Synthesis, structure, redox, NLO and DNA interaction aspects of [{(L '(-)''')(2)Ru-II}(3)(mu(3)-L)](3+) and [(L ')(2)Ru-II(NC5H4S-)](+) [L3-=1,3,5-triazine-2,4,6-trithiolato, L '(-)''' = arylazopyridine]

Abstract

The trinuclear complexes [{(L-'/"')(2)Ru-II}(3)(mu(3)-L)](ClO4)(3), [1](ClO4)(3)-[3](ClO4)(3){L=trianionic form of 1,3,5-triazine-2,4,6-trithiol; NpC5H4N=N-a-C6H4(R), R=H (L'), m-Me (L"), p-Me (L"')} and the analogous mononuclear complex [(L')(2)Ru-II(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(II)Ru(II)Ru(III)reversible arrowRu(II)Ru(II)Ru(II); Ru(II)Ru(III)Ru(III)reversible arrowRu(II)Ru(II)Ru(III); Ru(III)Ru(III)Ru(III)reversible arrowRu(II)Ru(III)Ru(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 pi* 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 gamma=(0.90-2.45)x10(-29) esu. The interactions of the trinuclear complexes [{(L')(2)Ru-II}(3)(mu(3)-L)](3+) [1](3+), [{(bpy)(2)Ru-II} 3(mu(3)-L)](3+) [5](3+) and [{(phen)(2)Ru-II}(3)(mu(3)-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.