Photographic element with new singlet oxygen quenchers

Photographic elements are disclosed comprising a silver halide emulsion layer having associated therewith a magenta coupler and a magenta dye stabilizer compound of the formula S-I: ##STR1## wherein R.sup.0 represents an aryl group or a heterocyclic group; L.sub.1 and L.sub.2 are independently linear alkylene or cycloalkylene linking groups; and R.sup.a and R.sup.b are independently selected substituent groups at least one of which has a .sigma.* value of at least 1.8. Compounds in accordance with formula S-I act as singlet oxygen quenchers and are effective stabilizers for magenta dye images. Photographic elements of the present invention upon exposure and photographic processing yield magenta dye images that have low fading when exposed to light.

FIELD OF THE INVENTION 
This invention relates to photographic elements containing a layer having 
associated therewith magenta dye forming couplers and compounds which 
reduce fading of the dyes formed from the couplers on processing of the 
photographic element. 
BACKGROUND OF THE INVENTION 
In a silver halide photographic element, a color image is formed when the 
element is exposed to light and then subjected to color development with a 
primary aromatic amine developer. Color development results in imagewise 
reduction of silver halide and production of oxidized developer. Oxidized 
developer reacts with one or more incorporated dye-forming couplers to 
form an imagewise distribution of dye. 
The dyes that are formed by any color coupler during processing have a 
tendency to fade over time as a result of exposure to light, heat, 
humidity and oxygen. As all three image dyes of a typical color element 
fade, this results in overall fading of the image over time. In addition, 
since the three image dyes may not fade at the same rate, an apparent 
change in image color may result. Such change is particularly noticeable 
in the case of magenta image dye fading. 
A significant disadvantage of many magenta dye-forming couplers is fading 
of the dyes formed from them by photographic processing due to extended 
exposure to low levels of light. Compounds which are included in 
photographic elements to reduce image dye fading are known as stabilizers. 
Inclusion of stabilizers in color photographic materials can reduce the 
deterioration of the dye images which occurs over time as a result of the 
action of light, heat, humidity and/or oxygen. This is especially true for 
dyes formed from pyrazoloazole couplers. U.S. Pat. Nos. 5,236,819, 
5,082,766 and 5,017,465 and German Published Patent Application DTOS 
4,307,194, e.g., describe the use of certain stabilizers with 
pyrazoloazole couplers to improve their dye stability. One class of 
stabilizers which is disclosed includes compounds of the following 
structure: 
##STR2## 
wherein A represents a group of non-metal atoms necessary to complete a 
5-membered to 8-membered nitrogen-containing ring and R.sup.0 represents 
an aryl group or a heterocyclic group. Preferred compounds of such formula 
as described in U.S. Pat. No. 5,017,465 include compounds wherein A 
represents the atoms necessary to complete a thiomorpholine 1,1-dioxide 
group and where R.sup.0 represents an alkoxy substituted phenyl group. 
Such compounds are believed to stabilize by acting as singlet oxygen 
quenchers. 
It would be desirable to improve the light stability of dyes derived from 
magenta dye forming couplers, and thus retain the color rendition of the 
image for a longer period of time. It would also be desirable to provide 
singlet oxygen quenching stabilizers with greater structural flexibility 
than the prior art stabilizers comprising nitrogen-containing ring 
structures, so that other properties of such compounds may be more easily 
adjusted where desired (e.g., compound solubility and dispersibility). 
SUMMARY OF THE INVENTION 
In accordance with one embodiment of the invention, a photographic element 
is disclosed comprising a silver halide emulsion layer having associated 
therewith a magenta coupler and a magenta dye stabilizer compound of the 
formula S-I: 
##STR3## 
wherein R.sup.0 represents an aryl group or a heterocyclic group; 
L.sub.1 and L.sub.2 are independently linear alkylene or cycloalkylene 
linking groups; and 
R.sup.a and R.sup.b are independently selected substituent groups at least 
one of which has a .sigma.* value of at least 1.8. 
In accordance with preferred embodiments, R.sup.0 represents a substituted 
phenyl group of the following formula: 
##STR4## 
wherein m is 1, 2, 3 or 4; 
n is 0, 1, 2, 3, or 4, provided that the sum of m and n is less than or 
equal to 5; 
A is --NR.sub.1 '--, --S--, or --O--; and 
R.sub.1 and R.sub.1 ' are independently H or a substituent group and 
R.sub.2 is a substituent group, provided that substituent groups 
represented by R.sub.1 and R.sub.2 or two R.sub.1 or R.sub.2 groups may be 
joined to form a ring. 
In accordance with most preferred embodiments, R.sup.0 represents a 
para-substituted phenyl group of the formula: 
##STR5## 
where n is 0 or 1. 
Compounds in accordance with formula S-I act as singlet oxygen quenchers 
and are effective stabilizers for magenta dye images. Photographic 
elements of the present invention upon exposure and photographic 
processing yield magenta dye images that have low fading when exposed to 
light.

DETAILED DESCRIPTION OF THE INVENTION 
As used herein, unless otherwise indicated the alkyl and aryl groups, and 
the alkyl and aryl portions of groups, can be unsubstituted or substituted 
with non-interfering substituents. Typical alkyl groups have 1 to 32 
carbon atoms and typical aryl groups have 6 to 32 carbon atoms. Depending 
upon the position of the group, preferred alkyl groups can have 1 to 20 
carbon atom, 1 to 12 carbon atoms or 1 to 4 carbon atoms and preferred 
aryl groups can have 6 to 20 or 6 to 10 carbon atoms. Other groups 
identified below which contain a replaceable hydrogen atom can be 
substituted or not, depending on the particular structure and properties 
desired. 
R.sup.0 represents an aryl or heterocyclic group. Representative groups 
include phenyl, 1-naphthyl, 2-furyl and 2-thienyl, and pyridyl. In a 
preferred embodiment, R.sup.0 represents a substituted phenyl group 
represented by the formula: 
##STR6## 
wherein m is 1, 2, 3 or 4; n is 0, 1, 2, 3, or 4, provided that the sum of 
m and n is less than or equal to 5; A is --NR.sub.1 '--, --S--, or --O--; 
and R.sub.1 and R.sub.1 ' are independently H or a substituent group and 
R.sub.2 is a substituent group, provided that substituent groups 
represented by R.sub.1 and R.sub.2 or two R.sub.1 or R.sub.2 groups may be 
joined to form a ring. 
R.sub.1 preferably represents an alkyl group, a cycloalkyl group, an 
alkenyl phenyl group, an aryl group, a heterocyclic group, a bridged 
hydrocarbon group, an alkyl sulfonyl group or an aryl sulfonyl group. For 
R.sub.1, the alkyl group may include, e.g., a straight-chain or 
branched-chain alkyl group having 1 to 24 carbon atoms; the cycloalkyl 
group, e.g., a cycloalkyl group having 5 to 24 carbon atoms; the alkenyl 
group, e.g., an alkenyl group having 3 to 24 carbon atoms; the aryl group, 
e.g., a phenyl group and naphthyl group; the heterocyclic group, e.g., a 
pyridyl group, an imidazolyl group and a thiazole group; the acyl group, 
e.g., an acetyl group and a benzoyl group; the bridged hydrocarbon group, 
e.g., a bicyclo[2.2.1]heptyl group, etc., respectively. R.sub.2 may 
represent, e.g., a halogen atom or the groups such as alkyl, aryl, alkoxy, 
aryloxy, alkythio, arylthio, acyl, alkoxycarbonyl, carbamoyl (e.g., 
alkylcarbamoyl, arylcarbamoyl) ureido (e.g., alkylureido, arylureido), 
sulfamoyl (e.g., alkylsufamoyl, arylsulfamoyl), amino, alkylsulfonyl, 
arylsulfonyl, nitro, cyano and carboxy. 
The --AR.sub.1 substituent in the above formula is preferably located para 
to the amino substituent, and the --R.sub.2 substituent (when present) is 
preferably located ortho to the --AR.sub.1 substituent. In accordance with 
particularly preferred embodiments, R.sup.0 thus is represented by the 
formula: 
##STR7## 
wherein n represents 0 or 1. 
