Determination of molar absorptivities of radicals of 18 phenothiazine derivatives

Minakata, Kumagusu; Сузукі, Осаму; Ishikawa, Yasunobu; Seno, Hiroshi; Harada, Naoko

doi:10.1016/0379-0738(92)90108-9

Cited by 10 publications

(6 citation statements)

References 15 publications

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“…In all measurements, the solutions were thermostated to the desired temperature (±0.1°C) with an external Julabo F25 ultrathermostat. The reaction rate was recorded by monitoring the disappearance of the phenothiazines radicals visualized by the decrease in absorbance at 514 nm for phenothiazines radicals electron transitions in accordance with literature data: k max , nm (e max , dm 3 mol -1 cm -1 ): promazine radical, 513(9200) [27], chlorpromazine radical, 525(10200) [27], promethazine radical, 515(9300) [27], and trifluoperazine radical, 502(9000) [28]. In the same visible spectral region, the characteristic electronic transition of the manganese(III)-pyrophosphate ion is observed, k max , nm (e max , dm 3 mol -1 cm -1 ): 513(85).…”

Section: Kinetic Measurementsmentioning

confidence: 99%

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

Wı́sniewska

Rześnicki

Topolski

2011

Transition Met Chem

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The oxidative degradation of phenothiazine derivatives (PTZ) by manganese(III) was studied in the presence of a large excess of manganese(III)-pyrophosphate (P 2 O 7 2-), phosphate (PO 4 3-), and H ? ions using UV-vis. spectroscopy. The first irreversible step is a fast reaction between phenothiazine and manganese pyrophosphate leading to the complete conversion to a stable phenothiazine radical. In the second step, the cation radical is oxidized by manganese to a dication, which subsequently hydrolyzes to phenothiazine 5-oxide. The reaction rate is controlled by the coordination and stability of manganese(III) ion influenced by the reduction potential of these ions and their strong ability to oxidize many reducing agents. The cation radical might also be transformed to the final product in another competing reaction. The final product, phenothiazine 5-oxide, is also formed via a disproportionation reaction. The kinetics of the second step of the oxidative degradation could be studied in acidic phosphate media due to the large difference in the rates of the first and further processes. Linear dependences of the pseudo-first-order rate constants (k obs ) on [Mn III ] with a significant non-zero intercept were established for the degradation of phenothiazine radicals. The rate is dependent on [H ? ] and independent of [PTZ] within the excess concentration range of the manganese(III) complexes used in the isolation method. The kinetics of the disproportionation of the phenothiazine radical have been studied independently from the further oxidative degradation process in acidic sulphate media.

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Section: Kinetic Measurementsmentioning

confidence: 99%

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

Wı́sniewska

Rześnicki

Topolski

2011

Transition Met Chem

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“…The first is reversible and results in the formation of a colored cation-radical. The second, irreversible, giving rise to the colorless sulfoxide [2].…”

Section: Introductionmentioning

confidence: 99%

Spectroelectrochemical determination of chlorpromazine hydrochloride by flow-injection analysis

Daniel

Gutz

2005

Journal of Pharmaceutical and Biomedical Analysis

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“…5) Minakata et al 6) reported that phenothiazines changed to dierent colored radicals following their oxdation with the rea gent and the radicals produced were stable.…”

Section: Compounding Test With Acidic and Basic Rea Gentsmentioning

confidence: 99%

Coloration of Phenothiazines with Metal-containing Drugs

et al. 2004

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We studied the color change of phenothiazines and metalcontaining drugs after compound formation, followed by use of FTRaman spectrocopy to observe any structural changes in them. When 6 phenothiazines (thioridazine hydrochloride, prochlorperazine maleate, levomepromazine maleate, chlorpromazine phenolphthalinate, uphenazine maleate and perphenazine fendiate) formed compounds with natural aluminum silicate, the color change was accompa nied by a shift of FTRaman signals. These changes could be attributed to the structural changes of phenothiazines. This present observation can be then used in advance to avoid coloration of phenothiazines during preparative procedures with metalcontaining drugs such as antacids.

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Determination of molar absorptivities of radicals of 18 phenothiazine derivatives

Cited by 10 publications

References 15 publications

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

Spectroelectrochemical determination of chlorpromazine hydrochloride by flow-injection analysis

Coloration of Phenothiazines with Metal-containing Drugs

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