Supporting information
Crystallographic Information File (CIF) https://doi.org/10.1107/S010827010402342X/na1676sup1.cif | |
Structure factor file (CIF format) https://doi.org/10.1107/S010827010402342X/na1676Isup2.hkl |
CCDC reference: 256991
CrO3 (0.2 mol) and DABCO (0.1 mol) were dissolved separately in adequate H2O (1.5 and 1.2 mol), and the two solutions were then mixed with cautious stirring. Crystals of the title salt were formed in the final solution by slow evaporation of water at 298 K for a week.
The H atoms of the NH groups were located in difference Fourier maps and refined with the N—H distance restrained. All remaining H atoms were placed in calculated positions and allowed to ride on their parent atoms, with C—H = 0.97 Å and with Uiso(H) = 1.2Ueq(C).
Data collection: SMART (Bruker, 2000); cell refinement: SMART; data reduction: SAINT (Bruker, 2000); program(s) used to solve structure: SHELXTL (Bruker, 2000); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL.
(C6H14N2)[Cr2O7] | F(000) = 1344 |
Mr = 330.19 | Dx = 1.965 Mg m−3 |
Orthorhombic, Pbca | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P2ac2ab | Cell parameters from 5621 reflections |
a = 9.0727 (4) Å | θ = 2.9–25.2° |
b = 12.9327 (5) Å | µ = 1.97 mm−1 |
c = 19.0201 (8) Å | T = 298 K |
V = 2231.71 (16) Å3 | Block, red |
Z = 8 | 0.34 × 0.27 × 0.23 mm |
Bruker SMART CCD area-detector diffractometer | 2005 independent reflections |
Radiation source: fine-focus sealed tube | 1889 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.026 |
ϕ and ω scans | θmax = 25.2°, θmin = 2.1° |
Absorption correction: integration (SADABS; Bruker, 2000) | h = −10→10 |
Tmin = 0.554, Tmax = 0.660 | k = −14→15 |
10994 measured reflections | l = −19→22 |
Refinement on F2 | Secondary atom site location: difference Fourier map |
Least-squares matrix: full | Hydrogen site location: inferred from neighbouring sites |
R[F2 > 2σ(F2)] = 0.029 | H atoms treated by a mixture of independent and constrained refinement |
wR(F2) = 0.081 | w = 1/[σ2(Fo2) + (0.0435P)2 + 2.1654P] where P = (Fo2 + 2Fc2)/3 |
S = 1.09 | (Δ/σ)max < 0.001 |
2005 reflections | Δρmax = 0.36 e Å−3 |
163 parameters | Δρmin = −0.28 e Å−3 |
2 restraints | Extinction correction: SHELXTL (Bruker, 2000), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4 |
Primary atom site location: structure-invariant direct methods | Extinction coefficient: 0.0075 (5) |
(C6H14N2)[Cr2O7] | V = 2231.71 (16) Å3 |
Mr = 330.19 | Z = 8 |
Orthorhombic, Pbca | Mo Kα radiation |
a = 9.0727 (4) Å | µ = 1.97 mm−1 |
b = 12.9327 (5) Å | T = 298 K |
c = 19.0201 (8) Å | 0.34 × 0.27 × 0.23 mm |
