The photophysical and photochemical properties of some aza-analogues of 1,4-distyrylbenzene, bearing a nitrogen heteroatom in the side arene rings, have been investigated. The kinetic competition between the radiative and reactive relaxation channels of the lowest excited singlet state has been compared with that of the parent hydrocarbon. The replacement of the side phenyl rings with pyridyl or quinolyl rings was found to markedly affect the photobehavior of the three stereoisomers (EE, ZE, and ZZ). Adiabatic formation of the excited 1 EE* by irradiation of the other isomers was evidenced by fluorescence measurements. The effect of the presence of the heteroatom in the central ring, while maintaining the linear conjugation, was investigated for EE-2,5-distyrylpyridine, and it was found to be less important than that of N in the side rings. Information about the conformational equilibria of the compounds bearing side quinolyl groups or the pyridyl central ring, due to internal rotation around the quasi single bonds with the ethenic carbons, was obtained by selective photoexcitation.

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