New texaphyrin-type expanded porphyrins

Abstract

This paper presents the synthesis of several new Schiff-base type expanded porphyrins. A dimeric, tetraazacyclodotetradecane-linked texaphyrin system has been prepared. It, as its gadolinium(III) adduct, displays a relaxivity in aqueous solution that is roughly 5 times higher than the benchmark texaphyrin monomer currently undergoing human clinical trials as a potential MRI enhancing and X-ray radiation sensitizing drug. Polymeric gadolinium(III) texaphyrin species, derived from poly-L-lysine and a glycosylated poly-L-lysine, have also been prepared; they too display greatly enhanced relaxivities. In work along different lines, the synthesis of an "expanded" texaphyrin has been effected and the construction of two "three dimensional" texaphyrin-inspired targets accomplished. These latter define a new class of pyrrolic cryptands.