ELECTRONIC STATES AND OPTICAL-PROPERTIES OF PORPHYRINS IN VANDERWAALS CONTACT - TH(IV) SANDWICH COMPLEXES

被引:87
作者
BILSEL, O
RODRIGUEZ, J
MILAM, SN
GORLIN, PA
GIROLAMI, GS
SUSLICK, KS
HOLTEN, D
机构
[1] UNIV ILLINOIS,SCH CHEM SCI,URBANA,IL 61801
[2] WASHINGTON UNIV,DEPT CHEM,ST LOUIS,MO 63130
关键词
D O I
10.1021/ja00042a037
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
Ground-state and time-resolved excited-state absorption spectra and fluorescence and phosphorescence spectra of three Th(IV) sandwich complexes, Th(IV)(TPP)2, Th(IV)(OEP)2, and Th(IV)(OEP)(TPP), are reported (OEP = 2,3,7,8,12,13,17,18-octaethylporphyrinate, TPP = 5,10,15,20-tetraphenylporphyrinate). These complexes, in which the nitrogen planes of the two porphyrin macrocycles are approximately 2.9 angstrom apart, exhibit a number of prominent optical characteristics: (i) monoporphyrin-like Q and B absorption bands, (ii) a new absorption between the Q and B bands, (iii) a weak, low-energy absorption that is substantially red-shifted relative to the Q bands of analogous monoporphyrin complexes, (iv) fluorescence and phosphorescence emission bands that are even further red-shifted relative to typical emission bands from porphyrin monomers, and (v) a moderately intense near-infrared 3(pi,pi*) excited-state absorption not observed in monomeric porphyrins. These characteristic optical properties of the sandwich complexes are all accounted for by a relatively simple molecular orbital configuration-interaction model. Additionally, the spectral data and molecular orbital model identify the energies of charge-transfer configurations and delineate their contribution to the electronic states of these strongly-coupled pi-systems. These results provide insights into the interactions that can take place between other pairs of chromophores brought within van der Waals contact, such as the bacteriochlorophyll dimer of the photosynthetic reaction center.
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页码:6528 / 6538
页数:11
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