Antibacterial metal complexes of o‐sulfamoylbenzoic acid: Synthesis, characterization, and DFT study

Abstract

Herein, antibacterial transition metal complexes of ML2 type having o‐sulfamoylbenzoic acid as ligand were synthesized from saccharin. All characterization techniques confirmed the syntheses of non‐ionic transition metal MnII (3), CoII (4), NiII (5), CuII (6), and ZnII (7) complexes, where mono‐anionic o‐sulfamoylbenzoic acid acts as a weak field ligand. The FT‐IR, elemental analysis, and magnetic susceptibility studies suggested octahedral and square pyramidal geometries depending on the nature of metal ions. Biological activity of these complexes was studied by using six bacterial strains. Interestingly, the bacterial strains Escherichia coli and Klebsiella aerogenes were inhibited to the maximum level by 6. Among aforementioned five complexes, 4 and 6 were found in crystalline form. Apart from experimental study, DFT study was also performed for entitled complexes at the M06/6‐311G(d,p) level. A comparative investigation was performed for geometrical parameters and vibrational analysis, and an agreement was obtained. Natural bonding orbital investigations expressed larger value of stabilization energy 21 kcal/mol for 3, 4, and 6 while 42 kcal/mol for 5 and 7. Furthermore, global reactivity findings also disclosed higher value of hardness (2.44–3.09 eV) for entitled chromophores, hence, showed more stability. Moreover, frontier molecular orbital (FMO) findings revealed a larger band gap (4.48–6.19 eV) with higher values of LUMO found for all complexes.