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Crystallization of the title compound, C
8H
8N
4O
2, results in the formation of one-dimensional chains of imidazole (im) molecules linked together by strong hydrogen bonds. The O
N(im) separation and O—H(
N) distance are 2.6906 (17) and 1.74 (2) Å, respectively, and the O—H
N angle is 173 (2)°. The one-dimensional chains are weakly π stacked along the
b axis, with centroid-to-centroid separations of 3.678 (2) Å between five- and six-membered rings and 3.963 (2) Å between six-membered rings. Each molecule is arranged around an inversion center.
Supporting information
CCDC reference: 275522
Imidazole-2-carboxaldehyde (1 mmol) was added to an aqueous methanol (5 ml) solution (5:1) containing NaOH (1.5 mmol) and stirred for 1 h. The mixture was extracted three times with CH2Cl2 (5 ml) and the combined extracts were allowed to evaporate slowly in air, producing colorless single crystals.
H atoms were located in difference maps. Imidazole H atoms were refined isotropically. Positions for the hydroxy and methine H atoms were refined, while their Uiso(H) values were assigned as 1.2Ueq(parent atom).
Data collection: SMART (Bruker, 2002); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: SHELXTL (Bruker, 2001); software used to prepare material for publication: SHELXTL.
5,10-dihyhydroxy-5H,10
H-diimidazo[1,2 − a:1',2'-d]pyrazine
top
Crystal data top
C8H8N4O2 | F(000) = 200 |
Mr = 192.18 | Dx = 1.620 Mg m−3 |
Monoclinic, P21/c | Mo Kα radiation, λ = 0.71073 Å |
Hall symbol: -P 2ybc | Cell parameters from 835 reflections |
a = 6.6274 (19) Å | θ = 2.7–24.6° |
b = 3.9625 (11) Å | µ = 0.12 mm−1 |
c = 15.260 (4) Å | T = 100 K |
β = 100.615 (5)° | Block, colorless |
V = 393.89 (19) Å3 | 0.12 × 0.11 × 0.05 mm |
Z = 2 | |
Data collection top
Bruker SMART APEX CCD diffractometer | 881 independent reflections |
Radiation source: normal-focus sealed tube | 688 reflections with I > 2σ(I) |
Graphite monochromator | Rint = 0.021 |
ω scans | θmax = 27.5°, θmin = 2.7° |
Absorption correction: multi-scan SADABS; Sheldrick, (1996). | h = −8→8 |
Tmin = 0.956, Tmax = 0.989 | k = −5→5 |
3097 measured reflections | l = −19→19 |
Refinement top
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)] = 0.036 | Hydrogen site location: inferred from neighbouring sites |
wR(F2) = 0.071 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | w = 1/[σ2(Fo2) + (0.0139P)2 + 0.291P] where P = (Fo2 + 2Fc2)/3 |
881 reflections | (Δ/σ)max < 0.001 |
78 parameters | Δρmax = 0.24 e Å−3 |
0 restraints | Δρmin = −0.18 e Å−3 |
Crystal data top
C8H8N4O2 | V = 393.89 (19) Å3 |
Mr = 192.18 | Z = 2 |
Monoclinic, P21/c | Mo Kα radiation |
a = 6.6274 (19) Å | µ = 0.12 mm−1 |
b = 3.9625 (11) Å | T = 100 K |
c = 15.260 (4) Å | 0.12 × 0.11 × 0.05 mm |
β = 100.615 (5)° | |
Data collection top
Bruker SMART APEX CCD diffractometer | 881 independent reflections |
Absorption correction: multi-scan SADABS; Sheldrick, (1996). | 688 reflections with I > 2σ(I) |
Tmin = 0.956, Tmax = 0.989 | Rint = 0.021 |
3097 measured reflections | |
Refinement top
R[F2 > 2σ(F2)] = 0.036 | 0 restraints |
wR(F2) = 0.071 | H atoms treated by a mixture of independent and constrained refinement |
S = 1.08 | Δρmax = 0.24 e Å−3 |
881 reflections | Δρmin = −0.18 e Å−3 |
78 parameters | |
Special details top
Experimental. Data were collected with a Bruker SMART APEX CCD-based diffractometer using /w-scans of width 0.3 °. and 30 s duration at a crystal-to-detector distance of 4.908 cm. Intensity decay over the course of the data collection was evaluated by recollecting the first 50 frames of data at the end of the experiment. No significant decay was noted. |
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. |
Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top | x | y | z | Uiso*/Ueq | |
