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

The compound [{(acac)(2)Ru}(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 (DeltaE greater than or equal to 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 1(2+). The separated (DeltaE greater than or equal to 540 mV) stepwise reduction produces weak near-infrared features associated with partially occupied pi* 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.