Unusual features in the triplet state EPR spectrum of 3,5-dichloro-4-aminophenyl cation

The tripler ground state of the 3,5-dichloro-aminophenyl cation (Ar-3(+)), generated by photolysis at 77 K of the parent arenediazonium salt, exhibits the strongest dipolar interaction in its EPR spectrum (D > 0.3 cm(-1)) found so far for any known aryl cation. It also shows high-energy site splitting, as detected by EPR for several other cations, producing two distinct forms (type A with D = 0.3066 cm(-1) and type B with D = 0.3410 cm(-1)). Ar-3(+) and certain other aryl cations also show electronic absorption spectra composed of two or three distinct bands. (C) 1997 Elsevier Science S.A.