Basic violet dyes

The first triaryknethane dyes were synthesized on a strictiy empirical basis in the late 1850s an example is fuchsine, which was prepared from the reaction of vinyl chloride with aniline. Thek stmctural relationship to triphenylmethane was estabHshed by Otto and Fmil Fischer (5) with the identification of pararosaniline [569-61-9] as 4,4, 4 -triaminotriphenyknethane and the stmctural elucidation of fuchsine. Several different stmctures have been assigned to the triaryknethane dyes (6—8), but none accounts precisely for the observed spectral characteristics. The triaryknethane dyes are therefore generally considered to be resonance hybrids. However, for convenience, usually only one hybrid is indicated, as shown for crystal violet [548-62-9] Cl Basic Violet 3 (1), for which = 589 nm. 

In the ketone method, the central carbon atom is derived from phosgene (qv). A diarylketone is prepared from phosgene and a tertiary arylamine and then condenses with another mole of a tertiary arylamine (same or different) in the presence of phosphoms oxychloride or zinc chloride. The dye is produced directly without an oxidation step. Thus, ethyl violet [2390-59-2] Cl Basic Violet 4 (15), is prepared from 4,4 -bis(diethylamino)benzophenone with diethylaruline in the presence of phosphoms oxychloride. This reaction is very useful for the preparation of unsymmetrical dyes. Condensation of 4,4 -bis(dimethylamino)benzophenone [90-94-8] (Michler s ketone) with AJ-phenjl-l-naphthylamine gives the Victoria Blue B [2580-56-5] Cl Basic Blue 26, which is used for coloring paper and producing ballpoint pen pastes and inks. 

In a variation of this method, isolation of the ben2hydrol derivative is not required. The methane base undergoes oxidative condensation in the presence of acid with the same or a different arylamine direcdy to the dye. New fuchsine [3248-91 -7] Cl Basic Violet 2 (16), is prepared by condensation of two moles of o-toluidine with formaldehyde in nitrobenzene in the presence of iron salts to give the corresponding substituted diphenylmethane base. This base is also not isolated, but undergoes an oxidative condensation with another mole of o-toluidine to produce the dye. 

The use of basic organic dyes for ion pair extraction-photometric determination has been described.87 After ammonia treatment, an orange-red color with CUS04 and H2O2 (Deniges) can be quantitated.88 A water insoluble violet complex (X max. 620 nm) with 2-picoline-Cu(II) has also been reported.89... 

Although treated as separate classes in the Colour Index, these structural types are closely related and the few diphenylmethane dyes such as auramine (1.28 Cl Basic Yellow 2) are now of little practical interest. Commercial usage of the triarylmethane dyes and pigments has also declined considerably in favour of the major chemical classes. They were formerly noteworthy contributors to the acid, basic, mordant and solvent ranges, primarily in the violet, blue and green sectors. Numerous structural examples are recorded in the Colour Index. The terminal groupings can be amine/quinonimine, as in auramine and crystal violet (1.29 Cl Basic Violet 3), hydroxy/quinone, or both. The aryl nuclei are not always benzenoid (section 6.5). 

The resins used to make fluorescent pigments are usually toluenesulphonamide-melamine-formaldehyde matrices. The dyes used for this purpose include Cl Disperse Yellow 11, Rhodamine 6G (Cl Basic Red 1) and Rhodamine B (Cl Basic Violet 10). More details of the fluorescent dyes used have been given in a review by Christie [31]. 

A few triphenylmethane dyes are still obtained by empirical methods first used in the early processes of dye manufacture. For example, in the production of magenta (Cl Basic Violet 14), a mixture of aniline, toluidines and nitrotoluenes is heated with zinc and iron(II)... 

Several examples of typical triarylmethane dyes have already been mentioned, in particular, pararosaniline (6.161), malachite green (6.162) its o-chloro derivative (6.169), crystal violet (6.164), rosaniline (6.165) and diphenylamine blue (6.173). Cl Basic Green 1 (6.168 R = C2H5), the ethyl analogue of malachite green, is prepared by the aldehyde route and is isolated as the sulphate. The ethyl analogue of crystal violet is Cl Basic Violet 4 (6.167 R = C2H5) and is obtained by the ketone route. 

Hemicyanine (styryl) dyes are readily obtained by heating Fischer s base with an appropriate aldehyde. Typical products include Cl Basic Red 14 (6.224) and Cl Basic Violet 16 (6.225). The latter dye has been classified by ETAD as toxic [73]. 

