Supramolecular Polymers of Chiral and Achiral Rhodium and Iridium Complexes of N-Confused Porphyrin

A series of rhodium(III) and iridium(III) complexes of N-confused porphyrin (NCP) was synthesized and characterized by spectroscopic, electrochemical, and XRD methods. The results were analyzed and corroborated by DFT calculations. Insertion of the metal ions was carried out in the presence of primary alcohols (EtOH, n-PrOH), affording diamagnetic chiral square-pyramidal complexes, HNCPM(Acyl), bearing a C-bonded apical acyl ligand. By exploiting H-bonding between the apical ligand and 2-NH, in the solid state, the complexes formed 1-D polymeric chains composed of homochiral (for rhodium(III)) or heterochiral (for iridium(III)) monomers. The optical activity of these molecules in solution was established by CD for HPLC-separated enantiomers. Redox properties were studied by electrochemical and spectroelectrochemical methods. Relatively low first oxidation potentials of the NCP complexes of both metals allowed facile reaction with I2 as an oxidant and a source of the anionic ligands. The paramagnetic six-coordinated HNCPMI2 complexes formed in the solid state 1-D polymeric chains bridged by I2, interacting by halogen bonding with axial iodides. Analysis of the electronic structures of these complexes using EPR and DFT calculations revealed a predominantly π-radical character of the metal(III) complexes rather than tetravalent rhodium or iridium NCP species.