Synthesis, characterization, crystal structure, thermal analysis of a new co-crystal supramolecular dinuclear zinc (II) complex containing chelidamate ligand

Abstract

A new co-crystal supramolecular dinuclear compound of Zn(II) namely (dapH)2(hypydcH)2·[Zn2(hypydc)2(H2O)6]·2H2O (1), where [hypydcH2 = 4-hydroxypyridine-2,6-dicarboxylic acid (chelidamic acid), dap = 3,4-diaminopyridine] has been synthesized and characterized by elemental analysis, spectral (IR, UV–Vis), thermal (TG/DTG) analysis and single crystal X-ray diffraction. The zinc (II) cation sits on a center of inversion. In the crystal structure of 1, chelidamate dianions have been coordinated to ZnII ion in a three dentate fashion through two oxygen and one nitrogen atoms from (hypydc)2– ligands. Furthermore, dicarboxylic groups link two zinc (II) centers to each other via oxygen atoms of carboxylic groups, also three water molecules coordinated to metal centers. Consequently, each Zn(II) atom is seven-coordinate and demonstrate approximately pentagonal-bipyramidal ZnNO6 coordination geometry. The metal fragments are linked via the central four-membered Zn2O2 ring. Surprisingly, in 1 a proton transfer ion pair of chelidamic acid and 3,4-diaminpyridine crystallized accompanied with neutral dinuclear complex of Zn(II). Interestingly, the structural analysis illustrates that anionic and cationic fragment accompanied with neutral dinuclear complex and uncoordinated water molecules assemble the crystal structure of 1 into a fascinating supramolecular architecture.