The thesis entitled “Local structure-property relationship in some selected Solid State Materials” mainly focuses on two fundamental topics: (a) evaluation of some standard global structural concepts in terms of local structure to provide a unique description of the crystal structure, and (b) the role of the crystal structure at different length-scales in controlling the properties in some selected materials.

The work carried out in this thesis systematically investigates the correlation between microstructures and electronic properties of organic semiconductors. The major directions that were pursued in this thesis are: (i) studies on structure-property relationship by rational design and synthesis of monodisperse oligomers with varying chain-lengths (ii) role of electronic properties and aggregation (microstructures) in governing singlet fission (SF). In the first part of the thesis, the optical, structural and charge transport properties of Diketopyrrolopyrrole (DPP)-based oligomers, as a function of the chain length, has been discussed. The energy bands became wider with an increase in chain length and a gain in backbone electron affinity was observed, with an offset in microstructural order. With an increase in chain length, the tendency to form intramolecular aggregates increased as compared to intermolecular aggregates due to the onset of backbone conformational defects and chain folding. An insight into the solid-state packing and microstructural order has been obtained by steady-state and transient spectroscopy, grazing incidence small angle x-ray scattering (GISAXS), atomic force microscopy (AFM) and transmission electron microscopy (TEM) studies. The charge-carrier mobilities varied in accordance with the degree of microstructural order as: dimer > trimer > pentamer. A library of DPP-DPP based trimers was also generated by modifying the donor chromophore (phenyl, thiophene and selenophene) in the oligomer backbone. Highest n-channel mobility of ~0.2 cm2V-1s-1 was obtained which validated that: (a) the effect of solid-state packing predominates the effect of backbone electronic structure on charge carrier mobility. Although oligomers possess lesser backbone defects than polymers in general, their charge carrier mobilities were not comparable to that of 2DPP-OD-TEG polymer, which forms highly oriented and isotropic edge-on crystallites/microstructures in the thin film, shows high n-channel mobility of 3 cm2V-1s-1 and band-like transport ;(b) although delocalized electronic states are achieved at greater chain lengths, the degree of solid-state microstructural order drastically reduces which leads to lower charge carrier mobilities; (c) conformational collapse resulted in lower electron mobilities and an increase in ambipolarity. The later part of the thesis debates on the relative contribution of electronic structure and aggregation (microstructures) in governing singlet fission (SF). Motivated by the recent SF model in carotenoid aggregates, a DPP-DPP based oligomer was synthesized by incorporating a vinylene bridge to imbue “polyene” character in the chromophore. Transient Spectroscopy (TA) measurements were carried out to monitor the formation of triplet states in the oligomer and to probe the occurrence of singlet fission. Although the oligomer exhibits “polyene” character like a typical “carotenoid aggregate”, it did not show singlet fission because of the additional stabilization of the singlet (S1) state which reduces the ∆EST. This study rationalized the importance of judicious control of band structures as well as microstructures to observe the SF phenomenon in this category of chromophores. The novel synthetic protocol provides the scope to tailor DPP-DPP based materials with desired effective conjugation lengths and side chains and can foreshow great prospects for future generation of organic electronics.

The thesis entitled "Pushing the Limits of NMR Sensitivity and Chiral Analysis: Design of New NMR Methods and Bio-molecular Tools" consists of six chapters. The research work reported in this thesis is focused on the development of novel chemical and NMR methodological approaches for enantiomeric analysis and mea- surement of residual dipolar couplings (RDCs), and the development of sensitivity enhanced slice selective NMR experiments for obtaining pure shift 1H spectra and the measurement of scalar couplings. The thesis is divided into two parts. The Part I comprises chapters 2-4, where the enantiomeric analysis is discussed, which includes newly developed chiral reagents, two new weak chiral aligning media and design of novel NMR techniques. Part II comprises chapters 5 and 6, which discusses new sensitivity enhanced slice selective NMR techniques. Chapter 1 gives a general introduction to NMR and the problems investigated in the remaining chapters of the thesis. The chapter starts with a brief discussion on the introduction, advancements and general applications of NMR, discussion is also given on the NMR approaches for enantiomeric analysis both in isotropic and anisotropic phases and the measurement of RDCs, including the benefits and limitations associated with each approach. The chapter sets the tone by discussing limitations of the existed NMR enantiomeric approaches and slice-selective techniques, and builds the bridge for the rest of the chapters by addressing these limitations. The chapter also introduces slice selective experiments, their benefits over other conventional methods and limitations. Additional introductory notes are also given on some related concepts. Part I : NMR Chiral analysis and RDCs measurements Chapter 2 discusses chiral sensing properties of RNA nucleosides and their utility as chiral derivatizing agents for the enantio-discrimination of 1o-amines using one dimensional 1H NMR. A three component protocol has been proposed for the complexation of nucleosides with amines, which is rapid, economical and provides maximum diastereomeric conversion. The chiral differentiating ability of nucleosides are examined for different amines based on the 1H NMR chemical shift differences between the diastereomers (∆δ R, S ). Enantiomeric differentiation has been observed at multiple chemically distinct proton sites. It is observed that adenosine and guanosine exhibit large chiral differentiation (∆δ R, S ) due to the presence of a purine ring. The comparison of the diastereomeric excess (de) measured by NMR with those of the gravimetrically prepared ratios are in excellent agreement with each other confirming the robustness of these RNA nucleosides in discriminating primary amines. Chapter 3 establishes the smooth connectivity with the chapter 2 by discussing the limitations of the enantiomeric discrimination using NMR in isotropic solutions. This chapter discusses two new water compatible aligning media that were developed based on self-assembling strategy of small bio-molecules. The self-assembled folic acid, and the binary mixture of 50-GMP and guanosine are introduced as two novel weak aligning media. The properties of these low ordered media have been systematically studied for their easy preparation, physical parameter dependent tunability of their degree of alignment, mesosphere sustainability over a broad range of temperature and the concentration of the ingredients, and the phase reproducibility. The applications of both these new media are demonstrated for chiral and pro-chiral discrimination and also for the measurement of RDCs. Both these liquid crystalline media could be tuned to very low degree of alignment (order parameter of the order of 10−4), which provides simple first order spectra of molecules aligned in them, the analysis provide order dependent NMR spectral parameters. The 50-GMP:guanosine orienting medium can be prepared in less than 1 hour, and has been demonstrated to be an ideal medium for the determination of RDCs that are used as restraints in the structure calculations of small molecules. Chapter 4 describes 1H NMR spectral complexity in isotropic and anisotropic phases and its consequences on enantiomeric analysis. In circumventing such problems, new NMR techniques have been developed and the spin dynamics involved in the designed sequences are discussed. The newly developed 2D 1H NMR experimental method termed as RES-TOCSY, and its applicability for resolving R and S enantiomeric or diastereomeric peaks of all the coupled proton spins in isotropic phase is discussed. The utility of the developed method is demonstrated in diverse situations, such as, for suppressing impurities peaks, resolving the severely overlapped peaks and unraveling the peaks