Porphyrins: XVIII. Luminescence of (Co), (Ni), Pd, Pt complexes

Abstract

Luminescence spectra were taken on a large number of Co, Ni, Pd, and Pt porphyrin complexes. The Co complexes were examined with the metal in oxidation states I, II, and III. In no case have excitation spectra confirmed that a Co or Ni complex luminesce, and in the purest samples an upper limit of phosphorescence yield is φ p < 0.0005. Pd and Pt complexes phosphoresce strongly with yields between 0.2 and 0.9. Lifetimes, yields, and vibrational peaks are reported. Yields of Pd porphin and Pt etioporphyrin are found to be relatively temperature independent up to the melting point of the solvent. Both Pd and Pt etioporphyrins phosphoresce in degassed room temperature liquids. The Pd porphin main phosphorescence band is split in low temperature alkane solution; the temperature dependence of the two peaks suggests that they arise from a geometry change in the excited state.