2-(4-Formyl-2,6-dimeth­oxy­phenoxy)­acetic acid

Collas, A.; Vande Velde, C.M.L.; Blockhuys, F.

doi:10.1107/S1600536810043990

organic compounds

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Volume 66| Part 11| November 2010| Page o3003

https://doi.org/10.1107/S1600536810043990

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2-(4-Formyl-2,6-dimethoxyphenoxy)acetic acid

Alain Collas,^a Christophe M. L. Vande Velde ^a ‡ and Frank Blockhuys ^a ^*

^aDepartment of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Wilrijk, Belgium
^*Correspondence e-mail: frank.blockhuys@ua.ac.be

(Received 22 October 2010; accepted 27 October 2010; online 31 October 2010)

In the title compound, C₁₁H₁₂O₆, the aldehyde group is disordered over two sites in a 0.79:0.21 ratio. The carboxylic acid chain is found in the [ap,ap] conformation due to two intramolecular O—H⋯O hydrogen bonds.

Related literature

For related acetic acids substituted in the α-position, see: Lundquist et al. (1987 ). For conformational and geometric considerations of carboxylic acids, see: Lide (1964 ); Leiserowitz (1976 ). For applications of PPV oligomers, see: Chemla (1987 ); Bandyopadhyay & Pal (2003 ). For hydrogen bonding and crystal engineering, see: Desiraju (1997 ); Steiner (2002 ).

Experimental

Crystal data

C₁₁H₁₂O₆
M_r = 240.21
Monoclinic, P 2₁ /c
a = 9.350 (2) Å
b = 7.416 (1) Å
c = 17.374 (8) Å
β = 113.67 (3)°
V = 1103.4 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.12 mm⁻¹
T = 293 K
0.27 × 0.24 × 0.15 mm

Data collection

Enraf–Nonius MACH3 diffractometer
4025 measured reflections
2015 independent reflections
1292 reflections with I > 2σ(I)
R_int = 0.030
3 standard reflections every 60 min intensity decay: 1%

Refinement

R[F² > 2σ(F²)] = 0.036
wR(F²) = 0.093
S = 1.01
2015 reflections
171 parameters
8 restraints
H-atom parameters constrained
Δρ_max = 0.15 e Å⁻³
Δρ_min = −0.15 e Å⁻³

Table 1
Hydrogen-bond geometry (Å, °)

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O42—H42⋯O4	0.82	2.11	2.617 (2)	120
O42—H42⋯O5	0.82	2.18	2.932 (2)	153
C6—H6⋯O41ⁱ	0.93	2.54	3.468 (3)	176
C41—H41A⋯O11Bⁱⁱ	0.97	2.71	3.189 (9)	111
C51—H51B⋯O11Aⁱⁱⁱ	0.96	2.57	3.369 (3)	141
C31—H31B⋯O11A^iv	0.96	2.70	3.454 (3)	136
C41—H41B⋯O4^v	0.97	2.56	3.527 (3)	173
Symmetry codes: (i) $[x, -y+{\script{3\over 2}}, z-{\script{1\over 2}}]$ ; (ii) $[x, -y+{\script{3\over 2}}, z+{\script{1\over 2}}]$ ; (iii) x-1, y, z; (iv) $[-x+2, y+{\script{1\over 2}}, -z+{\script{3\over 2}}]$ ; (v) $[-x+1, y-{\script{1\over 2}}, -z+{\script{3\over 2}}]$ .

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994 ); cell refinement: CAD-4 EXPRESS; data reduction: XCAD4 (Harms & Wocadlo, 1996 ); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ); software used to prepare material for publication: WinGX (Farrugia, 1999 ).

Supporting information

Crystal structure: contains datablocks I, global. DOI: https://doi.org/10.1107/S1600536810043990/zl2319sup1.cif

