




Supporting information
![]() | Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536809007247/at2732sup1.cif |
![]() | Structure factor file (CIF format) https://doi.org/10.1107/S1600536809007247/at2732Isup2.hkl |
CCDC reference: 726364
Key indicators
- Single-crystal X-ray study
- T = 100 K
- Mean
(C-C) = 0.001 Å
- R factor = 0.034
- wR factor = 0.096
- Data-to-parameter ratio = 15.5
checkCIF/PLATON results
No syntax errors found
Alert level B PLAT432_ALERT_2_B Short Inter X...Y Contact O2 .. C6 .. 2.91 Ang.
Alert level C Value of measurement temperature given = 100.000 Value of melting point given = 0.000 SHFSU01_ALERT_2_C Test not performed. _refine_ls_shift/su_max and _refine_ls_shift/esd_max not present. Absolute value of the parameter shift to su ratio given 0.001 PLAT250_ALERT_2_C Large U3/U1 Ratio for Average U(i,j) Tensor .... 2.17 PLAT432_ALERT_2_C Short Inter X...Y Contact C6 .. C6 .. 3.18 Ang.
Alert level G PLAT720_ALERT_4_G Number of Unusual/Non-Standard Labels .......... 5
0 ALERT level A = In general: serious problem 1 ALERT level B = Potentially serious problem 3 ALERT level C = Check and explain 1 ALERT level G = General alerts; check 0 ALERT type 1 CIF construction/syntax error, inconsistent or missing data 4 ALERT type 2 Indicator that the structure model may be wrong or deficient 0 ALERT type 3 Indicator that the structure quality may be low 1 ALERT type 4 Improvement, methodology, query or suggestion 0 ALERT type 5 Informative message, check
Equimolar quantities of 4-aminopyridine (0.094 g, 1 mmol) and oxalic acid (0.090 g, 1 mmol) were dissolved in 25 ml water. The solution was refluxed at 323 K for 12 h. Colourless crystals were harvested after two months of solvent evaporation.
All the hydrogen atoms were located from the Fourier map and were allowed to refine freely.
Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
2C5H7N2+·2C2HO4−·H2O | F(000) = 808 |
Mr = 386.32 | Dx = 1.503 Mg m−3 |
Monoclinic, C2/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -C 2yc | Cell parameters from 7009 reflections |
a = 15.6429 (6) Å | θ = 2.7–38.8° |
b = 5.6929 (2) Å | µ = 0.13 mm−1 |
c = 19.9091 (7) Å | T = 100 K |
β = 105.617 (2)° | Plate, colourless |
V = 1707.52 (11) Å3 | 0.49 × 0.34 × 0.11 mm |
Z = 4 |
Bruker SMART APEXII CCD area-detector diffractometer | 2467 independent reflections |
Radiation source: fine-focus sealed tube | 2159 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.027 |
ϕ and ω scans | θmax = 30.0°, θmin = 2.1° |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | h = −22→21 |
Tmin = 0.906, Tmax = 0.986 | k = −7→7 |
12438 measured reflections | l = −27→28 |
Refinement on F2 | Primary atom site location: structure-invariant direct methods |
Least-squares matrix: full | Secondary atom site location: difference Fourier map |
R[F2 > 2σ(F2)] = 0.034 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.096 | All H-atom parameters refined |
S = 1.03 | w = 1/[σ2(Fo2) + (0.0564P)2 + 0.8323P] where P = (Fo2 + 2Fc2)/3 |
2467 reflections | (Δ/σ)max < 0.001 |
159 parameters | Δρmax = 0.35 e Å−3 |
0 restraints | Δρmin = −0.24 e Å−3 |
2C5H7N2+·2C2HO4−·H2O | V = 1707.52 (11) Å3 |
Mr = 386.32 | Z = 4 |
Monoclinic, C2/c | Mo Kα radiation |
