Synthesis and magnetic studies of phthalato-bridged oxovanadium(Ⅳ) binuclear complexes

Six new μ-phthalato binuclear oxovanadium(IV) complexes,namely [(VO)2(PHTH)-(L)2]SO4 (L denotes 2,2'-bipyridine (bpy);1,10-phenanthroline (phen);4,4'-dimethyl-2,2'-bipyridine (Me2bpy);5-nitro-1,10-phenanthroline (NO2-phen);5-chloro-1,10-phenanthroline (Cl-phen) and 5-methyl-l,10-phenanthroline (CH3-phen),where PHTH is the phthalate dianion),have been synthesized and characterized by elemental analyses,IR,electronic spectra,magnetic moments at room temperature and molar conductivity measurements.The temperature dependence of the magnetic susceptibility of complexes [(VO)2(PHTH)(Phen)2]SO4 (1) and [(VO)2(PHTH)(CH3-phen)2]SO4 (2) was measured in 4-300 K range and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator,H--2JS1S2,giving the exchange integrals J=-12.8 cm-1 for 1 and J=-7.9 cm-1 for 2.This indicates an antiferromagnetic spin-exchange interaction between the metal ions within each molecule.     

Synthesis, characterization and magnetic properties of novel μ-isophthalato oxovanadium(IV) binuclear complexes

Four novel oxovanadium(IV) binuclear complexes have been synthesized, namely [(VO)₂(IPHTA) (L)₂SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 5-nitro-1,10-phenanthroline (NO₂-phen)), where IPHTA is the isophthalate dianon. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have IPHTA-bridged structures and consist of two vanadium(IV) atoms in a square-pyramidal environment. The complexes [(VO)₂(IPHTA)(Me₂bpy)₂]SO₄ (1) and [(VO)₂(IPHTA)(bpy)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility (4–300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, . The exchange integral, J, was found to be −26.8 cm⁻¹ for (1) and −31.0 cm⁻¹ for (2). These results are commensurate with antifferomagnetic interactions between two oxovanadium(IV) ions within each molecule. The influence of different terminal ligands on magnetic interactions between the metals of this kind of complexes is also discussed.     

Studies on the synthesis and magnetic property of binuclear oxovanadium(IV) complexes bridged by chloranilato group

Six novel oxovanadium(IV) binuclear complexes have been synthesized and characterized, namely, [(VO)₂(CA)L₂]SO₄ [L denotes 5-methyl-1,10-phenanthroline (Me-phen); 2,9-dimethyl-1,10-phenanthroline (Me₂-phen); 5-chloro-1,10-phenanthroline (Cl-phen); diaminoethane (en); 1,3-diaminopropane (pn) and 1,2-diaminopropane (ap) respectively.], where CA represents the dianion of chloranilic acid. Based on elemental analyses, molar conductivity and room temperature magnetic moment measurements, IR and electronic spectral studies, it is proposed that there complexes have CA-bridged structures and consist of two vanadium(IV) ions in a square-pyramidal environment. The complexes [(VO)₂(CA)(Me-phen)₂]SO₄ (1) and [(VO)₂(CA)(Me₂-phen)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility measurements (4～300 K) and the observed data were fitted to the modified Bleaney-Bowers equation by the least-squares method, giving the exchange integral J=-15.8 cm^?1 for 1 and J=-10.6 cm^?l for 2. This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two VO²⁺ ions within each molecule.     

