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Abstract: Crystal structure of monensin A rubidium salt dihydrate, [Rb(C36H61O11)·2H2O], has been studied by X-ray diffraction, FT-IR spectroscopy and PM5 semiempirical methods. The crystal space group is P212121 with a =12.6153(7), b =16.4841(10), c =19.4840(12) and Z =4. The Rb–O bond lengths are between 2.788(7) and 2.901(6)Å. The carboxyl group of monensin A is deprotonated and engaged in two intramolecular O(11)–H···O(1) of 2.52(1)Å and O(10)–H···O(2) of 2.60(1)Å hydrogen bonds with hydroxyl groups, accompanied with formation of a pseudo-cyclic structure. This structure is stabilised by the coordination of the Rb+ cation by oxygen atoms. Two water molecules are involved in the weak intermolecular hydrogen bond between the different species forming a supramolecule. The IR spectrum of the crystal is consistent with the results obtained by the X-ray study and provides spectroscopic evidence for the complex formation. The calculated structure and the structural parameters of the monensin A rubidium salt are comparable with those determined by the X-ray study. [Copyright &y& Elsevier]

Abstract: For the first time the structure of the complex formed between N-allylamide of monensin A (M-AM2) and divalent cation (Sr2+) has been studied by X-ray crystallography and FT-IR spectroscopy. The crystal structure of this complex contains one Sr2+ cation coordinated by six O atoms of M-AM2 molecule, one oxygen atom of the perchlorate anion and the nitrogen atom of the acetonitrile molecule. The M-AM2 molecule is additionally tied by an intramolecular hydrogen-bonded chain [O(3)H⋯O(9)H⋯O(10)H⋯O(1)e crystal data, FT-IR spectra and semiempirical calculations show that the oxygen atom of the amide group is not involved in the coordination of the Sr2+ cation. In the gas phase the formation of two types of (M-AM2+Sr)2+ and (M-AM2+Sr+ClO4)+ complexes is detected using ESI mass spectrometry and their structures are visualized by PM5 semiempirical calculations. [Copyright &y& Elsevier]

Abstract: A complex between a new N-phenylamide of monensin A (M-AM1) and sodium chloride has been synthesised and studied by X-ray diffraction and FT-IR spectroscopy. The crystal structure of the complex between M-AM1 and sodium chloride with acetonitrile was examined using X-ray diffraction and discussed in detail. Its structure is stabilised by coordination of the Na+ cation with oxygen atoms. The Na–O bond lengths are between 2.382(2) and 2.562(2)Å. The chloride anion is involved in a weak intermolecular hydrogen bond between different species forming a supramolecule. The ESI-MS spectra indicate that the amide forms stable complexes of exclusively 1:1 stoichiometry with Na+ cations. The FT-IR spectrum of the crystal is consistent with the results obtained by the X-ray study and provides spectroscopic evidence for the complex formation. Due to its specific structural properties N-phenylamide of monensin A efficiently binds sodium chloride. The result of the PM5 semiempirical calculation is in agreement with the spectroscopic data and allows visualisation of the structure of the M-AM1–Na+ complex. The new amide of monensin A has been additionally tested in view of its antimicrobial properties. It shows great activity towards some strains of Gram-positive bacteria (MIC=6.25–12.5μg/ml). [Copyright &y& Elsevier]