Photophysical properties of thiophenes and 2,2′-bithiophenes containing alicyclic moieties

Abstract

A series of novel 1-hydroxycycloalkyl- and cycloalkenylthiophenes (4a–4≿, 4e, 6b, 6d, 6e) and bithiophenes (5a–5e, 7b–7e) were synthesized via Grignard reaction. The conditions control in the Grignard reaction allowed to obtain tertiary alcohols or cycloalkenes selectively. The Vilsmeier–Haack formylation of thiophenes and 2,2′-bithiophenes with alicyclic fragment C4-C5 results formation of unsaturated aldehydes whereas cycloalkenes C6 form 5′-formylbithiophenes as the main isomers. The photophysical properties such as absorption and fluorescence spectra were recorded in different solvents, and relative quantum yields of aldehydes (9a, 9b, 11c–11e) and corresponding carbonitriles (13a, 13b, 15c–15e) were measured. The synthesized compounds showed an intense fluorescence in the 400–520 nm range, moderate quantum yields and large Stokes' shifts values.