O1 | 0.79266 (16) | 0.3904 (3) | 0.41251 (7) | 0.0194 (3) | |
H1O | 0.913 (3) | 0.499 (5) | 0.4010 (11) | 0.023* | |
N1 | 0.51118 (18) | 0.3244 (3) | 0.57806 (8) | 0.0150 (3) | |
N2 | 0.84981 (18) | 0.3412 (3) | 0.61308 (8) | 0.0174 (3) | |
C1 | 0.6881 (2) | 0.4270 (4) | 0.55355 (10) | 0.0149 (3) | |
C2 | 0.5645 (2) | 0.1666 (4) | 0.65950 (10) | 0.0174 (3) | |
H2 | 0.463 (2) | 0.072 (4) | 0.6894 (10) | 0.016 (4)* | |
C3 | 0.7720 (2) | 0.1787 (4) | 0.68005 (10) | 0.0186 (3) | |
H3 | 0.861 (3) | 0.092 (4) | 0.7310 (11) | 0.024 (4)* | |
C4 | 0.6996 (2) | 0.5997 (4) | 0.46706 (10) | 0.0156 (3) | |
H4 | 0.784 (2) | 0.816 (4) | 0.4762 (10) | 0.019* | |
Atomic displacement parameters (Å2) top | U11 | U22 | U33 | U12 | U13 | U23 |
O1 | 0.0166 (6) | 0.0210 (6) | 0.0223 (6) | −0.0012 (5) | 0.0082 (4) | −0.0031 (5) |
N1 | 0.0140 (6) | 0.0151 (6) | 0.0159 (6) | −0.0003 (5) | 0.0027 (5) | 0.0003 (5) |
N2 | 0.0161 (6) | 0.0181 (6) | 0.0182 (6) | 0.0003 (6) | 0.0035 (5) | −0.0007 (6) |
C1 | 0.0142 (7) | 0.0126 (7) | 0.0183 (7) | −0.0005 (6) | 0.0037 (6) | −0.0038 (6) |
C2 | 0.0211 (8) | 0.0157 (7) | 0.0165 (7) | −0.0001 (7) | 0.0058 (6) | 0.0015 (7) |
C3 | 0.0201 (8) | 0.0186 (8) | 0.0169 (7) | 0.0017 (7) | 0.0026 (6) | 0.0008 (7) |
C4 | 0.0129 (7) | 0.0162 (8) | 0.0180 (7) | 0.0002 (6) | 0.0032 (6) | −0.0011 (6) |
Geometric parameters (Å, º) top
O1—C4 | 1.3967 (17) | N2—C3 | 1.3854 (19) |
O1—H1O | 0.954 (18) | C1—C4 | 1.501 (2) |
N1—C1 | 1.3568 (18) | C2—C3 | 1.353 (2) |
N1—C2 | 1.3779 (19) | C2—H2 | 0.957 (16) |
N1—C4i | 1.4701 (18) | C3—H3 | 0.948 (17) |
N2—C1 | 1.3156 (19) | C4—H4 | 1.018 (17) |
| | | |
C4—O1—H1O | 108.6 (10) | N1—C2—H2 | 121.4 (9) |
C1—N1—C2 | 107.06 (12) | C2—C3—N2 | 110.24 (14) |
C1—N1—C4i | 127.17 (12) | C2—C3—H3 | 129.0 (10) |
C2—N1—C4i | 125.39 (12) | N2—C3—H3 | 120.8 (10) |
C1—N2—C3 | 105.23 (12) | O1—C4—N1i | 109.16 (12) |
N2—C1—N1 | 111.58 (13) | O1—C4—C1 | 110.67 (12) |
N2—C1—C4 | 123.91 (13) | N1i—C4—C1 | 107.90 (11) |
N1—C1—C4 | 124.42 (12) | O1—C4—H4 | 106.8 (9) |
C3—C2—N1 | 105.89 (13) | N1i—C4—H4 | 110.1 (9) |
C3—C2—H2 | 132.7 (9) | C1—C4—H4 | 112.2 (9) |
| | | |
C3—N2—C1—N1 | −0.85 (16) | C4i—N1—C2—C3 | −173.85 (13) |
C3—N2—C1—C4 | −177.67 (13) | N1—C2—C3—N2 | 0.03 (18) |
C2—N1—C1—N2 | 0.89 (17) | C1—N2—C3—C2 | 0.49 (18) |
C4i—N1—C1—N2 | 174.05 (13) | N2—C1—C4—O1 | 64.69 (18) |
C2—N1—C1—C4 | 177.69 (13) | N1—C1—C4—O1 | −111.73 (15) |
C4i—N1—C1—C4 | −9.1 (2) | N2—C1—C4—N1i | −175.93 (14) |
C1—N1—C2—C3 | −0.53 (17) | N1—C1—C4—N1i | 7.6 (2) |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N2ii | 0.954 (18) | 1.741 (18) | 2.6906 (17) | 173.2 (16) |
Symmetry code: (ii) −x+2, −y+1, −z+1. |
Experimental details
Crystal data |
Chemical formula | C8H8N4O2 |
Mr | 192.18 |
Crystal system, space group | Monoclinic, P21/c |
Temperature (K) | 100 |
a, b, c (Å) | 6.6274 (19), 3.9625 (11), 15.260 (4) |
β (°) | 100.615 (5) |
V (Å3) | 393.89 (19) |
Z | 2 |
Radiation type | Mo Kα |
µ (mm−1) | 0.12 |
Crystal size (mm) | 0.12 × 0.11 × 0.05 |
|
Data collection |
Diffractometer | Bruker SMART APEX CCD diffractometer |
Absorption correction | Multi-scan SADABS; Sheldrick, (1996). |
Tmin, Tmax | 0.956, 0.989 |
No. of measured, independent and observed [I > 2σ(I)] reflections | 3097, 881, 688 |
Rint | 0.021 |
(sin θ/λ)max (Å−1) | 0.650 |
|
Refinement |
R[F2 > 2σ(F2)], wR(F2), S | 0.036, 0.071, 1.08 |
No. of reflections | 881 |
No. of parameters | 78 |
H-atom treatment | H atoms treated by a mixture of independent and constrained refinement |
Δρmax, Δρmin (e Å−3) | 0.24, −0.18 |
Selected geometric parameters (Å, º) topO1—C4 | 1.3967 (17) | N2—C3 | 1.3854 (19) |
O1—H1O | 0.954 (18) | C1—C4 | 1.501 (2) |
N1—C1 | 1.3568 (18) | C2—C3 | 1.353 (2) |
N1—C2 | 1.3779 (19) | C4—H4 | 1.018 (17) |
N2—C1 | 1.3156 (19) | | |
