1H, 13C NMR, FT-IR, ESI-MS and PM5 semiempirical study of new lasalocid ester with 3-(methylthio)-1-propanol and its complexes with monovalent cations

A new ester of lasalocid with 3-(methylthio)-1-propanol (Las10) has been synthesised and its complexation of monovalent cations has been studied by ESI mass spectrometry as well as the 1H, 13C NMR and FT-IR spectroscopic methods. The ESI-MS spectra show that Las10 forms stable 1:1 complexes with Li+, Na+, K+, Rb+ and Cs+ cations. The FT-IR spectrum of Las10 in acetonitrile solution indicates that this molecule exists in keto and enol equilibrium, in which the keto form is predominant. It is demonstrated that the cations have no influence on this keto–enol equilibrium. The results of the PM5 semiempirical calculations are in agreement with the spectroscopic data and allow visualisation of the structure of Las10 and its complexes with the cations studied.