Boron-Bridged π-Conjugated Ladders as Efficient Electron-Transporting Emitters

Four diboron-bridged ladder molecules 1–4 have been designed and synthesized. X-ray diffraction analysis revealed that the bulky phenyl substituents on boron centers efficiently prevented π stacking of the luminescent ladder unit. Characterizations of these complexes demonstrated that the construction of diboron-containing ladder-type skeletons endowed these materials with good thermal stability, high fluorescence quantum yields, and strong electron affinity. The highly efficient nondoped organic light-emitting diodes using complexes 1 and 2 as electron-transporting emitters exhibited maximum luminance values of 16 930 and 18 060 cd/m2 with turn-on voltages of 3.5 and 2.5 V as well as maximum luminous efficiencies of 6.4 and 5.4 cd/A, respectively.