L.sub.1 and L.sub.2 are independently linear alkylene or cycloalkylene 
linking groups. L.sub.1 and L.sub.2 preferably are selected from alkylene 
groups having the formula --(C(R)(R)).sub.p --, where p equals from 1 to 
6, more preferably from 1 to 3, and most preferably 2, and each R may be 
independently H or an alkyl group, or two alkyl groups may be joined to 
form a cycloalkylene ring. Examples of cycloalkylene ring linking groups 
include the following: 
##STR8## 
Most preferably, each of L.sub.1 and L.sub.2 represents an unsubstituted 
ethylene linking group. 
R.sup.a and R.sup.b are independently selected substituent groups at least 
one of which, and more preferably each of which, has a .sigma.* value of 
at least 1.8. Preferably, at least one of R.sup.a and R.sup.b has a 
.sigma.* value of at least 2.5, and more preferably each of R.sup.a and 
R.sup.b has a .sigma.* value of at least 2.5. The Taft .sigma.* constant 
is described in pK.sub.a Prediction for Organic Acids and Bases, D. 
Perrin, B. Dempsey, and E. Serjeant, Chapman and Hall, New York, 
N.Y.(1981). It represents the electronic effect of a substituent in an 
aliphatic system. Values for various substituents may be found in Appendix 
Table A-1 of the above publication. Additional values may be found in 
"Exploring QSAR--Hydrophobic, Electronic, and Steric Constants," C. 
Hansch, A. Leo, and D. Hoekman, ACS Professional Reference Book, ACS, 
Washington, D.C., 1995. Hydrogen has a .sigma.* value of +0.49 and methyl 
has a value of 0.0. While a .sigma.* value of at least 1.8, and more 
preferably at least 2.5 is preferred for each of R.sup.a and R.sup.b in 
order to provide effective singlet oxygen quenching and good stabilizer 
compound stability towards singlet oxygen (.sup.1 O.sub.2) when used in 
accordance with the invention, combined .sigma.* values for R.sup.a and 
R.sup.b above 7.2 may result in lower than desired compound stability and 
singlet oxygen quench rates. Preferred combined .sigma.* values for 
R.sup.a and R.sup.b for compounds used in accordance with the invention 
are accordingly from 3.6 to 7.2, and more preferably 4.5 to 6.0, in order 
to provide effective singlet oxygen quenching and good stabilizer compound 
stability towards singlet oxygen. 
The .sigma.* constant value of a substituent may be determined by reference 
to the tables of the above publications. Table A.2 in the above pK.sub.a 
Prediction for Organic Acids and Bases reference contains a compilation of 
published Taft equations, in which various parent compounds (acids or 
bases) are utilized. As an alternative, one may determine the value 
experimentally from the formula: 
EQU .sigma.*=(pK.sup.O -pK)/.rho.* 
where .rho.* is the reaction constant which is the slope of the straight 
line plot of pK.sup.O -pK versus .sigma.* for known substituents of the 
base compound where pK.sup.O is the ionization constant of the base 
compound at 25.degree. C., and pK is the ionization constant of the 
substituted compound at 25.degree. C., which may be determined 
experimentally in accordance with conventional techniques. .rho.* may be 
determined from the slope of the linear plot of (pK.sup.O -pK) vs. 
.sigma.* values experimentally determined or from Table A.2 of the above 
publication. Reference may also be made to Mechanism and Theory in Organic 
Chemistry, 3rd Ed, T. H. Lowry and K. S. Richardson, Harper and Row, New 
York, (1987). 
Desirably, at least one of R.sup.a and R.sup.b is an electron withdrawing 
group selected from sulfamoyl, sulfonyl, sulfinyl, phosphonyl, phosphinyl, 
perfluorinated alkyl, and perfluorinated thio groups. More preferably at 
least one of and most preferably each of R.sup.a and R.sup.b is of the 
formula: 
##STR9## 
wherein R'and R" are independently selected from the group consisting of 
H, alkyl and aryl groups or together form a cyclic ring. The .sigma.* 
value of various preferred substituents are listed below, as reported in 
the "Exploring QSAR--Hydrophobic, Electronic, and Steric Constants" 
reference cited above: 
______________________________________ 
Substituent .sigma.* 
______________________________________ 
--CF.sub.3 2.61 
--CF.sub.2 CF.sub.2 CF.sub.2 CF.sub.3 2.44 
--CN 3.64 
--OCHF.sub.2 2.81 
--PO(OEt).sub.2 3.02 
--PO(Bu).sub.2 2.81 
--SO.sub.2 NMe.sub.2 2.65 
--SO.sub.2 NH.sub.2 2.61 
--SCF.sub.3 2.75 
--SCN 3.43 
--SOPh 3.08 
--SOMe 2.88 
--SO.sub.2 Ph 3.25 
--SO2Me 3.68 
--N(Me)SO.sub.2 CF.sub.3 3.0 
--NHSO.sub.2 CF.sub.3 3.1 
--NCS 2.65 
--N(SO.sub.2 Me).sub.2 2.80 
--N(CH.sub.2 CH.sub.2 OH).sub.2 2.43 
- 
#STR10## 
- X 
p-Me 3.02 
p-Br(Cl) 3.14 
p-t-Bu 2.97 
- 
#STR11## 
- X 
p-Br 3.35 
p-Cl 3.49 
p-F 3.4 
p-Me 3.32 
p-t-Bu 3.23 
p-OMe 3.23 
- 
#STR12## 
- X 
p-CN 2.73 
o-CN 2.67 
m-CN 2.59 
p-Br 2.44 
o-Br 2.48 
m-Br 2.48 
p-Cl 2.69 
o-Cl 2.62 
p-F 2.44 
m-F 2.51 
p-SO.sub.2 Me 2.85 
______________________________________ 
Specific stabilizer compounds of formula S-I which may be used within the 
scope of the present invention include the following structures: 
##STR13## 
Compounds of formula S-I in accordance with the invention may be prepared 
using generally known synthetic techniques. It is a particular advantage 
of the invention that the independently disubstituted dialkylene amino 
substituents allow for more structural flexibility in comparison to the 
prior art thiomorpholine-1,1-dioxide type compounds. Preferred compounds 
in accordance with the invention comprising N,N-bis-ethane sulfonamides, 
e.g., may be prepared in accordance with the following synthetic scheme: 
##STR14## 
The Michael addition of alkoxyanilines (I) to vinyl sulfonyl fluoride 
affords the N,N-bis-ethane sulfonylfluorides (II) in good yield (J. J. 
Krutak, R. D. Burpitt, W. H. Moore and J. A. Hyatt, J. Org. Chem., 44 
(22), 3847 (1979)). Addition of amines to (II) can generate either the 
N-mono-ethane sulfonamides (III) or the symmetrical N,N-bis-ethane 
sulfonamides (IV) depending on the reaction conditions. Subsequent 
addition of a second amine to (III) affords the unsymmetrical 
N,N-bis-ethane sulfonamide (V). 
Synthesis Example 1 
##STR15## 
4-(2-Ethylhexaoxy)aniline (16.8 g, 75.9 mmol) was dissolved in acetic acid 
(40 ml) and vinylsulfonylfluoride (18.4 g, 167 mmol) was added dropwise. 
After approximately 2 hrs., the reaction mixture set-up to a solid mass. 
Additional acetic acid (15 ml) was added to aid stirring. After 1 hr. the 
solid was isolated by filtration and washed thoroughly with hexanes. Air 
drying afforded 25.8 g (77% yield) of the desired product, IIa, as a pale 
pink, crystalline solid, mp. 80-81.degree. C. 
Mass Spec.: FDMS(CDCl.sub.3)-m/e=441M. 
NMR (CDCl.sub.3): .delta. 6.9 (s, 4); 3.8 (m, 6); 3.4-3.6 (m, 4); 1.2-1.8 
(m, 9); 0.8-1.0 (t, 6). 
