The Pseudo Symmetric Crystal Structure of 1,4-Diazabicyclo[2<middle dot>2<middle dot>2]octane-1,4-diium bis(5-hydroxy-2,4-dinitrophenolate)

Reaction of 4,6-dinitroresorcinol (1) and the nitrogen base 1,4-diazabicyclo[2<middle dot>2<middle dot>2]octane (2) affords the 1:2 salt and proton-transfer compound 1,4-diazabicyclo[2<middle dot>2<middle dot>2]octane-1,4-diium bis(5-hydroxy-2,4-dinitrophenolate) (3). Compound 3 crystallizes in the triclinic crystal system (space group P-1) with a = 8.3242(5) & Aring;, b = 11.9915(7) & Aring;, c = 12.4595(7) & Aring;, alpha = 116.282(2)degrees, beta = 100.576(3)degrees, gamma = 101.051(2)degrees, 1042.30(11) & Aring;(3) and Z = 2. The dication 2-H22+ forms charge assisted donating bifurcated N+-H & sdot;& sdot;& sdot;O- hydrogen bonds to the phenolate moieties of two monoanions of 1. The latter exhibit an intramolecular O-H & sdot;& sdot;& sdot;O hydrogen bond between the hydroxy group and the nitro group in ortho position. The crystal structure of 3 features pseudo B-centering of the lattice, which relates the two crystallographically distinct monoanions of 1 by a pseudo translation. The possible B-centring is broken by the ethylene groups of 2-H-2(2+), which are related in neighbouring molecules by centres of symmetry.