| | | |
N1i—C4—C1 | 107.90 (11) | | |
Symmetry code: (i) −x+1, −y+1, −z+1. |
Hydrogen-bond geometry (Å, º) top
D—H···A | D—H | H···A | D···A | D—H···A |
O1—H1O···N2ii | 0.954 (18) | 1.741 (18) | 2.6906 (17) | 173.2 (16) |
Symmetry code: (ii) −x+2, −y+1, −z+1. |
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Solid-state supramolecular assemblies are often stabilized by hydrogen bonding, hydrophobic and hydrophilic interactions, π–π stacking, and electrostatic interactions between ionic groups (Desiraju, 1995; MacDonald & Whitesides, 1994; Krische & Lehn, 2000). The present study expands our interest in utilizing imidazole compounds in supramolecular chemistry. We (Cheruzel et al., 2003, 2005; Mashuta et al., 2002) and others (Cromer et al., 1987) have shown that imidazole compounds readily form strong π stacks and hydrogen bonds with proton donor and/or acceptor compounds in the solid state, making these compounds excellent synthons for stabilizing supramolecular structures. The study described here illustrates our latest efforts to prepare imidazole compounds that form one-dimensional hydrogen-bonded chain structures. Compound (I) is the first fused tricyclic azafulvalene containing imidazole to be crystallographically characterized. Compound (I) has a nearly planar centrosymmetric tricyclic structure, containing fused five- and six- membered rings, which is structurally similiar to other 1-azafulvalenes (Galeazzi et al., 1993). The title compound, which was synthesized by the base-assisted cyclization of imidazole-2-carboxaldehyde, has Ci symmetry and two stereocenters.
The structure of (I) is shown in Fig. 1, and selected geometric parameters are given in Table 1. The five-membered aromatic imidazole rings are planar (the largest deviation from the mean plane of the N and C atoms is 0.0046 Å for C1). The imidazole C—C and C—N distances and C—C—N and C—N—C angles of (I) are normal and are consistent with those of other N-alkylated imidazole compounds (Mashuta et al., 2002). The six-membered ring, on the other hand, is slightly puckered, as reflected in both the torsion angles [N1—C1—C4—N1' = 7.7 (2)° and C4'—N1—C1—C4 = −9.2 (2)°] and the 0.0292 Å deviation of C4 from planarity.
Each of the stereocenters contains a hydroxy group (O1/H1O) and a methine H atom (H4) arranged in an anti conformation, which are related by inversion. The stereocenter at C4 is assigned an R configuration, while the center at C4' is assigned an S configuration. Therefore, (I) is achiral and a meso form of the compound. Each molecule of (I) is strongly hydrogen bonded and π stacked with neighboring molecules related by inversion symmetry and translation, respectively (Fig. 2). Hydroxy groups (O1/H1O and O1'/H1O') on opposing R and S stereocenters of molecules related by inversion symmetry are hydrogen bonded to respective imidazole N atoms (N2 and N2'). The O1···N2' separation and O1—H1O···N distance of 2.6909 (18) and 1.73 (2) Å, respectively, and the O1—H1O···N2' angle of 173.7 (17)°, are consistent with the formation of strong hydrogen bonds. The two pairs of O1—H1O···N hydrogen bonds link molecules together, forming ten-membered rings, and the bifunctional nature of (I) results in the formation of infinite one-dimensional hydrogen-bonded chains projected along the crystallographic a axis.
The one-dimensional chains of (I) also form slipped π stacks (Janiak, 2000), with neighboring chains related by translation along the crystallographic b axis. The closest contact between imidazole rings in a double layer is 3.516 Å, which is repeated along the b axis. The centroid-to-centroid separation between symmetry-related imidazole rings is 3.96 Å. The overall packing arrangement of the hydrogen-bonded chains and π stacks resembles a herringbone pattern.