Kinetics and mechanism of oxidation of 1,10‐phenanthroline by alkaline permanganate

Panari, R. G.; Harihar, Abdulazizkhan L.; Nandibewoor, Sharanappa T.

doi:10.1002/(sici)1099-1395(199904)12:4<340::aid-poc120>3.3.co;2-4

Cited by 3 publications

(3 citation statements)

References 2 publications

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“…Similar results have been observed in the phenanthroline complexes of various metals (28–30) and for the free ligands (18). It would appear that the hyperconjugative interactions of the methyl groups are greatest at the 5, 6 positions, which are also the most easily oxidized positions of the phenanthroline ring (31–33).…”

Section: Resultsmentioning

confidence: 99%

Effect of Ring Methylation on the Photophysical, Photochemical and Photobiological Properties of cis-Dichlorobis(1,10-Phenanthroline)Rhodium(III)Chloride†

Loganathan

Morrison

2006

Photochem Photobiol

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Methylated analogues of cis-dichlorobis(1,10-phenanthroline)rhodium(III)chloride (BISPHEN) have been prepared in order to increase the hydrophobicity of the parent compound, and thus create octahedral rhodium (III) complexes suitable for use as anticancer and antiviral agents that can be photoactivated. The parent complex has been shown in earlier work to be unable to cross through cell membranes. Octamethylation, as in the case of cis-dichlorobis(3,4,7,8-tetramethyl-1,10-phenanthroline)rhodium(III)chloride (OCTBP), provides enough hydrophobicity to be taken up by KB tumor cells. It also provides a higher level of ground-state association with double-stranded DNA and increases the quantum efficiency of photoaquation by greater than 10-fold, relative to BISPHEN. OCTBP forms covalent bonds to deoxyguanosine when irradiated with the nucleoside, as has been seen with the parent complex. Irradiation of OCTBP in the presence of the KB or M109 tumor cell lines using narrow-band UVB (lambda = 311 nm) irradiation initiates a considerable amount of phototoxicity. There is evidence that OCTBP acts as a prodrug (i.e. after passing through the cell membrane the metal complex is photolyzed to cis-chloro aquo OCTBP, which may be the active phototoxic agent). OCTBP and the tetramethyl analogue cis-dichlorobis(4,7-dimethyl-1,10-phenanthroline)rhodium(III)chloride (47TMBP) also show photoaquation upon excitation with visible light (lambda > 500 nm), and indeed, some phototoxicity of KB cells is observed at these wavelengths as well. This is attributed to direct population of photoactive triplet-excited states. These results, together with our earlier studies of cis-dichloro[dipyrido(3,2-a: 2',3'-c)phenazine (1,10-phenanthroline)rhodium(III)chloride (DPPZPHEN) demonstrate that such octahedral rhodium complexes are viable "photo-cisplatin" reagents.

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Section: Resultsmentioning

confidence: 99%

Effect of Ring Methylation on the Photophysical, Photochemical and Photobiological Properties of cis-Dichlorobis(1,10-Phenanthroline)Rhodium(III)Chloride†

Loganathan

Morrison

2006

Photochem Photobiol

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“…Experiments with model compounds such as amino acids (e.g., [11][12][13][14] have shown that the reduction of permanganate by these species at high pHs proceeds via formation of manganate MnO4 2-, hypomanganate MnO4 3-(15), and finally MnO2 or mixed Mn(III)/Mn-(IV) solids (16). Identified reaction products formed upon the permanganate oxidation of amino acids and other model compounds include ammonia, oxalate, CO2, and traces of aldehydes (17)(18)(19)(20). Similar species and, in addition to them, IDA, glycine, and glycolate were identified in solutions of EDTA oxidized at high pHs by Ag(III) (21), and also at circumneutral pHs in the case of oxidation by hydroxyl radicals generated in the H2O2/UV system (22) or with reactive oxygen species activated by zerovalent iron (23).…”

Section: Introductionmentioning

confidence: 99%

Investigation of Mechanisms of Oxidation of EDTA and NTA by Permanganate at High pH

Chang

Korshin

Ferguson

2006

Environ. Sci. Technol.

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Permanganate has been used for oxidation of nuclear wastes containing chelating agents such as ethylenediaminetetraacetic and nitrilotriacetic acids (EDTA and NTA) to improve separation of radionuclides and heavy metals from the wastes, butthe mechanisms of degradation of these and related organic ligands at high pHs have not been studied. EDTA, NTA, and the model compound ethylenediamine (EN) were found to be readily oxidized by permanganate at pH 12-14. The reduction of permangante was accompanied by formation of unstable manganate and dispersed MnO2 particles, which constituted the final product of permanganate reduction. The yields and speciation of EDTA, NTA, and EN breakdown products were affected by the pH and permanganate dose. Iminodiacetic acid (IDA), oxalate, formate, and ammonia were the predominant EDTA and NTA oxidation products. Mineralization of EDTA, NTA, and EN to CO2 was more significant at pH 12. At pH 14 formation of oxalate and deamination to NH3 were the most important reactions. IDA was released upon the oxidation of both EDTA and NTA, but EDTA oxidation yielded no ethylenediaminediacetic acid (EDDA). The speciation of the reaction products indicated that the ethylene group in EDTA was the preferred attack site in oxidations by alkaline permanganate.

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“…The process Mn(VII)-» Mn(IV) can be divided into a number of partial steps and examined seperately. If [OH"] > 0.1 mol dm -3 , permanganate will be reduced to manganate in the first step and, owing to its much lower reactivity, further reaction with manganate will be much slower [5,6,7]. The Mn02 appears practically only after permanganate has completely disappeared from the system.…”

Section: Introductionmentioning

confidence: 99%

Kinetics of Oxidative Deamination and Decarboxylation of L-Asparagine by Alkaline Permanganate: a Mechanistic Approach

Kembhavi¹,

Harihar²,

Nandibewoor³

2001

BioInorganic Reaction Mechanisms

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The kinetics of oxidative deamination and decarboxylation of L-asparagine (L-Aspg) by aqueous alkaline permanganate at constant ionic strength of 0.50 mol dm -3 were studied spectrophotometrically. The reaction exhibits first-order kinetics in [permanganate ion] and fractional-order dependences in [L-Aspg] and [alkali]. Initially added products such as aldehyde, ammonia and manganate have no significant effect on the rate of reaction. An increase in ionic strength and a decrease in dielectric constant of the medium increase the rate. The oxidation process in alkaline medium has shown to proceed via two paths: One a substrate dependent path, the other a substrate independent path. The constants involved in the mechanism were evaluated. There is a good agreement between observed and calculated rate constants. The activation paramaters with respect to slow step of path I and path II were calculated.

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Kinetics and mechanism of oxidation of 1,10‐phenanthroline by alkaline permanganate

Cited by 3 publications

References 2 publications

Effect of Ring Methylation on the Photophysical, Photochemical and Photobiological Properties of cis-Dichlorobis(1,10-Phenanthroline)Rhodium(III)Chloride†

Effect of Ring Methylation on the Photophysical, Photochemical and Photobiological Properties of cis-Dichlorobis(1,10-Phenanthroline)Rhodium(III)Chloride†

Investigation of Mechanisms of Oxidation of EDTA and NTA by Permanganate at High pH

Kinetics of Oxidative Deamination and Decarboxylation of L-Asparagine by Alkaline Permanganate: a Mechanistic Approach

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