Hermann Mathias, Wassy Daniel, Kohn Julia, Seitz Philipp, Betschart Martin U, Grimme Stefan, Esser Birgit
Institute for Organic Chemistry, University of Freiburg, Albertstr. 21, 79104, Freiburg, Germany.
Mulliken Center for Theoretical Chemistry, University of Bonn, Beringstr. 4, 53115, Bonn, Germany.
Angew Chem Int Ed Engl. 2021 May 3;60(19):10680-10689. doi: 10.1002/anie.202016968. Epub 2021 Mar 23.
Conjugated nanohoops allow to investigate the effect of radial conjugation and bending on the involved π-systems. They can possess unexpected optoelectronic properties and their radially oriented π-system makes them attractive for host-guest chemistry. Bending the π-subsystems can lead to chiral hoops. Herein, we report the stereoselective synthesis of two enantiomers of chiral conjugated nanohoops by incorporating dibenzo[a,e]pentalenes (DBPs), which are generated in the last synthetic step from enantiomerically pure diketone precursors. Owing to its bent shape, this diketone unit was used as the only bent precursor and novel "corner unit" in the synthesis of the hoops. The [6]DBP[4]Ph-hoops contain six antiaromatic DBP units and four bridging phenylene groups. The small HOMO-LUMO gap and ambipolar electrochemical character of the DBP units is reflected in the optoelectronic properties of the hoop. Electronic circular dichroism spectra and MD simulations showed that the chiral hoop did not racemize even when heated to 110 °C. Due to its large diameter, it was able to accommodate two C60 molecules, as binding studies indicate.
共轭纳米环有助于研究径向共轭和弯曲对相关π体系的影响。它们可能具有意想不到的光电特性，其径向取向的π体系使其在主客体化学中具有吸引力。弯曲π子系统可导致手性环。在此，我们报道了通过引入二苯并[a,e]并五苯（DBP）立体选择性合成手性共轭纳米环的两种对映体，DBP是在最后一步合成中由对映体纯的二酮前体生成的。由于其弯曲形状，该二酮单元被用作环合成中唯一的弯曲前体和新型“角单元”。[6]DBP[4]Ph环包含六个反芳香性DBP单元和四个桥连亚苯基。DBP单元小的HOMO-LUMO能隙和双极性电化学特性反映在环的光电性质中。电子圆二色光谱和分子动力学模拟表明，即使加热到110°C，手性环也不会外消旋。结合研究表明，由于其直径较大，它能够容纳两个C60分子。