Synthesis,characterization and biological studies of oxovanadium(IV) complexes with triazole‐derived Schiff bases

A series of triazole‐derived Schiff bases (L¹–L⁵) and their oxovanadium(IV) complexes have been synthesized. The chemical structures of Schiff bases were characterized by their analytical (CHN analysis) and spectral (IR, ¹H and ¹³C NMR and mass spectrometry) data, and oxovanadium(IV) complexes were elucidated by their physical (magnetic susceptibility and conductivity), analytical (CHN analysis), conductance measurements and electronic spectral data. The molar conductivity data indicate the oxovanadium(IV) complexes to be non‐electrolyte. The Schiff bases act as bidentate and coordinate with the oxovanadium(IV)‐forming stoichiometry of a complex as [M (L‐H)₂] where M = VO and L = L¹–L⁵ in a square‐pyramidal geometry. The agar well diffusion method was used for in vitro antibacterial screening against E. coli, S. flexenari, P. aeruginosa, S. typhi, S. aureus and B. subtilis and for antifungal activity against T. longifucus, C. albican, A. flavus, M. canis, F. solani and C. glaberata. The biological activity data show the oxovanadium(IV) complexes to be more antibacterial and antifungal than the parent Schiff bases against one or more bacterial and fungal strains. Copyright © 2009 John Wiley & Sons, Ltd.     

Synthesis characterization and magnetic properties of μ-iodanilato dinuclear oxovanadium(IV) complexes

Five oxovanadium(IV) dinuclear complexes described by the overall formula [(VO)₂(IA)L₂SO₄, where IA repents the dianion of iodanilic acid and L denotes 2, 2′-bipyridine (bpy); 4,4′-dimethy12,2′-bipyridine (Meo-bpy); 1,10-phenanthroline (phen); 4,7-diphenyl-l, 10-phenanthroline (Ph₂-phen) and 5-nitro-1, 10-phenanthroline (NO₂-phen), have been synthesized and characterized by elemental analyses, molar conductivity and roomtemperature magnetic moment measurements, IR and electronic spectral studies. It is proposed that these complexes have IA-bridged structures and consist of two oxovanadium(IV) ions each in a square pyramidal environment. The complexes (VO)₂(IA) (bpy)₂]SO₄, (1) and[(VO)₂( IA) (phen)₂ ]SO₄ (2) were further characterized by variable temperature (4.2–300 K) magnetic susceptibility measurements and the observed data were fitted to the modified Bleaney-Bowers equation by the least-squares method, giving the exchange integral J = - 2.15 m^?1 for 1 and J = - 9.88 cm^?1 for 2. This result indicates that there is a weak antiferromagnetic spin-exchange interaction between the two VO²⁺ ions within each molecule.     

Synthesis and magnetic interaction of μ-2-chloroterephthalato binuclear iron (Ⅱ) complexes

Four μ-2-chloroterephthalato binuclear iron(Ⅱ) complexes, namely [Fe2 (CTPHA) L4]-(ClO4)2, where L stands for 4,4'-dimethyl-2,2'-bipyridine (Me2-bpy); 2,9-dimethyl-l, 10-phenanthro-line (Me2-phen); 5-chloro-l, 10-phenanthroline (Cl-phen); 4, 7-diphenyl-l, 10-phenanthroline (Ph2-phen), respectively, and CTPHA represents 2-chlorolerephthalate dianion, have been synthesized and characterized. Based on the elemental analyses, molar conductance measurements and spectroscopic studies, extended CTPHA-bridged structures consisting of two iron(Ⅱ) ions, each in a distorted octahedral environment, are proposed for these complexes. [Fe2 CTPHA)-(Me2-bpy)4] (ClO2 (1) and [Fe2(CT-PHA)·(Me2-phen)4](ClO4)2 (2) complexes were characterized by variable temperature magnetic susceptibility (4-300 K) measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, H = - 2JS1 · S2 , giving the exchange integrals J = - 1.28 cm-1 for 1 and J = - 1.85 cm-1 for 2. These r     

Synthesis,electrochemical and antimicrobial studies of mono and binuclear iron(III) and oxovanadium(IV) complexes of [ONO] donor tridentate Schiff-base ligands

