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[摘要]：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. Maldng use of EPR/ENDOR spectroscopy and supported by DFT calculations, we were able to reveal the extent of pi-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 pi-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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