Triarylmethyl-based biradical as a superoxide probe.

Superoxide radical represents one of the most biologically relevant reactive oxygen species involved in numerous physiological and pathophysiological processes. Superoxide measurement through the decay of an electron paramagnetic resonance (EPR) signal of a triarylmethyl (TAM) radical possesses the advantage of a high selectivity and relatively high rate constant of TAM reaction with the superoxide. Hereby we report a straightforward synthesis and characterization of a TAM-TAM biradical showing a high reactivity with superoxide (second-order rate constant, (6.7 ± 0.2) × 103 M-1 s-1) enabling the measurement of superoxide radical by following the increase of a sharp EPR signal associated with the formation of a TAM-quinone-methide monoradical product.