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An oxovanadium(IV) complex of dipyridophenazine, as a potent metal-based PDT agent, shows efficient DNA photocleavage activity at near-IR region and high photocytotoxicity in both UV-A and visible light in HeLa cells.

Oxovanadium(IV) and dioxouranium(VI) complexes of 1-(2-pyridylazo)-2-naphthol (PAN) and 4-(2-pyridylazo) resorcinol (PAR) have been prepared and characterised by elemental analyses, various physico-chemical methods and magnetic measurements. The I. R. observations suggest that PAN is coordinated through oxygen and (pyridine) nitrogen, whereas PAR is coordinated through (pyridine) nitrogen and the ortho-hydroxyl group. The spectral-studies suggest that oxovanadium(IV) complexes have the coordination number five and dioxouranium(Vl) complexes have the coordination number six for the cations.

In this brief review the most recent studies and the most relevant aspects of the complexes generated by interaction of carbohydrates and related molecules with the oxovanadium(IV) cation, VO(2+), are presented and discussed. The survey includes complexes of mono-, di- and polysaccharides, and of other molecules related to simple sugars. First studies with conduritols and related molecules are also described. Moreover, complexes of ascorbic and quinic acids and of some peculiar flavonoids are also included. Some comments on the general physicochemical properties of these complexes are made and their biological activities and effects are also briefly discussed.

The hydrolysis of VO 2+ and the complex with sulfate were studied potentiometrically, spectrophotometrically and calorimetrically, in NaCl aqueous solution (0 I ≤ 1 mol L − 1 ) and at t = 25 °C. The formation of two hydrolytic species VO(OH) + and VO 2 (OH) 2 2+ and one complex with sulfate was found, with log β = − 5.65 for the reaction VO 2+ + H 2 O = VO(OH) + + H + , log β = − 7.02 for the reaction 2VO 2+ + 2H 2 O = (VO) 2 (OH) 2 2+ + 2H + and log K = 1.73 for VOSO 4 0 species (at I = 0.1 mol L − 1 and t = 25 °C). For these species, using calorimetric data, Δ H and T Δ S values were also obtained. By using the above values, interactions of VO 2+ with acetate ( ac ), malonate ( mal ), succinate ( suc ), 1,2,3-propanetricarboxylate ( tca ) and 1,2,3,4-butanetetracarboxylate ( btc ) ligands were studied potentiometrically and spectrophotometrically. The formation of ML + , ML 2 0 and MLOH 0 for ac ; ML 0 , MLH + , ML 2 2− and ML 2 H − for mal ; ML 0 , MLH + and MLOH − for suc ; ML − and MLH 0 for tca and ML 2− , MLH − and MLH 2 0 for btc were found. Formation constants are reported at I = 0.1 mol L − 1 , together with SIT parameters for the dependence on ionic strength. By visible spectrophotometric measurements, λ max and e max values for the relevant species in solution were determined.

The complexes formed by oxovanadium(IV) with humic and tannic acids have been studied by ESR. The comparison with simple model systems has shown that the major sites which are involved in metal binding over the pH range 2–6 have spectral parameters similar to those of complexes with carboxylate groups or salicylate and o -catecholate chelating sets. A population of weaker sites has been also observed. However, tannic acid shows pure o -catecholato coordination and, due to the strong chelating ability of this donor set, displaces the oxo-ligand from the VO(IV) ion yielding stable complexes of the tris(catecholato)vanadate(IV) type.

The oxovanadium(IV) complexes of hydroxy- and amino-benzoates have been synthesized and characterised by micro-analysis, magnetic susceptibility measurements, infrared and electronic reflectance spectra. The complexes of the hydroxybenzoates appear to be five-coordinate while their mixed ligand complexes with benzoate and the aminobenzoates are six-coordinate. The influence of carboxylate ions in the ‘anomalous’ behaviour of this class of compounds is discussed.

Two vanadyl complexes of dithiobis(2,4-pentanedione), H 2 acac 2 S 2 , with 1:1:1 (metal—acac 2 S 2 —L, where L = DMSO, py) stoichiometry have been characterized by elemental analysis, IR and optical spectral studies, field desorption mass spectrometry and magnetic susceptibility measurements. It is concluded that trinuclear complexes [VO(acac 2 S 2 )DMSO] 3 ( A ) and [VO(acac 2 S 2 )py] 3 ( B ) are formed, for which cyclic structural forms are proposed.

