U.S. DOE Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA.
J Am Chem Soc. 2010 Sep 8;132(35):12452-7. doi: 10.1021/ja105007b.
The conformations of (pentafluorophenyl)propyl groups (-CH(2)-CH(2)-CH(2)-C(6)F(5), abbreviated as PFP), covalently bound to the surface of mesoporous silica nanoparticles (MSNs), were determined by solid-state NMR spectroscopy and further refined by theoretical modeling. Two types of PFP groups were described, including molecules in the prone position with the perfluorinated aromatic rings located above the siloxane bridges (PFP-p) and the PFP groups denoted as upright (PFP-u), whose aromatic rings do not interact with the silica surface. Two-dimensional (2D) (13)C-(1)H, (13)C-(19)F and (19)F-(29)Si heteronuclear correlation (HETCOR) spectra were obtained with high sensitivity on natural abundance samples using fast magic angle spinning (MAS), indirect detection of low-gamma nuclei and signal enhancement by Carr-Purcell-Meiboom-Gill (CPMG) spin-echo sequence. 2D double-quantum (DQ) (19)F MAS NMR spectra and spin-echo measurements provided additional information about the structure and mobility of the pentafluorophenyl rings. Optimization of the PFP geometry, as well as calculations of the interaction energies and (19)F chemical shifts, proved very useful in refining the structural features of PFP-p and PFP-u functional groups on the silica surface. The prospects of using the PFP-functionalized surface to modify its properties (e.g., the interaction with solvents, especially water) and design new types of the heterogeneous catalytic system are discussed.
（五氟苯基）丙基基团（-CH(2)-CH(2)-CH(2)-C(6)F(5)，缩写为 PFP）通过固态 NMR 光谱学确定了其在介孔硅纳米粒子（MSNs）表面的构象，并通过理论建模进一步进行了细化。描述了两种类型的 PFP 基团，包括处于易位的分子，其全氟芳环位于硅氧烷桥上方（PFP-p）和被称为直立的 PFP 基团（PFP-u），其芳环与二氧化硅表面不相互作用。使用快速魔角旋转（MAS）、低γ核的间接检测和 Carr-Purcell-Meiboom-Gill（CPMG）自旋回波序列的信号增强，对天然丰度样品进行了具有高灵敏度的二维（2D）（13）C-（1）H、（13）C-（19）F 和（19）F-（29）Si 异核相关（HETCOR）光谱测量。二维双量子（DQ）（19）F MAS NMR 光谱和自旋回波测量提供了有关五氟苯基环的结构和迁移率的附加信息。PFP 几何形状的优化以及相互作用能和（19）F 化学位移的计算，对细化 PFP-p 和 PFP-u 官能团在二氧化硅表面上的结构特征非常有用。讨论了使用 PFP 功能化表面来修饰其性质（例如与溶剂的相互作用，特别是水）和设计新型多相催化体系的前景。
