Molecular Recognition and Coordination Chemistry of Mixed Donor Ligands

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The thesis entitled, DMolecular Recognition and Coordination Chemistry of Mixed Donor LigandsD is divided into five chapters. Chapter-1 gives a brief introduction as well as literature survey of molecular recognition and coordination chemistry of various mixed donor ligand systems. It describes various aspects of supramolecular self-assembly processes, molecular recognition, supramolecular photochemistry. It also describes the literature regarding the coordination chemistry of aryl azo dyes containing mixed donor sites. Host-Guest chemistry of molecular recognition is a highly expanding area of supramolecular chemistry. The term molecular recognition refers to the specific interaction between two or more molecules through noncovalent bonding such as hydrogen bonding, metal coordination, hydrophobic forces, van der Waals forces, D-D interactions, electrostatic and/or electromagnetic effects. The host and guest involved in molecular recognition exhibit molecular complementarities. Chemists have demonstrated that artificial supramolecular systems can be designed that exhibit molecular recognition. Molecular recognition can be subdivided into static molecular recognition and dynamic molecular recognition. Static molecular recognition is likened to the interaction between a key and a key hole; it is a 1:1 type complexation reaction between a host molecule and a guest molecule to form a host-guest complex. To achieve advanced static molecular recognition, it is necessary to make recognition sites that are specific for guest molecules. In the case of dynamic molecular recognition the binding of the first guest to the first binding site of a host affects the overall association. Syntheses of organic dyes are important in the field of molecular sensor technologies, particularly; their use in biological applications has gained considerable interest in the last few years. Azo-dyes are widely used in analytical chemistry and dyestuff industry, while textile mills predominantly use them. Recently they have received much attention in the field of nonlinear optics, optical storage and other photoelectric applications. Derivatives of azo-chromophore with pyrazole or imidazole as the heterocyclic component belong to class of organic ligand that contain four nitrogen atoms coupled in conjugated system of D-bonds. Azo function is photochromic, redox active, pH responsive and their complexes act as a molecular switch. Various fluorescent hosts have been developed for sensitive and simple detections of various guest molecules. However, these approaches have often involved the synthesis of structurally complicated hosts. Therefore, it is of high importance in the filed of photochemistry to discover and/or develop new simple and sensitive host molecule with fluorophore attached to it. Due to the many possible applications in analytical chemistry and biomedical research, considerable...
Supervisor: Gopal Das