Zinc carboxylates containing diimine: Synthesis, characterization, crystal structure, and luminescence

Two inorganic-organic hybrid compounds [Zn(3.5-O2N-OBz)(2)(bipy)] (1) and [Zn-2(3,5-O2N-OBz)(4) (O-phen)(2)] (2) have been synthesized from methanol-dimethyl formamide medium at room temperature and characterized by analytical, spectroscopic, and single-crystal X-ray diffraction. Compound 1 crystallizes in space group C2/c and consists of discrete molecule having a distorted tetrahedral environment around zinc. 2.2'-bipyridine is bidentate whereas, 3,5-dinitrobenzoic acid is ligated in monodentate fashion. The observed Zn-O and Zn-N distances in 1 are 1.944(15) angstrom and 2.0435(17) angstrom. The aromatic rings of bipyridine are non-planer and an angle of 3.86 degrees exists between them. Compound 2 crystallizes in space group C2/c and exists as dinuclear eight membered metallacycle with Zn Zn separation of 4.202 angstrom. The Zn-O distances in 2 range from 1.9833(19) angstrom to 2.091(2) angstrom and Zn-N distances are 2.108(2) angstrom and 2.173(2) angstrom. Each Zn ion has a distorted trigonal bipyramidal coordination environment with trigonal plane is formed by a nitrogen atom N(1) and two oxygen atoms O(1), O(7), while the apical positions are occupied by oxygen atom O(8) and nitrogen atom N(2) respectively. Weak C-H ... O interaction exist in 1 whereas pi-pi stacking interaction between phenanthroline rings with centroid-centroid separation of 3.739 angstrom is operative in the crystal lattice of 2. Compounds 1 and 2 exhibit luminescence at room temperature probably arising due to intra ligand pi-pi* transition. (C) 2013 Elsevier B.V. All rights reserved.