Oligotriarylamine-Extended Organoboranes with Tunable Electron-Donating Strength by Changing the Number of Donor Units.

Triarylborane (ArB) and triarylamine (ArN) have been widely employed to construct electronically different donor-acceptor (D-A) systems. Herein, we describe a series of A-D-A-type luminescent organoboranes ( = 1, 3, 5) that show an increased number of ArN units as electron donors and two terminal ArB as acceptors. When the ArN moieties were extended from one to five units, their electron-donating strength was gradually enhanced and the highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps could also be tuned, which was further reflected in the red-shifted emissions from blue (λ = 458 nm) to orange (λ = 595 nm) with a decrease in from 3.19 to 2.61 eV. showed a huge Stokes shift (∼14 057 cm) and a considerably bright emission with an enhanced solid-state quantum efficiency (Φ = 98%) compared with the other members. and exhibited aggregation-induced emissions (AIEs), and an apparent solvatochromic shift was also observed in the emission spectra as the solvent was changed from hexane to tetrahydrofuran (THF) (430 → 595 nm). In addition, the donor-acceptor charge-transfer character in these organoboranes caused a thermally responsive emission over a broad range.