Thionin

Note The literature is exclusively devoted to Thionin chloride however, Thionin acetate is certified by Biological Stain Commission (BSC). 

7-diamino-, acetate 3,7-Diaminophenothiazin-5-ium acetate Thionin Thionin acetate Thionin acetate 

Merck Index Number Not listed (Chloride listed  

Chemical/Dye Class Phenothiazine Molecular Formula C14H13N3O2S Molecular Weight 287.34 Physical Form Dark green powder Solubility Soluble in water, ethanol Melting Point 200 °C pAa 2.5, 11.3 Absorption (Xmax) 598 nm Emission (X ax) 625 nm Synthesis Synthetic methods  

Staining Applications Bacteria viruses nucleic acids glomerular deposits  

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Thionin 1 (X = S) is unknown only annulated systems have been reported which exhibit no aromatic character. 

The parent thionine system 1 up to now has not been prepared probably because the C-S bond in valence isomeric forms is too weak giving rise to facile rearrangement or decomposition. The obvious synthetic route, photochemical transformation of cyclooctatetraenccpisulfide 2 (9-thiabicyclo[6.1.0]nona-2,4,6-triene), does not lead to 1, but intriguingly to another valence isomer, the sulfur-bridged homotropylidene system 3.20... 

The dibenzannulated system dibenzo[ /]thionin (6) is prepared by a twofold Wittig reaction... 

The classical example of snch a device is a cell where thionine dye is used. Thionine is the oxidizing agent in the reaction T -r e + f TH. Thionine itself is hard to reduce electrochemically. Therefore, the mediating redox system Fe /Fe is used, which functions as an electron shnttle. The excited form of thionine, T, produced under illumination is readily rednced by divalent iron ions ... 

The thionine reduction prodnct TH is anodically reoxidized to thionine, while the Fe ions are cathodically rerednced to Fe ions. Thns, the chemical composition of the system will not change dnring cnrrent flow. The potential difference between the electrodes that can be used to extract electrical energy is 0.2 to 0.4 V under current flow. The conversion factor of Inminous to electrical energy is very low in such cells, about 0.1%. This is due to the numerous side reactions, which drastically lower the overall efficiency. Moreover, the stability of such systems is not high. Therefore, the chances for a practical use are not evident so far. 

Some properties of three typical photoredox-active dyes are summarized in Table 5.6. The most important photogalvanic system is based on the photoredox reaction of thionine with Fe2+. It was first studied by E. Rabinowitch in 1940 and recently optimized by J. W. Albery et ah The structural formula of thionine, Thi+ and its reduction products (Sem+, Leu2+) are as follows ... 

The photoexcited thionone, Thi+ is reduced by Fe2+ to the unstable semithionine (Sem+) which further disproportionates to Thi+ and the doubly reduced form of thionine, leucothionine (Leu2+) ... 

A regenerative photogalvanic cell with oxidative quenching (Fig. 5.58b) is based, for example, on the Fe3+-Ru(bpy)2+ system. In contrast to the iron-thionine cell, the homogeneous photoredox process takes place near the (optically transparent) cathode. The photoexcited Ru(bpy)2+ ion reduces Fe3+ and the formed Ru(bpy)3+ and Fe2+ are converted at the opposite electrodes to the initial state. 

Thionine [Lauth s violet] 0.563J 0.064 1-13 Colorless to violet... 

EXAFS data published in 1995 indicate the same contraction in metal-metal distances as the P-cluster is reduced.25 In the thionine-oxidized P2+ form, short Fe-Fe distances are found at 2.74 A in the resting P form, short Fe-Fe distances are around 2.67 A. Long Fe-Fe distances (cross cluster) of approximately 3.75 A... 

Stratakis, M. and Rabalakos, C. (2001). Chemoselective hydroperoxidation of alkenylarenes within thionin-supported zeolite Na-Y. Tetrahedron Lett. 42, 4545-4547... 

Stratakis, M., Nencka, R., Rabalakos, C., Adam, W. and Krebs, O. (2002). Thionin-sensitized intrazeolite photooxygenation of trisubstituted alkenes substituent effects on the regioselectivity as probed through isotopic labeling. J. Org. Chem. 67, 8758-8763... 

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