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]

Abstract

The trinuclear complexes [{(L'-)₂Ru^II}₃(μ₃-L)](ClO₄)₃, [1](ClO₄)₃-[3](ClO₄)₃ {L = trianionic form of 1,3,5-triazine-2,4,6-trithiol; N_pC₅H₄N N_a-C₆H₄(R), R = H (L′), m-Me (L?), p-Me (L)} and the analogous mononuclear complex [(L')2RuII(NC5H4S-)]ClO4 [4]ClO₄ were synthesized. Crystal structures of [1](ClO₄)₃ and [4]ClO₄ were determined. [1]³⁺-[3]³⁺ exhibit three successive oxidative couples corresponding to Ru^IIRu^IIRu^III Ru^IIRu^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 RuII-based lowest energy MLCT transitions (533-558 nm) involving the p level of azoimine chromophore of L'- varies depending on the nuclearity as well as substituents in the ligand framework and follows the order: [1]³⁺ > [2]³⁺ > [3]³⁺ > [4]⁺. 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⁺ [1]³⁺, [{(bpy)²Ru^II}₃(μ3-L)]³⁺ [5]³⁺ and [{(phen)2Ru^II}₃(μ₃-L)^]3+ [6]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.