Synthesis, mixed valence aspects and non-linear optical properties of the triruthenium complexes [{(bpy)_2Ru~(II)}_3(L)]~(3+) and [{(phen)_2Ru~(II)}_3(L)]~(3+) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline and L~(3-) = 1,3,5-triazine-2,4,6-trith

摘要

The triruthenium complexes [{(bpy)_2Ru~(II)}_3L]~(3+) [1]~(3+) and [{(phen)_2Ru~(II)}_3L]~(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 (Na_3L) respectively. In CH_3CN, 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 separtion in potnetial 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, -1.86V and -1.77, -2.01, -2.43V 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 Ru~(II)Ru~(II)Ru~(III) [1]~(4+) and Ru~(II)Ru~(III)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+).