masked due to severe line broadening when metal complexes are used as chiral auxiliaries. The advantages and limitations of the method over other methods available in the literature are discussed and the significant advantage of the present method is illustrated by spectral comparison with J-resolved experiment. The appli- cation of the method for the accurate measurement of enantiomeric excess has also been demonstrated. The chapter also introduces another NMR experimental technique developed for resolving enantiomeric peaks and complete unraveling of R and S spectra in anisotropic phase. The developed 2D NMR method is cited in the literature as CH-RES-TOCSY. In addition to spectroscopic visualization of R and S spectra, the method also yields C-H RDCs. The applicability of the new experiment has been demonstrated on a chosen example. The wide utility of the method has also been demonstrated for the assignment of symmetric cis- and trans- isomers. Part II : Sensitivity Enhancement of Slice selective NMR Experiments Chapter 5 describes applications of slice selective NMR experiments over conven tional NMR methods and their limitations as far as the sensitivity of signal detection is concerned, especially in low concentrated samples. The chapter introduces the implementation of Acceleration by Sharing Adjacent Polarization (ASAP) technique in slice selective experiments. It is convincingly demonstrated that ASAP helps in reducing inter scan relaxation delay and consequently permits acquisition of more number of scans in a given time, resulting in the gain in signal enhancement by a factor of two. The pulse sequences have been suitably designed for obtaining the pure shift 1H spectra and in G-SERF experiment for the measurement of 1H-1H couplings, both with significantly enhanced signal intensities. Chapter 6 describes new sensitivity enhanced slice selective NMR methods for mea- surement of scalar couplings. A new experiment has been developed which is named as Quick G-SERF (QG-SERF). It is a 1D NMR slice selective method developed based on real time spin manipulation technique. The method gives multiple scalar couplings of a selected spin with simplified multiplets, which is analogous to the 2D G-SERF but with considerable saving in instrument time by 1-2 orders of magnitude. The rapidness of the experiment arises due to reduced dimensionality. The spin dynamics involved in the pulse sequence and its working principle have been described. The application of the method is illustrated for the measurement of 1H-1H couplings. The sequence has been further improved to obtain the heteronuclear couplings between two abundant spins in an orchestrated manner and has been demonstrated for measurement of 1H-19F couplings. This sequence cited as HF-QG-SERF has been implemented on the molecules containing number of chemically non-equivalent fluorine atoms.

Crystal engineering is defined as “the understanding of intermolecular interactions in the context of crystal packing and in the utilisation of such understanding in the design of new solids with desired physical and chemical properties”. If crystals are the supramolecular equivalents of molecules, then crystal engineering is the supramolecular equivalent of organic synthesis. The subject considers both crystal structure analysis and design of new structures with targeted properties. The concept of “Supramolecular Synthons” was introduced by G. R. Desiraju in this context, for the rational design of structures. Supramolecular synthons are the smallest reducible structural units that contain geometrical and chemical information required for recognition between functional groups in molecular solids. Crystal engineering has grown very fast after the introduction of this idea in 1995 and engineered solids were found to be useful for application in many diverse fields, from structural chemistry to drug design. Because of the great significance of supramolecular synthons, their identification and analysis in terms of crystallographic, spectroscopic, and computational methods is essential. Single crystal X-ray diffraction (SCXRD) is a widely used technique for the identification of synthon structure. But the technique has its own limitations like requirement of good quality, suitably sized single crystals, longer times associated with the process which further restricts high throughput analysis. Practically, there is no other way for identification of synthons on a regular basis. In this situation a simple, accurate, and fast method will be of significance; not only for basic studies, but also to scan different solid state phases in pharmaceutical industries. Due to this reason, I have studied IR spectroscopy to find marker bands for different synthons in the first part of the thesis. In chapter 2, I have analyzed a variety of C–H···X based weak synthons. For identification of each synthon, two sets of compounds were taken. In one set the synthon exists and in the other set it does not. Comparison and verification of IR characteristics helps to establish marker bands. Such markers are used to get information on synthon patterns in compounds with unknown crystal structures. The next challenge is whether or not such an IR method can distinguish different geometries of a same interaction. To address this question, different geometries of NO2···I halogen bonded synthons are investigated in chapter 3. This synthon exists in three geometries P, Q and R based on angular and distance criteria. The identification process is divided into five steps. The first step identifies IR signatures from very similar compounds, but with different topologies. The second step verifies earlier features and establishes IR marker bands. In the next step a graded IR protocol is formulated for stepwise discrimination of unknown systems. Such a graded method is applied for clarification of synthon ambiguities and in the identification of synthons in new compounds. Till now synthon information from crystal structures is used as a basis for IR study. Spectroscopy provides chemical information on intermolecular interactions. Is it possible to use such chemical information for crystal engineering? Chapter 4 deals with this aspect. Here, IR investigation is performed on the acid···amide heterodimer synthon. The initial analysis shows contradictory outcomes for synthon formation. According to IR, the N–H···O interaction is significantly destabilized in this synthon. Why then does the acid···amide synthon form? It is found that the answer lies in the higher stability of the other interaction, O–H···O, in the synthon. In other words, dimer formation will be preferred when the O‒H···O interaction is favoured. This is possible when the acidity of H-atom and the basicity of carbonyl O-atom is high. Based on this, a combinatorial study is performed varying the chemical nature of molecules, electron donating or withdrawing. Four quadrants are generated with different combinations of the molecular nature. The result of the combinatorial study shows different acid–amide oriented synthon preferences from different quadrants. A combination of all the observed synthons creates a structural landscape for the acid–amide system. A particular synthon associated with a specific quadrant is found to be responsible for the mechanical property of the synthesized cocrystals. Analysis on the structural aspects of mechanical properties allows for the formulation of models for property engineering. Can it be possible to use these models for targeted property design, other than serendipitous results? Crystal engineering is associated with three aspects, structure analysis, structure design and property engineering. Structure analysis is the first step in any crystal engineering exercise. It also explains the way by which the subject was started in the early days to correlate structure with property. This is the first phase or generation of crystal engineering. The second generation considers rational design of crystal structure which is facilitated by the concept of the supramolecular synthon. This phase has seen in the incorporation of different synthon based strategies to build a variety of supramolecular architectures. However, there is no prediction of a property which is the ultimate aim of crystal engineering. If one can achieve a desired property by predesign, then crystal engineering will see the final and higher stage which is termed third generation crystal engineering in chapter 5. The second part of the thesis discusses work is this direction, where mechanical properties are targeted and achieved by design using models from previous