Synthesis, structural characterization, and theoretical analysis of novel zinc(ii) schiff base complexes with halogen and hydrogen bonding interactions

Abstract

In this article, we present the synthesis and characterization of three zinc(II) complexes, [Zn^II(HL¹)₂] (1), [Zn^II(HL²)₂]·2H₂O (2) and [Zn^II(HL³)₂] (3), with three tridentate Schiff base ligands, H₂L¹, H₂L², and H₂L³. The structures of the complexes were confirmed by single-crystal X-ray diffraction analysis. DFT calculations were performed to gain insights into the self-assembly of the complexes in their solid-state structures. Complex 1 exhibits dual halogen-bonding interactions (Br⋯Br and Br⋯O) in its solid-state structure, which have been thoroughly investigated through molecular electrostatic potential (MEP) surface calculations, alongside QTAIM and NCIPlot analyses. Furthermore, complex 2 features a fascinating hydrogen-bonding network involving lattice water molecules, which serves to link the [Zn^II(HL²)₂] units into a one-dimensional supramolecular polymer. This network has been meticulously examined using QTAIM and NCIplot analyses, allowing for an estimation of the hydrogen bond strengths. The significance of H-bonds and CH⋯π interactions in complex 3 was investigated, as these interactions are crucial for the formation of infinite 1D chains in the solid state.