Structure factors: contains datablock I. DOI: https://doi.org/10.1107/S1600536810043990/zl2319Isup2.hkl

checkCIF report

Comment top

The title compound was synthesized as a precursor for asymmetric PPV-type [poly(p-phenylene vinylene)] oligomers. These compounds are promising candidates as the active materials in organic memories (Bandyopadhyay & Pal, 2003) and as nonlinear optical (NLO) materials with a high first-order hyperpolarizability (Chemla, 1987). Besides the condition that these oligomers should bear acceptor and donor substituents connected by a π-system, it is of critical importance for their usefulness as an NLO material and as a bistable organic memory material that the crystal packing is non-centrosymmetric. In particular, the compound should crystallize in a polar space group. To engineer the crystal packing in order to meet this criterion, it is necessary to introduce certain statistically well chosen synthons (Desiraju, 1997). Therefore, we opted for carboxylic acid functional groups (powerful hydrogen bond donors) in the basic structure of the organic semiconductors. To combine the electronic (A-π-D) and the structural (non-centrosymmetric space group) requirements, we used the Williamson ether synthesis to prepare the title compound as a building block for a PPV-based semiconductor bearing a carboxylic acid moiety.

The carboxylic acid moiety is found in the [ap,ap] conformation (Fig. 1): the carboxyl H atom points in the opposite direction of the carbonyl group and the O4—C41—C42—O41 torsion angle is -168.64 (19)°. The reason for this unexpected conformation is the presence of an intramolecular bifurcated hydrogen bond involving H42, O4 and O5 (Table 1 and Fig. 2). Indeed, Lide showed, based on microwave experiments on gaseous formic acid, that, in general, the sp conformer is more stable than the ap conformer by about 16 kJ mol^-1 (Lide, 1964). The acetic acid chain is twisted out-of-plane by about 113° and the torsion angle O4—C41—C42—O42 is about 11°.

A sawtooth motif is generated along the c axis by the CH···O interaction between H6 and O41 (Fig. 2). Its effect is reinforced by H41A contacting O11B, the aldehyde O atom of the minor conformer. Perpendicular to these sawtooth ribbons (along the a axis) C51—H51B···O11A hydrogen bonds continue the structure (Fig. 2). These corrugated sheets are then stacked along the b axis by two weak CH···O hydrogen bonds and a CH···π interaction (Fig. 3): H31B contacts O11A, H41B contacts O4 and H41A contacts the centroid of the ring [C41—H41A···Cg^vi, 2.68 Å, 144°, symm. code vi = 1 - x, 1/2 + y, 3/2 - z]. Finally, there is a modest π–π interaction [Cg···Cg^vii, 4.133 (2) Å, 34.09°, symm. code vii = 1 - x, 2 - y, 1 - z].

Related literature top

For related acetic acids substituted in the α-position, see: Lundquist et al. (1987). For conformational and geometric considerations of carboxylic acids, see: Lide (1964); Leiserowitz (1976). For applications of PPV oligomers, see: Chemla (1987); Bandyopadhyay & Pal (2003). For hydrogen bonding and crystal engineering, see: Desiraju (1997); Steiner (2002).

Experimental top

Sodium hydroxide (5.0 g, 0.125 mol) in distilled water (20 ml) was added to a stirred solution of syringaldehyde (11.8 g, 0.065 mol) and iodoacetic acid (12.1 g, 0.065 mol) in distilled water (100 ml). The mixture was refluxed overnight and then poured into water (100 ml), which was then acidified using phosphoric acid. The mixture was left to cool in the refrigerator and the solvent was partially evaporated to precipitate the compound. The brown needle-like crystals were filtered off. The product changed colour to purple when it was exposed to air. The purple product was recrystallized from a 5:1 dichloromethane/acetone mixture to yield (54%) colourless crystals. ¹H NMR (CDCl₃, 400 MHz, TMS): δ 3.98 (s, 6H, H31 and H51), 4.69 (s, 2H, H41), 7.16 (s, 2H, H2 and H6), 9.89 (s, 1H, H11). ¹³C NMR (CDCl₃, 100 MHz, TMS): δ 56.6 (C31 and C51), 70.3, (C41), 106.6 (C2 and C6), 132.9 (C1), 141.1 (C4), 152.6 (C3 and C5), 170.2 (C42), 190.5 (C11).

Structure description top

# Following replaced by publCIF - wo 22. aug 16:49:48 2007

The stucture of the title compound, (I), is shown below. Dimensions are available in the archived CIF.

For related literature, see [type here to add references to related literature].

