Synthesis, mixed valence aspects and non-linear optical properties of the triruthenium complexes [{(bpy)2RuII}3(L)]3+ and [{(phen)2RuII}3(L)]3+ (bpy=2,2′-bipyridine, phen=1,10-phenanthroline and L3-=1,3,5-triazine-2,4,6-trithiol)

The triruthenium complexes [{(bpy)(2)Ru-II}(3)L](3+) [1](3+) and [{(phen)(2)Ru-II}(3)L](3+) [2](3+) have been synthesized via the reactions of [Ru-II(bpy)(2)(EtOH)(2)](2+) and [Ru-II(phen)(2)(EtOH)(2)](2+) with the trisodium salt of 1,3,5-triazine-2,4,6 trithiol (Na3L) respectively. In CH3CN, the complexes [1](3+) and [2](3+) exhibit three reversible one-electron redox processes corresponding to successive Ru(II)/ Ru(III) couples. The 190 - 250 mV separation in potential between the successive Ru(II)/ Ru(III) couples is indicative of moderate intermetallic electronic coupling in the mixed valence states. The bipyridine and phenanthroline based reductions are observed at - 1.58, - 1.86 V and - 1.77, - 2.01, - 2.43 V versus SCE respectively. The spectroelectrochemical study on the bipyridine derivative [1](n+) ( n = 3 - 6) in acetonitrile medium at 243 K shows a broad and relatively weak intervalence charge-transfer transition (IVCT) near 1900 nm for both the mixed valence states (RuRuRuIII)-Ru-II-Ru-II [1](4+) and (RuRuRuIII)-Ru-II-Ru-III [1](5+), characteristic of class II behaviour. The calculated coupling constant (V-ab), 560 cm(-1) is also supportive of class II mixed-valence states. The electrochemically generated one-electron oxidised species [1](4+) or [2](4+) exhibits an EPR spectrum characteristic of low-spin Ru-III ion in a distorted octahedral environment (g(1) = 2.246, g(2) = 1.993 for [1](4+) and g(1) = 2.469, g(2) = 2.191 for [2](4+)). The complexes are moderately strongly luminescent at 77 K. Both the complexes have also shown third order non-linear optical properties with gamma = -4.5 x 10(-29) esu for [1](3+) and -5.09 x 10(-29) esu for [2](3+).