New structural motifs and properties of squaric acid anions in the presence of the l-lysinium counterion

Two novel l-lysinium hydrogensquarate monohydrate (1) and the corresponding salt of the l-lysinium dication (2) are synthesized and their structure and properties elucidated in detail spectroscopically, thermally and structurally, using single crystal X-ray diffraction, linear-polarized solid-state IR-spectroscopy oriented colloid suspensions in nematic host, TGA, DSC, DTA methods, positive and negative HPLC tandem mass spectrometry (ESI-MS·MS). Quantum chemical methods are used to calculate the electronic structure, vibrational data and electronic spectra. Two novel structural motifs have been obtained, isolated [(HSq−)] and tetramolecular [(H2Sq)(HSq)2(Sq)]4− anion, respectively. Preliminary second harmonic generation measurements are also performed.