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Updated: Jun 1, 2026

Isolating Free Carbenes, their Mixed Dimers and Organic Radicals
Published on: April 19, 2019
Donor-substituted diphenylacetylene derivatives act as electron donors and acceptors
Christine Onitsch1, Arnulf Rosspeintner, Gonzalo Angulo
1Institute of Physical und Theoretical Chemistry, Graz University of Technology, Graz, Austria.
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.
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