Oxotungsten(VI) complexes with schiff bases obtained from salicylaldehyde and various amines

Oxotungsten(VI) complexes have been synthesized with bi-, ter- and quadri-dentate Schiff bases obtained from salicylaldehyde and various amines. The following types of complexes have been isolated: (1) WOCl₃ (bidentate); (2) WOCl₂(terdentate); (3) WO₂(terdentate); (4) WO₂(terdentate). L, L being N,N-dimethylformamide (DMF) and pyridine (py). With quadridentate N,N′-ethylenebis(salicylaldiminate), WOCl₃(quadridentate)_{$\text{1}\text{2}$} has been obtained. Results of infrared spectra and electronic spectra are presented and possible structures of these complexes are discussed.     

Metal complexes with unsymmetrical tetradentate schiff bases

A simple method for the synthesis of 1-amino-3-aza-4-methylhept-4-ene-6-one is presented. The dominant tautomeric form of the compound in CDCl₃ has been established. Using this compound eight (five new) unsymmetrical tetradentate Schiff bases and their nickel(II), palladium(II) and copper(II) complexes have been prepared and characterized by various physical techniques. Data for the complexes indicate that they are all of square-planar geometry. High resolution ¹H nmr studies, including lanthanide shift reagents on nickel and palladium chelates, allowed us to assign almost all proton resonances. Data for nickel(II) and palladium(II) chelates with 1-(2′-hydroxyphenyl)-1-phenyl-2,5-diaza-6-methylnona-1,6-diene-8-one are consistent with the ketoenamine structure of both the acetylacetone and hydroxybenzophenone portions of the molecules. Good resolved nitrogen hyperfine splitting was observed in the esr spectrum of the copper complex with the aforementioned ligand.     

Polynuclear complexes of lanthanides with nickel and copper schiff bases as ligands

Polynuclear complexes of lanthanide(III) nitrates, thiocyanates, chlorides and perchlorates with N,N′- 1,3-propylen-bis(salicylideniminato)nickel(II) and N,N'?1,3-propylen-bis(salicylideniminato)copper(II) have been prepared and characterized by vibrational and electronic spectra, magnetic susceptibility, molar conductivity and thermal analysis measurements. Reliable information relating to the lanthanide- ligand bondings and geometries of the complexes have been inferred from infrared and electronic spectral data.     

Biological activity of some schiff bases and their metal complexes

Schiff bases derived from salicylaldehyde and 2-substituted aniline and their metal chelates with Cu(II), Ni(II), and Co(II) ions were synthesized and screened for the antiinflammatory and antiulcer activity. The compound salicylidene anthranilic acid (SAA) was found to possess the antiinflammatory and antiulcer activity. The copper complexes showed an increased antiulcer activity. The SAA is perhaps acting by influencing prostaglandin biosynthesis.     

Metal complexes of the schiff bases 2-pyridinylhydrazine and 2-quinolinyl-hydrazine with 2-pyridinecarboxaldehyde N-oxide,including some N-oxide-bridged antiferromagnetic complexes of cobalt(II) and nickel(II)

Metal complexes of 2-pyridine carboxaldehyde 2′-pyridinylhydrazone 1-oxide (poph) and 2-pyridinecarboxaldehyde 2′-quinolinylhydrazone 1-oxide (poqh) are reported with copper(II), nickel(II), cobalt(II), iron(II) and manganese(II). Each ligand appears to function as an ONN donor, via the pyridine N-oxide oxygen, the imine nitrogen, and a pyridine or quinoline nitrogen. The complexes have been characterised by magnetic susceptibility measurements to liquid nitrogen temperature, and also by electronic, infrared, X-ray powder diffraction, and Mössbauer spectra. No magnetic interaction was detected with the copper(II) complexes. All the complexes of metal nitrates appear to be monomers.The complexes of poph with the halides and thiocyanates of nickel(II) and cobalt(II) appear to be six-coordinate and N-oxide-bridged; they exhibit varying degress of antiferromagnetic interaction and the magnetic data for the nickel(II) complexes have been fitted to various models. In contrast, the bulky ligand poqh produces halide-bridged six-coordinate nickel(II) complexes and monomeric five-coordinate cobalt(II) complexes.This behaviour by poqh resembles that of the related NNN ligands paphy and paqhy, which are the Schiff bases of 2-pyridinecarboxaldehyde with 2-pyridinylhydrazine and 2-quinolinylhydrazine, respectively.     

