Investigation of solvatochromism in the low-lying singlet states of dithienyl polyenes

To understand the low-lying singlet states of dithienyl polyenes, we invest igated the solvatochromism of a series of alpha,omega-di(2-dithienyl 3,4-bu tyl) polyenes having n = 1-5 double bonds. Absorption and emission spectra were collected in a series of aprotic solvents. The absorption energy dispe rsion effect sensitivity increased smoothly with n, reaching asymptotic beh avior as n approached 5. The emission energy had less solvent sensitivity. The trends gave evidence for the existence of a B-1(u)* absorbing state and a (1)A(g)* emitting state. We observed sensitivity of the absorbing and em itting states to solute-solvent electrostatic interactions, suggesting the dithienyl polyenes had a polar ground state conformation. (C) 1999 Publishe d by Elsevier Science B.V. All rights reserved.