Tridentate Schiff bases (H₂L¹ or H₂L²) were derived from condensation of acetylacetone and 2-aminophenol or 2-aminobenzoic acid. Binuclear square pyramidal complexes of the type [M₂(L¹)₂]?·?nH₂O (M?=?Fe–Cl, n?=?0; M?=?VO, n?=?1) were accessed from interaction of H₂L¹ with anhydrous FeCl₃ and VOSO₄?·?5H₂O, respectively. A similar reaction with H₂L², however, produced mononuclear complexes [ML²(H₂O) _x ]?·?nH₂O (M=Fe–Cl, x?=?0, n?=?0; M=VO, x?=?1, n?=?1). The compounds were characterized using elemental analysis, FT-IR, UV-Vis, and NMR (for ligand only), and mass spectroscopies and solution electrical conductivity studies. Magnetic susceptibility measurements suggest antiferromagnetic exchange in binuclear Fe(III) and VO(IV) complexes. Thermo gravimetric analysis (TGA) provided unambiguous evidence for the presence of coordinated as well as lattice water in [VOL²(H₂O)]?·?H₂O. Cyclic voltammetric studies showed well-defined redox processes corresponding to Fe(III)/Fe(II) and VO(V)/VO(IV). In vitro antimicrobial activities of the compounds were investigated against Klebsiella pneumoniae, Staphylococcus aureus, Pseudomonas aeroginosa, Escherichia coli, Bacillus subtilis, and Proteus vulgaris. H₂L¹ and its binuclear complexes exhibited pronounced activity against all the microorganisms tested.     

Synthesis,thermal and electrical studies on solvated oxovanadium(IV) complexes with schiff bases derived from aromatic diamines and 2-hydroxy-1-naphthaldehyde

Summary Solvated oxovanadium(IV) complexes of Schiff bases derived from aromatic diamines and 2-hydroxy-1-naphthaldehyde have been prepared from ethanolic medium. The elemental analyses reveal that the complexes have the ratio 1:1, 2:2 and 1:2 (ligand:metal) composition which are nonelectrolyte inDMF. The coordination number six (octahedral geometry) is proposed for the complexes prepared. This is based on the results of IR, electronic and EPR spectra. TGA as well as DTA studies and the electrical properties and (I–V) characteristics for the metal complexes were investigated.

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Synthese und thermische bzw. elektrochemische Untersuchungen an solvatisierten Oxovanadium(IV)-Komplexen mit Schiff-Basen aus aromatischen Diaminen und 2-Hydroxy-1-naphthaldehyd

Zusammenfassung Die im Titel genannten Komplexe wurden in ethanolischem Medium hergestellt. Sie sind inDMF Nichtelektrolyte und haben laut Elementaranalyse die Zusammensetzung Ligand:Metall=1:1, 2:2 und 1:2. Basierend auf IR-, UV- und EPR-Spektren wird die Koordinationszahl 6 (oktahedrale Geometrie) vorgeschlagen. Es wurden TGA- und DTA-Studien durchgeführt und das elektrochemische Verhalten der Metallkomplexe untersucht.

     

Novel cytotoxic oxovanadium(IV) complexes: Influence of pyrazole‐incorporated heterocyclic scaffolds on their biological response

Homoleptic VO^IV complexes with bidentate heterocycles, namely bipyrazole/pyrimidin‐2‐amine/triazolopyrimidine derivatives, are novel square pyramidal oxovanadium(IV) complexes. Their identities have been established using physicochemical techniques, namely elemental and spectral (ESI‐MS, IR, UV–visible) analyses. The in vitro antibacterial activities against Gram‐negative and Gram‐positive microorganisms have been studied for all compounds, exhibiting good inhibition as compared to the ligands. In addition, all compounds exhibit significant cytotoxicity towards brine shrimp with LD₅₀ values obtained in the range 8–24 μg ml⁻¹. Cellular level cytotoxicity has been investigated using bioassay of Schizosaccharomyces pombe , the complexes showing inevitable viability as concentration increases. Notably, UV absorption spectral titrations of the synthesized complexes with DNA reveal that the complexes bind to calf thymus DNA (CT‐DNA) through intercalation mode (K _b = 10⁴–10⁵ M⁻¹). Molecular docking reveals that the compounds are stacked between the base pairs of DNA. The results suggest that the complexes show promising binding affinity compared to the ligands towards CT‐DNA.     

