Controlling the Electronic Structures and Excited-State Characteristics of Dipyrrinatoiridium(III) Complexes by an Arylborane or an Arylamino Unit

Novel dipyrrinatoiridium(III) complexes, in which a typical element substituent (i.e., arylborane or arylamino group) was introduced at the meso position of the 5-phenyldipyrrinato ligand, were designed and synthesized. The (dimesitylboryl)phenyl complex 1 showed fascinating photophysical properties arising from a synergistic interaction between metal-to-ligand charge transfer/ligand-to-ligand charge transfer and charge transfer from the π orbital of the aryl group to the vacant p orbital on the boron atom [π(aryl)–p(B) charge transfer]. On the other hand, the (N,N-diphenylamino)phenyl complex 2 showed the most intense and longest-lived emission from the 3ππ*-type excited state in the dipyrrinato moiety among the complexes in the present study. These characteristics of the complexes were evaluated in terms of the structures and spectroscopic and photophysical properties.