Systematic Investigations of Polymorphism Photodimerization and Charge Transfer Mechanism in Organic Optical Materials

Abstract

This thesis involved efficient design of a series of multifunctional push-pull organic chromophores based on theoretical calculations and thereby syntheses and characterizations. Two types of scaffolds CNS and 3THC are considered as substrates for exploring their potential as photosensitive, polymorph, NLO and optoelectronic materials. Their structural features and exotic properties are then derived through systematic investigations using various theoretical methods and experimental techniques. Thereby, the structure-property relationships are derived both qualitatively and quantitatively. Unprecedented, environment friendly, catalysts and sensitizers-free photodimerization of acrylonitrile based push-pull Z-olefins, compounds 1-10, resulted in controlled regio- and stereoselective, densely functionalized cyclobutane ring under ambiant sunlight. Systematic crystallization experiments on compounds 3, 10 and 16 resulted in three isostructural polymorphs, two concomitant polymorphs and as many as eight solvatomorphs, respectively. Further, the underlying charge-transfer mechanism in the non-centrosymmetric crystal of compound 1 is understood via experimental charge density analysis based on high-resolution X-ray diffraction data. The high-mobilities of electrons and holes along the charge-transfer pathway is then verified upon fabrication of a protoype device based on its single crystal. In case of compound 19, a wide range of solid state emission (560 630nm) had been acheieved based on tactful polymorphic modification. Finally, the thesis work evidenced the discovery of a series of novel organic (nonlinear) optical materials and their polymorphic forms and further we explored their exhotic properties. It is expected that the materials discovered and the results generated through this thesis would help finding appropriate applications for certain societal need.