Budarin Vitaliy L, Clark James H, Deswarte Fabien E I, Mueller Karl T, Tavener Stewart J
Green Chemistry Centre, Department of Chemistry, University of York, Heslington, York, UK YO10 5DD.
Phys Chem Chem Phys. 2007 Jun 14;9(18):2274-83. doi: 10.1039/b701023k. Epub 2007 Apr 16.
Magic Angle Spinning (MAS) (19)F NMR spectra have been obtained and chemical shifts measured for 37 molecules in the gas phase and adsorbed on the surfaces of six common materials: octadecyl- and octyl-functionalised chromatography silicas, Kieselgel 100 silica, Brockmann neutral alumina, Norit activated charcoal and 3-(1-piperidino)propyl functionalised silica. From these six surfaces, octadecyl-silica is selected as a non-polar reference to which the others are compared. The change in chemical shift of a fluorine nucleus within a molecule on adsorption to a surface from the gas phase, Deltadelta(gas)(surface), is described by the empirical relationship: Deltadelta(gas)(surface) = delta(s) + (alpha(s)+pi(s))/alpha(r) (Deltadelta(gas)(reference) - delta(r)) + delta(HBA) + delta(HBD), where delta(s) and delta(r) are constants that describe the chemical shift induced by the electromagnetic field of the surface under investigation and reference surface, alpha(s) and alpha(r) are the relative surface polarisability for the surface and reference, pi(s) is an additional contribution to the surface polarisabilities due to its ability to interact with aromatic molecules, and delta(HBA) and delta(HBD) are measurements of the hydrogen acceptor and donor properties of the surface. These empirical parameters are measured for the surfaces under study. Silica and alumina are found to undergo specific interactions with aromatic reporter molecules and both accept and donate H-bonds. Activated charcoal was found to have an extreme effect on shielding but no specific interactions with the adsorbed molecules. 3-(1-Piperidino)propyl functionalised silica exhibits H-bond acceptor ability, but does not donate H-bonds.
已获得魔角旋转（MAS）（19）F核磁共振光谱，并测量了37种气相分子以及吸附在六种常见材料表面上的分子的化学位移，这六种材料分别是：十八烷基和辛基官能化的色谱硅胶、硅胶100、布罗克曼中性氧化铝、诺里特活性炭以及3-（1-哌啶基）丙基官能化硅胶。从这六种表面中，选择十八烷基硅胶作为非极性参考物，将其他表面与之进行比较。分子中的氟原子核从气相吸附到表面时化学位移的变化，即Δδ（气相）（表面），由经验关系式描述：Δδ（气相）（表面）=δ（s）+（α（s）+π（s））/α（r）（Δδ（气相）（参考物）-δ（r））+δ（HBA）+δ（HBD），其中δ（s）和δ（r）是描述被研究表面和参考表面的电磁场引起的化学位移的常数，α（s）和α（r）分别是该表面和参考物的相对表面极化率，π（s）是由于其与芳香族分子相互作用的能力而对表面极化率的额外贡献，δ（HBA）和δ（HBD）是表面的氢受体和供体性质的测量值。针对所研究的表面测量了这些经验参数。发现硅胶和氧化铝与芳香族报告分子发生特定相互作用，并且既接受又供氢。发现活性炭对屏蔽有极端影响，但与吸附分子没有特定相互作用。3-（1-哌啶基）丙基官能化硅胶表现出氢受体能力，但不供氢。
