title: Electronic coupling in tetraanisylarylenediamine mixed-valence systems: the interplay between bridge energy and geometric factors.
abstract: 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.
authors.affiliation: Institut für Organische Chemie, Julius-Maximilians-Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany. lambert@chemie.uni-wuerzburg.de
authors.forename: Christoph
authors.initials: C
authors.lastname: Lambert
authors.forename: Chad
authors.initials: C
authors.lastname: Risko
authors.forename: Veaceslav
authors.initials: V
authors.lastname: Coropceanu
authors.forename: Jürgen
authors.initials: J
authors.lastname: Schelter
authors.forename: Stephan
authors.initials: S
authors.lastname: Amthor
authors.forename: Nadine E
authors.initials: NE
authors.lastname: Gruhn
authors.forename: Jason C
authors.initials: JC
authors.lastname: Durivage
authors.forename: Jean-Luc
authors.initials: JL
authors.lastname: Brédas