Thiosemicarbazones-based Co(II), Ni(II), Cu(II) and Zn(II) complexes: synthesis, structural elucidation, biological activities and molecular docking

Coordination compounds of Co(II), Ni(II), Cu(II) and Zn(II) ions were synthesized from the ligands (E)-2-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)thiosemicarbazone(HL¹)/(E)-2-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-4-methylthiosemicarbazone(HL²)/(E)-2-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-N-(4-ethylphenyl)thiosemicarbazone(HL³)/(E)-2-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-N-(3-fluorophenyl)thiosemicarbazone(HL⁴) which were derived by condensing 1,3-diphenyl-1H-pyrazole-4-carboxaldehyde with derivatives of thiosemicarbazide. The characterization of synthesized compounds was carried out by numerous analytical and spectral techniques, i.e., FT-IR, ¹H NMR, ¹³C NMR, mass spectrometry, UV–Vis, SEM, ESR, powder XRD. Spectral studies illustrated that thiosemicarbazones are bonded through (NS) atoms with central metal ions conforming octahedral geometry of the complexes. The endothermic and non-spontaneous degradation pathways of the compounds were illustrated by TG–DTA studies. The in vitro antioxidant and anti-inflammatory activities were performed by DPPH and BSA assay, respectively, and the results suggested that the complexes 13, 14 having IC₅₀ values 2.08–2.01 μM and exhibited good radical scavenging power and complexes 13, 14, 16 showed good inflammation inhibition power with IC₅₀ values 8.88–10.85 μM. The in vitro antimicrobial activity was screened against S. aureus, B. subtilis, E. coli, P. aeruginosa, C. albicans, R. oryzae microbial strains, and the complexes 13, 14, 20 showed more efficiency with MIC values ranging from 0.0066 to 0.0067 μmol/mL. The overall biological activities advocate complexes 13 and 14 as compelling drugs for infectious ailments. Additionally, the recommended structure of the compounds (HL³) (3) and [Ni(L³)₂(H₂O)₂] (14) have been used to examine the most favored mode of interaction between protein and compounds via molecular docking study with Chromosome partition protein Smc (PDB ID:5H67). The main aim of this research work is to invent multifunctional medicinal drugs that include investigating the roles of pyrazole, thiosemicarbazides and transition metal complexes.

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