Characterization and crystal structures of zinc(II) and cadmium(II) complexes with D-(-)-quinic acid

Zinc(II) and cadmium(II) complexes with D-(-)-quinic acid (H(5)quina), [Zn( H(4)quina)(2)] and [Cd(H(4)quina)(2)] (H2O), have been prepared and charact erized by means of infrared spectra and thermal analysis. Crystal structure s of both complexes have been determined by X-ray diffraction. The crystal of [Zn(H(4)quina)(2)] is monoclinic with the space group C2. The zinc(II) a tom is in a trigonal antiprism geometry, ligated by two carboxylato oxygen atoms and two hydroxyl oxygen atoms from two molecules of quinic acid, and two carboxylato oxygen atoms of two neighboring molecules. This complex con sists of polymers bridged by a carboxylato oxygen atom. The crystal of [Cd( H(4)quina)(2)](H2O) is monoclinic with space group P2(1). The cadmium atom is in a monocapped trigonal prism geometry. There are two types of quinic a cid in this complex. One quinic acid molecule chelates with a cadmium atom by a carboxylato oxygen atom and a hydroxyl oxygen atom, and coordinates wi th a neighboring cadmium atom by a carboxylato oxygen atom. The other quini c acid molecule chelates with a cadmium atom by two oxygen atoms of a carbo xyl group, and chelates with a neighboring cadmium atom by two hydroxyl oxy gen atoms. This complex consists of polymers bridged by carboxylato oxygen atoms and hydroxyl oxygen atoms. (C) 1999 Elsevier Science Inc. All rights reserved.