Department of Chemistry, University of California, Irvine, Irvine, California 92697-2025, United States.
J Am Chem Soc. 2023 Apr 5;145(13):7648-7658. doi: 10.1021/jacs.3c01574. Epub 2023 Mar 23.
Fluorescence lifetime imaging microscopy (FLIM) reveals vesicle sizes, structures, microenvironments, reagent partitioning, and system evolution with two chemical reactions for widely used surfactant-water systems under conditions relevant to organic synthesis, including during steps of Negishi cross-coupling reactions. In contrast to previous investigations, the present experiments characterize surfactant systems with representative organohalide substrates at high concentrations (0.5 M) that are reflective of the preparative-scale organic reactions performed and reported in water. In the presence of representative organic substrates, 2-iodoethylbenzene and 2-bromo-6-methoxypyridine, micelles swell into emulsion droplets that are up to 20 μm in diameter, which is 3-4 orders of magnitude larger than previously measured in the absence of an organic substrate (5-200 nm). The partitioning of reagents in these systems is imaged through FLIM─demonstrated here with nonpolar, amphiphilic, organic, basic, and oxidative-addition reactive compounds, a reactive zinc metal powder, and a palladium catalyst. FLIM characterizes the chemical species and/or provides microenvironment information inside micelles and vesicles. These data show that surfactants cause surfactant-dictated microenvironments inside smaller micelles (<200 nm) but that addition of a representative organic substrate produces internal microenvironments dictated primarily by the substrate rather than by the surfactant, concurrent with swelling. Addition of a palladium catalyst causes the internal environments to differ between vesicles─information that is not available through nor predicted from prior analytical techniques. Together, these data provide immediately actionable information for revising reaction models of surfactant-water systems that underpin the development of sustainable organic chemistry in water.
荧光寿命成像显微镜（FLIM）揭示了囊泡的大小、结构、微环境、试剂分配以及在与有机合成相关的条件下（包括 Negishi 交叉偶联反应的步骤中）进行的两个化学反应的系统演化。与之前的研究不同，本实验在高浓度（0.5 M）下用有代表性的有机卤化物底物来表征表面活性剂体系，这反映了在水中进行的制备规模的有机反应以及已报道的反应。在有代表性的有机底物（2-碘代乙基苯和 2-溴-6-甲氧基吡啶）存在的情况下，胶束膨胀成乳液液滴，直径可达 20 µm，这比以前在没有有机底物的情况下测量的尺寸（5-200nm）大 3-4 个数量级。通过 FLIM 可以对这些体系中的试剂分配进行成像——这里用非极性、两亲性、有机、碱性和氧化加成反应性化合物、反应性锌粉和钯催化剂进行了演示。FLIM 可以对胶束和囊泡内的化学物质进行特征化，或提供微环境信息。这些数据表明，表面活性剂在较小的胶束（<200nm）内产生表面活性剂决定的微环境，但添加有代表性的有机底物会产生主要由底物而非表面活性剂决定的内部微环境，同时发生膨胀。添加钯催化剂会导致囊泡内的内部环境不同——这是通过之前的分析技术无法获得或预测的信息。这些数据共同为修订表面活性剂-水体系的反应模型提供了即时可行的信息，该模型是在水中发展可持续有机化学的基础。
