Metal-ligand Stoichiometry Research Articles

Studies on salicylaldehyde-2-aminobenzophenone-2-thenoylhydrazone complexes with 3d metal ions

Salicylaldehyde-2-aminobenzophenone-2-thenoylhydrazone (Hsabth) complexes of OV(IV), Mn(II), Ni(II), Ni(II), Cu(II) and Zn(II) having 1∶2 metal-ligand stoichiometry have been prepared and characterized by elemental analyses, molar conductance, magnetic susceptibility, electronic, ESR, infrared, NMR (1H and13C) and X-ray powder diffraction studies. Square pyramidal geometry around oxovandium(IV) and octahedral geometry around the rest of the metal ions have been proposed on the basis of magnetic and spectral studies.

Characterization and thermal behaviour of Cu(II) chelates of Schiff bases derived from aminopyridines

Complexes of copper(II) with Schiff bases derived from 3-amino- and 2-amino-pyridine and its derivatives with salicylaldehyde and o-hydroxynaphthaldehyde have been synthesized. The compounds have been characterized by elemental analysis, IR and electronic absorption spectra and differential thermal analysis. The data show the formation of two different types of compound with 1:1 and 1:2 metal-ligand stoichiometries and different thermal properties.

Thermal and electrical studies of some polychelates

Polychelates of Mn(II), Fe(II), Co(II), Ni(II), and Cu(II) with 4,4′-dihydroxy-3,3′-diacetylbiphenyl-dithioxamide (DDBDO) have been prepared. Their structures were determined by visible reflectance spectroscopy and magnetic measurements in conjunction with thermogravimetric and IR measurements. Elemental analysis indicates a 1∶1 metal-ligand stoichiometry and the association of water molecules with the central metal. The decomposition temperature of the chelates is in the order Ni(II)>Fe(II)>Co(II)>Mn(II)>Cu(II). Thermal activation energies (E a ), calculated with the help of Freeman-Carroll and Sharp-Wentworth methods, are in agreement with each other. The polychelates were found to be semiconductive, and the activation energy obtained from semiconducting behavior follows the order Co(II)>Ni(II)>Fe(II)>Cu(II)>Mn(II). The probable structure, such as six coordinated octahedral for Mn(II) and Fe(II) polychelates and four coordinated square planar for Co(II), Ni(II), and Cu(II) polychelates, have been suggested.

Study on Polymers and Polychelates Derived from β-Resorcylaldehydeoxime and Furfural

Abstract A new polymeric ligand has been synthesized from β-Resorcylaldehydeoxime (β-RAO) and furfural in presence of alkali as catalyst. The molecular weight of the polymeric ligand was estimated by non-aqueous conductometric titration and by vapour pressure osmometry (VPO). The polychelates were prepared by condensing β-RAO-Fur and metal acetates of copper(II), nickel(II) and cobalt(II). The polymers were characterized by elemental analysis, visible and infrared spectroscopy, thermal analysis and magnetic measurements. All polychelates are insoluble and did not melt up to 360°C. The elemental analysis data indicated that all polychelates have 1:2 metal ligand stoichiometry.

Synthesis and physicochemical studies of polymeric coordination complexes of some lanthanides with 1,4-dihydroxyanthraquinone

Coordination polymers of lanthanum(III), praseodymium(III), neodymium(III), samarium(III), dysprosium(III) and holmium(III) with 1,4-dihydroxyanthraquinone have been synthesized and characterised. Their magnetic moments, infrared spectra and electronic spectra have been studied to establish their structure. All the polychelates are amorphous, dark coloured powders, insoluble in common organic solvents and sparingly soluble in dimethylformamide. Nephelauxetic ratio (β), covalency factor ( b 1/2), etc. have been evaluated wherever possible. Thermogravimetric studies (TGA) indicate a higher decomposition temperature of polychelates than the parent ligand. A.c.-conductivity, dielectric constant (ϵ′), dielectric loss (ϵ″), all at various frequencies, as well as d.c.-conductivity of the prepared polychelates, are reported. The analytical data are suggestive of a 2:3 metal-ligand stoichiometry in the polychelates.

Nickel(II) and cobalt(II) complexes of the hydrazide of 1-naphthylacetic acid

The hydrazide of 1-naphthylacetic acid forms both bis- and tris-(ligand) high-spin nickel(II) and cobalt(II) complexes possessing an octahedral configuration. The compositions of the complexes are influenced not only by the metal-ligand stoichiometry but also by the nature of the inorganic anion. A physico-chemical investigation showed that the ligand is neutral and bidentate, coordinated through amido-nitrogen and carbonyl oxygen. The compounds were characterized by elemental analysis, magnetic measurements, i.r. and diffuse-reflection spectra and molar conductivity.