Compound S-I-2 (IVa) 
##STR16## 
The above bis-ethanesulfonylfluoride (6.75 g, 15.3 mmol) and piperidine 
(6.51 g, 76.5 mmol) were combined in THF (100 ml) and heated at 45.degree. 
C. for 18 hrs. The reaction was cooled, poured into ice water (500 ml) and 
acidified to pH=5-6 with acetic acid. After stirring for 2 hrs., the solid 
was isolated by filtration and washed with water. Air drying and 
recrystallization from isopropyl alcohol afforded 7.31 g (83% yield) of 
the desired product, IVa, as a white crystalline solid, mp 105-106.degree. 
C. 
Mass Spec.: FDMS(CDCl.sub.3)-m/e=571M. 
NMR (CDCl.sub.3): .delta. 6.9 (d, 2); 6.75 (d, 2); 3.6-3.8 (m, 14); 3.2 (d, 
8); 3.0-3.1 (t, 4); 1.2-1.8 (m, 9); 0.8 (t, 6). 
Compound IIIb 
##STR17## 
The bis-ethanesulfonylfluoride, IIa (1.94 g, 4.4 mmol) was dissolved in a 
minimal amount of THF and added dropwise to a solution of morpholine (2.5 
g, 28.7 mmol) in THF (40 ml). After stirring overnight, an additional 0.5 
ml of morpholine was added followed by a second portion of 1 ml after 7 
hrs. After an additional 18 hrs., the reaction was poured into ice water 
and acidified to pH=5 with acetic acid. The mixture was extracted with 
CH.sub.2 Cl.sub.2 (2.times.'s) and the combined organic extracts were 
washed with brine (2.times.'s), dried (Na.sub.2 SO.sub.4) and freed of 
solvent under vacuum to afford 1.64 g of crude oil. This oil was combined 
with a previous run (2.4 g) and chromatographed on silica gel (2:98, 
acetone:CH.sub.2 Cl.sub.2) to afford the mono-sulfonamide product, IIIb, 
as a tan colored oil, 0.93 g. 
NMR (CDCl.sub.3): .delta. 6.8 (d, 2); 6.85 (d, 2); 3.65-3.80 (m, 10); 3.55 
(m, 2); 3.2 (t, 4); 3.05-3.1 (t, 2); 1.2-1.8 (m, 9); 0.8-0.95 (m, 6). 
Compound S-I-4 (Vb) 
##STR18## 
The above mono-sulfonamide, IIIb (0.93 g. 1.8 mmol) and .sub.n -octylamine 
(0.7 g, 5.4 mmol) were dissolved in THF (10 ml) and heated to 40.degree. 
C. for 24 hrs. A small amount of octylamine was added and the mixture 
heated an additional 24 hrs. The reaction was cooled and poured into ice 
water. Acidification with acetic acid to pH=5 afforded a tacky solid that 
was isolated by filtration, washed with water and dissolved in 
dichloromethane. The organic solution was washed with brine (2.times.'s), 
dried (Na.sub.2 SO.sub.4) and freed of solvent under vacuum. The crude oil 
(0.87 g) was chromatographed on silica gel (5:95, MeOH:CHCl.sub.3) to 
afford 0.57 g of the desired product as white crystals; after 
recrystallization from isopropyl alcohol, mp=73-74.5.degree. C. 
Mass Spec: FDMS(CDCl3)-m/e=617M. 
NMR (CDCl.sub.3): .delta. 6.8-6.95 (m, 4); 5.1 (t, 1); 3.5-3.8 (m, 10); 
3.1-3.3 (m, 8); 2.65-2.8 (m, 2); 1.05-1.8 (m, 21); 0.8-1.0 (t, 9). 
The magenta dye forming coupler used in the elements in accordance with the 
invention is preferably a pyrazolone, pyrazolotriazole, or 
pyrazolobenzimidazole with or without a suitable leaving group. The 
magenta coupler can be monomeric, dimeric, trimeric, oligomeric or 
polymeric coupler wherein the coupler moiety can be attached to the 
polymeric backbone via a substituent on the coupler moiety or a 
substituent on a coupling off group. Illustrative magenta couplers are 
disclosed in, for example, U.S. Pat. Nos. 1,969,479; 2,311,082; 2,343,703; 
2,369,489; 2,575,182; 2,600,788; 2,706,685; 2,908,573; 3,061,432; 
3,062,653; 3,152,896; 3,153,816; 3,214,437; 3,253,924; 3,311,476; 
3,419,391; 3,519,429; 3,725,067; 3,770,447; 3,907,571; 3,928,044; 
3,935,015; 4,120,723; 4,123,281; 4,199,361; 4,336,325; 4,351,897; 
4,385,111; 4,401,752; 4,407,936; 4,413,054; 4,283,472; 4,338,393; 
4,420,556; 4,443,536; 4,500,630; 4,522,915; 4,540,654; 4,576,912; 
4,581,326; 4,621,046; 4,728,598; 4,774,172; and 4,853,319 European Patent 
Applications Nos. 284,239; 284,240; 240,852; 170,164; and 177,765; 
Japanese Patent Publication Nos. 60/170854, 60/194451 and 60/194452 and 
Great Britain Patents Nos. 1,047,612, 1,357,372 and 1,530,272, and 
"Farbkuppler-eine Literaturubersicht", published in Agfa Mitteilungen, 
Band III, pp 126-156 (1961); the disclosures of which are incorporated 
herein by reference. 
Magenta dye-forming couplers may comprise pyrazolone compounds of the 
general formula: 
##STR19## 
pyrazolotriazole compounds of the general formula: 
##STR20## 
and pyrazolobenzimidazoles of the formula: 
##STR21## 
wherein Ar is an unsubstituted aryl group or an aryl group (including 
pyridyl) substituted with one or more substituents selected from halogen 
atoms and cyano, alkylsulfonyl, arylsulfonyl, sulfamoyl, sulfonamido, 
carbamoyl, carbonamido, alkoxy, acyloxy, aryloxy, alkoxycarbonyl, 
aryloxycarbonyl, ureido, nitro, alkyl, and trifluoromethyl, or Ar is an 
aryl group substituted with a group which forms a link to a polymeric 
chain; 
R.sup.1 is a substituted or unsubstituted phenyl group and R.sup.2 is a 
substituted or unsubstituted alkyl or phenyl group, the R.sup.1 and 
R.sup.2 substituents being individually selected from halogen atoms, and 
alkyl, aryl, alkoxy, aryloxy, carbonamido, carbamoyl, sulfonamido, 
sulfamoyl, alkylsulfinyl, arylsulfinyl, alkylsulfonyl, arylsulfonyl, 
alkoxycarbonyl, aryloxycarbonyl, acyl, acyloxy, ureido, imido, carbamate, 
heterocyclic, cyano, trifluoromethyl, alkylthio, nitro, carboxyl and 
hydroxyl groups, provided that R.sup.1 and R.sup.2 each contain at least 6 
carbon atoms or the R.sup.1 and R.sup.2 substituents may individually 
comprise a group which forms a link to a polymeric chain; 
R.sup.3 and R.sup.4 are individually selected from the group consisting of 
hydrogen, substituted and unsubstituted alkyl, substituted and 
unsubstituted phenyl, substituted and unsubstituted alkoxy, substituted 
and unsubstituted amino, substituted and unsubstituted anilino, 
substituted and unsubstituted acylamino, halogens and a group which links 
to a polymer, provided that the total number of carbon atoms contained in 
R.sup.3 and R.sup.4 is at least 6 if neither R.sup.3 nor R.sup.4 is a 
group which links to a polymer; and 
X is hydrogen or a coupling-off group selected from the group consisting of 
halogens, alkoxy, aryloxy, alkylthio, arylthio, acyloxy, sulfonamido, 
carbonamido, arylazo, nitrogen-containing heterocyclic and imido groups. 
