Some divalent metal(II) complexes of novel potentially tetradentate Schiff base N,N′‐bis(2‐carboxyphenylimine)‐2,5‐thiophenedicarboxaldhyde: Synthesis, spectroscopic characterization and bioactivities

Abstract

A novel tetradentate dianionic Schiff base ligand, N,N′-bis(2-carboxyphenylimine)-2,5-thiophenedicarboxaldhyde (H 2 L) and some first row d-transition metal chelates (Co(II), Cu(II), Ni(II) and Zn(II)) were synthesized and characterized using various physicochemical and spectroscopic methods. The spectroscopic data suggested that the parent Schiff base ligand coordinates through both deprotonated carboxylic oxygen and imine nitrogen atoms. The free Schiff base and its metal chelates were screened for their antimicrobial activities for various pathogenic bacteria and fungi using the agar well diffusion method. The antibacterial and antifungal activities of all the newly synthesized compounds are significant compared to the standard drugs ciprofloxacin and nystatin. The antioxidant activities of the compounds were determined by reduction of 1,1-diphenyl-2-picrylhydrazyl and compared with that of vitamin C as a standard. DNA binding ability of the novel Schiff base and its complexes was investigated using absorption spectroscopy, fluorescence spectroscopy, viscosity measurements and thermal denaturation. The obtained results clearly demonstrate that the binding affinity with calf thymus DNA follows the order: Cu(II) complex > Ni(II) complex > Zn(II) complex > Co(II) complex >H 2 L. Furthermore, the DNA cleavage activity of the newly synthesized ligand and its metal complexes was investigated using supercoiled plasmid DNA (pUC18) gel electrophoresis.

Metal complexes of novel Schiff base derived from iron sandwiched organometallic and 4‐nitro‐1,2‐phenylenediamine: Synthesis, characterization, DFT studies, antimicrobial activities and molecular docking

“…The 1 H‐NMR spectrum of the ligand showed multiple signals within the range 6.00–7.39 ppm which assigned to the aromatic protons. These signals still appeared in the Cd(II) complex within range 6.00‐7.40 ppm . Other multiple signals with the integration corresponding to 9H at 4.22‐4.76 ppm appeared at Schiff base ligand spectrum.…”

Synthesis, Characterization, and Biological Evaluation of Cu(II) Complexes Containing Triflupromazine with Glycine and Histidine

“…The mechanisms of the studied metal complexes′ binding modes to the CT‐DNA solution were clarified further by measuring the viscosity of their mixtures containing different Cu(II) complex concentrations. Although optical and photophysical probes provide useful information regarding metal complex binding modes with DNA, more evidence is necessary to support this binding model [28] . When crystallographic and structural information is unavailable, measurements of the viscosity of metal complexes with CT‐DNA solutions are considered the most significant and least ambiguous way to assess the binding model in solution.…”

“…Although optical and photophysical probes provide useful information regarding metal complex binding modes with DNA, more evidence is necessary to support this binding model. [28] When crystallographic and structural information is unavailable, measurements of the viscosity of metal complexes with CT-DNA solutions are considered the most significant and least ambiguous way to assess the binding model in solution. The dependence of the relative specific viscosity parameter [(η/η 0 ) 1/3 ] of mixed complex-CT-DNA solutions on the corresponding [complex]/[DNA] ratio was presented in Figure 3.…”