Jozef Hodyl PhD Thesis - Theses - Flinders University

CHAPTER 3GUEST MOLECULE INCLUSION STUDIESWITH THE RECEPTOR MODEL3.1 BackgroundEarlier it was mentioned that prior to immobilisation of molecular receptor precursor46 onto a silica surface, guest uptake studies would be undertaken on a tri-phenoxypendant-armed, molecular receptor, to ascertain the ability of a receptor equippedwith only three aromatic groups to function as a satisfactory host species. Thesestudies were required as the silica immobilised host species would lack one aromaticgroup compared to hosts such as 26. To do this a series of guest inclusionexperiments was performed with [Cd(TracHP12)](ClO 4 ) 2 , 49, with a view toacquiring guest molecule binding constant data that could be used to gauge whetherthe loss of stability of the host-guest complex, associated with the loss of onearomatic group, would be prohibitively large or not.493.2 Measurement of Host-Guest Binding Constants3.2.1 Binding constant measurements using the 1 H NMR monitored titrationmethodTitrations in which NMR chemical shift values are monitored are routinely used as ameans of obtaining binding constant data. 190-194It is well established that upondissolution, host-guest complexes will establish the equilibrium shown in equation52