CARBOCATIONIC FLUORESCENCE AND ITS EFFICIENT ELECTRON-TRANSFER QUENCHING

被引:22
作者
SAMANTA, A
GOPIDAS, KR
DAS, PK
机构
[1] UNIV NOTRE DAME,RADIAT LAB,NOTRE DAME,IN 46556
[2] UNIV HYDERABAD,SCH CHEM,HYDERABAD 500134,ANDHRA PRADESH,INDIA
关键词
D O I
10.1021/j100110a020
中图分类号
O64 [物理化学(理论化学)、化学物理学];
学科分类号
070304 ; 081704 ;
摘要
The absorption and emission spectral properties of several carbocations have been examined in acidified acetonitrile and Nafion matrices. Xanthenium and thioxanthenium carbocations are characterized by moderately strong yellow-to-orange fluorescence (tau(F) = 1-30 ns). In contrast, triphenylmethyl carbocation is very weakly emitting. The fluorescence of xanthenium and thioxanthenium carbocations is readily quenched by aromatics by a predominantly charge-transfer mechanism; the quenching rate constants are in the limit of diffusion control. Electron-transfer-derived radical cations (from aromatic quenchers) and radicals (from carbocations) are observed in the course of nanosecond laser flash photolysis. The yields of net electron transfer are, however, low (less-than-or-equal-to 0.02), suggesting efficient back electron transfer in the radical cation/radical pairs in singlet configuration.
引用
收藏
页码:1583 / 1588
页数:6
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