Patent ID: 7718781

Claim:
A composition comprising a targeting group attached to a complex between a gadolinium (III) ion and an organic ligand, said complex comprising a structure according to Formula I: wherein R 1 , R 2 , and R 3 are members independently selected from a linking member, H, substituted or unsubstituted alkyl, substituted or unsubstituted aryl, substituted or unsubstituted heteroalkyl, hydroxy, carboxy, amide, ester, and amino groups, with the proviso that when A is nitrogen, R 1 is other than amino, and with the further proviso that when E is nitrogen, R 3 is not present; R 4 is a member selected from a linking member, H, substituted or unsubstituted alkyl, substituted or unsubstituted heteroalkyl, substituted or unsubstituted aryl, hydroxy, carboxy, amide, and ester groups; and A, E and Z are members independently selected from carbon and nitrogen, said complex having a solubility in water of at least about 15 mM.