Chemistry of selected d-block elements with some bi- and multi- dentate N- donor ligands

The main objective of this thesis is to develop some newer aspects of the chemistry of some transition (Fe, Ni, Pd, Ru and Cu) and non-transition metals (Zn, Cd and Hg) by means of studying their new mono- and poly-nuclear complexes of some bi- and polydentate ligands. The ligands will have N donor sites. Some hetero donor atoms are incorporated in the ligand frameworks for the sake of comparison. The new complexes will be characterised by magnetic susceptibility studies, mass spectrometry, EPR, NMR, ATR, Resonance Raman, UV-Vis spectra, Emission spectra, Mössbauer spectra and other spectroscopic methods. Wherever possible, structure will be determined by X-ray crystallography. Electrochemical techniques like cyclic voltammetry and coulometry will be used for uncommon oxidation states of metals. Various quantum mechanical theories like AM1, MP2, DFT and AIM etc. will be applied to examine structure reactivity correlations. This thesis begins with a brief introduction (chapter I) to the coordination chemistry of some transition and non-transition metals relevant to the present study. Chapter II deals with the chemistry of transition metal complexes with bidentate N-donor ligands like 1,10-phenanthroline and 5,6-dihydro-5,6-epoxy-1,10-phenanthroline. Uncommon Cu(II)-S8 bond, six coordinate Cu(I) in solution, crystallisation of an MLCT state in iron complexes, epoxide ring opening in a zinc complexes without any catalyst in a diastereoselective mannar, substituents’ effect on10Dq have been determined for nickel complexes and heteroleotic metal complexes also have been discussed in chapter II. A tridentate ligand L (dihydrazone of 2,6-diacetyl pyridine) and its metal complexes are discussed in Chapter III. Increasing denticity of L and corresponding metal complexes are also discussed. Chapter IV describes the chemistry of two tetradentate ligands derived from the condensation of benzil and 2-hydrazinopyridine, benzil dihydrazone and 2- (methylthio)benzaldehyde. Cu(II)-P bond formation, Ni-Ni and Pd-Pd bonding have been discussed. NICS and side dependent aromaticity of phosphole, a new aromaticity index, aromaticity of metallacycles and a Möbius chelate constitute Chapter V. Chapter VI introduces a new structural index for the 5-coordinate Cu(II) complexes.Research was carried out under the supervision of Prof. Dipankar Dutta of Inorganic Chemistry division under SCS [School of Chemical Sciences]Research was carried out under CSIR & DST gran

Theoretical and computational study of properties and detoxification mechanisms of chemical warfare agents, toxic chemicals and enzyme inhibitors

The thesis deals with the reaction mechanism, kinetics, molecular docking, simulation and thermochemistry of molecules having biological and toxicological interest. The high-level theoretical methods are used for accurate results and predictions.An introduction to the thesis is given in the first chapter for understanding the biological and toxicological chemistry. The second chapter describes briefly theoretical methods and techniques of computational chemistry. The rest of the chapters of the thesis are based on the published papers or on the manuscripts currently under consideration for publication. This thesis is a systematic presentation of the author’s original research works.Research was conducted under the supervision of Prof. Abhijit kr. Das of Spectroscopy division under SPS [School of Physical Sciences]Research was carried out under CSIR fellowship and gran

Study of Structural and Electrical Properties of Cathode Materials and Glassy Electrolytes