Coupling-off groups are well known to those skilled in the photographic 
art. Generally, such groups determine the equivalency of the coupler and 
modify the reactivity of the coupler. Coupling-off groups can also 
advantageously effect the layer in which the coupler is coated or other 
layers in the photographic material by performing, after release from the 
coupler, such functions as development inhibition, bleach acceleration, 
color correction, development acceleration and the like. Representative 
coupling-off groups include, as noted above, halogens (for example, 
chloro), alkoxy, aryloxy, alkyl thio, aryl thio, acyloxy, sulfonamido, 
carbonamido, arylazo, nitrogen-containing heterocyclic groups such as 
pyrazolyl and imidazolyl, and imido groups such as succinimido and 
hydantoinyl groups. Except for the halogens, these groups may be 
substituted if desired. Coupling-off groups are described in further 
detail in: U.S. Pat. Nos. 2,355,169; 3,227,551; 3,432,521; 3,476,563; 
3,617,291; 3,880,661; 4,052,212 and 4,134,766, and in British Patent 
References Nos. 1,466,728; 1,531,927; 1,533,039; 2,006,755A and 
2,017,704A, the disclosures of which are incorporated herein by reference. 
Magenta dye-forming couplers which contain bridgehead nitrogen 5,5 fused 
ring cyclic azoles systems are particularly suitable for use with the 
stabilizers of the invention. Such couplers include pyrazolotriazoles, 
pyrazolobenzimidazoles, and imidazopyrazoles and include such couplers as 
pyrrolo[1,2-b]pyrazoles, pyrazolo[3,2-c][1,2,4]triazoles, 
pyrazolo[2,3-b][1,2,4]triazoles, imidazo[1,2-b]pyrazoles, 
imidazo[1,5-b]pyrazoles, imidazo[1,2-a]imidazoles, 
imidazo[1,2-b][1,2,4]triazoles, imidazo[2,1-c][1,2,4]triazoles, 
imidazo[5,1-c][1,2,4]triazoles and [1,2,4]triazolo[3,4-c][1,2,4]triazole. 
Specific couplers which may be used within the scope of the present 
invention include the following structures: 
##STR22## 
The coupler compounds of the present invention are known compounds and can 
be prepared by techniques known to those skilled in the art. References 
which describe the preparation of the magenta dye forming couplers are the 
patents and published applications referred to above as describing these 
compounds, and references cited therein. 
Typically, the couplers and the stabilizers with which they are associated 
are dispersed in the same layer of the photographic element in a high 
boiling organic compound known in the art as a coupler solvent. 
Representative coupler solvents include phthalic acid alkyl esters such as 
diundecyl phthalate, dibutyl phthalate, bis-2-ethylhexyl phthalate, and 
dioctyl phthalate, phosphoric acid esters such as tricresyl phosphate, 
diphenyl phosphate, tris-2-ethylhexyl phosphate, and 
tris-3,5,5-trimethylhexyl phosphate, citric acid esters such as tributyl 
acetylcitrate, 2-(2-Butoxyethoxy)ethyl acetate, and 
1,4-Cyclohexyldimethylene bis(2-ethylhexanoate), benzoic acid esters such 
as octyl benzoate, aliphatic amides such as N,N-diethyl lauramide, 
N,N-Diethyldodecanamide, N,N-Dibutyldodecanamide, mono and polyvalent 
alcohols such as oleyl alcohol and glycerin monooleate, and alkyl phenols 
such as p-dodecyl phenol and 2,4-di-t-butyl or 2,4-di-t-pentyl phenol. 
Commonly used coupler solvents are the phthalate esters, which can be used 
alone or in combination with one another or with other coupler solvents. 
Selection of the particular coupler solvent has been found to have an 
influence on the activity of the coupler as well as the hue and stability 
of the dye formed on coupling. 
Typically the amount of compound S-I range from about 0.05 to about 2.0 
moles stabilizer per mole of coupler, preferably from about 0.2 to 1.0 
moles stabilizer per mole of coupler. The magenta coupler is typically 
coated in the element at a coverage of from 0.25 mmol/m.sup.2 to 1.0 
mmol/m.sup.2, and preferably at a coverage of from 0.40 to 0.70 
mmol/m.sup.2. When a coupler solvent is employed, it typically is present 
in an amount of 0.1 to 5.0 mg/mg coupler, and preferably in an amount of 
0.5 to 2.0 mg/mg coupler. To further enhance the stability of the dyes 
formed in photographic elements in accordance with the invention, 
additional conventional stabilizing compounds may also be included. 
Throughout this application a reference to any type of chemical "group" 
includes both the unsubstituted and substituted forms of the group 
described. Generally, unless otherwise specifically stated, substituent 
groups usable on molecules herein include any groups, whether substituted 
or unsubstituted, which do not destroy properties necessary for the 
photographic utility. It will also be understood throughout this 
application that reference to a compound of a particular general formula 
includes those compounds of other more specific formula which specific 
formula falls within the general formula definition. Examples of 
substituents on any of the mentioned groups can include known 
substituents, such as: halogen, for example, chloro, fluoro, bromo, iodo; 
alkoxy, particularly those with 1 to 6 carbon atoms (for example, methoxy, 
ethoxy); substituted or unsubstituted alkyl, particularly lower alkyl (for 
example, methyl, trifluoromethyl); alkenyl or thioalkyl (for example, 
methylthio or ethylthio), particularly either of those with 1 to 6 carbon 
atoms; substituted and unsubstituted aryl, particularly those having from 
6 to 20 carbon atoms (for example, phenyl); and substituted or 
unsubstituted heteroaryl, particularly those having a 5 or 6-membered ring 
containing 1 to 3 heteroatoms selected from N, O, or S (for example, 
pyridyl, thienyl, furyl, pyrrolyl); and others known in the art. Alkyl 
substituents may specifically include "lower alkyl", that is having from 1 
to 6 carbon atoms, for example, methyl, ethyl, and the like. Further, with 
regard to any alkyl group, alkylene group or alkenyl group, it will be 
understood that these can be branched or unbranched and include ring 
structures. 
The photographic elements of this invention can be black and white elements 
(for example, using magenta, cyan and yellow dye forming couplers), single 
color elements or multicolor elements. Multicolor elements contain dye 
image-forming units sensitive to each of the three primary regions of the 
spectrum. Each unit can be comprised of a single emulsion layer or of 
multiple emulsion layers sensitive to a given region of the spectrum. The 
layers of the element, including the layers of the image-forming units, 
can be arranged in various orders as known in the art. In an alternative 
format, the emulsions sensitive to each of the three primary regions of 
the spectrum can be disposed as a single segmented layer. 
Photographic elements of this invention can have the structures and 
components shown on Research Disclosure, February 1995, Item 37038, pages 
79-114. Research Disclosure is published by Kenneth Mason Publications, 
Ltd., Dudley Annex, 12a North Street, Emsworth, Hampshire PO10 7DQ, 
ENGLAND. Specific elements can be those shown on pages 96-98 of this 
Research Disclosure item as Color Paper Elements 1 and 2, in which is 
employed in the magenta dye forming layers the stabilizer combinations of 
the present invention instead of the stabilizers shown there. A typical 
multicolor photographic element of this invention comprises a support 
bearing a cyan dye image-forming unit comprised of at least one 
red-sensitive silver halide emulsion layer having associated therewith at 
least one cyan dye-forming coupler, a magenta dye image-forming unit 
comprising at least one green-sensitive silver halide emulsion layer 
having associated therewith at least one magenta dye-forming coupler, and 
a yellow dye image-forming unit comprising at least one blue-sensitive 
silver halide emulsion layer having associated therewith at least one 
yellow dye-forming coupler. The element can contain additional layers, 
such as filter layers, interlayers, overcoat layers, subbing layers, and 
the like. All of these can be coated on a support which can be transparent 
or reflective (for example, a paper support). Photographic elements of the 
present invention may also usefully include a magnetic recording material 
as described in Research Disclosure, Item 34390, November 1992, or a 
transparent magnetic recording layer such as a layer containing magnetic 
particles on the underside of a transparent support as in U.S. Pat. Nos. 
4,279,945 and 4,302,523. The element typically will have a total thickness 
(excluding the support) of from 5 to 30 microns. While the order of the 
color sensitive layers can be varied, they will normally be red-sensitive, 
green-sensitive and blue-sensitive, in that order on a transparent 
support, (that is, blue sensitive furthest from the support) and the 
reverse order on a reflective support being typical. 
