The way from isostructurality to polymorphism. Where are the borders? The role of supramolecular interactions and crystal symmetries

ABSTRACT

To produce substances with required physico-chemical properties demands the recognition of structural features of materials. It includes polymorphism and isostructurality which are strongly related with intermolecular interactions and crystal symmetries. Fine tuning of structural properties can be achieved by the application of substituents or in the case of multi-component systems by the introduction of molecules of different sizes, shapes and chemical compositions. How far can a crystal structure tolerate small molecular changes? The molecular conformation of flexible molecules may adjust to the supramolecular features both in the preserved and in the new lattices. Packing motifs conserving the supramolecular arrangement may still remain whereas the space groups may be different. This is morphotropy which may follow isostructurality in the course of stepwise chemical modification before a completely different packing arrangement appears. What is the degree of structurally decreasing similarity in fine-tuned systems that we may still consider to be isostructural and when do we say the structures are different?

KEYWORDS:

• Isostructurality
• polymorphism
• morphotropy
• supramolecular interactions
• crystal symmetries
• synthon engineering

Acknowledgements

The author is grateful to all the senior and younger crystallographers and chemists for education and collaboration and who contributed with teaching, discussions and compounds to help me synthesize this work. Highlighted from all co-authors of the cited papers are: Alajos Kálmán, Mátyás Czugler, László Fábián, Nikoletta B. Báthori, Tamás Holczbauer from the Research Centre for Natural Sciences, Hungarian Academy of Sciences; János Madarász, Edit Székely, Péter Molnár and Laura Bereczki from the Budapest University of Technology and Economics; Katalin Mészáros-Szécsényi from University of Novi Sad; Ingeborg Csöregh from Stockholm University; and last but not least Edwin Weber, Tobias Gruber and Conrad Fischer from the Technical University, Bergakademie Freiberg. The author expresses her thanks to the Editor, John Helliwell, for all his advices to improve this paper.

Disclosure statement

No potential conflict of interest was reported by the author.

Additional information

Funding

This work was supported by National Research, Development and Innovation Office – NKFIH (former Hungarian National Research Fund) [grant number OTKA K-100801].

Notes on contributors

Petra Bombicz

Petra Bombicz received a B.Sc. in 1987, an M.Sc. in organic synthesis in 1989, a ‘Dr. univ.’ in organosilicon chemistry in 1993 and a Ph.D. in crystallography in 1997 from the Budapest University of Technology and Economics. She joined the Chemical Crystallography Research Group of the Research Centre for Natural Sciences of the Hungarian Academy of Sciences in 1993, where 20 years later she became the head as the successor of Prof. Alajos Kálmán (working on research of polymorphism) and Prof. Mátyás Czugler (who has established supramolecular research in the group). She performed her postdoc at the Free University in Berlin, and was a visiting researcher at the Stockholm University, at the Studsvik Neutron Centre of Uppsala University and at the University of Cape Town. Her research interests include supramolecular chemistry, crystal engineering, intermolecular interactions, polymorphism and isostructurality involving single crystal X-ray diffraction.