Chiral tetracoordinate organoboranes based on double B←N bridged bipyridine with circularly polarized luminescence

Abstract

Circularly polarized luminescence (CPL) has received great attention because CPL materials are very promising in chiroptical applications. In this article, we report a new kind of chiral tetracoordinate organoborane with excellent CPL performance, which is based on double B←N bridged bipyridine (BNBP). These two molecules, consisting of one BNBP skeleton and two axially chiral binaphthyl groups, were synthesized via the Et₂AlCl-mediated reaction. Their chiral structures and properties were fully studied by single-crystal structural analyses, circular dichroism and circularly polarized luminescence measurements, as well as theoretical calculations. Notably, they display remarkable fluorescence properties with the quantum yields exceeding 0.40 in the solid state. Moreover, they possess good CPL efficiencies with the luminescence dissymmetric factors of up to ±2.0 × 10⁻³. As disclosed, the BNBP and binaphthyl groups play an important role in producing these excellent CPL properties. The development of new building blocks is thus very desirable for high-performance CPL chromophores.