work. Chapter 6 discusses the engineering of elastic crystals from initial brittle precursors. A capping based model is proposed and used to prepare systems that can adopt the desired structure type. Among many other requirements, the crystals need some structurally buffering regions to show elasticity. Type-II electrostatic halogen bonds are used to construct such buffering regions. When the crystals are obtained according to the model type, they show reversible elastic deformation. σ-Hole based halogen bonds are crucial to the synthesis. But, during the project some adverse effects were noticed/realized for the use of halogen bonds. This suggests the need for an alternative methodology. A synthon that can mimic both the geometrical and chemical nature of σ-hole based halogen bonds would be useful to replace the earlier one. A search in this respect results in π-hole oriented orthogonal synthons based on C=O···C=O and NO2···NO2 interactions. A stepwise replacement procedure is applied to see and carry forward structural modularity in the new systems. Cocrystal systems are chosen for easy replacement by changing the constituents. Halogen bonds in cocrystals of the first step are partially substituted by a π-hole mimicking synthon in the second step and completely substituted in the third step. All the structures in the different steps are found to retain the same property, namely elasticity, although they possess dissimilar synthons. These aspects are discussed in chapter 7. Chapter 8 deals with the design of hand twistable helical crystals which are known to result during natural growth. Helical shape crystals are highly impactful for application in metamaterials and lithographic techniques, but at the same time occurrence of such morphology is unpredictable. Such shape generates from the periodic bending of crystals and thus needs multiple deformation directions. Here, a multistep crystal engineering procedure is adopted to get two directionally (2D) plastically bendable crystals, starting from one directional (1D) plastic crystals. Halogen bonds again play a major role in the design. The route follows the order 1D plastic crystals → 1D elastic crystals → 2D elastic crystals → 2D plastic crystals. These 2D plastic crystals are used to obtain hand-twisted helical crystals. Here, different properties namely elastic and plastic are seen in identically structured compounds. Once again, problems in using halogens are noticed. To address the issue of halogens, chapter 9 uses halogen bond/hydrogen bond equivalence to replace halogen bonds by geometrically and chemically similar hydrogen bonds. However, the first designed molecule in this respect did not result in the desired structure. The obligations are removed by applying the molecular/supramolecular equivalence strategy on the earlier molecule. Such an attempt gives another completely hydrogen bonded system that can now adopt the model structure and show a similar 2D plasticity. Crystals of this compound are also hand twistable. Third generation crystal engineering needs predesign models for targeted property engineering. In this context some differently structured elastic crystals are compared with common brittle crystals to identify and ascertain the structural requirements. This analysis helps in constructing different models for future engineering of elastic crystals. It also tabulates the structural and interaction differences in obtaining different mechanical properties namely shearing, plastic, elastic and brittle. In summary, these two major aspects for doing crystal engineering are highlighted in my thesis. One is the identification of robust synthons and the other is the use of synthon based structure design for property engineering. The first part of the thesis discusses the IR spectroscopic method for identification of synthons and then uses the spectral information for crystal structure engineering. The second part is related to deliberate crystal property engineering and uses structure-property relationships from the previous chapters and the literature to formulate predesign models and strategy. Achieving crystal properties in this way is expected to initiate the fast progress of the third generation crystal engineering.

The thesis presents detailed results of theoretical analyses based on extensive computer simulation studies with an aim to explore, quantify whenever possible, and understand structure and dynamics of polymers and proteins in several complex solvents. In order to make the Thesis coherent, we also study certain aspects of binary mixtures. Based on the phenomena studied, the thesis has been divided into four major parts: I. Dynamics of biological water: Distance dependent variation of dielectric constants in aqueous protein solutions II. Temperature dependent study of structural transformations in aqueous binary mixtures III. Conformation and dynamics of polymers in solution: Role of aqueous binary mixtures IV. Conformational change and unfolding dynamics of proteins: Role of sol-vent environment The above mentioned four parts have further been divided into thirteen chapters. In the following we provide a brief chapter-wise outline of the thesis. Part I consists of two chapters, where we focus on the study of dynamics of biological water and distance dependent variation of static and dynamic proper-ties (including dielectric constant) of water near different proteins. To start with, chapter 1 provides an introduction to the structure and dynamics of biological water. Here we discuss different experimental studies; including dielectric relaxation, NMR and salvation dynamics those explore the bimolecular hydration dynamics in great detail. We also discuss the wide range of computer simulation and theoretical studies that have been carried out to understand the dynamical behaviour of biological water. In chapter 2, we present our molecular dynamics simulation study to ex-plore the distance dependent static and dynamic behaviour of biological water near four different protein surfaces. Proteins are known to have large permanent dipole moments that can influence structure and dynamics of even distant water molecules. Therefore, distance dependence of polarization punctuation can provide important insight into the nature of biological water. We explore these aspects by studying aqueous solutions of four different proteins of different char-acteristics and varying sizes. We find that the calculated dielectric constants of the systems show a noticeable increment in all the cases compared to that of neat water. Total dipole moment auto time correlation function of water is found to be sensitive to the nature of the protein. We also define and calculate the effective dielectric constant of successive layers and find that the layer adjacent to protein always has significantly lower value (∼ 50). However, progressive layers exhibit successive increment of dielectric constant, finally reaching a value close to that of bulk 4–5 layers away. Theoretical analysis providing simple method for calculation of shellwise local dielectric constant and implication of these findings are elaborately discussed in this chapter. Part II deals with the temperature dependent study of aqueous DMSO and ethanol solutions and consists of three chapters. Chapter 3 provides a general introduction to the non-ideality (deviation from Raoult’s law) encountered in different binary mixtures. We discuss different theoretical models for treatment of binary mixtures. Finally we provide a systematic study about the non-ideality observed in aqueous binary mixtures. Here we discuss the anomalies observed in such systems and carry out a brief survey on the existing ideas of structural transformations associated with the solvation of a foreign molecule in water. In chapter 4, we discuss the results of temperature dependent study of struc-tural and dynamic properties of aqueous dimethyl sulfoxide (DMSO) mixture. It is now well-known that aqueous DMSO mixture exhibits signature of perco-lation driven structural aggregation at a mole fraction range xDMSO ≈ 0.15. We study the structural and dynamical change in this binary mixture below and above the percolation threshold along with decreasing temperature. Significant change in the molecular structure of DMSO as well as that of water is observed above the percolation threshold at a lower temperature, particularly at 200K. The structural arrangement of the DMSO molecules is found to be progressively more ordered with increasing DMSO concentration and decreasing temperature. On the other hand, water structure is found to be significantly