Behaviour towards Alkalis.—Add a few drops of sodium hydroxide solution to the aqueous solution of a basic triphenylmethane dye. For a short time the colour remains unchanged, but soon fades and at the same time a faintly coloured flocculent precipitate separates. In all cases this is the carbinol to which repeated reference has already been made when pure it is colourless. In the case of crystal violet the carbinol is [(CHg N.CgHJjCOH. 

Nonchelating dyes include basic triphenylmethane dyes (e.g., Brilliant Green, Malachite Green, Crystal Violet), xanthene dyes (e.g., Rhodamine B, Rhodamine 6G), azine dyes (e.g., Methylene Blue), and acid dyes (e.g., Eosin, Erythrosin). These are intensely colored and when paired with an oppositely charged analyte ion lead to high sensitivities. 

The most important xanthenes are the imino derivatives known as rhodamines, exemplified by rhodamine B (Cl Basic Violet 10) (3.23a), A. 543 nm and 552 nm and rhodamine 6G (Cl Basic Red 1) (3.23b), /L 530 and X 557 nm (Figure 3.11). These are intensively fluorescent dyes with quantum yields close to unity. Rhodamine 6G especially has found wide apphcation in dayhght fluorescent pigments (see section 3.5.2) and this ring structure has been much modified for use in many other outlets, especially as laser dyes (see section 3.5.3) and in biomedical applications (see section 3.5.6). 

Many cationic dyes for acrylic fibres, especially methines, such as Cl Basic Red 13, Cl Basic Violet 7 and Cl Basic Red 74 are very bright and fluorescent and hence this fibre has a place in fluorescent textiles. 

Basic fuchsin (rosaniline, basic violet 14) or Pyronin Y are suitable as tracking dye. 

Tile triarylmethane dyes are generally considered to be resonance hybrids. However, for convenience, usually only one hybrid is indicated, as shown for crystal violet, Cl Basic Violet 3 (1), for which Xmllx = 589 nm. 

The corresponding C.I. Basic Violet 16, 48013 6359-45-l, obtained from 4-dicthylaminobcnzaldehyde, dyes polyacrylonitrile a more intense bluish red... 

Sahoo, C., A.K. Gupta and A. Pal (2005). Photocatalytic degradation of crystal violet (Ci basic violet 3) on silver ion doped Ti02. Dyes and Pigments, 66(3), 189-196. 

Basic Blue 22, and C.l. Basic Red 18. The triaryl methane dye C.l. Basic Violet 3 has a mobile cation that produces resonance structures of comparable energy. 

Several dye coloration scales are used to characterize starch varieties. Perhaps the oldest is the differentiation between starches based on the uptake of Saphranin and Gentiana Violet (see Table XXXVIII).787 Co-vello788 presented another coloration scale which is based on the use of six common acidic and basic dyes (see Table XXXIX). Like the Saphranin and Gentiana Violet dyes, these dyes adsorb directly on starch. Table XL presents a list of synthetic dyes tested in starch dyeing.789-790 Zwikker791 observed the reactions of mechanically damaged starch granules and amylo-... 

Data on the toxicity of TCPM and TCPMe are very scarce. Michaels and Lewis [2] have reported a toxicity study on five azo and triphenylmethane dyes. In that study Basic Violet 3, with a structure in which the basic structure of TCPM can be recognized (Fig. 2), shows the highest toxicity a survival rate of 20.7 6.6% at a dye concentration of 5.0 mg/1 of microbiota in a plating medium incorporated with dye. 

Cellulosic fibres have, for all practical purposes, no affinity for basic dyes. A few such as Auramine (C.I. basic yellow 2), Magenta (C.I. basic VIOLET 14), and Methyl Violet (C.I. basic violet 1) have some affinity for cotton, but the wet-fastness leaves very much to be desired. In the case of the protein fibre there is substantial evidence that the affinity is of a chemical nature. The reaction is essentially one of salt formation as shown ... 

Sensitive extraction spectrophotometric methods for determining Sb have been based on the ion-pair formation between SbCl5 and the basic triphenylmethane dyes [37]. Brilliant Green (e=7.0-10 ) [3,37-46], Crystal Violet [25,37,47-49], Methyl Violet [12,37], Methyl... 

Numerous spectrophotometric methods are based on the formation of ion-associates of the anionic iodide complex (CdL or Cdls ) [52-55] and bromide (CdBr4 ) [56] complexes with basic dyes. In the old flotation-spectrophotometric method (e = 1.3-10 ) [52], Crystal Violet is used, DIPE as floating solvent and acetone for dissolution of the floated compound. Other dyes that have been used in association with the cadmium iodide complex include Rhodamine 6G [57], Malachite Green (extraction with benzene) [53,54], and a basic azo dye [55]. 

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