Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
1999-12-27
2002-04-02
Higel, Floyd D. (Department: 1626)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C548S253000, C549S003000, C549S210000, C556S113000, C556S117000
Reexamination Certificate
active
06365746
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to new Au(I) complexes comprising an organomercapto ligand, and to the manufacture of such complexes.
BACKGROUND OF THE INVENTION
There has been considerable effort devoted to improving the sensitivity of silver halide emulsions to actinic radiation, thereby increasing the sensitivity of the photographic elements in which they are contained. In this regard, photographic chemists have attempted to vary the components of, or the processes for making, silver halide emulsions. One particularly preferred means by which to improve sensitivity has been to chemically sensitize photographic emulsions with one or more compounds containing labile atoms of gold, sulfur, selenium or the like. Examples of chemically sensitized photographic silver halide emulsion layers are described in, for example,
Research Disclosure,
Item No. 308119, December 1989, Section III, and the references listed therein. (
Research Disclosure
is published by Kenneth Mason Publications Ltd, Dudley Annex, 12a North Street, Emsworth, Hampshire PO 10 7DQ, England.)
Many gold sensitizers have been described. For example, U.S. Pat. No. 3,503,749 describes the use of water soluble Au(I) thiolate salts comprising one Au atom ligated to one sulfur containing ligand; U.S. Pat. No. 5,220,030 teaches the use of Au(I) compounds with bis mesoionic heterocycles; U.S. Pat. No. 5,252,455 and U.S. Pat. No. 5,391,727 disclose the use of Au(I), macrocyclic cationic sensitizers; U.S. Pat. No. 5,049,484 teaches the use of Au(I) sensitizers having a Au atom ligated to the nitrogen atom of heterocyclic rings. U.S. Pat. No. 5,620,841 discloses the use of gelatin dispersions of a Au(I) thiosulfonato sensitizer with two different ligands at least one of which is mesoionic; and U.S. Ser. No. 08/672,254 teaches the use of gelatin dispersions of Au(I) thiosulfonato sensitizers with two different ligands at least one of which is a thioether group. JP 8069075 discusses the use of organic gold sulfide compounds in the sensitization to give low fogging and high contrast silver halide photographic materials. However, all of the above compounds have one or more disadvantages such as lack of water solubility, difficulty of synthesis or poor stability.
One common chemical sensitizer used in the sensitization of silver halide emulsions is aurous sulfide which is made as a colloidal gelatin dispersion, the exact composition of which is not well characterized. This gold sulfide dispersion can give rise to lot-to-lot variability and undesirable and inconsistent sensitometric performnance. The source of this variability may come from side reactions in the preparation of this highly insoluble solid since these reactions produce species which may be photographically active. Further, because of the highly insoluble nature of gold sulfide, most of the sensitizer added is in fact unused during the sensitization. The remaining sensitizer left in the gel/silver halide matrix can affect sensitometry.
The bis Au(I) mesoionic heterocycls e.g. bis(1,4,5-trimethyl-1,2,4-triazolium-3-thiolate) gold (I) tetrafluoroborate, TTT, while being a very useful sensitizer, is somewhat lacking in solution stability. Further, for the mesoionic triazolium sensitizers, multiple steps and recrystallizations are required in the preparation of the starting material bis(tetramethylthiourea) Au(I) tetrafluoroborate. Synthesis of the gold ligand 1,4,5-trimethyl-1,2,4-triazolium-3-thiolate is difficult, and the preparation of the mesoionic triazolium sensitizer is limited to small batches. Finally, the limited solubility of the mesoionic triazolium sensitizers requires the use of a large volume of water for dissolution.
Thus, there is still need for Au (I) compounds that are stable, water soluble and well characterized. Further, they must be easily manufactured from readily available starting materials.
