Molecular structure of the 1:1 inclusion complex of monensin A sodium salt with acetonitrile

Crystal structure of the inclusion crystal of monensin A sodium salt with acetonitrile, Na(C36H61O11) CH3CN, has been studied by X-ray diffraction, FT-IR spectroscopy, and PM5 semiempirical methods. The space group of the crystal is P212121 with a = 12.8116(5), b = 16.5851(6), c = 18.6807(6) and Z = 4. Within the inclusion complex the Na+ cation is coordinated by six O atoms of monensin A molecule in a distorted octahedron geometry. The Na–O bond lengths are between 2.3276(13) and 2.6033(14) Å. The oxygen atoms of the carboxylate group are involved in two intramolecular hydrogen bonds of different strength: O(11)–H⋯O(1) of 2.554(2) Å and O(10)–H⋯O(2) of 2.683(2) Å. These two hydrogen bonds bind two ends of the monensin molecule, which in this way forms a pseudo cyclic structure wrapped around the Na+ 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 sodium salt and the structural parameters are comparable with those determined from the X-ray data.