This thesis deals with the synthesis of some cathode materials and glassy electrolytes and their characterization using several techniques such as differential scanning calorimetry (DSC), X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR) studies etc. as well as electrical measurements in wide frequency and temperature range. The thesis is organized as follows: Chapter 1 presents an introduction to cathode materials and glassy electrolytes along with some precise definitions in this context. Secondly, it presents different models of ac and dc conduction in ion conducting and electron conducting systems. Finally, it presents precise objectives of the present work. Chapter 2 presents the sample preparation techniques as well as different experimental techniques such as X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE-SEM), Transmission Electron Microscopy (TEM), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FT-IR) Spectroscopy, electrical and dielectric measurements etc. In chapter 3 the micro-structural properties of the cathode compound Lix(Mn1/3Ni1/3Co1/3)O2- (x=1, 0.9 and =0, 0.05) has been studied. This compound has been prepared in solid state synthesis route using a wide range of calcination temperatures. The post-calcination heat-treatment has been employed in all the samples. The effect of calcination temperature and heat treatment on the microstructure and morphology of this compound has been studied in details. The synthesis condition of the compound has been optimized by the combination of calcinations and heat-treatment. In chapter 4 the electrical properties of the electrode compounds Li[Ni1/3Mn1/3Co1/3]O2 and Li0.9[Ni1/3Mn1/3Co1/3]O1.95 have been investigated in a wide temperature and frequency range. The temperature dependence of the dc conductivity has been explained employing polaron hopping models, proposed by Schnakenberg and Emin and co-workers, which consider the coupling of polarons with optical and acoustic phonon modes. The experimental ac conductivity data have been analyzed in the framework of several theoretical models based on quantum mechanical tunneling and classical hopping over barriers. It has been shown that the electron tunneling is dominant in the compositions in the temperature range from 93 K to 193 K. A crossover of relaxation mechanism from electron tunneling to polaron tunneling is observed at 193 K. In chapter 5 the structural and electrical properties of CdI2 doped silver polyphosphate, meta-phosphate and ultra-phosphate glassy electrolytes have been investigated. Xray diffraction, scanning and transmission electron microscopic study has been performed to investigate the presence of crystalline phases within the glassy matrix. The identification of different crystalline phases has been performed by analyzing the selected area electron diffraction (SAED) patterns. Electrical properties of the compositions have been investigated in a wide temperature and frequency range. The electrical data have been analyzed in the framework of the conductivity and the modulus formalisms. It has been shown that the increase or decrease of the conductivity in these glasses depends on the degree of Cd-Ag exchange. In chapter 6 the mixed glass former effect has been investigated in silver borophosphate glassy electrolytes. The micro-structural study of the compositions has been performed by employing different experimental techniques such as XRD, SEM, TEM, DSC etc. The network structure of the glassy electrolytes has been analyzed from FTIR spectra. The population of BO4 and BO3 units in these compositions has been determined from deconvolution of FTIR spectra. Electrical properties of the compositions have been investigated in a wide temperature and frequency range. The experimental data have been analyzed in the framework of conductivity and modulus formalism. Two different types of microscopic length scales of ion dynamics such as characteristic length scale and spatial extent of ion motion have been estimated from linear response theory. It has been shown that the dc conductivity and microscopic length scales of ion motion are strongly correlated to the population of BO4 and BO3 units. In chapter 7 two different phenomena have been investigated. First one is mixed glass former effect in silver boro-phosphate glassy electrolytes in presence of a dopant CdI2. The second one is immobile salt effect in CdI2 doped silver boro-phosphate glassy electrolytes. The micro-structural study of the compositions has been performed by employing different experimental techniques such as XRD, SEM, TEM, DSC etc. The network structure of the glasses has been analyzed from FTIR spectra. Electrical properties of the compositions have been investigated in a wide temperature and frequency range. The experimental data have been analyzed in the framework of conductivity and modulus formalism. It has been observed that different physical properties such as dc conductivity, glass transition temperature, density etc. are different in CdI2 doped borophosphate glassy electrolytes from that for undoped borophosphate glassy electrolytes. It has been shown that the mixed former effect and immobile salt effect are correlated to each other.The research was conducted under the supervision of Prof. Aswini Ghosh of the Solid State Physics division under SPS [School of Physical Sciences]The research was carried out under the RCI (DRDO) and DST Gran

Some Studies on the Prospect of Finding New Physics Beyond the Standard Model at the LHC