Dioxouranium(VI) thiocyanate complexes of schiff bases of p-nitro,chloro, bromo,hydroxy and methoxy aniline and salicylaldehyde

A series of dioxouranium(VI) complexes was synthesised with some Schiff base ligands containing substituent groups at para positions to CHN groups. These molecules were obtained by the condensation of para-nitro, chloro, bromo, hydroxy, methyl and methoxy aniline with salicylaldehyde. The bidentate ligands formed complexes of the type UO₂(NCS)₂ (X-N-Sal)_n·mH₂O, where n = 2, m = 3, x = NO₂, Cl, Br and OH; n = 3, m = 2, x = CH₃ and OCH₃.Conductivity measurements indicate that all the complexes are non-electrolytes in nitromethane solution, whereas in DMF they correspond to 1:1 electrolytes.IR spectral data suggest that the molecules and not the anions of the Schiff base are coordinated to the central uranium atom. IR and Raman spectra suggest that the complexes UO₂(NCS)₂(X-N-Sal)₂· 3H₂O (X = NO₂, Cl, Br) have C_2h molecular symmetry, whereas UO₂(NCS)₂(X-N-Sal)₃·2H₂O (X = OCH₃, CH₃) have C_2v symmetry.The frequencies of UO_2(asym) (IR) and UO_2(sym) (R) in the complexes seem to vary with the various substituents of the Schiff base ligand, in the order:NO₂ > Cl > Br > OH > CH₃ > OCH₃     

Synthesis of homodinuclear macrocyclic complexes of lanthanides and phenolic schiff bases

Successful syntheses of the first examples of homodinuclear macrocyclic lanthanide complexes are reported. The complexes were obtained as compounds of the 2:2 Schiff base formed by condensing 2,6-diformyl-p-cresol and triethylenetetramine (L₇) by a template procedure using lanthanide nitrates and perchlorates. When reactant methanolic solutions were concentrated the complexes were deposited as yellow or orange microcrystalline precipitates, Ln₂L₇(NO₃)₄sigma; nH₂O or Ln₂L₇(NO₃)_{4tau; x}(OH)_x, x = 1 or 2, whereas solutions diluted three times deposited complexes as flaky off-white crystalline precipitates of light lanthanides. The orange Ln₂L₇(NO₃)₂(OH)₂ complexes can be converted in quantitative yield to the off-white flaky form of Ln₂L₇(NO₃)₄sigma; nH₂O by refluxing them in methanolic solution containing triethylenetetramine and a three-fold excess of Ln(NO₃)₃. The complexes were characterized by elemental analysis, fast atom bombardment mass spectrometry, UV-Vis and infrared spectroscopy and thermogravimetry. Interesting and mostly new polyatomic oxo clusters, e.g. Ln₂O₃⁺, Ln₃O₄⁺, Ln₄O₆⁺, Ln₅O₇⁺, were dominant in the mass spectra but are treated in detail elsewhere.     

Lanthanide complexes of some macrocyclic schiff bases derived from pyridine-2,6-dicarboxaldehyde α,ω-primary diamines

The synthesis of macrocyclic lanthanide complexes via the reaction of pyridine-2,6-dicarboxaldehyde with 1,2-diaminoethane, 1,2-diaminopropane and 1,3-diaminopropane in the presence of lanthanide nitrates as templating agents is discussed together with the use of the lanthanum derivatives in transmetallation reactions with copper(II).     

Synthesis, structure and biological activity of cobalt(II) and copper(II) complexes of valine-derived schiff bases

We have synthesized two cobalt(II) 2 and copper(II) 3 complexes of valine-derived Schiff bases. The obtained complexes were characterized by elemental analysis, FT-IR and X-ray diffraction. Biological studies of complexes 2 and 3 had been carried out in vitro for antimicrobial activity against Gram-positive, Gram-negative bacteria and human pathogenic fungi. Compound 3 was proven to be a broad spectrum agent, showed a significant inhibition of the growth of Gram-positive bacteria (Staphylococcus aureus, methicillin-resistant S. aureus, Bacillus subtilis, Micrococcus luteus), and pathogenic fungi (Candida spp., Cryptococcus neoformans, Rhodothece glutinis, Saccharomyces cerevisia, Aspergillus spp., Rhizopus nigricans) tested and a moderate activity against Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Proteus vulgaris and Enterobacter aerogenes) tested. The in vitro cytotoxicity of compound 3 was evaluated using hemolytic assay, in which the compound 3 was found to be non-toxic to human erythrocytes even at a concentration of 500mug/mL.     

Synthesis characterization and cytotoxicity studies of platinum(II) complexes with reduced amino pyridine schiff base and its derivatives as ligands

A series of reduced amino pyridine Schiff base platinum(II) complexes were prepared as potential anticancer drugs, and characterized by NMR, IR spectroscopy, elemental analysis, and molar conductivity. UV and CD results showed the binding mode between these compounds and salmon sperm DNA may be intercalation. The cytotoxicity of these complexes was validated against A549, Hela, and MCF-7 cell lines by MTT assay. Some complexes exhibited better cytotoxic activity than cisplatin against Hela and MCF-7 cell lines.     

