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4-Amino­pyridine (4AP) and 2,5-di­hydroxy­benzon­quinone (DHBQ) crystallize in a 2:1 ratio as a molecular salt with two mol­ecules of water, i.e. 2C5H7N2+·C6H2O42-·2H2O in space group P21/c. The 4AP mol­ecules and the DHBQ mol­ecules pack to form infinite one-dimensional hydrogen-bonded chains mediated by the water mol­ecules, which themselves act as tetrahedral centres and link the chains in three dimensions.

Supporting information

cif

Crystallographic Information File (CIF) https://doi.org/10.1107/S1600536801009011/cf6075sup1.cif
Contains datablocks global, I

hkl

Structure factor file (CIF format) https://doi.org/10.1107/S1600536801009011/cf6075Isup2.hkl
Contains datablock I

CCDC reference: 170752

Key indicators

  • Single-crystal X-ray study
  • T = 100 K
  • Mean [sigma](C-C) = 0.003 Å
  • R factor = 0.068
  • wR factor = 0.148
  • Data-to-parameter ratio = 11.8

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


Red Alert Alert Level A:
CHEM_001 Alert A _chemical_formula_sum is missing Chemical formula as sum of elements. The following tests will not be performed. CELLZ_01,CHEMS_01,CHEMW_01 CHEM_003 Alert A _chemical_formula_weight is missing Chemical formula mass (Da). The following tests will not be performed. CHEMW_01,CHEMW_02,CHEMW_03,DENSD_01 ABSMU_01 Alert A The ratio of given/expected absorption coefficient lies outside the range 0.90 <> 1.10 Calculated value of mu = 0.000 Value of mu given = 0.111 DIFMN_02 Alert A The minimum difference density is < -0.1*ZMAX*2.00 _refine_diff_density_min given = -0.377 Test value = 0.000 DIFMX_01 Alert A The maximum difference density is > 0.1*ZMAX*2.00 _refine_diff_density_max given = 0.288 Test value = 0.000
Yellow Alert Alert Level C:
ABSTM_02 Alert C The ratio of expected to reported Tmax/Tmin(RR') is < 0.90 Tmin and Tmax reported: 0.804 1.000 Tmin' and Tmax expected: 0.929 0.994 RR' = 0.860 Please check that your absorption correction is appropriate. CHEMS_02 Please check that you have entered the correct _publ_requested_category classification of your compound; FI or CI or EI for inorganic; FM or CM or EM for metal-organic; FO or CO or EO for organic. From the CIF: _publ_requested_category EO From the CIF: _chemical_formula_sum : DIFMN_03 Alert C The minimum difference density is < -0.1*ZMAX*0.75 The relevant atom site should be identified. DIFMX_02 Alert C The minimum difference density is > 0.1*ZMAX*0.75 The relevant atom site should be identified. PLAT_369 Alert C Long C(sp2)-C(sp2) Bond C(1) - C(2) = 1.54 Ang.
5 Alert Level A = Potentially serious problem
0 Alert Level B = Potential problem
5 Alert Level C = Please check

Comment top

To investigate a variety of molecular interactions in the solid state, in particular N—H···O and O—H···N hydrogen bonds, we have produced cocrystals of 2,5-dihydoxybenzoquinone (DHBQ) and 4-aminopyridine (4AP).

DHBQ is a weak organic acid structurally and chemically very similar to squaric acid. This is reflected in the crystal structures it forms; the recently reported structure of DHBQ with 4,4'-bipyridine (Cowan et al., 2001) is closely related to the squarate analogue reported by Reetz et al. (1994) and the present structure is very similar to that observed in 4AP and squarate (Karle et al., 1996).

The DHBQ molecule has become deprotonated and consequently shows partial delocalization in the present structure. The conformation is similar to that reported by Kulpe (1974) for the potassium salt and discussed by Kulpe & Dähne (1978). They describe DHBQ as two coupled trimethineoxonol (TMO, see below) connected by two long Csp2—Csp2 bonds. The long Csp2—Csp2 bond is between C1 and C2 [C1—C2 1.542 (3) Å] and is even longer than the typical Csp3—Csp3 bond length (C—C = 1.53 Å; Allen et al., 1992).

