| abstract |
1. Compounds of general Formula I ##STR1## wherein n and m in each case mean the numbers 0, 1, 2, 3 and 4, n X stands for a hydrogen atom and/or a metal ion equivalent of an element of atomic numbers 21-29, 31, 32, 37-39, 42-44, 49 or 57-83, n R 1 and R 2 , being different, mean in each case a hydrogen atom or a straight-chain, branched, saturated or unsaturated C 0 -C 20 -alkylene group, this alkylene group exhibiting at the end either a second molecule of general Formula I A or I B ##STR2## a functional group, or, linked by way of this functional group, a bio- or macromolecule, are valuable diagnostic and therapeutic media, |