A simple general route of obtaining very stable octacoordinated non-oxovanadium(IV) complexes of the general formula VL2 (where H2L is a tetradentate ONNO donor) is presented. Six such complexes (1-6) are adequately characterized by elemental analysis, mass spectrometry, and various spectroscopic techniques. One of these compounds (1) has been structurally characterized. The molecule has crystallographic symmetry and has a dodecahedral structure existing in a tetragonal space group Pn2. The non-oxo character and VL2 stoichiometry for all of the complexes are established from analytical and mass spectrometric data. In addition, the non-oxo character is clearly indicated by the complete absence of the strong nuV=O band in the 925-1025 cm-1 region, which is a signature of all oxovanadium species. The complexes are quite stable in open air in the solid state and in solution, a phenomenon rarely observed in non-oxovanadium(IV) or bare vanadium(IV) complexes.

Recently, we reported that [meso-tetrakis(4-sulfonatophenyl)porphyrinato]oxovanadium(IV)(4-), VO(tpps), shows in-vitro insulin-mimetic and in-vivo anti-diabetic activity in streptozotocin (STZ)-induced type 1 diabetic mice. This result prompted us to examine its ability in type 2 diabetic model KKAy mice with insulin resistance. We studied the in-vivo anti-diabetic activity of VO(tpps), compared with that of vanadium(IV) oxide sulfate, VS, as control. Both compounds were orally administered at doses of 5–10 mg (0.1-0.2 mmol) V/kg body weight to the KKAy mice for 28 days. VO(tpps) normalized the hyperglycaemia within 15 days, while VS lowered the blood glucose concentration only by a small degree. In addition, metabolic syndromes characterized by insulin and leptin resistance were significantly improved in VO(tpps)-treated KKAy mice compared with those treated with VS. The improvement in diabetes was validated by oral glucose tolerance test and decrease in HbA1c concentration. Based on these observations, VO(tpps) is proposed to be an orally active oxovanadium(IV)-porphyrin complex for treating not only type 2 diabetes but also metabolic syndromes in animals.

The synthesis, X-ray crystal structure, and spectroscopic properties of the new coordination compound [OVIV(HBIMETEN)], [H3BIMETEN = N , N' - (2-hydroxybenzil) -N-(1-methylimidazole-2-yl-methyl)-N'-hydroxyethil-ethylenediamine] are reported as VIVO2+ complex example containing phenolate and 1-methylimidazole coordinated simultaneously to the metal center. The EPR and UV-Vis properties of the title compound are similar to those observed in [OVIV(tf)].

The X-ray structure of [(μ-OCH3)VO(ma)]2 shows the dimer to contain a planar rectangular [(OV)2O2] core and variable-temperature (2−300 K) magnetic susceptibility measurements were found to show strong antiferromagnetism for this dimer (J = −107 cm-1). By comparison with previous reports, an inverse correlation between J and V−V distance was elucidated.

The magnetic susceptibility of the title compound was measured between 1.9 and 300 K. It shows a Curie–Weiss behaviour in the temperature range between 50 and 300 K. Below 40 K, a ferromagnetic interaction between the VO2+ groups is observed, which was also confirmed by an investigation of the magnetization as a function of the magnetic field, at 5 K. The mechanism of the interactions was analyzed theoretically using a high temperature series expansion. An excellent agreement between experimental and theoretical data was obtained with the exchange integral J=2.73 cm−1. The presented results constitute the first direct evidence of the formation of ··VO···VO···VO·· ferromagnetic chains in certain oxovanadium(IV) complexes.

Oxovanadium(IV) complexes have been synthesized and characterized the general composition [VOL(A)], where H2L = salicylidene-o-aminothiophenol A1 = bis(benzylidene)ethylenediamine, A2 = bis(acetophenone)ethylenediamine, A3 = 2,2′-bipyridylamine, A4 = bis(benzylidene) − 1,8-diaminonaphthalene, A5 = thiophene-o-carboxaldeneaniline and A6 = thiophene-o-carboxaldene-p-anisidine. Spectral studies indicate that the oxovanadium(IV) complexes assume a six-coordinate octahedral geometry. The antibacterial activities of the complexes against Salmonella typhi, Escherichia coli and Serratia mercescens are higher as compared to the free ligands, vanadyl sulphate, and the control (DMSO) but of moderate activity as compared to the standard drug (tetracycline).

