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 (H 2 O) 4 ] ( 1 ) and [Zn(3,5,6-tcpa) 2 (H 2 O) 4 ] [Zn(3,5,6-tcpa) 2 (H 2 O) 2 ] ( 2 ) (3-H 2 cpa = 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 Zn II 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 Zn II ion comprises four oxygen atoms from water (H 2 O) molecules and two from the carboxy groups of monodentate trans -related 3,5,6-tcpa − ligands. The four-coordination about the second Zn II ion is comprised of two H 2 O 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.