Samir M. El-Medani

Molybdenum and Tungsten Carbonyl Complexes With N2 Schiff Base Donors: Syntheses, Spectral, Electrochemical, Thermal, Catalytic Epoxidation, and Biological Activity Studies

Thermal reactions of Mo(CO)6 with the Schiff base 4-nitro-N-(pyridine-2-yl-methylene)aniline (NPMA) in THF in absence and presence of triphenyl phosphine (PPh3), pyridine (py) or thiourea (Tu) gave the four carbonyl complexes, [Mo(CO)4(NPMA)] (1), [Mo(CO)3(NPMA)(PPh3)] (2) [Mo2(O)2(CO)2(NPMA)2(Py)2] (3), and [Mo2(O)2(CO)4(NPMA)(Tu)2] (4), respectively. Thermal reaction of W(CO)6 with NPMA in THF gave the two complexes [W2(O)6(NPMA)] (5) and [W2(O)6(NPMA)(Py)2] (6) in absence and presence of pyridine, respectively, while under sunlight irradiation the complex [W2(CO)6(NPMA)2] (7) was isolated. Magnetic susceptibility, elemental analyses, and IR, mass, and 1H NMR spectroscopy were studied. Thermal, cyclic voltammetry, catalytic epoxidation, and biological activity were also investigated.

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.

DFT calculations, spectroscopic, thermal analysis and biological activity of Sm(III) and Tb(III) complexes with 2-aminobenzoic and 2-amino-5-chloro-benzoic acids

The complexes of Sm(III) and Tb(III) with 2-aminobenzoic acid (anthranilic acid, AA) and 2-amino-5-chlorobenzoic acid (5-chloroanthranilic acid, AACl) were synthesized and characterized based on elemental analysis, IR and mass spectroscopy. The data are in accordance with 1:3 [Metal]:[Ligand] ratio. On the basis of the IR analysis, it was found that the metals were coordinated to bidentate anthranilic acid via the ionised oxygen of the carboxylate group and to the nitrogen of amino group. While in 5-chloroanthranilic acid, the metals were coordinated oxidatively to the bidentate carboxylate group without bonding to amino group; accordingly, a chlorine-affected coordination and reactivity-diversity was emphasized. Thermal analyses (TGA) and biological activity of the complexes were also investigated. Density Functional Theory (DFT) calculations at the B3LYP/6-311++G (d,p)_ level of theory have been carried out to investigate the equilibrium geometry of the ligand. The optimized geometry parameters of the complexes were evaluated using SDDALL basis set. Moreover, total energy, energy of HOMO and LUMO and Mullikan atomic charges were calculated. In addition, dipole moment and orientation have been performed and discussed.

Spectroscopic, DFT, biological, DNA-binding and antioxidant studies of some metal chelates with a novel thiazole-derived Schiff base

Abstract Thermal reactions of Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Ru(III) metal ions with a novel Schiff base ligand (HL) derived from the condensation of 2-aminothiazole and 2-hydroxy-1-naphthaldehyde resulted in the formation of a series of metal complexes, [Co(L)2(H2O)2]·2H2O (1), [Ni(L)(CH3COO)(H2O)2] (2), [Cu(L)2(H2O)2] (3), [Zn(L)2] (4), [Cd(L)(CH3COO)]·2H2O (5), and [Ru(L)2(H2O)2]Cl (6). The ligand and its complexes were characterized by means of elemental and thermal analyses, molar conductance, and magnetic moment measurements along with different spectroscopic techniques. The structure of the ligand was determined by X-ray crystal structure analysis and revealed that it crystallized in the orthorhombic space group P21cn with a Z value of 4. Theoretical calculations based on accurate DFT approximations were used to verify the structures of ligand and complexes. The relative reactivities were estimated using chemical descriptors analysis. The biological activities of the compounds were examined. The antioxidant activity against DPPH radical was evaluated in vitro by using spectrophotometric methods; the experiments showed potent antioxidant activity. Also, the interaction of the reported compounds with calf-thymus DNA (CT-DNA) by different techniques revealed that the complexes could bind to CT-DNA by intercalative mode. GRAPHICAL ABSTRACT