Hydrazine-based Schiff base complexes of nickel/copper(II): synthesis, molecular and supramolecular, thermal, electrochemical, antibacterial, and computational studies
Tazrin Islam Tonny, Imdadul Haque, Mohammad Siam Abdullah, Baldeep K. Sidhu, David E. Herbert, Mohammed Enamullah
Abstract
The hydrazine-based Schiff base of 2-phenyl-1-((2-hydroxy)phenylethylidene)hydrazine (HL), synthesized from 2-hydroxy-acetophenone and 1-phenylhydrazine, reacts with nickel(II) and copper(II) acetate to give bis[2-phenyl-1-((2-oxo)phenylethylidene)hydrazinato-κ2N,O]Ni/Cu(II) (1 and 2), respectively. The molecular structure for HL shows two parallel identical molecules (A and B) with opposite orientations in the asymmetric unit of the crystal. The molecules exist in the usual enol-imine form, showing an expected intramolecular O–H···N hydrogen bond between the phenolic-H and imine-N atoms. Supramolecular packing analysis further reveals a bilayer-link via an intermolecular hydrogen bond between the imine-H and phenolate-O of symmetry-related molecules of A and B. Powder X-ray diffraction patterns suggest formation of HL, 1, and 2 with distinct phases. Electron impact (EI) mass spectra show the parent ion peak at m/z = 508 (1) and 513 (2). Thermal analysis reveals a reversible phase transformation from solid crystal to isotropic liquid for HL and an irreversible transition for 1 or 2. Cyclic voltammetry results suggest an irreversible transformation of two electron charge transfer pathway for 1 and 2 in DMF. Complex 2 exhibits significant antibacterial activity, while HL reveals moderate activity against Escherichia coli and Staphylococcus aureus bacteria. Experimental results of electronic spectra and molecular structure were authenticated by computational modeling.