CV and NMR study on the reaction of Mo(VI) with 3,4-dihydroxybenzoic acid and ascorbic acid in aqueous solution

Litos, Charalambos; Aletras, V.; Hatzipanayioti, Despina; Kamariotaki, Mary; Lymberopoulou-Karaliota, Alexandra

doi:10.1016/j.ica.2006.11.021

Cited by 12 publications

(7 citation statements)

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“…ICP-AES analyses of the solution and the residual solid indicated that 75% of the Mo atoms were exchanged into solution. The 1 H NMR spectrum contained several reasonably well-defined signals in the region of the aromatic ligand protons, which were assigned to [Mo 2 O 5 (3,4-dhb) 2 ] m − (dimer) and [MoO 2 (3,4-dhb) 2 ] m − (monomer) species by comparison with literature data for similar complexes. ,,,,, The ratio of the integrals for the two H 5 signals was approximately 1:1.1 (mononuclear:binuclear), which is in very good agreement with the monomer/dimer molar ratio estimated from the elemental analysis data (Table ). Still, the 1 H NMR result must be treated with caution because the exchange was not complete, and one of the two guest species may be preferentially exchanged.…”

Section: Resultssupporting

confidence: 64%

Investigation of Layered Double Hydroxides Intercalated by Oxomolybdenum Catecholate Complexes

et al. 2008

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Oxomolybdenum(VI) complexes of 3,4-dihydroxybenzoic acid (3,4-H 2dhb) have been incorporated into layered double hydroxides (LDHs) by treatment of the LDH-nitrate (Zn-Al, Mg-Al) or LDH-chloride (Li-Al) precursors with aqueous or water/ethanol solutions of the complex (NMe 4) 2[MoO 2(3,4-dhb) 2].2H 2O at 50 or 100 degrees C. The texture and chemical composition of the products were investigated by elemental analysis and scanning electron microscopy (SEM) with coupled energy dispersive spectroscopy (EDS). Microanalysis for N and EDS analysis for Cl showed that at least 90% of nitrate or chloride ions were replaced during the ion exchange reactions. The final Mo content in the materials varied between 6.5 and 11.6 wt %. Mo K-edge EXAFS analysis, supported by IR, Raman, UV-vis, and (13)C{ (1)H} CP/MAS NMR spectroscopic studies, showed the presence of cointercalated [MoO 2(3,4-dhb) 2] ( m- ) and [Mo 2O 5(3,4-dhb) 2] ( m- ) complexes in proportions that depend on the type of LDH support and the reaction conditions. The binuclear bis(catecholate) complex, with a Mo...Mo separation of 3.16 A, was the major species intercalated in the Zn-Al and Li-Al products prepared using only water as solvent. The X-ray powder diffraction (XRPD) patterns of all the Mo-containing LDHs showed the formation of an expanded phase with a basal spacing around 15.4 A. High-resolution synchrotron XRPD patterns were indexed with hexagonal unit cells with a c-axis of either 30.7 (for Li-Al-Mo LDHs) or 45.9 A (for a Zn-Al-Mo LDH). Fourier maps ( F obs) calculated from the integrated intensities extracted from Le Bail profile decompositions indicated that the binuclear guest species are positioned such that the Mo --> Mo vector is parallel to the host layers, and the overall orientation of the complex is perpendicular to the same layers. The thermal behavior of selected materials was studied by variable-temperature XRPD, thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC).

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Section: Resultssupporting

confidence: 64%

Investigation of Layered Double Hydroxides Intercalated by Oxomolybdenum Catecholate Complexes

et al. 2008

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“…The residue was dissolved in 1 mL of D 2 O (99.9 atom% D) containing acetonitrile (4.21 × 10 −2 M) as internal standard. The formation of dehydroascorbic acid was monitored by 1 H NMR at 4.63, 4.48, and 4.03 ppm with reference to the acetonitrile standard (1.93 ppm). − The amount of dehydroascorbic acid produced was found to be (4.2 ± 0.4) × 10 3 mmol (after subtracting the amount of dehydroascorbic acid formed in a blank without the oxidant); i.e., 2 mol of dehydroascorbic acid is formed from each mole of Ru VI oxidant.…”

