Oxazine dyes

Figure B2.1.5 Fluorescence upconversion traces obtained at two observation wavelengdis (fiill circles, 570 mn open circles, 650 mn) at room temperature with an oxazine dye, phenoxazone, in methanol solvent. Figure courtesy of Professor S Rosenthal (Vanderbilt University).

Sauer M, Drexhage K H, Lieberwirth U, Muller R, Nerd S and Zander C 1998 Dynamics of the electron transfer reaction between an oxazine dye and DNA oligonucleotides motored on the single-molecule level Chem. Phys. Lett. 284 153-63... 

There have been approximately 80 references to oxazine dyes in the past 15 years. Several are references to their use as laser dyes and titration indicators. Thirty of these references are to oxazine dyes for either acryUc fibers or leather (qv) (7) (see Fibers, acrylic). 

Oxazine dyes containing sulfonic acid groups and claimed to be suitable for dyeing leather in brown shades include [89477-76-9] (20) and [87617-03-6] 2X) (8). 

Cationic oxazine dyes suitable for dyeing acryUc fibers have been reported (7). 

Synthesis. Several synthetic methods have been reported for oxazine dyes. The following are representative ... 

It has often been necessary to isolate oxazine dyes as insoluble zinc salts. Addition of urea [57-13-6] CH4N2O, or thiourea [62-56-6] CH4N2S, to the reaction mixture is reported to give good yields without using zinc (12), eg, the salt (25) [33203-82-6] is formed. 

Fig. 2. Phthalocyaiiine (22), and metallized fomiazan (23, 24) and azine (25) blue reactive dyes. Reactive Blue 15 [12225-39-7] (Cl 74459) (22) Reactive Blues (23) [78709-74-7] (8) and (24) (9) Reactive Blue 204 [109125-56-6] (25). Otlieiblue oxazine dyes aie other fluorotriazines [97140-65-3] (10,11), and a...

Steinhurst, D. A. and Owrutsky, J. C. (2001) Second harmonic generation from oxazine dyes at the air/water interface. /. Phys. Chem., 105, 3062-3072. 

Table 2. Effect of Substituents on the Color of Oxazine Dyes...

The availability of oxazine leucos is dictated by the ease of synthesis of the oxazine dyes. 

Bindschedler s Green (6.204) can be made by condensing p-nitroso-N,N-dimethylaniline with N,N- dimethyl aniline. A similar condensation with 2-naphthol gives Meldola s Blue (6.209 Cl Basic Blue 6), the first oxazine dye, discovered in 1879. The symmetrical Cl Basic Blue 3 (6.210) is of more commercial significance. It is synthesised by nitrosation of N,N-diethybrn-anisidine followed by condensation with N,N-diethybm-aminophenol, and is used for dyeing acrylic fibres. This dye is now classified by ETAD as toxic [73]. 

In pyronines, replacement of the carbon atom of the central ring (opposite to the oxygen atom) by a nitrogen atom produces oxazine dyes, which are used as laser dyes emitting in the range 600-750 nm. 

There are many systems of different complexity ranging from diatomics to biomolecules (the sodium dimer, oxazine dye molecules, the reaction center of purple bacteria, the photoactive yellow protein, etc.) for which coherent oscillatory responses have been observed in the time and frequency gated (TFG) spontaneous emission (SE) spectra (see, e.g., [1] and references therein). In most cases, these oscillations are characterized by a single well-defined vibrational frequency, It is therefore logical to anticipate that a single optically active mode is responsible for these features, so that the description in terms of few-electronic-states-single-vibrational-mode system Hamiltonian may be appropriate. 

Azine dyes, which have the general formula 15, are ring-closed azadiphenyl-methane or indamine dyes. Examples arephenazine dyes, oxazine dyes, and thia-zine dyes. 

Cationic dyes form positively charged dye ions by dissociation, and the positive electric charge is delocalized over the entire molecule. They are usually di- and triarylmethine dyes such as C.I. Basic Green 4, 42000 [569-64-2] (31), which are also known as triarylmethane dyes or triaryl carbenium ions [15], oxazine dyes such as C.I. Basic Blue 3, 51005 [2787-91-9] (32), orthiazine dyes. 

Oxidation. A primary intermediate, i.e., a para-substituted aromatic compound such as a derivative of 1,4-diaminobenzene or of 4-aminophenol, is oxidized to a quinonediimine or quinonemonoimine, respectively. The imine then reacts with a secondary intermediate (coupler), which is a meta-substituted compound such as as a derivative of 1,3-diaminobenzene, 3-aminophenol, or resorcinol. Another oxidation step yields an indo, phenazine, or oxazine dye which is three times the size of the precursors. The mechanism of this coupling reaction is shown in Scheme 5.1. 

Figure 7 Photosensitized reduction of oxazine dye using humic acid as sensitizer. The transient absorption spectrum was recorded following 532-nm laser pulse excitation of humic acid containing the dye and 1102.

Liu, D. Kamat, P. V. Electrochemically active nanocrystalline Sn02 Aims. Surface modifications with thiazine and oxazine dye aggregates, J. Electrochem. Soc. 1995, 142, 835. 

Vinodgopal, K. Environmental photochemistry Electron transfer from excited humic acid to Ti02 colloids and semiconductor mediated reduction of oxazine dyes by humic acid, Res. Chem. Intermed. 1994, 20, 825. 

A number of oxazine dye salts, on dissolving in aqueus alkali, precipitated the free radical thus the dye Meldola s blue, which precipitates even in almost neutral solution, yields a very stable solid free radical which can be kept in air and can be used as standard like 2,2-diphenyl-1 -picrylhydrazyl. 

Mention should be made of oxazine dyes, used also as biological stains, which are oxidized phenoxazine derivatives containing suitable auxochromic groups. A detailed treatment of these dyes, however, is beyond the scope of this review. Most of the industrial phenoxazine dyes are derived from benzophenoxazines (e.g., Meldola s blue) or from more complex ring systems containing the phenoxazine residue (triphendioxazine dyes).3,118 The long-known dyestuffs orcein and litmus which are prepared by the action of ammonia on certain lichens, and may also occur accidentally in nature, are both based on the oxidized phenoxazine ring system as shown by Musso and co-workers.119... 

Orange II, 262, 378 Orange IV, 273 Orientation rules, 50 ff. anthraquinone series, 56 benzene series, 51 carbazole series, 60 naphthalene series, 53 Orienting power, 51 Orthanilic acid, 122 Oxazine dyes, 308 ff. Oxidation methods, 8... 

As already mentioned in Sect. 4.1, the fluorescence behavior of many dye systems can be rationalized using the TICT model. For example, the fluorescence efficiency of xanthene dyes and derivatives like rhodamine and oxazine dyes correlates with the donor strength of the amino groups as predicted from... 

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