Oligosilanyl-Bridged Biscarbazoles: Structure, Synthesis, and Spectroscopic Properties

Oligosilanyl-bridged systems are expected to give rise to unique optoelectronic properties because of σ–π conjugation between the Si–Si σ orbital and the aryl π orbital. Herein, we synthesized a small series of novel biscarbazoles bridged with permethylated oligosilanyl units (−[Si­(CH₃)₂]n–, n = 1–4) and examined their spectroscopic properties in detail. In the target molecules BCzSin, n = 2–4, the efficient σ–π conjugation elevated the highest occupied molecular orbital energy level with no influence on the lowest unoccupied molecular orbital. In the solid state, the emission full width at half-maximum (fwhm) of all the compounds narrowed significantly, while the emission efficiency increased and the emission color of carbazole was retained. This research provided a very simple and general way of subtly manipulating the electronic properties of organic materials to construct an emissive color-retaining system for multifunctional applications.