title: Characterization of photoinduced isomerization and intersystem crossing of the cyanine dye Cy3.
abstract: Several important photophysical properties of the cyanine dye Cy3 have been determined by laser flash photolysis. The triplet-state absorption and photoisomerization of Cy3 are distinguished by using the heavy-atom effects and oxygen-induced triplet --> triplet energy transfer. Furthermore, the triplet-state extinction coefficient and quantum yield of Cy3 are also measured via triplet-triplet energy-transfer method and comparative actinometry, respectively. It is found that the triplet --> triplet (T1-->Tn) absorptions of trans-Cy3 largely overlap the ground-state absorption of cis-Cy3. Unlike what occurred in Cy5, we have not observed the triplet-state T1-->Tn absorption of cis-Cy3 and the phosphorescence from triplet state of cis-Cy3 following a singlet excitation (S0-S1) of trans-Cy3, indicating the absence of a lowest cis-triplet state as an isomerization intermediate upon excitation in Cy3. The detailed spectra of Cy3 reported in this paper could help us interpret the complicated photophysics of cyanine dyes.
authors.affiliation: The State Key Laboratory of Molecular Reaction Dynamics, and Beijing National Laboratory for Molecular Sciences (BNLMS), Institute of Chemistry, Chinese Academy of Sciences, Beijing-100080, P. R. China.
authors.forename: Ke
authors.initials: K
authors.lastname: Jia
authors.forename: Yan
authors.initials: Y
authors.lastname: Wan
authors.forename: Andong
authors.initials: A
authors.lastname: Xia
authors.forename: Shayu
authors.initials: S
authors.lastname: Li
authors.forename: Fangbin
authors.initials: F
authors.lastname: Gong
authors.forename: Guoqiang
authors.initials: G
authors.lastname: Yang
mesh_terms: D002232:Carbocyanines / Q000737:chemistry*; D007536:Isomerism; D008027:Light; D010777:Photochemistry
chemical_list: D002232:Carbocyanines; C089187:cyanine dye 3