Syntheses and X-ray crystal structures of derivatives of 2,2′,4,4′,6,6′-hexaiodobiphenyl

Iodination of 1,1'-biphenyl-3,3',5,5'-tetrol and 1,1'-biphenyl-3,3'-diol with ICl afforded the corresponding 2,2',4,4',6,6'-hexaiodo derivatives. Hydrophilic residues aimed at masking the lipophilicity of the iodine atoms were introduced by alkylation of the OH groups. The solid state structures, which were obtained by X-ray crystallography, of three hexaiodinated derivatives (namely 5, 7 and 13) show that, as expected, the two aromatic rings are forced to lie in nearly perpendicular planes by the hindrance of the four iodine atoms adjacent to the inter-annular C-C bond. The hexaiodinated biphenyl skeleton was investigated as the core backbone of a new class of X-ray contrast media.