No Abstract.Nigerian Journal of Chemical Research Vol 5 2000: 17-20

The complex cation [{V(daptsc)(MeOH)}2(mu-O)]2+ [daptsc(2-) = 2,6-diacetylpyridine bis(thiosemicarbazonate)] is the first crystallographically elucidated dimer to possess a [V2O]6+ core, the [V(IV)-O-V(IV)]6+ structural unit, formed by cleavage of the multiple bond in the oxo-cation VO2+, is linear with the oxo group residing on a crystallographic center of inversion, and the temperature dependence of the magnetic data of the dimer is consistent with weak antiferromagnetic coupling of the d1-d1 centers.

Vanadyl sulfate (VS) may reduce oxidative stress related to its hypoglycemic and hypolipidemic effects in diabetes mellitus; besides, as a catalytic element, it may induce lipid peroxidation. Studies investigating effects of VS on the oxidative-antioxidative systems in diabetes yielded conflicting results, and this study was designed to investigate the effects of VS on the oxidative-antioxidative systems in streptozotocin-induced (65 mg/kg) diabetic rats. Vanadyl sulfate was administered in drinking water 0.75 mg/mL during 5 weeks after the induction of diabetes. Thirty-two male Wistar rats were randomly divided into four groups: control (C), control + vanadyl sulfate (C + VS), diabetes (D), and diabetes + vanadyl sulfate (D + VS). Vanadyl sulfate reduced the enhanced glucose, lipid, and tissue malondialdehyde levels and increased the reduced serum paraoxonase and arylesterase activity in the D + VS group. Plasma malondialdehyde level was significantly increased in the C + VS group, compared with the control group. Erythrocyte glutathione peroxidase activity was significantly higher in the C + VS and D + VS groups, compared with the C and the D groups, respectively.The results of the present study suggest that (i) VS has antioxidative potential in streptozotocin-treated rats, and it might be used as a supportive therapeutic agent in uncontrolled diabetes; (ii) VS treatment might play a role in the improvement of serum paraoxonase activity and, thus, inhibit the progression of atherosclerosis; (iii) the prooxidant potential of the VS should be taken into account.

The behaviour of the bis-chelated oxovanadium(IV) complexes formed by acetylacetone (acac) and five of its derivatives was re-examined through a combination of spectroscopic methods in different solvents. It has been found that the complexes are penta-coordinated with a geometry close to the square pyramid and maintain in solution the same structure as in the solid state. The results rule out a cis–trans isomerism of the species VOL2S (L = acac or derivative, S = solvent) in solution. Depending on the coordinating ability of the solvent a sixth molecule can be bound, more or less strongly, to the free axial position of the complexes. The combined application of the electronic absorption and IR spectroscopies allows to establish if the complexes in solution are penta- or hexa-coordinated.

The interaction of the VO2+ cation with meso-2,3-dimercaptosuccinic acid (DMSA) was investigated by electron absorption spectroscopy in aqueous solution at different pH values. The spectral behavior, complemented with a spectrophotometric titration, shows the generation of a [VO(DMSA)2]2− complex in which the oxocation interacts with two pairs of deprotonated-SH groups of the acid. It was also found that DMSA rapidly reduces VO3− to VO2+, which might be chelated by an excess of the acid. DMSA can also produce the partial reduction of a V2O5 suspension at pH=5.2. The results of this study suggest that DMSA might be a potentially useful detoxification agent for vanadium., Centro de Química Inorgánica

