Redox reactions of [VO(salen)]+/0 couple in acetonitrile: Volume analyses in relation to large chiral recognitions observed for electron self-exchange reactions of [VO(Schiff-Base)]+/0

Sasajima, Yasuhide; Shimizu, Motoharu; Kuroyanagi, Norie; Kishikawa, Nobuyuki; Noda, Kyoko; Itoh, Sumitaka; Takagi, Hideo D.; Inamo, Masahiko

doi:10.1016/j.ica.2005.10.028

Cited by 4 publications

(9 citation statements)

References 20 publications

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“…Self-exchange rates for [VO(salen)] +/0 complexes have been measured in acetonitrile, from stopped-flow kinetic studies of the redox reaction with [Co(phen) 3 ] 2+ and [Co(4,7-Me 2 phen) 3 ] 2+ , using the Marcus/Ratner cross relation. 42 Activation volumes, measured using high pressure stopped-flow methods, were consistent with theoretical values (calculated using the Stranks-Hush-Marcus equation) with axial approach of the oxidized and reduced forms of the vanadium complexes. Aerobic catalytic oxidations mediated by vanadium-containing Keggin-type complexes, viz.…”

Section: Redox Reactionssupporting

confidence: 74%

Reaction mechanisms in solution

Haines

2007

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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Section: Redox Reactionssupporting

confidence: 74%

Reaction mechanisms in solution

Haines

2007

Annu. Rep. Prog. Chem., Sect. A: Inorg. Chem.

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“…The high potential quasi-reversible couple, with redox potentials dependent on substituent, is ascribed to the V(V)/V(IV) redox couple. 12,64,70 The reported redox potentials strongly correlate with Hammett substituent constants, as shown in Table 6. 71 The redox potentials of 1 and 2 are close to the literature value reported for the [VO(salen)] 0/+ redox couple.…”

Section: Physicochemical Characterizationmentioning

confidence: 81%

“…71 The redox potentials of 1 and 2 are close to the literature value reported for the [VO(salen)] 0/+ redox couple. 12,70,72,73 Complex 3, with the highest E 1/2 redox potential in the described family of complexes, requires a larger driving force to be oxidized and as a result the fourth oxidation state of vanadium is better stabilized than in the case of the rest of the complexes.…”

Section: Physicochemical Characterizationmentioning

confidence: 95%

Assemblies of salen-type oxidovanadium(iv) complexes: substituent effects and in vitro protein tyrosine phosphatase inhibition

et al. 2014

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Oxidovanadium(IV) complexes with substituted chiral tetradentate dianionic N,N'-bis-o-hydroxybenzylidene-1,2-propylenediamines were synthesized and their physicochemical properties were characterized using single crystal X-ray diffraction, elemental analysis, ATR FTIR, UV-VIS and EPR spectroscopy, cyclic voltammetry, spectroelectrochemistry and preliminary in vitro protein-tyrosine phosphatase inhibition activity studies. Different 5-substituents in the salicylaldehyde (condensed with 1,2-diaminopropane; 2 : 1) were tested, namely 5-Br (complex 1), 5-Cl (2), 5-NO2 (3) and 5-OCH3 (4). The crystal structures of 1 and 2 show square pyramidal coordination of vanadium and parallel arrangement of monomeric exo isomers in supramolecular dimers. The halogen-halogen interaction of substituents in 5,5'-positions leads to weakening of axial interaction between phenolate O and V in 2, compared to 1. The Br atom takes part in halogen bonding with a vanadyl group in 1. Complex 3 has a linear polymeric structure with a V-O-V asymmetric bridge motif (IR absorption band at 873 cm(-1), separated d-d bands and broad EPR band structure in frozen solution pointing to oligomeric nature) while 4 is monomeric (V=O stretching at 976 cm(-1), broad d-d band structure). Redox potentials of the V(4+)/V(5+) couple lie in the range of -0.14 to 0.21 V (vs. Fc/Fc(+)) and show substantial dependence on the electron withdrawing properties of the substituents. The charge transfer character of the bands present in the range 365-395 nm was confirmed based on UV-VIS spectroelectrochemical experiments. Different assemblies of complex molecules are influenced by the electron withdrawing properties of the 5,5'-substituents, leading to supramolecular dimers (1, 2 and 4) and linear polymeric self-assembly (3). An in vitro study of representative complex 1 showed protein tyrosine phosphatase activity inhibition higher than that of suramin but lower than those of oxidovanadium(IV) sulphate and bis(maltolato)oxidovanadium(IV).

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“…The kinetic data obtained for vanadylsalen complex were parallel to that of vanadyl ion studied indicating the operation of similar mechanism except for the fact that the reaction is more rapid (k s = 0.29 dm 3 mol )1 s )1 ) than the vanadyl ion. The rapid oxidation of the vanadyl salen complex by TBATB can be attributed to the decrease in the redox potential of the V 5+ /V 4+ (1.0 V) couple when it is complexed with a Schiff base (0.85 V) [20] . Since, the kinetic behaviour of the reaction is similar, even when the ligand attached to metal ion is changed, indicate that in the transition state the interaction between the reactants does not take place through the ligand.…”

Section: Discussionmentioning

confidence: 99%

Kinetics and mechanism of vanadium(IV) oxidation by tetrabutylammonium tribromide

Kalantre

Maradur

Gokavi

2007

Transition Met Chem

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The reaction between tetrabutylammonium tribromide(TBATB) and vanadium(IV) has been studied in 50% (v/v) acetic acid under second order conditions. The overall order of reaction is found to be two, unity in each reactant. The reaction involves two single-electron transfer steps generating bromine free radical in the first rate determining step. The test for the formation of free radicals in presence of added acrylonitrile was negative while added toluene increases the rate of the reaction considerably due to its conversion into benzyl bromide. The reaction is retarded by hydrogen ions as a result of protonation prior equilibria of the active reductant, vanadyl acetate. The oxidation of the vanadylsalen complex by TBATB proceeds more rapidly than that of vanadyl acetate but follows the similar kinetic behaviour. Considerable decrease in the entropy of activation of the reaction indicates formation of an ordered transition state between the two reactants and since the kinetic behaviour remains unaltered, even after the change in the ligand attached to the reductant, indicates an interaction between the reactants through the oxygen atom on the vanadyl ion.

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Redox reactions of [VO(salen)]+/0 couple in acetonitrile: Volume analyses in relation to large chiral recognitions observed for electron self-exchange reactions of [VO(Schiff-Base)]+/0

Cited by 4 publications

References 20 publications

Reaction mechanisms in solution

Reaction mechanisms in solution

Assemblies of salen-type oxidovanadium(iv) complexes: substituent effects and in vitro protein tyrosine phosphatase inhibition

Kinetics and mechanism of vanadium(IV) oxidation by tetrabutylammonium tribromide

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