A new mixed-valence Cu-I/Cu-II three-dimensional coordination polymer constructed with an N,O-donor ligand generated via solvothermal synthesis: structural features and magnetic properties

A new mixed-valence Cu-I/Cu-II three-dimensional coordination polymer, poly[[diaquabis[mu(4)-2-(pyrazin-2-yl)quinoline-4- carboxylato]dicopper(I)copper(II)] bis( tetrafluoridoborate)], {[Cu-3(C14H8N3O2)(2)(H2O)(2)](BF4)(2)}(n), was synthesized and characterized, with 2-(pyrazin-2-yl)quinoline-4-carboxylic acid being employed as a linker ligand. The ligand was isolated as its hydrochloride salt, 4-carboxy-2-(pyrazin-2-yl)quinolin-1-ium chloride dihydrate, C14H10N3O2+ center dot Cl(- center dot)2H(2)O. The compounds show luminescence at 550 nm for the ligand and at 565 nm for the polymer at 297 K. The ligand structure was rationalized by means of quantum-chemical calculations, which led to a similar conformation to that determined from X-ray diffraction studies.