deviated from tetrahedral arrangement in presence of DMSO clusters even at low temperature. The dynamics of water is also found to be considerably affected with increase of concentration and lowering of temperature. Similar phenomenon is observed for another amphiphilic molecule, ethanol, and has been discussed in chapter 5. Aqueous ethanol mixture is a widely studied solvent, both experimentally and using computer simulations. All the studies indicate several distinct salvation regimes. In recent molecular dynamics simulation studies, the reason for formation of micro-aggregates of ethanol is again attributed to percolation driven structural transformation. We carry out a temperature dependent study of water-ethanol binary mixture, particularly at low ethanol concentration to understand the molecular origin of such structural transformation. We find that the structural arrangement of ethanol as well as water molecules is similarly affected as that of DMSO with lowering of temperature. However, dynamics of water molecules in aqueous ethanol solution is found to be marginally affected, unlike the case of aqueous DMSO solution. We discuss the microscopic reason for such behaviour in a detailed manner. In Part III, we discuss the dynamics of linear polymer chains in different aqueous binary mixtures. Here we have three chapters. In chapter 6, we carry out a brief survey of the existing theories of polymers in solution. We discuss the quality of solvents depending on the preferred interactions between the polymer and the solvent or the polymer with its own. We also discuss the celebrated Flory-Huggins theory. We derive the expression of free energy of the Flory-Huggins theory in terms of the volume fraction of monomer and solvent molecules. In chapter 7, we discuss the results of our study of polymer dynamics in aqueous DMSO solution. We find that at a mole fraction 0.05 of DMSO (xDMSO ≈ 0.05) in aqueous solution, a linear polymer chain of intermediate length (n=30) adopts collapsed conformation as the most stable conformational state. The same chain exhibits an intermittent oscillation between the collapsed and the extended coiled conformations in neat water. Even when the mole fraction of DMSO in the bulk is 0.05, the concentration of the same in the first hydration layer around the polymer is found to be as large as 17 %. Formation of such hydrophobic environment around the hydrocarbon chain may be viewed as the reason for the collapsed conformation gaining additional stability. We find a second anomalous behaviour to emerge near xDMSO ≈ 0.15 that is attributed to the percolation driven structural aggregation of DMSO that lowers the relative concentration of the DMSO molecules in the hydration layer. In chapter 8, we carry out similar study of linear polymer chain in water– ethanol binary mixture. In this case also, we find a sudden collapse of the poly-merat xEtOH ≈ 0.05. Since ethanol molecules are known to form micro-aggregates in this concentration range, stability of collapsed state of polymer at this con-centration is anticipated to be correlated to this phenomenon. In fact, a purely hydrophobic polymer chain, in its collapsed form is anticipated to assist in the formation of spanning cluster comprised of hydrophobic ethyl groups at this concentration range thereby facilitating the percolation transition. We discuss these prospects in this chapter. Part IV deals with the solvent sensitivity to the conformational change and unfolding dynamics of protein. Part IV consists of five chapters. In chapter 9, we develop an understanding of protein folding and unfolding dynamics by discussing the fundamental theories developed in the last few decades. We also discuss the major role of solvents in stabilizing or destabilizing the native, ordered state. In chapter 10, we present a detailed study of unfolding of a small protein, chicken villin headpiece (HP36) in water-ethanol binary mixture, using molecular dynamics simulations. The prime objective of this work is to explore the sensitivity of protein dynamics towards increasing concentration of the cosolvent and unravel essential features of intermediates formed in the unfolding path-way. In water–ethanol binary mixtures, HP36 is found to unfold partially, under ambient conditions, that otherwise requires temperature as high as ∼ 600K to denature in pure aqueous solvent. The study unravels certain interesting aspects about the pathway of unfolding, guided by the formation of unique intermediates. Unfolding is initiated by the separation of hydrophoic core comprising three phenylalanine residues (Phe7, Phe11, Phe18). This separation initiates the melting of the helix2 of the protein. However, with an increase of cosolvent concentration different partially unfolded intermediates are found to be formed. We attribute the emergence of such partially unfolded states to the preferential solvation of hydrophobic residues by the ethyl groups of ethanol. We explore and subsequently quantify the detailed dynamics of unfolding in water-ethanol that appear to be more complex and sensitive to solvent composition. With an aim to develop a general understanding of the role of water–ethanol binary mixture in facilitating anomalous conformational dynamics of proteins, we carry out combined theoretical and experimental studies to explore detailed structural change of a larger protein, Myoglobin with increasing ethanol concentration. These studies are described in chapter 11. In agreement with our pre-vious observations, we identify in this case two well-defined structural regimes, one at xEtOH ≈ 0.05 and the other at xEtOH ≈ 0.25, characterized by formation of distinct partially folded conformations and separated by a unique partially unfolded intermediate state at xEtOH ≈ 0.15. We also find non-monotonic com-position dependence of (i) radius of gyration (ii) long range contact order (iii) residue specific solvent accessible surface area of tryptophan (iv) circular dichro-ism spectra and UV-absorption peaks. Multiple structural transformations, well-known in water-ethanol binary mixture, appear to have considerably stronger effects on the conformation and dynamics of protein Myoglobin. In chapter 12, we explore the free energy surface of unfolding pathway through umbrella sampling, for the small globular alpha-helical protein chicken-villin headpiece (HP36) in three different solvent conditions (water, xDMSO ≈ 0.15 and xDMSO ≈ 0.3). Recently established as a facilitator of helix melting, DMSO is found to be a good denaturant for HP36 and at a mole fraction of xDMSO ≈ 0.3, complete melting of the protein is ensured. The unfolding proceeds through initial separation or melting of the same aggregated hydrophobic core that com-prises three phenylalanine residues (Phe7, Phe11 and Phe18) accompanied by simultaneous melting of the helix2. Unfolding is found to be a multistage process involving crossing of three consecutive minima and two barriers at the initial stage. At a molecular level, Phe18 is observed to reorient itself towards other hy-drophobic grooves to stabilize the intermediate states. We identify the configuration of intermediates in all the solvent conditions which are found to be unique for the corresponding minima with similar structural arrangement. Consider-able softening of the barriers is observed with increasing DMSO concentration. Higher concentration of DMSO tunes the unfolding pathway by destabilizing the third minimum and stabilizing the second one, indicating the development of solvent modified, less rugged pathway. Chapter 13 provides a detailed microscopic mechanism of DMSO induced unfolding of HP36. We analyze the free energy contours of the protein HP36, obtained from molecular dynamics simulation in xDMSO ≈ 0.15 and xDMSO ≈ 0.3. The most probable intermediates obtained from the free energy contours are found to be similar to those obtained from umbrella sampling which again sup-ports the fact that the melting proceeds through formation of a series of unique intermediates. We characterize the preferential hydrophobic salvation of the hydrophobic core that drives the melting of secondary structure, by calculating time dependent radial distribution function and identifying the formation of strong orientation order between methyl groups of DMSO and phenyl alanine residues. Finally we employ Kramer’s rate equation to calculate the rate of bar-rier crossing that reveals significantly faster rate of unfolding with increasing DMSO concentration that is in agreement with simulation results. Whenever possible, we have discussed the scope of future work at the end of each chapter.

