Oxidation of glyoxylic acid by a mononuclear manganese(IV) complex of 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane: A kinetics and mechanistic study

Nayak, Suprava; Brahma, Gouri Sankhar; Reddy, K. V.; Dash, Anadi C.

doi:10.1016/j.poly.2011.03.032

Cited by 3 publications

(5 citation statements)

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“…This small decreasing trend of k obs distinctly shows the involvement of a radical intermediate from glyoxylic acid which reacted with Mn III (salen) almost instantaneously to maintain the stoichiometry as shown in equation 3but was scavenged by acrylamide causing a decrease in the overall rate constant (k obs ). However, the competitive effectiveness of acrylamide in influencing the radical scavenging was not so significant under these experimental conditions as we did not observe any polymer formation in contrast to the polymerization of this monomer in acidic medium by the redox couple HGL + Mn IV complex reported by Nayak et al 19 Figure 2 displays the repetitive spectral scans of the reaction mixture (250 ≤ λ, nm ≤ 500 nm) at 40 • C, pH = 2.05 over extended time. There is a steady decrease of absorbance at all wavelengths with an isosbestic point at 265 nm.…”

Section: Test Of Free Radicalmentioning

confidence: 47%

“…The details of the procedure adopted has been described by Nayak and co-workers. 19 Our Table 2. Rate data for the reduction of Mn III (salen)(OH 2 ) 2 + by Glyoxalate (Gly) at 40.0 • C and 45.0 (I N = 5/2) as evidenced from the 6 line ESR spectrum of the spent reaction mixture (see figure 1).…”

Section: Product Analysis and Stoichiometrymentioning

confidence: 99%

“…The fast hydration/dehydration equilibria of glyoxylic acid and its conjugate base in water has been wellstudied and discussed at length by Nayak et al 19 The acid and its anion exist in the monohydrate form (gemdiol) to the extent of >99% and 93-95%, respectively. We, therefore, consider the protolytic equilibrium of HGl in terms of the gem-diols:…”

Section: Equilibrium Measurementsmentioning

confidence: 99%

“…The reduction of Mn IV in [Mn IV 3 (µ-O) 4 (Phen)(OH 2 ) 2 ] 4+ by HGl/Gl − have been shown by Mandal and co-workers 24 to follow second order kinetics with the reactivity trend, k red (HGl) > k red (Gl − ), an observation similar to ours but for the proton ambiguity in their case. In a recent study of the oxidation of glyoxylic acid by Mn IV L and Mn III L {L = tetra deprotonated 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane} Nayak and co-workers 19 have unambiguously demonstrated the higher reactivity of HGl relative to that of its conjugate base, Gl − and attributed this reactivity order to the preferential hydrogen bonding effect of HGl.…”

Section: A B Cmentioning

confidence: 99%

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Glyoxylate as a reducing agent for manganese(III) in salen scaffold: A kinetics and mechanistic study

et al. 2014

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The kinetics of oxidation of glyoxylic acid (HGl) by Mn III (salen)(OH 2) + 2 ((H 2 salen = N,Nbis(salicylidene)ethane-1,2-diamine) is investigated at 30.0-45.0 • C, 1.83 ≤ pH ≤ 6.10, I = 0.3 mol dm −3 (NaClO 4). The products are identified as formic acid, CO 2 and Mn II with the reaction stoichiometry, | [Mn III ]/ [HGl]| = 2. The overall reaction involves fast equilibrium pre-association of Mn III (salen)(OH 2) + 2 with HGl and its conjugate base Gl − forming the corresponding inner sphere complexes (both HGl and Gl − being the monohydrate gem-diol forms) followed by the slow electron transfer steps. In addition, the second order electron transfer reactions involving the inner-sphere complexes and HGl/Gl − are also observed. The rate, equilibrium constants and activation parameters for various steps are presented. Mn III (salen)(OH 2)(Gl) is virtually inert to intra molecular electron transfer while the process is facile for Mn III (salen)(OH 2)(HGl) + (10 5 k et = 2.8 ± 0.3 s −1 at 35.0 • C) reflecting the involvement of proton coupled electron transfer mechanism in the latter case. A computational study of the structure optimization of the complexes, trans-Mn III (salen)(OH 2) + 2 , trans-Mn III (salen)(OH 2)(Gl), and trans-Mn III (salen)(OH 2)(HGl) + (all high spin Mn III (d 4) systems), reveals strongest axial distortion for the (aqua)(Gl) complex ; HGl bound to Mn I I I centre by the C=O function of the carboxyl group in the (aqua)(HGl) complex facilitates the formation of a hydrogen bond between the proton of the carboxyl group and the coordinated phenoxide moiety ((O-H.. .O hydrogen bond distance 1.745 Å) and the gem-diols are not involved in H-bonding in either case. A rate comparison for the second order paths: Mn III (salen)(OH 2)(HGl)/Gl) +/0 + HGl/Gl − → products, shows that HGl for the (aqua)(HGl) complex is a better reducing agent than Gl − for the (aqua)(Gl) complex (k HG ∼ 5 k Gl). The high values of activation enthalpy (H = = 93-119 kJ mol −1) are indicative of substantial reorganization of the bonds as expected for inner-sphere ET process.