The pyridine group of the 4AP has become protonated and forms N—H···O hydrogen bonds to the DHBQ. In contrast to the squarate and 4AP system in which one strong N—H···O hydrogen bond is formed (Karle et al., 1996), a bifurcated N—H···O hydrogen bond is formed with similar N···O distances [N1···O1 2.875 (3) Å and N1···O2 2.757 (3) Å] (Fig. 1). The bifurcated N—H···O hydrogen bond is assisted by two almost equal-length weak C—H···O bonds [C11···O1 3.132 (4) Å and C11–H11–O1 115 (2)°, and C15···O2 3.177 (3) Å and C15–H15–O2 109 (2)°]. The aromatic rings of the DHBQ and the 4AP are inclined at an angle of 8.2° with respect to each other, but an imaginary torsion angle, O1···O2···C15···C11 of 0.4°, shows that most of this is a fold along an axis through O1 and O2. These C—H···O bonds are short and have large C—H···O angles compared with similar C—H···O bonds (Steiner, 1997), but they prevent rotation of the 4AP about an axis through N1 and N2 that would be allowed by the other hydrogen bonds in the chain.

The 4AP molecules pack with each other amino group to amino group. The unlikely close proximity of these two basic groups [N2···N2ii 3.511 (5) Å and H2A···H2Bii 2.52 (4) Å; symmetry code: (ii) 1 - x, -y, 1 - z] is caused by hydrogen-bond formation to the lone pairs of the water molecule oxygen (Fig. 1) (N2—H2A···O10 and N2—H2B···O10ii).

The molecules pack to form infinite hydrogen-bonded chains that propagate along the [301] direction. The chains form columns along the [103] direction. The water is an essential part of the supramolecular structure, it links the one-dimensional chains together by accepting hydrogen bonds from the amino groups of the 4AP molecules and also forms hydrogen bonds to the DHBQ molecules, which join adjacent chains together into a three-dimensional network (Fig. 2).

Experimental top

Approximately 0.5 mlof a 0.2 M solution of 4-aminopyridine in methanol was poured slowly into a narrow test tube containing approximately 0.5 ml of 0.2 M aqueous solution of 2,5-dihydroxybenzonquinone to produce a water/methanol interface. Thin red plate-like crystals suitable for X-ray analysis were produced by slow diffusion at the interface of the solutions.

Refinement top

All H atoms were found in the difference Fourier maps and were refined with isotropic displacement parameters; the C—H, N—H and O—H distances all refined to within standard ranges and there are no anomolous values of Uiso. As we are interested in the behaviour of the H atoms with respect to any hydrogen-bonded networks, it would be artificial to add any constraints to this stable and converged refinement.

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SMART; data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); software used to prepare material for publication: SHELXL97.

Figures top
[Figure 1] Fig. 1. The moieties of the title compound shown with 50% probability displacement ellipsoids. The dashed lines indicate hydrogen bonds. [Symmetry codes: (I) 4 - x, -y, 2 - z; (II) 1 - x, -y, 1 - z.]
[Figure 2] Fig. 2. Packing diagram viewed along the a axis. The dashed lines indicate hydrogen bonds. It can be seen easily how the water molecules bind the structure together.
Bis(4-aminopyridinium) 2,5-dioxidobenzoquinone dihydrate top
Crystal data top
2C5H7N2+·C6H2O42·2H2OF(000) = 384
Mr = 364.36Dx = 1.426 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 6.345 (4) ÅCell parameters from 980 reflections
b = 11.353 (8) Åθ = 5.0–23.9°
c = 11.838 (8) ŵ = 0.11 mm1
β = 95.684 (16)°T = 100 K
V = 848.5 (10) Å3Plate, red
Z = 20.65 × 0.35 × 0.05 mm
Data collection top
Bruker SMART-CCD
diffractometer
1861 independent reflections
Radiation source: fine-focus sealed tube1475 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.055
ω scansθmax = 27.1°, θmin = 2.5°
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
h = 88
Tmin = 0.804, Tmax = 1.000k = 1414
7323 measured reflectionsl = 1415
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.068Hydrogen site location: difference Fourier map
wR(F2) = 0.148All H-atom parameters refined
S = 1.66 w = 1/[σ2(Fo2) + (0.05P)2]
where P = (Fo2 + 2Fc2)/3
1861 reflections(Δ/σ)max < 0.001
158 parametersΔρmax = 0.29 e Å3
0 restraintsΔρmin = 0.38 e Å3
Crystal data top
2C5H7N2+·C6H2O42·2H2OV = 848.5 (10) Å3
Mr = 364.36Z = 2
Monoclinic, P21/cMo Kα radiation
a = 6.345 (4) ŵ = 0.11 mm1
b = 11.353 (8) ÅT = 100 K
c = 11.838 (8) Å0.65 × 0.35 × 0.05 mm
β = 95.684 (16)°
Data collection top
Bruker SMART-CCD
diffractometer
1861 independent reflections
Absorption correction: multi-scan
(SADABS; Sheldrick, 1996)
1475 reflections with I > 2σ(I)
Tmin = 0.804, Tmax = 1.000Rint = 0.055
7323 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0680 restraints
wR(F2) = 0.148All H-atom parameters refined
S = 1.66Δρmax = 0.29 e Å3
1861 reflectionsΔρmin = 0.38 e Å3
158 parameters
Special details top

