Cation-Complexation Behavior of Template-Assembled Synthetic G-Quartets

We report the preparation and solution study of a set of template-assembled synthetic G-quartets (TASQs) bound to different cations. These G-quartet baskets effectively extract cations of different sizes and valencies. They form isolated G-quartets with small cations such as Na+ and Sr(2+), and dimeric assemblies with larger cations such as Cs+. Their structures were determined by using (1)H NMR spectroscopy, and their sizes were evaluated by using a series of pulsed-field gradient NMR experiments. The effect of anion has been studied, and the cation selectivities have been investigated by a series of competition experiments.