Jozef Hodyl PhD Thesis - Theses - Flinders University

ange of pH due to its high basicity. 5 Examples of guanidinium derived receptors arethe foldable bis-guanidinium receptors 5 and 6 synthesised by Schiessl andSchmidtchen. 58 It was discovered that receptor 5 was good at binding dicarboxylateguest anions such as oxylate, malonate, isophthalate and p-nitroisophthalate givinglogK values of 3.4, 4.2, 3.8 and 4.2, respectively.OOHNNHHNNNHORHNRO2Cl5, R = SiPh 2 tBu6, R = HEach of the complexes formed displayed 1:1 H:G (host:guest) binding by analysisusing 1 H NMR monitored titrations in CD 3 OD. Both receptor 5 and 6 also showedaffinity for nucleotide phosphates in polar solvents. For example 1 H NMR monitoredtitration studies with 5 gave logK values of between 4.3 and 4.6 in CD 3 OD while 6bound H 2 PO 4 - with a logK of 3.0 in D 2 O. Receptor 6 is also capable of bindingbiological materials, for example 5'-adenosine monophosphate (5'AMP) with a logK58, 59of 4.0.Exploration and synthesis of receptors for anionic guest species has sincebroadened beyond straightforward predisposition of positively charged regionswithin a host species, which, by their electronic status, are inclined toward bindinganions. Later receptors included architectures based on calixarenes, cryptands,cyclodextrins, steroids and crown ethers that use singly, or in combination, neutralhydrogen bond donor groups, hydrophobic binding, electrostatic van der Waals7