Synthesis and Characterization of an Iridium Triphyrin Complex

A sandwich complex of iridium(III) benzotriphyrin (2) has been synthesized from free-base benzotriphyrin (1) and [IrCl(cod)]₂ (COD = 1,5-cyclooctadiene). The COD ring was transformed from 1,5-COD to an η¹,η³-C₈H₁₂ unit as a π-allyl ligand associated with the valence change of iridium from Ir^I to Ir^III, as revealed by X-ray diffraction analysis. The Soret-like band of 2 was blue-shifted and broadened compared with that of 1, indicating strong electronic interactions between triphyrin and the iridium ion. Compound 2 also showed very broad absorption in the range of 500-800 nm, which can be assigned to a mixture of Q and metal-to-ligand charge-transfer bands.