Bruker SMART CCD area-detector diffractometer | 2005 independent reflections |
Absorption correction: integration (SADABS; Bruker, 2000) | 1889 reflections with I > 2σ(I) |
Tmin = 0.554, Tmax = 0.660 | Rint = 0.026 |
10994 measured reflections |
R[F2 > 2σ(F2)] = 0.029 | 2 restraints |
wR(F2) = 0.081 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.09 | Δρmax = 0.36 e Å−3 |
2005 reflections | Δρmin = −0.28 e Å−3 |
163 parameters |
Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. |
Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger. |
x | y | z | Uiso*/Ueq | ||
H2 | 0.257 (3) | 0.590 (2) | 0.4315 (15) | 0.045 (9)* | |
H1 | 0.016 (3) | 0.8291 (18) | 0.3269 (14) | 0.039 (8)* | |
Cr1 | 0.14305 (4) | 0.92266 (3) | 0.17742 (2) | 0.02208 (16) | |
Cr2 | 0.35354 (4) | 1.05206 (3) | 0.08222 (2) | 0.02211 (16) | |
O1 | 0.2633 (2) | 0.83204 (14) | 0.18856 (11) | 0.0396 (5) | |
O2 | 0.0521 (2) | 0.94089 (14) | 0.24937 (10) | 0.0383 (5) | |
O3 | 0.0291 (2) | 0.89510 (16) | 0.11518 (10) | 0.0406 (5) | |
O4 | 0.23041 (19) | 1.04206 (12) | 0.15559 (9) | 0.0267 (4) | |
O5 | 0.5154 (2) | 1.01342 (17) | 0.10452 (12) | 0.0463 (5) | |
O6 | 0.3606 (2) | 1.17191 (17) | 0.06117 (13) | 0.0489 (6) | |
O7 | 0.2893 (3) | 0.9839 (3) | 0.01921 (12) | 0.0780 (10) | |
N1 | 0.0684 (2) | 0.77568 (15) | 0.34751 (11) | 0.0239 (4) | |
N2 | 0.2060 (2) | 0.63563 (15) | 0.40841 (11) | 0.0242 (4) | |
C1 | −0.0115 (3) | 0.7470 (2) | 0.41333 (13) | 0.0283 (5) | |
H1A | −0.1149 | 0.7353 | 0.4033 | 0.034* | |
H1B | −0.0039 | 0.8025 | 0.4475 | 0.034* | |
C2 | 0.0580 (3) | 0.64893 (19) | 0.44250 (13) | 0.0278 (5) | |
H2A | 0.0692 | 0.6544 | 0.4931 | 0.033* | |
H2B | −0.0042 | 0.5898 | 0.4323 | 0.033* | |
C3 | 0.2916 (3) | 0.73390 (19) | 0.41383 (14) | 0.0288 (6) | |
H3A | 0.3931 | 0.7223 | 0.3999 | 0.035* | |
H3B | 0.2909 | 0.7587 | 0.4620 | 0.035* | |
C4 | 0.2202 (3) | 0.81354 (18) | 0.36553 (14) | 0.0270 (5) | |
H4A | 0.2144 | 0.8800 | 0.3890 | 0.032* | |
H4B | 0.2784 | 0.8217 | 0.3231 | 0.032* | |
C5 | 0.0776 (3) | 0.68334 (19) | 0.30018 (13) | 0.0290 (6) | |
H5A | 0.1110 | 0.7040 | 0.2538 | 0.035* | |
H5B | −0.0186 | 0.6514 | 0.2956 | 0.035* | |
C6 | 0.1870 (3) | 0.6069 (2) | 0.33281 (14) | 0.0303 (6) | |
H6A | 0.1495 | 0.5369 | 0.3290 | 0.036* | |
H6B | 0.2808 | 0.6105 | 0.3085 | 0.036* |
U11 | U22 | U33 | U12 | U13 | U23 | |
Cr1 | 0.0227 (2) | 0.0211 (2) | 0.0225 (2) | 0.00086 (14) | 0.00592 (15) | 0.00310 (15) |
Cr2 | 0.0207 (2) | 0.0244 (2) | 0.0212 (2) | −0.00480 (14) | 0.00231 (15) | −0.00068 (15) |
O1 | 0.0381 (11) | 0.0329 (10) | 0.0476 (11) | 0.0124 (9) | 0.0126 (9) | 0.0072 (8) |
O2 | 0.0438 (12) | 0.0384 (10) | 0.0329 (10) | 0.0126 (9) | 0.0174 (9) | 0.0112 (8) |
