Jozef Hodyl PhD Thesis - Theses - Flinders University

Conformer C had never been observed in studies using homochiral ligands of thistype, but the situation with non-homochiral ligands was unknown. 226Furthermore, this study would give an indication of any selectivity towardsparticular metal(II) ions. Finally, as each macrocyclic terminus is theoreticallyexpected to coordinate to one metal(II) ion, then the number of moles of these ionstaken up should equate to the number of moles of macrocycles immobilised on themass of functionalised silica gel provided. The results obtained from these metaluptake studies could then be compared with the loading capacity from microanalysisand thermal combustion data to verify the number of available macrocyclic receptorligands per unit mass of material. This series of experiments was also undertaken todetermine whether the time provided for metal uptake would affect the metal loadingcapacity of the receptor material.Other silica based materials: silica gel, Si-GPS, 33, Si-GPS(endcapped), 85, and,Si-GPS-Trac (endcapped), 89, were also subjected to metal(II) ion uptakeexperiments to determine whether the free linker molecules and silanol groups, bothfree and endcapped, had an effect on the uptake capacity observed in the experimentswith Si-GPSTrac, 43.5.1.1 Strategy for metal(II) ion uptake with Si-GPS-Trac, 43Metal loading experiments were conducted by the batch uptake method, with fivereplicates undertaken to check reproducibility. These were performed by shaking 10cm 3 of an aqueous solution, at pH ~5 (HEPES) containing the appropriate metal(II)nitrate (2 x 10 -2 - 5 x 10 -2 mol dm 3 ) with 100 mg of the silica based material forbetween 15 minutes and 18 hours as shown for Si-GPS-Trac, 43, in Scheme 5.1.At the end of the shaking time the silica material was recovered by filtration andthe filtrate and washings collected in a volumetric flask.88