Heteroatom effect on the radiative and reactive photobehaviour of E,E-1,2-distyrylbenzene

The heteroatom effect on the radiative and reactive relaxations of E,E-1,2-distyrylbenzene (DSB) has been studied by stationary and time-resolved techniques on three compounds where the side phenyl (Ph) groups were replaced by 4′-pyridyl (4P), 2′-thienyl (2T) and 2′-furyl (2F) groups. Contrary to the case of the hydrocarbon, whose photoisomerization is accompanied by substantial degradation, the E,E → Z,E photoisomerization prevails in the hetero-analogues, particularly in the thienyl derivative. The lack of conjugation in these 1,2-substituted benzenes leads to a decrease in the fluorescence yield with respect to their 1,4 and 1,3 analogues (particularly in the presence of the heteroatoms), which is accompanied by an increase of the photoreaction quantum yield for the pyridyl- (significant) and thienyl- (very small) derivatives, whilst internal conversion is the prevalent deactivation pathway of the furyl derivative.