Synthesis, Photophysical, and Electrochemical Properties of Pyrenes Substituted with Donors or Acceptors at the 4- or 4,9-Positions

We
report herein an efficient and direct functionalization of the
4,9-positions of pyrene by Ir-catalyzed borylation. Three pinacol
boronates (-Bpin), including 4-(Bpin)-2,7-di­(tert-butyl)­pyrene (5), 4,9-bis(Bpin)-2,7-di­(tert-butyl)­pyrene (6), and 4,10-bis(Bpin)-2,7-di­(tert-butyl)­pyrene
(7), were synthesized. The structures of 6 and 7 have been confirmed by single-crystal X-ray diffraction.
To demonstrate the utility of these compounds, donor (NPh2)-substituted compounds 4-diphenylamino-2,7-di­(tert-butyl)­pyrene (1) and 4,9-bis(diphenyl­amino)-2,7-di­(tert-butyl)­pyrene
(2) have been synthesized on a gram scale. Acceptor (BMes2)-substituted compounds 4,9-bis(BMes2)­pyrene (3) and 4,9-bis(BMes2)-1,2,3,6,7,8-hexa­hydro­pyrene (4) were synthesized for comparison. The photophysical and
electrochemical properties of compounds 1–4 have been studied both experimentally and theoretically.
The S0 → S1 transitions of the 4- or
4,9-disubstituted pyrenes, 1–3, are
allowed, with moderate fluorescence quantum yields and radiative decay
rates. The photophysical and electrochemical properties of 1–3 were compared with the 2,6-naphthalenylene-cored
compound 4 as well as the previously reported 2,7- and
1,6- pyrenylene-cored compounds.

本文报道了一种通过铱催化硼化反应（Ir-catalyzed borylation），对芘的4,9位进行高效直接官能化的方法。我们成功合成了三种频哪醇硼酸酯（pinacol boronate，-Bpin）类化合物：4-(Bpin)-2,7-二叔丁基芘（5）、4,9-二(Bpin)-2,7-二叔丁基芘（6）以及4,10-二(Bpin)-2,7-二叔丁基芘（7）。化合物6与7的结构经单晶X射线衍射（single-crystal X-ray diffraction）得以确证。

为验证此类化合物的应用潜力，我们以克级规模合成了给体（donor）取代的化合物4-二苯基氨基（NPh2）-2,7-二叔丁基芘（1）与4,9-二(二苯基氨基)-2,7-二叔丁基芘（2）。为开展对比研究，我们还合成了受体（acceptor）取代的化合物4,9-二(BMes2)芘（3）与4,9-二(BMes2)-1,2,3,6,7,8-六氢芘（4）。

我们通过实验与理论计算相结合的手段，对化合物1至4的光物理性质（photophysical properties）与电化学性质（electrochemical properties）展开了系统研究。4位或4,9位取代的芘类化合物1至3的基态（S0）→第一单重激发态（S1）跃迁为自旋允许跃迁，且具备中等水平的荧光量子产率与辐射跃迁速率。

我们将化合物1至3的光物理与电化学性质，与以2,6-萘二亚基为核的化合物4，以及此前已报道的以2,7-和1,6-芘二亚基为核的相关化合物进行了对比分析。