This invention also contemplates the use of photographic elements of the 
present invention in what are often referred to as single use cameras (or 
"film with lens" units). These cameras are sold with film preloaded in 
them and the entire camera is returned to a processor with the exposed 
film remaining inside the camera. Such cameras may have glass or plastic 
lenses through which the photographic element is exposed. 
In the following discussion of suitable materials for use in elements of 
this invention, reference will be made to Research Disclosure, September 
1994, Number 365, Item 36544, which will be identified hereafter by the 
term "Research Disclosure I." The Sections hereafter referred to are 
Sections of the Research Disclosure I. 
The silver halide emulsions employed in the elements of this invention can 
be either negative-working, such as surface-sensitive emulsions or 
unfogged internal latent image forming emulsions, or direct positive 
emulsions of the unfogged, internal latent image forming type which are 
positive working when development is conducted with uniform light exposure 
or in the presence of a nucleating agent. Suitable emulsions and their 
preparation as well as methods of chemical and spectral sensitization are 
described in Sections I through V. Color materials and development 
modifiers are described in Sections V through XX. Vehicles which can be 
used in the elements of the present invention are described in Section II, 
and various additives such as brighteners, antifoggants, stabilizers, 
light absorbing and scattering materials, hardeners, coating aids, 
plasticizers, lubricants and matting agents are described, for example, in 
Sections VI through X and XI through XIV. Manufacturing methods are 
described in all of the sections, other layers and supports in Sections XI 
and XIV, processing methods and agents in Sections XIX and XX, and 
exposure alternatives in Section XVI. 
With negative working silver halide a negative image can be formed. 
Optionally a positive (or reversal) image can be formed although a 
negative image is typically first formed. 
The photographic elements of the present invention may also use colored 
couplers (e.g. to adjust levels of interlayer correction) and masking 
couplers such as those described in EP 213 490; Japanese Published 
Application 58-172,647; U.S. Pat. No. 2,983,608; German Application DE 
2,706,117; U.K. Patent 1,530,272; Japanese Application A-113935; U.S. Pat. 
No. 4,070,191 and German Application DE 2,643,965. The masking couplers 
may be shifted or blocked. 
The photographic elements may also contain materials that accelerate or 
otherwise modify the processing steps of bleaching or fixing to improve 
the quality of the image. Bleach accelerators described in EP 193 389; EP 
301 477; U.S. Pat. Nos. 4,163,669; 4,865,956; and 4,923,784 are 
particularly useful. Also contemplated is the use of nucleating agents, 
development accelerators or their precursors (UK Patent 2,097,140; U.K. 
Patent 2,131,188); electron transfer agents (U.S. Pat. Nos. 4,859,578; 
4,912,025); antifogging and anti color-mixing agents such as derivatives 
of hydroquinones, aminophenols, amines, gallic acid; catechol; ascorbic 
acid; hydrazides; sulfonamidophenols; and non color-forming couplers. 
The elements may also contain filter dye layers comprising colloidal silver 
sol or yellow and/or magenta filter dyes and/or antihalation dyes 
(particularly in an undercoat beneath all light sensitive layers or in the 
side of the support opposite that on which all light sensitive layers are 
located) either as oil-in-water dispersions, latex dispersions or as solid 
particle dispersions. Additionally, they may be used with "smearing" 
couplers (e.g. as described in U.S. Pat. No. 4,366,237; EP 096 570; U.S. 
Pat. Nos. 4,420,556; and 4,543,323.) Also, the couplers may be blocked or 
coated in protected form as described, for example, in Japanese 
Application 61/258,249 or U.S. Pat. No. 5,019,492. 
The photographic elements may further contain other image-modifying 
compounds such as developer inhibitor releasing compounds (DIR's). 
The elements of the present invention may be employed to obtain reflection 
color prints as described in Research Disclosure, November 1979, Item 
18716, available from Kenneth Mason Publications, Ltd, Dudley Annex, 12a 
North Street, Emsworth, Hampshire P0101 7DQ, England, incorporated herein 
by reference. The emulsions and materials to form elements of the present 
invention, may be coated on pH adjusted support as described in U.S. Pat. 
No. 4,917,994; with epoxy solvents (EP 0 164 961); with additional 
stabilizers (as described, for example, in U.S. Pat. Nos. 4,346,165; 
4,540,653 and 4,906,559); with ballasted chelating agents such as those in 
U.S. Pat. No. 4,994,359 to reduce sensitivity to polyvalent cations such 
as calcium; and with stain reducing compounds such as described in U.S. 
Pat. Nos. 5,068,171 and 5,096,805. Other compounds useful in the elements 
of the invention are disclosed in Japanese Published Patent Applications 
83/09,959; 83/62,586; 90/072,629, 90/072,630; 90/072,632; 90/072,633; 
90/072,634; 90/077,822; 90/078,229; 90/078,230; 90/079,336; 90/079,338; 
90/079,690; 90/079,691; 90/080,487; 90/080,489; 90/080,490; 90/080,491; 
90/080,492; 90/080,494; 90/085,928; 90/086,669; 90/086,670; 90/087,361; 
90/087,362; 90/087,363; 90/087,364; 90/088,096; 90/088,097; 90/093,662; 
90/093,663; 90/093,664; 90/093,665; 90/093,666; 90/093,668; 90/094,055; 
90/094,056; 90/101,937; 90/103,409; 90/151,577. 
The silver halide used in the photographic elements of the present 
invention may be silver iodobromide, silver bromide, silver chloride, 
silver chlorobromide, silver chloroiodobromide, and the like. The type of 
silver halide grains preferably include polymorphic, cubic, and 
octahedral. The grain size of the silver halide may have any distribution 
known to be useful in photographic compositions, and may be ether 
polydispersed or monodispersed. Particularly useful in this invention are 
tabular grain silver halide emulsions. Specifically contemplated tabular 
grain emulsions are those in which greater than 50 percent of the total 
projected area of the emulsion grains are accounted for by tabular grains 
having a thickness of less than 0.3 micron (0.5 micron for blue sensitive 
emulsion) and an average tabularity (T) of greater than 25 (preferably 
greater than 100), where the term "tabularity" is employed in its art 
recognized usage as T=ECD/t.sup.2 where ECD is the average equivalent 
circular diameter of the tabular grains in microns and t is the average 
thickness in microns of the tabular grains. 
The average useful ECD of photographic emulsions can range up to about 10 
microns, although in practice emulsion ECD's seldom exceed about 4 
microns. Since both photographic speed and granularity increase with 
increasing ECD's, it is generally preferred to employ the smallest tabular 
grain ECD's compatible with achieving aim speed requirements. 
Emulsion tabularity increases markedly with reductions in tabular grain 
thickness. It is generally preferred that aim tabular grain projected 
areas be satisfied by thin (t&lt;0.2 micron) tabular grains. To achieve the 
lowest levels of granularity it is preferred to that aim tabular grain 
projected areas be satisfied with ultrathin (t&lt;0.06 micron) tabular 
grains. Tabular grain thicknesses typically range down to about 0.02 
micron. However, still lower tabular grain thicknesses are contemplated. 
For example, Daubendiek et al. U.S. Pat. No. 4,672,027 reports a 3 mole 
percent iodide tabular grain silver bromoiodide emulsion having a grain 
thickness of 0.017 micron. 
As noted above tabular grains of less than the specified thickness account 
for at least 50 percent of the total grain projected area of the emulsion. 
To maximize the advantages of high tabularity it is generally preferred 
that tabular grains satisfying the stated thickness criterion account for 
the highest conveniently attainable percentage of the total grain 
projected area of the emulsion. For example, in preferred emulsions 
tabular grains satisfying the stated thickness criteria above account for 
at least 70 percent of the total grain projected area. In the highest 
performance tabular grain emulsions tabular grains satisfying the 
thickness criteria above account for at least 90 percent of total grain 
projected area. 
