| prov:value
| - ub.3 H.sub.2, --SO.sub.3 H or --CONHOH; g, h,i, j, k and m may be the same or different and are an integer from one to about six; X is --CO.sub.2 H, --PO.sub.3 H.sub.2, --SO.sub.3 H or --CONHOH.Also provided are compositions comprising complexes of the compounds with metal ions of the general formula ##STR3##wherein A is N or CR.sub.1, wherein R.sub.1 is hydrogen, C.sub.1 -C.sub.8 alkyl, or C.sub.
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