Synthesis and magnetic properties of copper (II)-lanthanoid (III) binuclear complexes with N,N′-bis(3-aminopropyl) oxamido ligand

Six novel μ-oxamido binuclear complexes, namely Cu(axpn)Ln(L)₂(ClO₄)₃ (Ln: Eu, Gd, Tb, Nd, Ho, Er), where oxpn is N,N'-bis(3-aminopropyl) oxamido, L denotes 5-nitro,10-phenanthroline (abbreviated as NO₂-phen), have been synthesized and characterised. The magnetic susceptibility of complexes Cu(oxpn)Gd(NO₂-phen)2(ClO₄)₃.2H₂O was measured over the 4–300 K and the observed data were successfully simulated by equation based on spin Hamiltonian operator (H = -2J₁ · S₂), giving the exchange integral J(Cu-Gd)=-1.62 cm^?1. This indicates a weak antiferromagnetic interaction between the Cu(II) and Gd(III) ions.     

Synthesis, characterization and magnetism of μ-chloranilato bi-nuclear chromium (III) complexes

Five new chloranilato-bridged binuclear chromium (III) complexes have been synthesized and identified as [Cr2(CA)L4]-(ClO4)4[L denotes 5-methyl-1,10-phenanthroline (Me-phen); 2,9-dimethyl-1, 10-phenanthroline ( Me2-phen); 5-chloro-1,10-phenanthroline(Cl-phen); diaminoethane (en) or 1,3-diaminopropane (pn)], where CA represents the dianion of chloranilic acid. Based on elemental analyses, molar conductivity and magnetic moment of room-temperature measurements, and IR and electronic spectral studies, it is proposed that these complexes have CA-bridged structures and consist of two chromium (III) ions, each in an octahedral environment. The complexes [Cr2(CA)(Me-phen)4](ClO4)4(1) and [Cr2(CA)(Me2-phen)4](ClO4)4(2) were further characterized by variable temperature (4.2-300 K) magnetic susceptibility measurements and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, , giving the exchange parameter J = -7.8 cm-1 for (1) and J= -6.5 cm*1 for (2). This result     

Synthesis, characterization and magnetism of binuclear cobalt (II) complexes bridged by tetracarboxylato groups

Three new binudear cobalt (II) complexes with extended te-tracarboxylato- bridge have been synthesized and characterized, namely [Co2 (PMTA) (bpy)4] (1), [Co2(PMTA)-(phen)4] (2) and [Co2(PMTA) (NO2phen)4] (3), where PMTA represents the tetraanion of pyroniellitic acid, and bpy, phen, NO2-phen denote 2,2'-bipyridine, 1,10-phenan-throline; 5-nirto-1, 10-plienanthroline, respectively. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have PMTA-bridged structures and consist of two cobalt (II) ions, each in a distorted octahedral environment. These complexes were further characterized by variable temperature magnetic susceptibility measurements (4-300 K) and the observed data were successfully simulated by the equation based on the spin Hamiltonian operator, giving the exchange integral J = - 1.02 cm-1 for 1, J = -1.21 cm-1 for 2 and J = - 1.18 cm-1 for 3, respectively. These results revealed the operation of antiferromagneti     

