2',6'-Di­methoxy­flavone-bromo­acetic acid (1/1)

In the title compound, C₁₇H₁₄O₄·C₂H₃BrO₂, pairs of mol­ecules are linked via a hydrogen bond involving the carbonyl group of the flavone (2-phenyl-4H-1-benzo­pyran-4-one) and the carboxyl group of bromo­acetic acid. This acid is in the antiplanar Br-C-C=O conformation.

Key indicators

• Single-crystal X-ray study
• T = 293 K
• Mean [sigma](C-C) = 0.015 Å
• R factor = 0.075
• wR factor = 0.249
• Data-to-parameter ratio = 11.5

checkCIF results

No syntax errors found

ADDSYM reports no extra symmetry


 Alert Level B:



THETM_01  Alert B The value of sine(theta_max)/wavelength is less than 0.575
          Calculated sin(theta_max)/wavelength =    0.5655


 0 Alert Level A = Potentially serious problem

 1 Alert Level B = Potential problem

 0 Alert Level C = Please check

---

S1. Comment

2',6'-Dimethoxyflavone is a synthetic flavone which gives inclusion compounds with alkyl carboxylic acids: acetic (Wallet et al., 1989), propionic (Tinant et al., 1991) which crystallize in space group P1, and chloroacetic and trichloroacetic acids (Espinosa et al., 1999) which crystallize in non-centrosymmetric space groups. We were interested in knowing whether the presence of a haloacetic acid would favour the crystallization in a non-centrosymmetric space group. The substitution of one halogen by another had been reported as not altering the existing packing of crystals (Kálmán et al., 1993; Wallet et al., 2000). The space group is of prime importance for the phenomenon of second harmonic generation. 2',6'-Dimethoxyflavone–acid complexes may provide the possibility to get acid molecules in different conformations of those given by pure acid crystals. Earlier examples are given by complexes with formic acid (Tinant et al., 1991) and 2,6-dimethoxybenzoic acid (Wallet et al., 1998). However, the control of the structure of solids via hydrogen-bonding interactions is known to be difficult (Desiraju, 1989).

The molecule structure of the title compound, (I), is shown in Fig. 1. The torsion angle O1—C2—C1'—C6' in the flavone is -66.5 (11)°. The backbone of the bromoacetic acid is almost planar, Br1—C11—C12—O122 = -175.8 (9)°. Two forms of crystal structure have been reported for bromoacetic acid (Vor der Bruck & Leiserowitz, 1975). In (I), the acid molecule shows the same conformation as in the pure acid crystals (synplanar). The difference is that the bromoacetic acid is in the anti Br—C—C═O conformation (syn in the two forms of the pure acid). In addition to the O121—H121···O4 hydrogen bond (Table 1) there is a short contact C3—H3···O122, which exists in the complexes with acetic and propionic acids (space group P1) but does not exist in the complexes with chloroacetic and trichloroacetic acids which crystallize in non-centrosymmetric space groups. Thus, a skewed non-planar arrangement of the carboxyl group to the benzopyrone moiety of flavone seems to be a driving force leading to non-centrosymmetric structure.

S2. Experimental

The synthesis of 2',6'-dimethoxyflavone has been previously reported (Wallet et al., 1989). Bromoacetic acid was from Aldrich. Crystals of (I) were obtained by slow evaporation of an ethanol solution of the stoichiometric mixture.

S3. Refinement

The positional parameters of the hydroxyl H121 atom were refined. All the other H atoms were introduced in calculated positions and constrained to ride on their bonded atom.

Computing details

Data collection: CAD-4 EXPRESS (Enraf-Nonius, 1994); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics: PLUTON93 (Spek, 1993).

Figures

Fig. 1. View of the title complex showing the labelling of the non-H atoms. Displacement ellipsoids are shown at the 50% probability level.

(I)

Crystal data

C17H14O4·C2H3BrO2	Z = 2
Mr = 421.24	F(000) = 428
Triclinic, P1	Dx = 1.536 Mg m^−3
a = 7.663 (1) Å	Mo Kα radiation, λ = 0.71073 Å
b = 9.693 (1) Å	Cell parameters from 25 reflections
c = 12.877 (1) Å	θ = 8.5–12.5°
α = 86.56 (1)°	µ = 2.29 mm^−1
β = 78.56 (1)°	T = 293 K
γ = 76.30 (2)°	Prism, pale yellow
V = 910.71 (17) Å^3	0.66 × 0.30 × 0.04 mm

