocorrole catalyzed epoxidation of a series of conjugated and nonconjugated olefins has been undertaken in ionic liquid ([BMIM]PF6) medium at room temperature using different terminal oxidants such as t-BuOOH, PhIO and aqueous NaOCl. The product selectivity achieved in ionic liquid medium shows remarkable improvement over those obtained in molecular solvents. The highest product yield is achieved by a biphasic system involving ionic liquid with aqueous NaOCl as the terminal oxidant. The biphasic system provides easy recovery and recycling of the catalysts without any modification of structure. The studies of homoleptic copper dipyrromethene complex has been discussed in Chapter V. The bidentate dipyrromethene complex of Cu(II) has been synthesized. The X-ray crystal structure of [Cu(II)(dpm)2] has been determined. The neutral bis(5- (4-nitrophenyl)dipyrromethene)Cu(II) complex [Cu(II)(dpm)2] is found to undergo ligand centred oxidation process to give [Cu(II)(dpm)2 •+], which has been substantiated by combined experimental and theoretical investigation. The metal bound ligand centred oxidation at high potential is of irreversible nature. The DFT calculation reveals increase in spin density over ligand moiety in the one electron oxidized [Cu(II)(dpm)2] complex, suggesting radical character of the ligand. Complex [Cu(II)(dpm)2] is found to catalyze C-H activation of alkanes and alkenes with tertbutylhydroperoxide at room temperature. The oxidation under ambient condition with benign terminal oxidant clearly indicates the involvement of the ligand based oxidation of [Cu(II)(dpm)2] in catalyzing C-H activation at room temperature. Chapter VI presents the ligand co-opertative effect in metal complex catalyzed oxidation elaborating the role of redox-neutral or redox-innocent cyclam ligand (1,4,8,11-tetraazacyclotetradecane) in C-H bond activation. The chapter describes efficient and selective hydroxylation of cycloalkanes (R-H→R-OH) catalyzed by high spin non-heme iron(III) cyclam complex [FeIII(cyclam)(OTf)2]OTf with hydrogen peroxide under mild condition. Remarkable increase in conversion and selectivity has been achieved by the addition of acid suggesting acid promoted O-O bond heterolysis. The efficient functional model of monoxygenase group of enzyme based on a highspin iron(III) complex of cyclam [FeIII(cyclam)(OTf)2]OTf provides the first example wherein a non-heme iron complex catalyzes alkane hydroxylation with 100% selectivity. The intercalation of cis-[Fe(III)(cyclam)Cl2]Cl (cyclam = 1,4,8,11- tetraazacyclo- tetradecane) complex on smectite montmorillonite K-10 is described in chapter VII. The intercalated solid is fully characterized using powder EDXRF, XRD, TGA, IR and UV-Visible analysis. Complex cis-[Fe(III)(cyclam)Cl2]Cl intercalated into Montmorillonite K-10 emerges as an efficient catalyst for selective hydroxylation (R-H→R-OH) of alkanes using environmentally benign H2O2 at room temperature. Cyclohexane and adamantane are selectively oxidized to their corresponding alcohols with remarkably high turnover number (198 and 265 respectively). Relative reaction without the clay matrix proves that a cooperative effect between the constituents of the intercalated catalyst is responsible for the enhanced selectivity
Open Access
Study on thermodynamic and transport properties of some solution systems with reference to manifestation of solvation effect
(University of North Bengal, 2013) Dewan, Rajani; Roy, Mahendra Nath
In ‘Solution Chemistry’ broadly three types of approaches have been made to estimate the extent of solvation. The approaches involves the studies of viscosity, conductance, etc., of electrolytic solutions and the derivation of various factors associated with ionic solvation, the second is the thermodynamic approach by measuring the free energies, enthalpies and entropies of solvation of ions from which factors associated with solvation can be elucidated, and the third is spectroscopic measurements where the spectral solvent shifts or the chemical shifts determine their qualitative and quantitative nature. Studies of thermodynamic properties of electrolytes, along with transport and acoustic studies, give very valuable information about ion-ion and ionsolvent interactions in solutions. The influence of these interactions is sufficiently large to cause dramatic changes in chemical reactions involving ions. The changes in ionic solvation have important applications in diverse areas as organic and inorganic synthesis, studies of reaction mechanisms, non-aqueous battery technology and extraction. Using mixed solvents in these studies enable the variation of properties such as dielectric constant or viscosity, and therefore the ion-ion and ion-solvent interactions could be better studied. Consequently, a number of conductometric and related studies of different electrolytes in non-aqueous solvents, especially mixed organic solvents, have been made for their optimal use in high-energy batteries and for understanding organic reaction mechanisms. Thus, extensive studies on electrical conductance in mixed organic solvents have been performed to examine the nature and magnitude of ion-ion and ion-solvent interactions. CHOICE OF SOLVENTS AND SOLUTES Solvents such as Nitromethane, 1,3-Dioxolane, Nitrobenzene, Methanol, Ethylene glycol, n-Hexanol, o-Toluidine, Aniline, Acetonitrile, N,NDimethylformamide, N,N-Dimethylacetamide and Dimethylsulphoxide have been used in the research work because these solvents are industrially very important and by mixing these solvents we could obtain a wide variation of viscosities and dielectric constants giving us an optimum environment for the study. The electrolytes used in the research work are Sodium