A new series of oxovanadium(IV)-lanthanide(III) heteronuclear complexes [Yb(H 2 O) 8 ] 2 [(VO) 2 -(TTHA)] 3 .21 H 2 O (1), {[Ho(H 2 O) 7 -(VO) 2 (TTHA)][(VO) 2 (TTHA)] 0 . 5 } 8.5H 2 O (2), {[Gd(H 2 O) 7 (VO) 2 -(TTHA)][(VO) 2 (TTHA)] 0 . 5 ].8.5.H 2 O (3), {[Eu(H 2 O) 7 ][(VO) 2 (TTHA)] 1 . 5 } 10.5 H 2 O (4), and [Pr 2 (H 2 O) 6 (SO 4 ) 2 ]-[(VO) 2 (TTHA)] (5) (H 6 TTHA=tri-ethylenetetraaminehexaacetic acid) were prepared by using the bulky flexible organic acid H 6 TTHA as structure-directing agent. X-ray crystallographic studies reveal that they contain the same [(VO) 2 (TTHA)] 2 - unit as building block, but the Ln 3 + ion lies in different coordination environments. Although the lanthanide ions always exhibit similar chemical behavior, the structures of the complexes are not homologous. Compound 1 is composed of a [Yb(H 2 O) 8 ] 3 + ion and a [(VO) 2 -(TTHA)] 2 - ion. Compounds 2 and 3 are isomorphous; both contain a trinuclear [Ln(H 2 O) 7 (VO) 2 (TTHA)] + (Ln= Ho for 2 and Gd for 3) ion and a [(VO) 2 (TTHA)] 2 - ion. Compound 4 is an extended one-dimensional chain, in which each Eu 3 + ion links two [(VO) 2 -(TTHA)] 2 - ions. For 5, the structure is further assembled into a three-dimensional network with an interesting framework topology comprising V 2 Pr 2 and V 4 Pr 2 heterometallic lattices. Moreover, 4 and 5 are the first oxovanadium(iv)-lanthanide(III) coordination polymers and thus enlarge the realm of 3d-4f complexes. The IR, UV/Vis, and EPR spectra and the magnetic properties of the heterometallic complexes were studied. Notably, 2 shows unusual ferromagnetic interactions between the VO 2 + and Ho 3 + ions.

The interaction between oxovanadium(IV) and primary hydroxamic acids (aceto- (HAha), benzohydroxamic acid (HBha) or N -hydroxy- N ′-[3-( N -hydroxy-carbamoyl)-propyl]-heptane-1,7-dicarboxamide (H 2 Diha)) as well as the corresponding N -methyl substituted hydroxamic acids (HMeAha, HMeBha, H 2 MeDiha) was studied by pH-potentiometric and pH-stat methods in aqueous solution. Stoichiometry and stability constants of the VO(IV) complexes formed in the pH range 2.0–5.0 were determined and the effect of the substituents on the C or N atoms of the hydroxamic group is discussed. The dihydroxamic acids are more effective oxovanadium(IV) binders than the monohydroxamic ones. Above pH = 4.5–5.0 (depending upon ligand excess), slow redox reaction was found in all the systems studied. During this process, beside the oxidation of VO(IV) to the appropriate V(V)–hydroxamate complex, formation of amides as reduction products was detected under anaerobic conditions. The same reaction can also take place when stirring sparingly soluble VOA 2 type complexes (A: Bha or MeBha) in water in the absence of oxygen. The exact stoichiometry of the redox reaction was determined by pH-stat measurements and found to be 2VO(R 1 CON(R 2 )O) 2 + R 1 CON(R 2 )OH + H 2 O = 2[VO 2 (R 1 CON(R 2 )O) 2 ] − + 2H + + R 1 CON(R 2 )H (R 1 : CH 3 , C 6 H 5 ; R 2 : H, CH 3 ) for the monohydroxamates. The N -methyl hydroxamic acids tend to oxidise VO 2+ significantly slower than the corresponding primary ones.

Single crystals of the title compound have been prepared hydrothermally. Vanadate tetrahedra and distorted oxovanadium octahedra form layers, linked by two independent Cu atoms located on inversion centres. Each Cu atom is surrounded by six O atoms, forming an octahedron distorted by Jahn-Teller elongation. One of the two independent interlayer spaces bridged by the Cu atoms is significantly more compact than the other.

The interaction of oxovanadium(IV) (VO2+) in aqueous solution with commercial calcium hydroxyapatite (CAP) has been studied. VO2+ ions are adsorbed on the surface of CAP by coordination to OH groups, without modification of the crystalline lattice. The extent of the adsorption is followed by chemical analysis, ESR and IR spectroscopy. Results are compared with those obtained for VO2+/synthetic calcium hydroxyapatite (HAP), reported by us in previous works. The uptake is better than the observed for HAP. The maximum adsorption is observed at pH 3.5 and 288 K. We conclude that VO2+ is indeed adsorbed on CAP and the extent of adsorption depends on the pH and temperature.

