supporting information


Acta Cryst. (2007). E63, o3894    [ doi:10.1107/S1600536807040834 ]

Coumarin-3-carboxylic acid: a second P21/c modification

H. A. Sparkes and J. A. K. Howard

Abstract top

A second polymorph of coumarin-3-carboxylic acid (2-oxo-2H-1-benzopyran-3-carboxylic acid), C10H6O4, is reported in the P21/c space group. The structure shows inter­molecular hydrogen bonding between the carboxyl groups on pairs of mol­ecules related by an inversion centre, as well as a number of C-H...O contacts.

Comment top

Coumarin and its derivatives have attracted much interest due to their optical (Wolff et al., 2003) and biological properties (Testa et al., 2000). The structure of coumarin-3-carboxylic acid (I) (form A) has previously been determined at 296 K by Dobson & Gerkin (1996), using crystals grown by evaporation from an ether solution. The new polymorph (form B) reported here was obtained unexpectedly during recrystallization of (I).

In form (B) (Figure 1) all bond lengths and angles fall within the expected ranges. The coumarin moiety (C1—C9/O1) in is essentially planar with an r.m.s deviation for the fitted atoms of 0.008 (2) Å, while the carboxyl group is twisted just out of this plane with a torsion angle of 1.8 (3)° (O4, C10, C8, C7).

Hydrogen bonding was observed in both forms; in form (A) an intramolecular hydrogen bond (O2···H3A) was identified with an O2···O3 distance of 2.589 (2) Å and an O2···H3A— O3 angle of 153°. The position of the carboxyl group hydrogen atom (H3A/H4A) in (B) differs from that found in form (A) and as a result the hydrogen bonding is intermolecular, involving pairs of coumarin-3-carboxylic acid molecules related by an inversion centre; the O3···O4_1 (_1 = x + 1, y, z) separation distance is 2.623 (2) Å with an O3—H3A···O4_1 angle of 167° (Fig. 2).

Although the conformation of coumarin-3-carboxylic acid in both structures is very similar, the packing is significantly different. In (A), alternate molecules are rotated with respect to each other (Fig. 3(i)) creating an angle of 60.31 (4)° between the mean planes calculated through the coumarin moiety of symmetry related fragments. Unlike the situation in (A), all of the molecules in (B) are aligned, forming parallel sheets through the structure in which the angle between the mean planes calculated through the coumarin moieties in symmetry related fragment (x, 1/2 − y, z − 1/2) in alternate sheets is 8.09 (4)° (Fig. 3(ii)).

It was noted in the initial structure report on (I) (Dobson & Gerkin, 1996) that there were a number of short attractive C—H···O interactions in form (A), and the authors postulated that these interactions accounted for the higher than expected density of the structure. Form (B) has a similar calculated density to that of (A), along with a number of short C—H···O contacts that satisfy the criteria postulated by Taylor & Kennard (1982).

Related literature top

For the initial structure described in P21/n, see: Dobson & Gerkin (1996). For additional related literature, see: Testa et al. (2000); Wolff et al. (2003); Taylor & Kennard (1982).

Experimental top

Coumarin-3-carboxylic acid was purchased from Aldrich (99%) and recrystallized by evaporation at room temperature from a solution of acetone and water.

Refinement top

Hydrogen atoms were positioned geometrically in (aromatic C—H = 0.95 Å and O—H = 0.84 Å) and refined using a riding model. The hydrogen atom isotropic displacement parameters were fixed to Uiso(H) = 1.2 times Ueq of the parent atom. The hydrogen atom of the CO2H group was modelled at 50% occupancy on both O3 and O4, as peaks were identified in the fourier map at both positions and the associated C—O bond lengths were essentially equivalent at (1.265 (2) Å (C10—O3) and 1.271 (2) Å (C10—O4)).

