title: Donor-substituted diphenylacetylene derivatives act as electron donors and acceptors.
abstract: Despite the predominant electron donor character of p-phenylenediamine, our studies on extended p-phenylenediamine derivatives show that they can not only be chemically oxidized, giving well-known Wurster-type radical cations, but also be chemically reduced, giving radical anions. Making use of EPR/ENDOR spectroscopy and supported by DFT calculations, we were able to reveal the extent of π-electron delocalization in the paramagnetic species and to shed light onto the geometry and bond lengths. While for the radical anions spin was found to be mostly delocalized into the π-system, the radical cations can be described as essentially N-centered. Furthermore, we performed electrochemical characterizations using cyclic voltammetry to gain insight into the thermodynamics of the redox processes. The photophysical properties of the parent extended p-phenylenediamine were investigated by absorption, emission, and excitation spectroscopy. The fluorescence quantum yield and the excited-state lifetime of the neutral precursors in hexane and acetonitrile were determined to establish elementary differences originating from solvent effects.
authors: Institute of Physical und Theoretical Chemistry, Graz University of Technology, Graz, Austria.
authors: Christine
authors: C
authors: Onitsch
authors: Arnulf
authors: A
authors: Rosspeintner
authors: Gonzalo
authors: G
authors: Angulo
authors: Markus
authors: M
authors: Griesser
authors: Milan
authors: M
authors: Kivala
authors: Brian
authors: B
authors: Frank
authors: François
authors: F
authors: Diederich
authors: Georg
authors: G
authors: Gescheidt