Studies on some oxovanadium(IV) complexes of acyl pyrazolone analogues

A series of novel bidentate pyrazolone based Schiff base ligands were synthesized by interaction of 4-benzoyl-3-methyl-1-(4′-methylphenyl)-2-pyrazolin-5-one with various aromatic amines like aniline, o-,m-,p-chloroaniline and o-,m-,p-toluidine in a ethanolic medium. All of these ligands have been characterized on the basis of elemental analysis, IR and ¹H NMR data. The molecular geometries of five of these ligands have been determined by single crystal X-ray study. Crystallographic study reveals that these ligands exist in the amine-one tautomeric form in the solid state. NMR study also suggests the existence of the amine-one form in solution at room temperature. Ab initio calculations for representative ligand HL¹ has been carried out to know the coordination site of the ligand. Novel vanadium Schiff base complexes of these ligands with general formula [OV(L^1–7)₂(H₂O)] have been prepared by interaction of aqueous solution of vanadyl sulfate pentahydrate with DMF solution of the appropriate ligands. The resulting complexes have been characterized on the basis of elemental analysis, vanadium determination, molar conductance and magnetic measurements, thermo gravimetric analysis, infrared and electronic spectral studies. Suitable distorted octahedral structures have been proposed for these complexes.     

Synthesis and magnetic properties of μ-phenolato copper (Ⅱ) binuclear complexes with different exogenous bridges

The syntheses and magnetic properties are reported for a series of copper(Ⅱ) complexes prepared from a pentadentate binucleating ligand 2,6-diformyl-4-methylphenol di(benzoyl-hydrazone) (H3L). These complexes incorporate different exogenous ions (X-) into a bridging position to form copper(Ⅱ) binuclear complexes of the formula [Cu2(H2L)X]2+, where X-= Br-(1), Cl-(2), HO-(3), C2H5O-(4) and C3H3N2- (5). The complexes have been characterized with variable temperature magnetic susceptibility (4.2-300 K) and the observed data were fit to those from a modified Bleaney-Bowers equation by least-squares method, giving the exchange integral 2J = -6.2 cm-1 for 1, -76.4 cm-1 for 2, -241.9 cm-1 for 3, -231.1 cm-1 for 4 and -343.8 cm-1 for 5. This suggested that there is an antiferromagnetic interaction between the Cu(Ⅱ) ions and the sequence of the effect of some exogenous bridging ligands on magnetic coupling is corresponding to that in spectrochemical series.     

Synthesis and characterization of binuclear transition metal–rhenium(VII) complexes with bridging cyanide ligands

Reacting transition metal complexes in low oxidation states, containing one or two cyanide ligands, with methyltrioxorhenium(VII) leads to bridged mixed metal compounds in good yields. The Re(VII) core is then surrounded by five or six ligands, respectively. The strength of these CN bridges and thus the stability of the newly generated bimetallic compound strongly depends on the donor strength of the ligands surrounding of the Cr/Mo/W or Fe moiety. The stability of the mixed metal molecules is reflected in the temperature dependent behavior of their ¹⁷O-NMR spectra, in their IR (Re=O) stretching frequencies and force constants, as well as several other spectroscopic data. UV–vis absorption spectra show the appearance of charge transfer bands. In the case of the mixed Mo/Re complexes the ⁹⁵Mo-NMR spectroscopy is also a helpful tool to examine the donor capability of the Mo moiety. The described compounds also show photosensitivity.     

Synthesis,spectral, thermal and crystallographic investigations on oxovanadium(IV) and manganese(III) complexes derived from heterocyclic β-diketone and 2-amino ethanol