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
C11.8229 (3)0.06776 (18)0.94682 (19)0.0160 (5)
O11.6626 (3)0.11905 (13)0.89569 (14)0.0200 (4)
C21.8462 (4)0.06544 (19)0.92583 (18)0.0153 (5)
O21.6999 (2)0.11425 (13)0.86112 (14)0.0186 (4)
C32.0225 (4)0.12489 (19)0.9788 (2)0.0181 (5)
H32.039 (4)0.210 (2)0.969 (2)0.017 (6)*
N11.3352 (3)0.00917 (17)0.76266 (18)0.0191 (5)
H11.475 (5)0.009 (2)0.800 (3)0.039 (9)*
C111.2239 (4)0.0928 (2)0.7516 (2)0.0207 (5)
H111.296 (4)0.161 (2)0.784 (2)0.019 (6)*
C121.0248 (4)0.09632 (18)0.69516 (19)0.0175 (5)
H120.950 (4)0.168 (2)0.689 (2)0.027 (7)*
C130.9301 (4)0.00777 (18)0.64651 (19)0.0152 (5)
N20.7376 (3)0.00589 (18)0.58957 (17)0.0197 (5)
H2A0.679 (4)0.074 (2)0.554 (2)0.022 (7)*
H2B0.659 (4)0.064 (2)0.574 (2)0.021 (7)*
C141.0523 (4)0.11252 (19)0.6605 (2)0.0172 (5)
H140.993 (4)0.178 (2)0.630 (2)0.019 (6)*
C151.2494 (4)0.1106 (2)0.7176 (2)0.0194 (5)
H151.336 (4)0.179 (3)0.733 (2)0.031 (7)*
O100.5121 (3)0.20783 (14)0.47749 (16)0.0212 (4)
H10A0.435 (5)0.261 (3)0.520 (3)0.048 (10)*
H10B0.570 (6)0.254 (3)0.426 (3)0.051 (10)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
C10.0134 (12)0.0178 (11)0.0172 (12)0.0000 (9)0.0042 (10)0.0038 (9)
O10.0178 (9)0.0188 (8)0.0227 (9)0.0013 (6)0.0020 (7)0.0004 (7)
C20.0167 (12)0.0186 (11)0.0113 (11)0.0028 (9)0.0043 (9)0.0000 (8)
O20.0156 (9)0.0187 (8)0.0209 (9)0.0024 (6)0.0013 (7)0.0013 (6)
C30.0216 (13)0.0132 (10)0.0193 (12)0.0010 (9)0.0012 (10)0.0002 (9)
N10.0121 (10)0.0259 (10)0.0188 (10)0.0004 (8)0.0008 (8)0.0028 (8)
C110.0222 (13)0.0217 (11)0.0189 (12)0.0049 (10)0.0046 (10)0.0002 (10)
C120.0197 (12)0.0133 (10)0.0195 (13)0.0007 (9)0.0027 (10)0.0012 (9)
C130.0153 (11)0.0203 (11)0.0112 (11)0.0007 (9)0.0068 (9)0.0014 (9)
N20.0185 (10)0.0200 (10)0.0196 (11)0.0005 (8)0.0035 (8)0.0009 (8)
C140.0204 (13)0.0152 (11)0.0163 (12)0.0008 (9)0.0039 (10)0.0029 (9)
C150.0203 (13)0.0200 (11)0.0183 (12)0.0048 (9)0.0039 (10)0.0014 (9)
O100.0200 (9)0.0161 (8)0.0275 (10)0.0000 (7)0.0021 (8)0.0017 (7)
Geometric parameters (Å, º) top
C1—O11.272 (3)C12—C131.420 (3)
C1—C3i1.409 (4)C12—H120.96 (3)
C1—C21.542 (3)C13—N21.337 (3)
C2—O21.271 (3)C13—C141.421 (3)
C2—C31.403 (4)N2—H2A0.94 (3)
C3—C1i1.409 (4)N2—H2B0.93 (3)
C3—H30.96 (3)C14—C151.361 (4)
N1—C111.354 (3)C14—H140.91 (3)
N1—C151.357 (3)C15—H150.94 (3)
N1—H10.93 (3)O10—H10A0.91 (4)
C11—C121.371 (4)O10—H10B0.91 (4)
C11—H110.97 (3)
O1—C1—C3i124.1 (2)C11—C12—H12118.7 (18)
O1—C1—C2117.1 (2)C13—C12—H12121.0 (18)
C3i—C1—C2118.8 (2)N2—C13—C12121.3 (2)
O2—C2—C3124.2 (2)N2—C13—C14122.3 (2)
O2—C2—C1116.7 (2)C12—C13—C14116.5 (2)
C3—C2—C1119.1 (2)C13—N2—H2A120.6 (17)
C2—C3—C1i122.1 (2)C13—N2—H2B123.4 (18)
C2—C3—H3121.4 (16)H2A—N2—H2B116 (2)
C1i—C3—H3116.5 (17)C15—C14—C13120.6 (2)
C11—N1—C15120.3 (2)C15—C14—H14121.2 (18)
C11—N1—H1119 (2)C13—C14—H14118.3 (18)
C15—N1—H1120 (2)N1—C15—C14121.2 (2)
N1—C11—C12121.1 (2)N1—C15—H15115.4 (18)
N1—C11—H11115.6 (18)C14—C15—H15123.4 (18)
C12—C11—H11123.2 (18)H10A—O10—H10B106 (3)
C11—C12—C13120.3 (2)
Symmetry code: (i) x+4, y, z+2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.95 (3)2.14 (3)2.875 (3)133 (2)
N1—H1···O20.95 (3)1.94 (3)2.757 (3)142 (2)
C11—H11···O10.96 (3)2.60 (3)3.132 (4)115 (2)
C15—H15···O20.96 (3)2.74 (3)3.177 (3)109 (2)
N2—H2A···O100.94 (3)2.02 (3)2.948 (3)172 (2)
N2—H2B···O10ii0.94 (3)2.02 (3)2.963 (3)174 (2)
O10—H10A···O1iii0.95 (4)1.83 (4)2.770 (3)168 (3)
O10—H10B···O2iv0.91 (4)1.90 (4)2.779 (3)161 (3)
Symmetry codes: (ii) x+1, y, z+1; (iii) x+2, y+1/2, z+3/2; (iv) x1, y+1/2, z1/2.

