Ir(III) complexes designed for light-emitting devices: beyond the luminescence color array

In pursuing novel efficient lighting technologies and materials, phosphorescent cyclometallated Ir(III) complexes have been prominent due to their wide color arrays and highly efficient electroluminescence. Their photophysical properties are strongly influenced by spin-orbit coupling exerted by the iridium core, usually resulting in intense, short-lived emission, which can be systematically tuned as a triumph of molecular engineering. This Perspective aims to present recent breakthroughs and state of the art on emissive Ir(III) compounds, in particular a personal account on heteroleptic [Ir(N boolean AND C)(2)(L boolean AND X)](+) complexes, addressing the mechanistic concepts behind their luminescence. Their fascinating photophysical properties strengthen application in more-efficient light-emitting technologies, such as organic light-emitting diodes and light-emitting electrochemical cells.