Structure of Ion Pair Receptor Combined with Li+Cl– in Concentrated Acetonitrile Solutions Studied by Neutron Diffraction with 6Li/7Li Isotopic Substitution Method

Neutron diffraction measurements with the 6Li/7Li isotopic substitution method have been carried out to obtain direct structural information on the ion pair receptor, C16H34O4N4, combined with Li+Cl– ion pair in concentrated acetonitrile solutions. The difference interference term, ΔLi(Q), was derived from the difference between the total interference term observed for 6Li- and 7Li-enriched sample solutions. Structural parameters concerning the Li+Cl––receptor complex were determined by the least-squares fitting analysis of the observed ΔLi(Q). It has been found that the Li+ forms bonds with two ether–oxygen atoms of the receptor molecule with the distances of r(Li+···O) = 1.88(4) and 1.9(1) Å and simultaneously one Cl– and one N atom of a CD3CN molecule in concentrated 12 and 7 mol % LiCl–receptor solutions in CD3CN, respectively.