Nickelocene: A universal quencher of organic triplets

Organic triplets, with energies in the range 0.9–3.2 eV, are quenched by nickelocene with rate constants in the limit of diffusion control ((1.3–11) × 109 M−1s−1 in benzene). The efficient quenching, explainable in terms of a combination of energy and electron transfer, suggests the existence of a low-lying spin-forbidden transition (< 0.9 eV) in nickelocene.