Compounds of formulae (I) and (II) ##STR1## wherein the R, R.sub.1, R.sub.2, R.sub.3 and R.sub.4 groups have the meanings defined in the disclosure, are useful chelants for metal ions. The complexes of compounds (I) and (II) with paramagnetic ions are useful as contrast agents for M.R.I. imaging.
式(I)和(II)的化合物##STR1##其中R、R.sub.1、R.sub.2、R.sub.3和R.sub.4基团的含义如披露中所定义,对
金属离子是有用的
螯合剂。化合物(I)和(II)的配合物与顺磁离子形成的配合物对于磁共振成像的对比剂是有用的。