Computing details top

Data collection: SMART (Bruker, 1998); cell refinement: SAINT (Bruker, 1998); data reduction: SAINT (Bruker, 1998); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. Molecular structure of form (B). Ellipsoids are depicted at the 50% probability level.
[Figure 2] Fig. 2. Illustration of hydrogen bonding (dashed lines) in the two forms with ellipsoids depicted at the 50% probability level (i) form (A) (Dobson & Gerkin, 1996), (ii) form (B) [_1 = −x + 1, −y, −z]. Only one position of the CO2H hydrogen atom in form (B) is shown for clarity.
[Figure 3] Fig. 3. Comparison of the packing in (i) form (A) (Dobson & Gerkin, 1996), (ii) form (B). Hydrogen atoms are omitted for clarity.
2-oxo-2H-1-benzopyran-3-carboxylic acid top
Crystal data top
C10H6O4F(000) = 392
Mr = 190.15Dx = 1.588 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
Hall symbol: -P 2ybcCell parameters from 1039 reflections
a = 9.8733 (7) Åθ = 2.4–26.3°
b = 9.4382 (7) ŵ = 0.13 mm1
c = 9.7356 (6) ÅT = 120 K
β = 118.785 (2)°Plate, colourless
V = 795.12 (10) Å30.17 × 0.16 × 0.04 mm
Z = 4
Data collection top
Bruker SMART 6K CCD detector
diffractometer
1048 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tubeRint = 0.039
Graphite monochromatorθmax = 26.3°, θmin = 4.2°
Detector resolution: 8 pixels mm-1h = 1212
ω scansk = 1111
5128 measured reflectionsl = 1211
1604 independent reflections
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)] = 0.041Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.111H-atom parameters constrained
S = 0.99 w = 1/[σ2(Fo2) + (0.0615P)2]
where P = (Fo2 + 2Fc2)/3
1604 reflections(Δ/σ)max = 0.001
127 parametersΔρmax = 0.19 e Å3
0 restraintsΔρmin = 0.21 e Å3
Crystal data top
C10H6O4V = 795.12 (10) Å3
Mr = 190.15Z = 4
Monoclinic, P21/cMo Kα radiation
a = 9.8733 (7) ŵ = 0.13 mm1
b = 9.4382 (7) ÅT = 120 K
c = 9.7356 (6) Å0.17 × 0.16 × 0.04 mm
β = 118.785 (2)°
Data collection top
Bruker SMART 6K CCD detector
diffractometer
1048 reflections with I > 2σ(I)
5128 measured reflectionsRint = 0.039
1604 independent reflections
Refinement top
R[F2 > 2σ(F2)] = 0.0410 restraints
wR(F2) = 0.111H-atom parameters constrained
S = 0.99Δρmax = 0.19 e Å3
1604 reflectionsΔρmin = 0.21 e Å3
127 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*/UeqOcc. (<1)
O10.84754 (15)0.31858 (13)0.55156 (15)0.0262 (4)
O20.80372 (17)0.09130 (14)0.50285 (17)0.0373 (4)
O30.61410 (15)0.00992 (14)0.20082 (17)0.0310 (4)
H3A0.56330.04050.12110.037*0.50
O40.52464 (15)0.18083 (14)0.01970 (16)0.0299 (4)
H4A0.48410.11080.03930.036*0.50
C10.8303 (2)0.45875 (19)0.5069 (2)0.0240 (4)
C20.9047 (2)0.5584 (2)0.6240 (2)0.0264 (5)
H20.96480.53060.73040.032*
C30.8890 (2)0.6988 (2)0.5815 (2)0.0286 (5)
H30.93880.76870.66040.034*
C40.8017 (2)0.7415 (2)0.4254 (3)0.0298 (5)
H40.79320.83910.39860.036*
C50.7282 (2)0.6407 (2)0.3108 (3)0.0280 (5)
H50.66870.66880.20440.034*
C60.7408 (2)0.4964 (2)0.3505 (2)0.0226 (4)
C70.6668 (2)0.38576 (19)0.2395 (2)0.0237 (5)
H70.60470.40960.13210.028*
C80.6823 (2)0.2480 (2)0.2821 (2)0.0225 (5)
C90.7781 (2)0.2081 (2)0.4468 (2)0.0253 (5)
C100.6020 (2)0.1388 (2)0.1607 (2)0.0242 (5)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0305 (7)0.0232 (8)0.0180 (7)0.0008 (6)0.0062 (6)0.0007 (6)
O20.0499 (10)0.0247 (8)0.0248 (8)0.0020 (7)0.0081 (7)0.0021 (7)
O30.0339 (8)0.0240 (7)0.0257 (8)0.0016 (6)0.0068 (6)0.0017 (6)
O40.0314 (8)0.0306 (8)0.0183 (8)0.0027 (6)0.0046 (6)0.0014 (6)
C10.0239 (10)0.0230 (10)0.0238 (11)0.0005 (8)0.0103 (8)0.0006 (9)
C20.0252 (10)0.0307 (11)0.0188 (11)0.0007 (8)0.0070 (8)0.0019 (9)
C30.0285 (11)0.0284 (11)0.0265 (12)0.0040 (9)0.0113 (9)0.0067 (9)
C40.0304 (11)0.0258 (11)0.0298 (12)0.0006 (8)0.0119 (9)0.0005 (9)
C50.0278 (11)0.0279 (11)0.0237 (11)0.0003 (8)0.0086 (9)0.0003 (9)
C60.0222 (10)0.0235 (10)0.0188 (10)0.0002 (8)0.0072 (8)0.0007 (8)
C70.0228 (10)0.0282 (11)0.0166 (10)0.0018 (8)0.0065 (8)0.0007 (8)
C80.0236 (10)0.0244 (10)0.0183 (11)0.0009 (7)0.0091 (8)0.0018 (8)
C90.0273 (11)0.0243 (11)0.0205 (11)0.0010 (8)0.0083 (8)0.0036 (9)
C100.0211 (10)0.0287 (11)0.0217 (11)0.0001 (8)0.0094 (8)0.0005 (9)
Geometric parameters (Å, º) top
O1—C11.377 (2)C3—C41.398 (3)
O1—C91.387 (2)C3—H30.9500
O2—C91.202 (2)C4—C51.377 (3)
O3—C101.265 (2)C4—H40.9500
O3—H3A0.8400C5—C61.404 (3)
O4—C101.271 (2)C5—H50.9500
O4—H4A0.8400C6—C71.426 (3)
C1—C21.384 (3)C7—C81.351 (3)
C1—C61.390 (3)C7—H70.9500
C2—C31.375 (3)C8—C91.465 (3)
C2—H20.9500C8—C101.479 (3)
C1—O1—C9123.23 (15)C6—C5—H5119.8
C10—O3—H3A109.5C1—C6—C5118.37 (18)
C10—O4—H4A109.5C1—C6—C7117.81 (17)
O1—C1—C2117.19 (17)C5—C6—C7123.82 (18)
O1—C1—C6120.57 (16)C8—C7—C6122.10 (18)
C2—C1—C6122.24 (18)C8—C7—H7118.9
C3—C2—C1117.99 (19)C6—C7—H7118.9
C3—C2—H2121.0C7—C8—C9120.09 (18)
C1—C2—H2121.0C7—C8—C10119.17 (18)
C2—C3—C4121.75 (19)C9—C8—C10120.74 (17)
C2—C3—H3119.1O2—C9—O1115.75 (18)
C4—C3—H3119.1O2—C9—C8128.05 (18)
C5—C4—C3119.32 (19)O1—C9—C8116.20 (17)
C5—C4—H4120.3O3—C10—O4123.52 (18)
C3—C4—H4120.3O3—C10—C8119.23 (18)
C4—C5—C6120.3 (2)O4—C10—C8117.25 (17)
C4—C5—H5119.8
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O4i0.841.802.6258 (19)167
O4—H4A···O3i0.841.802.6258 (18)167
C2—H2···O2ii0.952.573.393 (2)146
C4—H4···O2iii0.952.573.384 (3)144
C4—H4···O3iii0.952.483.275 (3)141
C5—H5···O4iv0.952.533.419 (2)156
Symmetry codes: (i) x+1, y, z; (ii) x+2, y+1/2, z+3/2; (iii) x, y+1, z; (iv) x+1, y+1, z.