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Section: Test Of Free Radicalmentioning

confidence: 47%

Section: Product Analysis and Stoichiometrymentioning

confidence: 99%

Section: Equilibrium Measurementsmentioning

confidence: 99%

Section: A B Cmentioning

confidence: 99%

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Glyoxylate as a reducing agent for manganese(III) in salen scaffold: A kinetics and mechanistic study

et al. 2014

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“…

INTRODUCTIONSynthesis and isolation of multidentate carboxamido ligand containing N4O2 donor atoms in the form of amide, amine and phenolate groups have remained a long standing challenge [1][2][3][4][5][6] owing to their varied functionality during complexation. These ligands have proved to be excellent complexing agents for several metal ions such as Mn III/II [6], Fe III/II [7-10], Cr III [11], Co III/II [12][13][14] and Cu II [15], etc.

…”

mentioning

confidence: 99%

Synthesis and Characterization of Cobalt(III) Complex of 1,5-bis(2-Hydroxybenzamido)-3- aza pentane and its Interaction with Glutathione: A Kinetic and Spectrophotometric Study

Aravind

Brahma

Nayak³

2019

Asian J. Chem.

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A new octahedral cobalt(III) complex of 1,5-bis(2-hydroxybenzamido)-3-aza pentane was synthesized and characterized by elemental analysis, UV-visible, IR, mass spectrometry and thermal analysis methods. Oxidative behaviour of the complex towards the physiologically abundant tripeptide, glutathione(GSH) was studied by UV-visible and FT-NMR techniques. Kinetics of electron transfer between the complex and GSH was studied at 25.0 ≤ t/°C ≤ 45.0, 0.025 ≤ [H+]/mol dm-3 ≤ 0.20 and I = 1.0 mol dm-3 (NaClO4). NMR spectra of the reaction mixture were taken as a function of time. Changes observed in the NMR-spectrum during the period of scanning are the initial disappearance of the fine structure and subsequent broadening of the signals of GSH protons. Peaks at (δ, ppm): 2.93 and 2.98, characteristics of Cys-CH2 δ protons in GSH get disappear slowly and new peaks develop at (δ, ppm): 3.33 and 3.38, corresponding to resonating frequencies of Cys-CH2 δ protons in GSSG. Likewise, the peak at (δ, ppm):2.93, characteristic of Cys-CH2 δ proton in GSH is replaced by the resurgence of two peaks at (δ, ppm): 4.3 and 4.1 ppm, commensurate with the resonating frequencies of same set of protons as that of GSH but in a dimeric environment. The time dependent NMR simulation of the reaction reveals that GSH reduces the CoIII moiety successfully, while it gets converted into the dimer, GSSG. The relatively fast transformation of GSH to GSSG as evident from both electronic spectra and NMR studies together with the activation parameters obtained from the temperature dependence of reaction rate suggest that there is no involvement of any bridging group for electron transfer and the redox process may be taking place via outer sphere mechanism.

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Surface engineered environment-stable red-emitting fluorides for white light emitting diodes

Yang

Luo

Wan

et al. 2022

Ceramics International

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Oxidation of glyoxylic acid by a mononuclear manganese(IV) complex of 1,8-bis(2-hydroxybenzamido)-3,6-diazaoctane: A kinetics and mechanistic study

Cited by 3 publications

References 46 publications

Glyoxylate as a reducing agent for manganese(III) in salen scaffold: A kinetics and mechanistic study

Glyoxylate as a reducing agent for manganese(III) in salen scaffold: A kinetics and mechanistic study

Synthesis and Characterization of Cobalt(III) Complex of 1,5-bis(2-Hydroxybenzamido)-3- aza pentane and its Interaction with Glutathione: A Kinetic and Spectrophotometric Study

Surface engineered environment-stable red-emitting fluorides for white light emitting diodes

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