Krieg M, Redmond R W
Pediatrics Department, MACC Fund Research Center, Medical College of Wisconsin, Milwaukee 53226.
Photochem Photobiol. 1993 Mar;57(3):472-9. doi: 10.1111/j.1751-1097.1993.tb02321.x.
The photophysical properties of 3,3'-dialkylthiacarbocyanine iodides and chlorides were measured in various solvents. It was found that photoisomerization and fluorescence are the major contributors to the deactivation of the excited singlet state; intersystem crossing occurs with only a very low efficiency. In ethanol, a triplet yield of 0.004 and a singlet oxygen quantum yield of 0.002 were determined. The photophysical parameters of these dyes are not substantially influenced by the length of the alkyl chain or the size of the halide counterion. The substitution of an ethyl with an octadecyl-chain only slightly hinders photoisomerization, and the replacement of the chloride with an iodide reduces only marginally the fluorescence lifetimes and fluorescence quantum yields in chloroform. A significant external heavy-atom effect is observed using dibromoethane as a solvent: triplet and singlet oxygen yields increase 7-10-fold, and the triplet lifetime decreases from 55 microseconds to 15 microseconds.
在各种溶剂中测量了3,3'-二烷基硫代碳菁碘化物和氯化物的光物理性质。发现光异构化和荧光是激发单重态失活的主要因素；系间窜越的效率非常低。在乙醇中，测得三重态产率为0.004，单线态氧量子产率为0.002。这些染料的光物理参数基本上不受烷基链长度或卤化物抗衡离子大小的影响。用十八烷基链取代乙基只会轻微阻碍光异构化，用碘化物取代氯化物只会略微降低氯仿中的荧光寿命和荧光量子产率。使用二溴乙烷作为溶剂时观察到显著的外部重原子效应：三重态和单线态氧产率增加7至10倍，三重态寿命从55微秒降至15微秒。