Synthesis and Characterization of 2-Thenoylhydrazine Complexes with some Bivalent Metal Ions

Abstract The 2-thenoylhydrazine, TH(L) (Fig. 1) complexes having 1:1, 1:2 or 1:3 metal-ligand stoichiometry have been prepared and characterized by elemental analyses, molar conductance, molecular weight, magnetic susceptibility, electronic, infrared, NMR, Mossbauer and X-ray powder diffraction studies. Tetrahedral stereochemistry around Zn(II), Cd(II) and Hg(II), square pyramidal geometry around VO(IV) and octahedral coordination around Mn(II), Fe(II), Co(II), Ni(II) and Cu(II) ions have been proposed in these complexes on the basis of magnetic and spectral studies.

Multinuclear NMR studies on new platinum imine complexes

Platinum(II)-olefin complexes with Schiff bases derived from 2-acetylthiophene, and primary amines were synthesized and characterized on the basis of elemental analysis, I.R., 1H, 13C, and 195Pt-NMR studies. The Schiff bases behave as unidentate bases with N as the only donor ligand and form four coordinate complexes with 1:1 metal-ligand stoichiometry at ambient temperature of composition trans-[PtCl 2(η 2-C 2H 4)(Imine)]. Long-range coupling constants were observed between different protons of the imine and platinum-195. Addition of excess amine leads to displacement of the imine and rapidly gives the zwitterionic 2-ammonioethanide-platinum(II) complex. The platinum complex of the imine type provide the first example of stable platinum(II)-olefin-monodentate σ-imine bonded complexes. In addition, 1H, 13C and 195Pt-NMR spectra show that only a single rotamer exists. Other more imine complexes were synthesized.

Magnetic, Spectral, Thermal, and Electrical Properties of Coordination Polymers Derived from Terpolymers

Abstract Coordination polymers of Cu(II), Ni(II), Co(II), Zn(II), Cr(III), Fe(III), oxovanadium (IV), and dioxouranium(VI) with salicylic acid (S)-thiourea (T)-trioxane (T) (STT) polymer were prepared. The analytical data agree with 1:1 metal-ligand stoichiometry. Elemental analyses, magnetic, spectral, and thermal properties, and electrical conductivities of STT and its chelates have been studied and probable structures are assigned to the coordination polymers. All the chelates are amorphous powders, insoluble in common organic solvents, and showing slight solubility in DMF.

Studies on Polyazomethine Chelate Polymers

Abstract Poly-Schiff-base ligand (SBSAL-DDM) is synthesized by condensing bis-salicylaldehyde 5,5′-sulfone with 4,4′-diaminodiphenyl methane. The polychelates of Cu(II), Ni(II), Co(II), and Mn(II) with poly-Schiff base have been isolated and analyzed. The analytical data agree with 1:1 metal-ligand stoichiometry. The polychelates are studied in terms of electrical, thermal, spectral, and magnetic properties. A probable structure has been proposed for the above polymers.

Study on Semi-Glycinecresol Red complexes with bivalent metal ions

Semi-Glycinecresol Red (SGCR or H 3SGCR) was purified by means of chromatography on cellulose and by cation-exchange. A potentiometric, spectrophotometric and ESR study on the complex formation equilibria of several bivalent metal ions with SGCR was performed. The acid—base and metal—ligand stoichiometries were determined, and the formation constants, λ max and absorptivities of the visible-region absorption spectra of the corresponding proton and metal complexes were determined. The copper complexes were examined by ESR spectroscopy. Each metal ion was found to form the 1:1 and 1:2 (metal:ligand) complex species, MSGCR − and M(SGCR) 4− 2, in alkaline solution. However, only Cu(II) was found to form the protonated complexes, CuHSGCR and Cu(HSGCR) 2− 2, in weakly acidic media. SGCR is suitable as an indicator for Cu(II) in a weakly acidic solution and for Cu(II), Zn(II) and Pb(II) in alkaline solution

N-Acetylacetone-anthranilic acid as a gravimetric reagent for copper(II)

N-Acetylacetone-anthranilic acid has been employed as a reagent for the gravimetric determination of copper(II). The solid copper(II) chelate formed possesses 1:1 metal-ligand stoichiometry and is found to exist as an unsolvated dimer. The complex has a magnetic moment of 1.88 B.M. at 298 K. A non-planar dimeric structure is suggested to explain the observed facts.