O3 | 0.0372 (11) | 0.0451 (11) | 0.0396 (11) | −0.0148 (9) | −0.0025 (9) | 0.0012 (9) |
O4 | 0.0316 (10) | 0.0227 (8) | 0.0258 (9) | −0.0031 (7) | 0.0068 (7) | −0.0019 (7) |
O5 | 0.0296 (11) | 0.0532 (13) | 0.0560 (13) | 0.0111 (9) | 0.0076 (10) | 0.0155 (11) |
O6 | 0.0433 (13) | 0.0390 (12) | 0.0645 (15) | 0.0057 (9) | 0.0153 (10) | 0.0225 (11) |
O7 | 0.0651 (17) | 0.125 (2) | 0.0438 (13) | −0.0595 (17) | 0.0214 (12) | −0.0443 (15) |
N1 | 0.0215 (10) | 0.0227 (10) | 0.0275 (10) | 0.0022 (8) | −0.0039 (8) | 0.0071 (8) |
N2 | 0.0227 (11) | 0.0197 (10) | 0.0300 (11) | 0.0036 (8) | −0.0062 (8) | 0.0050 (8) |
C1 | 0.0202 (12) | 0.0346 (13) | 0.0299 (13) | 0.0041 (10) | 0.0043 (10) | 0.0043 (11) |
C2 | 0.0273 (13) | 0.0321 (13) | 0.0241 (12) | −0.0029 (10) | 0.0006 (10) | 0.0085 (10) |
C3 | 0.0198 (13) | 0.0284 (13) | 0.0382 (14) | −0.0028 (10) | −0.0088 (10) | −0.0002 (11) |
C4 | 0.0229 (12) | 0.0221 (12) | 0.0361 (14) | −0.0046 (9) | −0.0014 (11) | 0.0030 (10) |
C5 | 0.0339 (14) | 0.0308 (13) | 0.0222 (12) | −0.0060 (11) | −0.0056 (10) | 0.0017 (10) |
C6 | 0.0321 (14) | 0.0260 (12) | 0.0328 (14) | 0.0021 (11) | 0.0006 (11) | −0.0039 (11) |
Cr1—O3 | 1.612 (2) | C1—C2 | 1.521 (3) |
Cr1—O2 | 1.6153 (18) | C1—H1A | 0.9700 |
Cr1—O1 | 1.6153 (18) | C1—H1B | 0.9700 |
Cr1—O4 | 1.7847 (16) | C2—H2A | 0.9700 |
Cr2—O7 | 1.598 (2) | C2—H2B | 0.9700 |
Cr2—O6 | 1.602 (2) | C3—C4 | 1.524 (3) |
Cr2—O5 | 1.608 (2) | C3—H3A | 0.9700 |
Cr2—O4 | 1.7921 (17) | C3—H3B | 0.9700 |
N1—C1 | 1.493 (3) | C4—H4A | 0.9700 |
N1—C5 | 1.498 (3) | C4—H4B | 0.9700 |
N1—C4 | 1.502 (3) | C5—C6 | 1.532 (4) |
N1—H1 | 0.926 (17) | C5—H5A | 0.9700 |
N2—C3 | 1.493 (3) | C5—H5B | 0.9700 |
N2—C6 | 1.495 (3) | C6—H6A | 0.9700 |
N2—C2 | 1.501 (3) | C6—H6B | 0.9700 |
N2—H2 | 0.867 (18) | ||
O3—Cr1—O2 | 109.08 (11) | N2—C2—C1 | 107.98 (18) |
O3—Cr1—O1 | 111.68 (11) | N2—C2—H2A | 110.1 |
O2—Cr1—O1 | 109.87 (10) | C1—C2—H2A | 110.1 |
O3—Cr1—O4 | 107.78 (9) | N2—C2—H2B | 110.1 |
O2—Cr1—O4 | 107.32 (9) | C1—C2—H2B | 110.1 |
O1—Cr1—O4 | 110.99 (9) | H2A—C2—H2B | 108.4 |
O7—Cr2—O6 | 111.16 (16) | N2—C3—C4 | 108.23 (18) |
O7—Cr2—O5 | 111.05 (15) | N2—C3—H3A | 110.1 |
O6—Cr2—O5 | 109.28 (11) | C4—C3—H3A | 110.1 |
O7—Cr2—O4 | 108.46 (10) | N2—C3—H3B | 110.1 |
O6—Cr2—O4 | 106.82 (10) | C4—C3—H3B | 110.1 |
O5—Cr2—O4 | 109.97 (10) | H3A—C3—H3B | 108.4 |
Cr1—O4—Cr2 | 121.36 (9) | N1—C4—C3 | 107.86 (18) |
C1—N1—C5 | 109.44 (19) | N1—C4—H4A | 110.1 |
C1—N1—C4 | 109.56 (19) | C3—C4—H4A | 110.1 |
C5—N1—C4 | 110.23 (19) | N1—C4—H4B | 110.1 |
C1—N1—H1 | 107.0 (19) | C3—C4—H4B | 110.1 |
C5—N1—H1 | 111.7 (18) | H4A—C4—H4B | 108.4 |
C4—N1—H1 | 108.9 (19) | N1—C5—C6 | 107.90 (19) |
