2'-Diborylazobenzenes with Double N-B Coordination: Control of Fluorescent Properties by Substituents and Redox Reactions
2'-Diborylazobenzenes with Double N-B Coordination: Control of Fluorescent Properties by Substituents and Redox Reactions
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具有双 N-B 配位的 2-二硼基偶氮苯：通过取代基和氧化还原反应控制荧光性质
DOI：
10.1002/ejic.201200069
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发表时间：
2012
期刊：
影响因子：
--
通讯作者：
S. Nagase
中科院分区：
文献类型：
--
作者：
N. Kano;A. Furuta;T. Kambe;J. Yoshino;Y. Shibata;T.Kawashima;N. Mizorigi;S. Nagase
合成了2，2 ′-二[二（五氟苯基）硼基]偶氮苯。X射线晶体学分析显示偶氮苯部分的平面核心结构、双分子内N-B配位和两个四配位硼原子。2，2 ′-二硼偶氮苯在辐照下显示出橙子和红色的荧光发射。双N-B配位导致吸收和发射最大值的红移，以及相对于2-硼基偶氮苯衍生物的斯托克斯位移的降低。基于密度泛函理论计算2，2 ′-二硼偶氮苯的分子轨道，发现其π* 轨道（LUMO）的能级（-4.67 eV）远低于2-硼偶氮苯的π * 轨道（-3.70 eV）.在低还原电位下，2，2 ′-二硼偶氮苯的循环伏安图中观察到一个可逆的还原波。2，2 ′-二硼偶氮苯之一的单电子还原产生偶氮苯自由基阴离子，这通过活性ESR信号证实。在此偶氮苯中，荧光被还原淬灭，并通过空气氧化恢复。
2,2′‐Bis[bis(pentafluorophenyl)boryl]azobenzenes were synthesized. X‐ray crystallographic analysis exhibits a planar core structure of the azobenzene moiety, double intramolecular N–B coordination, and two tetracoordinate boron atoms. The 2,2′‐diborylazobenzenes show fluorescence emission with orange and red colors upon irradiation. The double N–B coordination causes redshifts in both the absorption and emission maxima and a decrease in the Stokes shifts relative to those of the 2‐borylazobenzene derivative. On the basis of the density functional theory calculations of the molecular orbitals of 2,2′‐diborylazobenzene, the π* orbital (LUMO) was found at a much lower energy level (–4.67 eV) than that in 2‐borylazobenzene (–3.70 eV). A reversible reduction wave was observed at a low reduction potential in the cyclic voltammograms of the 2,2′‐diborylazobenzenes. Single‐electron reduction of one of the 2,2′‐diborylazobenzenes generates an azobenzene radical anion, which was confirmed by an active ESR signal. The fluorescence was quenched by the reduction and recovered by air oxidation in this azobenzene.