Geometry Optimization, Quantum Chemical Analysis, Visual Study of Weak Interactions, and the Antifungal Activity Studies of Some Metal (II) Complexes of 1,4-Benzodioxane-6-Carbaldehyde Thiosemicarbazone by Molecular Docking

A new Schiff-base 1,4-benzodioxane-6-carboxaldehyde thiosemicarbazone (B1) and its Zn(II), Cu(II) Ni(II) and Mn(II) complexes (ZnB1, CuB1, NiB1 and MnB1) were synthesized and characterized. The FT-IR, 1H-NMR and UV-Vis spectroscopy as well as elemental analysis, electrical conductivity measurement, thermal studies were all used to describe the structural features of the ligand and its metal (II) complexes. The metal complexes were found to exhibit octahedral geometry. Furthermore, computational studies using the DFT-B3LYP method are reported for the ligand B1 and its metal (II) complexes. The electronic property analysis revealed that, B1 serves as a strong electron donor due to its large positive energy gap (7.43Ev), indicating its propensity to participate as an electron donor in chemical reactions. A similar chemical behavior was observed with the CuB1 complex having an energy gap of 5.27 eV, suggesting its involvement, as an electron acceptor in the reaction, a bit weaker, compared to NiB1, with the highest energy gap of 7.23 eV. The ZnB1 and MnB1complexes also behaved as electron acceptors with energy gaps of 7.08 eV and 5.83 eV, respectively. The biological potential as lead compounds against Candida albicans infection was explored through molecular docking analysis. The results revealed binding affinities of −8.2 kcal/mol, −8.1 kcal/mol, −8 kcal/mol, −7.9 kcal/mol, and −7.1 kcal/mol for NiB1, CuB1, ZnB1, MnB1 complexes, and B1 ligand, respectively. These results demonstrated that the protein receptor (5BTH) and the metal complexes exhibited strong binding capacity. Comparatively, the over-the-counter medication fluconazole (access code DB00196), which was used as a benchmark to validate the results, had a theoretical binding affinity of −8.2 kcal/mol, a value equivalent to that obtained for the metal complexes. Additionally, the mean binding affinities for the examined complexes NiB1, CuB1, ZnB1, and MnB1 were noticeably higher with values of −7.93 kcal/mol, −7.77 kcal/mol, −7.54 kcal/mol, and −6.48 kcal/mol, respectively. The nickel complex demonstrated appreciable biological activity and reactivity in its interactions with the 5BTH protein, comparable to the standard drug fluconazole.