[Nicole E. Braml and Wolfgang Schnick (2012): "New Heptazine Based Materials with a Divalent Cation – Sr[H2C6N7O3]2·4H2O and Sr[HC6N7(NCN)3]·7H2O". ''Zeitschrift für anorganische und allgemeine Chemie'', volume 639, issue 2, pages ???
{{doi|10.1002/zaac.201200345}}
]
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[Hansjuergen Schroeder and Ehrenfried Kober (???): "Some Reactions of Cyameluric Chloride".
The Organics Division, Olin Mathieson Chemical Corporation, New Haven, Connecticut
Received May 23, (1962)
In contrast to the concept generally presented in the literature, cyameluric chloride was found to undergo nucleophilic
displacement reactions readily, and therefore was utilized as the starting material for the synthesis of various tri-s-triazine
derivatives. All three chlorine atoms can be easily replaced by means of sodium alkylates, phenols, or amines to give the
respective trialkylcyamelurates, triarylcyamelurates, and melem (triaminotri-s-triazine) derivatives. Difficulties were
encountered in the synthesis of unsymmetrical tri-s-triazines, since in most reactions cyameluric chloride trisubstitution predominated regardless of the ratio of the reactants. Only four unsymmetrical compounds could be obtained. A series of
triaryl tri-s-triazines was prepared by subjecting cyameluric chloride to a modified Friedel-Crafts reaction with benzene or
alkylbenzenes. While s-triazine derivatives show th
This invention relates to photographic silver halide emulsions containing dicarbocyanine dyes and in super sensitizing combination there with, hydromelonic acid, cyameluric acid, or an alkali metal salt thereof.
It is known in the art of making photographic emul
sions that certain dyes of the cyanine class alter the sensi tivity of photographic emulsions of the gelatino-silver halide kind, when the dyes are incorporated in the emul
sions. It is also known that the sensitization produced by a given dye varies somewhat with the type of emulsion in which the dye is incorporated. Furthermore, the
sensitization of a given emulsion by a given dye may be
altered by varying the conditions in the emulsion. For example, the sensitization may be increased by increasing the silver ion concentration or decreasing the hydrogen ion concentration (i. e., increasing the alkalinity) or both.
Thus, sensitization can be increased by bathing plates, coated with a spectrally sensitized emulsion, in water or in aqueous solutions of ammonia. Such a process of al tering the sensitivity of a sensitized emulsion by increasing the silver ion concentration and/or by decreasing the hydrogen ion concentration is commonly called "hyper sensitization'. Hypersensitized emulsions have generally poor keeping qualities. I have now found another means of altering the sensi tivity in emulsions containing dicarbocyanine dyes. Since
the conditions in the emulsion, i. e., the hydrogen ion
and/or the silver ion concentration undergo little or no
change in my method, I shall designate my method as a kind of supersensitization. It is, therefore, an object of my invention to provide photographic emulsions containing dicarbocyanine dyes and as supersensitizers therefor, certain derivatives of melon and cyameluric acid, particularly hydromelonic acid, cyameluric acid, or an alkali metal salt of these acids. Another object is to provide a means for prepar ing these supersensitized emulsions. Other objects will be
come apparent from a consideration of the following de scription and examples. While the derivatives of melon and cyameluric acid em ployed in my invention have been previously employed in photographic emulsions which have been optically sensi tized with “cyanine" and "merocyanine" dyes, the effects observed in the instant invention are not general. That
is, it has been found that no significant (or measureable) supersensitizing effect is observed with many simple cyanine and carbocyanine dyes. It was not expected, therefor, that the useful results illustrated below could be obtained with dicarbocyanine dyes. The dicarbocyanine dyes which are useful
]
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[Elisabeta Horvath-Bordon, Edwin Kroke, Ingrid Svoboda, Hartmut Fueß, Ralf Riedel, Sharma Neeraj and Anthony K. Cheetham (2004):
issue 22,
''Dalton Transactions'',
Alkalicyamelurates, M3[C6N7O3]·xH2O, M = Li, Na, K, Rb, Cs: UV-luminescent and thermally very stable ionic tri-s-triazine derivatives†
]