Triplet-state electron spin resonance studies of aryl cations. Part 3. Substituent and medium effects for aminophenyl cations

Abstract

The presence of a strong medium effect on the observation of triplet-state Ar⁺ has been noted, enabling extension of our previous studies to further examples of triplet Ar⁺ including that of the parent molecule of the series, p-NH₂-C₆H₄⁺ which features a D parameter of 0.2967 cm^–1 and of the o-morpholinophenyl cation (D 0.1671 cm^–1) which is the first example of Ar⁺ stabilised in its triplet state by a single ortho-substituent. The trend, noted earlier, for a large D parameter to be associated with a good π-donor in the 4-position, is confirmed by new examples.