High dielectric constant materials have tremendous impact on miniaturization of devices that are used in various applications like wireless communication systems, microelectronics, global positioning systems, etc. To store electric charge in a very small space necessarily needs a capacitor with very high dielectric constant. Thus, these materials are very important in fabricating capacitors, or metal oxide semiconductor filed effect transistor (MOSFET). Among the existing commercially available devices, silicon-based microelectronic devices are commonly used based on the moderately stable dielectric constants of silicon with low losses and minimal temperature and frequency dependence. However, now-a-days, the perovskite based transition metal oxides have drawn attention that have the ability to fulfill all the requirements for being a good dielectric material in all the industrial applications. In this thesis we have studied a few selected perovskite based transition metal oxide systems in terms of their dielectric and magnetic behaviour. In Chapter 1, we have have given brief introductions about the some application of dielectric materials and the origin of dielectric and magnetic properties in the materials. We have also discussed about the polarisation in the dielectric materials to understand it’s frequency dependence and also to formalise different relaxation behaviour with the help of physical and mathematical explanation. In Chapter 2, we describe the various methodologies adopted in this thesis. In Chapter 3, we have studied the dielectric behaviour of Nd2NiMnO6, a rare earth based double perovskite ferromagnetic insulator. We successfully synthesised and characterised the compounds, settled the valency issues with the help of temperature dependent XAS of the transition metal atom in contrast to the existing controversy available in literature. We have found that this material shows relaxor kind behaviour with a colossal dielectric constant value. We have studied in details the origin of the colossal dielectric constant and the relaxation behaviour along with the a.c and d.c. transport properties. We have shown the origin of the ferromagnetism (TC ∼ 200 K) with a low temperature antiferromagnetic ordering (TN ∼ 55 K) with the help of detailed studies of temperature dependent d.c., a.c. magnetism and their XMCD. We have also investigated the isothermal variation of magnetodielectric and magnetoresistance behaviour as a function of magnetic field and their origin. In Chapter 4,we study the effect of cation anti-site disorder on the magnetic, dielectric and transport properties of another rare earth based ferromagnetic double perovskite insulator La2NiMnO6 by controlling different extent of anti-site disordered. We have confirmed the valency of the transition metal cations using XAS technique and followed by shown, different types of magnetic interaction between the transition metal cations using d.c magnetic, quantitative XMCD analysis and the origin of large dielectric response, a.c. transport & dielectric relaxation using temperature variation dielectric measurement as an experimental evidence in contrast of our previous speculation published in literature. We further have studied, the coupling between the magnetic and electric spin through isothermal magnetodielectric measurement. In Chapter 5, we have successfully synthesised and characterised a solid solution of YMnxIn1−xO3 series via different mol % of In doping in the multiferroic YMnO3 system. YMnO3 is a well known multiferroic material studied rigorously during past few decades. We have seen, YMnO3 which has a antiferromagnetic ordering temperature of ∼ 75 K suppressed with increasing the dopant concentration In. We have figured out the effect of In doping in the suppression of multiferroic phase and extended it to the dielectric properties. We have found that, the temperature dependence of dielectric constant shows an anomaly at the magnetic ordering temperature and studied magnetodielectric coupling. We have also investigated the temperature variation of dielectric relaxation and a.c. transport behaviour as a function of composition. In Chapter 6, we have identified the phase seperation and proposed a phase diagram as function of Gd doping in the Ho2−xGdxCuTiO6 double perovskite, where two end member, namely Ho2CuTiO6 and Gd2CuTiO6 are found to be in two different crystallographic phase as, hexagonal (P63cm) and orthorhombic (Pnmm), respectively. We have characterised the valency of the transition metal cations using XAS.We have seen very less temperature and frequency dependence of dielectric constant in hexagonal phase in compare to the orthorhombic phase and tried to figuring out from experimental analysis by performing temperature dependence dielectric const measurement. We also have shown the effect of doping in the origin of dielectric relaxation, a.c transport and magnetic behaviour of this system. In Chapter 7, we have synthesised and characterised successfully two different rare earth based layered perovskite La3Cu2VO9 and La4Cu3MoO12 compounds are of centrosymmetric space group. We have figured it of the valency of the different atoms present in the compound using XAS. We also do have observed the good temperature stability of dielectric constant of these materials and explored origin of mechanism in the dielectric relaxation, a.c. transport property by performing the temperature dependance dielectric measurement. The magnetic structure also have shown with the help of d.d. magnetic measurements. In Appendix A, we have seen the very stable dielectric constant constant from very low to above room temperature of the 2D nano PbS. The frequency stability of dielectric constant is also remarkable in compare to bulk PbS values available in literature. We have explored the origin of the conductivity and relaxation mechanism performing dielectric constant measurement. In conclusion, we investigate, in this thesis, dielectric properties of different transition metal oxides system and the mechanism of dielectric relaxation, a.c, d.c transport and their origin of magnetic response.

