Patent ID: 7335771

Claim:
A compound having the formula: wherein: groups R 3 and R 4 are attached to the Z 1 ring structure and groups R 5 and R 6 are attached to the Z 2 ring structure; Z 1 and Z 2 independently represent the atoms necessary to complete a phenyl ring structure; at least one of groups R 1 and R 2 is the group -E-F, wherein E is a spacer group selected from the group consisting of: (CHR′) p — —{(CHR′) q —O—(CHR′) r } s — —{(CHR′) q —NR′—(CHR′) r } s — —{(CHR′) q —(CH═CH)—(CHR′) r } s — —{(CHR′) q —Ar—(CHR′) r } s — —{(CHR′) q —CO—NR′—(CHR′) r } s — and —{(CHR′) q —CO—Ar—NR′—(CHR′) r } s — where R′ is hydrogen, C 1 -C 4 alkyl or aryl, which may be optionally substituted with sulphonate, Ar is phenylene, optionally substituted with sulphonate, p is 1-10, q is 0-10, r is 1-10 and s is 1-5; and F is a reactive group selected from the group consisting of carboxyl, succinimidyl ester, sulpho-succinimidyl ester, isothiocyanate, maleimide, haloacetamide, acid halide, hydrazide, vinylsulphone, dichlorotriazine and phosphoramidite; groups R 3 , R 4 , R 5 , R 6 , R 7 and R 8 are independently selected from hydrogen, halogen, amide, hydroxyl, cyano, nitro, C 1 -C 6 alkoxy, C 1 -C 20 alkyl, sulphonate, and sulphonic acid; when any of groups R 1 and R 2 is not said group -E-F, said remaining group R 1 or R 2 is selected from hydrogen, mono- or di-nitro-substituted benzyl, C 1 -C 20 alkyl, and the group —(CH 2 —) n Y; Y is selected from sulphonate, sulphate, phosphonate, phosphate, quaternary ammonium and carboxyl; and n is an integer from 1 to 6.