N-Iodosaccharin-pyridine co-crystal system under pressure: experimental evidence of reversible twinning.
Acta Crystallogr B Struct Sci Cryst Eng Mater
; 78(Pt 3 Pt 2): 436-449, 2022 Jun 01.
Article
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| MEDLINE
| ID: mdl-35702961
ABSTRACT
This work presents a single-crystal X-ray diffraction study of an organic co-crystal composed of N-iodosaccharin and pyridine (NISac·py) under hydrostatic pressure ranging from 0.00â
(5)â
GPa to 4.5 (2)â
GPa. NISac·py crystallizes in the monoclinic system (space group B21/e). The unconventional setting of the space group is adopted (the conventional setting is P21/c, No. 14) to emphasise the strongly pseudo-orthorhombic symmetry of the lattice, with a ß angle very close to 90°. The crystal structure contains one molecule each of N-iodosaccharin (NISac) and pyridine (py) in the asymmetric unit (Z' = 1), linked via an Nsac...I...N'py halogen-bonding motif. A gradual modification of this motif is observed under pressure as a result of changes in the crystalline environment. Mechanical twinning is observed under compression and the sample splits into two domains, spanning an unequal volume that is mapped by a twofold rotation about the [100] direction of the B21/e unit cell. The twinning is particularly significant at high pressure, being reversible when the pressure is released. The structure of the twinned sample reveals the continuity of a substantial substructure across the composition plane. The presence of this common substructure in the two orientations of the twinned individuals can be interpreted as a structural reason for the formation of the twin and is the first observed example in a molecular crystal. These results indicate that the anisotropy of intermolecular interactions in the crystal structure results in an anisotropic strain generated upon the action of hydrostatic compression. Periodic density functional theory calculations were carried out by considering an isotropic external pressure, the results showing good agreement with the experimental findings. The bulk modulus of the crystal was obtained from the equations of state, being 7â
(1)â
GPa for experimental data and 6.8â
(5)â
GPa for theoretical data.
Palabras clave
Texto completo:
1
Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Piridinas
Límite:
Humans
Idioma:
En
Revista:
Acta Crystallogr B Struct Sci Cryst Eng Mater
Año:
2022
Tipo del documento:
Article
País de afiliación:
Francia