Effect of solvent polarity, pH, and metal complexation on the triple fluorescence of 4-(N-1,4,8,11-tetraazacyclotetradecyl)benzonitrile

被引:50
作者
Collins, GE [1 ]
Choi, LS [1 ]
Callahan, JH [1 ]
机构
[1] USN, Res Lab, Div Chem, Washington, DC 20375 USA
关键词
D O I
10.1021/ja972169r
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Triple fluorescence is observed for 3-(N-1,4,8,11-tetraazacyclotetradecyl)benzonitrile (DMABN-Cyclam) in ethanol, corresponding to a locally excited (LE) singlet state, a twisted intramolecular charge-transfer (TICT) state. and an intramolecular exciplex (E). The LE state emission dominates the spectrum in nonpolar solvents such as n-hexane, while polar solvents stabilize the charge-transfer states, TICT and E. Optimal intramolecular exciplex emission, however, was observed in toluene, while the TICT band was maximal in water. The influence of pH on the fluorescent properties of DMABN-Cyclam were studied, indicating that protonation of cyclam strongly influences the equilibria existing between the three excited-state species, as well as the extent of quenching apparent for each excited-state band. DMABN-Cyclam uniquely responded to the addition of micromolar quantities of transition metal cations with varying changes in the triple fluorescence emission.
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页码:1474 / 1478
页数:5
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