organic papers o1524 Odabas ¸og ˘lu and Bu ¨ yu ¨ kgu ¨ ngo ¨r  C 6 H 18 N 2 O 2 2+ C 2 O 4 2 doi:10.1107/S1600536806009822 Acta Cryst. (2006). E62, o1524–o1525 Acta Crystallographica Section E Structure Reports Online ISSN 1600-5368 3,6-Dioxaoctane-1,8-diammonium oxalate Mustafa Odabas ¸og ˘lu a * and Orhan Bu ¨yu ¨kgu ¨ngo ¨r b a Department of Chemistry, Faculty of Arts & Science, Ondokuz Mayıs University, TR-55139 Kurupelit Samsun, Turkey, and b Department of Physics, Faculty of Arts & Science, Ondokuz Mayıs University, TR-55139 Kurupelit Samsun, Turkey Correspondence e-mail: muodabas@omu.edu.tr Key indicators Single-crystal X-ray study T = 100 K Mean (C–C) = 0.002 A ˚ R factor = 0.031 wR factor = 0.076 Data-to-parameter ratio = 12.3 For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e. Received 21 February 2006 Accepted 16 March 2006 # 2006 International Union of Crystallography All rights reserved The title compound, C 6 H 18 N 2 O 2 2+ C 2 O 4 2 , crystallizes with one half-cation and one half-anion in the asymmetric unit. It contains cyclic N—HO hydrogen-bonded rings involving 3,6-dioxaoctane-1,8-diammonium and oxalate ions, forming a three-dimensional network. Comment Analysis of intermolecular interactions in crystalline systems is very important in supramolecular chemistry (Braga et al., 2002). These interactions influence the crystal packing and can provide insight into the collective properties of materials as well as leading to the design of new crystals with specific physical and chemical properties (Lam & Mak, 2000). We have been interested in supramolecular hydrogen-bonded systems formed by organic amines and carboxylic acids (Odabas ¸og ˘lu, Bu ¨ yu ¨ kgu ¨ ngo ¨ r & Lo ¨ nnecke, 2003; Odabas ¸og ˘lu, Bu ¨ yu ¨ kgu ¨ ngo ¨r, Turgut et al.,2003; Odabas ¸og ˘lu & Bu ¨ yu ¨ kgu ¨ ngo ¨ r, 200a,b). The structure presented here, (I), is another example of this type of supramolecular assembly (Fig. 1). In (I), the 3,6-dioxaoctane-1,8-diammonium ions are linked to the oxalate ions through N—HO hydrogen bonds, resulting in the formation of spirocyclic R 2 2 (5) and R 2 2 (4) hydrogen-bonded rings (Fig. 2 and Table 2). The asymmetric unit contains half of each ion. N—HO hydrogen bonds found in amine carboxylates with essentially linear hydrogen bonds exhibit an average NO bond distance of 2.811 A ˚ and an average N—HO angle of 158.2  (Vaidhyanathan et al., 2002). Compound (I) has a slightly longer NO average bond distance of 2.829 (12) A ˚ and a slightly smaller N—HO average bond angle of 149.9 (12)  . In (I), the C1—N1 bond exhibits a normal Csp 3 —Nsp 3 single-bond length (Vaidhyanathan et al., 2002; Odabas ¸og ˘lu & Bu ¨ yu ¨ kgu ¨ ngo ¨ r, 2006), while the C1—C2 single bond is shorter than normal. This shortening can be attributed to the positive inductive effect of the O and N atoms. Experimental The title compound was prepared by mixing 2-[2-(2-amino- ethoxy)ethoxy]ethanamine and oxalic acid in a 1:1 molar ratio in water at 353 K. Crystals of (I) were obtained by slow evaporation of the solvent (m.p. 494–495 K).