Jozef Hodyl PhD Thesis - Theses - Flinders University

6.886.68δobs (ppm)6.486.286.085.880 1 2 3 4 5 6 7 8 9 10[H]/[G]Figure 3.8 Titration curve displaying the change in chemical shift of the H A protons of p-nitrophenolate with increasing ratio of [Cd(TracHP12)](ClO 4 ) 2 , 49. The red squaresrepresent experimental data points while the curve shows the theoretical δ values thatbest fit the calculated values of K and δ HG .The binding constant (K) values obtained from monitoring either the H A or H Bdoublets were of the same magnitude, allowing for experimental error, giving a meanvalue of logK = 3.45 ± 0.05 and showing the reproducibility of the method.3.2.5 Binding constant studies of anionic aromatic guest species with[Cd(TracHP12)](ClO 4 ) 2 , 49Binding constants for acetate, D-histidinate, L-histidinate, phenoxyacetate, and p-nitrobenzoate, with [Cd(TracHP12)](ClO 4 ) 2 , 49 were determined in the same wayand are tabulated in Table 3.1 alongside the values obtained for receptor 26.Comparing the logK values of the host-guest complexes formed with[Cd(TracHP12)] 2+ , 49, with those formed with [Cd((S)thphpc12] 2+ , 26, it is seen thatthe value obtained for p-nitrophenolate with [Cd(TracHP12)] 2+ , 49, logK = 3.45±0.05, is smaller than the value obtained with [Cd((S)thphpc12] 2+ , 26, logK = 4.2 ±0.2. This may be due to absence of the fourth aromatic moiety on the host pendant60