TRIPODAL LIGANDS POSSESSING 6 CONVERGENT HYDROXYL-GROUPS A NOVEL FAMILY OF IRON SEQUESTERING AGENTS BASED ON O,O'-DIHYDROXYBIPHENYL SUBUNITS

A new family of iron(III) sequestering agents has been designed. Tripo dal ligands possessing six convergent hydroxyl groups have been prepar ed by condensation of an appropriate o,o'-biaryl building block and a spacer. The preparations of building blocks and of simple bidentate li gands designed for comparative studies are described : several methods have been used for ortho functionalisation and for 3,3'-difunctionali sation of 2,2'-dihydroxybiphenyl. Sulfonation of the ligands led to wa ter soluble agents. These ligands offer an alternative to synthetic hy droxamate or catecholate siderophores. The hexamethoxylated tripodal p recursors and their complexing ability towards alkali cations are also described. The complexing abilities of hexahydroxylated sequestering agents towards iron(III) are comparable to those of hydroxamate sidero phores but are lower than those of catecholate siderophores.