The triruthenium complex [{(acac)2RuII}3(L)] containing a conjugated diquinoxaline[2,3-a:2′,3′-c]phenazine (L) bridge and acetylacetonate (acac) as ancillary ligands. Synthesis, spectroelectrochemical and EPR investigation

Abstract

The compound [{(acac)₂Ru}₃(L)] (1) undergoes three well-separated one-electron oxidation and reduction processes. The EPR results indicate electron removal from the ruthenium(II) centres on oxidation and the occupation of a largely L-based molecular orbital on reduction. In spite of well-separated (ΔE ≥ 340 mV) oxidation no obvious intervalence charge transfer bands were detected in the Vis, NIR or IR regions, suggesting very weak electronic coupling between the metal centres in the mixed-valent intermediates 1⁺ and 1²⁺. The separated (ΔE ≥ 540 mV) stepwise reduction produces weak near-infrared features associated with partially occupied π* orbitals of L, the unusually high g anisotropy in the EPR spectrum of 1⁻ is attributed to the occupation of a degenerate MO by the unpaired electron.