Mono- and Dinuclear Ruthenium(II) Complexes of 2,6-Di(pyrazol-3-yl)pyridines: Deprotonation, Functionalization, and Supramolecular Association

A number of Ru(II) complexes, both homo- and heteroleptic, of variously N-substituted 2,6-di(4,5,6,7-tetrahydroindazol-3-yl)pyridines have been prepared from the free ligands or by N-alkylations of Ru-bound, N-H-bearing ligands. Carboxyl-bearing complexes were prepared by hydrolysis of the corresponding esterified complexes. All were characterized by elemental analysis and by their NMR, FAB-MS, and UV−visible spectra, and a selection was additionally submitted to cyclic voltammetry. The fully substituted complexes showed MLCT bands in the 414−424 nm range and E1/23+/2+ values in the +0.83−0.98 V range. Comparisons with data from related complexes are discussed. A heteroleptic dinuclear species was prepared from a CH2-linked bis(tridentate) and found to consist of the like (chiral racemic) diastereomer. It showed a single MLCT band at 416 nm and a single Ru3+/2+ couple at +0.98 V. In the case of N-H-bearing complexes, deprotonation caused the appearance of a less energetic MLCT band and multiple CV waves a...