Conjugated fluorene-thiophenes prepared from azomethine connections Part I. The effect of electronic and aryl groups on the spectroscopic and electrochemical properties

Abstract

The spectroscopic investigation of new fluoreno-thiophene azomethines revealed that these compounds are fluorescent. However, they exhibit reduced fluorescence compared to native fluorene owing to competitive deactivation of the singlet excited state by nonradiative means involving both internal conversion and intersystem crossing. The absorption and emission wavelengths can be tuned and the HOMO–LUMO energy gap modulated from 2.0 to 3.2 eV by incorporating various electronic groups, number of azomethine bonds, and the fluorene-thiophene sequence. Electrochemical investigation confirmed that both oxidation and reduction occur resulting in irreversible radical ion formation.