Zinc(II) complexes derived from 2-formylpyridine nicotinoyl hydrazone as organic blocker: Syntheses, crystal architectures, Hirshfeld surface analyses and DFT studies

Abstract

In this work we report new discrete mononucler heteroleptic zinc(II) halido complexes of the type [Zn(Hal)2HL] (Hal = Cl, 1; Br, 2) and zinc(II) pseudohalido complex [Zn(NCS)2HL]·1.5MeOH (3·1.5MeOH) (HL = 2-formylpyridine nicotinoyl hydrazone). Single crystal X-ray diffraction revealed that in the structures of complexes 1–3, the Zn(II) metal atom is in a five-coordinated coordination environment and adopts a distorted square pyramidal chromophore, formed by one N2O tridentate chelator HL and two halides or thiocyanates, respectively. All complexes display a very similar molecular structure and complexes 1 and 2 are fully isostructural. Crystal packing of 1 and 2 is mainly dictated by the bifurcated N–H···Hal and linear C–H···Hal hydrogen bonds, yielding 1D polymeric chains, which additionally stabilized by intermolecular stacking interactions of the types ZnOCNN···ZnOCNN, ZnOCNN···ZnNCCN and 2-Py···3-Py. These 1D chains are interlinked into a 3D network through C–H···Hal interactions. Crystal packing of 3·1.5MeOH is constructed from centrosymmetric dimers formed through linear N–H···O and O–H···N hydrogen bonds, yielding a hydrogen bonded synthon of motif R44(16). These dimers are interlinked trough the C–S···ZnNCCN interactions, yielding 1D polymeric chains, which, in turn, are interlinked through the C–H···O bonds, and ZnNCCN···3-Py and 3-Py···3-Py stacking interactions into a 3D framework. Hirshfeld surface analysis, employed to gain additional insight into interactions responsible for the packing of complexes, and quantitative examination of 2D fingerprint plots revealed that the most important factors in the crystal packing are H···Hal and and H···H contacts in 1 and 2, and H···H, H···N, H···C and H···S contacts in 3, further supported by C···C contacts. Density function theory (DFT) calculations were performed to gather more information into structure and bonding since they play an important role in the construction of 3D supramolecular frameworks.