Electrostatically driven geometry changes accompanying charge separation in supposedly rigid bichromophoric systems

被引:18
作者
Shephard, MJ [1 ]
Paddon-Row, MN [1 ]
机构
[1] Univ New S Wales, Sch Chem, Sydney, NSW 2052, Australia
关键词
D O I
10.1021/jp002451b
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
Calculations on the structures of a variety of charge-separated (CS) bichromophoric systems in the gas phase were carried out at the UHF, CIS, and UB3LYP theoretical levels, using the 3-21G, 6-31G(d), and 6-31+G-(d basis sets. The results indicate that the relatively computationally inexpensive UHF/3-21G method gives a reliable description of the molecular structure and charge distribution in these states. It is predicted that the CS states of most of the bichromophoric systems studied will undergo strong structural distortions due to the Coulombic forces operating between the two charged chromophores. These structural distortions are largely associated with changes in the geometries of the charged chromophores, although the putative "rigid" saturated hydrocarbon bridges connecting the chromophores can also undergo some distortion. In the case of 8b, the distorted CS geometry predicted by these calculations is consistent with results obtained from recent experimental charge recombination studies on the CS state of the similar system, 8a. Geometry changes accompanying charge separation or charge recombination processes, on the scale predicted here, might influence the interpretation of rate data based on semiclassical ET theories.
引用
收藏
页码:11628 / 11635
页数:8
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