Hydrogensquarates of 3-nicotinoyl and 3-isonicotinoyl coumarin—Crystal structures and spectroscopic elucidation

Two novel hydrogensquarates of 3-nicotinoyl (1) and 3-isonicotinoyl (2) coumarin have been synthesized and their structures and properties elucidated spectroscopically and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy, UV-spectroscopy and negative ESI MS. Quantum chemical calculations were used to obtain the electronic structure, vibrational data and electronic spectra. The IR-spectroscopic elucidation is carried out by a comparison with the characteristics of corresponding neutral 3-nicotinoyl and 3-isonicotinoyl coumarins.