Relaxometric Study of Copper [15]Metallacrown-5 Gadolinium Complexes Derived from α-Aminohydroxamic Acids

Proton nuclear magnetic relaxation dispersion (NMRD) profiles were recorded between 0.24 mT and 1.4 T for lanthanum(III)‐ and gadolinium(III)‐containing [15]metallacrown‐5 complexes derived from α‐aminohydroxamic acids and with copper(II) as the ring metal. The influence of the different R‐groups on the proton relaxivity was investigated, and a linear relationship between the relaxivity and the molecular mass of the metallacrown complex was found. The selectivity of the metallacrown complexes was tested by transmetalation experiments with zinc(II) ions. The crystal structure of the copper [15]metallacrown‐5 gadolinium complex with glycine hydroximate ligands is reported. The proton relaxivity of different gadolinium(III)‐containing [15]metallacrown‐5 complexes with copper(II) as the ring metal (an example of which is shown here) was determined by NMRD measurements. A linear relationship between the molecular mass and the relaxivity was found.