Novel mononuclear oxovanadium(IV) and manganese(III) complexes [VO(L¹)₂·H₂O] (1); [VO(L²)₂·H₂O] (2); [VO(L³)₂·H₂O] (3); [Mn(L¹)₂]ClO₄·H₂O (4); [Mn(L²)₂] ClO₄·H₂O (5); [Mn(L³)₂]ClO₄·H₂O (6) were prepared by condensation of 1 mol of VOSO₄·5H₂O or Mn(OAc)₃· 2H₂O with 2 mol of ligand HL¹, HL² or HL³ (where HL¹ = 4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2- phenyl-2,4-dihydro-pyrazol-3-one; HL²=4-[(2-hydroxy-ethylamino)-methylene]-5-methyl-2-p-tolyl-2,4-dihydro-pyrazol-3-one; HL³=4-{4-[(2-hydroxy-ethyl-amino)-methyl]-3-methyl-5-oxo-4,5-dihydropyrazol-1-yl} benzene sulfonic acid). The resulting complexes were characterized by elemental analyses, molar conductance, magnetic and decomposition temperature measurements, electron spin resonance, FAB mass, IR and electronic spectral studies. From TGA, DTA and DSC, the thermal behaviour and degradation kinetic were studied. Electronic spectra and magnetic susceptibility measurements indicate distorted octahedral stereochemistry of oxovanadium(IV) complexes and regular octahedral stereochemistry of manganese(III) complexes. Hamiltonian and bonding parameters found from ESR spectra indicate the metal ligand bonding is partial covalent. The X-ray single crystal determination of one of the representative ligand was carried out which suggests existence of amine-one tautomeric form in the solid state. The ¹H-NMR spectra support the existence of imine-ol form in solution state. The LC-MS studies sustain the¹H-NMR result. The electronic structure of the same representative ligand was optimized using 6-311G basis set at HF level ab initio studies to predict the coordinating atoms of the ligand.     

Synthesis,characterization, and insulin-enhancing studies of unsymmetrical tetradentate Schiff-base complexes of oxovanadium(IV)

A series of unsymmetrical tetradentate Schiff bases were synthesized by interaction of 2-hydroxy-1-naphthaldehyde, phenylenediamine and salicylaldehyde, or substituted salicylaldehyde in an ethanolic medium. The oxovanadium(IV) complexes and the ligands were synthesized and characterized by elemental analyses, ¹H NMR, infrared, electron paramagnetic resonance, electronic spectra, cyclic voltammetry, and room temperature magnetic susceptibility measurements. The elemental analyses for both the ligands and the metal complexes confirmed purity of the compounds as formulated. Electron paramagnetic resonance spectra of the complexes were measured as powder and in toluene/dichloromethane (9 : 1, v/v) solution at room and liquid N₂ temperatures. The g values, g _o = 1.971, g _⊥ = 1.978, and g = 1.950, are the same for all the complexes examined. The vanadium nuclear hyperfine splitting, A _o = 101–99, A _⊥ = 65–64, A _∥ = 179–177, vary slightly with substituents on the salicylaldehyde. Infrared spectra reveal strong V=O stretching bands in the range 970–988 cm^?1, typical of monomeric five-coordinate complexes. The room temperature magnetic moments of 1.6–1.8 BM for the complexes confirmed that the complexes are V(IV) complexes, with d¹ configuration. Only one quasi-reversible wave is observed for each compound and they all showed redox couples with peak-to-peak separation values (ΔE _p) ranging from 78 to 83 mV, indicating a single step one electron transfer process. Insulin-mimetic tests on C2C12 muscle cells using Biovision glucose assay showed that all the complexes significantly stimulated cell glucose utilization with negligible cytotoxicity at 0.05 µg µL^?1.     

Bioactive versatile azomethine complexes of organotin(IV) and organosilicon(IV)

Diorganotin(IV) and diorganosilicon(IV) derivatives of the types R₂MCl(TSCZ) and R₂M(TSCZ)₂ (where TSCZ is the anion of a thiosemicarbazone ligand, R=Ph or Me and M=Sn or Si) have been synthesized and characterized by elemental analyses, molecular weight determinations and conductivity measurements. The mode of bonding has been established on the basis of IR and ¹H, ¹³C ²⁹Si and ¹¹⁹Sn NMR spectroscopic studies. Some of the representative complexes have also been evaluated for their antimicrobial effects on different species of pathogenic fungi and bacteria in vivoas well as in vitro.The results of these investigations are reported. © 1998 John Wiley & Sons, Ltd.