Investigation of hydrogen-bond network in bis(glycinium) oxalate using single-crystal neutron diffraction and spectroscopic studies

Abstract

Single-crystal neutron diffraction investigation of bis(glycinium) oxalate was undertaken in order to study its hydrogen-bonding network, particularly the very short hydrogen bond between the glycinum and oxalate ions, indicated by the X-ray diffraction study. The non-existence of any phase transition in these crystals was attributed to the fact that the short hydrogen bond in bis(glycinium) oxalate is asymmetric in nature, with no hydrogen disorder. The potential energy landscape for the above-mentioned H atom was found to have a single minimum closer to the glycinium ion. IR and Raman investigations of the title complex supported the above result.

Crystal structures of amino acids: from bond lengths in glycine to metal complexes and high-pressure polymorphs

“…Neutron diffraction is sometimes used to resolve issues concerning the protonation state of a molecule or a complex, but all these amino acids unequivocally occur in the zwitterionic state in the crystal. The more recent research efforts using single crystal neutron diffraction have been motivated by the search for phase transitions in Gly suggested to be associated with anomalous electrical behaviour, [37] search for structural evidence for parity violation (giving a preference for l-over d-amino acids in nature), [38] investigation of a very short hydrogen bond in an amino acid complex (WEHZAL01), [39] verification of a putative hydrogen bond between water and Pt(II) (CCAPGC11), [40] and in conjunction with X-ray diffraction (XRD) to perform topological analysis of the electron density in order to analyse the effect of the multi-polar refinement strategy. [41] Neutron powder diffraction, still a relatively new method, has emerged as a valuable tool for investigations of phase transitions at high pressures.…”

Rapid enhancement of optical transparency on glycine phosphite crystals by shock waves

“…Six glycine polymorphs have been extensively studied under high pressure conditions. 15 Glycine forms complexes with many organic and inorganic acids, which are prominent materials for nonlinear optical (NLO), piezoelectric, and ferroelectric applications, such as glycine phosphate, 16 triglycine sulfate, 17 triglycine selenate, 18 triglycine tetrafluoroberylate, 19 diglycine nitrate, 20 glycinium maleate, 21 glycinium oxalate, 22 glycine picrate, 23 bisglycinium oxalate, 24 glycine-phthalic acid, 25 and glycine-glutaric acid. 26 Among many glycine complexes, glycine phosphite (GPI) is a representative of a hydrogenbonded ferroelectric crystal.…”