New structural motif of hydrogensquarate anions in the presence of dl-Serinium cation. Spectral and structural elucidation

Abstract

A new crystalline complex of dl-serine and squaric acid (H2Sq) in stoichiometric ratio 1:1 (dl-Ser·HSq) was synthesized, isolated and structurally characterized by single crystal X-ray diffraction. The compound crystallizes in the monoclinic space group P21/n and its structure consists of a 3D supramolecular network of hydrogensquarate anions and serinium cations directed by intermolecular hydrogen bonding interactions. The 3D network is formed by hydrogen bonds with participation of CO–OH, hydrogensquarate ion and NH3+ group, (Sq) CO…OC (OH) (2.525 Å), –NH3+…OC (Sq) (2.915, 2.985 and 3.016 Å), hydroxyl group CH2–OH…OC (Sq) (2.739 Å), O…H–N+ (3.016 Å) and (C–OHA…OC (Sq) (3.242), respectively. The structural information shows a new structural motif, a non-classic α-chain of the hydrogensquarate anions with dihedral angle between neighbouring HSq− anions 43.66°. The Raman and infrared spectra of the new crystal were measured in the 4000–50 cm−1and 4000–400 cm−1 region frequency range respectively. The assignment of bands in infrared and Raman spectra of the crystal was performed on the basis of DFT (B3LYP) calculations, X-ray structural results and by the comparison with literature data.