Probing the Na+ binding site in a calix[4]arene-guanosine conjugate dimer by solid-state 23Na NMR and quantum chemical calculation

Using solid-state 23Na NMR and quantum chemical calculations we have found that the Na+ ion bound to a calix[4]arene–guanosine conjugate dimer resides slightly above the G-quartet plane and simultaneously coordinates to a water molecule in a square-pyramidal (penta-coordination) geometry.