Switchable Electronic Coupling in Model Oligoporphyrin Molecular Wires Examined through the Measurement and Assignment of Electronic Absorption Spectra
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- 作者：Karina Sendt ; Lesley A. Johnston ; Warren A. Hough ; Maxwell J. Crossley ; Noel S. Hush ; and Jeffrey R. Reimers
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：August 7, 2002
- 年：2002
- 卷：124
- 期：31
- 页码：9299 - 9309
- 全文大小：151K
- 年卷期：v.124,no.31(August 7, 2002)
- ISSN：1520-5126
文摘
The use of a quinone functionality in the linkage unit of laterally bridged oligoporphyrins as aswitch for controlling electronic coupling between the termini is examined. The quinone-bridged bisporphyrinP2TA-O2 was synthesized by condensation of 2 equiv of the dione 2,3-dioxo-5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)chlorin with 2,3,5,6-tetraamino-1,4-benzoquinone. The electronic absorption spectra of P2TA-O2 and its conjugated benzenoid analogue P2TA are measured and assigned, in conjunction with thespectra of the fragment monomers and porphyrin-bridge compounds. Band homologies and CASPT2calculations are used to make the assignments. Chemically, the dimer in one case is bridged by a through-conjugated, 
-delocalized 1,4,5,8-tetraazaanthracene molecule. This is shown to display significant inter-porphyrin coupling, with an observed difference in the exciton couplings of the Bx and By bands being ca.0.18 eV. However, the other dimer is bridged using a derivative in which the central ring is converted to across-conjugated, -localized quinonoid form; this molecule displays no observable inter-porphyrin coupling.This scenario provides a paradigm for the use of molecular electronic devices in sensing, control, andhigh-capacity relatively low-speed data storage applications.
-delocalized 1,4,5,8-tetraazaanthracene molecule. This is shown to display significant inter-porphyrin coupling, with an observed difference in the exciton couplings of the Bx and By bands being ca.0.18 eV. However, the other dimer is bridged using a derivative in which the central ring is converted to across-conjugated, -localized quinonoid form; this molecule displays no observable inter-porphyrin coupling.This scenario provides a paradigm for the use of molecular electronic devices in sensing, control, andhigh-capacity relatively low-speed data storage applications.