2D NMR, FT-IR, ESI MS studies and DFT, PM5 semiempirical calculations of new benzoic semduramicin anhydride and their complexes with selected monovalent cations

A new benzoic semduramicin anhydride (SemBz) was obtained. The new compound and its ability to form complexes with monovalent cations was studied by the ESI mass spectrometry, DFT, 2D NMR and FT-IR spectroscopic methods. The FT-IR spectra indicate that the K+ cation in SemBz complex is localised. However, Li+ and Na+ cations in SemBz complexes undergoes fast fluctuations between oxygen atoms inside the cavity of the molecule. These observations were compared to the behavior of semduramicin salts with these cations. The structures of all salts and complexes obtained were calculated by the PM5 semiempirical method. All results are in agreement with the spectroscopic data and allow visualisation of SemBz structure and its complexes with monovalent cations.