Photophysical Properties of the Series fac- and mer-(1-Phenylisoquinolinato-N∧C2′)x(2-phenylpyridinato-N∧C2′)3-xIridium(III) (x=1-3)

The photophysical properties of tris-cyclometalated iridium(III) complexes have been probed by chemical and geometric variation through the series fac- and mer-lr(piq)(x)(ppy)(3-x) (x = 1-3; piq = 1-phenylisoquinolinato-N boolean AND C-2 ', ppy = 2-phenylpyridinato-N boolean AND C-2 '). The phosphorescent decays were recorded in solution at 295 K and in polymer films from 2 to 295 K. In the heteroleptic complexes, emission occurs based solely on the piq ligand(s), at least by the nanosecond time scale, as its excited states are the lowest energy. Because fac-Ir(piq)(3) and fac-Ir(ppy)(3) possess practically the same oxidation potential, comparison of photophysical properties through the series fac-lr(piq)(x)-(ppy)(3-x) (x = 1-3) revealed the effects of having one, two, or three emissive piq ligands with no confounding effects from differences in electron withdrawing or donating properties between the spectator ppy ligands and the piq ligands. Effects of placement of piq ligands in different coordination geometries were elucidated by comparisons to the mer series.