Zwitterionic dye

ZWITTERIONIC DYES BASED ON PYRIDINIUM OR STILBAZOLIUM RING... 

Certain materials, such as many phthalocyanines [45], can only be deposited during each upstroke (Z-type deposition) and others only during each insertion (X-type). The type of deposition followed by a particular material affects the properties of the resulting LB films due to symmetry restrictions for second-order physical effects such as piezoelectricity or optical second-harmonic generation. The bilayer unit (equivalent to the unit cell in a crystal) is symmetric for Y-type deposition but non centric for Z- and X-type modes, as indicated in Figure 12.12. Unfortunately, several researchers have found that Z- and X-mode multilayers are often temporally unstable, although the zwitterionic dyes of Ashwell prove to be one of the exceptions [46]. 

A sensor array, in which a single entity acts as both host and indicator for several metal ions, has been produced by Anslyn and coworkers [64]. The system, a chemodosimeter, is based on a squaraine derivative as a signalling unit. Squaraines (SQ) are a class of zwitterionic dyes, in which a central squaric acid ring is... 

The pFL-dependent partitioning of the ionizable, cationic dye thymol blue has also been investigated [6]. In its neutral, zwitterionic, and monoanionic forms, the dye preferentially partitions into the IL phase (from acidic solution), the partition coefficient to the IL increasing with increasing IL hydrophobicity. Under basic conditions, the dye is in the dianionic form and partitions into water (Figure 3.3-9). 

Photochemical synthesis of sulphoxides was reported for the first time by Foote and Peters111 in 1971. They found that dialkyl sulphides undergo smoothly dye-photosensitized oxidation to give sulphoxides (equation 32). This oxidation reaction has been postulated to proceed through an intermediate adduct 63, which could be a zwitterionic peroxide, a diradical or cyclic peroxide, which then reacts with a second molecule of sulphide to give the sulphoxide (equation 33). 

As mentioned in Table 8.1, amphoteric surfactants contain both an anionic and a cationic group. In acidic media they tend to behave as cationic agents and in alkaline media as anionic agents. Somewhere between these extremes lies what is known as the isoelectric point (not necessarily, or even commonly, at pH 7), at which the anionic and cationic properties are counterbalanced. At this point the molecule is said to be zwitterionic and its surfactant properties and solubility tend to be at their lowest. These products have acquired a degree of importance as auxiliaries in certain ways [20-25], particularly as levelling agents in the application of reactive dyes to wool. 

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... 

Aggregation of pseudoisocyanine (dye I, Fig. 3) and 5,5 -dichloro-3,3 -diethyl-9-phenylthiacarbocyanine chloride (dye II, Fig. 5) induced by the vesicles consisting of zwitterionic DMPC and anionic DCP (Fig. 6) lipids was studied in [28]. Both dyes were shown to form fluorescent J-aggregates upon addition of the vesicles formed of the mixture of DMPC and DCP with relative content equal to 1 1. At the same time, for both dyes pure DMPC vesicles did not induce the J-aggregation. Upon addition of the vesicles containing DMPC and DCP in the 4 1 ratio, as well as... 

Figure 1.12 Reichardt s betaine dye in its zwitterionic ground state (a) and first excited state (b). The ground state has a larger dipole moment (15 D) than the excited state (6 D). Measurement of the energy of the transition between these two states (n - n ) is the basis for the Ej scale of solvent polarity...

Figure 1.14 Increasing solvent polarity stabilizes the zwitterionic ground state Or) of Rei-chardt s dye relative to the first excited state (n ), leading to an increase in the transition energy...

The main classes of dyes nsed as potentiometric probes are cationic or zwitterionic styryl dyes, cationic carbocyanines and rhodamines, anionic oxonols and hybrid oxonols and merocyanines. The particular class of dye determines factors snch as accnmnlation in cells, response mechanism and toxicity. 

Rogers et al. [2] demonstrated the reversible pH-dependent liquid-liquid partitioning of the well-known indicator thymol blue between water and [C4CiIm][PFg]. Neutral (zwitterionic) form of the dye partitions mostly to the IL phase, while the charged forms prefer the water phase. To adjust pH, the authors used mineral acids and bases no significant difference in the... 

Recognition of amino acids has been attempted more frequently with receptors that are likewise zwitterionic in nature (compare 35). Some early studies include the transport of phenylalanine by a merocyanine dye through a liposomal bilayer [53]. Rebek s dicarboxylate-complexing cleft 9 (see Sect. 2) turned out to be a selective (though achiral) binder of trypthophane, phenylalanine, and tyrosine methyl ether [54]. A reasonable structure for a phenylalanine complex of 2 1 stoichiometry, as deduced from NMR studies, is schematically represented in formula 39 [55]. 

The indazolin-3-ones (55) yield magenta dyes formulated as zwitterionic structures (56) (69USP3486894). On the other hand, the related benzisoxazolones (57) give yellow azo dyes (58) with p-phenylenediamines (57BRP778089). 

IV, and V.(13) The absorption spectra of III and IV (Figure 5b) are similar to FBB and its analogues, however the spectrum of V is anomalous. The spectrum of V resembles that of the anion VI, and suggest that this dye has a zwitterionic ground state. No improvement in the figure of merit of these dyes can reasonably be correlated with their structure. 

Three synthetic approaches to donor-acceptor-substituted conjugated molecules with enhanced orientability in electric fields, potentially applicable to the preparation of electro-optic polymers via electric field poling, are summarized. The three approaches are parallel attachment of chromophores to a common framework, embedding the chromophore in a zwitterion, and head-to-tail oligomerization of chromophores. The oligomerization method as well as the use of dyes as curing agents are briefly discussed in relation to the stability of electric field-induced polar order in polymer matrices. 

Problems with the compatibility of the dyes can also arise in dyeing mixtures of PA and PAC fibers. Such blends are produced, e.g., for skiwear. The cationic dyes used for the PAC component do not dye normal PA fibers. Acid and metal-complex dyes leave PAC fibers practically white. Sulfo group containing 1 1 metal-complex dyes possess a zwitterionic character and therefore can be applied in low concentration in the same bath with cationic dyes, without the occurrence of precipitation. In this manner, one-bath dyeing can be carried out. The stability of... 

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