Received 13 June 2013
aChemistry Department, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland, and, Centre of New Technologies, University of Warsaw, Zwirki i Wigury 93, 02-089 Warszawa, Poland, and bChemistry Department, University of Warsaw, Pasteura 1, 02-093 Warszawa, Poland
Correspondence e-mail: firstname.lastname@example.org
A corrected and improved structure of the polymorph II of 2C3H8NO3+·C2O42-·2H2O, based on single-crystal data, is presented. The structure is refined with anisotropic displacement parameters for all non-H atoms and all H atoms are located. Due to the charged moieties, the structure is classified as a molecular salt. Intermolecular O-HO-, O-HO and N+-HO-hydrogen bonds link the components of the structure. The L-serinium cations and oxalate anions form a network of channels in  direction, filled with the water molecules of crystallization. The dihedral angle between the CO2 units of the oxalate dianion is 10.2 (3)°
Crystallization of serine with oxalic acid leads to diverse molecular salts, with some of them exhibiting polymorphism. The polymorphs I and II of 2C3H7NO3+·C2O42-·2H2O have already been described, see: Braga et al. (2013). Form II was determined by powder X-ray diffraction methods and therefore the crystal structure lacks properly located H atoms and anisotropic displacement parameters of all heavy atoms in the structure.
Data collection: CrysAlis PRO (Agilent, 2012); cell refinement: CrysAlis PRO; data reduction: CrysAlis PRO and SORTAV (Blessing, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012) and DIAMOND (Brandenburg, 1999); software used to prepare material for publication: SHELXL97.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: GK2581 ).
The authors acknowledge support from Foundation for Polish Science Team project (TEAM/2009-3/8) co-financed by European Regional Development Fund operated within Innovative Economy Operational Programme.
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Braga, D., Chelazzi, L., Ciabatti, I. & Grepioni, F. (2013). New J. Chem. 37, 97-104.
Brandenburg, K. (1999). DIAMOND. Crystal Impact GbR, Bonn, Germany.
Farrugia, L. J. (2012). J. Appl. Cryst. 45, 849-854.
Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.