Section: Methodsmentioning

confidence: 99%

Kinetics and Mechanism of the Oxidation of Ascorbic Acid in Aqueous Solutions by a trans-Dioxoruthenium(VI) Complex

et al. 2008

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The oxidation of ascorbic acid (H(2)A) by a trans-dioxoruthenium(VI) species, trans-[Ru(VI)(tmc)(O)(2)](2+) (tmc = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), has been studied in aqueous solutions under argon. The reaction occurs in two phases: trans-[Ru(VI)(tmc)(O)(2)](2+) + H(2)A --> trans-[Ru(IV)(tmc)(O)(OH(2))](2+) + A, trans-[Ru(IV)(tmc)(O)(OH(2))](2+) + H(2)A --> trans-[Ru(II)(tmc)(OH(2))(2)](2+) + A. Further reaction involving anation by H(2)A occurs, and the species [Ru(III)(tmc)(A(2-))(MeOH)](+) can be isolated upon aerial oxidation of the solution at the end of phase two. The rate laws for both phases are first-order in both Ru(VI) and H(2)A, with the second-order rate constants k(2) = (2.58 +/- 0.04) x 10(3) M(-1) s(-1) at pH = 1.19 and k(2)' = (1.90 +/- 0.03) M(-1) s(-1) at pH = 1.24, T = 298 K and I = 0.1 M for the first and second phase, respectively. Studies on the effects of acidity on k(2) and k(2)(') suggest that HA(-) is the kinetically active species. Kinetic studies have also been carried out in D(2)O, and the deuterium isotope effects for oxidation of HA(-) by Ru(VI) and Ru(IV) are 5.0 +/- 0.3 and 19.3 +/- 2.9, respectively, consistent with a hydrogen atom transfer (HAT) mechanism for both phases. A linear correlation between log(rate constants) for oxidation by Ru(VI) and the O-H bond dissociation energies of HA(-) and hydroquinones is obtained, which also supports a HAT mechanism.

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“…3,4‐Dihydroxybenzoic acid (protocatechuic acid) also shows antioxidant activity as well as anticarcinogenic and mutagenic activities (Krajka‐Kuźniak et al. , 2004; Litos et al. , 2007).…”

Section: Resultsmentioning

confidence: 99%

“…This compound shows high antioxidant capacity, also as anti-inflammatory and antidepressive activities (Takeda et al, 2002;Norata et al, 2007;Pari & Prasath, 2008). 3,4-Dihydroxybenzoic acid (protocatechuic acid) also shows antioxidant activity as well as anticarcinogenic and mutagenic activities (Krajka-Kuz´niak et al, 2004;Litos et al, 2007). Chlorogenic acid, which is a compound that derives from caffeic acid, shows antioxidant and anti-hepatitis B virus activities (Heo et al, 2007;Wang et al, 2009).…”

Section: Resultsmentioning

confidence: 99%

Juice from king palm (Archontophoenix alexandrae) leaf sheathes: chemical characterisation and use in soft drink formulation

Tramonte

Provesi

Silva

et al. 2011

Int J of Food Sci Tech

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The heart of palm is a food extracted from several species of palm trees. Only 10-20% of the raw material is transformed into canned hearts of palm, therefore this agro-industry generates a large quantity of solid residue. The aim of this work was to extract and characterise a juice produced from this solid residue. This extract is compared with the traditional fruit juices (orange and pineapple juices), obtaining higher contents of minerals, such as magnesium (22.80 mg ⁄ 100 g) and potassium (276.90 mg ⁄ 100 g), phenolic compounds (gallic, 3,4-dihydroxybenzoic, chlorogenic, syringic and caffeic acids) and high free radical scavenging capacity (expressed as 2,2-diphenyl-1-picrylhydrazyl), which suggest high antioxidant activity. Additionally, a new soft drink was formulated using this king palm juice as its main ingredient. The soft drink samples formulated with this juice had high sensory acceptability and high intention of consumption, which suggests an important and low-cost application for this industrial residue.

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CV and NMR study on the reaction of Mo(VI) with 3,4-dihydroxybenzoic acid and ascorbic acid in aqueous solution

Cited by 12 publications

References 50 publications

Investigation of Layered Double Hydroxides Intercalated by Oxomolybdenum Catecholate Complexes

Investigation of Layered Double Hydroxides Intercalated by Oxomolybdenum Catecholate Complexes

Kinetics and Mechanism of the Oxidation of Ascorbic Acid in Aqueous Solutions by a trans-Dioxoruthenium(VI) Complex

Juice from king palm (Archontophoenix alexandrae) leaf sheathes: chemical characterisation and use in soft drink formulation

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