Silica-bonded calixarenes in chromatography .1. Synthesis and characterization by solid-state NMR spectroscopy

Two different reaction schemes have been used to synthesize silica-bonded calixarene phases. Specifically, a triethoxysilyl calix[4]arene is reacted with silica to produce a bonded calix[4]arene tetraamide phase, and a hydride-derivatized silica undergoes a hydrosilylation reaction with p-allylcalix[6]arene hexaester to give a calix[6]arene hexaester phase. The resulting products were characterized by C-13 and Si-29 cross polarization/magic angle spinning NMR spectroscopy. The spectra clearly show calixarene bonding to the silica surface and are invaluable in determining the nature and extent of chemical modification of the surface with these macrocyclic compounds.