Structural investigation of N,N′-methylenebisacryl­amide via X-ray diffraction assisted by crystal structure prediction

The crystal structure of N,N′-methylenebisacrylamide was determined through the geometry optimization of the molecular unit with density functional theory and conformational analysis, and then through the calculation of the packing via a crystal structure prediction protocol, based on lattice energy minimization. All the calculated structures were ranked, comparing their powder pattern with the laboratory low-quality X-ray diffraction data. Rietveld refinement of the best three proposed structures allowed the most probable crystal arrangement of the molecules to be obtained. This approach was essential for disentangling the twinning problems affecting the single-crystal X-ray diffraction data, collected on samples obtained via recrystallization of powder, which definitely confirmed the predicted model. It was found that N,N′-methylenebisacrylamide shows a monoclinic structure in the space group C2/c, with lattice parameters a = 17.822 (12), b = 4.850 (3), c = 19.783 (14) Å, β = 102.370 (9)°, V = 1670 (2) ų. Two strong interactions between the amide protons and the carbonyl groups of neighbouring molecules were found along the b axis, determining the crystal growth in the form of wires in this direction. This work provides a further example of how computational methods may help to investigate low-quality molecular crystals with standard diffraction techniques.

Computing details

Data collection: APEX2 (Bruker, 2008); cell refinement: APEX2 (Bruker, 2008); data reduction: SAINT (Bruker, 2008); program(s) used to solve structure: SHELXS97 (Sheldrick, 1990); 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).

(I)

Crystal data

C7H10N2O2	F(000) = 656
Mr = 154.17	Dx = 1.226 Mg m^−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
a = 17.822 (12) Å	Cell parameters from 90 reflections
b = 4.850 (3) Å	θ = 5–15°
c = 19.783 (14) Å	µ = 0.09 mm^−1
β = 102.370 (9)°	T = 293 K
V = 1670 (2) Å^3	Needle, colorless
Z = 8	0.20 × 0.09 × 0.06 mm

Data collection

APEX II diffractometer	1461 independent reflections
Radiation source: fine-focus sealed tube	871 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.075
OMEGA SCAN scans	θmax = 25.0°, θmin = 2.1°
Absorption correction: empirical (using intensity measurements) software bruker	h = −21→21
Tmin = 0.552, Tmax = 0.746	k = −5→5
8010 measured reflections	l = −23→23

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)] = 0.074	Hydrogen site location: inferred from neighbouring sites
wR(F^2) = 0.228	H-atom parameters constrained
S = 0.99	w = 1/[σ^2(Fo^2) + (0.0758P)^2 + 6.8758P] where P = (Fo^2 + 2Fc^2)/3
1461 reflections	(Δ/σ)max < 0.001
100 parameters	Δρmax = 0.24 e Å^−3
0 restraints	Δρmin = −0.19 e Å^−3

Special details

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'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 > 2σ(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
C1	0.1212 (3)	0.3506 (9)	−0.0069 (2)	0.0514 (11)
C2	0.1700 (2)	0.1805 (8)	0.1933 (2)	0.0475 (11)
C3	0.2245 (3)	0.2668 (10)	0.0929 (2)	0.0546 (12)
H3A	0.2521	0.4174	0.0770	0.066*
H3B	0.2606	0.1171	0.1069	0.066*
C4	0.0588 (3)	0.2240 (10)	−0.0579 (2)	0.0621 (13)
H4	0.0581	0.0330	−0.0621	0.075*
C5	0.0052 (3)	0.3612 (12)	−0.0967 (3)	0.0781 (16)
H5A	0.0044	0.5525	−0.0936	0.094*
H5B	−0.0330	0.2699	−0.1281	0.094*
C6	0.1402 (3)	0.3040 (10)	0.2498 (2)	0.0596 (13)
H6	0.1441	0.4941	0.2558	0.071*
C7	0.1092 (4)	0.1646 (12)	0.2913 (3)	0.101 (2)
H7A	0.1045	−0.0258	0.2864	0.121*
H7B	0.0911	0.2533	0.3263	0.121*
N1	0.1650 (2)	0.1751 (7)	0.03660 (17)	0.0550 (10)
H1	0.1572	0.0010	0.0306	0.066*
N2	0.1961 (2)	0.3576 (7)	0.15207 (17)	0.0505 (10)
H2	0.1960	0.5310	0.1611	0.061*
O1	0.1329 (2)	0.6015 (6)	−0.00422 (18)	0.0701 (11)
O2	0.17040 (19)	−0.0707 (6)	0.18383 (17)	0.0639 (10)

