期刊
JOURNAL OF PHYSICAL CHEMISTRY A
卷 116, 期 44, 页码 10786-10792出版社
AMER CHEMICAL SOC
DOI: 10.1021/jp309019g
关键词
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资金
- Division of Chemical Sciences, Geosciences, and Biosciences, Office of Basic Energy Sciences of the U.S. Department of Energy [DE-FG02-09ER16118]
- NSF-REU [CHE-1004641]
- Direct For Mathematical & Physical Scien
- Division Of Chemistry [1004641] Funding Source: National Science Foundation
The photochemistry of the rotor probe 9-(2-carboxy-2-cyanovinyl)julolidine (CCVJ) was studied to elucidate a curious effect of fluid flow previously reported. The apparent sensitivity to fluid motion observed in CCVJ but not in the closely related molecule 9-(dicyanovinyl)julolidine (DCVJ) is found to be an indirect effect of a photo-isomerization reaction. The results presented here demonstrate that it is this isomerization, rather than the commonly assumed TICT process, that confers viscosity-sensing ability on these fluorophores. In micromolar solutions in hydroxylic solvents CCVJ exists primarily in the carboxylate form. Only the E isomer of this anion is initially present in solutions prepared from the solid, but in room light such solutions rapidly achieve a photostationary state in which the E isomer and an essentially nonfluorescent Z isomer exist in comparable concentrations. The Z isomer is metastable in S-0 such that in the absence of light the solution reverts slowly to pure E. Unlike DCVJ where only a single isomer is possible, the production of long-lived photoproducts in CCVJ and other asymmetrically substituted styryenyl probes complicates their fluorescence response. Considerable care is needed when such fluorphores are used as steady-state sensors of environmental fluidity are used.
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