Marro Nicolas, Della Sala Flavio, Kay Euan R
EaStCHEM School of Chemistry , University of St Andrews , North Haugh , St Andrews , KY16 9ST , UK . Email:
Chem Sci. 2019 Nov 14;11(2):372-383. doi: 10.1039/c9sc04195h. eCollection 2020 Jan 14.
Nanoparticle-based devices, materials and technologies will demand a new era of synthetic chemistry where predictive principles familiar in the molecular regime are extended to nanoscale building blocks. Typical covalent strategies for modifying nanoparticle-bound species rely on kinetically controlled reactions optimised for efficiency but with limited capacity for selective and divergent access to a range of product constitutions. In this work, monolayer-stabilized nanoparticles displaying complementary dynamic covalent hydrazone exchange reactivity undergo distinct chemospecific transformations by selecting appropriate combinations of 'nucleophilic' or 'electrophilic' nanoparticle-bound monolayers with nucleophilic or electrophilic molecular modifiers. Thermodynamically governed reactions allow modulation of product compositions, spanning mixed-ligand monolayers to exhaustive exchange. High-density nanoparticle-stabilizing monolayers facilitate reaction monitoring by quantitative F NMR spectroscopy. Kinetic analysis reveals that hydrazone exchange rates are moderately diminished by surface confinement, and that the magnitude of this effect is dependent on mechanistic details: surface-bound electrophiles react intrinsically faster, but are more significantly affected by surface immobilization than nucleophiles. Complementary nanoparticles react with each other to form robust covalently connected binary aggregates. Endowed with the adaptive characteristics of the dynamic covalent linking process, the nanoscale assemblies can be tuned from extended aggregates to colloidally stable clusters of equilibrium sizes that depend on the concentration of a monofunctional capping agent. Just two 'dynamic covalent nanoparticles' with complementary thermodynamically governed reactivities therefore institute a programmable toolkit offering flexible control over nanoparticle surface functionalization, and construction of adaptive assemblies that selectively combine several nanoscale building blocks.
基于纳米颗粒的器件、材料和技术将开启合成化学的新时代，在这个时代，分子领域熟悉的预测原理将扩展到纳米级构建块。用于修饰纳米颗粒结合物种的典型共价策略依赖于为提高效率而优化的动力学控制反应，但在选择性和多样化获取一系列产物组成方面的能力有限。在这项工作中，展示互补动态共价腙交换反应性的单层稳定纳米颗粒，通过选择具有亲核或亲电分子修饰剂的“亲核”或“亲电”纳米颗粒结合单层的适当组合，经历独特的化学特异性转变。热力学控制的反应允许调节产物组成，范围从混合配体单层到彻底交换。高密度纳米颗粒稳定单层有助于通过定量¹⁹F NMR光谱监测反应。动力学分析表明，表面限制会适度降低腙交换速率，并且这种影响的程度取决于机理细节：表面结合的亲电试剂本质上反应更快，但比亲核试剂更容易受到表面固定的影响。互补的纳米颗粒相互反应形成坚固的共价连接二元聚集体。赋予动态共价连接过程的适应性特征，纳米级组装体可以从扩展聚集体调整为取决于单官能封端剂浓度的平衡尺寸的胶体稳定簇。因此，仅两个具有互补热力学控制反应性的“动态共价纳米颗粒”就构成了一个可编程工具包，可灵活控制纳米颗粒表面功能化，并构建选择性组合多个纳米级构建块的适应性组装体。