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.068 (3)	0.040 (2)	0.049 (2)	0.006 (2)	0.017 (2)	−0.001 (2)
C2	0.055 (3)	0.037 (2)	0.047 (2)	0.0042 (19)	0.003 (2)	0.0022 (19)
C3	0.066 (3)	0.048 (3)	0.050 (3)	0.004 (2)	0.013 (2)	0.003 (2)
C4	0.091 (4)	0.045 (3)	0.048 (3)	0.002 (3)	0.011 (3)	−0.008 (2)
C5	0.082 (4)	0.067 (3)	0.080 (4)	−0.007 (3)	0.006 (3)	−0.002 (3)
C6	0.081 (3)	0.046 (3)	0.055 (3)	0.006 (2)	0.022 (3)	−0.001 (2)
C7	0.145 (6)	0.067 (4)	0.117 (5)	0.016 (4)	0.085 (5)	0.013 (4)
N1	0.083 (3)	0.039 (2)	0.042 (2)	−0.0007 (19)	0.0122 (19)	−0.0014 (16)
N2	0.071 (3)	0.0359 (19)	0.044 (2)	−0.0018 (17)	0.0110 (18)	−0.0036 (16)
O1	0.090 (3)	0.0323 (17)	0.083 (2)	−0.0001 (16)	0.0084 (19)	0.0018 (16)
O2	0.091 (3)	0.0319 (17)	0.073 (2)	0.0025 (15)	0.0249 (19)	−0.0025 (15)

Geometric parameters (Å, º)

C1—O1	1.234 (5)	C4—C5	1.277 (7)
C1—N1	1.336 (5)	C4—H4	0.9300
C1—C4	1.467 (7)	C5—H5A	0.9300
C2—O2	1.233 (5)	C5—H5B	0.9300
C2—N2	1.334 (5)	C6—C7	1.277 (7)
C2—C6	1.466 (6)	C6—H6	0.9300
C3—N1	1.435 (6)	C7—H7A	0.9300
C3—N2	1.439 (5)	C7—H7B	0.9300
C3—H3A	0.9700	N1—H1	0.8600
C3—H3B	0.9700	N2—H2	0.8600
O1—C1—N1	122.0 (4)	C4—C5—H5A	120.0
O1—C1—C4	122.6 (4)	C4—C5—H5B	120.0
N1—C1—C4	115.4 (4)	H5A—C5—H5B	120.0
O2—C2—N2	122.0 (4)	C7—C6—C2	123.5 (5)
O2—C2—C6	122.3 (4)	C7—C6—H6	118.3
N2—C2—C6	115.7 (4)	C2—C6—H6	118.3
N1—C3—N2	113.3 (4)	C6—C7—H7A	120.0
N1—C3—H3A	108.9	C6—C7—H7B	120.0
N2—C3—H3A	108.9	H7A—C7—H7B	120.0
N1—C3—H3B	108.9	C1—N1—C3	122.4 (4)
N2—C3—H3B	108.9	C1—N1—H1	118.8
H3A—C3—H3B	107.7	C3—N1—H1	118.8
C5—C4—C1	123.7 (5)	C2—N2—C3	121.9 (4)
C5—C4—H4	118.1	C2—N2—H2	119.0
C1—C4—H4	118.1	C3—N2—H2	119.0