Computing details top

Data collection: CAD-4 EXPRESS (Enraf–Nonius, 1994); cell refinement: CAD-4 EXPRESS (Enraf–Nonius, 1994); data reduction: XCAD4 (Harms & Wocadlo, 1996); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top

	Fig. 1. Molecular structure of the title compound with the numbering scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are represented as spheres with an arbitrary radius.
	Fig. 2. Corrugated sheets in the ac plane generated by weak intermolecular hydrogen bonds and the bifurcated intramolecular hydrogen bond.
	Fig. 3. The two weak hydrogen bonds and the CH···π interaction responsible for the stacking of the sheets along the b axis.

2-(4-Formyl-2,6-dimethoxyphenoxy)acetic acid top

Crystal data top

C₁₁H₁₂O₆	F(000) = 504
M_r = 240.21	D_x = 1.446 Mg m⁻³
Monoclinic, P2₁/c	Melting point: 415 K
Hall symbol: -P 2ybc	Mo Kα radiation, λ = 0.71073 Å
a = 9.350 (2) Å	Cell parameters from 25 reflections
b = 7.416 (1) Å	θ = 9.0–14.2°
c = 17.374 (8) Å	µ = 0.12 mm⁻¹
β = 113.67 (3)°	T = 293 K
V = 1103.4 (6) Å³	Block, colourless
Z = 4	0.27 × 0.24 × 0.15 mm

Data collection top

Enraf–Nonius MACH3 diffractometer	R_int = 0.030
Radiation source: fine-focus sealed tube	θ_max = 25.3°, θ_min = 2.4°
Graphite monochromator	h = −11→11
ω/2θ scans	k = 0→8
4025 measured reflections	l = −20→20
2015 independent reflections	3 standard reflections every 60 min
1292 reflections with I > 2σ(I)	intensity decay: 1%

Refinement top

Refinement on F²	Secondary atom site location: difference Fourier map
Least-squares matrix: full	Hydrogen site location: inferred from neighbouring sites
R[F² > 2σ(F²)] = 0.036	H-atom parameters constrained
wR(F²) = 0.093	w = 1/[σ²(F_o²) + (0.0427P)² + 0.1341P] where P = (F_o² + 2F_c²)/3
S = 1.01	(Δ/σ)_max < 0.001
2015 reflections	Δρ_max = 0.15 e Å⁻³
171 parameters	Δρ_min = −0.15 e Å⁻³
8 restraints	Extinction correction: SHELXL97 (Sheldrick, 2008), Fc^*=kFc[1+0.001xFc²λ³/sin(2θ)]^-1/4
Primary atom site location: structure-invariant direct methods	Extinction coefficient: 0.0086 (18)

Crystal data top

C₁₁H₁₂O₆	V = 1103.4 (6) Å³
M_r = 240.21	Z = 4
Monoclinic, P2₁/c	Mo Kα radiation
a = 9.350 (2) Å	µ = 0.12 mm⁻¹
b = 7.416 (1) Å	T = 293 K
c = 17.374 (8) Å	0.27 × 0.24 × 0.15 mm
β = 113.67 (3)°

Data collection top

Enraf–Nonius MACH3 diffractometer	R_int = 0.030
4025 measured reflections	3 standard reflections every 60 min
2015 independent reflections	intensity decay: 1%
1292 reflections with I > 2σ(I)

Refinement top

R[F² > 2σ(F²)] = 0.036	8 restraints
wR(F²) = 0.093	H-atom parameters constrained
S = 1.01	Δρ_max = 0.15 e Å⁻³
2015 reflections	Δρ_min = −0.15 e Å⁻³
171 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