Optically pure 1,1’-binaphthol and its derivatives have been evaluated as versatile chiral auxiliaries and ligands in asymmetric transformations. Research in this area has provided many efficient and useful methods for the preparation of key chiral building blocks, some of which have been used for the construction of complex natural products.[1] They have also been extensively applied to the preparation of chiral organic materials.[2] The wide-ranging and important applications of such compounds in organic synthesis have stimulated great interest in developing efficient methods for their preparation.[3] Compared to the well-established resolution of racemic binaphthol for the preparation of optically pure BINOL,[3a±f] catalytic asymmetric preparation of chiral binaphthols has developed much more slowly. The discovery of efficient catalysts for the highly enantioselective formation of optically active binaphthol and its derivatives is an attractive target. The oxidative coupling of 2-naphthols in the presence of a catalytic amount of a copper complex of a chiral amine has provided several promising results, but high enantioselectivity has been achieved only for the coupling of 3carboalkoxyl-2-naphthols (93% ee).[4] A photo-activated chiral [RuII(salen)(NO)] complex catalyzes the aerobic oxidative coupling of 2-naphthols with 33±71% ee.[5] Chen et al. and Uang et al. independently designed similar oxovanadium(iv) complexes of chiral Schiff bases for the asymmetric oxidative coupling of 2-naphthols with moderate enantioselectivities of up to 62% ee.[6] We developed the catalyst (R,S)-1c for the oxidative coupling of 2-naphthol with high enantioselectivity, and found that the chiral centers on the amino acid part and the axially chiral binaphthyl unit are both crucial to stereocontrol by the catalyst.[7] However, a drawback is that the chiral oxovanadium complex must be prepared from an optically pure 3,3’diformyl-2,2’-dihydroxy-1,1’-binaphthol and (S)-amino acid. The catalyst is only highly enantioselective when the two COMMUNICATIONS

Polydentate bridging ligands can be used to link small polyoxo-alkoxo-metalate units to form supramolecular clusters. In the title compound, twelve μ4 -bridging squarato groups connect eight trinuclear methoxo-oxo-vanadate units to form a tetradodecanuclear cubic framework, in whose cavity six n-butyl groups of the tetra-n-butylammonium cations are anchored.

New tetradentate Schiff-base oxovanadium(IV) complexes [VOL′]SO4 (where L′=tetradentate ligands derived from 2,4-dihydroxy 5-acetyl acetophenone and substituted diamines) were prepared and characterized by physico-chemical techniques. All the complexes are monomeric in nature and a square-pyramidal geometry is proposed. Various ligand-field and molecular-orbital parameters have been calculated.

We report the synthesis and study of a new series of oxovanadium (IV) dithiocarbamate adducts and derivatives with pyridine and cyclohexyl, di-iso-butyl, di-n-propyl, anilin, morpholin, piperidin and di-iso-propyl amines. The complexes have been characterized by analytical, magnetochemical, IR, visible-UV spectral and thermal studies, and are assigned the formulas [VO(L)2].py, where L=cyclohexyl, di-iso-butyl, di-n-propyl, anilin dithiocarbamate and [VO(OH)(L)(py)2]OH.H2O (L=morpholin, piperidin and di-iso-propyl dithiocarbamate). The effect of the adduct formation on the pV=0 bound is discussed in terms of the IR (V=O, V-S and V-N stretching frequencies) and electronic spectra (d-d transitions).

Invited for the cover of this issue is the group of Teresa Santos-Silva from Universidade Nova de Lisboa and Joao da Costa Pessoa, Universidade de Lisboa, Portugal. The cover image shows a representation of the HEWL–VIVO(pic)2 adduct (HEWL: hen egg white lysozyme; pic: picolinato).

