Received 10 September 2012
In the title molecular salt, C5H9N2+·C7H3N2O7-, the roughly planar anion (r.m.s. deviation = 0.120 Å) has been deprotonated at the phenol group. An intramolecular O-HO hydrogen bond in the anion generates an S(6) ring. In the crystal, the components are linked by cation-to-anion N-HO and N-H(O,O) hydrogen bonds, generating  double chains. Weak C-HO interactions consolidate the packing.
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL.
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: HB6958 ).
We gratefully acknowledge the financial support of the Education Office Foundation of Zhejiang Province (project No. Y201017321) and the innovation project of Zhejiang A & F University.
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