Gadolinium-binding cyclic hexapeptoids: synthesis and relaxometric propertiesElectronic supplementary information (ESI) available: Sodium complex formation for the cyclic peptoids 1, 2, 9 and 10 (synthetic schemes, experimental procedure and 1H NMR spectra for the free and complexed ligands), Gd3+ complex formation for 1 and 2 (titration graphs), relaxometric determination of the stability constants of Gd-1 and Gd-2 (fitting equations). See DOI: 10.1039/c3ob42029a

Two new cyclic hexapeptoids incorporating N -carboxyethylglycine and N -methoxyethylglycine residues are able to efficiently bind Gd 3+ . Their thermodynamic stabilities and relaxivities have been assessed by 1 H-relaxometric investigations. Cyclic hexapeptoids are able to efficiently bind Gd 3+ ions. Their thermodynamic stabilities have been assessed by 1 H-relaxometric investigations.