Photophysics of molecular rotors of functionalized surface-active styrylcyanine dyes

Abstract

This paper describes the essential photophysical properties of a newly synthesized 1-cetyl-4-(p-NN-dimethylamino styryl)-pyridinium bromide and its parent short-chain styrylcyanine dye. These dyes exhibit similar fluorescence behaviour and are characterized by extensive non-radiative processes. The observed main differences are related to the long-chain hydrocarbon group and are found to be an enhanced sensitivity of the organized surfactant molecules to solvent interactions. The influence of various macro-and micro-scopic solvent properties on the photophysical properties of the dyes is investigated, with particular focus on the interplay of dye structure and specific solvent-solute interactions that govern the competition between radiative and non-radiative decay. It is found that specific interactions by hydrogen-bonding solvents are the key controlling factors in the relaxation processes. The results are expressed in terms of linear and multilinear relationships. Correlating the experimental results with theory (CNDO and PPP-SCF-CI calculations) provides a better insight into the excited-state properties of these dyes.