Chiral Nanographene Propeller Embedding Six Enantiomerically Stable [5]Helicene Units

A one-step synthesis of a nanographene propeller with a D3-symmetry was obtained starting from 7,8-dibromo[5]­helicene by Yamamoto nickel(0) couplings. It afforded a chiral polyaromatic hydrocarbon (PAH) embedding six enantiomerically stable [5]­helicene units. This dense accumulation of helical strain resulted in a distorted geometry, but stable stereochemistry. The conformational, structural, chiroptical, and photophysical properties of the molecule are reported.以7,8-二溴[5]螺烯为起始原料，通过山本（Yamamoto）零价镍偶联反应，可一步合成具有D3对称结构的纳米石墨烯螺旋桨型分子。该产物为嵌入六个对映体稳定[5]螺烯单元的手性多环芳烃（polyaromatic hydrocarbon，PAH）。这种螺旋张力的密集堆积使得分子呈现扭曲的几何构型，但同时拥有稳定的立体化学特性。本文报道了该分子的构象、结构、手性光学及光物理性质。