【作者】 王忻昌； 房洪勋； 孙轶斌； 王秀秀； 杨柳林； 曹晓宇； 田中群；

【Author】 Xinchang Wang;Hongxun Fang;Yibin Sun;Xiuxiu Wang;Liulin Yang;Xiaoyu Cao;Zhongqun Tian;School of Electronic Science and Engineering,Xiamen University;College of Chemistry and Molecular Engineering,Peking University;College of Chemistry and Chemical Engineering,Xiamen University;

【机构】 厦门大学电子科学与技术学院； 北京大学化学与分子工程学院； 固体表面物理化学国家重点实验室厦门大学化学化工学院；

【摘要】 动力学表征是研究化学反应和分子组装机理的关键,其中分子组装复杂度比化学反应高,其动力学研究往往需要高分辨表征技术。核磁共振技术具有极高的能量分辨,能给出详细的结构和溶液动态信息,是分子组装中不可或缺的表征手段。然而,核磁共振技术的时间分辨率较低,仅能表征半衰期大于十分钟的反应和组装过程,极大地限制了核磁在动力学表征中的应用。为解决此瓶颈,我们发展了微流控-核磁技术,通过将微流控芯片引入核磁共振仪的探头,使反应物和产物在微流控芯片中原位混合,结合适配微流控芯片的射频线圈,实现了分子组装过程的原位、实时、高分辨表征（图1）。更重要的是,利用"空间换时间",即保持管路内流速不变,每次核磁采样均得到完全一样的谱图,实现动力学过程中同一时间点核磁谱图的累加,克服了核磁采样过程低时间分辨率的缺点。借助微流控-核磁技术的优势,我们表征了一系列分子组装和化学反应,这些过程均无法采用其他技术进行表征。首先,我们表征了一个基于准轮烷的主客体交换过程,利用氨基金刚烷将准轮烷中心的CB[7]置换出来。利用微流核磁技术,我们采集了从15秒到300秒反应过程的核磁谱,得到其动力学曲线。^[1]更进一步,通过设计一系列主客体模型并表征,得到它们的动力学级数,确定了主客体交换过程由两个决速步骤控制,分别是CB[7]从轮烷的脱离,以及氨基金刚烷与环糊精CB[8]的结合。在此过程中实现了半衰期小于5秒分子组装过程的高时间分辨核磁表征,包括1.5秒时体系二维核磁谱图。其次,还表征了一系列水相中亚胺反应,实现醛基和氨基反应的定量化预测。我们的工作证明了微流控-核磁技术研究分子组装和化学反应机理方面强大优势。更多还原

【Abstract】 Kinetics are essential for revealing mechanisms of both molecular assembly and chemical reaction.Molecular assembly is generally more complex than chemical reactions,thus its kinetic characterization needs to be high-resolution.Nuclear Magnetic Resonance（NMR） can give high-resolution structural information at the atom level and has been become an essential characterization method in molecular assembly.Nevertheless,the time-resolution of NMR is poor and has rarely been used in the study of kinetics.We developed microfluidic NMR to increase the time-resolution of NMR.By introducing a microfluidic chip into the probe of NMR,the reactants can be mixed inside the chip.Specially designed coil for NMR characterization allowed the realization of high-resolution,in situ NMR techniques.More importantly,by keeping flow rate（Q） constant,each acquisition contains the same NMR information of mixtures,allowing high signal-to-noise NMR spectra to be accumulated（Fig.1）.We applied microfluidic-NMR to characterize a series of molecular assembly and chemical reaction processes.First,we characterized host-guest processes based on pseudorotaxane,which aminoadamantane "dragged" the cucurbiturilc[7] out of pseudorotaxane.We drew the kinetic curve of this process by acquiring NMR spectra from 15 s to 300 s.^[1] Furthermore,we designed and characterized a series of model host-guest processes,from which we identified the rate-determining steps.We realized the kinetic study of molecular assembly processes with halt-life of less than 5 s, and two-dimensional NMR spectra after the assembly process started just 1.5 s.Second,we also studied a series of imine condensation in aqueous solution and realized quantitative prediction of reaction rates.Our work proved the capability of microfluidic NMR in studying mechanisms of both chemical reaction and molecular assembly processes.Keywords:Molecular assembly,Kinetic Characterization,Microfluidic NMR,Reaction Mechanisms.更多还原