Executing a Series of Zinc(II) Complexes of Homologous Schiff Base Ligands for a Comparative Analysis on Hydrolytic, Antioxidant, and Antibacterial Activities.

Six zinc(II) complexes, namely, [Zn(HLH)Cl] (), [Zn(HLH)Br] (), [Zn(HLH)(OH)I]·I (), [Zn(HL)Cl] (), [Zn(HL)Br] (), and [Zn(HL)I] () have been manufactured by using two homologous Schiff base ligands HL and HL for the purpose of perlustrating their phosphatase-like activity, antioxidant activity, and antibacterial activity. Complexes , , , and have been reported earlier by us, whereas complexes and have been synthesized and structurally characterized by regular physicochemical methods The hydrolytic property of the six complexes has been evaluated by checking the hydrolysis of the P-O bond of a widely used substrate, namely, disodium salt of (-nitrophenyl)phosphate (PNPP) in 97.5% (v/v) mixture of ,-dimethylformamide and water (DMF-water). Complexes have profound efficiency toward hydrolysis of phosphate ester bonds, and complexes and were noted to be inactive toward hydrolysis. Complex displayed the highest efficacy among the six complexes. Additionally, antioxidant and antibacterial activities of the complexes were studied thoroughly. A detailed study of their antioxidant property revealed that complex manifested superior radical scavenging activity, thus exhibiting the highest antioxidant property. The antibacterial activity was tested using four investigating bacteria, specifically ATCC19111, ATCC 700699, ATCC 23564, and ATCC 25922 by determining minimum inhibitory concentration (MIC) values using the microdilution method. Here as well, complex exhibited the highest activity to both Gram positive and Gram negative bacteria. The chemistry behind these experimental findings has been manifested by shedding light upon the structural features of the complexes. The suitable choice of ligand HL where one methylene group is less than its homologous ligand and metal precursor (ZnI) imparts a unique hydroxo-bridged molecular geometry and 2D hydrogen bonding network which in turn probably enhances the hydrolytic and biological activities of complex .