Affiliation:
1. Dipartimento di Chimica, Università di Perugia, Perugia I-06123, Italy
Abstract
The photobehaviour of four aza-analogues ofEE-distyrylbenzene bearing the heteroatom in the two side rings [1,4-di-(2-pyridylethenyl)benzene] or in the central ring [2,5-di-(phenylethenyl)pyridine, 2,6-di(phenylethenyl)pyridine and the corresponding diene, 2,6-di(phenylbutadienyl)pyridine] has been investigated in aqueous solutions at pH 2 and 9, where the molecules are in mono-protonated and neutral forms, respectively. The type of conjugation, linear for the first two compounds and crossed for the others, is particularly important in determining the spectral and photochemical properties. The main effects of the protic solvent are a reduction of the radiative deactivation, prevalent in the corresponding hydrocarbons, and an increase of the reactive deactivation, very modest in the hydrocarbons. The increase in photoreactivity to detriment of fluorescence, observed in protic medium with respect to non-polar solvents, is drastically emphasized in acid medium where the fluorescence quantum yield decreases by an order of magnitude leading to high values of theEE→ZEphotoisomerization quantum yield. The presence of conformational isomerism (two main conformers were detected) has been observed in both basic and acid media for compounds with crossed conjugation and for the linearly conjugated 2,5 substituted pyridine. The results obtained give a picture of the different photobehaviour of the neutral and protonated species and indicate the experimental conditions to favour a specific relaxation pathway.
Funder
Ministero dell’Istruzione, dell’Università e della Ricerca
Subject
General Materials Science,Renewable Energy, Sustainability and the Environment,Atomic and Molecular Physics, and Optics,General Chemistry
Cited by
9 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献