Synthesis, spectral, crystal structural, antimicrobial, DNA interaction and thermal behavior of some new zinc halide complexes: 3D supramolecular structure of zinc bromide complex

Abstract Three new four coordinated zinc(II) complexes have been synthesized and characterized by IR, UV, elemental analysis, 1 H and 13 C NMR and X-ray single crystal analysis. The elemental analyses of the complexes are in agreement with the general formula of ZnLX 2 wherein L = Schiff base ligand and X = Cl − , Br − and I − . Low molar conductivities in DMF indicated non-electrolyte character of all complexes. Spectroscopic studies well confirmed the coordination via azomethine nitrogens of the ligand to zinc ion. The single crystal X-ray analysis shows that ZnLBr 2 crystallizes in the triclinic crystal system with space group P 1 ¯ . It contains two crystallographically independent molecules noted as A and B, with both Zn1A and Zn1B being almost in perfect tetrahedral environments ( τ 4  = 0.94 for Zn1A and τ 4  = 0.93 for Zn1B). A detailed structural analysis shows that there are three non-classical hydrogen bondings of C–H…Br in the structure. Various C–H…π and C–H…Br interactions play an important role in stabilizing the molecular structure and then give rise to a 3D supramolecular structure of the ZnLBr 2 complex. After characterization, the Schiff base and its complexes were screened in vitro for their antibacterial and antifungal activities by disk diffusion technique. Also the ability of the complexes for DNA cleavage was studied by agarose gel electrophoresis method. Finally, thermal behavior of the complexes has been studied by thermo-gravimetry and then some activation kinetics parameters of decomposition steps were evaluated based on TG/DTG plots.