Experimental details

Crystal data
Chemical formula2C5H7N2+·C6H2O42·2H2O
Mr364.36
Crystal system, space groupMonoclinic, P21/c
Temperature (K)100
a, b, c (Å)6.345 (4), 11.353 (8), 11.838 (8)
β (°) 95.684 (16)
V3)848.5 (10)
Z2
Radiation typeMo Kα
µ (mm1)0.11
Crystal size (mm)0.65 × 0.35 × 0.05
Data collection
DiffractometerBruker SMART-CCD
diffractometer
Absorption correctionMulti-scan
(SADABS; Sheldrick, 1996)
Tmin, Tmax0.804, 1.000
No. of measured, independent and
observed [I > 2σ(I)] reflections
7323, 1861, 1475
Rint0.055
(sin θ/λ)max1)0.641
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.068, 0.148, 1.66
No. of reflections1861
No. of parameters158
H-atom treatmentAll H-atom parameters refined
Δρmax, Δρmin (e Å3)0.29, 0.38

Computer programs: SMART (Bruker, 1998), SMART, SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1990), SHELXL97 (Sheldrick, 1997), SHELXL97.

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1···O10.95 (3)2.14 (3)2.875 (3)133 (2)
N1—H1···O20.95 (3)1.94 (3)2.757 (3)142 (2)
C11—H11···O10.96 (3)2.60 (3)3.132 (4)115 (2)
C15—H15···O20.96 (3)2.74 (3)3.177 (3)109 (2)
N2—H2A···O100.94 (3)2.02 (3)2.948 (3)172 (2)
N2—H2B···O10i0.94 (3)2.02 (3)2.963 (3)174 (2)
O10—H10A···O1ii0.95 (4)1.83 (4)2.770 (3)168 (3)
O10—H10B···O2iii0.91 (4)1.90 (4)2.779 (3)161 (3)
Symmetry codes: (i) x+1, y, z+1; (ii) x+2, y+1/2, z+3/2; (iii) x1, y+1/2, z1/2.
 

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