Surface modification of carbon and metal electrodes with bistable molecular redox switches by click and amide coupling

摘要

Ruthenium complexes [Ru(R-Ph-tpy)(bpyMeOHpy)] (Ph-tpy = 4'-(4-R-phenyl)-2,2':6',2 ''-terpyridine, R = NH2, COOH, CRCH, bpyMeOHpy = 1-[6-(2,2'-bipyridyl)]-1-(2-pyridyl)-ethanol) were covalently attached to carbon and metal electrodes by amide and click coupling reactions. Coupling agents were covalently grafted onto the electrodes by electrochemical reduction of p-functionalized diazonium tethers X-Ph-N-2(+) (X = COOH, NO2, N-3) followed by electrochemical reduction of the nitro tether. The modification of the electrode surfaces with the Ru complexes results in a hysteretic current-voltage response based on the redox-induced N-6/N5O linkage isomerism of the ambidentate pyridyl/alkoxy unit in the bpyMeOHpy chelate ligand. The immobilized complexes can be exhaustively addressed electrochemically with scan rates <= 10000 V s(-1) and can switch uniformly with kinetic and thermodynamic parameters similar to the properties of reference complexes in homogeneous solution.