Sodium-23 NMR Studies of Sodium Ion Ensembles with a 1,3-Alternate-Shaped Calix[4]arene

Abstract

Sodium-23 NMR longitudinal magnetization recovery (L.M.R.) study has been carried out to clarify the sodium ion exchange in ensembles with 1,3-alternate-shaped calix[4]arene 1 for the first time. The line width υ_1/2 of a sharp singlet for NaClO₄ in the absence of 1 is 65 Hz: upon addition of 1 a singlet peak was broadened to 1100 Hz (υ_1/2). The life times (τ) of Na⁺ were estimated to be (20-3.8)×10^-3 s for τ_A and (5.0-2.0)×10^-3 s for τ_B, by the simulations of sodium-23 NMR L.M.R. curves. The life times of 1-Na⁺ Ensemble are larger than those for 18-crown-6. This implies that Na⁺ cation is bound deeply in the cavity formed by two OCH₂CO groups of 1, the complex being classified as a “nest-in-type”.