Tetraphenylborate, Tetrabutylammonium Tetraphenylborate, Lithium Hexafluoroarsenate, Tetraalkylammonium Iodides, 1-Ethyl-3-methylimidazolium Bromide and Tetrabutylammonium Hexafluorophosphate. These electrolytes are used as reference and supporting electrolytes and are used as non-aqueous electrolytes in electrochemical applications. METHODS OF INVESTIGATION Different experimental techniques are employed to get a better insight into the phenomena of solvation and different interactions prevailing in solution. The techniques used to study various interactions in solution are: Densitometry, Viscometric, Conductometry, Ultrasonic Interferometry and Refractometry. PHYSICO-CHEMICAL PARAMETERS AND THEIR SIGNIFICANCE Limiting molar conductance (Λ0) gives an idea about the ion-solvent interaction in the solution. Association constant (KA) obtained from the conductance study gives an idea about the solvation of the ions. Partial molar volume ( 0 V φ ) and Viscosity B-coefficient obtained from the density and viscosity values respectively indicates the extent of ion-solvent interaction in a solution. From experimental speed of sound values, limiting apparent molar adiabatic compressibility ( K φ ° ) and the experimental slope ( * k S ) can be estimated. These parameters also give an idea about the ion-solvent and ion-ion interaction in the solution. SUMMARY OF WORKS DONE CHAPTER I This chapter contains the objective and applications of the research work. CHAPTER II This chapter contains the general introduction of the thesis and forms the background of the present work. A brief review of notable works in the field of ion-solvent interaction has been given. CHAPTER III This chapter contains the experimental section which mainly involves the structure, source, purification and application of the solvents and solutes used in the research work and the details of the instruments used for the study. CHAPTER IV In this chapter precise measurements on electrical conductance of sodium tetraphenylborate and tetrabutylammonium tetraphenylborate in different mass fraction (0.00–1.00) of nitromethane in nitrobenzene at 298.15K have been represented. Limiting molar conductances (Λ0), association constants (KA) and co-sphere diameter (R) for ion-pair formation in the mixed solvent systems were evaluated using the Fuoss conductance-concentration equation. FT-IR measurements for the solvents and solutions have been undertaken. CHAPTER V This chapter includes the study of electrolytic conductivities (Λ ), densities (ρ ), viscosities (η ), refractive indices (nD) and speed of sound (u) of tetrabutylammonium hexafluorophosphate in nitromethane, 1,3-dioxolane and nitrobenzene at 298.15 K. The limiting molar conductivities ( o Λ ), association constants (KA), and the distance of closest approach of the ion (R) have been evaluated using the Fuoss conductance equation. Triple ion formation in 1,3- dioxolane has been analyzed by Fuoss-Kraus theory of triple-ions. The limiting apparent molar volumes( 0 V φ ), experimental slopes( V * S ) derived from the Masson equation, and viscosity A and B coefficients using the Jones-Dole equation have been interpreted in terms of ion-ion and ion-solvent interactions, respectively. Molar refraction ( M R ) have been calculated using the Lorentz- Lorenz equation. The adiabatic compressibility ( S β ) have been evaluated using the u values. The limiting apparent molar adiabatic compressibility ( 0 K φ ) have been calculated and discussed. CHAPTER VI This chapter includes the study of electrolytic conductivities of tetraalkylammonium iodides, R4NI (R= butyl to heptyl) in (0.00, 0.25, 0.50 and 0.75) mass fraction of o-toluidine in n-hexanol at 298.15 K. Limiting molar conductances (Λ0), association constants (KA) and the co-sphere diameter R for ion-pair formation in 0.00 and 0.25 mass fraction of solvent mixture have been evaluated using the Fuoss-Equation. Triple-ion formation in 0.50 and 0.75 mass fraction of o-toluidine in n-hexanol has been analyzed by the Fuoss-Kraus theory of triple ions. CHAPTER VII Conductometric studies of 1-ethyl-3-methylimidazolium bromide in acetonitrile, methanol, N,N-dimethylformamide, N,N-dimethylacetamide and dimethylsulphoxide were undertaken at 298.15K. FT-IR measurements were supplemented to explain the ion-dipole interaction in the solution. The extent of interaction is expressed in terms of the association constant (KA) and shows the ion-dipole interaction to be a function of viscosity. CHAPTER VIII In this chapter, conductivities of some tetraalkylammonium iodides were measured at 298.15 K aniline. The observed molar conductivities were analyzed by Fuoss-Kraus theory of triple-ions. A linear relationship between the triple-ion formation constants [log (KT / KP)] and the salt concentrations at the minimum conductivity (log Cmin) have been given for all salts in aniline. The formation of triple-ions has been explained on the basis of coulombic interactions and covalent bonding forces operative between the ions. CHAPTER IX In this chapter, the electrolytic conductivities, densities and viscosities of lithium hexafluoroarsenate have been studied in different mass fraction of ethylene glycol in methanol at 298.15 K. The limiting molar conductivities (Λ0), association constants (KA) and the distance of closest approach of the ion (R) have been evaluated using the Fuoss conductance equation. The limiting apparent molar volumes (φV o), experimental slopes (SV *) derived from the Masson equation and viscosity A and B-coefficients using the Jones-Dole equation have been interpreted in terms of ion-ion and ion-solvent interactions respectively. CHAPTER X This chapter contains the concluding remarks of the works related to the thesis.
