Triplet aryl cation ( 3 Ar + ): its photostimulated and thermal conversion into Ar· and role as the primary intermediate in matrix photochemistry of ArN 2 + ions

Photolysis at 77 K of 2,4,5-trimethoxybenzenediazonium hexafluorophosphate (ArN2+PF6–) yields 3Ar+ and Ar· in a ratio dependent on (i) irradiation wavelength, (ii) light intensity, (iii) matrix, (iv) photolysis time, and under selected Conditions, i.e.λirr >350 nm, low intensity, microcrystalline matrix, short photolysis time, [3Ar+]/[Ar·] exceeds 10, implying that 3Ar+ is the primary photoproduct; 3Ar+ transforms into Ar· in the dark (in any matrix), and this change is accelerated under irradiation.