Highly electron-deficient 1-propyl-3,5-dinitropyridinium: evaluation of electron-accepting ability and application as an oxidative quencher for metal complexes

Impacts of the nitro groups on the electron-accepting and oxidizing abilities of N-propylpyridinium were evaluated quantitatively. A 3,5-dinitro derivative has efficiently quenched emission from photosensitizing Ru(ii) and Ir(iii) complexes owing to the thermodynamically-favored electron transfer to the pyridinium whose LUMO is greatly lowered by the presence of electron-withdrawing nitro groups. Owing to enhanced electron-accepting/oxidizing abilities, a N-propylpyridinium derivative with two electron-withdrawing nitro groups efficiently quenched emission from Ru(ii) and Ir(iii) complexes by electron transfer.