Thionine blue

Methylene blue, new methylene blue, thionine blue, Capri blue, cresyl blue, brilliant cresyl blue, Nile blue, Basle blue, Mel-dola s blue, fast navy blue, new blue, metamine blue, naphthol u, blue, metaphenylene blue, paraphenylene blue, mdamine blue, indazine, neutral blue, muscanne, diphene blue, rhoduline blue, rhoduline sky blue frl ... 

P. 158. Thionine blue G 0.—This dyestuff is closely allied to methylene blue, and its constitution is e.Ypressed by the formula ... 

With thionine blue in phosphate buffer at pH 3 With M-phloxin buffered at pH 6 with phosphate and... 

The Leucothionine blue, formed during the photooxidation of AA sensitized by Thionine blue, is highly fluorescent No data 80 1.6 Pharmaceuticals, juices, soft drinks 1997 147 O... 

Perez-Ruiz, T., C. Martinez-Lozano, V. Tomas, and C. Sidrach. 1997. Flow injection fluorometric determination of ascorbic acid based on its photooxidation by Thionine Blue. Analyst 122 115-118. 

In the case of fluorescence spectra, it is the emission of the radiation from the excited state that is measured, rather than its absorption. This also provides valuable information. As an example, tetraethylorthosilicate (TEOS)-based gels were doped with two optically active organic indicators, thionin and nile blue A. Before trapping in a solgel host, thionin and nile blue A were both evaluated for solvent and protonation effects on their spectral properties. Only extreme pH values provided by HCl, NaOH, and NH4OH produced new absorption and/or fluorescence bands. The absorption and fluorescence spectra revealed a decrease in a pH 11 solution of NH4OH compared to neutral conditions (Krihak et al., 1997). 

Residues of methylene blue in edible animal tissues are of public health concern because tliis dye and its metabolites are mutagenic (74). Metabolism studies in cattle have indicated that methylene blue can be eliminated in urine partly unchanged, partly metabolized to leucomethylene blue, or demethylated to N-methyl homologues of thionin, the completely demethylated metabolite of methylene blue, or reduced in vivo and subsequently eliminated in its leuco-form or in one or more chromogenic substances (75). 

Although the leucometabolite of methylene blue has been repeatedly detected (75, 76), recent research (77) cannot confirm its presence in milk various metabolites at different stages of demethylation, in addition to a methylene blue complex, are found instead. Among these metabolites, a trimethyl derivative called azure A, a dimethyl derivative called azure B, a monomethyl derivative called azure C, and completely demethylated thionin have been positively identified. Further investigation demonstrated that the methylene blue complex was a protein-thionin conjugate, whereas thionin was the residue with the longest residence time in milk (78). 

Examples of striking differences in redox potentials between ground and first triplet states are observed in the oxidizing powers of methylene blue and thionine. In the ground state, the dyes cannot oxidize Fe2+ to Fe +. But when excited in the presence of Fe +, the colour of the dye is bleached. The colour returns on removal of the excitation source. In the long lived triplet state, oxidation potential of the dye increases and the ferrous iron is oxidized to ferric state, the dye itself being reduced to the leuco form. 

Many complex dye molecules form triplet states which undergo facile reduction. Thiazine dyes such as thionine, 49, and methylene blue are photoreduced by a variety of oxidizing agents, including ferrous ion.475... 

A number of dithiolato-metal-dye complexes were synthesized117 by adding thionine (TH), tolusafranine (SAF) or methylene blue (MB) to a mixture of a metal salt and Na2(mnt) or H2(tdt). The composition of the products was determined from elemental analyses and valence state considerations. Peculiar stoichiometries were found, e.g. Mn2(mnt)5(SAF)6(OH)2 11H20, necessitating the assumption that equally unusual structures existed. Nonetheless, the molar absorption coefficients of the maximum absorption were larger for the complexes than the free dyes. In hexa-methylphosphoramide, the metal dithiolene accelerated the rate of photochemical reduction versus the free ligand with TH but retarded the rate for the SAF and MB complexes. 

Organic Systems. The photooxidation and reduction reactions for most organic compounds require two electron processes and are generally irreversible. However, several phenothiazine dyes, such as Thionine and Methylene Blue, function as reversible two electron redox systems. The reversible photobleaching of chlorophyll may also involve a one or two electron process although the exact mechanism is still in doubt. One electron redox processes for organic molecules are possible... 

The patent and open literature were searched for examples of dye sensitized photopolymerization in which a common monomer (acrylamide), and one of several common dyes (thionine, T methylene blue, MB or rose bengal, RB) were used in combination with a stated concentration of an activator. The polymerization conditions (monomer concentration, light intensity absorbed, and extent conversion) were stated in each case chosen for inclusion. The relative photospeed of the system was calculated based on several corrections to the raw data. We here define the relative photospeed of a composition as the inverse of the exposure time t needed to effect some fixed percentage of monomer conversion. 

The quantum yield of fluorescence of many fluorescent substances in solution decreases with increasing concentration. In some cases, e.g., with aqueous solutions of thionine and Methylene Blue, this selfquenching is due to formation of stable dimers in equilibrium with the monomer.78 In other cases, e.g., with solutions of anthracene, perylene, and coronene in solvents such as benzene, chloroform, and kerosene, Bowen and co-workers have shown that quenching takes place by collision17 the self-quenching rate constants obtained are very close to those given in Table I (see also ref. 19). 

Figure 9.13 indicates the typical change in reflection spectra for the thionine reductant system in a PVA matrix coated on paper with a water-repellent property.36 The blue color, with an absorbance of approximately 1.0 at 610nm, faded rapidly upon irradiation with visible light this absorption gradually recovered when the material was stored in a desiccator at constant relative humidity in the absence of light. The recovery was complete except when the exposure was to an extremely intense light. 

As can be seen from Table 9.12, photochromism is also strongly affected by humidity. It is well known that thiazine and its derivatives undergo photoreduction smoothly in the presence of such activated surfaces as silica gel and alumina with water molecules,37 and that methylene blue is also photochemically reduced in acid solution, even with only available water as the reducing agent38 Therefore the water present in polymer films must produce a thionine-water hydration system, which accelerates the rate of the photoreduction of thionine, as well as promoting the contact of reductants by a plasticizer effect. PVA, used as the matrix, can also play the role of reductant, but its extent may be minor as compared with the added reductant. The effect of water is supported by the fact that a less hydrophilic polymer matrix such as poly(methyl methacrylate) does not exhibit photochromism even though the system contains an appreciable amount of reductants. 

C. A. Parker, Photoreduction of methylene blue and thionine by ferrous sulfate, Nature, 182, 245-246 (1958). 

Several other systems have been investigated in this context. An important condition that has to be satisfied while choosing system, is that the free energy of photochemical steady state under sun light illumination should be greater than that when it is dark. Methylene blue and Fe2+, Co-EDTA complex and thionine, and excited tri-bipyridyl complex of Ru2+ and Fe2+ are a few systems that satisfy this condition. The equilibrium in dark with the bipyridyl system is... 

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