After the discovery of a ∼ 125 GeV Higgs boson at the Large Hadron Collider (LHC), now the Standard Model (SM) of particle physics is complete although there are still some doubts over the fact that this can be a beyond the Standard Model (BSM) Higgs boson. More updated data on Higgs boson coupling measurements will reveal its true identity. Meanwhile, we need to go beyond the SM to address some vital experimental findings. One of them is the neutrino oscillation data that indicates at least two neutrinos have tiny but non-zero masses. The other one is the existence of Dark Matter (DM) revealed from cosmological data. Weak scale supersymmetry (SUSY) is the most popular choice for explaining these new physics phenomena beyond the SM. However, even Minimal Supersymmetric Standard Model (MSSM) itself is not sufficient to explain the neutrino oscillation data under R-parity conserving scenario. In this thesis, we, therefore, attempt to explore a SUSY model with added singlets that can account for small neutrino masses by means of inverse seesaw mechanism. As a consequence, we can have a mixed sneutrino lightest SUSY particle (LSP) that may be as light as ∼ 50 GeV. Within R-parity conserving scenario, this LSP can serve as a very good DM candidate satisfying all existing constraints arising from collider, DM and low energy experiments. This model can have enhanced same-sign dilepton final states with large missing energy coming from gluino and squark pair as well as squarkgluino associated productions and their cascade decays through charginos. The two body decays of the lighter chargino into a charged lepton and a singlet sneutrino has a characteristic decay pattern which is correlated with the observed large atmospheric neutrino mixing angle. This feature can be probed at the LHC through trilepton channel. Moreover, the ∼ 125 GeV Higgs boson now have a new decay channel into a pair of LSP sneutrinos that is completely invisible. Most recent data published by ATLAS and CMS collaborations at the LHC in different Higgs boson decay channels constrain this sort of non-standard decays. We perform a two parameter global analysis of the available experimental data to date to determine the optimal invisible Higgs boson branching fraction in this scenario. This new decay provides us a new missing energy channel that can be probed at the LHC. We present detailed cut-based analyses for these different proposed signals at the LHC to test the viability of such a scenario.Research conducted under supervision of Prof. Sourav Roy, Theoretical Physics division under SPS [School of Physical Sciences]Research conducted under DST research gran

Environment Induced Protein-Surfactant/Lipid Bioconjugate formation in Aqueous Medium and Air Water Interface

The interaction with proteins with surfactants have great impact due to not only fundamental interest but also enormous biological importance. In the field of application, surfactant-protein system has been playing a significant role in developing biosensors, drug delivery protocols and various biomolecular devices. The protein entrapment into vesicle membrane and immobilization of this system without de-neutralization of solid substrate is extremely valuable in wide variety of industrial, biological , pharmaceutical and cosmetic applicationsThe research was conducted under the supervision of Prof. G B Talapatra of the Spectroscopy division under SPS [School of Physical Sciences]The research was carried out under DST research grant and fellowshi

Cycloaddition-Based Approaches to Bio-active Natural Products

Natural products regime has been recognized as an invaluable source of compounds of medicinal importance. While some natural products are directly used as drugs, some drugs are derived from natural products by modification of structures. In some cases the pharmacophore is placed in a new backbone that replaces the core skeleton present in the natural product. Thus synthesis of natural products continues to be in the fore front of organic chemistry research. Carbocyclic compounds having ring sizes four to six are found in a large number of natural products with promising biological activities. Cycloaddition reactions such as [2 + 2] and [4 + 4] can be employed to access directly compounds with four and six membered rings. Ring expansion of four membered rings is one of the commonly employed approaches to construct five membered rings. This proposed investigation will employ a combination of the above approaches for synthesis of bioactive natural products containing four to six memebered rings. Synthesis of optically active natural products using naturally occurring optically active materials is the most efficient way when their availability and adaptability are fulfilled. However, such cases are rare as great variety of natural products exist while adaptable chiral compounds are very limited. Therefore, finding certain common chiral pools adaptable to versatile target molecules is one of the most important tasks in organic synthesis. A programme has been initiated in July, 2010 under the supervision of Professor Subrata Ghosh, F.A.Sc, F.N.A Department of Organic Chemistry, Indian Association for the Cultivation of Science, Jadavpur, Kolkata – 700 032 for the synthesis of enantiopure organic compounds starting from nature’s chiral pool starting material D-mannitol. Investigation embodied in this dissertation entitled “Cycloaddition-Based Approaches to Bio-active Natural Products” is directed towards the development of synthetic methodologies for some fused carbocyclic system present in natural products. The present thesis addresses the above mentioned themes of contemporary interest in organic chemistry and is presented in three chapters. In Chapter 1, a brief review on construction of cyclobutane ring system is described. Chapter 2 deals with synthetic studies toward kelsoene. Approach to the asymmetric synthesis of a functionalized tricyclo[6.2.0.0 2,6 ]decane ring system present in kelsoene and poduran employing stereocontrolled copper (I)-catalyzed intramolecular [2+2] photocycloaddition, and RCM reaction as the key steps. Chapter 3 deals with synthetic studies on erythrodiene and spirojatamol. The key steps involve (i) pinacol-type rearrangement of a cyclobutane derivative, (ii) copper(I)-catalyzed intramolecular [2 + 2] photocaycloaddition of a diene prepared from (+) dihydrocarvone to form oxabicyclo[3.2.0]heptanes derivative. ii The subject matter of each part has been structured under following headings: Introduction, Background, Results and Discussion, Conclusion, References, Experimental and NMR Spectra. In keeping with the general practice of reporting scientific observations, due acknowledgements have been made to the findings of other investigators.A Thesis Submitted for the Degree of Doctor of Philosophy (Science) of Jadavpur University by AMRITA GHOSHResearch had been conducted in the division of Organic chemistry under IACS fellowship under the supervision of Prof. Subrata Ghosh, O

