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Polymorph screening at surfaces of a benzothienobenzothiophene derivative: discovering new solvate forms†
a
Patrick
Brocorens,
b
Jérôme
Cornil,
b
Lucia
Maini,
e
Priya
Pandey,
e
Lorenzo
Pandolfi,
f
Elisabetta
Venuti,
f
Yves Henri
Geerts
cg
and
Roland
Resel
*a
Abstract
The discovery of new polymorphs opens up unique applications for molecular materials since their physical properties are predominantly influenced by the crystal structure type. The deposition of molecules at surfaces offers great potential in the variation of the crystallization conditions, thereby allowing access to unknown polymorphs. With our surface crystallization approach, four new phases are found for an oligoethylene glycol-benzothienobenzothiophene molecule, and none of these phases could be identified via classical polymorph screening. The corresponding crystal lattices of three of the new phases were obtained via X-ray diffraction (XRD). Based on the volumetric considerations together with X-ray fluorescence and Raman spectroscopy data, the phases are identified as solvates containing one, two or three solvent molecules per molecule. The strong interaction of dichloromethane with the oligoethylene glycol side chains of the molecules may be responsible for the formation of the solvates. Temperature-dependent XRD reveals the low thermal stability of the new phases, contrary to the thermodynamically stable bulk form. Nevertheless, the four solvates are stable under ambient conditions for at least two years. This work illustrates that defined crystallization at surfaces enables access to multiple solvates of a given material through precise and controlled variations in the crystallization kinetics.
- This article is part of the themed collection: Materials Horizons 10th anniversary regional spotlight collection: Europe
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