Data collection

Enraf Nonius CAD4 diffractometer	1072 reflections with I > 2σ(I)
Radiation source: fine-focus sealed tube	Rint = 0.065
Graphite monochromator	θmax = 23.7°, θmin = 2.9°
non–profiled ω/2θ scans	h = 0→8
Absorption correction: ψ scan (North et al., 1968)	k = −10→10
Tmin = 0.440, Tmax = 0.913	l = −14→14
2993 measured reflections	3 standard reflections every 60 min
2760 independent reflections	intensity decay: none

Refinement

Refinement on F^2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F^2 > 2σ(F^2)] = 0.075	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.249	H atoms treated by a mixture of independent and constrained refinement
S = 0.96	w = 1/[σ^2(Fo^2) + (0.1319P)^2] where P = (Fo^2 + 2Fc^2)/3
2760 reflections	(Δ/σ)max = 0.006
240 parameters	Δρmax = 0.65 e Å^−3
0 restraints	Δρmin = −0.66 e Å^−3

Special details

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. The presence of acid and the stoichiometry in the crystal were preliminary confirmed by CH microanalysis. Calcd for C₁₉H₁₇BrO₆: C, 54.15; H, 4.03. Found: C, 54.43; H, 3.96. Number of psi-scan sets used was 4 Theta correction was applied. Averaged transmission function was used. No Fourier smoothing was applied. 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 (Ų)

