Computational Studies of 4-Formylpyridinethiosemicarbazone and Structural and Biological Studies of Its Ni(II) and Cu(II) Complexes

Abstract

To understand the stability, chelation behaviour, and biological activity of 4-Formylpyridinethiosemicarbazone (H4FPT), it is important to recognize its interactive geometry. Hence, computational studies on geometrically optimized structures of thione and thiol forms of H4FPT were performed. Binary metal complexes of the ligand, H4FPT (L) with the Ni(II) and Cu(II) metal ions (M), were synthesized and characterized by various spectroanalytical techniques as elemental analysis, molar conductance, magnetic susceptibility measurements, LC-MS, TGA, IR, UV-Visible, ESR, and powder XRD. Elemental analysis, LC-MS, and TGA studies indicate 1:2 (ML2) composition for mononuclear Ni(II) complex and 1:1 (ML) composition for dinuclear Cu(II) complex. Electronic absorption titrations, fluorescence quenching studies, and viscosity measurements suggest intercalative mode of binding of the complexes with calf thymus DNA (CT-DNA). These complexes also promote hydrolytic cleavage of plasmid pBR322. The ligand (H4FPT) and its complexes showed moderate-to-good activity against Gram-positive and Gram-negative bacterial strains. The DPPH radical scavenging studies showed antioxidant nature of both complexes.

Synthesis, Characterization and Biological Activity of Novel Cu(II) Complexes of 6-Methyl-2-Oxo-1,2-Dihydroquinoline-3-Carbaldehyde-4n-Substituted Thiosemicarbazones

“…These results are in agreement with the theoretical calculations carried out on similar TSCs [97], which have shown that the thione tautomeric forms are stable, even in the presence of a solvent (MeOH). However, recent computational studies on 4-formylpyridine-TSC derivatives proved that both the thiol and thione forms are stable [98]. The 1 H NMR spectra of H2L1 showed the presence of two distinct signals for -(C=S)NH2 protons at 8.09 and 8.31 ppm, respectively, the latter presenting a NOESY correlation with the N(2)H proton at 11.64 ppm and suggested an E conformation.…”

“…These results are in agreement with the theoretical calculations carried out on similar TSCs [97], which have shown that the thione tautomeric forms are stable, even in the presence of a solvent (MeOH). However, recent computational studies on 4-formylpyridine-TSC derivatives proved that both the thiol and thione forms are stable [98].…”

Synthesis, Structural Characterisation, and Electrochemical Properties of Copper(II) Complexes with Functionalized Thiosemicarbazones Derived from 5-Acetylbarbituric Acid

“…Elemental analyses were performed with a Fisons-Carlo Erba 1108 microanalyser (CARLO ERBA Reagents SAS, Chaussée du Vexin, Val-de-Reuil, France). 1 H and 13 C NMR spectra were obtained as DMSO-d 6 solutions with a Varian Mercury 300 instrument (Varian Medical Systems, Inc, Palo Alto, CA, USA). IR spectra were recorded as KBr disks (4000-400 cm −1 ) or polyethylene-sandwiched Nujol mulls (500-100 cm −1 ) with a Bruker IFS-66v spectrophotometer (Bruker Corporation, Billerica, MA, USA).…”

“…However, they can also be coordinated in a tridentate or tetradentate manner, among other possibilities, when the aldehyde is functionalized or it is a bis-thiosemicarbazone. Clearly, the biological activity of the resulting complexes will be affected by the type of metal center and functionalization [13].…”