Study of magnetic interaction in transition metal complexes

Recent times, the major goal of studying polynuclear coordination complexes is to elucidate their interesting properties, which could have prospective applications to develop modern technology. Designing of polynuclear transition metal complexes with Schiff base or small molecular organic ligands and studying their magnetic interactions including macroscopic magnetic properties such as magnetic hysteresis, photomagnetism, nanomagnetism, spin crossover and so on, to explore the possibility of new technological applications are the major concerning subject of this thesis. Along with magnetic measurements, various structural and spectroscopic characterizations such as X-ray crystallography, electrical measurements (impedance spectroscopy), UV-Vis absorption, EPR, FTIR, Mossbauer study etc were used to investigate their structures as well as several molecular properties associated with their magnetic behaviour. We have also used theoretical calculations based on density functional theory in order to understand their magneto-structural correlations.The research was conducted under the supervision of Prof. Shyamal Kr. Saha of the Materials Science division under SMS [School of Materials Sciences]The research was carried out under CSIR fellowship and research gran

Study of Improved Dielectric Properties of Some Technologically Important Flexible Inorganic Oxide-Polymer Composites

The rapid development of the electronics industry requires easily synthesized as well as inexpensive electronic components which would offer higher performance yet with smaller size. In this regard, ceramic polymer (C/P) composites with 0–3 connectivity are especially attractive for various applications due to their ease of fabrication, and they have thus been widely studied over the last couple of decades. In such composites, the 0–3 connectivity is formed by suspending 0–dimensional ceramic particles within a 3–dimensional continuative polymer matrix host. The ability to make a composite of a particular, bespoke permittivity and permeability (albeit within certain limits) provides useful degrees of freedom in applications and design. Additionally, 0–3 composites provide opportunities to develop materials with the combined magnetic and dielectric properties desired for multifunctional components. The principal advantage to be had is the downsizing of telecommunication devices. By combining high-permittivity ceramic powders with ductile polymers, composites with good dielectric properties can be developed. In general, the properties achievable with composites depend on the initial matrix and filler properties. With 0–3 type composites, their dielectric and magnetic properties are dominated by the guest material. In this respect, ferroelectric high- εr ceramic or conductive fillers have been widely studied, because of their potential applications such as high charge-storage capacitors, artificial muscles, smart skins, and apparatus used in high-speed integrated circuits. Even though many ceramic materials like BaTiO3, Ba(Sr, Ti)O3, Pb(Zr, Ti)O3, Pb(Mg, Nb)O3 etc. that have a high dielectric permittivity and a low dielectric loss are presently used in electronic fields, they are generally brittle in nature, sintered at high temperature and entail a complicated fabrication process. To overcome these disadvantages, C/P composites are better alternatives and offer excellent material characteristics, such as flexibility, machinabilty, low-temperature process ability and tailored dielectric properties. Such flexibility in the fabrication of inductive and capacitive circuit elements would be highly advantageous in telecommunication and related applications. Generally polymers offer good mechanical flexibility and high electrical breakdown strength but suffer from low dielectric permittivity (low- εr). Many efforts have been devoted to achieve enhanced εr values with low dielectric loss.Research was conducted under the supervision of Prof. B K Chowdhury of the Solid State Physics division under SPS [School of Physical Sciences]Research was carried out under DST & CSIR gran

Synthesis and Functionalization of Carbon-Based Nanomaterials for Biomedical and Environmental

