Facile Synthesis of Novel Functionalized Silsesquioxane Nanostructures Containing an Encapsulated Fluoride Anion

The presence of strongly electron withdrawing groups on alkoxysilanes, EWG-(CH2)n-Si­(OEt)3 (where n = 1–3 and the electron-withdrawing group EWG contains an Si–C­(sp3) bond), facilitates the formation and encapsulation of the fluoride anion in a silsesquioxane cage. Such species have been studied by 19F and 29Si NMR spectroscopy and X-ray crystallography together with MALDI-TOF and ESI mass spectrometry. The EWG must not be a good leaving group. Interestingly, this strategy led only to the T8 cage and excellent yields were obtained (81–95%) even without solvent. A wide range of functionalities were used. This new route offers an opportunity to build novel nanometer-sized 3-D molecular structures with a variety of functionalities which have not been accessible in the past.在烷氧基硅烷（alkoxysilanes）上引入强吸电子基团（electron-withdrawing group, EWG），即结构为EWG-(CH2)n-Si(OEt)3的分子（其中n取值为1~3，且该吸电子基团EWG含有Si-C(sp3)键），可促进氟阴离子在倍半硅氧烷笼（silsesquioxane cage）中的形成与包封。此类物种已通过19F与29Si核磁共振波谱、X射线晶体学，结合基质辅助激光解吸电离飞行时间质谱（MALDI-TOF）与电喷雾电离质谱（ESI）开展了研究。该吸电子基团EWG不可为优良离去基团。值得注意的是，此合成策略仅生成T8笼型结构，且即便在无溶剂条件下也可获得81%~95%的优异产率。研究中使用了宽泛范围的官能团。这条全新的合成路径为构建兼具多样官能团的新型纳米级三维分子结构提供了可能，而此类结构在过往难以获取。