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, beta = 102.370 (9)°, V = 1670 (2) Å3.
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.
Reproduced with permission. Copyright 2015, International Union of Crystallography