Distance Dependence of Electron Transfer in Rigid, Cofacially Compressed, -Stacked Porphyrin-Bridge-Quinone Systems
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- 作者：Youn K. Kang ; Igor V. Rubtsov ; Peter M. Iovine ; Jianxin Chen ; and Michael J. Therien
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：July 17, 2002
- 年：2002
- 卷：124
- 期：28
- 页码：8275 - 8279
- 全文大小：81K
- 年卷期：v.124,no.28(July 17, 2002)
- ISSN：1520-5126
文摘
The electron-transfer (ET) dynamics of a series of unusually rigid 
-stacked porphyrin-quinone(P-Q) systems, in which sub-van der Waals interplanar distances separate juxtaposed porphyryl, aromaticbridge, and quinonyl components of these assemblies, are reported. The photoinduced charge separation(CS) and thermal charge recombination (CR) ET reactions of [5-[8'-(2' ',5' '-benzoquinonyl)-1'-naphthyl]-10,20-diphenylporphinato]zinc(II) (1a-Zn), [5-[8'-(4' '-[8' ''-(2' '' ',5' '' '-benzoquinonyl)-1' ''-naphthyl]-1' '-phenyl)-1'-naphthyl]-10,20-diphenylporphinato]zinc(II) (2a-Zn), and [5-(8'-[4' '-(8' ''-[4' '' '-(8' '' ''-[2' '' '' ',5' '' '' '-benzoquinonyl]-1' '' ''-naphthyl)-1' '' '-phenyl]-1' ''-naphthyl)-1' '-phenyl]-1'-naphthyl)-10,20-diphenylporphinato]zinc(II) (3a-Zn)in CH2Cl2 were investigated by pump-probe transient absorption spectroscopy. Analyses of thesedata show that the phenomenological ET distance dependence (
) for both the CS and CR reactionsin these systems is soft (CS = 0.43 Å-1; CR = 0.35 ± 0.16 Å-1). This work demonstrates that simplearomatic building blocks such as benzene, which are characterized by highly stabilized filled molecularorbitals and large HOMO-LUMO gaps, can provide substantial D-A electronic coupling when organizedwithin a -stacked structural motif that features a modest degree of arene-arene interplanar compression.
-stacked porphyrin-quinone(P-Q) systems, in which sub-van der Waals interplanar distances separate juxtaposed porphyryl, aromaticbridge, and quinonyl components of these assemblies, are reported. The photoinduced charge separation(CS) and thermal charge recombination (CR) ET reactions of [5-[8'-(2' ',5' '-benzoquinonyl)-1'-naphthyl]-10,20-diphenylporphinato]zinc(II) (1a-Zn), [5-[8'-(4' '-[8' ''-(2' '' ',5' '' '-benzoquinonyl)-1' ''-naphthyl]-1' '-phenyl)-1'-naphthyl]-10,20-diphenylporphinato]zinc(II) (2a-Zn), and [5-(8'-[4' '-(8' ''-[4' '' '-(8' '' ''-[2' '' '' ',5' '' '' '-benzoquinonyl]-1' '' ''-naphthyl)-1' '' '-phenyl]-1' ''-naphthyl)-1' '-phenyl]-1'-naphthyl)-10,20-diphenylporphinato]zinc(II) (3a-Zn)in CH2Cl2 were investigated by pump-probe transient absorption spectroscopy. Analyses of thesedata show that the phenomenological ET distance dependence () for both the CS and CR reactionsin these systems is soft (CS = 0.43 Å-1; CR = 0.35 ± 0.16 Å-1). This work demonstrates that simplearomatic building blocks such as benzene, which are characterized by highly stabilized filled molecularorbitals and large HOMO-LUMO gaps, can provide substantial D-A electronic coupling when organizedwithin a -stacked structural motif that features a modest degree of arene-arene interplanar compression.