The work presented in this thesis entitled “Synthesis and Functionalization of Carbon-Based Nanomaterials for Biomedical and Environmental Application” was initiated by the author in July, 2010 in Centre for Advanced Materials, Indian Association for the Cultivation of Science, Kolkata, under the supervision of Dr. Nikhil Ranjan Jana. Numerous types of nanomaterials have been exploited gradually for the rapid development of nanotechnology in different applications such as biological science, photocatalysis, catalysis, solar cell, fuel cell, nanoelectronics, optical detection ete. Convensional tunable emissive semiconductor quantum dots (QD) and gold nanoparticles are widely used in ongoing research. But these QD are composed of toxic metals such as cadmium (Cd) and non-metals like selenium (Se), tellurium (Te) etc. Consequently, human sivilization and environment being gradually affected by applying such QD. Gold nanoparticle-based probes afford dark field imaging which has limited applications for cellular imaging because of the high scattering background from the cell. Besides fluorescent nanomaterials based on doped semiconductor nanocrystals, fluorescent gold clusters and fluororescent silicon nanoparticles are under development and have yet to exhibit performances size with enhanced tunable emission from blue to red via carbonisation approach from different types of carbohydrates. The as prepared FCN are hydrophilic and hydrophobic in =seere and their fluorescence quantum yield varies from 6-30 %. These particles also exhibit sxe-dependent, tunable visible emission. These FCN have been transformed into similar «eed various functionalized nanoprobes by linking with folic acid, long chain amine and TAT peptide. Long chain amine and TAT peptide functionalization increase the cellular eptske and efficiency, whereas folate functionalization offers specific detection and imaging of cancer cells. The small size of these nanoprobes affords easier subcellular targeting. Chapter 5 describes interdigited bilayer type coating strategy which provides both eellieadal stability and functionalization option for graphene. Colloidal graphene oxide have Seen first converted into interdigited bilayer coated graphene oxide and next they have been transformed into colloidal graphene by hydrazine reduction. These coated graphenes can be Secber transformed into colloidal functional graphene using covalent conjugation chemistry. Functional graphene has been synthesized for optical detection of enzyme where a flourescent dye is covalently linked through a peptide so that the dye fluorescence is quenched by graphene but switches on once enzymes cleave the peptide bond. The qemeediested bilayer coating reported here is unique as it provides an optimum coating Geckness (< 3 nm), offering optically responsive graphene fluorophore substrate with high colloidal stability. Chapter 6 describes a simple and large scale synthesis method for graphene-silver nanoparticle based composite for sunlight induced mineralisation of colourless endocrine disruptors (phenol, bisphenol A and atrazine). It is found that photocatalytic efficiency of the composite under visible light is significantly higher as compared to graphene or silver nanoparticle. It is proposed that presence of graphene not only provides a large surface area support for the Ag nanoparticle and organic molecule, but also stabilises charge separation via electrons transfer, thereby enhancing photocatalytic efficiency through oxidative degradation of organic pollutants. Chapter 7 describes the summary of all the chapters and scope of my work has been described. Attention has been given to incorporate all the current references related to this contemporary area of research. Any unintended omission is deeply regretted.The research was carried out under the supervision of Prof. N R Jana under SMS [School of Materials Sciences]The research was conducted under CSIR research gran

Synthetic Studies on the Catalysis by Supported Metal, Metal Nanoparticles and Other Benign Materials

The main object of this present work is to develop useful synthetic procedures using transition metal based catalysts and Photocatalysts in an environmentally benign way. The thesis has been divided into four chapters. Chapter-1 deals with “Heterogeneous Catalysis’’. In chapter-I, section-I, a brief review on heterogeneous Cu catalyst has been described. Section II consists of Heterogeneous Cu-Al2O3 catalyzed solvent controlled N-arylations of cyclic amides and amines with bromoiodoarenes. Chapter-2 consists of two sections where section-I explains the catalytic activity of Cu nanoparticles in various organic reactions. In section-II magnetically separable CuFe2O4 nanoparticle catalyzed S-vinylations and S-arylations have been demonstrated. Chapter-3 of the thesis is based on “Catalysis by Homogeneous Metal Complexes” and has been split into two sections. Section-I includes a brief review on the homogeneous Ni catalysts and their applications in organic synthesis. Section-II describes Ni-Cu co-catalyzed cross coupling of styrenyl and vinyl halides with phenols for the synthesis of aryl-vinyl ethers. Chapter-4 of the thesis deals with “Sustainable synthesis of organoselenides and tellurides’’. In chapter-4, section-I, a brief review on the synthesis of organoselenides has been described. Section-II contains Zn mediated synthesis of diaryl chalcogenides from aryl diazonium tetrafluoroborates. Section III includes a brief review on recent developments of photoredox catalysis in organic synthesis and after that a direct synthesis of aryl and heteroaryl amines to selenides has been discussedResearch was conducted under supervision of Prof. B C Ranu, Organic Chemistry division under SCS [School of Chemical Sciences]Research was conducted under CSIR fellowship & DST research gran