Experimental details

Crystal data
Chemical formulaC10H6O4
Mr190.15
Crystal system, space groupMonoclinic, P21/c
Temperature (K)120
a, b, c (Å)9.8733 (7), 9.4382 (7), 9.7356 (6)
β (°) 118.785 (2)
V3)795.12 (10)
Z4
Radiation typeMo Kα
µ (mm1)0.13
Crystal size (mm)0.17 × 0.16 × 0.04
Data collection
DiffractometerBruker SMART 6K CCD detector
diffractometer
Absorption correction
No. of measured, independent and
observed [I > 2σ(I)] reflections
5128, 1604, 1048
Rint0.039
(sin θ/λ)max1)0.624
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.041, 0.111, 0.99
No. of reflections1604
No. of parameters127
H-atom treatmentH-atom parameters constrained
Δρmax, Δρmin (e Å3)0.19, 0.21

Computer programs: SMART (Bruker, 1998), SAINT (Bruker, 1998), SHELXS97 (Sheldrick, 1997), SHELXL97 (Sheldrick, 1997), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
O3—H3A···O4i0.841.802.6258 (19)167.1
O4—H4A···O3i0.841.802.6258 (18)166.9
C2—H2···O2ii0.952.573.393 (2)145.7
C4—H4···O2iii0.952.573.384 (3)143.9
C4—H4···O3iii0.952.483.275 (3)141.2
C5—H5···O4iv0.952.533.419 (2)155.5
Symmetry codes: (i) x+1, y, z; (ii) x+2, y+1/2, z+3/2; (iii) x, y+1, z; (iv) x+1, y+1, z.
 
Acknowledgements top

The authors thank the EPSRC for funding.