Two mononuclear zinc(II) complexes constructed by two types of phenoxyacetic acid ligands: syntheses, crystal structures and fluorescence properties

Abstract

Abstract Two new mononuclear complexes, [Zn(3-Hcpa)2(H2O)4] (1) and [Zn(3,5,6-tcpa)2(H2O)4] [Zn(3,5,6-tcpa)2(H2O)2] (2) (3-H2cpa = 3-carboxy-phenoxyacetic acid, 3,5,6-Htcpa = 3,5,6-trichloro pyridine-2-oxyacetic acid), were synthesized and structurally characterized. The single-crystal X-ray diffraction analysis showed that in 1 the ZnII ion lies on an inversion center of an octahedron formed by four aqua ligands and two carboxy oxygen atoms of two unidentate 3-Hcpa− anions in trans-arrangement. Complex 2 is a co-crystal consisting of two discrete and stereochemically different complexes: one with an octahedrally, and the other a tetrahedrally coordinated zinc center. The six-coordination about the first ZnII ion comprises four oxygen atoms from water (H2O) molecules and two from the carboxy groups of monodentate trans-related 3,5,6-tcpa− ligands. The four-coordination about the second ZnII ion is comprised of two H2O ligands and two unidentate carboxy oxygen atoms from 3,5,6-tcpa− ligands. O–HLO hydrogen bond and/or ClLCl halogen bond interactions play an important part in construction of the three-dimensional (3D) networks for 1 and 2. The photoluminescence spectra reveal that both 1 and 2 display luminescent properties in the violet region.