Electronic Coupling in Tetraanisylarylenediamine Mixed-Valence Systems: The Interplay between Bridge Energy and Geometric Factors
作者:Christoph Lambert、Chad Risko、Veaceslav Coropceanu、Jürgen Schelter、Stephan Amthor、Nadine E. Gruhn、Jason C. Durivage、Jean-Luc Brédas
DOI:10.1021/ja0512172
日期:2005.6.1
We have investigated three organic mixed-valence systems that possess nearly identical inter-redox site distances and differ by the nature of the bridging units benzene, naphthalene, and anthracene: the N,N,N',N'-tetra(4-methoxyphenyl)-1,4-phenylenene-diamine radical cation (1(+)), the 1,4-bis(N,N-di(4-methoxyphenyl)-amino)naphthalene radical cation (2(+)), and the 9,10-bis(N,N-di(4-methoxyphenyl)amino)anthracene radical cation (3(+)). The electronic interactions in these systems have been studied by means of gas-phase ultraviolet photoelectron spectroscopy, vis/NIR spectroscopy, and electronic-structure calculations. The experimental and theoretical results concur to indicate that the strength of electronic interaction decreases in the following order of bridging units: benzene > naphthalene > anthracene. This finding contradicts the usual expectation that anthracene is superior to benzene as a driving force for electronic communication. We explain these results in terms of a super-exchange mechanism and its strong dependence on steric interactions.