Electron transfer quenching and electrochemiluminescence comparative studies of the systems containing N-methylpyridinium cations and Ru(2,2′-bipyridine)32+ or Ru(1,10-phenathroline)32+ complexes

Quenching of the luminescent state of tris(2,2'-bipyridine)ruthenium(II) and tris(1,10-phenanthroline)ruthenium(H) (Ru(bipy)(3)(2+) and Ru(phen)(3)(2+)) complexes by a series of pyridinium ions has been studied in 0.1M (C2H5)(4)-NPF6 acetonitrile solutions. 4-Acetyl, 4-cyano, 4-carbomethoxy, and 4-carbamido-1-methylpyridium cations R+ were employed as electron acceptor quenchers. The quenching rates were measured by using steady-state technique. Separation efficiencies of electron-transfer products were obtained by measurements of the transient absorbances of photogenerated N-methylpyridinium radicals R-. using laser flash photolysis. The quenching rate constants and radical separation efficiencies were used for the calculation of the kinetic parameters for forward, reverse and back electron transfer. Opposite electron-transfer process, i.e., a generation of the excited states *Ru(bipy)(3)(2+) and *Ru(phen)(3)(2+) (in reactions Ru(bipy)3 31 + R-. or Ru(phen)(3)(3+) + R-., respectively), has been studied by means of the electrochemically generated chemiluminescence. Reaction schemes for both types of the electron transfer processes have been comparatively discussed concluding that the same set of the kinetic parameters may be successfully applied in quantitative description.