C3—N2—C6 | 109.75 (19) | N1—C5—H5A | 110.1 |
C3—N2—C2 | 109.75 (18) | C6—C5—H5A | 110.1 |
C6—N2—C2 | 109.93 (19) | N1—C5—H5B | 110.1 |
C3—N2—H2 | 105 (2) | C6—C5—H5B | 110.1 |
C6—N2—H2 | 112 (2) | H5A—C5—H5B | 108.4 |
C2—N2—H2 | 110 (2) | N2—C6—C5 | 107.67 (19) |
N1—C1—C2 | 108.18 (19) | N2—C6—H6A | 110.2 |
N1—C1—H1A | 110.1 | C5—C6—H6A | 110.2 |
C2—C1—H1A | 110.1 | N2—C6—H6B | 110.2 |
N1—C1—H1B | 110.1 | C5—C6—H6B | 110.2 |
C2—C1—H1B | 110.1 | H6A—C6—H6B | 108.5 |
H1A—C1—H1B | 108.4 | ||
O3—Cr1—O4—Cr2 | −67.22 (14) | C6—N2—C3—C4 | 50.7 (3) |
O2—Cr1—O4—Cr2 | 175.43 (11) | C2—N2—C3—C4 | −70.2 (2) |
O1—Cr1—O4—Cr2 | 55.37 (14) | C1—N1—C4—C3 | 50.5 (3) |
O7—Cr2—O4—Cr1 | 38.95 (18) | C5—N1—C4—C3 | −69.9 (2) |
O6—Cr2—O4—Cr1 | 158.86 (13) | N2—C3—C4—N1 | 16.6 (3) |
O5—Cr2—O4—Cr1 | −82.67 (14) | C1—N1—C5—C6 | −71.3 (2) |
C5—N1—C1—C2 | 50.3 (3) | C4—N1—C5—C6 | 49.3 (2) |
C4—N1—C1—C2 | −70.7 (2) | C3—N2—C6—C5 | −71.3 (2) |
C3—N2—C2—C1 | 50.2 (3) | C2—N2—C6—C5 | 49.5 (2) |
C6—N2—C2—C1 | −70.6 (2) | N1—C5—C6—N2 | 17.8 (3) |
N1—C1—C2—N2 | 17.0 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2 | 0.93 (2) | 2.09 (2) | 2.841 (3) | 137 |
N1—H1···O1i | 0.93 (2) | 2.31 (3) | 2.943 (3) | 125 |
N2—H2···O7ii | 0.87 (2) | 1.95 (3) | 2.720 (3) | 148 |
N2—H2···O5iii | 0.87 (2) | 2.39 (3) | 2.992 (3) | 127 |
C1—H1A···O1i | 0.97 | 2.42 | 3.023 (3) | 120 |
C1—H1A···O6iv | 0.97 | 2.47 | 3.348 (3) | 151 |
C1—H1B···O6v | 0.97 | 2.55 | 3.299 (3) | 135 |
C2—H2A···O3ii | 0.97 | 2.44 | 3.344 (3) | 156 |
C3—H3A···O3vi | 0.97 | 2.57 | 3.049 (3) | 111 |
C3—H3A···O6iii | 0.97 | 2.44 | 3.291 (3) | 146 |
C3—H3B···O6v | 0.97 | 2.50 | 3.353 (4) | 147 |
C4—H4A···O5i | 0.97 | 2.50 | 3.234 (3) | 132 |
C4—H4B···O1 | 0.97 | 2.57 | 3.397 (3) | 144 |
C5—H5A···O1 | 0.97 | 2.49 | 3.323 (3) | 144 |
C5—H5B···O4iv | 0.97 | 2.56 | 3.443 (3) | 151 |
Symmetry codes: (i) x−1/2, y, −z+1/2; (ii) x, −y+3/2, z+1/2; (iii) −x+1, y−1/2, −z+1/2; (iv) −x, y−1/2, −z+1/2; (v) −x+1/2, −y+2, z+1/2; (vi) x+1/2, y, −z+1/2. |
Experimental details
Crystal data | |
Chemical formula | (C6H14N2)[Cr2O7] |
Mr | 330.19 |
Crystal system, space group | Orthorhombic, Pbca |
Temperature (K) | 298 |
a, b, c (Å) | 9.0727 (4), 12.9327 (5), 19.0201 (8) |
V (Å3) | 2231.71 (16) |
Z | 8 |
Radiation type | Mo Kα |
µ (mm−1) | 1.97 |
Crystal size (mm) | 0.34 × 0.27 × 0.23 |
Data collection | |
Diffractometer | Bruker SMART CCD area-detector diffractometer |
Absorption correction | Integration (SADABS; Bruker, 2000) |
Tmin, Tmax | 0.554, 0.660 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 10994, 2005, 1889 |
Rint | 0.026 |
(sin θ/λ)max (Å−1) | 0.599 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.029, 0.081, 1.09 |
