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Tilt and shift polymorphism in molecular perovskites.
Stefan Burger1, Shivani Grover2, Keith T Butler3
1Department of Chemistry, Technical University of Munich, Lichtenbergstraße 4, 85748 Garching, Germany. gregor.kieslich@tum.de.
Materials Horizons
|December 6, 2021
Summary
Molecular perovskites exhibit novel tilt and shift polymorphism, a type of irreversible phase transition unique to these materials. This discovery aids in classifying molecular perovskite crystal chemistry and understanding structure-property relationships.
Area of Science:
- Materials Science
- Solid-State Chemistry
- Crystallography
Background:
- Molecular perovskites (ABX 3 coordination polymers) are versatile materials for studying properties like barocalorics and ferroelectrics.
- Unlike inorganic perovskites, molecular perovskites offer unique geometric and structural freedom due to molecular ions on A- and X-sites.
Purpose of the Study:
- Introduce and define "tilt and shift polymorphism" for irreversible perovskite-to-perovskite phase transitions.
- Categorize phase transitions in molecular perovskites based on structural changes.
- Advance the classification of molecular perovskite crystal chemistry.
Main Methods:
- Synthesis of a new molecular perovskite series: [(nPr)3(CH3)N]M(C2N3)3 (M = Mn2+, Co2+, Ni2+).
- Investigation of crystallisation under varying synthetic conditions.
- Characterization of different polymorphs exhibiting distinct tilt systems within the perovskite structure.
Main Results:
- Demonstrated tilt and shift polymorphism in molecular perovskites, a phenomenon absent in inorganic perovskites.
- Identified different polymorphs crystallizing in the perovskite structure but with varying tilt systems.
- Established a link between synthetic conditions and the resulting polymorph.
Conclusions:
- Tilt and shift polymorphism is a direct consequence of using molecular building units in perovskites.
- This classification system is crucial for understanding the crystal chemistry of molecular perovskites.
- The findings represent a significant step in maturing the field of molecular perovskites and their structure-property relationships.
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