A novel tetranuclear nickel(II) salamo-based complex adopting two open cubic structures: synthesis, chracterization, DFT calculation, Hirshfeld analysis, and fluorescent properties

Abstract

A novel tetranuclear Ni(II) complex [Ni4(L)2(N3)4Cl(MeOH)3]·CH3COCH3 is synthesized via a symmetrical salamo-based ligand H2L, NiCl2·6H2O, and NaN3. The structure is characte­rized by elemental analyses, IR and UV-Vis spectroscopy, and X-ray diffraction analysis. The X-ray crystal analysis shows that Ni(II) atoms in the Ni(II) complex have distorted octahedral geometries. It is the key factor that the ligand containing 3-position methoxy groups gives rise to the formation of the tetranuclear Ni(II) complex. When NO3– anions are used to bridge two Ni2 atoms, there are two symmetrical open cubic structures. The Ni(II) complex forms a 3D supramolecular structure through intermolecular hydrogen bond interactions. Using the Hirshfeld surface to clarify interactions between the molecules, the percentages of C—H/H—C, O—H/H—O, and H—H/H—H contacts are calculated as 19.0 %, 15.3 %, and 54.0 %, respectively. Density functional theory (DFT) studies show that the stability of the Ni(II) complex is much higher than that of H2L. The calculation of the fluorescence titration experiment can give K = 1.05·108 M–1, which further proves the stability of the Ni(II) complex.