Suitable tabular grain emulsions can be selected from among a variety of 
conventional teachings, such as those of the following: Research 
Disclosure, Item 22534, January 1983, published by Kenneth Mason 
Publications, Ltd., Emsworth, Hampshire P010 7DD, England; U.S. Pat. Nos. 
4,439,520; 4,414,310; 4,433,048; 4,643,966; 4,647,528; 4,665,012; 
4,672,027; 4,678,745; 4,693,964; 4,713,320; 4,722,886; 4,755,456; 
4,775,617; 4,797,354; 4,801,522; 4,806,461; 4,835,095; 4,853,322; 
4,914,014; 4,962,015; 4,985,350; 5,061,069 and 5,061,616. 
The silver halide grains to be used in the invention may be prepared 
according to methods known in the art, such as those described in Research 
Disclosure I and James, The Theory of the Photographic Process. These 
include methods such as ammoniacal emulsion making, neutral or acidic 
emulsion making, and others known in the art. These methods generally 
involve mixing a water soluble silver salt with a water soluble halide 
salt in the presence of a protective colloid, and controlling the 
temperature, pAg, pH values, etc, at suitable values during formation of 
the silver halide by precipitation. 
The silver halide to be used in the invention may be advantageously 
subjected to chemical sensitization with noble metal (for example, gold) 
sensitizers, middle chalcogen (for example, sulfur) sensitizers, reduction 
sensitizers and others known in the art. Compounds and techniques useful 
for chemical sensitization of silver halide are known in the art and 
described in Research Disclosure I and the references cited therein. 
The photographic elements of the present invention, as is typical, provide 
the silver halide in the form of an emulsion. Photographic emulsions 
generally include a vehicle for coating the emulsion as a layer of a 
photographic element. Useful vehicles include both naturally occurring 
substances such as proteins, protein derivatives, cellulose derivatives 
(e.g., cellulose esters), gelatin (e.g., alkali-treated gelatin such as 
cattle bone or hide gelatin, or acid treated gelatin such as pigskin 
gelatin), gelatin derivatives (e.g., acetylated g the like), and others as 
described in Research Disclosure I. Also useful as vehicles or vehicle 
extenders are hydrophilic water-permeable colloids. These include 
synthetic polymeric peptizers, carriers, and/or binders such as poly(vinyl 
alcohol), poly(vinyl lactams), acrylamide polymers, polyvinyl acetals, 
polymers of alkyl and sulfoalkyl acrylates and methacrylates, hydrolyzed 
polyvinyl acetates, polyamides, polyvinyl pyridine, methacrylamide 
copolymers, and the like, as described in Research Disclosure I. The 
vehicle can be present in the emulsion in any amount useful in 
photographic emulsions. The emulsion can also include any of the addenda 
known to be useful in photographic emulsions. These include chemical 
sensitizers, such as active gelatin, sulfur, selenium, tellurium, gold, 
platinum, palladium, iridium, osmium, rhenium, phosphorous, or 
combinations thereof. Chemical sensitization is generally carried out at 
pAg levels of from 5 to 10, pH levels of from 5 to 8, and temperatures of 
from 30 to 80.degree. C., as illustrated in Research Disclosure, June 
1975, item 13452 and U.S. Pat. No. 3,772,031. 
The silver halide may be sensitized by sensitizing dyes by any method known 
in the art, such as described in Research Disclosure I. The dye may be 
added to an emulsion of the silver halide grains and a hydrophilic colloid 
at any time prior to (e.g., during or after chemical sensitization) or 
simultaneous with the coating of the emulsion on a photographic element. 
The dye/silver halide emulsion may be mixed with a dispersion of color 
image-forming coupler immediately before coating or in advance of coating 
(for example, 2 hours). 
Photographic elements of the present invention are preferably imagewise 
exposed using any of the known techniques, including those described in 
Research Disclosure I, section XVI. This typically involves exposure to 
light in the visible region of the spectrum, and typically such exposure 
is of a live image through a lens, although exposure can also be exposure 
to a stored image (such as a computer stored image) by means of light 
emitting devices (such as light emitting diodes, CRT and the like). 
Photographic elements comprising the composition of the invention can be 
processed in any of a number of well-known photographic processes 
utilizing any of a number of well-known processing compositions, 
described, for example, in Research Disclosure I, or in T. H. James, 
editor, The Theory of the Photographic Process, 4th Edition, Macmillan, 
N.Y., 1977. In the case of processing a negative working element, the 
element is treated with a color developer (that is one which will form the 
colored image dyes with the color couplers), and then with a oxidizer and 
a solvent to remove silver and silver halide. In the case of processing a 
reversal color element, the element is first treated with a black and 
white developer (that is, a developer which does not form colored dyes 
with the coupler compounds) followed by a treatment to fog unexposed 
silver halide (usually chemical or light fogging), followed by treatment 
with a color developer. Preferred color developing agents are 
p-phenylenediamines. Especially preferred are: 4-amino-N,N-diethylaniline 
hydrochloride, 4-amino-3-methyl-N,N-diethylaniline hydrochloride, 
4-amino-3-methyl-N-ethyl-N-(b-(methanesulfonamido)ethylaniline 
sesquisulfate hydrate, 4-amino-3-methyl-N-ethyl-N-(b-hydroxyethyl)aniline 
sulfate, 4-amino-3-b-(methanesulfonamido)ethyl-N,N-diethylaniline 
hydrochloride and 4-amino-N-ethyl-N-(2-methoxyethyl)-m-toluidine 
di-p-toluene sulfonic acid. 
Development is followed by bleach-fixing, to remove silver or silver 
halide, washing and drying. Bleaching and fixing can be performed with any 
of the materials known to be used for that purpose. Bleach baths generally 
comprise an aqueous solution of an oxidizing agent such as water soluble 
salts and complexes of iron (III) (e.g., potassium ferricyanide, ferric 
chloride, ammonium or potassium salts of ferric ethylenediaminetetraacetic 
acid), water-soluble persulfates (e.g., potassium, sodium, or ammonium 
persulfate), water-soluble dichromates (e.g., potassium, sodium, and 
lithium dichromate), and the like. Fixing baths generally comprise an 
aqueous solution of compounds that form soluble salts with silver ions, 
such as sodium thiosulfate, ammonium thiosulfate, potassium thiocyanate, 
sodium thiocyanate, thiourea, and the like. 
The stabilizers of this invention can be used in photographic elements that 
are intended to be processed in amplification processes that use 
developer/amplifier solutions described in U.S. Pat. No. 5,324,624, for 
example. When processed in this way, the low volume, thin tank processing 
system and apparatus described in U.S. patent application Ser. No. 
08/221,711, filed Mar. 31, 1994, preferably is employed. 
The following examples further illustrate this invention. 
Singlet Oxygen Quenching Examples 
Photooxidation kinetics for compounds in accordance with the invention were 
determined with the use of a merry-go-round photochemical apparatus. The 
equipment is designed to photolyze multiple samples and/or concentrations 
simultaneously, insuring uniform radiation of all solutions. The light 
fade apparatus is equipped with a 500 watt tungsten-halogen light source 
that shines through a combination of filters onto a water jacketed beaker 
containing a merry-go-round sample holder. The function of the 
merry-go-round is to rotate the samples so that all solutions are exposed 
to the same amount of light regardless of possible nonuniformity of the 
light source or of the filter system. The lamp and filter system portion 
of the apparatus remain stationary during operation. Two photolysis units 
were constructed. The two units are identical with the exception that one 
is a single lamp unit while the other is equipped with an additional lamp 
and filter system for increased light intensity. The distance from the 
plane of light to the closest sample position is approximately 15 inches 
for the single lamp unit and approximately 3.5 inches for the double lamp 
unit. The double and single lamp units, as well as the distances, were 
selected to achieve intensities that permit convenient and practical 
irradiation times. 
The apparatus can accommodate one sample holder, and holders with both 6 
and 20 sample capacity are available. Sample holders that accommodate HPLC 
autosampler vials, as well as spectrophotometric cuvettes (1 cm 
pathlength) have been constructed. The samples are immersed in the water 
bath for temperature control. The filter holder is designed to hold 
multiple 6.5.times.6.5 inch glass filter plates, and combinations of 
appropriate filters allow for isolation of a narrow band of light if 
needed. All samples are rotated past the light source(s) at a constant 
rotation speed, and the entire volume of solution is exposed to the light 
source(s). A controller activates the light and the motion of the 
merry-go-round. The time of irradiation and the speed of rotation of the 
merry-go-round may be set by the user. 
