Stable neutral radicals of planar N2O2-type dipyrrin platinum complexes: hybrid radicals of the delocalized organic π-orbital and platinum d-orbital

Abstract

Neutral radicals of N₂O₂-dipyrrin platinum complexes were synthesized by the reaction of dipyrrin ligands with PtCl₂(cod) and successive one-electron oxidation. The radicals are very stable even under aerobic and ambient conditions. X-ray crystallographic analysis revealed the stacking array of the planar dipyrrin complex moieties. The ESR signals were broadened and significantly downfield shifted. The absorption spectra exhibited NIR bands. These results indicated a delocalized radical character with a contribution by the platinum d-orbital.