No. of reflections | 2005 |
No. of parameters | 163 |
No. of restraints | 2 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.36, −0.28 |
Computer programs: SMART (Bruker, 2000), SMART, SAINT (Bruker, 2000), SHELXTL (Bruker, 2000), SHELXTL.
Cr1—O3 | 1.612 (2) | N1—C5 | 1.498 (3) |
Cr1—O2 | 1.6153 (18) | N1—C4 | 1.502 (3) |
Cr1—O1 | 1.6153 (18) | N2—C3 | 1.493 (3) |
Cr1—O4 | 1.7847 (16) | N2—C6 | 1.495 (3) |
Cr2—O7 | 1.598 (2) | N2—C2 | 1.501 (3) |
Cr2—O6 | 1.602 (2) | C1—C2 | 1.521 (3) |
Cr2—O5 | 1.608 (2) | C3—C4 | 1.524 (3) |
Cr2—O4 | 1.7921 (17) | C5—C6 | 1.532 (4) |
N1—C1 | 1.493 (3) | ||
O3—Cr1—O2 | 109.08 (11) | O7—Cr2—O5 | 111.05 (15) |
O3—Cr1—O1 | 111.68 (11) | O6—Cr2—O5 | 109.28 (11) |
O2—Cr1—O1 | 109.87 (10) | O7—Cr2—O4 | 108.46 (10) |
O3—Cr1—O4 | 107.78 (9) | O6—Cr2—O4 | 106.82 (10) |
O2—Cr1—O4 | 107.32 (9) | O5—Cr2—O4 | 109.97 (10) |
O1—Cr1—O4 | 110.99 (9) | Cr1—O4—Cr2 | 121.36 (9) |
O7—Cr2—O6 | 111.16 (16) | ||
N1—C1—C2—N2 | 17.0 (3) | N1—C5—C6—N2 | 17.8 (3) |
N2—C3—C4—N1 | 16.6 (3) |
D—H···A | D—H | H···A | D···A | D—H···A |
N1—H1···O2 | 0.926 (17) | 2.09 (2) | 2.841 (3) | 137 |
N1—H1···O1i | 0.926 (17) | 2.31 (3) | 2.943 (3) | 125 |
N2—H2···O7ii | 0.867 (18) | 1.95 (3) | 2.720 (3) | 148 |
N2—H2···O5iii | 0.867 (18) | 2.39 (3) | 2.992 (3) | 127 |
C1—H1A···O1i | 0.97 | 2.42 | 3.023 (3) | 120 |
C1—H1A···O6iv | 0.97 | 2.47 | 3.348 (3) | 151 |
C1—H1B···O6v | 0.97 | 2.55 | 3.299 (3) | 135 |
C2—H2A···O3ii | 0.97 | 2.44 | 3.344 (3) | 156 |
C3—H3A···O3vi | 0.97 | 2.57 | 3.049 (3) | 111 |
C3—H3A···O6iii | 0.97 | 2.44 | 3.291 (3) | 146 |
C3—H3B···O6v | 0.97 | 2.50 | 3.353 (4) | 147 |
C4—H4A···O5i | 0.97 | 2.50 | 3.234 (3) | 132 |
C4—H4B···O1 | 0.97 | 2.57 | 3.397 (3) | 144 |
C5—H5A···O1 | 0.97 | 2.49 | 3.323 (3) | 144 |
C5—H5B···O4iv | 0.97 | 2.56 | 3.443 (3) | 151 |
Symmetry codes: (i) x−1/2, y, −z+1/2; (ii) x, −y+3/2, z+1/2; (iii) −x+1, y−1/2, −z+1/2; (iv) −x, y−1/2, −z+1/2; (v) −x+1/2, −y+2, z+1/2; (vi) x+1/2, y, −z+1/2. |
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Chromates may exist as mono-, di-, tri-, tetra- and poly-forms (Pressprich et al., 1988; Wang et al., 2003; Yim & Nam, 2004; Fouada et al., 1999). As no theory can currently predict the real state of these chromium compounds, many experimental attempts to find new chromates have been made since the turn of the century. We have now synthesized the title salt, (I), and its structure is here compared with those of other chromates. \sch
