Neutral dyes

Fig. 8. Sensitizing dyes of the cyanine class. K. = N — alkyl or chalcogens (O, S, Se, Te) R = chloro, phenyl, or additional benzene ring R = methyl, ethyl, or hydrogen n = 0, 1, 2 and RPRIME, R " = alkyl or sulfoalkyl. Solubihty in methanol for a carbocyanine dye n = 1 X = S R = Cl R = ethyl. Cationic dye (R" = R " = ethyl anion = bromide) 9.5 mmol/T. neutral dye (R" = ethyl R " = sulfopropyl) 3.6 mmol/L anionic dye (R" = R = sulfopropyl ...

Dicarbocyanine and trie arbo cyanine laser dyes such as stmcture (1) (n = 2 and n = 3, X = oxygen) and stmcture (34) (n = 3) are photoexcited in ethanol solution to produce relatively long-Hved photoisomers (lO " -10 s), and the absorption spectra are shifted to longer wavelength by several tens of nanometers (41,42). In polar media like ethanol, the excited state relaxation times for trie arbo cyanine (34) (n = 3) are independent of the anion, but in less polar solvent (dichloroethane) significant dependence on the anion occurs (43). The carbocyanine from stmcture (34) (n = 1) exists as a tight ion pair with borate anions, represented RB(CgH5 )g, in benzene solution photoexcitation of this dye—anion pair yields a new, transient species, presumably due to intra-ion pair electron transfer from the borate to yield the neutral dye radical (ie, the reduced state of the dye) (44). 

To overcome hydrolysis of vinyl sulfone dyes during appHcation under neutral dyeing of wool, Hoechst introduced dyes with the /V-methyl taurine... 

For generation of acidic conditions, a non-volatile acid such as citric acid (12.7), or an acid donor such as ammonium tartrate (12.8) or ammonium sulphate, is preferred. An acid or acid donor is not used with 1 2 metal-complex dyes of high neutral-dyeing affinity,... 

The addition of an electron acceptor group into the D-ti-D can further enhance the 2PA cross sections. A series of dyes, cationic PD 2630, and two neutral dyes, SD 2243 and TD 2765, are shown in Fig. 18a. Compared with the polymethine dye PD 2630, SD 2243 has a squaraine fragment and a strong electron acceptor inserted into the main conjugation chain, while TD 2765 contains a tetraone fragment and an... 

Therefore, it is reasonable to assume that the metal complex dyes formed from dye anions such as (10) also exist in the azo form, irrespective of the tautomeric form of the neutral dye. As is evident later, this assumption is confirmed by X-ray diffraction studies on the metal complex dyes. 

This versatile water-soluble reactant has been evaluated in wool and nylon dyeing. The nucleophilic aminoalkyl derivatives of orthodox aminochlorotriazine dyes behave like traditional acid dyes on wool owing to their zwitterionic character under neutral-dyeing conditions (Scheme 7.65). Improved wet fastness can be achieved using the reactant XLC... 

In this chapter, we describe the design and important properties of supra-molecularly organized dye molecules in the channels of hexagonal nanocrystals. We focus on zeolite L as a host. The principles, however, hold for other materials as well. As an example, we mention ZSM-12 for which some preliminary results have been reported [55], We have developed different methods for preparing well-defined dye-zeolite materials, working for cationic dyes, neutral dyes, and combinations of them [3, 22, 25, 52], The formula and trivial names of some dyes that so far have been inserted in zeolite L are reported in Section II.C. The properties of natural and commercially available zeolites can be influenced dramatically by impurities formed by transition metals, chloride, aluminiumoxide, and others. This fact is not always sufficiently taken care of. In this chapter, we only report results on chemically pure zeolites, the synthesis of which is described in [53]. 

Cationic and neutral dyes have the tendency to adsorb at the inner and at the outer surface of the zeolite crystals. It is to be expected that the affinity of molecules to the coat and the base area differs. The coat and the base area of a good zeolite L material are nicely illustrated on the left and right side, respectively, of Figure 1.7. The number of molecules needed to form a monolayer nD on a cylinder of surface Az is... 

The general concept of the synthesis of sandwich materials is illustrated in Figure 1.15. In our first report on this [22], we first inserted a neutral dyel from the gas phase, filling the channels to the desired degree. It was possible to find conditions to insert a cationic dye2 from an aqueous suspension, despite the fact that neutral dyes are usually displaced by water molecules. This process can be well controlled so that a specific desired space is left for the third dye3 to be inserted. It is also possible to insert first a cationic dye and then a neutral one or to use other combinations. The principle can be extended to more than three different dyes. 

This chapter shows that zeolite L is a very suitable host for the arrangement of a wide variety of chromophores. The structure of zeolite L is such that the formation of non-fluorescent dimers inside the channels can be prohibited and chromophores can be aligned in a certain direction. We have shown that this host-guest system can be used to make very efficient nanoscale two-directional photonic antenna systems. A broad spectral absorption range can be achieved by using several different cationic and neutral dyes. 

Displacement equilibrium Neutral dye molecules D in the zeolite ZDrXp can be displaced by x molecules of X. The states of X(out) and D(out) have to be specified. 

A similar open-chain host binding hydrophobic anionic and neutral dyes in water Murakami Y, Hayashida O, Nagai Y, (1993) Tetrahedron Lett 34 7935 Schmidtchen FP (1986) J Org Chem 51 5161... 

A van Deemter plot for the separation of neutral dyes by micellar electrokinetic chromatography follows.61... 

Solid diazonium salt 1 (0.50 mmol) and jS-naphthol 2 (0.60 mmol) were separately ground in agate mortars and cautiously mixed. In the case of Id MgSC>4 2H20 (0.50 mmol) was added to the mixture. The mixtures rested for 24 h in test tubes and were then exposed to ultrasound for 24 h in a cleaning bath. The quantitatively obtained azo-dye salts 3-HX were neutralized and freed from excess 2 by washings with 0.5 n NaOH (20 mL) and water (20 mL). The yields of the neutral dyes with the hydrazono structure 3a-d were 100, 98, 99 and 99%. 

The three major dye types, i.e., neutral, anionic, and cationic, are subdivided by use the neutral dyes comprise disperse, vat, and solvent dyes the anionic dyes, acid, direct, and reactive dyes and the cationic dyes, dyes for polyacrylonitrile fibers and other fibers modified to contain acid groups. 

In principle the anionic dyes also include direct dyes, but, because of their characteristic structures, these are used to dye cellulose-containing materials and are applied to the fiber from a neutral dye bath (see Section 3.3). 

Dyes based on these compounds possess, in addition to good lightfastness, excellent wetfastness and are usually neutral-dyeing on wool. This, although of no importance for dyeing pure wool, plays an important role in dyeing blended spun yam and blended fabrics of wool and cotton or wool and viscose staple. The neutral-dyeing acid dye can be used in combination with direct dyes (union wool recipes). Examples are C.I. Acid Yellow 56, 24825 [6548-24-9] (17), and C.I. Acid Red 154, 24800 [6507-79-5] (18 R = CH3). 

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