We report on an interaction of a mixture of cyclohexylamine and salicylaldehyde with Ni(OAc)2 conducted in EtOH, which allowed to produce a novel discrete trinuclear heteroleptic complex [Ni3L3L'(OAc)2]·2EtOH (1·2EtOH), where L is the monodeprotonated anion of N-cyclohexylsalicylideneimine (HL) and L' is the monodeprotonated anion of salicylaldehyde, in the form of green prismatic crystals. Notably, the structure of complex 1 differs significantly from the previously reported discrete mononuclear homoleptic complex [NiL2], which was obtained by reacting HL with Ni(OAc)2·4H2O in the same solvent (EtOH). Complex 1·2EtOH was studied by IR spectroscopy, and its composition and crystal structure were revealed using the elemental analysis data and single crystal X-ray diffraction. Phase purity of the solid material was examined by powder X-ray diffraction. In the molecular structure of 1, three ligands L, the ligand L' and one of the acetate anions exhibit bridging coordination modes linking three nickel(II) cations, while the second acetate anion exhibits a terminal coordination mode. Both oxygen atoms of the latter anionic ligand are involved in the O–H···O hydrogen bonds with the ethanol molecules. Optical properties of solutions of 1 in CH2Cl2, MeOH and DMSO were studied using UV–vis spectroscopy, while optical properties of 1·2EtOH in the solid state were revealed using the diffuse reflectance spectroscopy. DFT calculations were performed to analyze potential Ni···Ni interactions within the trinuclear system, and quantum theory of atoms in molecules (QTAIM) analysis was employed to compare Ni–O(phenol) and Ni···O(acetate) coordination bonds. A potential inhibitor activity of complex 1 towards the SARS-CoV-2 Omicron S-open-2 and S-close proteins was predicted using a molecular docking approach, which results were compared to those revealed for complexes [NiLig]2 and [NiLig]2·[NiLig] (H2Lig = N,N'-bis(2‑hydroxy-1-naphthylmethylene)ethylenediamine), both exhibiting an unusually short Ni···Ni separations.