a = 15.6429 (6) Å | µ = 0.13 mm−1 |
b = 5.6929 (2) Å | T = 100 K |
c = 19.9091 (7) Å | 0.49 × 0.34 × 0.11 mm |
β = 105.617 (2)° |
Bruker SMART APEXII CCD area-detector diffractometer | 2467 independent reflections |
Absorption correction: multi-scan (SADABS; Bruker, 2005) | 2159 reflections with I > 2σ(I) |
Tmin = 0.906, Tmax = 0.986 | Rint = 0.027 |
12438 measured reflections |
R[F2 > 2σ(F2)] = 0.034 | 0 restraints |
wR(F2) = 0.096 | All H-atom parameters refined |
S = 1.03 | Δρmax = 0.35 e Å−3 |
2467 reflections | Δρmin = −0.24 e Å−3 |
159 parameters |
Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K. |
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 | ||
O1 | 0.50462 (4) | −0.16951 (12) | 0.39445 (3) | 0.01643 (15) | |
O2 | 0.59652 (5) | −0.02380 (12) | 0.49260 (3) | 0.01700 (16) | |
O3 | 0.55682 (5) | 0.41624 (12) | 0.44228 (4) | 0.02023 (17) | |
O4 | 0.45356 (5) | 0.26647 (12) | 0.35138 (3) | 0.01903 (16) | |
N1 | 0.18206 (5) | 0.86694 (16) | 0.57611 (4) | 0.01960 (18) | |
N2 | 0.39056 (6) | 1.06075 (16) | 0.74035 (4) | 0.01829 (17) | |
C1 | 0.20886 (7) | 0.72101 (18) | 0.63132 (5) | 0.0199 (2) | |
C2 | 0.27784 (6) | 0.77998 (18) | 0.68707 (5) | 0.01844 (19) | |
C3 | 0.32276 (6) | 0.99712 (16) | 0.68737 (5) | 0.01467 (18) | |
C4 | 0.29134 (6) | 1.14587 (17) | 0.62850 (5) | 0.01667 (19) | |
C5 | 0.22175 (6) | 1.07631 (18) | 0.57489 (5) | 0.0188 (2) | |
C6 | 0.54297 (6) | 0.00122 (16) | 0.43617 (4) | 0.01357 (17) | |
C7 | 0.51411 (6) | 0.25017 (16) | 0.40655 (5) | 0.01471 (18) | |
O1W | 0.5000 | 0.46896 (19) | 0.7500 | 0.0215 (2) | |
H2W1 | 0.5135 (12) | 0.560 (3) | 0.7190 (9) | 0.048 (5)* | |
H1 | 0.1765 (9) | 0.574 (3) | 0.6285 (7) | 0.028 (3)* | |
H2 | 0.2966 (9) | 0.673 (3) | 0.7268 (8) | 0.029 (4)* | |
H4 | 0.3195 (9) | 1.295 (3) | 0.6250 (7) | 0.023 (3)* | |
H5 | 0.1983 (9) | 1.169 (2) | 0.5344 (7) | 0.021 (3)* | |
H1N2 | 0.4086 (10) | 0.968 (3) | 0.7766 (8) | 0.028 (4)* | |
H2N2 | 0.4168 (9) | 1.197 (3) | 0.7367 (7) | 0.025 (3)* | |
H1N1 | 0.1413 (11) | 0.823 (3) | 0.5397 (9) | 0.038 (4)* | |
H1O1 | 0.5253 (12) | −0.327 (4) | 0.4140 (9) | 0.054 (5)* |
U11 | U22 | U33 | U12 | U13 | U23 | |
O1 | 0.0207 (3) | 0.0102 (3) | 0.0151 (3) | 0.0000 (2) | −0.0007 (2) | −0.0013 (2) |
O2 | 0.0197 (3) | 0.0137 (3) | 0.0141 (3) | 0.0009 (2) | −0.0014 (3) | 0.0004 (2) |
O3 | 0.0259 (4) | 0.0109 (3) | 0.0186 (3) | −0.0014 (2) | −0.0033 (3) | −0.0011 (2) |
O4 | 0.0249 (4) | 0.0141 (3) | 0.0136 (3) | 0.0010 (2) | −0.0027 (3) | 0.0007 (2) |
N1 | 0.0176 (4) | 0.0215 (4) | 0.0160 (4) | −0.0005 (3) | −0.0017 (3) | −0.0030 (3) |
N2 | 0.0178 (4) | 0.0182 (4) | 0.0152 (4) | −0.0017 (3) | −0.0019 (3) | 0.0011 (3) |
C1 | 0.0196 (4) | 0.0165 (5) | 0.0221 (5) | −0.0023 (3) | 0.0031 (4) | −0.0012 (3) |
C2 | 0.0192 (4) | 0.0166 (4) | 0.0176 (4) | −0.0011 (3) | 0.0017 (3) | 0.0028 (3) |
C3 | 0.0149 (4) | 0.0143 (4) | 0.0140 (4) | 0.0012 (3) | 0.0022 (3) | −0.0006 (3) |
C4 | 0.0177 (4) | 0.0143 (4) | 0.0165 (4) | 0.0008 (3) | 0.0019 (3) | 0.0017 (3) |
C5 | 0.0182 (4) | 0.0205 (5) | 0.0152 (4) | 0.0032 (3) | 0.0002 (3) | 0.0025 (3) |
C6 | 0.0158 (4) | 0.0112 (4) | 0.0133 (4) | −0.0001 (3) | 0.0032 (3) | −0.0002 (3) |
C7 | 0.0188 (4) | 0.0112 (4) | 0.0132 (4) | 0.0003 (3) | 0.0027 (3) | 0.0002 (3) |
