Synthesis, structure, redox, NLO and DNA interaction aspects of [{(L ^′-″′)2Ru^II} ₃(μ₃-L)]³⁺ and [(L^′) 2Ru^II(NC₅H₄S^-)]⁺ [L ^3- = 1,3,5-triazine-2,4,6-trithiolato, L ^′-″′ = arylazopyridine]

The trinuclear complexes [{(L^′-″′) ₂Ru^II}₃(μ₃-L)](ClCO ₄)₃, (ClO₄)₃ - (ClO ₄)₃ {L = trianionic form of 1,3,5-triazine-2,4,6-trithiol; N_pC₅H₄N=N_a - C₆H ₄(R), R= H (L′), m-Me (L″),p-Me (L″′)} and the analogous mononuclear complex [(L′)₂Ru^II(NC ₅H₄S^-)]ClO₄ ClO₄ were synthesized. Crystal structures of (ClO₄)₃ and ClO ₄ were determined. ^3-3- exhibit three successive oxidative couples corresponding to Ru^IIR ^IIR^III⇌ Ri^IIRi^IIRu ^II; Ru^IIRu^IIIRu^III ⇌ Ru ^IIRu^IIRu^III; Ru^IIIRu ^IIIRu^III ⇌ Ru^IIRu^IIIRu ^III where the mixed valent states are moderately coupled. The complexes display multiple reductions associated with the azo functions of the ancillary ligands (L^′-″′). The energy of the Ru^II-based lowest energy MLCT transitions (533-558 nm) involving the π* level of azoimine chromophore of L^′-″′ varies depending on the nuclearity as well as substituents in the ligand framework and follows the order: ³⁺ > ³⁺ > ³⁺ > ⁺. The complexes exhibit reasonably high third-order non-linear optical properties with γ = (0.90-2.45) × 10^-29 esu. The interactions of the trinuclear complexes [{(L ^′)₂Ru^II}₃(μ₃-L)] ^{3- 3+}, [{(bpy)₂Ru^II} ₃(μ₃-L)]^{3- 3+} and [{(phen) ₂Ru^II}₃(μ₃-L)]^{3+ 3-} (bpy = 2,2′-bipyridine and phen = 1,10-phenanthroline) with the circular and linear forms of p-Bluescript DNA show reduced ethidium bromide fluorescence on gel electrophoresis.