Co and Cu crystalline frameworks built with nitrogen heterocycle polycarboxylic acids and their catalytic property towards the reduction of p-nitrophenol

Abstract

Nitrogen heterocyclic polycarboxylic acid is a type of ligands with excellent coordination ability and rich conformations. Two metal complexes, ([Co2(L1)2(CH3COO)(H2O)3]‧(CH3COO)‧H2O (1) (HL1 = 4-[2,6-bis(pyrazin-2-yl) pyrid-4-yl]benzoic acid)) and (Cu2(L2)(H2O) (2) (H4L2 = 5-[6-(3,5-dicarboxy phenylamino)pyrid-2-ylamino]benzene-1,3-dicarboxylic acid)) were synthesized with transition metal salts and nitrogen heterocycle polycarboxylic acid ligands by solvothermal method. Both complexes were characterized by infrared and ultraviolet spectroscopy, powder X-ray diffraction analysis, and thermogravimetric analysis. The X-ray single crystal structural analysis shows that complex 1 is a one-dimensional double-chain supramolecular structure built by intermolecular hydrogen bonds. While complex 2 is a three-dimensional framework with multiple channels, where the two independent Cu(II) metals are five-coordinated to form a square pyramidal coordination geometry. In addition, in order to investigate the functional properties of the two complexes, catalytic reduction experiments towards p-nitrophenol were carried out preliminarily. The reduction efficiency above 96 % demonstrates their potential as catalysts.