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

In this article, we present the synthesis and characterization of three zinc(ii) complexes, [Zn-II(HL1)(2)] (1), [Zn-II(HL2)(2)]<middle dot>2H(2)O (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 & ctdot;Br and Br & ctdot;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 & ctdot;pi interactions in complex 3 was investigated, as these interactions are crucial for the formation of infinite 1D chains in the solid state.