American Chemical Society
jo302309m_si_001.pdf (3.46 MB)

Triarylimidazole Redox Catalysts: Electrochemical Analysis and Empirical Correlations

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journal contribution
posted on 2013-03-01, 00:00 authored by Ni-tao Zhang, Cheng-chu Zeng, Chiu Marco Lam, Randi K. Gbur, R. Daniel Little
A series of triarylimidazoles was synthesized and characterized electrochemically. The synthetic route is general, providing a pathway to 30 redox mediators that exhibit a > 700 mV range of accessible potentials. Most of the triarylimidazoles display three oxidation peaks where the first redox couple is quasi-reversible. The electronic character of the substituents affects the oxidation potential. This is exemplified by a linear correlation between the first oxidation potential and the sum of the Hammett σ+ substituent constants, as well as with a series of calculated ionization potentials. We close by putting forward a rule of thumb stating that for a given mediator, the upper limit of accessible potentials can be extended by at least 500 mV beyond the largest recorded value. A rationale, the conditions under which the rule is likely to apply, and an example are provided.