Open Access
Physico-chemical investigations on the ion-solvent interactions of some Tetraalkylammonium and common ions in non-aqueous and mixed binary aqueous solvent systems
(University of North Bengal, 1992) Das, Bijan; Hazra, D.K.
Open Access
Exploration of the chelation property of few newly designed (N,O)-type schiff base ligands with d-block metals and bio-oxidase activities of their synthetic coordination compounds
(University of North Bengal, 2023) Mahato, Shreya; Biswas, Bhaskar
This dissertation comprises a total of seven chapters. Chapter I consists of a concise introduction to the design, foundation, and applications of the coordination compounds based on synthetic and commercially available ligands and the applicability of the present work in the recent trends of scientific development. Chapter II represents the synthesis, X-ray structural analysis, supramolecular architectures, and oxidative coupling of 2-aminophenol of a copper(II) complex, [Cu(L1)](H2O) (1) containing a previously reported Schiff base, H2L1 = 2,2'-((1,2- phenylenebis(azanylylidene))bis(methanylylidene))diphenol. The analysis of the crystal structure indicates that the Cu(II) centre adopts a square planar coordination geometry within the R3̅ space group. Furthermore, the aqua molecule located nearby actively participates in significant intermolecular hydrogen bonding, resulting in the formation of a water-mediated dimeric unit of the Cu(II) complex. The Hirshfeld surface analysis suggests that C−H…O and O−H…O types of hydrogen bonding, as well as π⋯π interactions play a crucial role. The catalytic properties of complex 1 were assessed for the oxidative dimerization of 2-aminophenol (2-AP) in methanol, revealing high catalytic efficiency with a kcat/KM value of 2.14×105. Additionally, studies utilizing mass spectrometry confirmed that the catalytic process involves the formation of an enzymesubstrate adduct in the solution phase. Chapter III represents the synthesis, X-ray structural analysis, Hirshfeld surface analysis, oxidative dimerization of 2-aminophenol and antibacterial activity of a newly designed copper(II)-Schiff base complex, [Cu(L2)2] (2), [Schiff base (HL2) = 2-(2- methoxybenzylideneamino)phenol]. X-ray analysis of complex 2 reveals that the Cu(II) complex forms crystals in a cubic crystal system with the Ia3̅ d space group. In its crystalline phase, the Cu(II) centre adopts a unique tetragonal bipyramidal geometry. Complex 2 has been tested for its phenaxozinone synthase activity in acetonitrile, mimicking biological systems, and demonstrated significant catalytic activity with a high turnover number of 536.4 h−1. Electrochemical analysis of complex 2 showed the appearance of two additional peaks at −0.15 and 0.46 V in the presence of 2-AP. This suggests the formation of AP−/AP•− and AP•−/IQ redox couples in the solution. The presence of the iminobenzosemiquinone radical at g = 2.057 was confirmed in the reaction mixture through electron paramagnetic resonance, indicating its role as the driving force for the oxidative dimerization of 2-AP. The ESI-mass spectrum exhibited a peak at m/z 624.81 for complex 2 in the presence of 2-AP, confirming that the catalytic oxidation proceeds through the formation of an enzyme-substrate adduct. Furthermore, complex 2 showed potential antibacterial properties against pathogenic bacterial species such as Staphylococcus aureus, Enterococcus, and Klebsiella pneumonia. Scanning electron microscope studies provided evidence that the antibacterial activity is attributed to the destruction of the bacterial cell membrane. Chapter IV represents the synthesis, crystal structure, supramolecular architecture, 4- methylcatechol oxidation, and bactericidal activity of an interesting zinc(II)-Schiff base complex, [Zn(L2)2Cl2] (3), [Schiff base (HL2) = 2-(2- methoxybenzylideneamino)phenol]. The analysis of the crystal structure of complex 3 indicates that the zinc centre is present in a distorted tetrahedral arrangement. The Schiff base molecule adopts three donor centres, but it becomes protonated and exists as a zwitterionic form, acting as a monodentate coordinator towards zinc. Complex 3 has been studied for its ability to catalyse the biomimetic oxidation of 4-methylcatechol (4-MC) in methanol, and it demonstrates