Oxovanadium(IV) complexes with (ONNO)-type tetradentate Schiff base ligands: salen, acacen, aceten, acetph (H2salen = N,N'-ethylenebis(salicylideneimine), H2aceten = N,N'-ethylenebis(2-hydroxyacetophenoneimine), H2acacen = N,N'-ethylenebis(acetylacetonimine), H 2 acetph = N ,N ' -phenylene-1,2-b is (2-hydroxyacetophenoneimine)), were the first time investi- gated in ethylene polymerization and ethylene/1-octene copo- lymerization processes. In general, all these complexes are moderately active precatalyst for ethylene polymerization up- on activation with EtAlCl2 and they give high molecular weight linear polyethylenes. Their activity in copolymeriza- tion was found relatively low. However, they yielded copoly- mers with high 1-octene incorporation even at low comono- mer concentrations in the feed. The catalytic performance in homo- and copolymerization was influenced by both the ligand structure and polymerization parameters (Al/ V molar ratio, polymerization temperature, comonomer feed concentration). In addition, the (VO(acacen)) was supported onto magnesium supports, and in the presence of various cocatalyst and at different reaction conditions it was screened as the catalyst of choice for ethylene homo- and copolymerization.

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Oxovanadium(IV) complexes with (ONNO)-chelating ligands as catalysts for ethylene homo- and copolymerization

A new series of transition metal complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) have been synthesized from the Schiff base (L) derived from 4-aminoantipyrine, 3-hydroxy-4-nitrobenzaldehyde and o-phenylenediamine. Structural features were obtained from their elemental analyses, magnetic susceptibility, molar conductance, mass, IR, UV-Vis, 1H NMR and ESR spectral studies. The data show that these complexes have composition of ML type. The UV-Vis, magnetic susceptibility and ESR spectral data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The redox behaviour of copper and vanadyl complexes was studied by cyclic voltammetry. Antimicrobial screening tests gave good results in the presence of metal ion in the ligand system. The nuclease activity of the above metal complexes shows that Cu, Ni and Co complexes cleave DNA through redox chemistry whereas other complexes are not effective.

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Synthesis, spectral characterization of Schiff base transition metal complexes: DNA cleavage and antimicrobial activity studies

N,N'-ethylenebis(salicylideneiminato) transition metal ion chelates

Neutral tetradentate N2O2 type complexes of Cu(II), Ni(II), Mn(II), Zn(II) and VO(II) have been synthesised using a Schiff base formed by the condensation of o-phenylenediamine with acetoacetanilide in alcohol medium. All the complexes were characterised on the basis of their microanalytical data, molar conductance, magnetic susceptibility, IR, UV-Vis1H NMR and ESR spectra. IR and UV-Vis spectral data suggest that all the complexes are square-planar except the Mn(II) and VO(II) chelates, which are of octahedral and square pyramidal geometry respectively. The monomeric and neutral nature of the complexes was confirmed by their magnetic susceptibility data and low conductance values. The ESR spectra of copper and vanadyl complexes in DMSO solution at 300 K and 77 K were recorded and their salient features are reported.

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Synthesis and characterisation of Cu(II), Ni(II), Mn(II), Zn(II) and VO(II) Schiff base complexes derived from o -phenylenediamine and acetoacetanilide

Novel terdentate neutral complexes of CuII, NiII, CoII, MnII, ZnII, CdII, HgII, VOII, ZrOII and UO2
II have been prepared using a Schiff base derived from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one (4-aminoantipyrine) and acetoacetanilide The structural features of the chelates have been confirmed by microanalytical data, ir, uv–vis, 1H-nmr, esr and mass spectral techniques Electronic absorption and ir spectra of the complexes indicate an octahedral geometry around the central metal ion, except for the VOII and ZrOII complexes which show square pyramidal geometry The monomeric and neutral nature of the complexes are confirmed from their magnetic susceptibility and low conductance values The cyclic voltammogram of the copper complex in MeCN at 300 K shows a quasi-reversible peak for the couple CuII/CuIII at Epc = 047 and Epa = 061 V versus Ag/AgCl and two irreversible peaks for CuII → CuI and CuI → Cu0 reduction at Epc = −063 and − 089 V respectively The esr spectra of copper and vanadyl complexes in DMSO solution at 300 K and 77 K were recorded and their salient features are reported The molecular orbital coefficients (α2, β2) were calculated for complexes The antimicrobial activity of the ligand and its complexes have been extensively studied on microorganisms such as Staphylococcus aureus, Klebsiela pneumoniae, Bacillus subtillis, Escherichia coli, Citrobacter ferundii and Salmonella typhi Most of the complexes have higher activities than that of the free ligand

Synthesis, spectral, redox and antimicrobial activities of Schiff base complexes derived from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one and acetoacetanilide

Stereochemistry and electronic structure of oxovanadium(IV) chelates with tetradentate Schiff base ligands derived from 1,3-diamines

Circular dichroism of tetradentate Schiff base chelates of oxovanadium(IV)

The results of i.r. electronic, c.d., and e.s.r. solution spectra indicate that [NN′-bis(salicylidene)-S-(+)-butane-1,3-diamino]oxovanadium(IV), [VO(sal)2-(+) tnMe], is five-co-ordinate in chloroform, but becomes six-co-ordinate in solvents such as pyridine, dimethylformamide, and methanol.

Richard L. Farmer

Papers

Stereochemistry and electronic structure of oxovanadium(IV) chelates with tetradentate Schiff base ligands derived from 1,3-diamines

Circular dichroism of tetradentate Schiff base chelates of oxovanadium(IV)

Solution properties of [NN′-bis(salicylidene)-S-(+)-butane-1,3-diamino]oxovanadium(IV)