Acyclic and macrocyclic schiff base complexes of lanthanides and actinides

The work reviewed here is the result of a collaborative project designed to explore the interaction of lanthanides and actinides with acyclic and macrocyclic Schiff base ligands. The ligands are penta- and hexa-dentate in character and have present arrays of donors drawn from oxygen, nitrogen and sulphur atoms. The acyclic ligands are capable of allowing binuclear incorporation to occur; this feature was included in the study as is the area of selective metal extraction. A single ligand capable of removing two cations simultaneously would have cost benefit advantage over a ligand capable only of removing a single cation.     

Metal complexes of a new class of polydentate Mannich bases: Synthesis and spectroscopic characterisation

A new class of polydentate Mannich bases featuring an N₂S₂ donor system, bis((2-mercapto-N-phenylacetamido)methyl)phosphinic acid H₃L¹ and bis((2-mercapto-N-propylacetamido)methyl)phosphinic acid H₃L², has been synthesised from condensation of phosphinic acid and paraformaldehyde with 2-mercaptophenylacetamide W1 and 2-mercaptopropylacetamide W2, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(Lⁿ)Cl₂], K₃[M′^II(Lⁿ)Cl₂] and K[M(Lⁿ)] (M′ = Mn(II) or Fe(II); M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) or Hg(II); n = 1, 2) are reported. The structures of new ligands, mode of bonding and overall geometry of the complexes were determined through IR, UV–Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II) and Fe(II) complexes, square planar for Ni(II) and Cu(II) complexes and tetrahedral for the Co(II), Zn(II), Cd(II) and Hg(II) complexes. Complex formation studies via molar ratio in DMF solution were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1).     

Ni(II) complexes with Schiff bases derived from amino sugars

It was found by 1H and 13C NMR spectroscopy that the Schiff base, 2-deoxy-2-(2-hydroxybenzaldimino)-D-glucopyranose exhibits enol-imine-keto-amine and anomeric equilibria in methanolic, and in dimethyl sulfoxide solutions. The reaction of the Schiff base with nickel acetate gave the bidentate, mononuclear Ni(II) complex that was characterized by spectroscopic methods and by cyclic voltammetry. The coordination of the Schiff base to the metal is through the enol-imine tautomeric form, and the anomeric equilibrium remains in dimethyl sulfoxide solutions. This complex was also obtained by reaction of D-glucosamine with Ni(II) salicylaldehydate. The same reaction was employed for the synthesis of bis-N-[2-deoxy-D-galactopyranosyl-2-(2-hydroxybenzaldiminate)]Ni(II). The small paramagnetic shifts of the 1H NMR resonances of the complexes suggest that paramagnetic species are present in low proportions.     

Influence of some reactional parameters on the substitution degree of biopolymeric Schiff bases prepared from chitosan and salicylaldehyde

Some reactional parameters as mol ratio (salicylaldehyde:free amino groups), reaction time and temperature were investigated in order to improve the substitution degree (DS) in the preparation of biopolymeric Schiff bases from chitosan. In this case, the reaction of chitosan and salicylaldehyde was used as a probe system in order to produce the Schiff base. The use of 50% (mol/mol) salicylaldehyde excess, reaction time of 18 h and temperature of 55 °C permitted to obtain a DS of 60% without evidences of hydrolysis of the biopolymeric matrix or changes in its acetylation degree.     

The synthesis of polymeric schiff base metal complexes with 4 N ligands

The bifunctional aldehyde 3,3′diamino-4,4′diformyldiphenyl-sulfone was prepared and reacted with diamines to Schiff bases. Polymeric metal complexes were obtained with Mn²⁺, Ni²⁺, Pd²⁺, Pt²⁺, Ir³⁺ and Au³⁺. The thermal stabilities of these complexes are reported.     

Structure and anomeric configuration of the 3,6-anhydro-osazone derivatives obtained from d-altro-2-heptulose phenylosazone

Dehydration of d-altro-2-heptulose phenylosazone with methanolic sulfuric acid afforded two 3,6-anhydro-osazone derivatives (2 and 3). Compound 3 was obtained as the preponderant isomer, with inversion at C-1 (C-3 of the starting osazone), and 2 was obtained without inversion. Refluxing of 3 with copper sulfate afforded the C-nucleoside analog, namely, 2-phenyl-4-β-d-ribofuranosyl-1,2,3-osotriazole (4). Acetylation of 4 afforded the tri-O-acetyl derivative 5. The anomeric configuration was determined by c.d. and n.m.r. spectroscopy. The mass spectra of compounds 2–5 are discussed.