Extensive research work was carried out in past few decades to synthesize new compounds with extended structures by employing various organic linkers and metals. A large number of potential applications of these coordination polymer materials were explored as it contains both inorganic metals as well as organic molecules. The large open pores of coordination polymer compounds were explored for applications such as absorption, separation, and catalysis etc. whereas the framework part provides a model system to study physical properties such as magnetism, luminescence, ferroelectricity etc. We were mainly interested in designing new magnetic materials with extended structures which is the primary objective of this thesis. To study this a systematic investigations are carried out with azide bridged copper(II) compounds. Azide is a versatile ligand which possesses a large number of bridging modes. On the other hand, the coordination flexibility offered by the copper centres makes it to possess diverse coordination number (4-6) as well as geometry. Copper-azide compounds were synthesized at room temperature and the structure was determined using single-crystal X-ray diffraction studies. Structure and magnetic behavior of the copper-azide compounds were studied and discussed here in this thesis. Further, we have studied selective absorption and separation of aliphatic nitrile compounds by employing a two-dimensional interdigitated coordination polymer. In addition, transformation studies of a Ni5 cluster to a Ni9 cluster have also been carried out. Chapter 1 of this thesis presents a brief overview of azide based compounds and summarizes important copper-azide compounds and their magnetic behavior. In chapter 2, synthesis, structure, and magnetic behavior of two-dimensional copper-azide based compounds have been presented. Field dependent magnetic studies were also carried out for all the compounds. Chapter 3 presents the synthesis, structure, and magnetic behavior of copper-azide compounds where 1,2-diaminopropane was employed as a site blocking agent. In chapter 4, the synthesis, structure, and magnetic behavior of two isostructural three-dimensional copper-azides are presented. In chapter 5, synthesis, structure, and magnetic behavior of the azide based one and two-dimensional compounds are presented. Chapter 6 presents synthesis and structure of a two-dimensional inter-digitated coordination polymer compounds. The selective absorption and separation of aliphatic nitriles were also presented in this chapter. In chapter 7, synthesis, structure, and magnetic behavior of Ni clusters are presented. A transformation study to convert a Ni5 cluster to Ni9 cluster was also carried out and presented in this chapter.

The metal-organic framework (MOF) compounds have witnessed rapid growth in the past decade and currently emerged as a highly unique area in the field of chemistry, materials science, and multiple branches of engineering. It presents applications in diverse fields such as gas sorption, catalysis, ionic conductivity, sensing etc. These compounds are built by the inorganic metal ions which are bridged by organic linkers to form extended structures. These compounds are mainly synthesized by either one-pot synthesis or in a sequential manner. In the former case, the inorganic metal ions and the respective organic linker are reacted together in a particular solvent or solvent mixture, whereas in the later case, a metalloligand is prepared by using the organic linker and the primary metal ion, which react with the secondary metal ion forming the desired structure. In this thesis, the synthesis of metal-organic framework compounds by one-pot synthesis as well as the sequential synthesis is presented. The structures of all the synthesized compounds have been determined by single crystal X-ray diffraction technique. The prepared compounds were employed in the study of sensing of nitroaromatic compounds, toxic metal ions and highly oxidizing anions. In addition, detailed studies of heterogeneous catalysis employing the prepared MOFs were investigated along with catalysis by metal nanoparticle incorporated within MOFs. In select cases, the labile nature of the lattice water molecules was established by performing in-situ single crystal to single crystal (SCSC) structural transformation studies. In addition, the proton conductivity and the magnetic behavior have also been studied. Chapter 1 of the thesis presents a brief overview on metal-organic framework compounds and summarizes its various important properties. In chapter 2, the synthesis, structure, and characterization of heterometallic metal-organic framework compounds using 2-mercaptonicotinic (H2mna) and Cu(I) / Ag(I) based two metalloligands, [Cu6(Hmna)6] and [Ag6(Hmna)2(mna)4](NH4)4 are presented. In chapter 3, we present the synthesis, structure and nitroaromatic sensing behavior of [Ag6(mna)6](NH4)6 metalloligand based heterometallic metal-organic framework compounds. In chapter 4, the synthesis, structure and Lewis acid catalytic behavior of 6-mercaptonicotinic acid based heterometallic metal-organic framework compounds are presented. In chapter 5, the stabilization of the palladium nanoparticles in the newly synthesized 1,10-phenanthroline based metal-organic framework compounds and their catalytic behavior is presented. In chapter 6, we present the synthesis, structure and the sensing behavior of hazardous chemicals such as toxic metal ions and highly oxidizing anions. In addition, the adsorption and desorption of synthetic dye molecules by the metal-organic framework compounds are also presented.

