Merocyanine dye

The merocyanines are also a valuable class of photographic sensitizers. Because of their nonionic structure they are more soluble in nonpolar solvents than the ionic cyanines. Merocyanines 21-23 can also sensitize from the blue to the near-infrared. They are most useful as blue and green sensitizing dyes. 

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If an ideal solution is formed, then the actual molecular A is just Aav (and Aex = 0). The same result obtains if the components are completely immiscible as illustrated in Fig. IV-21 for a mixture of arachidic acid and a merocyanine dye [116]. These systems are usually distinguished through the mosaic structure seen in microscopic evaluation. 

Fig. IV-21. Surface pressure versus area for monolayers of immiscible components a monolayer of pure cadmium arachidate (curve 1) and monolayers of mixed merocyanine dye, MC2, and cadmium arachidate of molar ratio r = 1 10 (curve 2) 1 5 (curve 3), 1 2 (curve 4), and pure MC2 (curve 5). The subphase is 2.5 x 0 M CdC, pH = 5.5 at 20°C. Curve 3a (O) was calculated from curves 1 and 5 using Eq. IV-44. (From Ref. [116].)...

Carbocyanine or merocyanine dyes prepared from selenazole or selenazoline rings have a particular interest in photography. 

Nitro-substituted indolino spiroben2opyrans or indolino spironaphthopyrans are photochromic when dissolved in organic solvents or polymer matrices (27). Absorption of uv radiation results in the colorless spiro compound [1498-88-0], C22H2gN202, being transformed into the colored, ring-opened species. This colored species is often called a photomerocyanine because of its stmctural similarity to the merocyanine dyes (see Cyanine dyes). Removal of the ultraviolet light source results in thermal reversion to the spiro compound. 

Fig. 3. Spectral sensitizing dyes for silver haUdes. (a) Blue sensitizers (400—500 nm) are designated BN (b) green sensitizers (500—600 nm) are designated GN (the ring oxygen may be replaced by N(R)) (c) red sensitizers (600—700 nm) are designated RN (d) MN designates a merocyanine dye and (e),...

Photopolymerization reactions are widely used for printing and photoresist appHcations (55). Spectral sensitization of cationic polymerization has utilized electron transfer from heteroaromatics, ketones, or dyes to initiators like iodonium or sulfonium salts (60). However, sensitized free-radical polymerization has been the main technology of choice (55). Spectral sensitizers over the wavelength region 300—700 nm are effective. AcryUc monomer polymerization, for example, is sensitized by xanthene, thiazine, acridine, cyanine, and merocyanine dyes. The required free-radical formation via these dyes may be achieved by hydrogen atom-transfer, electron-transfer, or exciplex formation with other initiator components of the photopolymer system. 

A merocyanine dye, l-ethyl-4-(2-(4-hydroxyphenyl)ethenyl)pyridinium bromide (M-Mc, 2), exhibits a large spectral change according to the acid-base equilibrium [40, 41]. The equilibrium is affected by the local electrostatic potential and the polarity of the microenvironment around the dye. Hence, this dye is useful as a sensitive optical probe for the interfacial potential and polarity when it is covalently attached to the polyelectrolyte backbone. 

Morishima et al. [42] prepared polyanions (A-x, 3) of various charge densities tagged with the merocyanine dye (Me) by terpolymerization of acrylic acid (AA), acrylamide (AAm), and a small mole fraction of l-(2-methacryloyloxyethyl)-4-(2-(4-hydroxyphenyl)ethenyl)pyridinium bromide (MA-Mc). Since these polyanions carry only 1 mol% of the MA-Mc units, they can practically be treated as copolymers of AA and AAm with a wide range of composition. 

The merocyanine dye mentioned above shows solvatochromism, which means that the absorption band maximum of the quinoid form (D form) is sensitive to solvent polarity [40,41]. In Fig. 3, the absorption maximum of the solvatochromic band for M-Mc (a low molecular weight merocyanine analog) is plotted against the dielectric constant of 1,4-dioxane/water mixtures [42]. With the relationship... 

