Based on these photophysical investigations, a possible catalytic mechanism in operation for the C(sp)-C(sp 3 ) cross coupling reaction under our reaction conditions is presented in Scheme The significant difference between pDTCz-DPmS and HE is that the former acts photocatalytically, namely it operates in such a way as to be regenerated during the course of the reaction. By contrast, HE effectively acts as a stoichiometric photoreductant. To further confirm this, we monitored the reaction in the absence of PC by 1 H NMR spectroscopy (Figure ). During the reaction, a quartet at 4.39 ppm is seen to increase in magnitude. This quartet is indicative of the aromatized HE (diethyl 2,6-dimethylpyridine-3,5-dicarboxylate, Figure ); further, observed singlets at 8.67 and 2.85 ppm are also associated with the oxidised HE generated during the reaction.