title: Triarylimidazole redox catalysts: electrochemical analysis and empirical correlations.
abstract: 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.
authors.affiliation: College of Life Science & Bioengineering, Beijing University of Technology, Beijing 100124, China.
authors.forename: Ni-tao
authors.initials: NT
authors.lastname: Zhang
authors.forename: Cheng-chu
authors.initials: CC
authors.lastname: Zeng
authors.forename: Chiu Marco
authors.initials: CM
authors.lastname: Lam
authors.forename: Randi K
authors.initials: RK
authors.lastname: Gbur
authors.forename: R Daniel
authors.initials: RD
authors.lastname: Little