Multinuclear NMR, FT-IR, ESI MS studies and PM5 semiempirical calculations of new ethylene glycol ester of lasalocid acid and their complexes with K+ cation

摘要

A new lasalocid ester with ethylene glycol (Las4) was synthesised. The new ester and its ability to complex formation with K+ cations was studied by the electron spray ionization (ESI) mass spectrometry, H-1, C-13 NMR and FT-IR spectroscopic methods. The ESI MS spectra indicated that the new ester formed stable 1: 1 complex with K+ cation independent of the stoichiometry and cone voltage values used. With increasing cone voltages, only the degradations of the Las4-K+ complex with formation of fragmentary cation complexes were found. The NMR and FT-IR spectra of Las4 in chloroform indicated the formation of the keto form, whereas in acetonitrile, the existence of keto and enol forms was detected. For the Las4-K+ complex, these two tautomeric forms were conserved. The PM5 semiempirical calculations are in agreement with the spectroscopic data and allow visualization of Las4 structure, its complex with K+ cation and the fragmentary K+ complexes. (C) 2004 Elsevier B.V. All rights reserved.