O1W | 0.0307 (6) | 0.0146 (5) | 0.0188 (5) | 0.000 | 0.0061 (4) | 0.000 |
O1—C6 | 1.3139 (11) | C1—C2 | 1.3654 (13) |
O1—H1O1 | 1.00 (2) | C1—H1 | 0.973 (15) |
O2—C6 | 1.2155 (11) | C2—C3 | 1.4211 (13) |
O3—C7 | 1.2611 (11) | C2—H2 | 0.979 (15) |
O4—C7 | 1.2458 (11) | C3—C4 | 1.4221 (12) |
N1—C5 | 1.3471 (14) | C4—C5 | 1.3621 (13) |
N1—C1 | 1.3514 (13) | C4—H4 | 0.966 (15) |
N1—H1N1 | 0.863 (17) | C5—H5 | 0.951 (13) |
N2—C3 | 1.3291 (12) | C6—C7 | 1.5547 (13) |
N2—H1N2 | 0.877 (15) | O1W—H2W1 | 0.874 (18) |
N2—H2N2 | 0.890 (16) | ||
C6—O1—H1O1 | 111.9 (11) | N2—C3—C4 | 121.12 (9) |
C5—N1—C1 | 121.00 (8) | C2—C3—C4 | 116.98 (8) |
C5—N1—H1N1 | 118.7 (11) | C5—C4—C3 | 119.91 (9) |
C1—N1—H1N1 | 120.2 (11) | C5—C4—H4 | 118.8 (8) |
C3—N2—H1N2 | 120.1 (10) | C3—C4—H4 | 121.3 (8) |
C3—N2—H2N2 | 117.4 (9) | N1—C5—C4 | 121.21 (9) |
H1N2—N2—H2N2 | 122.5 (13) | N1—C5—H5 | 115.6 (8) |
N1—C1—C2 | 120.95 (9) | C4—C5—H5 | 123.2 (9) |
N1—C1—H1 | 116.1 (8) | O2—C6—O1 | 125.55 (8) |
C2—C1—H1 | 123.0 (8) | O2—C6—C7 | 121.00 (8) |
C1—C2—C3 | 119.93 (9) | O1—C6—C7 | 113.45 (7) |
C1—C2—H2 | 120.2 (9) | O4—C7—O3 | 127.09 (8) |
C3—C2—H2 | 119.9 (9) | O4—C7—C6 | 118.46 (8) |
N2—C3—C2 | 121.90 (9) | O3—C7—C6 | 114.44 (8) |
C5—N1—C1—C2 | −0.98 (15) | C1—N1—C5—C4 | 1.41 (15) |
N1—C1—C2—C3 | −0.29 (15) | C3—C4—C5—N1 | −0.56 (15) |
C1—C2—C3—N2 | −179.57 (9) | O2—C6—C7—O4 | −173.95 (8) |
C1—C2—C3—C4 | 1.08 (14) | O1—C6—C7—O4 | 6.47 (12) |
N2—C3—C4—C5 | 179.98 (9) | O2—C6—C7—O3 | 6.58 (13) |
C2—C3—C4—C5 | −0.67 (14) | O1—C6—C7—O3 | −173.00 (8) |
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H2W1···O4i | 0.874 (18) | 1.895 (18) | 2.7676 (9) | 175.0 (18) |
N2—H1N2···O4ii | 0.877 (15) | 1.983 (16) | 2.8556 (11) | 173.4 (14) |
N2—H2N2···O1Wiii | 0.890 (16) | 1.993 (15) | 2.8620 (12) | 164.8 (13) |
N1—H1N1···O3iv | 0.863 (17) | 2.100 (17) | 2.8645 (11) | 147.3 (15) |
N1—H1N1···O2iv | 0.863 (17) | 2.218 (17) | 2.8818 (11) | 133.6 (15) |
O1—H1O1···O3v | 1.00 (2) | 1.60 (2) | 2.5916 (10) | 177.6 (18) |
C5—H5···O2vi | 0.951 (13) | 2.361 (14) | 3.1585 (12) | 141.2 (11) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x, −y+1, z+1/2; (iii) x, y+1, z; (iv) x−1/2, y+1/2, z; (v) x, y−1, z; (vi) x−1/2, y+3/2, z. |
Experimental details
Crystal data | |
Chemical formula | 2C5H7N2+·2C2HO4−·H2O |
Mr | 386.32 |
Crystal system, space group | Monoclinic, C2/c |
Temperature (K) | 100 |
a, b, c (Å) | 15.6429 (6), 5.6929 (2), 19.9091 (7) |
β (°) | 105.617 (2) |
V (Å3) | 1707.52 (11) |
Z | 4 |
Radiation type | Mo Kα |
µ (mm−1) | 0.13 |
Crystal size (mm) | 0.49 × 0.34 × 0.11 |
Data collection | |
Diffractometer | Bruker SMART APEXII CCD area-detector diffractometer |
Absorption correction | Multi-scan (SADABS; Bruker, 2005) |
Tmin, Tmax | 0.906, 0.986 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 12438, 2467, 2159 |
Rint | 0.027 |
(sin θ/λ)max (Å−1) | 0.703 |
Refinement | |
R[F2 > 2σ(F2)], wR(F2), S | 0.034, 0.096, 1.03 |
No. of reflections | 2467 |
No. of parameters | 159 |
H-atom treatment | All H-atom parameters refined |
Δρmax, Δρmin (e Å−3) | 0.35, −0.24 |
Computer programs: APEX2 (Bruker, 2005), SAINT (Bruker, 2005), SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).
