Synthesis and Functionalization of Cyclometalated Iridium(111) Complexes by Post-Complexation Functionalization for Biomedical and Material Sciences -Development of Intelligent Molecules Using Metal Complex Building Blocks

Cyclometalated iridium(III) (Ir(III) complexes (e.g.:fac-Ir(tolpy)(3) (tolpy = 2-(4'-tolyl)pyridine), fac-Ir(ppy)(3) (ppy = 2-phenylpyridine) are extremely stable in water and organic solvents and are used as organic light emission diodes (OLEDs) and cell imaging materials due to its high emission properties. In the syntheses of various cyclometalated metal complexes, appropriate ligands are prepared and then used for the complexation with metal salts. Therefore, it is generally difficult to synthesize various metal complexes that contain labile and/or unstable functional groups under harsh reaction conditions (such as high temperature). In this review, we describe regioselective substitution reactions and successive conversions of the cyclometalated Ir (III) complexes to many derivatives for the synthesis of the functionalized Ir(III) complexes such as Ir complex-peptide hybrids (IPHs), Ir complex-chromophore hybrids (ICHs), which is called "post-complexation functionalization", and their application to biomedical and material sciences. The synthesis of heteroleptic triscyclometalated Ir complexes via Zn-2+-promoted degradation reactions is also described.