Experimental and theoretical studies of new Co(III) complexes of hydrazide derivatives proposed as multi-target inhibitors of SARS-CoV-2

Cobalt(III) complexes with Schiff base ligands derived from hydrazone, (HL 1  = (E)-N'-(3,5-dichloro-2-hydroxybenzylidene)-4-hydroxybenzohydrazide, HL 2  = (E)-N'-(3,5-dichloro-2-hydroxybenzylidene)-4-hydroxybenzohydrazide (3,5-dibromo-2-hydroxybenzylidene), and HL 3  = (E)-4-hydroxy-N'-(2-hydroxy-3-ethoxybenzylidene)benzohydrazide), were synthesized and characterized by elemental analysis, Fourier transform infrared (FT-IR) spectroscopy, UV-Vis spectroscopy, and cyclic voltammetry. X-ray diffraction was used to determine the single crystal structure of the complex (1). Co(III) was formed in a distorted, very regular octahedral coordination in this complex; three pyridine moieties complete this geometry. Schiff base complexes' redox behaviors are represented by irreversible (1), quasi-reversible (2), and quasi-reversible (3) voltammograms. A density functional theory (DFT)/B3LYP method was used to optimize cobalt complexes with a base set of 6-311G. Furthermore, fragments occupying the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were investigated at the same theoretical level. Quantum theory of atoms in molecules (QTAIM) computations were also done to study the coordination bonds and non-covalent interactions in the investigated structures. Hirshfeld surface analysis was used to investigate the nature and types of intermolecular exchanges in the crystal structure of the complex (1). The capacity of cobalt complexes to bind to the major protease SARS-CoV-2 and the molecular targets of human angiotensin-converting enzyme-2 (ACE-2) was investigated using molecular docking. The molecular simulation methods used to assess the probable binding states of cobalt complexes revealed that all three complexes were stabilized in the active envelope of the enzyme by making distinct interactions with critical amino acid residues. Interestingly, compound (2) performed better with both molecular targets and the total energy of the system than the other complexes.

Crystal structure of poly[bis(μ3-(1-(3,5-di(1H-imidazol-1-yl)phenyl)-1H-imidazole-κ3N:N′:N′′)cobalt(II)] dinitrate — N,N-dimethylformamide (1/4), C42H52N18O10Co

C42H52N18O10Co, monoclinic, P21/c (no. 14), a = 11.3692(7) Å, b = 17.5938(10) Å, c = 12.1825(7) Å, β = 108.6360(10)°, V = 2309.1(2) Å3, Z = 2, R gt(F) = 0.0308, wR ref(F 2) = 0.0765, T = 120(2) K.

Crystal structure of aqua-dichlorido-(4-(((3-ethoxy-2-oxidobenzylidene)hydrazono)(oxido)methyl)pyridin-1-ium-κ3 N,O,O′)iron(III), C15H16Cl2N3O4Fe

C15H16Cl2N3O4Fe, monoclinic, P21/n (no. 14), a = 8.7419(15) Å, b = 22.717(4) Å, c = 9.6256(16) Å, β = 112.546(2)°, V = 1765.4(5) Å3, Z = 4, R gt(F) = 0.0255, wR ref(F 2) = 0.0622, T = 298 K [1–3].

The stacking interactions of bipyridine complexes: the influence of the metal ion type on the strength of interactions

The strength of the stacking interactions in the bipy complexes of nickel, palladium, and platinum, [M(CN)2 bipy]2 (M = Ni, Pd, Pt), was calculated using the ωB97xD/def2-TZVP method. The results show that for all considered geometries, interactions are the strongest for platinum, and weakest for nickel complexes, as a result of higher dispersion contributions of platinum over the palladium and nickel complexes. It was also shown that strength of interactions considerably rises with an increase of the stacking overlap area. As a consequence of the favorable electrostatic term, the strength of interactions also rises when metal atom and cyano ligands are involved in the overlap with bipy ligand. The strongest interaction was calculated in the platinum complex, for the geometry that has overlap of metal and cyano ligands with bipy ligand with an energy of -39.80 kcal mol(-1). The energies for similar geometries of palladium and nickel complexes are -34.60 and -32.45 kcal mol(-1). These energies, remarkably, exceed the strength of the stacking interactions between organic aromatic molecules. These results can be of importance in all systems with stacking interactions, from materials to biomolecules.