Synthesis of Diarylboron β ‐Diketiminate Complexes and Their Thermally Activated Delayed Fluorescence Properties
Shunichiro Ito, Ryoji Himeno, Shun Omagari, Shota Hosoya, Mengfei Wang, Suguru Yoshida, Katsuhisa Tanaka, Yasuchika Hasegawa, Kazuo Tanaka, Yoshiki ChujoABSTRACT
Diarylboron β ‐diketiminate complexes were synthesized through the complexation between β ‐diketimine and the corresponding triarylboranes. The crystal samples exhibited dual‐emission behavior, and the ratios of the two peaks varied with temperature. Temperature‐dependent photoluminescence (PL) spectroscopy suggested that the thermochromic luminescence properties observed in the crystalline state should originate from thermally activated delayed fluorescence (TADF). The results of photophysical measurements and density functional theory calculations implied that the intersystem crossing processes in this class of complexes should involve higher‐lying triplet excited states. The intensity ratio between shorter and longer wavelength PL bands showed an Arrhenius‐type relationship against temperature. Therefore, these complexes could be applied as a ratiometric luminescent thermometer.