Electronic and optical properties of semiconducting nanocrystals, that can be engineered and manipulated by various ways like varying size, shape, composition, structure, has been a subject of intense research for more than last two decades. The size dependency of these properties in semiconductor nanocrystals is direct manifestation of the quantum confinement effect. Study of electronic and optical properties in smaller dimensions provides a platform to understand the evolution of fundamental bulk properties in the semiconductors, often leading to realization and exploration of entirely new and novel properties. Not only of fundamental interests, the semiconductor nanocrystals are also shown to have great technological implications in diverse areas. Besides size tunable properties, introduction of impurities, like transition metal ions, gives rise to new functionalities in the semicon-ductor nanocrystals. These materials, termed as doped semiconductor nanocrystals, have been the subject of great interest, mainly due to the their interesting optical properties. Among different transition metal doped semiconductor nanocrystals, manganese doped systems have drawn a lot on attention due to their certain advantages over other dopants. One of the major advantages of Mn doped semiconductor nanocrystals is that they do not suffer from the problem of self-absorption of emission, which quite often, is consid-ered detrimental in their undoped counterparts. The doped nanocrystals are known to produce a characteristic yellow-orange emission upon photoexcitation of the host that is relatively insensitive to the surface degradation of the host. This emission, originating from an atomic d-d transition of Mn2+ ions, has been a subject of extensive research in the recent past. In spite of the spin forbidden nature of the specific d-d transition, namely 6A1 −4 T1, these doped nanocrystals yield intense phosphorescence. However, one major drawback of utilizing this system for a wide range application has been the substantial inability of the community to tune the emission color of Mn-doped systems in spite of an intense effort over the years; the relative constancy of the emission color in these systems has been attributed to the essentially atomic nature of the optical transition involving localized Mn d levels. Interestingly, however, the Mn emission has a very broad spectral line-width in spite of its atomic-like origin. While the long (∼ 1 ms) emission life-time of the de-excitation process is well-studied and understood in terms of the spin and orbitally forbidden nature of the transition, there is little known concerning the process of energy transfer to the Mn from the host in the excitation step. In this thesis, we have studied the ultrafast dynamic processes involved in Mn emission and addressed the issues related to its tunability and spectral purity. Chapter 1 provides a brief introduction to the fundamental concepts relevant to the studies carried out in the subsequent chapters of this thesis. This chapter is started with a small preview of the nanomaterials in general, followed by a discussion on semiconducting nanomaterials, evolution of their electronic structure with dimensions and size as well as the effect of quantum confinement on their optical properties. As all the semiconducting nanomaterials studied in the thesis are synthesized via colloidal synthesis routes, a separate section is devoted on colloidal semiconducting nanomaterials, describing various ways of modifying or tuning their optical properties. This is followed by an introduction to the important class of materials “doped semiconductor nanocrystals”. With a general overview and brief history of these materials, we proceed to discuss about various aspects of manganese doped semiconductor nanocrystals in great details, highlighting the origin of the manganese emission and the associated carrier dynamics as well as different reported synthetic strategies to prepare these materials. The chapter is closed with the open questions related to manganese doped semiconductor nanocrystals and the scope of the present work. Chapter 2 describes different experimental and theoretical methods that have been employed to carry out different studies presented in the thesis. It includes common experimental techniques like UV-Vis absorption spectroscopy, steady-state and time-resolved photoluminescence spectroscopy used for optical measurements, X-ray diffraction, trans-mission electron microscopy and atomic absorption spectroscopy used for structural and elemental analysis. Experimental tools to perform special studies like transient absorption and single nanocrystal spectroscopy are also discussed. Finally, theoretical fitting method used to analyse various spectral data has been discussed briefly. Chapter 3 deals with the dynamic processes involved in the photoexcitation and emission in manganese doped semiconductor nanocrystals. For this study, Mn doped ZnCdS alloyed nanocrystal has been chosen as a model system. There are various radiative and nonrdiative recombination pathways of the photogenerated carriers and they often compete with each other. We have studied the dynamics of all possible pathways of carrier relaxation, viz. excitonic recombination, surface state emission and Mn d-d transition. The main highlight of this chapter is the determination of the time-scale to populate surface states and the Mn d-states after the photoexcitation of the host. Employing femtosecond pump-probe based transient absorption study we have shown that the Mn dopant states are populated within sub-picosecond of the host excitation, while it takes a few picoseconds to populate the surface states. Keeping in mind the typical life-time of the excitonic emission (∼ a few ns), the ultra-fast process of energy transfer from the host to the Mn ions explains why the presence of Mn dopant ions quenches the excitonic as well as the surface state emissions so efficiently. Chapter 4 presents a study of manganese emission in ZnS nanocrystals of different sizes. By varying the size of the ZnS host nanocrystal, we show that one can tune the Mn emission over a limited range. In particular, with a decrease in host size, the Mn emission has been observed to red-shift. We have attributed this shift in Mn emission to the change in the ratio of surface to bulk dopant ions with the variation of the host size, noting that the strength of the ligand field at the Mn site should depend on the position of the Mn ion relative to the surface due to a systematic lattice relaxation in such nanocrystals. The ligand field affects the emission wavelength directly by controlling the splitting of the t2 and e levels of Mn2+ ions. The surface dopant ions experience a strong ligand field due to distorted tetrahedral environment which leads to larger splitting of these t2 and e states. We further corroborated these results by performing doping concentration dependent emission and life-time studies. In Chapter 5 addresses two fundamental challenges related to manganese photolumines-cence, namely the lack of a substantial emission tunability and presence of a very broad spectral width (∼ 180-270 meV). The large spectral width is incompatible with atomic-like manganese 4T1 −6 A1 transition. On the other hand, if this emission is atomic in nature, it should be relatively unaffected by the nature of the host, though it can be manipulated to some extent as discussed in Chapter 3. The lack of Mn emission tunability and spectral purity together seriously limit the usefulness of Mn doped semiconductor nanocrystals. To understand why the Mn emission tunability range is very limited (typically 565-630 nm) and to understand the true nature of this emission, we carried out single nanocrystal imaging and spectroscopy on Mn doped ZnCdS alloyed nanocrystals. This study reveals that Mn emission, in fact, can vary over a much wider range (∼ 370 meV) and exhibits widths substantially lower (∼ 60-75 meV) than reported so far. We explained the occur-rence of Mn emission in this broad spectral range in terms of the possibility of a large number of symmetry inequivalent sites resulting from random substitution of Cd and Zn ions that leads to differing extent of ligand field contributions towards the splitting of Mn d-levels. The broad Mn emission observed in ensemble-averaged measurements is the result of contribution from Mn ions at different sites of varying ligand field strengths inside the NC. Chapter 6 presents a synthetic strategy to strain-engineer a nanocrystal host lattice for a controlled tuning of the ligand field effect of the doped Mn sites. It is realized synthesizing a strained quantum dot system with the structure ZnSe/CdSe/ZnSe. A larger lattice parameter of CdSe compared to that of ZnSe causes a strain field that is maximum near the interface, gradually decreasing towards the surface. We control the positioning of Mn dopant ions at different distances from the interface, thereby doping Mn at different predetermined strain fields. With the help of this strain engineering, we are able to tune Mn emission across the entire range of the visible spectrum. This strain induced tuning of Mn emission is accompanied by life-times that is dependent on the emission energy which has been explained in terms of perturbation effect on the Mn center due to the strain generated inside the quantum dot. The spectacular emission tuning has been explained by modelling the quantum dot system as an elastic continuum containing three distinct layers under hydrostatic pressure. From this modelling, we found that the strain is max-imum at the interface and decreases continuously as one goes away from the interface. We also show that the Mn emission maximum red shifts with increasing distance of the dopants from the maximum strained region. In summary, we have performed a study on the photophysical processes in manganese doped semiconductor nanocrystals. We have emphasized in understanding of different dynamic processes associated with the manganese emission and tried to understand the true nature of manganese emission in a nanocrystal. This study has brought out some new aspects of manganese emission and opened up possibilities to tune and control manganese emission by proper design of the host material.

