Structure-Aromaticity-Spectroscopy Relationship in Conjugated Polymers

Abstract

Abstract In this study, an effort has been made to analyze the aromaticity of oligomers of benzene and thiophene, with and without linkers using Nucleus-Independent Chemical Shift (NICS) as a descriptor, and their relation with HOMO-LUMO gap, reorganization energy and excitation energy. Thus, calculations have been performed to develop structure-aromaticity-spectroscopy relationship. Although the inter-relationship between geometry and aromaticity has been extensively discussed in the literature, the present study provides pointers about relationship between aromaticity, conjugation, and spectroscopic properties. Benzene and thiophene-based oligomers have been chosen for the study comprising of vinyl and ethynyl linkers along with the α-linked benzene and thiophene oligomers as model systems. The results show that both HOMO-LUMO gaps and excitation energies exhibit linear relationship with inverse of the NICS values, indicating the possible existence of the structure-aromaticity-π-conjugation-spectroscopy relationship.