Structure of Ion\nPair Receptor Combined with Li<sup>+</sup>Cl<sup>–</sup> in\nConcentrated Acetonitrile Solutions\nStudied by Neutron Diffraction with <sup>6</sup>Li/<sup>7</sup>Li\nIsotopic Substituti

Neutron diffraction measurements with the <sup>6</sup>Li/<sup>7</sup>Li isotopic substitution method have been carried\nout to obtain direct\nstructural information on the ion pair receptor, C<sub>16</sub>H<sub>34</sub>O<sub>4</sub>N<sub>4</sub>, combined with Li<sup>+</sup>Cl<sup>–</sup> ion pair in concentrated acetonitrile solutions. The\ndifference interference term, Δ<sub>Li</sub>(<i>Q</i>), was derived from the difference between the total interference\nterm observed for <sup>6</sup>Li- and <sup>7</sup>Li-enriched sample\nsolutions. Structural parameters concerning the Li<sup>+</sup>Cl<sup>–</sup>–receptor complex were determined by the least-squares\nfitting analysis of the observed Δ<sub>Li</sub>(<i>Q</i>). It has been found that the Li<sup>+</sup> forms bonds with two\nether–oxygen atoms of the receptor molecule with the distances\nof <i>r</i>(Li<sup>+</sup>···O) = 1.88(4)\nand 1.9(1) Å and simultaneously one Cl<sup>–</sup> and\none N atom of a CD<sub>3</sub>CN molecule in concentrated 12 and 7\nmol % LiCl–receptor solutions in CD<sub>3</sub>CN, respectively.