SUMMARY OF THE INVENTION
This invention provides organomercapto Au(I) complexes having the formula
[(M—SOL)
n
—A—S—Au—S—A—(SOL—M)
n
]M
wherein
M is a cationic counterion;
SOL is a solubilizing group;
A is a substituted or unsubstituted divalent organic linking group;
and n is 1 to 4; and wherein the compound is symmetrical. This invention further provides a simple method of manufacturing an organomercapto Au(I) complex comprising reacting an Au(I) complex with an organomercapto ligand and isolating the resulting organomercapto Au(I) complex from the reaction mixture.
The novel organomercapto Au(I) complexes of this invention have numerous advantages. Unlike prior mixed-ligand gold compounds, the two Au ligands in this new class of compounds are identical, thus reducing the complexity of preparation. Further, the present invention employs inexpensive and commercially available materials for the generation of the necessary Au(I) species. Another advantage is that the preparation of the gold complexes of the present invention does not utilize dangerous explosive gold fulminates or large quantities of organic solvents.
Additionally, because of the stability of the covalent gold and sulfur bonds, the complexes of the present invention are more stable than those having mesoionic ligands. Indeed, there is evidence that even in acidic solutions, the complexes of the present invention are more stable than those of the mesoionic sensitizers.
The gold complexes of the present invention are also highly water soluble. Because of the water solubility of these complexes, the use of costly and time consuming preparation of gel dispersions is unnecessary. Further, there is no need to use large volumes of water for dissolving the complexes.
DETAILED DESCRIPTION OF THE INVENTION
The organomercapto Au(I) complexes of the invention are represented by the formula
[(M—SOL)
n
—A—S—Au—S—A—(SOL—M)
n
]M
with the complex being symmetrical. M is a cationic counterion. Preferably M is an alkali metal, for example potassium, sodium or cesium, or an ammonium cation, for example, a tetrabutyl or tetraethyl ammonium group. SOL is a water solubilizing group, suitable examples of which are sulfato, sulfonato, sulfinato, phosphato, and carboxy groups. n is an integer from 1 to 4, and more preferably n is 1 or 2.
A is a substituted or unsubstituted divalent organic radical. Preferably A is an aliphatic, (cyclic or acyclic), aromatic or heterocyclic divalent group. When A is an aliphatic group, preferably it is a substituted or unsubstituted alphatic group having 1 to 20 carbon atoms, and more preferably having 1 to 8 carbon atoms. Examples of appropriate groups include alkylene groups such as ethylene, methylene, propylene, butylene, pentylene, hexylene, octylene, 2-ethylhexylene, decylene, dodecylene, hexadecylene, octadecylene, cyclohexylene, isopropylene and t-butylene groups.
The preferred aromatic groups have from 6 to 20 carbon atoms. More preferably, the aromatic groups have 6 to 10 carbon atoms and include, among others, phenylene and naphthylene groups. These groups may have substituent groups. The heterocyclic groups are preferably substituted or unsubstituted divalent 3 to 15-membered rings with at least one atom selected from nitrogen, oxygen, sulfur, selenium and tellurium in the ring nucleus. More preferably, the heterocyclic groups are 5 to 6-membered rings with at least one atom, and preferably more than one atom, selected from nitrogen. Examples of heterocyclic groups include the divalent radicals of pyrrolidine, piperidine, pyridine, tetrahydrofuran, thiophene, oxazole, thiazole, imidazole, benzothiazole, benzoxazole, benzimidazole, selenazole, benzoselenazole, tellurazole, triazole, benzotriazole, tetrazole, oxadiazole, or thiadiazole rings. The preferred heterocyclic group is tetrazole.
Unless otherwise specifically stated, substituent groups which may be substituted on molecules herein include any groups, whether substituted or unsubstituted, which do not destroy properties necessary for photographic utility. When the term “group” is applied to the identification of a substituent containing a substitutable hydrogen, it is intended to enc
Cleary Brian P.
Lok Roger
White Weimar W.
Eastman Kodak Company
Higel Floyd D.
Meeks Roberts Sarah
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