Qi Honglan, Teesdale Justin J, Pupillo Rachel C, Rosenthal Joel, Bard Allen J
Center for Electrochemistry, Department of Chemistry and Biochemistry, The University of Texas , Austin, Texas 78712, United States.
J Am Chem Soc. 2013 Sep 11;135(36):13558-66. doi: 10.1021/ja406731f. Epub 2013 Aug 27.
Two new 2,2'-bipyridine (bpy) derivatives containing ancillary BODIPY chromophores attached at the 5- and 5'-positions (BB3) or 6- and 6'-positions (BB4) were prepared and characterized. In this work, the basic photophysics, electrochemistry, and electrogenerated chemiluminescence (ECL) of BB3 and BB4 are compared with those previously reported for a related bpy-BODIPY derivative (BB2) (J. Phys. Chem. C 2011, 115, 17993-18001). Cyclic voltammetry revealed that BB3 and BB4 display reversible 2e(-) oxidation and reduction waves, which consist of two closely spaced (50-70 mV) 1e(-) events. This redox behavior is consistent with the frontier molecular orbitals calculated for BB3 and BB4 and indicates that the 2,2'-bipyridine spacer of each bpy-BODIPY homologue does not facilitate efficient electronic communication between the tethered indacene units. In the presence of a coreactant such as tri-n-propylamine (TPA) or benzoyl peroxide (BPO), BB3 and BB4 exhibit strong ECL and produce spectra that are very similar to their corresponding photoluminescence profiles. The ECL signal obtained under annihilation conditions, however, is significantly different and is characterized by two distinct bands. One of these bands is centered at ∼570 nm and is attributed to emission via an S- or T-route. The second band occurs at longer wavelengths and is centered around ∼740 nm. The shape and concentration dependence of this long-wavelength ECL signal is not indicative of emission from an excimer or aggregate, but rather it suggests that a new emissive species is formed from the bpy-BODIPY luminophores during the annihilation process.
制备并表征了两种新的2,2'-联吡啶（bpy）衍生物，其在5-和5'-位（BB3）或6-和6'-位（BB4）连接有辅助硼二吡咯发色团。在本工作中，将BB3和BB4的基本光物理、电化学和电致化学发光（ECL）与先前报道的相关bpy-硼二吡咯衍生物（BB2）（《物理化学杂志C》2011年，115卷，17993 - 18001页）进行了比较。循环伏安法表明，BB3和BB4显示出可逆的2e⁻氧化和还原波，其由两个紧密间隔（50 - 70 mV）的1e⁻事件组成。这种氧化还原行为与为BB3和BB4计算的前沿分子轨道一致，表明每个bpy-硼二吡咯同系物的2,2'-联吡啶间隔基不利于连接的茚并芴单元之间的有效电子通信。在存在三正丙胺（TPA）或过氧化苯甲酰（BPO）等共反应物的情况下，BB3和BB4表现出强烈的ECL，并产生与其相应光致发光谱非常相似的光谱。然而，在湮灭条件下获得的ECL信号明显不同，其特征在于两个不同的谱带。其中一个谱带中心位于约570 nm，归因于通过单重态或三重态途径的发射。第二个谱带出现在更长波长处，中心约在740 nm附近。这种长波长ECL信号的形状和浓度依赖性并非表明来自准分子或聚集体的发射，而是表明在湮灭过程中由bpy-硼二吡咯发光体形成了一种新的发射物种。
