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

Two inorganic–organic hybrid compounds [Zn(3,5-O2N-OBz)2(bipy)] (1) and [Zn2(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 ZnO and ZnN distances in 1 are 1.944(15) Å and 2.0435(17) Å. The aromatic rings of bipyridine are non-planer and an angle of 3.86° exists between them. Compound 2 crystallizes in space group C2/c and exists as dinuclear eight membered metallacycle with ZnZn separation of 4.202 Å. The ZnO distances in 2 range from 1.9833(19) Å to 2.091(2) Å and ZnN distances are 2.108(2) Å and 2.173(2) Å. 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 CH⋯O interaction exist in 1 whereas π–π stacking interaction between phenanthroline rings with centroid–centroid separation of 3.739 Å is operative in the crystal lattice of 2. Compounds 1 and 2 exhibit luminescence at room temperature probably arising due to intra ligand π–π∗ transition.