Narrow-Line and Broadband Spectra of Iridium(III) Complexes in a Shpol'skii Matrix and an Amorphous Host

Abstract

Narrow-line emission and excitation spectra of the lowest triplet state have been studied in a Shpol'skii host (n-octane) for three cyclometalated IrL(2)acac complexes of current practical interest. The ligands L and acac are the C-deprotonated anions of 2-phenylpyridine, 2-benzothienylpyridine, 1-phenylisoquinoline, and acetylacetone. The occurrence of narrow lines is surprising for such nonplanar structures. Individual triplet sublevels are identified, and a striking intensity effect is observed in a magnetic field. Broadband spectra and lifetime data of the complexes in PMMA yield additional properties of the individual sublevels-radiative and nonradiative decay rates and emission spectra. The data are consistent with the assumption that these individual rates and spectra are approximately independent of temperature. For each complex, the decay rates vary by a factor of > or =20 among the three sublevels, and that of the lowest sublevel is the smallest, but rates of radiative and nonradiative decay generally vary in parallel for all three sublevels. The individual sublevels have significantly different spectra. These regularities appear to be universal characteristics of Ir(III) and Pt(II) complexes. They cannot be explained solely on the basis of the symmetries of the electronic states because the symmetry of the present complexes is too low.