AN ASSESSMENT OF CALIXARENE AMIDES AS POTENTIAL MAGNETIC-RESONANCE-IMAGING ENHANCEMENT AGENTS FOR GADOLINIUM(III)

The compound 5, 11, 17, butyl-25,26,27,28-carbamoyloxymethoxycalix[4]a rene (1) has been evaluated as a ligand for potential use as a magneti c resonance imaging agent with gadolinium(III). The assessment procedu res include high field relaxivity H-1 NMR measurements as well as UV-V is stability constant measurement for the Gd(III) complex. Although th e selected ligand proved to be unsuitable for in vivo applications bec ause of the low stability constant for the complex it forms, the relax ivity value of R = 3.40(6) mM(-1) s(-1) is quite reasonable. These ini tial results however point to some future ligand modifications that ar e necessary in order to successfully design calixarene-based MRI enhan cement agents for Gd(III).