(Invited) Synthesis and Photophysical Properties of Cyclometalated Iridium(III) Complexes Having Arylborane Units Toward the Photoreaction

Cyclometalated iridium(III) complexes are known to show intense absorption and bright phosphorescence at room temperature and have been applied to photosensitizer and light-emitting materials. For such applications of the complexes, the study of synthetic tuning of the HOMO/LUMO energies of the complexes through introduction of electron-withdrawing substituent(s) on the ligand and/or that of heteroaromatic ring(s). By introducing another interaction site into Ir complexes, it is considered that a more sensitive HOMO/LUMO energies change occurs. Therefore, we focused on the arylborane compounds. When boron has a tri-substituted structure, it has an vacant p-orbital and has a planar structure. Since this vacant p-orbital shows Lewis acidity, it is considered that it acts as an acceptor site. Furthermore, the excited-states of arylborane derivatives are expected to be utilized to photoinduced electron transfer systems. Therefore, in this study, we synthesized a novel iridium(III) complexes having various boron substituents, which is thought to cause intramolecular charge transfer, and investigated its spectroscopic properties. Figure 1