Oxobis(2,4-pentanedionato)vanadium(IV), a Redetermination

Shuter, E.; Rettig, S. J.; Orvig, Chris

doi:10.1107/s0108270194010462

Cited by 18 publications

(15 citation statements)

References 3 publications

(4 reference statements)

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“…The lengthening of V1-O2 in 6 is due to its coordination to the metal centre of the terminal [VO (acac) (acac) 2 ] where the metal centre is in square-pyramidal geometry. [7] For the same reason the displacement of the vanadium(IV) centre from the O 4 square-plane formed by the two acetylacetonate ligands towards the terminal oxido group is significantly less [0.365(2) Å] in 6 than the displacement [0.5447(4) Å] observed in the structure of [VO(acac) 2 ]. [7] However, the V2=O8 bond length [1.585(4) Å] is very similar to that…”

Section: X-ray Structuresmentioning

confidence: 92%

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Divanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) Complexes

Sarkar

Pal

2009

Eur J Inorg Chem

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Keywords: Vanadium / Mixed-valent compounds / EPR spectroscopy / Redox chemistry / Localized valenceIn an acetonitrile/water mixture, reactions of the N, NЈ-bis(diacetyl)hydrazine (H 2 diah), bis(acetylacetonato)oxidovanadium(IV) [VO(acac) 2 ] and monodentate N-coordinating heterocycles (hc) in a 1:2:2 mol ratio provide yellow divanadium(V) complexes of formula [(hc)O 2 V(µ-diah)VO 2 (hc)] (1, hc = imidazole; 2, hc = pyrazole; 3, hc = 3,5-dimethyl pyrazole). On the other hand, in the same solvent mixture reactions of the same reagents in a 1:4:2 mol ratio produce green linear tetravana-(4, hc = imidazole; 5, hc = pyrazole; 6, hc = 3,5-dimethyl pyrazole). The complexes 1-6 have been characterized by elemental analysis, magnetic susceptibility, and various spectroscopic and electrochemical measurements. The X-ray crystal structures of 1, 3 and 6 have been determined. In all three structures, the diazine ligand diah 2-is in trans configuration. Metal-centred bond parameters are consistent with the localized electronic structure IntroductionThe chemistry of multinuclear oxido-bridged vanadium complexes has been a subject of continuous interest over the past two decades because of the biochemical importance of these species and their potential use as therapeutic agents and oxidation catalysts.[1] We have been working on oxidovanadium(IV/V) complexes with acid hydrazide based Schiff bases for some time.[2] Recently we reported a coordinatively unsymmetrical complex (variation in the ligands bonded to the two metal centres) of the mixed valence syn-{OV(µ-O)VO} 3+ core that is of trapped valence character in the solid state as well as in solution at ambient temperature.[2h] Before this, there was a solitary report on a complex with the same core, where the two tridentate ligands attached to the two metal centres differ only in the substituent on the aromatic fragment, [3l] and there were very few examples of the {OV(µ-O)VO} 3+ with a valence localized electronic structure in the fluid state. [3g,3i,3l] Compared to dinuclear species, tetranuclear complexes composed of two {OV(µ-O)VO} 3+ units are extremely rare. To the best of our knowledge only three structurally characterized complexes [a]

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Section: X-ray Structuresmentioning

confidence: 92%

“…[7] The V1···V2 distance and the V1-O2-V2 bridge angle in the {OV(µ-O)VO} (3) with the atom numbering schemes. All non-hydrogen atoms are represented by their 50 % probability thermal ellipsoids.…”

Section: X-ray Structuresmentioning

confidence: 99%

Divanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) Complexes

Sarkar

Pal

2009

Eur J Inorg Chem

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“…complexes with V-O, V-N, and V-S bonds: [VO(H 2 O) 5 ] 2? (1) [51], [VO(acac) 2 ] (2), where acac is acetylacetonato(-) [52], [VO(ma) 2 ] (3), where ma is maltolato(-) [53], [VO(salen)] (4), where salen is N, [56], [VO(tma) 2 ] (7), where tma is 2-methyl-3-oxy-4H-pyran-4-thionato(-) [57], [VO(mnt) 2 ] 2-(8), where mnt is 1,2-dicianoethylene-1,2-dithiolato(-) [58], and [VO(edt) 2 ] 2-(9), where edt is ethane-1,2-dithiolato(2-) [59]. The functionals B3LYP, B3PW91, and B3P86, coupled with the basis set 6-311g, were used; for the structures containing V-S bonds, diffuse and polarization functions were also added on the sulfur atom.…”

