Syntheses, crystal structures and MMCT properties of diruthenium-based cyanido-bridged Ru V/VI2–NC–RuII complexes

Abstract

The goal of this study was to investigate how the electron-donating capability around the lower valent metal ion and the electron-accepting capability of the higher valent metal ion influence metal to metal charge transfer (MMCT) properties in mixed-valence complexes. A series of trinuclear ruthenium complexes represented as [Ru₂(ap-4-Me)₃(CH₃COO)NCRuCpMe_x(dppe)][PF₆] (CpMe_x = polymethylcyclopentadienyl, x = 0, 1, and 5; and dppe = 1, 2-bis(diphenylphosphino)ethane, ap-4-Me = 2-anilino-4-methylpyridine) and their one-electron oxidized products were synthesized and fully characterized. The UV–vis-NIR spectra confirmed that as the electron donor character of the CpMe_x(dppe)RuCN fragment enhanced or the electron-accepting capability of the higher valent diruthenium cluster increased, the Ru^II → Ru^V₂ or Ru^VI₂ Ru₂ MMCT bands shifted to lower energies, which was supported by TDDFT calculations.