<i>o</i>‑Carboranyl–Phosphine as a New Class of Strong-Field Ancillary Ligand in Cyclometalated Iridium(III) Complexes: Toward Blue Phosphorescence

Abstract

Heteroleptic tris-cyclometalated Ir­(III) complexes supported by the <i>o</i>-carboranyl–phosphine ligand (<i>CBP</i>), (C^∧N)₂Ir­(<i>CBP</i>) (C^∧N = <i>ppy</i> (<b>1</b>), <i>dfppy</i> (<b>2</b>)), have been synthesized and characterized. The PL spectra of <b>1</b> and <b>2</b> displayed substantially blue shifted phosphorescence relative to the corresponding Ir­(C^∧N)₃ complexes. Electrochemical and theoretical studies showed that the <i>CBP</i> ligand functioned as a strong-field ancillary ligand, and the greater HOMO stabilization in comparison to that of the LUMO by the <i>CBP</i> ligand was responsible for the increase in band gap, leading to a large blue shift in phosphorescence