Effect of the type of metal on the electrical conductivity and thermal properties of metal complexes: The relation between ionic radius of metal complexes and electrical conductivity

Synthesis, characterization, biological evaluation and molecular docking of a Schiff base ligand and its metal complexes

Condensation of 2,3-diaminopyridine with 2,4-dihyrodybenzaldehyde yielded a 4,4'-[(1E,1 ~ E)-(pyridine-2,3-diyl)bis(azanylylidene)]bis(methanylylidene)bis(benzene-1,3-diol) monobasic tridentate Schiff base ligand (HL) with an ONN donor sequence. Elemental analyses, conductivity tests, magnetic susceptibility data, FT-IR, UV-vis spectra, x-ray diffraction, and mass spectrum data of the ligand and its complexes were used for the characterization of the structures. Computational HF/3-21G calculations were performed to optimize their geometrical structures and assess their HOMO-LUMO energy gaps. The low molar conductance of the complexes indicates that they are not electrolytic. From the spectrophotometric and gravimetric analyses, the complexes (2-4) are in the ratio of 1:2, while complexes (1 & 5) (1:1) metal to ligand. 2,3-Diaminopyridine, 2,4-dihydroxybenzaldehyde, ligand (HL) and its complexes were screened for antibacterial and antifungal activities against some bacterial (Enterococcus faecalis, Salmonella typhi, and Staphylococcus epidermidis) and fungal isolates (Aspergillus flavus, Alternaria solani, and Candida albicans). The result reveals that 2,4-dihyrodybenzaldehyde has the strongest antibacterial activity among the other compounds followed by Mn(II) complex. The antimicrobial activity increases by increasing the compound concentration. To assess the inhibitory impact of ligand and its complexes on binding sites of B. cereus (PDB ID: 1FEZ), S. epidermidis (PDB ID: 3KP7), E. faecalis (PDB ID: 5V5U) and S. typhi (PDB ID: 5V2W) proteins, molecular modeling has been implemented offer a fresh concept for medication design. Molecular docking studies confirmed strong binding interactions between the metal complexes and bacterial proteins, validating their biological potential. These findings demonstrate the promising antimicrobial properties of Schiff base metal complexes, making them potential candidates for pharmaceutical and medicinal applications.

Novel Lanthanide Complexes Synthesized from 3-Dimethylamino Benzoic Acid and 5,5'-Dimethyl-2,2' Bipyridine Ligand: Crystal Structure, Thermodynamics, and Fluorescence Properties

Two isostructural lanthanide complexes were synthesized by solvent evaporation with 3-dimethylaminobenzoic acid and 5,5'-dimethyl-2,2'-bipyridine as ligands. The general formula of the structure is a [Ln(3-N,N-DMBA)3(5,5'-DM-2,2'-bipy)]2·2(3-N,N-DMHBA), Ln = (Gd(1), Tb(2)), 3-N,N-DMBA = 3-Dimethylamino benzoate, 5,5'-DM-2,2'-bipy = 5,5'-dimethyl-2,2' bipyridine. Both complexes exhibited dimeric structures based on X-ray diffraction analysis. At the same time, infrared spectroscopy and Raman spectroscopy were used to measure the spectra of the complex. A thermogravimetric infrared spectroscopy experiment was performed to investigate the thermal stability and decomposition mechanism of the complexes. Measurements of the low-temperature heat capacity of the complexes were obtained within the temperature range of 1.9 to 300 K. The thermodynamic function was calculated by heat capacity fitting. In addition, the fluorescence spectra of complex 2 were studied and the fluorescence lifetime values were determined, and the energy transfer mechanism of complex 2 was elucidated.

New Bi-Nuclear Nickel(II) Complex-Based Salen Schiff Base: Synthesis, Crystal Structure, Spectroscopic, Thermal, and Electrical Investigations

In this study, a new bi-nuclear nickel complex [Ni2HL2(EtOH)2](Cl)(EtOH) of a Schiff base ligand, 2-[3-[2-hydroxybenzylideneamino]propyliminomethyl]phenol, was synthesized and characterized using UV/Vis, IR, HRMS, and TGA/DTA analysis. The molecular structure of the obtained complex was corroborated by the single crystal X-ray diffraction technique. It was found in the complex that two molecules of the ligand coordinate with two nickel atoms through azomethine-N and phenoxy-O, resulting in 6-coordinate distorted octahedral geometry, in which two ethanol molecules occupy the axial positions. The dielectric and electrical properties of the obtained samples were studied by impedance spectroscopy at different frequencies (from 1 Hz to 1 MHz) in the temperature range 298–343 K. It is found that the electrical conductivity of the Ni(II) complex is lower than that of the free ligand H2L, suggesting that the complexation traps the charge carriers contained in the ligand.