	x	y	z	Uiso*/Ueq
Br1	0.9559 (3)	0.26096 (14)	0.36870 (11)	0.1161 (9)
O1	0.4596 (8)	0.8299 (6)	0.9302 (5)	0.0437 (18)
O4	0.7735 (10)	0.4825 (6)	0.7659 (5)	0.064 (2)
O2'	0.6078 (11)	0.9965 (7)	0.6770 (6)	0.067 (2)
O6'	0.0975 (10)	0.8764 (7)	0.8903 (6)	0.061 (2)
O121	0.8240 (12)	0.4156 (8)	0.5732 (6)	0.081 (3)
H121	0.844 (16)	0.439 (13)	0.652 (11)	0.122*
O122	0.6331 (11)	0.6031 (8)	0.5214 (6)	0.082 (3)
C2	0.4654 (12)	0.8183 (9)	0.8257 (7)	0.037 (2)
C3	0.5688 (12)	0.7072 (9)	0.7686 (7)	0.042 (3)
H3	0.5710	0.7073	0.6962	0.051*
C4	0.6758 (13)	0.5885 (9)	0.8162 (7)	0.040 (3)
C5	0.7635 (13)	0.4939 (10)	0.9879 (8)	0.047 (3)
H5	0.8357	0.4116	0.9546	0.057*
C6	0.7540 (15)	0.5101 (11)	1.0935 (8)	0.062 (3)
H6	0.8214	0.4399	1.1316	0.075*
C7	0.6440 (15)	0.6308 (11)	1.1439 (8)	0.066 (3)
H7	0.6353	0.6394	1.2164	0.079*
C8	0.5480 (15)	0.7375 (11)	1.0897 (8)	0.059 (3)
H8	0.4768	0.8196	1.1238	0.070*
C9	0.5596 (14)	0.7204 (9)	0.9810 (7)	0.045 (3)
C10	0.6667 (13)	0.5989 (10)	0.9299 (7)	0.043 (3)
C11	0.7951 (16)	0.4398 (12)	0.3927 (9)	0.080 (4)
H11A	0.8501	0.5085	0.3482	0.119*
H11B	0.6839	0.4370	0.3685	0.119*
C12	0.7427 (15)	0.4937 (12)	0.5016 (8)	0.055 (3)
C21	0.6876 (16)	1.0748 (13)	0.5943 (10)	0.086 (4)
H21A	0.6490	1.0598	0.5302	0.130*
H21B	0.8184	1.0446	0.5847	0.130*
H21C	0.6504	1.1739	0.6111	0.130*
C61	−0.0955 (14)	0.8867 (13)	0.9198 (9)	0.077 (4)
H61A	−0.1545	0.9781	0.9499	0.115*
H61B	−0.1179	0.8138	0.9710	0.115*
H61C	−0.1434	0.8753	0.8582	0.115*
C1'	0.3504 (14)	0.9426 (9)	0.7804 (8)	0.042 (3)
C2'	0.4210 (16)	1.0271 (10)	0.7014 (8)	0.047 (3)
C3'	0.311 (2)	1.1358 (11)	0.6567 (9)	0.067 (3)
H3'	0.3611	1.1940	0.6050	0.080*
C4'	0.131 (2)	1.1573 (11)	0.6883 (11)	0.080 (4)
H4'	0.0565	1.2289	0.6551	0.097*
C5'	0.0500 (16)	1.0789 (12)	0.7675 (10)	0.070 (3)
H5'	−0.0764	1.1005	0.7893	0.084*
C6'	0.1587 (15)	0.9663 (10)	0.8153 (8)	0.051 (3)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
Br1	0.1754 (19)	0.0781 (10)	0.0628 (9)	0.0120 (9)	0.0079 (10)	−0.0172 (7)
O1	0.047 (5)	0.048 (4)	0.031 (4)	0.005 (3)	−0.014 (3)	−0.004 (3)
O4	0.086 (6)	0.052 (4)	0.034 (4)	0.023 (4)	−0.010 (4)	−0.005 (3)
O2'	0.067 (6)	0.064 (5)	0.065 (5)	−0.019 (4)	−0.003 (4)	0.031 (4)
O6'	0.047 (5)	0.068 (5)	0.063 (5)	−0.003 (4)	−0.010 (4)	0.000 (4)
O121	0.110 (7)	0.072 (5)	0.038 (4)	0.040 (5)	−0.030 (5)	−0.009 (4)
O122	0.096 (6)	0.065 (5)	0.064 (5)	0.028 (5)	−0.021 (5)	−0.003 (4)
C2	0.039 (6)	0.038 (5)	0.038 (6)	−0.006 (5)	−0.020 (5)	0.002 (4)
C3	0.051 (7)	0.040 (5)	0.027 (5)	0.009 (5)	−0.011 (5)	0.004 (4)
C4	0.044 (6)	0.040 (5)	0.029 (5)	0.000 (5)	−0.005 (5)	0.006 (4)
C5	0.045 (7)	0.048 (5)	0.044 (7)	0.003 (5)	−0.015 (5)	0.012 (5)
C6	0.068 (8)	0.071 (7)	0.049 (7)	−0.006 (6)	−0.030 (6)	0.019 (6)
C7	0.082 (9)	0.074 (8)	0.036 (6)	0.000 (7)	−0.023 (6)	0.008 (6)
C8	0.075 (9)	0.062 (7)	0.040 (6)	−0.013 (6)	−0.014 (6)	−0.010 (5)
C9	0.055 (7)	0.045 (6)	0.031 (6)	−0.001 (5)	−0.011 (5)	0.002 (5)
C10	0.032 (6)	0.065 (6)	0.030 (5)	0.001 (5)	−0.015 (5)	0.001 (5)
C11	0.083 (9)	0.085 (8)	0.056 (7)	0.031 (7)	−0.032 (7)	−0.019 (6)
C12	0.048 (7)	0.067 (7)	0.046 (7)	−0.006 (6)	−0.012 (6)	−0.004 (6)
C21	0.072 (9)	0.093 (9)	0.096 (11)	−0.031 (8)	−0.015 (8)	0.018 (8)
C61	0.025 (7)	0.123 (10)	0.078 (9)	−0.015 (7)	0.007 (6)	−0.031 (8)
C1'	0.042 (7)	0.038 (5)	0.043 (6)	0.006 (5)	−0.015 (5)	−0.007 (5)
C2'	0.052 (8)	0.045 (6)	0.044 (6)	−0.005 (6)	−0.019 (6)	0.005 (5)
C3'	0.082 (10)	0.052 (7)	0.063 (8)	−0.001 (7)	−0.028 (8)	0.013 (6)
C4'	0.101 (12)	0.046 (7)	0.092 (10)	0.014 (8)	−0.057 (10)	0.014 (7)
C5'	0.047 (8)	0.075 (8)	0.083 (9)	0.011 (7)	−0.026 (7)	−0.008 (7)
C6'	0.051 (8)	0.050 (6)	0.050 (7)	0.005 (6)	−0.022 (6)	−0.013 (5)

Geometric parameters (Å, º)

