Heteroleptic Metal Complexes of a Pyrimidinyl Based Schiff Base Ligand Incorporating 2,2′-Bipyridine Moiety: Synthesis, Characterization, and Biological Studies

Abstract

A sequence of transition metal complexes of Mn(II), Co(II), Ni(II), and Cu(II) incorporating a novel pyrimidinyl based Schiff base ligand, 2-(4,6-dimethylpyrimidin-2-ylamino)naphthalene-1,4-dione (HL) and 2,2 ′-bipyridine has been synthesized and characterized using elemental, magnetic, conductance, infrared (FT-IR), nuclear magnetic resonance (1 Hand 13 C-NMR), electronic (UV-Vis), electrospray ionization mass spectrometry (ESI-MS), thermographic analysis (TGA), and molecular docking studies. The acquired results were consistent with the adoption of the chemical formula, [M(X)(L)(Y)]•nH 2 O (where M = Mn, Co, Ni, and Cu; L = Schiff base; X = 2,2 ′-bipy; Y = OAc; and n = 0,1) for the metallic complexes. HL ligand acts as a bidentate chelator and coordinates to metallic ion centre through carbonyl oxygen atom and deprotonated imide nitrogen. Similarly, 2,2 ′-bipy acts as a non-ionic bidentate chelator coordinating to metallic ion center via two nitrogen atoms. The mixed ligand complexes were appraised against pathogenic strains: S. aureus, P. aeruginosa, E. coli, B. cereus, P. mirabilis, K. oxytoca, A. niger, A. flevus, and R. Stolonifer. The antimicrobial studies gave moderate-good activity. Molecular docking studies on these compounds were done to indicate binding interactions between the compounds and adopted drug targets. Additionally, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity of the compounds were determined at different concentrations. The antioxidant study showed good radical scavenging abilities.

Schiff base metal complex as a potential therapeutic drug in medical science: A critical review

“…For this study, they seeded 0.2 mL of 24 h grown microbial culture in each plate and bore wells with the sterile cork of 7 mm diameter and introduced the tested samples prepared at 10 mg/mL concentration in DMSO. The study revealed moderate to some very good antimicrobial activity, even surpassing the control drug's activity several times [52]. The antioxidant capacity of all the synthesized complexes was good and the ligand showed even better activity than the standard ascorbic acid. )…”

“…Heteroleptic metal complexes of pyrimidinyl-based Schiff base ligand also possess good antimicrobial activity against various pathogenic bacteria and fungi. In a previous study, Festus et al (2019) synthesized Mn(II), Co(II), Ni(II), and Cu(II) complexes of novel Schiff base ligand (23) (2-(4,6dimethylpyrimidin-2-ylamino)naphthalene-1,4dione and 2,2′-bipyridine) and appraised them antimicrobial evaluation against S. aureus, E. coli, P. aeruginosa, B. cereus, P. mirabilis, K. oxytoca, A. niger, A. flevus, and R. stolonifer organisms following the agar-well diffusion method. For this study, they seeded 0.2 mL of 24 h grown microbial culture in each plate and bore wells with the sterile cork of 7 mm diameter and introduced the tested samples prepared at 10 mg/mL concentration in DMSO.…”

New Heteroleptic 3D Metal Complexes: Synthesis, Antimicrobial and Solubilization Parameters

“…Furthermore, NiL 1 Gly, CoL 3 Gly, NiL 3 Gly demonstrated much-enhanced susceptibility as compared to ligands and glycine against B. cereus . These improved antibacterial activities of complexes may be attributed to the involvement of hyper-conjugation and induction of greater lipo solubility [ 22 ]. The polarity of metal ions diminished and caused delocalization of π-electrons, which, in turn, favored the penetration of complexes through the bacterial membrane, subsequently enhancing their activity [ 23 , 24 ].…”

“…Studies on antibacterial activity of synthesized ligands and metal complexes were performed with slight changes in the reported protocol [ 22 ]. Six microbial strains viz.…”

“…The in vitro antifungal activities of all ligands and metal complexes were evaluated by employing the disc technique [ 22 ]. The antifungal screening against A. niger , A. flevus and R. Stolonifer were determined by potato dextrose agar (PDA) media prepared from washed-sliced skinned potatoes (250 g), dextrose (25 g), and agar (25 g) mixed in 1250 mL of distilled water.…”