Spectroscopic investigation, thermal behavior, catalytic reduction, biological and computational studies of novel four transition metal complexes based on 5-methylthiophene Schiff base type.

Four new complexes prepared from 5-Methyl-2-carboxaldehyde-thiophene and 2,6-pyridinediamine with cobalt, nickel, copper and cadmium ions have been synthesized because of the significance of these complexes in pharmacological research and catalytic reduction. The prepared compounds were characterized using elemental analysis, mass, UV-visible, NMR and FTIR spectroscopy, as well as molar conductance, magnetic susceptibility measurements, fluorescence properties and TGA analysis. The stoichiometry mode was confirmed as 1:1 (metal: ligand) for Co, Ni and Cu complexes and 1:2 (metal: ligand) for Cd complex according to the results of the elemental and spectral studies. Furthermore, the thermal stability and luminescence properties of complexes have been studied. Thermal studies confirmed the presence of water molecules. The thermodynamic properties of the complexes were measured via the Coats-Redfern procedure. The geometric structures of the complexes were found to be octahedral around the metal ions. The optical energy gaps (Eopt) vary between 2.92 and 3.71 eV indicating that these compounds can be used as selective absorbing solar energy in photovoltaic applications. In the presence of NaBH4, the greatest reduction efficiency for the conversion of 2-NP to 2-AP was discovered to be 73-91% within 15-25 min. In vitro, high antifungal and antibacterial activity was shown by complexes than the ligand alone. The Cd(II) complex was shown to have greater activity than all of the examined microorganisms when compared to the reference drug in addition it had 4.94 µg/ml minimal inhibitory concentration against "S. aureus", "B. subtilis", and "E. coli". The bond angles, bond lengths, and quantum chemical factors of the ligand and complexes were shown in the molecular modeling using the DFT approach. The studied compounds' binding modes were confirmed using the Gaussian 09 program.

Synthesis, structural characterization, and antimicrobial evaluation of new mononuclear mixed ligand complexes based on furfural-type imine ligand, and 2,2'-bipyridine.

The present investigation goal was to investigate the chemistry of four new mononuclear mixed ligand Fe(III), Co(II), Cu(II), and Cd(II) complexes constructed from furfural-type imine ligand (L), and the co ligand 2,2'-bipyridine in addition to assessing their antimicrobial activity against some bacterial, and fungi strains. The structure of the complexes was interpreted by different spectroscopic techniques such as MS, IR, 1H NMR, UV-Vis, elemental analysis, TG-DTG, conductivity, and magnetic susceptibility measurements. The correlation of all results revealed that ligand (L) acts as a neutral ONNO tetradentate whereas the co ligand acts as a neutral NN bidentate. The coordination of the ligands with the metal ions in a molar ratio of 1:1:1 leads to formation of an octahedral geometry around the metal ions. The octahedral geometry has been validated and optimized by DFT analysis. Conductivity data showed the electrolytic nature of all complexes. The thermal stability of all complexes was deduced in addition to evaluating some thermodynamic, and kinetic parameters using Coats-Redfern method. Furthermore, all complexes in comparison to their parent ligands were tested for their biological potency against some pathogenic bacterial, and fungi strains using the paper disk diffusion method. [CdL(bpy)](NO3)2 complex revealed the highest antimicrobial activity.

Synthesis, characterization, fluorescence and catalytic activity of some new complexes of unsymmetrical Schiff base of 2-pyridinecarboxaldehyde with 2,6-diaminopyridine.

The Schiff base, 2-[(pyridin-2-ylmethylidene)amino]-6-aminopyridine (L) was synthesized by 1:1 condensation of 2-pyridinecarboxaldehyde and 2,6-diaminopyridine. The ligand and its complexes were characterized by different physicochemical studies. The analytical and spectroscopic tools indicated that the synthesized complexes have the general formulae: [M(L)Cl2]·2H2O (M=Cu(II), Ni(II) and Co(II)), [La(L)3](NO3)3·3H2O and [Sm(L)(ClO4)3]·3H2O. Vibrational spectra indicated the coordination of L to metal ions through its pyridyl and azomethine nitrogen atoms. The presence of water molecules in all reported complexes has been supported by TG/DTA studies. Kinetic and thermodynamic parameters were computed using Coats and Redfern method. The prepared ligand and its complexes exhibited intraligand (π-π∗) fluorescence and can potentially serve as photoactive materials. The catalytic activity of the complexes toward the decomposition of hydrogen peroxide was investigated. Both the ligand and its complexes have been screened for antibacterial activities.