Intervalence charge transfer (IVCT) in ruthenium dinuclear and trinuclear assemblies containing the bridging ligand HAT {1,4,5,8,9,12-hexaazatriphenylene}

The lVCT characteristics of the mixed-valence forms of the dinuclear [{Ru(bpy)(2)}(2)(mu-hat)](n+) and the trinuclear [{Ru(bpy)(2)}(3)(mu-hat)](n+) species {HAT = 1,4,5,8,9,12-hexaazatriphenylene; bpy=2,2'-bipyridine} show a marked dependence on the nuclearity, and in the trinuclear case on the extent of oxidation. Small differences are also found between the diastereoisomers of the dinuclear complex {meso (AA) and rac (Delta Delta/Lambda Lambda)}, and between the homochiral (Delta(3)/Delta(3)) and heterochiral (Delta(2)Lambda/Lambda(2)Delta) diastereoisomers of the trinuclear case. The strong metal-metal interactions result in unusual spectroscopic and electrochemical properties of the singly-oxidised (+7) and doubly-oxidised (+8) trinuclear mixed-valence species. A qualitative localised bonding description based on the geometrical properties of the d pi(Ru-II/III) orbitals is invoked to explain the IVCT behaviour in the di- and trinuclear systems.