The research work reported in this thesis is focused on the chiral analysis, quantification of enantiomeric composition, assignment of absolute configuration of molecules with chosen functional groups. The weak intra-molecular hydrogen bonding interactions are detected by exploiting several multinuclear and multi-dimensional techniques. Pulse sequences have been designed to manipulate the spin dynamics to derive specific information from the complex NMR spectra encountered in diverse situations. Broadly, the thesis can be classified in to three sections. The section I containing two chapters reports the introduction of new chiral auxiliaries and protocols developed for enantiomeric discrimination, measurement of enantiomeric contents, assignment of absolute configuration for molecules possessing specific functional groups using chiral solvating and derivatizing agents. The section II, reports NMR experimental evidence for the observation of the rare type of intramolecular hydrogen bonds involving organic fluorine in biologically important organic molecules, that are corroborated by extensive DFT based theoretical calculations. The section II also discusses the H/D exchange mechanism as a tool for quantification of HB strengths in organic building blocks. The section III reports the two different novel NMR methodologies designed for deriving information on the scalar interaction strengths in an orchestrated manner. The designed sequences are able to completely eradicate the axial peaks, prevents the evolution of unwanted couplings and also yields ultrahigh resolution in the direct dimension, permitting the accurate measurement of scalar couplings for a particular spin. The brief summary about each chapter is given below. Chapter 1 provides a general introduction to one and two dimensional NMR spectroscopy. The pedagogical approach has been followed to discuss the conceptual understanding of spin physics and the NMR spectral parameters. The basic introduction to chirality, existing approaches in the literature for discrimination of enantiomers and the assignment of absolute configuration of molecules with chosen functional groups and their limitations are briefly discussed. The brief introduction to hydrogen bond, experimental methods to obtain the qualitative information about the strengths of hydrogen bonds, and the theoretical approaches employed in the thesis to corroborate the NMR experimental findings have been provided. The mechanism of H/D exchange, the utilization of exchange rates to derive strengths of intra-molecular hydrogen bond in small molecules have also been discussed. This chapter builds the bridge for the rest of the chapters. Each of these topics are discussed at length in the corresponding chapters. Part I: NMR Chiral Analysis: Novel Protocols Chapter 2 discusses a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, amino alcohols. The protocol involves the in-situ formation of chiral ammonium borate salt from a mixture of C2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept has been convincingly demonstrated for the visualization of enantiomers of a large number of chiral and pro-chiral amines and amino alcohols. The protocol also permits the precise measurement of enantiomeric composition. The significant advantage of the protocol is that it can be performed directly in the NMR tube, without any physical purification. The structure of the borate complex responsible for the enantiodifferentiation of amines has also been established by employing multinuclear NMR techniques and DFT calculations. From DOSY and 11B NMR experiments it has been ascertained that there are only two possible complexes or entities which are responsible for differentiating enantiomers. From the combined utility of DFT calculations and the 11B NMR chemical shifts, the structure of the borate complex has been determined to be an amine-coordinated complex with the N atom of the amine. Chapter 3 discusses a simple chiral derivatizing protocol involving the coupling of 2-formylphenylboronic acid and an optically pure [1,1-binaphthalene]-2,2-diamine for the rapid and accurate determination of the enantiopurity of hydroxy acids and their derivatives, possessing one or two optically active centres. It is established that this protocol is not only rapid method for discrimination of enantiomers but also highly effective for assigning the absolute configuration of various chiral hydroxy acids and their derivatives. The developed protocol involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and 2-formylphenylboronic acid with (S)-[1,1-binaphthalene]-2,2-diamine as chiral derivatizing agents. The absence of aliphatic peaks from the derivatizing agent, large chemical shift separation between the discriminated peaks of diastereomers, and the systematic change in the direction of displacement of peaks for an enantiomer in a particular diastereomeric complex, permitted the unambiguous assignment of absolute configuration. Part II : Rare Type of Intramolecular Hydrogen Bonding In chapter 4 The rare occurrence of intramolecular hydrogen bonds of the type N–H˖˖˖F–C, in the derivatives of imides and hydrazides in a low polarity solvent, is convincingly established by employing multi-dimensional and multinuclear solution state NMR experiments. The observation of 1hJFH, 2hJFN, and 2hJFF of significant strengths, where the spin polarization is transmitted through space among the interacting NMR active nuclei, provided strong and conclusive evidence for the existence of intra-molecular hydrogen bonds. Solvent induced perturbations and the variable temperature NMR experiments unambiguously supported the presence of intramolecular hydrogen bond. The two dimensional HOESY and 15N–1H HSQC experiments reveals the existence of multiple conformers in some of the investigated molecules. The 1H DOSY experimental results discarded any possibility of self or cross-dimerization of the molecules. The results of DFT based calculations, viz., Quantum Theory of Atoms In Molecules (QTAIM) and Non Covalent Interaction (NCI), are in close agreement with the NMR experimental findings. In chapter 5 the rates of hydrogen/deuterium (H/D) exchange determined by 1H NMR spectra have been utilized to derive the strength of hydrogen bonds and to monitor the electronic effects in the site-specific halogen substituted Benz amides and anilines. The theoretical fitting of the time dependent variation in the integral areas of 1H NMR resonances to the first order decay function permitted the determination of H/D exchange rate constants (k) and their precise half-lives (t1/2) with high degree of reproducibility. The comparative study also permitted the determination of relative strengths of hydrogen bonds and the contribution from electronic effects on the H/D exchange rates. Part III: Novel NMR Methodologies for the Precise Measurement of 1H-1H Couplings Chapter 6 describes two novel NMR methodologies developed for the precise measurement of 1H-1H couplings. Poor chemical shift dispersion and the pairwise interaction among the entire coupled network of protons results in the severely complex and overcrowded one dimensional 1H NMR spectra, hampering both the resonance assignments and the accurate determination of nJHH. The available two-dimensional selective refocusing (SERF) based experiments suffer from the evolution of magnetization from uncoupled protons as intense uninformative axial peaks. This creates ambiguity in the identification of peaks belonging to the coupled partners of a selectively excited proton, hindering the extraction of their interaction strengths. This challenge has been circumvented by designing two novel experimental technique, cited as “Clean-G-SERF” and “PS-Clean-G-SERF”. The Clean-G-SERF technique completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton. The method permits the accurate determination of spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. The PS-Clean-G-SERF technique has been designed for the complete elimination of axial peaks and undesired couplings, with a blend of ultra-high resolution achieved by real time broad band mononuclear decoupling has been discussed in this chapter. The spin dynamics involved in both these pulse sequences have been discussed. The diverse applications of both these novel experiments have been demonstrated.