A compound of formula Iα or formula Iβ below: wherein: each Y is independently O= or S=; Z is -O- or -S-; each R 2 is independently selected from -CO 2 R a, -CN, -NO 2, -N 3, -N=C=O, - N=C=S, -NO, -N=C=NR a, -S R a, -S 2 R a, -S 2 NR a R b, -C NR a R b, -C R a, -C SR a, -C OR a, -C(=S)R a, -S-CN, sulfo, phosphono, alkylphosphono and alkylsulfo, wherein R a and R b are each independently selected from the group consisting of -H, alkyl, aryl, arylalkyl, cycloalkyl, heteroalkyl and haloalkyl or optionally R a and R b when attached to the same nitrogen atom are combined to form a 5- or 6-membered ring having from 0-2 additional heteroatoms as ring members selected from O, N and S; R 3 is -H or C 1-8 alkyl; each R 4 is independently C 1-8 alkyl; the subscript m is an integer from 1-5; the subscript p is 1 or 2; and the subscript q is an integer from 0-4, provided that the compound is not selected from: wherein: each Y is independently O= or S=; Z is -O- or -S-; adjacent R 1 groups together with the benzene ring to which they are attached form a fused carbocyclic aromatic ring system selected from the group consisting of naphthalene, phenanthrene, anthracene, triphenylene and pyrene, each of which having from 1-4 R 5 substituents selected from the group consisting of -COOH, -COO-M +, sulfo, alkylsulfo, phosphono and alkylphosphono; each R 2 is independently selected from -CO 2 R a, -CN, -NO 2, -N 3, -N=C=O, - N=C=S, -NO, -N=C=NR a, -S R a, -S 2 R a, -S 2 NR a R b, -C NR a R b, -C R a, -C SR a, -C OR a, -C(=S)R a, -S-CN, sulfo, phosphono, alkylphosphono and alkylsulfo, wherein R a and R b are each independently selected from the group consisting of -H, alkyl, aryl, arylalkyl, cycloalkyl, heteroalkyl and haloalkyl or optionally R a and R b when attached to the same nitrogen atom are combined to form a 5- or 6-membered ring having from 0-2 additional heteroatoms as ring members selected from O, N and S; wherein M + is selected from the group consisting of NH 4 +, Li +, Na +, K + and R 3 is -H or C 1-8 alkyl; each R 4 is independently C 1-8 alkyl the subscript n is an integer from 0-4 provided that the compound of formula Iβ has adjacent R 1 groups forming a fused carbocyclic ring system as specified earlier in this definition of formula Iβ; the subscript m is an integer from 1-5; the subscript p is 1 or 2; and the subscript q is an integer from 0-4. each Y is independently O= or S=; Z is -O- or -S-; each R 2 is independently selected from -CO 2 R a, -CN, -NO 2, -N 3, -N=C=O, - N=C=S, -NO, -N=C=NR a, -S R a, -S 2 R a, -S 2 NR a R b, -C NR a R b, -C R a, -C SR a, -C OR a, -C(=S)R a, -S-CN, sulfo, phosphono, alkylphosphono and alkylsulfo, wherein R a and R b are each independently selected from the group consisting of -H, alkyl, aryl, arylalkyl, cycloalkyl, heteroalkyl and haloalkyl or optionally R a and R b when attached to the same nitrogen atom are combined to form a 5- or 6-membered ring having from 0-2 additional heteroatoms as ring members selected from O, N and S; R 3 is -H or C 1-8 alkyl; each R 4 is independently C 1-8 alkyl; the subscript m is an integer from 1-5; the subscript p is 1 or 2; and the subscript q is an integer from 0-4, each Y is independently O= or S=; Z is -O- or -S-; adjacent R 1 groups together with the benzene ring to which they are attached form a fused carbocyclic aromatic ring system selected from the group consisting of naphthalene, phenanthrene, anthracene, triphenylene and pyrene, each of which having from 1-4 R 5 substituents selected from the group consisting of -COOH, -COO-M +, sulfo, alkylsulfo, phosphono and alkylphosphono; each R 2 is independently selected from -CO 2 R a, -CN, -NO 2, -N 3, -N=C=O, - N=C=S, -NO, -N=C=NR a, -S R a, -S 2 R a, -S 2 NR a R b, -C NR a R b, -C R a, -C SR a, -C OR a, -C(=S)R a, -S-CN, sulfo, phosphono, alkylphosphono and alkylsulfo, wherein R a and R b are each independently selected from the group consisting of -H, alkyl, aryl, arylalkyl, cycloalkyl, heteroalkyl and haloalkyl or optionally R a and R b when attached to the same nitrogen atom are combined to form a 5- or 6-membered ring having from 0-2 additional heteroatoms as ring members selected from O, N and S; wherein M + is selected from the group consisting of NH 4 +, Li +, Na +, K + and R 3 is -H or C 1-8 alkyl; each R 4 is independently C 1-8 alkyl the subscript n is an integer from 0-4 provided that the compound of formula Iβ has adjacent R 1 groups forming a fused carbocyclic ring system as specified earlier in this definition of formula Iβ; the subscript m is an integer from 1-5; the subscript p is 1 or 2; and the subscript q is an integer from 0-4.