Fig. 1 shows the asymmetric unit of the counter-balanced ion pair of (I), consisting of a diprotonated diazabicyclo[2.2.2]octane (DABCO) cation and a discrete dichromate anion, linked via an N1—H1···O2 hydrogen bond (Table 2). The dichromate anion is composed of two CrO4 tetrahedra joined through a shared O atom. The bridging Cr—O bond lengths, Cr1—O4 and Cr2—O4, are longer than the terminal Cr—O bonds. The O—Cr—O angles range from 106.82 (10) to 111.68 (11)°. Therefore, the coordination geometries formed by the four O atoms around each Cr atom are distorted tetrahedra. The bond lengths and angles are in good agreement with those found in bipyridinium dichromates (Martín-Zarza et al., 1995), bis(octyltrimethylammonium) dichromate (Fossé et al., 1998) and tetramethylammonium dichromate (Fossé et al., 2001). (CrO3)n is an extreme case of a polychromate, where chains of corner-sharing CrO4 tetrahedra are extended along the whole crystal (Stephens & Cruickshank, 1970). In (I), the bridging Cr—O bond distance is obviously longer than that in (CrO3)n (1.748 Å), and the terminal Cr—O distances are comparable with those of (CrO3)n (1.599 Å).
Compound (I) demonstrates a hydrogen-bonding network of N—H···O and C—H···O interactions, which is similar to what is observed in diprotonated DABCO trichromate (Ding et al., 2004). There are bifurcated hydrogen bonds between the cations and the anions, namely N1—H1···O2 and N1—H1···O1i, and N2—H2···O7ii and N2—H2···O5iii (Table 2). With careful study, two chiral supramolecular chains of (I) are observed, which could be described in graph-set notation (Etter, 1990) as C22(11). One chain is formed via N1—H1···O2 and N2—H2···O7ii interactions and runs along the c axis (Fig. 3), and another is formed via N1—H1···O2 and N2—H2···O5iii interactions and runs along the b axis (Fig. 2). These chains are joined by a number of C—H···O interactions, of which the shortest is C1—H1A···O1i (Table 2). Hydrogen-bonded chains are formed in (I), rather than the hydrogen-bonded rings observed in diprotonated DABCO trichromate.
DABCO may assume one of several conformations, namely ordered and non-distorted, ordered and distorted, disordered and non-distorted, or disordered and distorted (Nimmo & Lucas, 1976). Disordered conformations are frequently observed, such as 1:1 DABCO-biphenol (Ferguson et al., 1998), 1:1 DABCO-perchloric acid (Katrusiak, 2000) and 1:2 DABCO-maleic acid (Sun & Jin, 2002). In (I), the diprotonated DABCO is ordered and distorted, owing to the confinement and twist of the above-mentioned hydrogen bonds. The situation is similar to that in diprotonated DABCO trichromate. In (I), the N—C—C—N torsion angles, with a mean value of 17.1 (3)°, indicate such a great distortion as to be comparable with the motif in an encapsuled diprotonated DABCO (Jin et al., 2003).