Advanced Surface Functionalization of Periodic Mesoporous Silica: Kinetic Control by Trisilazane Reagents

详细信息    查看全文

• 作者：Clemens Zapilko ; Markus Widenmeyer ; Iris Nagl ; Frank Estler ; Reiner Anwander ; Gabriele Raudaschl-Sieber ; Olaf Groeger ; Gü ; nter Engelhardt
• 刊名：Journal of the American Chemical Society
• 出版年：2006
• 出版时间：December 20, 2006
• 年：2006
• 卷：128
• 期：50
• 页码：16266 - 16276
• 全文大小：306K
• 年卷期：v.128,no.50(December 20, 2006)
• ISSN：1520-5126

文摘

The surface reactions of mesoporous silica MCM-41 with a series of new trisilylamines(trisilazanes) (SiHMe₂)₂NSiMe₂R and (SiMe₂Vin)₂NSiMe₂R (R = indenyl, norpinanyl, chloropropyl, 3-(N-morpholin)propyl; Vin = vinyl), disilylalkylamine (SiHMe₂)iPrNSiMe₂(CH₂)₃Cl, and monosilyldialkylaminesMe₂NSiMe₂R (R = indenyl, chloropropyl, 3-(N-morpholin)propyl) were investigated. ¹H, ¹³C, and ²⁹SiMAS NMR spectroscopy, nitrogen adsorption/desorption, infrared spectroscopy, and model reactionswith calix[4]arene as a mimic for an oxo surface were used to clarify the chemical nature of surface-bondedsilyl groups. The trisilylamines exhibited a comparatively slow surface reaction, which allowed forthe adjustment of the amount of silylated and nonreacted SiOH groups and led to a stoichiometricdistribution of surface functionalities. The 2:1 integral ratio of SiHMe₂ and SiMe₂R moieties of suchtrisilazanes was found to be preserved on the silica surface as indicated by microanalytical as wellas ¹³C and ²⁹Si MAS NMR spectroscopic data of the hybrid materials. For example, the reaction of MCM-41 with (SiHMe₂)₂NSiMe₂(CH₂)₃Cl, (SiHMe₂)iPrNSiMe₂(CH₂)₃Cl, and Me₂NSiMe₂(CH₂)₃Cl provided bi- andmonofunctional hybrid materials with one-third, one-half, or all chemically accessible silanol groupsderivatized by chloropropyl groups, respectively. Thus, a molecular precursor strategy was developed toefficiently control the relative amount of three different surface species, SiHMe₂ (or SiVinMe₂), SiMe₂R,and SiOH, in a single reaction step. The reaction behavior of indenyl-substituted monosilazanes andtrisilazanes (R = Ind) with calix[4]arene proved that the indenyl substituent can act as a leaving groupforming a dimethylsilyl species, which is anchored bipodally on the silica surface, that is, via two Si-Obonds.