Methylene Blue, Rose Bengal, and 1,3-diphenylisobenzofuran (DPBF) were 
purchased from Aldrich Chemical Company. HPLC grade acetonitrile and 
methanol were obtained from J. T. Baker. All reagents were used without 
further purification. Solvents were bubbled with air for 15 minutes prior 
to use. Spectrophotometric measurements were determined with a Hewlett 
Packard HP8450a spectrophotometer. 
The ability of compounds to act as quenchers of .sup.1 O.sub.2 was 
determined by measuring its effect on the Methylene Blue-sensitized 
photooxidation of DPBF in methanol. In this system Methylene Blue is the 
sensitizer and DPBF is the acceptor. The photooxidation was followed by 
spectrophotometrically monitoring the decrease in DPBF absorption at 410 
nm as a function of time. Solutions containing 2.2.times.10.sup.-4 M 
Methylene Blue and 5.6.times.10.sup.-5 M DPBF were irradiated at various 
times in the absence of stabilizer and in the presence of 
2.times.10.sup.-3 M and 5.times.10.sup.-3 M stabilizer. Photolysis times 
ranged from 2 seconds to 10 minutes. The experiment used the single lamp 
fade unit and the 20-position merry-go-round cuvette holder. A 610 nm 
cutoff filter was employed to ensure that only the sensitizer absorbed the 
light. The entire experiment, including sample preparation, was conducted 
in the dark. A general reaction scheme mechanism for .sup.1 O.sub.2 
processes for this system is depicted in FIG. 1. The first step of the 
reaction scheme is absorption of light (hv) by the sensitizer to produce 
an excited state sensitizer (.sup.1 Sens). The quencher (Q) can in 
principle inhibit the reaction of the acceptor (A) by quenching singlet 
(.sup.1 Sens) or triplet (.sup.3 Sens) sensitizer, or by quenching or 
reacting with .sup.1 O.sub.2. The excited singlet state (.sup.1 Sens) has 
a short lifetime and, therefore, quenching of the singlet is too 
inefficient to be of concern with most quenchers. The triplet state is 
generated by intersystem crossing (isc) and due to its longer lifetime it 
has a better chance to react. If the triplet sensitizer energy is greater 
than 22 kcal/mol, it can transfer energy to molecular oxygen generating 
singlet oxygen. Many singlet oxygen quenchers can interact with the 
excited triplet state of the sensitizer, thus decreasing the amount of 
.sup.1 O.sub.2 generated. 
The electronically excited .sup.1 O.sub.2 molecules produced by energy 
transfer from triplet state sensitizer to molecular oxygen can exist in 
two excited states. The lower energy state, .sup.1 .DELTA..sub.g, (22 
kcal/mol) is much longer lived and is believed to be the .sup.1 O.sub.2 
species which leads to reaction in solution. .sup.1 O.sub.2 (.sup.1 
.DELTA..sub.g) reactions comprise several pathways where chemical 
reactions and physical quenching are competitive processes. The rate 
constants ka, kd, and kq+kr represent the acceptor, solvent and stabilizer 
deactivation of .sup.1 O.sub.2. The acceptor reaction with .sup.1 O.sub.2 
results in the formation of the oxidized product, .sup.1 O.sub.2. The 
quencher is intended to inhibit the interactions of .sup.1 O.sub.2 and 
acceptor. There are two types of processes by which the stabilizer can 
remove .sup.1 O.sub.2 molecules. The first is physical quenching and the 
second is a destructive process termed chemical quenching. In addition 
solvent dependent radiationless decay of .sup.1 O.sub.2 regenerates ground 
state oxygen. 
The concentration of DPBF as a function of photolysis time was measured and 
the experimental data were fit by non-linear regression to obtain the 
first order rate constant (kobs) for the fade of DPBF. From the 
experimental absorbance vs time curves, it was possible to calculate the 
rates of DPBF disappearance in the absence and presence of quencher. 
Assuming that .sup.1 O.sub.2 quenching is the only important inhibition 
(i.e. no quenching of sensitized excited states), then the following 
kinetic expression represents the photooxidation of the acceptor in the 
presence of quencher; 
EQU -d[A]/dt=K([A]/(kd/ka+[A]+kq/ka[Q] Equation 1 
where K is proportional to the rate of singlet oxygen production and is 
constant for a constant concentration of sensitizer, and kq is the 
combined rate for physical and chemical quenching of .sup.1 O.sub.2. The 
integrated form of Equation 1 was derived, and after substituting the 
experimentally determined kobs into the integrated expression, the ratio 
of the .sup.1 O.sub.2 quenching rate constant (kq) and the acceptor 
reaction rate constant (ka) is given by 
EQU kq/ka=(K-(A.sub.0 -A.sub.inf)(1-e.sup.-kobs)/.E-backward..sub.A 
-.beta.kobs)/[Q] Equation 2 
where A.sub.0 is the initial absorbance, .E-backward..sub.A represents the 
extinction coefficient of DPBF (21,000 Lmol.sup.-1 cm.sup.-1), and the 
constant .beta. defined as kd/ka is characteristic for a given acceptor in 
a known solvent. The constant K was determined from Equation 3 by 
following the decay rate of DPBF in the absence of quencher. 
EQU K=(A.sub.0 -A.sub.inf)(1-e.sup.-kobs)/.E-backward..sub.A 
+.beta.kobsEquation 3 
The final absorbance (A.sub.inf) and all other values are known. The .beta. 
value for the highly reactive chemical acceptor, DPBF, in methanol was 
determined by spectrophotometrically monitoring the Rose Bengal-sensitized 
photooxygenation reaction between DPBF and .sup.1 O.sub.2. Five methanol 
solutions of DPBF, ranging in concentration from 2.times.10.sup.-5 to 
2.times.10.sup.-4 M and containing identical quantities of Rose Bengal 
(2.7.times.10.sup.-4 M), were prepared in the dark. The solutions were 
irradiated for 10 seconds under identical conditions using the single lamp 
fade apparatus. Photolysis was carried out in disposable semimicro 
cuvettes at 23.degree. C. The absorbance at 410 nm was recorded for each 
concentration of acceptor following photolysis. 
In the absence of a .sup.1 O.sub.2 quencher, .sup.1 O.sub.2 either decays 
regenerating ground state oxygen, .sup.3 O.sub.2, or reacts with colored 
acceptor (A) to form a colorless product (AO.sub.2). The instantaneous 
quantum yield for product formation (.O slashed..sub.AO.sbsb.2) is 
EQU .O slashed..sub.AO.sbsb.2 =(.O 
slashed..sup.3.sub.Sens)ka[A]/(kd+ka[A])Equation 4 
where .O slashed..sup.3.sub.Sens is the quantum yield of triplet 
sensitizer. At low acceptor concentration, ka[A]&lt;kd and .O 
slashed..sub.AO.sbsb.2 is proportional to [A]. Substituting the constant 
.beta. for kd/ka, the reciprocal of Equation 4 becomes 
EQU 1/.O slashed..sub.AO.sbsb.2 =.sub.1/ .O slashed..sup.3.sub.Sens 
(1+.beta./[A]) Equation 5 
If the light flux is constant within a series of reactions then the amount 
of product formed in a given time of irradiation can be substituted since 
it is proportional to .O slashed..sub.AO.sbsb.2. A plot of the reciprocal 
of the product concentration vs the reciprocal of the mean acceptor 
concentration was fit by linear regression. The value of .beta. was 
obtained from the slope/intercept ratio. This relationship is valid only 
if the acceptor concentration does not change appreciably during the 
reaction (negligible conversion). 
