Patent ID: 7750163

Claim:
A compound of formula (I): wherein: Z 1 and Z 2 independently represent the carbon atoms necessary to complete a one ring, or two-fused ring aromatic system; R 1 and R 2 are independently chosen from the group -E-F, C 1 -C 6 alkyl, benzyl either unsubstituted or substituted with sulphonic acid, and the group —(CH 2 ) k —W, where W is sulphonic acid or phosphonic acid and k is an integer from 1 to 10; 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, and n=1, 2 or 3; R 3 , R 4 , R 5 and R 6 are independently selected from the group -E-F, hydrogen and sulphonic acid; each R 7 is independently the group -E-F, hydrogen or two of R 7 together with the group, form a hydrocarbon ring system having 5 or 6 atoms; each R 11 , R 12 , R 13 and R 14 is independently a group —(CH 2 ) k —W as defined above, or C 1 -C 6 alkyl; E is a single bond or a spacer group having a chain from 1-20 linked atoms selected from the group consisting of carbon, nitrogen and oxygen atoms and F is a target bonding group; wherein F is either: (i) a reactive group selected from carboxyl, succinimidyl ester, sulpho-succinimidyl ester, isothiocyanate, maleimide, haloacetamide, acid halide, hydrazide, vinylsulphone, dichlorotriazine and phosphoramidite; or (ii) a functional group selected from hydroxy, amino, sulphydryl, carbonyl (including aldehyde and ketone) and thiophosphate; or (iii) an affinity tag; with the provisos that: (a) one of groups R 1 , R 2 , R 3 , R 4 , R 5 , R 6 and R 7 is the group -E-F; (b) one or more of R 11 , R 12 , R 13 and R 14 is the group —(CH 2 ) k —W; (c) the compound of Formula I has from 3 to 5 sulfonic acid groups.