A novel bis(6-ethylpicolinato)(H 2 O)oxovanadium(IV) complex (VO(6epa) 2 ·(H 2 O)) was prepared and its structure was revealed by X-ray analysis (space group Pc(#7), a =10.838(2), b =11.148(5), c =16.642(3) A, and Z =2). Because VO(6epa) 2 ·(H 2 O) exhibited higher in vitro insulinomimetic activity compared to that of vanadyl sulfate in terms of inhibition of free fatty acid (FFA) release from isolated rat adipocytes in the presence of epinephrine, its in vivo effect on whether the complex has a blood glucose normalizing effect was examined in KK-A y mice, a model animal of type 2 diabetes mellitus. VO(6epa) 2 ·(H 2 O) was found to normalize the high blood glucose levels of KK-A y mice when given intraperitoneally at doses of 49 μmol/kg body weight for the first 4 days and then 39 μmol/kg body weight for 10 days. In addition, VO(6epa) 2 ·(H 2 O) improved glucose tolerance ability as examined by the oral glucose test and seemed to have little toxicity in terms of serum parameters. VO(6epa) 2 ·(H 2 O) showed higher normoglycemic activity than bis(6-methylpicolinato)oxovanadium(IV) (VO(6mpa) 2 ) at the same dose. These results indicated that greater enhancement of the blood glucose normalizing effect in KK-A y mice by ethyl substitution compared to methyl substitution may be due to its being more strongly lipophilic.

A series of vanadium(III) and oxovanadium(IV/V) compounds with the ligands, N-(2-nitrophenyl)pyridine-2-carboxamide (Hpycan), N-(phenyl)pyridine-2-carboxamide (Hpheca), and N-(2-pyridyl)acetamide (Hpyra), containing the amide functionality, was prepared and characterized both in solution and in solid state. All vanadium compounds contain a vanadium-amide oxygen bond. Crystal data for [VOCl(2)(OC(2)H(5))(Hpheca)] (4) are monoclinic; P2(1)/a; a = 12.668(5) A, b = 8.084(3) A, c = 17.222(6) A, alpha = 108.148(12) degrees; Z = 4. In addition to the synthesis and crystallographic studies, the optical, infrared, and magnetic properties of these compounds are reported. Electron paramagnetic resonance [of oxovanadium(IV) species] and (1)H, (13)C{(1)H}, and (51)V nuclear magnetic resonance [of oxovanadium(V) compounds] properties are reported as well.

The oxovanadium (IV) complex [VOL2].5H2O (1) and the oxovanadium(V) complexes K[VOL2O].4H2O) (2), [VOL2OH] (3) and [VOL2OCH3] (4) (L = potassium salt of 7-iodo-8-hydroxyquinoline-5-sulfonic acid) were prepared and characterized. The IR spectra of the solids were recorded and discussed in comparison with those of other similar compounds. The electronic absorption spectra, in different solvents, were also analyzed. Pre-resonance Raman measurements, performed with the first two mentioned complexes, reinforce some of the spectroscopic assignments., Centro de Química Inorgánica

Different aspects of the coordination chemistry of oxovanadium(IV) and oxovanadium(V), relevant to the bioinorganic chemistry of vanadium, are presented. Some of the investigated complexes are good models for different aspects of the metabolism and detoxification of vanadium or for a better characterization and understanding of the structural and electronic peculiarities of the coordination spheres of VO2+ and VO2+ in biomolecules. Their structural, spectroscopic and magnetic properties are briefly discussed. The investigated systems include ligands such as reduced and oxidized glutathione, L-ascorbic acid, nucleotides and related systems, carbohydrates, phosphates, carboxylic acids, oxine derivatives and some others.

A vanadyl complex, bis(6-methylpicolinato)oxovanadium(IV), VO(6MPA), with VO(N2O2) coordination mode, was found to exhibit a normoglycemic effect on KKAy mice with hereditary noninsulin-dependent diabetes mellitus with daily oral administration.

The title compound {systematic name: bis[1,4(η5)-cyclopentadienyl]hexakis(μ-diethyl phosphito)-1:2κ6 P:O;3:4κ6 O:P-μ-oxalato-2:3κ4 O 1,O 2:O 1′,O 2′-dioxido-2κO,3κO-1,4-dicobalt(III)-2,3-divanadium(IV)}, [Co2V2(C5H5)2(C2O4)(C4H10O3P)6O2], is an oxalate-bridged dinuclear complex of oxovanadium(IV). The geometric center of the dimer lies on an inversion center. The unique Co atom is bonded to three P atoms and a cyclopentadienyl ring. The unique V atom has six O atom neighbors in an approximately octahedral arrangement; the V—O bond trans to the V=O bond is significantly lengthened.

