Two BN lsosteres of Anthracene: Synthesis and Characterization
Two BN lsosteres of Anthracene: Synthesis and Characterization
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DOI：
10.1021/ja508813v
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发表时间：
2014-10-29
影响因子：
15
通讯作者：
Liu, Shih-Yuan
中科院分区：
文献类型：
--
作者：
Ishibashi, Jacob S. A.;Marshall, Jonathan L.;Liu, Shih-Yuan
开发了两种母体 BN 蒽 1 和 2 的合成方法，并通过与全碳蒽直接比较来表征它们的电子结构和反应行为。气相紫外光电子光谱研究揭示了以下 HOMO 能量趋势：蒽，-7.4 eV； BN 蒽 1，-7.7 eV；双-BN 蒽 2，-8.0 eV。 UV-vis吸收光谱中较低能带的λmax如下： 蒽，356nm； BN 蒽 1, 359 nm;双-BN 蒽 2，357 nm。因此，尽管 HOMO 随着 BN 掺入量的增加而稳定，但整个蒽系列的 HOMO-LUMO 带隙保持不变。三种研究的蒽化合物的发射波长最大值为 403 nm。 BN 蒽 1 和双-BN 蒽 2 的 N-H 质子的 pKa 值测定为大约 26。BN 蒽 1 和 2 不发生热或光诱导的环加成反应或弗里德尔-克来福特酰化。然而，BN 蒽 1 与 Br2 的亲电溴化是在 9 位发生区域选择性的。 BN蒽的溴化反应行为和区域选择性与这些化合物的电子结构一致；即，(1) BN 蒽的较低 HOMO 能级使分子稳定，免受环加成和弗里德尔-克来福特反应，(2) HOMO 轨道系数与观察到的溴化区域选择性一致。总的来说，这项工作表明 BN/CC 电子等排现象可以作为一种分子设计策略来稳定并苯型结构的 HOMO，同时保持光学带隙。
The synthesis of two parental BN anthracenes, 1 and 2, was developed, and their electronic structure and reactivity behavior were characterized in direct comparison with all-carbon anthracene. Gas-phase UV-photoelecton spectroscopy studies revealed the following HOMO energy trend: anthracene, -7.4 eV; BN anthracene 1, -7.7 eV; bis-BN anthracene 2, -8.0 eV. The ?max of the lower energy band in the UV-vis absorption spectrum is as follows: anthracene, 356 nm; BN anthracene 1, 359 nm; bis-BN anthracene 2, 357 nm. Thus, although the HOMO is stabilized with increasing BN incorporation, the HOMO-LUMO band gap remains unchanged across the anthracene series. The emission ?max values for the three investigated anthracene compounds are at 403 nm. The pKa values of the N-H proton for BN anthracene 1 and bis-BN anthracene 2 were determined to be approximately 26. BN anthracenes 1 and 2 do not undergo heat- or light-induced cycloaddition reactions or Friedel-Crafts acylations. Electrophilic bromination of BN anthracene 1 with Br2, however, occurs regioselectively at the 9-position. The reactivity behavior and regioselectivity of bromination of BN anthracenes are consistent with the electronic structure of these compounds; i.e., (1) the lower HOMO energy levels for BN anthracenes stabilize the molecules against cycloaddition and Friedel-Crafts reactions, and (2) the HOMO orbital coefficients are consistent with the observed bromination regioselectivity. Overall, this work demonstrates that BN/CC isosterism can be used as a molecular design strategy to stabilize the HOMO of acene-type structures while the optical band gap is maintained.