Spectral, electrochemical and structural study of aryl derivatives of trans-stilbenes

Abstract

Aryl-substituted alkenes are promising materials for optoelectronic and photovoltaic applications. In this study we report a new series of stilbene derivatives with aromatic substituents. UV-vis absorption and fluorescence spectra of the studied compounds are presented. The optical properties are found to be dependent on dihedral angle and orbital delocalization between side substituents and the central stilbene moiety, as well as on relaxation of the excited state geometry. Especially the anthracene derivative presents different geometry and excited state properties than other studied compounds. The conclusions are supported by theoretical quantum-chemical analysis at the DFT level. Depending on the type of aromatic side substituents the HOMO orbital is localized either mainly on the central vinylene or the outmost aryl moieties. This affects the reactivity of these compounds in electrochemical reactions as well as the type of oxidation products. The thiophene derivative undergoes polymerization during oxidation and a conjugated polymer is produced while anthracene, phenylene and pentafluorophenylene derivatives undergo irreversible oxidation with creation of unconjugated products.