[VO(C 15 H 22 BN 6 )(C 7 H 14 NS 2 ) cristallise dans P2 1 /n avec a=9,838, b=20,683, c=14,029 A, β=106,356, Z=4; affinement jusqu'a R=0,049. L'atome central V adopte une geometrie de coordination octaedrique deformee dans laquelle une face de l'octaedre est occupee par le coordinat tridente tris(«3,5»-dimethyl-«1»-pyrazolyl) hydroborate et la face opposee par les coordinats oxo et dipropyldithiocarbamato. La structure du complexe mononucleaire est comparee avec celle du complexe analogue diethyldithiocarbamato

Solvent effects on the electronic absorption spectra of oxovanadium(IV) β-diketonates are discussed. It has been found that positions of the long-wave-length bands can be described in terms of the donor-acceptor concept including the donor numbers and the acceptor numbers.

[VCl 2 O(C 4 H 9 NO) 2 ] cristallise dans P2 1 2 1 2 1 avec a=8,635, b=12,237, c=13,683 A, Z=4, affinement jusqu'a R=0,043. Le complexe a une structure bipyramide rhomboedrique avec les deux coordinats chloro et l'oxygene vanadyle dans un plan quadratique

Six VO²⁺ complexes of 8-hydroxyquinoline (oxine) and of some of its mono- and dihalogenated derivatives have been prepared. The complex of 5-chloro-oxine is very unstable and oxidizes rapidly, generating a V(V) complex of stoichiometry VO(QCl)₂OH which could also be prepared in pure form. The infrared spectra of all complexes have been recorded and are discussed in detail. The complexes containing halogenated ligands appear as polymeric species, interacting through V=O...V=O bridges. The magnetic moments, investigated at room temperature, indicate completely quenched orbital contributions. The analysis of the electronic spectra reveals very complex solution behaviour including, oxidation phenomena, ligand loss, and interaction with the solvent., Facultad de Ciencias Exactas

Vanadyl-meso-tetrakis(4-sulfonatophenyl)porphyrin, VOTPPS, was synthesized and evaluated for its in vitro and in vivo insulin-mimetic activities in streptozotocin (STZ)-induced diabetic mice. Based...

The title vanadium complex, [VClO(C16H22N4)]ClO4, of the tetradentate ligand N,N′-di­methyl-N,N′-bis(2-pyridyl­methyl)­ethane-1,2-di­amine was obtained from air oxidation of a mixture of the ligand and VCl3 in wet methanol.

The V atom in the title compound, [V(C13H10NO2)(C18H16N2O3)O], is O,O′-chelated by an N-benzoyl­hydroxy­laminate ligand and O,N,O′-chelated by a benzoyl­acetone 4-methoxy­benzoyl­hydrazonate ligand. The oxo O atom occupies the sixth coordination site of the octahedral coordination.

The crystal structure of the oxovanadium(IV) complex (CH3C5H5O)2VOCl2 was determined. The molecule has trigonal bipyramidal geometry, with oxygen atoms of cyclopentenones in axial positions and oxygen and two chlorine atoms in equatorial positions. Copyright © 2005 John Wiley & Sons, Ltd.

In the title compound, [VO(H2O)5](C7H5O6S)2·2H2O, the VIV atom is six-coordinated by O atoms (one vanadyl neighbour and five water mol­ecules) in a distorted octahedral configuration. The complex also contains two uncoordinated sulfosal­icylate anions and two uncoordinated water mol­ecules. Numerous O—H⋯O hydrogen bonds result in the formation of a three-dimensional network.

The equilibrium structure, harmonic vibrational frequencies, dipole moment derivatives and the dissociation energy of the title VO(acac)2 complex have been investigated using ab initio effective core potential and all-electron calculations. In accordance with experimental data, the calculations, performed at the Hartree–Fock (HF) level of theory, indicate a pyramidal C2v arrangement of the molecule with optimized geometrical parameters in very good agreement with experimental values. The simple HF treatment consistently reproduces the experimental IR features, both in terms of energy and intensity, thus allowing a complete, unambiguous assignment. The VO—(acac)2 bond dissociation energy has been evaluated by single-point MP2 calculations at the HF optimal geometry and is in satisfactory agreement with the experimental value.

Bis(2-[α-hydroxyalkyl/aryl]benzimidazolato)dioxovanadates(V) dihydrates, as their potassium salts, were prepared by the reaction of [VO(acac)2] with the respective benzimidazole followed by aerial oxidation in presence of KOH. An octahedral structure has been proposed for these complexes on the basis of IR, electronic and 1H NMR spectral studies, and thermogravimetric analysis.