Institute of Chemistry , The Hebrew University of Jerusalem, Edmond J. Safra Campus , Jerusalem 91904 , Israel.
Chemical Research Support Unit , Weizmann Institute of Science , Rehovot 76100 , Israel.
J Am Chem Soc. 2018 Jul 5;140(26):8086-8090. doi: 10.1021/jacs.8b04447. Epub 2018 Jun 21.
Twisting linear acenes out of planarity affects their electronic and optical properties, and induces chirality. However, it is difficult to isolate the effect of twisting from the substituent effect. Moreover, many twistacenes (twisted acenes) readily racemize in solution. Here, we introduce a series of twistacenes having an anthracene backbone diagonally tethered by an n-alkyl bridge, which induces a twist of various angles. This allows us to systematically monitor the effect of twisting on electronic and optical properties. We find that absorption is bathochromically shifted with increasing twist, while fluorescence quantum efficiency drops dramatically. The tethered twistacenes were isolated to their enantiomerically pure form, displaying strong chiroptical properties and anisotropy factor ( g-value). No racemization was observed even upon prolonged heating, rendering these tethered twistacenes suitable as enantiopure helical building units for π-conjugated backbones.
将线性并苯扭转成非平面结构会影响其电子和光学性质，并诱导手性。然而，扭转的影响很难与取代基效应区分开来。此外，许多扭曲并苯（扭曲并苯）在溶液中很容易外消旋。在这里，我们引入了一系列具有蒽骨架的扭曲并苯，它们由 n- 烷基桥对角桥接，从而诱导出各种角度的扭转。这使我们能够系统地监测扭转对电子和光学性质的影响。我们发现，随着扭转的增加，吸收发生红移，而荧光量子效率急剧下降。桥接的扭曲并苯被分离成其对映体纯的形式，显示出强的圆二色性和各向异性因子（g 值）。即使长时间加热也没有观察到外消旋，这使得这些桥接的扭曲并苯适合作为π 共轭主链的对映纯螺旋构建单元。
