Jozef Hodyl PhD Thesis - Theses - Flinders University

environment to the hydrophobic interior of the CD, the binding strength is loweredaccordingly, compared to benzoic acid. 69 Moreover, studies with p-nitrobenzoateguests conducted by Davies and Savage revealed that guest species derived from p-nitrobenzoic acid bound more weakly than those from benzoic acid. They concludedthat the charged species bound as Bergeron et al. proposed, but that binding in bothcharged and uncharged species was also mediated by the electron withdrawing ordonating ability of the substituents. They ascertained that substituents with higherelectron withdrawing ability penetrated the cavity first. As the nitro group has higherelectron withdrawing ability than the carboxy moiety the carboxy group was likely toprotrude into the aqueous environment and hence the lower binding observed for p-nitrobenzoic acid derivatives. 711.3.2 CalixarenesThe calixarenes exhibit some similarity with cyclodextrins as both have recurringstructural subunits containing peripheral functional groups arranged around ahydrophobic core. 72 Since their discovery they have become the subject of manystudies as receptors due to the ease of modifying their backbones and their welldefinedupper and lower rims surrounding a central annulus, as shown for 8, a typical59, 73, 74calixarene.upper rimR 1R 1 R 1 R1annuluslower rimOOR 2 R 2 R 2 R 2OO810