Hydrolytic cleavage of Schiff bases by [RuCl2(DMSO)4]

Saccharified Uranyl Ions: Self-Assembly of UO2 2+ into Trinuclear Anionic Complexes by the Coordination of Glucosamine-Derived Schiff Bases

The reaction of UO2 (OAc)2  ⋅ 2H2 O with the biologically inspired ligand 2-salicylidene glucosamine (H2 L1 ) results in the formation of the anionic trinuclear uranyl complex [(UO2 )3 (μ3 -O)(L1 )3 ]2- (12- ), which was isolated in good yield as its Cs-salt, [Cs]2 1. Recrystallization of [Cs]2 1 in the presence of 18-crown-6 led to formation of a neutral ion pair of type [M(18-crown-6)]2 1, which was also obtained for the alkali metal ions Rb+ and K+ (M=Cs, Rb, K). The related ligand, 2-(2-hydroxy-1-naphthylidene) glucosamine (H2 L2 ) in a similar procedure with Cs+ gave the corresponding complex [Cs(18-crown-6)]2 [(UO2 )3 (μ3 -O)(L2 )3 ([Cs(18-crown-6)]2 2). From X-ray investigations, the [(UO2 )3 O(Ln )3 ]2- anion (n=1, 2) in each complex is a discrete trinuclear uranyl species that coordinates to the alkali metal ion via three uranyl oxygen atoms. The coordination behavior of H2 L1 and H2 L2 towards UO2 2+ was investigated by NMR, UV/Vis spectroscopy and mass spectrometry, revealing the in situ formation of the 12- and 22- dianions in solution.

Palladium (II)-Salan Complexes as Catalysts for Suzuki-Miyaura C-C Cross-Coupling in Water and Air. Effect of the Various Bridging Units within the Diamine Moieties on the Catalytic Performance

Water-soluble salan ligands were synthesized by hydrogenation and subsequent sulfonation of salens (N,N'-bis(slicylidene)ethylenediamine and analogues) with various bridging units (linkers) connecting the nitrogen atoms. Pd (II) complexes were obtained in reactions of sulfosalans and [PdCl₄]^2-. Characterization of the ligands and complexes included extensive X-ray diffraction studies, too. The Pd (II) complexes proved highly active catalysts of the Suzuki-Miyaura reaction of aryl halides and arylboronic acid derivatives at 80 °C in water and air. A comparative study of the Pd (II)-sulfosalan catalysts showed that the catalytic activity largely increased with increasing linker length and with increasing steric congestion around the N donor atoms of the ligands; the highest specific activity was 40,000 (mol substrate) (mol catalyst × h)^-1. The substrate scope was explored with the use of the two most active catalysts, containing 1,4-butylene and 1,2-diphenylethylene linkers, respectively.

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.

Synthesis, spectroscopic, antimicrobial, DNA binding and cleavage studies of some metal complexes involving symmetrical bidentate N, N donor Schiff base ligand

The Schiff base ligand, N,N'-bis-(4-isopropylbenzaldimine)-1,2-diaminoethane (L), obtained by the condensation of 4-isopropylbenzaldehyde and 1,2-diaminoethane, has been used to synthesize the complexes of the type [ML(2)X(2)] [M = Co(II), Ni(II) and Zn(II); X = Cl and OAc]. The newly synthesized ligand (L) and its complexes have been characterized on the basis of elemental analyses, mass, (1)H and (13)C-NMR, molar conductance, IR, UV-vis, magnetic moment, CV and thermal analyses, powder XRD and SEM. IR spectral data show that the ligand is coordinated to the metal ions in a bidentate manner. The geometrical structures of these complexes are found to be octahedral. Interestingly, reaction with Cu(II) ion with this ligand undergoes hydrolytic cleavage to form ethylenediamine copper(II) complex and the corresponding aldehyde. The antimicrobial results indicate that the chloro complexes exhibit more activity than the acetato complexes. The complexes bind to CT-DNA by intercalation modes. Novel chloroform soluble ZnL(2)Cl(2) complex exhibits tremendous antimicrobial, DNA binding and cleaving properties.

Spectrometric study of tautomeric and protonation equilibria of o-vanillin Schiff base derivatives and their complexes with Cu(II)

Electronic absorption and emission properties of a series of Schiff bases derived from 2-hydroxy-3-methoxybenzaldehyde and 2-aminopyridine, 2,3-diaminopyridine, 2,6-diaminopyridine, or 3-aminomethylpyridine were studied in solvents of different polarities. The interconversion of the enolimine to the ketoamine tautomeric form was observed for compound 1, 6-methoxy-2-(3-pyridylmethyliminomethyl)phenol, and the corresponding equilibrium constant was estimated in several solvents. Protonation constants of all the investigated compounds were determined spectrophotometrically in the methanol/water 1/4 system. The effect of copper(II) ions on absorption and on the emission spectra of these ligands was examined in the buffered dioxane/water 1/1 system (pH 5.8). Strong complexation of Cu(II) and formation of a 1:1 complex were observed for the bis-Schiff base derived from 2,3-diaminopyridine. The complex of copper(II) with compound 1 was isolated and characterized by elemental analysis, magnetic susceptibility measurement, UV-vis and IR spectrometry.