	x	y	z	U_iso*/U_eq	Occ. (<1)
O11A	0.8177 (2)	0.6876 (3)	0.52772 (13)	0.0677 (9)	0.785 (6)
C11A	0.6811 (5)	0.6988 (12)	0.5115 (3)	0.0490 (13)	0.785 (6)
H11A	0.6121	0.6482	0.4613	0.059*	0.785 (6)
C11B	0.720 (3)	0.712 (5)	0.5283 (16)	0.0490 (13)	0.215 (6)
H11B	0.8278	0.7181	0.5571	0.059*	0.215 (6)
O11B	0.6629 (10)	0.6437 (14)	0.4603 (6)	0.078 (3)	0.215 (6)
O4	0.39907 (13)	1.04247 (17)	0.70196 (7)	0.0376 (3)
O5	0.22382 (14)	0.89227 (19)	0.55872 (8)	0.0449 (4)
O3	0.71034 (14)	1.0208 (2)	0.76755 (8)	0.0478 (4)
C6	0.4523 (2)	0.7946 (3)	0.53433 (11)	0.0388 (5)
H6	0.3923	0.7439	0.4824	0.047*
C2	0.7062 (2)	0.8612 (3)	0.64352 (11)	0.0414 (5)
H2	0.8144	0.8545	0.6638	0.050*
C5	0.38175 (19)	0.8774 (2)	0.58135 (10)	0.0345 (4)
O42	0.13206 (15)	0.9328 (2)	0.70058 (9)	0.0604 (5)
H42	0.1655	0.9578	0.6649	0.091*
C4	0.47318 (19)	0.9529 (2)	0.65853 (10)	0.0334 (4)
O41	0.22968 (17)	0.8754 (2)	0.83608 (9)	0.0623 (5)
C1	0.6143 (2)	0.7884 (3)	0.56601 (11)	0.0392 (5)
C41	0.4098 (2)	0.9607 (3)	0.77859 (11)	0.0380 (4)
H41A	0.4634	1.0416	0.8252	0.046*
H41B	0.4701	0.8502	0.7880	0.046*
C3	0.6358 (2)	0.9442 (2)	0.69064 (11)	0.0369 (4)
C42	0.2502 (2)	0.9191 (3)	0.77494 (12)	0.0429 (5)
C51	0.1233 (2)	0.8060 (3)	0.48261 (12)	0.0551 (6)
H51A	0.1374	0.8599	0.4359	0.083*
H51B	0.0167	0.8202	0.4755	0.083*
H51C	0.1484	0.6800	0.4853	0.083*
C31	0.8750 (3)	0.9877 (4)	0.80939 (15)	0.0730 (7)
H31A	0.8941	0.8602	0.8120	0.110*
H31B	0.9128	1.0359	0.8653	0.110*
H31C	0.9282	1.0449	0.7788	0.110*

Atomic displacement parameters (Å²) top

	U¹¹	U²²	U³³	U¹²	U¹³	U²³
O11A	0.0510 (16)	0.0877 (17)	0.0786 (16)	0.0113 (11)	0.0409 (12)	0.0007 (12)
C11A	0.050 (3)	0.052 (2)	0.049 (3)	0.002 (3)	0.025 (3)	0.002 (2)
C11B	0.050 (3)	0.052 (2)	0.049 (3)	0.002 (3)	0.025 (3)	0.002 (2)
O11B	0.084 (6)	0.101 (7)	0.053 (6)	0.007 (5)	0.031 (5)	−0.019 (5)
O4	0.0424 (7)	0.0359 (7)	0.0372 (7)	0.0054 (6)	0.0188 (6)	0.0017 (6)
O5	0.0315 (7)	0.0590 (9)	0.0409 (7)	0.0027 (6)	0.0109 (6)	−0.0073 (6)
O3	0.0327 (7)	0.0590 (9)	0.0445 (8)	−0.0028 (6)	0.0080 (6)	−0.0074 (7)
C6	0.0424 (11)	0.0409 (11)	0.0330 (9)	0.0001 (9)	0.0149 (8)	0.0011 (9)
C2	0.0340 (10)	0.0435 (11)	0.0503 (11)	0.0039 (9)	0.0206 (9)	0.0078 (9)
C5	0.0327 (9)	0.0366 (10)	0.0354 (9)	0.0020 (8)	0.0148 (8)	0.0043 (8)
O42	0.0361 (7)	0.0922 (13)	0.0540 (9)	0.0028 (8)	0.0193 (7)	0.0085 (9)
C4	0.0364 (9)	0.0309 (10)	0.0375 (9)	0.0034 (8)	0.0196 (8)	0.0026 (8)
O41	0.0623 (9)	0.0806 (12)	0.0556 (9)	0.0015 (9)	0.0359 (8)	0.0100 (8)
C1	0.0452 (10)	0.0375 (11)	0.0438 (11)	0.0053 (9)	0.0271 (9)	0.0068 (9)
C41	0.0399 (10)	0.0419 (11)	0.0321 (9)	0.0023 (9)	0.0142 (8)	−0.0017 (8)
C3	0.0349 (9)	0.0359 (10)	0.0394 (10)	−0.0019 (8)	0.0144 (8)	0.0036 (9)
C42	0.0434 (11)	0.0454 (12)	0.0433 (11)	0.0047 (9)	0.0210 (9)	0.0012 (9)
C51	0.0376 (11)	0.0738 (16)	0.0470 (12)	−0.0074 (11)	0.0095 (9)	−0.0118 (11)
C31	0.0452 (13)	0.0778 (18)	0.0681 (15)	0.0078 (12)	−0.0066 (11)	−0.0103 (14)

