Jozef Hodyl PhD Thesis - Theses - Flinders University

acetone-d 6 . For instance, the logK for benzoate was 4.6 whereas chloride and nitrateanions gave logK values of 3.4 and 2.3, respectively.1.3.3 Amide based anion receptorsIt is well known that anion binding to proteins is not solely the domain of positivelycharged side groups, but that neutral amide linkages are also involved. The ability ofthe amide subunits to function as both hydrogen bond donors (NH group) andhydrogen bond acceptors (oxygen lone pairs on carbonyl) makes these versatilegroups for anion sequestration. Since amide based binding motifs have suchsignificance in biological systems, development of synthetic anion receptors withcomparable capabilities has been given substantial attention.5, 7, 80, 81Kondo et al. synthesised anion receptors containing an isophthalamide core withterminal amide groups bearing pyridyl moieties at their periphery. For example 13,as shown in Figure 1.6. 8213Figure 1.6 Complexation of dihydrogen phosphate by receptor 13. 82Receptor 13 forms complexes with dihydrogen phosphate and Y-shaped anionssuch as acetate by forming hydrogen bonds with the four amide NH groups. Studieshave shown that receptor 13 is selective towards H 2 PO 4 - with K(H 2 PO 4 - )/K(AcO - ) >14