D—H···A | D—H | H···A | D···A | D—H···A |
O1W—H2W1···O4i | 0.874 (18) | 1.895 (18) | 2.7676 (9) | 175.0 (18) |
N2—H1N2···O4ii | 0.877 (15) | 1.983 (16) | 2.8556 (11) | 173.4 (14) |
N2—H2N2···O1Wiii | 0.890 (16) | 1.993 (15) | 2.8620 (12) | 164.8 (13) |
N1—H1N1···O3iv | 0.863 (17) | 2.100 (17) | 2.8645 (11) | 147.3 (15) |
N1—H1N1···O2iv | 0.863 (17) | 2.218 (17) | 2.8818 (11) | 133.6 (15) |
O1—H1O1···O3v | 1.00 (2) | 1.60 (2) | 2.5916 (10) | 177.6 (18) |
C5—H5···O2vi | 0.951 (13) | 2.361 (14) | 3.1585 (12) | 141.2 (11) |
Symmetry codes: (i) −x+1, −y+1, −z+1; (ii) x, −y+1, z+1/2; (iii) x, y+1, z; (iv) x−1/2, y+1/2, z; (v) x, y−1, z; (vi) x−1/2, y+3/2, z. |
4-Aminopyridine (Fampridine) is used clinically in Lambert-Eaton myasthenic syndrome and multiple sclerosis because by blocking potassium channels it prolongs action potentials thereby increasing transmitter release at the neuromuscular junction (Judge & Bever, 2006; Schwid et al., 1997; Strupp et al., 2004). The structure of 4-aminopyridine has already been reported (Chao & Schempp, 1977). Redetermination of the structure of 4-aminopyridine has been reported (Anderson et al., 2005). The crystal structure of oxalic acid monohydrate has been reported (Derissen & Smith, 1974). As an extension of our systematic study of the hydrogen bonding patterns of 4-aminopyridine with carboxylic acids, the title compound (I) has been synthesized and the crystal structure determined.
The asymmetric unit of (I) (Fig. 1) contains one molecule of 4-aminopyridine cation, one molecule of oxalate anion and half-a-molecule of water. A proton transfer from the carboxyl group of oxalic acid to atom N1 of 4-aminopyridine resulted in the formation of salts. This protonation lead to the widening of C1–N1–C5 angle of the pyridine ring to 121.0 (8)°, compared to 115.25 (13)° in the unprotonated 4-aminopyridine (Anderson et al., 2005). This type of protonation is observed in various 4-aminopyridine acid complexes (Bhattacharya et al., 1994; Karle et al., 2003). The bond lengths and bond angles of the 4-aminopyridine are comparable to the values reported earlier for 4-aminopyridine (Chao & Schempp, 1977; Anderson et al., 2005). The 4-aminopyridine ring is essentially planar with the maximum deviation from planarity being 0.0075 (9)Å for atom N1. The bond lengths and bond angles of the oxalate are comparable to the values reported for oxalic acid (Derissen & Smith, 1974).
The crystal packing is consolidated by intermolecular O—H···O, N—H···O and C—H···O hydrogen bonds (Table 1). Intermolecular short contacts of O—O = 2.5916 (10)i to 2.7074 (10)Å and N—O = 2.8557 (11)ii to 2.8646 (11)iiiÅ are observed [symmetry codes: (i) x,-1 + y,z; (ii) x,1 - y,1/2 + z; (iii) -1/2 + x,1/2 + y,z]. The molecules are linked into a 3-D network (Fig. 2).