ic101099z_si_001.pdf (129.67 kB)

Structural and Magnetic Effects of meso-Substitution in Alkyl-Substituted Metalloporphyrinate π-Cation Radicals: Characterization of [Fe(TalkylP)(Cl)]SbCl6 (alkyl = ethyl and n-propyl)

Download (129.67 kB)
journal contribution
posted on 06.09.2010 by Ming Li, Teresa J. Neal, Graeme R. A. Wyllie, Charles E. Schulz, W. Robert Scheidt
We report the preparation and characterization of two meso-alkyl substituted porphyrin π-cation radical derivatives, [Fe(TalkylP)(Cl)]SbCl6 (alkyl = ethyl or propyl). Both complexes have been characterized by UV/vis/near-IR, IR, and Mössbauer spectroscopy, temperature-dependent solid-state magnetic susceptibility measurements, and X-ray structure determinations. All data for both oxidized species are consistent with the formulation of the complexes as ring-oxidized iron(III) porphyrin species. The molecular structures of the two five-coordinate species have the typical square-pyramidal coordination group of high-spin iron(III) derivatives. The crystal structures also reveal that the species form cofacial π−π dimers with lateral shifts of 1.44 Å and 3.22 Å, respectively, for the propyl and ethyl radical derivatives. Both radicals exhibit porphyrin cores with alternating bond distance patterns in the inner 16-membered ring. In addition, [Fe(TEtP)(Cl)]SbCl6 and [Fe(TPrP)(Cl)]SbCl6 have been characterized by temperature-dependent (6−300 K) magnetic susceptibility studies, the best fitting of the temperature-dependent moments reveal strong coupling between iron spins and porphyrin radical, and a smaller magnitude of antiferromagnetic coupling between ring radicals, which are opposite to those found in the five-coordinate iron(III) OEP radicals. The differences in structure and properties of the cation radical meso-alkyl and β-alkyl derivatives possibly reflect differences in properties of a1u- and a2u-forming radicals.

History

Exports