Geometric parameters (Å, º) top

O11A—C11A	1.195 (5)	C2—C1	1.384 (3)
C11A—C1	1.485 (4)	C2—H2	0.9300
C11A—H11A	0.9300	C5—C4	1.386 (2)
C11B—O11B	1.196 (17)	O42—C42	1.324 (2)
C11B—C1	1.498 (16)	O42—H42	0.8200
C11B—H11B	0.9300	C4—C3	1.395 (2)
O4—C4	1.382 (2)	O41—C42	1.197 (2)
O4—C41	1.430 (2)	C41—C42	1.500 (3)
O5—C5	1.371 (2)	C41—H41A	0.9700
O5—C51	1.430 (2)	C41—H41B	0.9700
O3—C3	1.359 (2)	C51—H51A	0.9600
O3—C31	1.435 (3)	C51—H51B	0.9600
C6—C5	1.383 (2)	C51—H51C	0.9600
C6—C1	1.389 (3)	C31—H31A	0.9600
C6—H6	0.9300	C31—H31B	0.9600
C2—C3	1.383 (3)	C31—H31C	0.9600

O11A—C11A—C1	124.3 (3)	C6—C1—C11B	130.1 (9)
O11A—C11A—H11A	117.8	O4—C41—C42	110.56 (15)
C1—C11A—H11A	117.8	O4—C41—H41A	109.5
O11B—C11B—C1	118.8 (19)	C42—C41—H41A	109.5
O11B—C11B—H11B	120.6	O4—C41—H41B	109.5
C1—C11B—H11B	120.6	C42—C41—H41B	109.5
C4—O4—C41	116.19 (13)	H41A—C41—H41B	108.1
C5—O5—C51	117.50 (14)	O3—C3—C2	126.16 (16)
C3—O3—C31	116.68 (16)	O3—C3—C4	114.84 (16)
C5—C6—C1	118.91 (17)	C2—C3—C4	119.00 (16)
C5—C6—H6	120.5	O41—C42—O42	121.25 (19)
C1—C6—H6	120.5	O41—C42—C41	121.93 (18)
C3—C2—C1	119.53 (17)	O42—C42—C41	116.83 (16)
C3—C2—H2	120.2	O5—C51—H51A	109.5
C1—C2—H2	120.2	O5—C51—H51B	109.5
O5—C5—C6	125.46 (16)	H51A—C51—H51B	109.5
O5—C5—C4	114.83 (15)	O5—C51—H51C	109.5
C6—C5—C4	119.71 (15)	H51A—C51—H51C	109.5
C42—O42—H42	109.5	H51B—C51—H51C	109.5
O4—C4—C5	118.19 (15)	O3—C31—H31A	109.5
O4—C4—C3	120.58 (16)	O3—C31—H31B	109.5
C5—C4—C3	121.20 (16)	H31A—C31—H31B	109.5
C2—C1—C6	121.65 (17)	O3—C31—H31C	109.5
C2—C1—C11A	122.7 (2)	H31A—C31—H31C	109.5
C6—C1—C11A	115.7 (2)	H31B—C31—H31C	109.5
C2—C1—C11B	108.2 (9)

