Synthesis, Crystal structure, Hirshfeld surface interactions, anti-corrosion analysis, DFT calculations, Docking studies and evaluation of the antioxidant activity of a new zwitterion Schiff base

The title compound Schiff base (SB) named: (6E)-3-benzyloxy-6- [ [ [2-hydroxy-1,1-bis(hydroxymethyl)ethyl] amino]methylene]cyclohexa-2,4-dien-1-one(I) (C18 H21 N O5), was synthesized via the reaction of 4-benzyloxy2-hydroxy-benzaldehyde with 2-amino-2-(hydroxymethyl)propane-1,3-diol (Trizma)and characterized by singlecrystal diffraction XRD, infrared spectra, 1H and 13C NMR spectroscopy. It crystallizes as a zwitterion, (E)-5(benzyloxy)-2-(((1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl)iminio)methyl)phenolate (II), with the phenolic H atom having migrated to the imino group. Additionally,Hirshfeld surface analysis (HS), two-dimensional fingerprint plots and energy frameworks of II were calculated to quantify the interatomic interactions present in the crystal.The antioxidant activity of the synthesized compound was evaluated by five tests: ABTS, DPPH, OpH, SNP and reducing power activity. Furthermore, molecular docking calculations were performed for SB compound at the active site of mushroom tyrosinase (PDB ID:2Y9X) to determine the binding affinity between the title compound and receptor protein. Results reveal a great affinity (-6.16 kcal/mol) of the SB to the protein that is mainly dominated by hydrogen bonds. In this work, experimentally, the assessment of the anti-corrosion ability of this compound by different methods showed excellent inhibition. On the other hand, anti-corrosion potentials of title compound have been investigated using density functional theory (DFT) in gas and solvent phases. Chemical reactivity descriptors like global hardness (q), chemical potential (u), electronegativity (x), electrophilicity (co) and number of transferred electrons (AN) were computed at coB97XD with 6-311+g(d) basis set. The local reactive sites on this compound were studied using Fukui indices, local philicity index and dual descriptor. The quantum chemical calculation suggests a good charge transfer tendency from the title compound to the low-lying vacant d-orbitals of iron (The average value of charge transfer is ANIII/Fe.approximate to 2.21 and ANIII/Cu.approximate to 0.07). The C7 atom is the nucleophilic sites (Af(r)C7 approximate to 0.25) on the inhibitor for effective interaction on the metal surface as shown by local reactive descriptor in gas and solvent. Furthermore, the results obtained from DFT and TD-DFT studies are in excellent agreement with experimental data (structure geometry (RMS Error approximate to 0.3 angstrom), optical properties (lambda exp-Cal approximate to 18 nm) and inhibition efficiencies).