The stability of compounds to singlet oxygen was determined in both 
methanol and acetonitrile. The dual lamp fade unit with a 610 nm cutoff 
filter was used to excite the sensitizer (Methylene Blue). Solutions 
containing 4.3.times.10.sup.-5 M Methylene Blue and a single low 
stabilizer concentration (1.5.times.10.sup.-4 M) were irradiated for 
various times using the 6-position HPLC vial sample holder. The photolysis 
times ranged from 30 minutes to 8 hours. The disappearance of the 
stabilizer was monitored by HPLC employing a 100.times.2.1 mm HP Hypersil 
C-18 column with either a 0.1 M ammonium acetate/acetonitrile or a 0.1% 
TFA/acetonitrile gradient elution system. The relative reactivity of 
compounds with .sup.1 O.sub.2 were determined by calculating the 
stabilizer half-life (t.sub.1/2) in the presence of .sup.1 O.sub.2. 
Results for compounds S-I-1 through S-I-6, S-I-19 and S-I-20 in accordance 
with the invention and comparison compounds Comp-1 through Comp-7 
evaluated as described above are given in Table I below: 
______________________________________ 
Comp-1 
#STR23## 
Comp-2 
##STR 4## 
- Comp-3 
#STR25## 
- Comp-4 
#STR26## 
- Comp-5 
#STR27## 
- Comp-6 
#STR28## 
- Comp-7 
##STR29## 
______________________________________ 
Compound k.sub.g k.sub.a 
t.sub.1/2 (MeCN) (hr) 
Comments 
______________________________________ 
S-I-1 0.3 3.7 Invention 
S-I-2 0.31 3.8 Invention 
S-I-3 0.28 3.2 Invention 
S-I-4 0.27 3.4 Invention 
S-I-5 0.2 2.4 Invention 
S-I-6 0.12 2.0 Invention 
S-I-19 0.39 1.3 Invention 
S-I-20 0.39 1.2 Invention 
Comp-1 0.18 2.6 Comparison 
Comp-2 0.19 3.0 Comparison 
Comp-3 0.12 3.0 Comparison 
Comp-4 0.22 &lt;0.5 Comparison 
Comp-5 0.13 3.1 Comparison 
Comp-6 0.22 2.2 Comparison 
Comp-7 0.15 2.4 Comparison 
______________________________________ 
Compounds S-I-1 through S-I-6, S-I-19 and S-I-20 in accordance with the 
invention exhibit both good singlet oxygen quench rates and compound 
stability. Compounds S-I-1 through S-I-4 comprising sulfonamido R.sup.a 
and R.sup.b substituents with a combined .sigma.* value of approximately 
5.2 in accordance with preferred embodiments of the invention exhibit 
particularly good quench rates and compound stability in comparison to 
compounds Comp-1 through Comp-7. 
Photographic Element Examples 
Photographic elements were prepared with and without stabilizers of formula 
S-I (0, 0.017, 0.035, 0.069, 0.10, 0.17, or 0.26 g/m.sup.2, corresponding 
to 0, 0.05, 0.1, 0.2, 0.3, 0.5 and 0.75 mol stabilizer/mol coupler) by 
coating the following layers in the order listed on a polyethylene-coated 
paper support: 
______________________________________ 
1st layer 
Gelatin 3.23 g/m.sup.2 
2nd layer 
Gelatin 2.15 g/m.sup.2 
Green sensitized AgCl emulsion 0.17 g Ag/m.sup.2 
Coupler M-9 0.29 g/m.sup.2 
Dibutyl phthalate coupler solvent 0.27 g/m.sup.2 
Diethylhexyl phthalate coupler solvent 0.27 g/m.sup.2 
Stabilizer S-I-2 0-0.26 g/m.sup.2 
Surfactant Alkanol XC (E. I. Dupont) 0.26 g/m.sup.2 
3rd layer 
Gelatin 1.40 g/m.sup.2 
Bis(vinylsulfonyl)methane 0.15 g/m.sup.2 
Surfactants 0.04 g/m.sup.2 
______________________________________ 
The photographic elements were given stepwise exposures to green light and 
processed at 35.degree. C. as follows: 
______________________________________ 
Developer 45 sec. 
Bleach-Fix 45 sec. 
Wash (running water) 1 min. 30 sec. 
______________________________________ 
The developer and bleach-fix had the following compositions: 
______________________________________ 
Developer 
Triethanolamine 12.41 g 
Blankophor REU .TM. (Mobay Corp.) 2.30 g 
Lithium polystyrene sulfonate 0.09 g 
N,N-Diethylhydroxylamine 4.59 g 
Lithium sulfate 2.70 g 
N-{2-[(4-amino-3-methylphenyl) 5.00 g 
ethylamino]ethyl}methanesulfonamide 
sesquisulfate 
1-Hydroxyethyl-1,1-diphosphonic acid 0.49 g 
Potassium carbonate, anhydrous 21.16 g 
Potassium chloride 1.60 g 
Potassium bromide 7.00 mg 
Water to make 1.00 L 
pH adjusted to 10.4 @ 26.7.degree. C. 
Bleach-Fix 
Ammonium thiosulfate 71.85 g 
Ammonium sulfite 5.10 g 
Sodium metabisulfite 10.00 g 
Acetic acid (glacial) 10.20 g 
Ammonium ferric 48.58 g 
ethylenediaminetetraacetate 
Ethylenediaminetetraacetic acid 3.86 g 
Water to make 1.00 L 
pH adjusted to 6.7 @ 26.7.degree. C. 
______________________________________ 
Magenta dyes were formed upon processing. The density of each strip was 
measured. The strips were then covered by UV-absorbing filters (in lieu of 
coating a similar filter layer over the photosensitive layer of the 
elements) and subjected to irradiation by the light of a xenon arc lamp at 
an intensity of 50 klux for two weeks. Photographic elements containing 
stabilizer compound S-I-2 in accordance with the invention showed 
significantly improved light stability of the magenta dye as evidenced by 
the density to green light remaining from an initial density of 1.0 in 
comparison to the element containing no S-I-2. 
A specific embodiment of the invention is a multilayer element provided on 
a reflective support and employing silver chloride emulsions and coated as 
taught in Research Disclosure, September 1996, Item 38957 which is 
exemplified by the following: 
______________________________________ 
Coating Format Laydown mg/m.sup.2 
______________________________________ 
Layer Blue Sensitive Layer 
Gelatin 1300 
Blue sensitive silver 640 
Yellow Coupler Y-1 440 
St-3 440 
S-1 190 
Layer Interlayer 
Gelatin 650 
Sc-1 55 
S-1 160 
Layer Green Sensitive Layer 
Gelatin 1100 
Green sensitive silver 70 
Magenta Coupler M-29 270 
S-1 75 
S-2 32 
St-1 20 
S-I-2 165 
St-2 530 
Layer UV Interlayer 
Gelatin 635 
UV-1 30 
UV-2 160 
Sc-1 50 
S-3 30 
S-1 30 
Layer Red Sensitive Layer 
Gelatin 1200 
Red sensitive silver 170 
Cyan Coupler C-1 365 
S-1 360 
UV-2 235 
S-4 30 
Sc-1 3 
Layer UV Overcoat 
Gelatin 440 
UV-1 20 
UV-2 110 
Sc-1 30 
S-3 20 
S-1 20 
Layer SOC 
Gelatin 490 
Sc-1 17 
SiO.sub.2 200 
Surfactant 2 
______________________________________ 
Y-1 
#STR30## 
- M-29 
#STR31## 
- C-1 
#STR32## 
- S-1 
#STR33## 
- S-2 
#STR34## 
- S-3 
#STR35## 
S-4 CH.sub.3 COOC.sub.2 H.sub.4 OC.sub.2 H.sub.4 OC.sub.4 H.sub.9 
Sc-1 
#STR36## 
- St-1 
#STR37## 
- St-2 
#STR38## 
- St-3 N-t-butyl(acrylamide)/n-butyl acrylate 
copolymer(50:50) 
- 
UV-1 
#STR39## 
- UV-2 
##STR40## 
______________________________________ 
The invention has been described by reference to preferred embodiments, but 
it will be understood changes can be made to the embodiments specifically 
described herein within the spirit and scope of the invention.