Jozef Hodyl PhD Thesis - Theses - Flinders University

6.1.7 Guest inclusion studies with precursor silica materialsThere exists the possibility that the silica surface or the silane linker may adsorbguest molecules. Therefore, to determine whether percent inclusion values obtainedfrom guest inclusion experiments are correspondingly enhanced, both pristine SiO 2and Si-GPS, 33, were treated with guest anions using some of the guest species usedin the previous studies with Si-GPS-[Cd(Trac)](ClO 4 ) 2 , 94. Neither SiO 2 nor Si-GPS,33, showed any significant uptake of any of the guest molecules tested. For bothmaterials the uptake of any guest species was less than 3%.Inclusion was also attempted with hydroxybenzoate guest species usingcadmium-free ligand materials Si-GPS-Trac, 43, and Si-GPS-TriPTrac, 45, todetermine their binding capability. The observed percent uptake for these materialswas considerably reduced to values of between 10 and 20% indicating that metal-ioncomplexation is a necessary feature for activation of these receptor materials toenable guest inclusion.6.1.8 Characterisation of the silica immobilised host-guest complexesSolid materials that are not readily solubilised, without disturbance of theircomposition, present difficulties in their characterisation. These problems can beovercome by subjecting these materials to analytical methods that are non-intrusiveand yet provide useful information about the material. One such technique is solidstate NMR, in particular 13 C CPMAS NMR. It is a very effective method fordetermining structure within solid materials. As the host-guest complexes formed inthe preceding work are immobilised on a silica surface their characterisation wasachieved in this way.A sample size of ~150 mg of the silica immobilised host-guest material wastamped into a 4 mm zirconium oxide rotor stoppered with a Kel-F end-cap. The112