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

A new mixed-valence CuI/CuII three-dimensional coordination polymer, poly[[diaquabis[µ4-2-(pyrazin-2-yl)quinoline-4-carboxylato]dicopper(I)copper(II)] bis(tetrafluoridoborate)], {[Cu3(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+·Cl-·2H2O. 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.

A new photoluminescent coordination polymer constructed with an N-donor ligand having extended coordination capabilities derived from quinoline and pyridine.

Employment of the organic 2-(pyridin-4-yl)quinoline-4-carboxylic acid ligand with extended coordination capabilities leads to the formation of the one-dimensional copper(II) coordination polymer catena-poly[[diaquacopper(II)]-bis[µ-2-(pyridin-4-yl)quinoline-4-carboxylato]-κ2N2:O;κ2O:N], {[Cu(C15H9N2O2)2(H2O)2]·2H2O}n, under hydrothermal conditions. The ligand, isolated as its hydrochloride salt, namely, 4-(4-carboxyquinolin-2-yl)pyridinium chloride monohydrate, C15H11N2O2+·Cl-·H2O, reveals a pseudosymmetry element (translation a/2) in its crystal structure. The additional pyridyl N atom, in comparison with the previously reported analogues with an arene ring instead of the pyridyl ring in the present ligand molecule, promotes the formation of a one-dimensional coordination polymer, rather than discrete molecules. This polymer shows photoluminescent properties with bathochromic/hypsochromic shifts of the ligand absorption bands, leading to a single band at 479 nm. The CuII ions are involved in weak antiferromagnetic interactions within dimeric units, as evidenced by SQUID magnetometry.