Br1—C11	1.876 (10)	C5—C6	1.364 (14)
O1—C2	1.348 (10)	C5—C10	1.384 (12)
O1—C9	1.369 (10)	C6—C7	1.381 (14)
O4—C4	1.249 (10)	C7—C8	1.362 (14)
O2'—C2'	1.367 (11)	C8—C9	1.402 (13)
O2'—C21	1.396 (12)	C9—C10	1.383 (12)
O6'—C6'	1.351 (12)	C11—C12	1.472 (14)
O6'—C61	1.433 (11)	C1'—C2'	1.375 (13)
O121—C12	1.316 (12)	C1'—C6'	1.415 (13)
O122—C12	1.192 (11)	C2'—C3'	1.360 (14)
C2—C3	1.337 (11)	C3'—C4'	1.327 (16)
C2—C1'	1.478 (12)	C4'—C5'	1.373 (17)
C3—C4	1.428 (12)	C5'—C6'	1.398 (15)
C4—C10	1.461 (13)
C2—O1—C9	118.3 (6)	C9—C10—C4	118.4 (8)
C2'—O2'—C21	117.0 (9)	C5—C10—C4	122.8 (8)
C6'—O6'—C61	118.9 (9)	C12—C11—Br1	118.2 (8)
C3—C2—O1	123.2 (8)	O122—C12—O121	123.2 (10)
C3—C2—C1'	123.6 (8)	O122—C12—C11	120.3 (11)
O1—C2—C1'	113.1 (7)	O121—C12—C11	116.4 (9)
C2—C3—C4	121.7 (8)	C2'—C1'—C6'	119.7 (9)
O4—C4—C3	123.7 (8)	C2'—C1'—C2	122.8 (10)
O4—C4—C10	120.9 (8)	C6'—C1'—C2	117.3 (9)
C3—C4—C10	115.4 (8)	C3'—C2'—O2'	124.0 (11)
C6—C5—C10	120.6 (9)	C3'—C2'—C1'	121.6 (11)
C5—C6—C7	119.9 (9)	O2'—C2'—C1'	114.2 (9)
C8—C7—C6	121.4 (10)	C4'—C3'—C2'	118.8 (12)
C7—C8—C9	118.2 (9)	C3'—C4'—C5'	123.2 (11)
O1—C9—C10	123.0 (8)	C4'—C5'—C6'	119.6 (12)
O1—C9—C8	116.0 (8)	O6'—C6'—C5'	126.0 (11)
C10—C9—C8	121.0 (9)	O6'—C6'—C1'	117.0 (9)
C9—C10—C5	118.8 (9)	C5'—C6'—C1'	117.0 (11)
C9—O1—C2—C3	−2.4 (14)	Br1—C11—C12—O121	4.7 (16)
C9—O1—C2—C1'	179.4 (9)	C3—C2—C1'—C2'	−59.5 (14)
O1—C2—C3—C4	2.8 (15)	O1—C2—C1'—C2'	118.7 (10)
C1'—C2—C3—C4	−179.1 (9)	C3—C2—C1'—C6'	115.3 (11)
C2—C3—C4—O4	179.7 (9)	O1—C2—C1'—C6'	−66.5 (11)
C2—C3—C4—C10	−1.2 (15)	C21—O2'—C2'—C3'	−5.9 (15)
C10—C5—C6—C7	1.3 (17)	C21—O2'—C2'—C1'	177.5 (9)
C5—C6—C7—C8	−2.1 (19)	C6'—C1'—C2'—C3'	1.4 (15)
C6—C7—C8—C9	1.7 (18)	C2—C1'—C2'—C3'	176.0 (9)
C2—O1—C9—C10	0.3 (14)	C6'—C1'—C2'—O2'	178.1 (8)
C2—O1—C9—C8	−179.7 (9)	C2—C1'—C2'—O2'	−7.2 (13)
C7—C8—C9—O1	179.5 (10)	O2'—C2'—C3'—C4'	−178.6 (11)
C7—C8—C9—C10	−0.5 (17)	C1'—C2'—C3'—C4'	−2.2 (17)
O1—C9—C10—C5	179.8 (9)	C2'—C3'—C4'—C5'	3 (2)
C8—C9—C10—C5	−0.2 (16)	C3'—C4'—C5'—C6'	−3.0 (19)
O1—C9—C10—C4	1.1 (16)	C61—O6'—C6'—C5'	5.3 (14)
C8—C9—C10—C4	−178.8 (9)	C61—O6'—C6'—C1'	−173.4 (8)
C6—C5—C10—C9	−0.2 (16)	C4'—C5'—C6'—O6'	−176.7 (10)
C6—C5—C10—C4	178.4 (10)	C4'—C5'—C6'—C1'	2.0 (16)
O4—C4—C10—C9	178.5 (9)	C2'—C1'—C6'—O6'	177.5 (9)
C3—C4—C10—C9	−0.7 (14)	C2—C1'—C6'—O6'	2.6 (12)
O4—C4—C10—C5	−0.1 (16)	C2'—C1'—C6'—C5'	−1.3 (14)
C3—C4—C10—C5	−179.3 (9)	C2—C1'—C6'—C5'	−176.2 (9)
Br1—C11—C12—O122	−175.8 (9)

Hydrogen-bond geometry (Å, º)

D—H···A	D—H	H···A	D···A	D—H···A
O121—H121···O4	1.09 (14)	1.51 (14)	2.534 (9)	152 (11)
C3—H3···O122	0.93	2.44	3.305 (12)	156