high efficacy with a good turnover number of 1.45 × 103 h−1. Various techniques such as electrochemical studies and electron paramagnetic resonance analysis have been employed to investigate the behaviour of complex 3 in the presence of 4-MC. The results confirm that the catalytic reaction proceeds through enzyme-substrate binding, and the generation of radicals during the catalytic process drives the oxidation of 4-MC. Additionally, an antibacterial study has been conducted against several clinical pathogens including Bacillus sp, Enterococcus, and E. coli. To assess the antimicrobial properties of complex 3, scanning electron microscope and EDX analysis were performed on the pathogens treated with a low dosage of the complex. The results reveal the destruction of the bacterial cell membrane in the selected zone of inhibition area, with a zinc occurrence of 1.44%. This finding holds significant promise for the development of future antibacterial agents. Chapter V represents the synthesis and crystal structure of a palladium(II) complex [(κ4- {1,2-C6H4(N=CH−C6H4O)2}Pd] (4) supported by a dianionic salen ligand [1,2- C6H4(N=CH−C6H4O)2]2− (H2L1) was synthesized and used as a molecular pre-catalyst in the hydroboration of aldehydes and ketones. Complex 4 was evaluated as an effective catalyst in the hydroboration of aldehydes and ketones using pinacolborane (HBpin). This process yielded boronate esters in exceptional yields at room temperature without the need for solvents. Furthermore, complex 4 demonstrated its competence as a catalyst in the reductive amination of aldehydes with HBpin and primary amines. This reaction occurred under mild and solvent-free conditions, resulting in a high yield (up to 97%) of secondary amines. Both methodologies exhibited remarkable conversion rates, excellent selectivity, and a wide range of applicability, accommodating electron-withdrawing, electron-donating, and heterocyclic substituents. A computational investigation utilizing density functional theory (DFT) elucidated the reaction mechanism behind the complex 4-catalyzed hydroboration of carbonyl compounds in the presence of HBpin. Additionally, the protocols unveiled the dual functionality of HBpin in facilitating the hydroboration reaction. Chapter VI represents the design and preparation of metal complex salts of the novel hybrid d-f block type, [Cu(bpy)2]2[Ce(NO3)6]2 (5), [Cu(phen)2(NO3)]2[Ce(NO3)6](HNO3) (6), [Zn(bpy)2(NO3)][ClO4] (7), and [Zn(phen)2(NO3)]2 [Ce(NO3)6] (8); [bpy = 2,2'- bipyridine; phen = 1,10-phenanthroline]. X-ray analysis of the structures of 5 and 6 reveals that the copper(II) centres in the cationic complex units have highly distorted tetrahedral and rare bicapped square pyramidal coordination geometries, respectively. Similarly, 7 and 8 exhibits rare bicapped square pyramidal geometry for their zinc(II) ions, while 5, 6, and 8 contain cerium(IV) ions arranged in a dodecahedral geometry. Studying the supramolecular interactions, it is observed that intermolecular O⋯H and O⋯π short contacts contribute to binding the complex units in 5. In contrast, complex salt 6 demonstrates predominantly π⋯π interactions, along with O⋯H and O⋯π short contacts, which facilitate binding among the complex units. To investigate the chargetransport phenomenon, we utilized complex salts (5-8) to construct Schottky devices. The carrier mobilities (μ) for salts 5-8 were determined as 1.76 × 10−6, 9.02 × 10−6, 1.86× 10−8, and 4.31 × 10−8 m2 V−1 s−1, respectively, with corresponding transit times (τ) of 439, 85, 4.17 × 103, and 1.79 × 103 ns. These results indicate that complex salt 6 exhibits the highest transport properties among all the complex salts. Analysing the charge-transport properties from a crystal engineering perspective, the superior performance of 6 can be attributed to its predominant π⋯π interactions. Overall, the synthesis of these novel complex salts, along with their physicochemical properties and charge-transport applications, holds significant promise for the development of new crystalline materials with intelligent functionalities. Chapter VII outlines an overview of the progress made thus far and identifies prospective avenues for future research.

Department of Chemistry

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