Tuning Emission of AIE-Active Organometallic Ir(III) Complexes by Simple Modulation of Strength of Donor/Acceptor on Ancillary Ligands

A new design strategy to tune emission color of aggregation-induced emission (AIE) Ir(III) complexes, by simply adjusting the strength of donor/acceptor on ancillary ligands, is reported. Herein, all studied Ir(III) complexes employ 1-(2,4-difluorophenyl)-1H-pyrazole as cyclometalated ligands but different pyridine-1,2,4-triazolyl moieties as ancillary ligands that were modified with carbazole end-capped alkyl groups, in which pyridine-1,2,4-triazolyl moieties and functionalized carbazole act as donor and acceptor units, respectively. The experimental and theoretical results clearly reveal the intrinsic relationship between structures and emission behaviors. Enhancing the ability of donor and/or acceptor leads to red-shifted emission and vice versa. In addition, one of the designed dyes exhibits the reversible and significant mechanochromic luminescent behavior thanks to its efficient AIE characteristic and structural modification, providing a feasible way to design multifunctional materials.