Crystal Structures of Two Aromatic Zinc(II) Carboxylates: [Zn(4-Chlorosalicylato)2(H2O)4]·2theophylline·(H2O)2 and Unique [Zn(5-Chlorosalicylato)2(isonicotinamide)2(H2O)

Abstract

The crystal structures of two zinc(II) 4-chloro- and 5-chlorosalicylate complexes, [Zn(4-ClC6H3-2-(OH)COO)2(H2O)4]·2tph·(H2O)2 (I) and [Zn(5-ClC6H3-2-(OH)COO)2(ina)2(H2O)] (II), where tph is theophylline and ina is isonicotinamide, have been determined using X-ray diffraction methods. Crystals of both (I) and (II) are triclinic, space group P-1, with Z = 1 in a cell with a = 7.2220(3), b = 8.59700(10), c = 16.0210(5) A, α = 75.990(2), β = 83.959(2), γ = 68.455(2)°, V = 897.54(5) A3 (I) and with Z = 2 in a cell with a = 11.4148(11), b = 11.5327(10), c = 12.0685(13) A, α = 63.458(6), β = 87.547(8), γ = 89.387(7)°, V = 1419.9(2) A3 (II). The coordination environment of the zinc(II) atom of compound (I) consists of two unidentate carboxylate oxygen atoms and four oxygen atoms of aqua ligands, forming a distorted octahedral configuration. Two theophylline molecules and the remaining water molecules are bound only by hydrogen bonds. The Zn atom of compound (II) is pentacoordinated with two unidentate carboxylate oxygen atoms, two pyridine nitrogen atoms of isonicotinamide ligands, and the oxygen atom of the aqua ligand, forming a distorted configuration between square pyramid and trigonal bipyramid. In both complexes intramolecular O–H···O hydrogen-bonding interactions are present. In the crystal structures, molecules are linked by intermolecular O–H···O and N–H···O hydrogen bonds. The structures are analyzed and compared to the similar Zn(II) complexes, with the chromophores ZnO6 and ZnO3N2. Two zinc(II) 4-chloro- and 5-chlorosalicylate complexes, [Zn(4-ClC6H3-2-(OH)COO)2(H2O)4]·2tph·(H2O)2 (I) and [Zn(5-ClC6H3-2-(OH)COO)2(ina)2(H2O)] (II) (tph = theophylline, ina = isonicotinamide) have been prepared and characterized by elemental analysis, IR spectroscopy and their crystal structures have been determined using X-ray diffraction methods.