Mononuclear Cu(II) complex of an oxime ligand derived from N-Heterocyclic hydrazide: Synthesis, spectroscopy, electrochemistry, DFT calculations and catecholase activity

Impressive promiscuous biomimetic models of ascorbate, amine, and catechol oxidases

Copper metalloenzymes ascorbate oxidase (AOase), amine oxidase (AmOase), and catechol oxidase (COase) possess copper(II) sites of coordination, which are trimeric, homodimeric, and dimeric, respectively. Two newly mononuclear copper(II) complexes, namely, [Cu(L)(bpy)](ClO4) (1) and [Cu(L)(phen)](ClO4) (2) where HL = Schiff base, have been synthesized. UV-visible, EPR and single-crystal X-ray diffraction examinations were used to validate the geometry in solution and solid state. For complex 1, the metal exhibits a coordination sphere between square pyramidal and trigonal bipyramidal geometry (τ, 0.49). A positive CuII/I redox potential indicates a stable switching between CuII and CuI redox states. Despite the monomeric origin, both homogeneous catalysts (1 or 2) in MeOH were found to favor three distinct chemical transformations, namely, ascorbic acid (H2A) to dehydroascorbic acid (DA), benzylamine (Ph-CH2-NH2) to benzaldehyde (Ph-CHO), and 3,5-di-tert-butylcatechol (3,5-DTBC) to 3,5-di-tert-butylquinone (3,5-DTBQ) [kcat: AOase, 9.6 (1) or 2.0 × 106 h-1(2); AmOase, 13.4 (1) or 9.4 × 106 h-1 (2); COase, 2.0 (1) or 1.9 × 103 h-1 (2)]. They exhibit higher levels of AOase activity as indicated by their kcat values compared to the AOase enzyme. The kcat values for COase activity in buffer solution [5.93 (1) or 2.95 × 105 h-1 (2)] are one order lower than those of the enzymes. This is because of the labile nature of the coordinated donor, the flexibility of the ligand, the simplicity of the catalyst-substrate interaction, and the positive CuII/I redox potential. Interestingly, more efficient catalysis is promoted by 1 and 2 concerning that of other mono- and dicopper(II) complexes.

Design, synthesis, antibacterial evaluation, molecular docking and computational study of 4-alkoxy/aryloxyphenyl cyclopropyl methane oxime derivatives

A series of new 4-alkoxy/aryloxyphenyl cyclopropyl methane oxime derivatives 2(a-k) were synthesized and fully characterized by FT-IR, 1H-NMR, 13C-NMR and Mass spectrometry techniques. All the synthesized compounds 2(a-k) were assayed for in vitro antibacterial activity against a selected bacterial strain and the compound (2 h) and (2k) exerted excellent activity against Staphylococcus aureus, Escherichia coli and Salmonella typhi strains. The potency of inhibitors and possible interaction mechanism of synthetic oxime (2k) with 1GQN enzyme on Salmonella typhi was explored by molecular docking method. Amongst the all synthesized compounds, the quantum chemical calculations were done for Cyclopropyl(4-(pyridin-3-ylmethoxy)phenyl)methanone oxime (2k). The first hyperpolarizability calculation performed in different solvent such as CHCl₃, CH₂Cl₂ and DMSO and compared to the reference compound urea. In addition, natural bond orbital analysis (NBO), local reactivity descriptors, thermodynamic properties, Mulliken charges, molecular electrostatic potential (MEP), frontier molecular orbitals (FMO) analysis were explored using theoretical calculations.