Supramolecular Chemistry of Thiazole Based Urea/Thiourea and Imine/Amine Derivatives : Polymorphism, Molecular/ion recognition

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Self-assembly, guided by noncovalent interactions is one of the fundamental features associated with biological systems. Inspired by this biological phenomenon, self-assembly has become a key step for miniaturization of functional devices and the development of future nanotechnology. Based on free rotation of C-N bond over intramolecularly hydrogen bonded six-membered synthon of a phenyl thiourea tethered thiazole derivative, three polymorphs were isolated. Each polymorph was obtained by crystallization from different solvent systems. Highly ordered structures were observed in each case, comprising of molecules with different orientation arranged in their respective lattice. But in case of the respective positional isomer, no polymorphs were observed, due to intermolecular locking of orientations over hydrogen bonded six-membered ring. Each polymorph as well as the monomorph adopts syn-anti orientation across the thiourea moiety. By protonating thiazole nitrogen, various salts of the two positional isomeric thiourea tethered thiazole derivative were prepared. Each salt adopt syn-syn orientation across the thiourea moiety. Formation of hydrated anion assembly and deprotonation of a polyacid to form crystalline salt is host-specific. Novel clusters of hydrated bromide ions, cyclic assemblies of dihydrogen phosphate, and chainlike structure of assemblies of bisulphate-water were established by stabilizing them in cationic hosts.
Supervisor: J. B. Baruah