Section: Validation Of the Dft Methodsmentioning

confidence: 99%

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

et al. 2012

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Density functional theory (DFT) methods were used to simulate the environment of vanadium in several V proteins, such as vanadyl-substituted carboxypeptidase (sites A and B), vanadyl-substituted chloroplast F(1)-ATPase (CF(1); site 3), the reduced inactive form of vanadium bromoperoxidase (VBrPO; low- and high-pH sites), and vanadyl-substituted imidazole glycerol phosphate dehydratase (IGPD; sites α, β, and γ). Structural, electron paramagnetic resonance, and electron spin echo envelope modulation parameters were calculated and compared with the experimental values. All the simulations were performed in water within the framework of the polarizable continuum model. The angular dependence of [Formula: see text] and [Formula: see text] on the dihedral angle θ between the V=O and N-C bonds and on the angle φ between the V=O and V-N bonds, where N is the coordinated aromatic nitrogen atom, was also found. From the results it emerges that it is possible to model the active site of a vanadium protein through DFT methods and determine its structure through the comparison between the calculated and experimental spectroscopic parameters. The calculations confirm that the donor sets of sites B and A of vanadyl-substituted carboxypeptidase are [[Formula: see text], H(2)O, H(2)O, H(2)O] and [N(His)(||), N(His)(⊥), [Formula: see text], H(2)O], and that the donor set of site 3 of CF(1)-ATPase is [[Formula: see text], OH(Thr), H(2)O, H(2)O, [Formula: see text]]. For VBrPO, the coordination modes [N(His)(||), N(His)(∠), OH(Ser), H(2)O, H(2)O(ax)] for the low-pH site and [N(His)(||), N(His)(∠), OH(Ser), OH(-), H(2)O(ax)] or [N(His)(||), N(His)(∠), [Formula: see text], H(2)O] for the high-pH site, with an imidazole ring of histidine strongly displaced from the equatorial plane, can be proposed. Finally, for sites α, β, and γ of IGPD, the subsequent deprotonation of one, two, and three imidazole rings of histidine and the participation of a carboxylate group of a glutamate residue ([N(His)(||), [Formula: see text], H(2)O, H(2)O], [N(His)(||), N(His)(||), [Formula: see text], H(2)O], and [N(His)(||), N(His)(||), [Formula: see text], OH(-), [Formula: see text]], respectively) seems to be the most plausible hypothesis.

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“…In both cases the chelates are synthesized in aqueous solution under refluxing conditions and crystallized upon cooling the reaction mixture [30, 61]. The molecular structure of VO(malto) 2 in crystals displays C 2 symmetry having only an internal molecular dyad coincident with the V=O bond while VO(acac) 2 displays C 2v symmetry [30, 62, 63]. In both chelates, the vanadium atom lies approximately 0.3 – 0.6 Å above the plane defined by the four oxygen-donor atoms with the V=O bond perpendicular to the plane.…”

Section: Structure Of Vanadyl (Vo2+) Chelates In Solutionmentioning

confidence: 99%

“…S represents a solvent molecule in the cis conformation. Both complexes exhibit trans conformations in crystals, as determined through X-ray crystallographic studies [30, 62, 63]. In solution, VO(acac) 2 remains in a trans conformation while VO(malto) 2 acquires an equatorially coordinated solvent molecule and one of the maltolato ligands switches an oxygen-donor atom to the axial site opposite the vanadyl oxygen atom.…”

Section: Figurementioning

confidence: 99%

The structural basis of action of vanadyl (VO2+) chelates in cells

Makinen

Salehitazangi

2014

Coordination Chemistry Reviews

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Much emphasis has been given to vanadium compounds as potential therapeutic reagents for the treatment of diabetes mellitus. Thus far, no vanadium compound has proven efficacious for long-term treatment of this disease in humans. Therefore, in review of the research literature, our goal has been to identify properties of vanadium compounds that are likely to favor physiological and biochemical compatibility for further development as therapeutic reagents. We have, therefore, limited our review to those vanadium compounds that have been used in both in vivo experiments with small, laboratory animals and in in vitro studies with primary or cultured cell systems and for which pharmacokinetic and pharmacodynamics results have been reported, including vanadium tissue content, vanadium and ligand lifetime in the bloodstream, structure in solution, and interaction with serum transport proteins. Only vanadyl (VO2+) chelates fulfill these requirements despite the large variety of vanadium compounds of different oxidation states, ligand structure, and coordination geometry synthesized as potential therapeutic agents. Extensive review of research results obtained with use of organic VO2+-chelates shows that the vanadyl chelate bis(acetylacetonato)oxidovanadium(IV) [hereafter abbreviated as VO(acac)2], exhibits the greatest capacity to enhance insulin receptor kinase activity in cells compared to other organic VO2+-chelates, is associated with a dose-dependent capacity to lower plasma glucose in diabetic laboratory animals, and exhibits a sufficiently long lifetime in the blood stream to allow correlation of its dose-dependent action with blood vanadium content. The properties underlying this behavior appear to be its high stability and capacity to remain intact upon binding to serum albumin. We relate the capacity to remain intact upon binding to serum albumin to the requirement to undergo transcytosis through the vascular endothelium to gain access to target tissues in the extravascular space. Serum albumin, as the most abundant transport protein in the blood stream, serves commonly as the carrier protein for small molecules, and transcytosis of albumin through capillary endothelium is regulated by a Src protein tyrosine kinase system. In this respect it is of interest to note that inorganic VO2+ has the capacity to enhance insulin receptor kinase activity of intact 3T3-L1 adipocytes in the presence of albumin, albeit weak; however, in the presence of transferrin no activation is observed. In addition to facilitating glucose uptake, the capacity of VO2+- chelates for insulin-like, antilipolytic action in primary adipocytes has also been reviewed. We conclude that measurement of inhibition of release of only free fatty acids from adipocytes stimulated by epinephrine is not a sufficient basis to ascribe the observations to purely insulin-mimetic, antilipolytic action. Adipocytes are known to contain both phosphodiesterase-3 and phosphodiesterase-4 (PDE3 and PDE4) isozymes, of which insulin antagonizes lipolysis only through...

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Oxobis(2,4-pentanedionato)vanadium(IV), a Redetermination

Cited by 18 publications

References 3 publications

Divanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) Complexes

Divanadium(V) and Trapped Valence Linear Tetravanadium(IV,V,V,IV) Complexes

Application of DFT methods to the study of the coordination environment of the VO2+ ion in V proteins

The structural basis of action of vanadyl (VO2+) chelates in cells

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