Small fractions of a similar type of merocyanine dye moieties (Me) were also covalently tagged onto poly(sodium 2-acrylamido-2-methylpropanesulfonate) (AMc-3, 4) and poly[(3-(methacrylamino)propyl)trimethylammonium chloride] (QMc-1, 5) [49], The observed pKobs value of 10.92 for AMc-3 was higher than that for the neutral reference (NMc-3, 6) by 2.24 pH units. By contrast, the... 

Menchutkin reaction 53 Mercury porosimetry (MP) 149 Merocyanine dye 57, 58 Methacrylic acid 162... 

Kulinich AV, Derevyanko NA, Ishchenko AA, Bondarev SL, Knyukshto VN (2008) Structure and fluorescence properties of indole cyanine and merocyanine dyes with partially locked polymethine chain. J Photochem Photobiol A Chem 200 106—113... 

Fast-response probes (response times less than milliseconds) styrylpyridinium and annellated hemicyanine dyes, merocyanine dyes, and 3-hydroxychromone dyes... 

Meridional tridendate ligand, 7 578 Merino wool, 26 370-371, 373, 374, 380 amino acid composition of, 26 377t Merocyanine 540 (MC540), 9 517 Merocyanine chromophores, 20 506 Merocyanine dyes, 9 503, 504, 511—512 ... 

Merocyanine Dye Method for Acid Analysis. Resist photochemistry can often be monitored by the changes in ultraviolet absorption spectra associated with a bleaching of the sensitizer absorbance. In the case of resist systems with triphenylsulfonium salts, no change in the film absorption is observed on irradiation. In order to determine the amount of acid produced, a direct method for acid analysis was required. A highly sensitive method was desirable since the amount of acid produced is approximately 10 6 mmol for a 1 micrometer thick film on a 2 inch wafer. Furthermore a nonaqueous technique is preferred in order to avoid hydrolysis of the hexafiuoroantimonate salt. Hydrolysis gives hydrogen fluoride (14) which makes accurate acid determination more difficult. 

Gaines (15) has previously described the use of merocyanine dyes as a nonaqueous means of determining Bronstcd acid concentration. Merocyanine dyes are protonated by strong acids to produce protonated dye which has a distinct visible absorption (Figure 1). The unprotonated dye form (3) has a solvent dependent visible absorption maxima. The present studies were performed in acetonitrile or dichloromcthane solvent where absorption maxima were at 576 nm and 610 nm respectively. The absorbance of the protonated form (4) is relatively unaffected by choice of solvent and is clearly separable from the absorbance of the free dye. The extinction coefficient of the free dye is quite large (71,000 in dichloromethane) which allows determination of small amounts of acid such as 10 6 mmol with an average error of less than 10%. 

For comparison, the solution quantum yield was determined by the merocyanine dye technique. Acetonitrile solutions of triphenylsulfonium hexafluoroantimonate were irradiated with a 5 m. /cm2 dose. Dye solution was added and the acid content was determined by changes in dye absorption. The quantum yield for acid production was determined to be 0.8, which agrees reasonably well with the value (0.71) determined for the hexafluoroarsenate salt (8). 

Figure 2. Bleaching of merocyanine dye absorption on addition of fractional equivalents of trifluoroacetic acid.

The authors wish to acknowledge George Gaines of General Electric Corporate Reasearch and Development and Robert Tweig of the IBM Research Research Division for providing samples of the merocyanine dyes. 

Acid-catalyzed photoresist films acid diffusion, 35 acid generation, 303233/341 advantages, 28 catalytic chain length, 3435r development of classes of cationic photoinitiators, 28 experimental procedure, 35-36 generation mechanism from irradiation of triphenylsulfonium salts, 28-29 merocyanine dye method for acid analysis, 30,31/33/... 

Deposition of a merocyanine-dye layer on a transparent electro-conducting film of polyester coated with indium-tin oxide (ITO). Two layered structures were studied ... 

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