Differentiating intramolecular spodium bonds from coordination bonds in two polynuclear zinc(ii) Schiff base complexes

Abstract

Two new zinc(II) complexes, [{N(CN)₂}Zn(L¹)Zn{μ-1,5-N(CN)₂}]₂ (1) and [{μ-1,5-N(CN)₂}{N(CN)₂}Zn(L²)Zn{μ-1,5-N(CN)₂}]_n (2) {H₂L¹ = 2,2′-[(2,2-dimethyl-1,3-propanediyl)bis(nitrilomethylidyne)]bis[6-methoxyphenol] and H₂L² = 2,2′-[(2,2-dimethyl-1,3-propanediyl)bis(nitrilomethylidyne)]bis[6-ethoxyphenol]} have been synthesized and characterized. The structures of both complexes have been confirmed by X-ray crystallography. A subtle difference in the aromatic ring of the Schiff base ligand (6-ethoxy in H₂L² and 6-methoxy in H₁L¹) has a strong influence on the final solid state structure. In addition, the O-atom of the methoxy groups in 1 forms stronger intramolecular spodium bonds with Zn(II) than the O-atom of the ethoxy group in 2. This has been analysed using density functional theory (DFT) calculations and a combination of the quantum theory of atoms in molecules (QTAIM) and noncovalent interaction (NCI) plot index computational tools.