Molecular structure of the 1:1 inclusion complex of monensin a lithium salt with acetonitrile

Crystal structure of the inclusion crystal of monensin A lithium salt with acetonitrile, Li(C36H61O11)center dot CH3CN, has been studied by X-ray diffraction, FT-IR spectroscopy and PM5 semiempirical methods. Monensin A lithium salt: acetonitrile (1: 1) complex is isostructural with the previously studied crystals of monensin A sodium salt: acetonitrile (1:1) complex. The crystal space group is P2(1)2(1)2(1) with a = 12.6937(9), b = 16.7689(12), c = 18.4927(12) and Z = 4. The Li-O bond lengths are between 2.022(5) and 2.633(5) angstrom. The oxygen atoms of the carboxylate group are involved in two intramolecular hydrogen bonds of different strength: O(11)-H center dot center dot center dot O(1) of 2.582(2)angstrom and O(10)-H center dot center dot center dot O(2) of 2.636(2) angstrom. These two hydrogen bonds bind two ends of the monensin molecule, which in this way forms a pseudo cyclic structure wrapped around the Li+ cation. The IR spectrum of the crystal confirms the results obtained by the X-ray study and provides spectroscopic evidence for the formation of the inclusion complex. The calculated structure of the monensin A lithium salt and the structural parameters are comparable with those determined by X-rays. (c) 2007 Elsevier B.V. All rights reserved.