C51—O5—C5—C6	3.9 (3)	O11A—C11A—C1—C6	177.2 (6)
C51—O5—C5—C4	−175.66 (17)	O11A—C11A—C1—C11B	0 (7)
C1—C6—C5—O5	−179.30 (17)	O11B—C11B—C1—C2	−179 (3)
C1—C6—C5—C4	0.2 (3)	O11B—C11B—C1—C6	0 (4)
C41—O4—C4—C5	112.81 (18)	O11B—C11B—C1—C11A	3 (4)
C41—O4—C4—C3	−69.2 (2)	C4—O4—C41—C42	−120.89 (17)
O5—C5—C4—O4	−3.6 (2)	C31—O3—C3—C2	−10.5 (3)
C6—C5—C4—O4	176.83 (16)	C31—O3—C3—C4	169.40 (19)
O5—C5—C4—C3	178.46 (16)	C1—C2—C3—O3	179.70 (17)
C6—C5—C4—C3	−1.1 (3)	C1—C2—C3—C4	−0.2 (3)
C3—C2—C1—C6	−0.7 (3)	O4—C4—C3—O3	3.3 (2)
C3—C2—C1—C11A	179.4 (5)	C5—C4—C3—O3	−178.83 (17)
C3—C2—C1—C11B	178.6 (17)	O4—C4—C3—C2	−176.79 (17)
C5—C6—C1—C2	0.6 (3)	C5—C4—C3—C2	1.1 (3)
C5—C6—C1—C11A	−179.4 (4)	O4—C41—C42—O41	−168.63 (19)
C5—C6—C1—C11B	−178 (2)	O4—C41—C42—O42	11.4 (2)
O11A—C11A—C1—C2	−2.9 (10)

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O42—H42···O4	0.82	2.11	2.617 (2)	120
O42—H42···O5	0.82	2.18	2.932 (2)	153
C6—H6···O41ⁱ	0.93	2.54	3.468 (3)	176
C41—H41A···O11Bⁱⁱ	0.97	2.71	3.189 (9)	111
C51—H51B···O11Aⁱⁱⁱ	0.96	2.57	3.369 (3)	141
C31—H31B···O11A^iv	0.96	2.70	3.454 (3)	136
C41—H41B···O4^v	0.97	2.56	3.527 (3)	173

Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) x, −y+3/2, z+1/2; (iii) x−1, y, z; (iv) −x+2, y+1/2, −z+3/2; (v) −x+1, y−1/2, −z+3/2.

Experimental details

Crystal data
Chemical formula	C₁₁H₁₂O₆
M_r	240.21
Crystal system, space group	Monoclinic, P2₁/c
Temperature (K)	293
a, b, c (Å)	9.350 (2), 7.416 (1), 17.374 (8)
β (°)	113.67 (3)
V (Å³)	1103.4 (6)
Z	4
Radiation type	Mo Kα
µ (mm⁻¹)	0.12
Crystal size (mm)	0.27 × 0.24 × 0.15

Data collection
Diffractometer	Enraf–Nonius MACH3
Absorption correction	–
No. of measured, independent and observed [I > 2σ(I)] reflections	4025, 2015, 1292
R_int	0.030
(sin θ/λ)_max (Å⁻¹)	0.602

Refinement
R[F² > 2σ(F²)], wR(F²), S	0.036, 0.093, 1.01
No. of reflections	2015
No. of parameters	171
No. of restraints	8
H-atom treatment	H-atom parameters constrained
Δρ_max, Δρ_min (e Å⁻³)	0.15, −0.15

Computer programs: CAD-4 EXPRESS (Enraf–Nonius, 1994), XCAD4 (Harms & Wocadlo, 1996), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), ORTEP-3 for Windows (Farrugia, 1997), WinGX (Farrugia, 1999).

Hydrogen-bond geometry (Å, º) top

D—H···A	D—H	H···A	D···A	D—H···A
O42—H42···O4	0.82	2.11	2.617 (2)	120
O42—H42···O5	0.82	2.18	2.932 (2)	153
C6—H6···O41ⁱ	0.93	2.54	3.468 (3)	176
C41—H41A···O11Bⁱⁱ	0.97	2.71	3.189 (9)	111
C51—H51B···O11Aⁱⁱⁱ	0.96	2.57	3.369 (3)	141
C31—H31B···O11A^iv	0.96	2.70	3.454 (3)	136
C41—H41B···O4^v	0.97	2.56	3.527 (3)	173

Symmetry codes: (i) x, −y+3/2, z−1/2; (ii) x, −y+3/2, z+1/2; (iii) x−1, y, z; (iv) −x+2, y+1/2, −z+3/2; (v) −x+1, y−1/2, −z+3/2.

Footnotes

‡Current address: Karel de Grote University College, Department of Applied Engineering, Salesianenlaan 30, B-2660 Antwerp, Belgium.

Acknowledgements

CMLVV thanks the Fund for Scientific Research (FWO Vlaanderen) for a grant as a research assistant. AC thanks the Institute for the Promotion of Innovation by Science and Technology in Flanders (IWT) for a predoctoral grant.

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