Photocatalytic activity of the photocatalysts. Knowing that the cyclic and rigid photocatalyst exhibit the photophysical and photochemical characteristics required for the proposed photocatalytic oxidative con-PET mechanism, we selected C-N arene functionalization as a model reaction to test our hypothesis. As the excited state lifetime of the Ar 3 N •+ * is in the ps range, the substrate benzene was used as co-solvent (4.48 M) preventing the need for diffusive reaction encounters. To note, at such high substrate concentration there is no experimental indication of any pre-assembled complexes, which is in striking agreement with a detailed computational investigation on the ability of complex formation of this type of photocatalysts. Already an initial trial showed that a catalytic amount of A catalysed the reaction between benzene (4.48 M) and ethyl 1H-pyrazole-4-carboxylate (0.2 M) yielding 6% of the coupling product after 16 h hours of irradiation at 400 nm (LED, 160 mW/cm 2 ) under ambient conditions (Table , entry 1). In contrast using the non-cyclic amine, oC (see Table and SI for the structure), resulted in no product formation (Table , entry 2). This low yield may indicate that in situ radical cation formation of the photocatalyst is rather inefficient for an overall substrate conversion. To test this hypothesis, SbCl 5 was added in catalytic amounts to the system oxidizing chemically the photocatalyst to its radical cation prior to illumination. And indeed, almost full conversion could be achieved under otherwise identical conditions (Table , entry 3).