摘要
The trans-cis photoisomerization of pentamethine cyanine dye （Cy5） has been theoretically investigated by the analysis on an analogical molecule model. All possible isomers have been searched by rotating the different bridge C-C bonds of the model. The relative stability of the isomers for the ground and first excited states as well as the corresponding excitation mechanism has been envisaged by DFT and time-dependent DFT method. The results show different conjugation degree of the isomers resulting in different absorption energy upon the different C-C bridge bond rotation. From the analyses of electronic density distribution of the frontier orbitals, it is predicted that there is charge transfer besides the π-π^＊ excitation for the cyanine dye model, which makes the mechanism and photo-properties different form those of other conjugated molecules.
The trans-cis photoisomerization of pentamethine cyanine dye （Cy5） has been theoretically investigated by the analysis on an analogical molecule model. All possible isomers have been searched by rotating the different bridge C-C bonds of the model. The relative stability of the isomers for the ground and first excited states as well as the corresponding excitation mechanism has been envisaged by DFT and time-dependent DFT method. The results show different conjugation degree of the isomers resulting in different absorption energy upon the different C-C bridge bond rotation. From the analyses of electronic density distribution of the frontier orbitals, it is predicted that there is charge transfer besides the π-π^＊ excitation for the cyanine dye model, which makes the mechanism and photo-properties different form those of other conjugated molecules.
基金
supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry (2008-890)
The Key Project of Educational Committee of Anhui Province (KJ2010A143)
Special Project (xzx200812)
Doctor’s Project Grant of Anhui Normal University
