Metal‐like Ductility in Organic Plastic Crystals: Role of Molecular Shape and Dihydrogen Bonding Interactions in Aminoboranes

Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomor...

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Bibliographic Details
Published in:Angewandte Chemie 2020-06, Vol.132 (27), p.11064-11073
Main Authors: Mondal, Amit, Bhattacharya, Biswajit, Das, Susobhan, Bhunia, Surojit, Chowdhury, Rituparno, Dey, Somnath, Reddy, C. Malla
Format: Article
Language:English
Subjects:
aminoboranes
Bonding strength
Chemistry
Compression
Crystal structure
Crystals
dihydrogen bonds
ductile crystals
Ductility
Electrostatic properties
Ferroelectric materials
Ferroelectricity
Metals
molecular globularity
Molten salt electrolytes
Organic crystals
plastic crystals
Robotics
Slip planes
Solid electrolytes
Symmetry
Twisting
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Summary:Ductility is a common phenomenon in many metals but is difficult to achieve in molecular crystals. Organic crystals bend plastically on one or two face‐specific directions but fracture when stressed in any other arbitrary directions. An exceptional metal‐like ductility and malleability in the isomorphous crystals of two globular molecules, BH3NMe3 and BF3NMe3, is reported, with characteristic tensile stretching, compression, twisting, and thinning. The mechanically deformed samples, which transition to lower symmetry phases, retain good long‐range order amenable to structure determination by single‐crystal X‐ray diffraction. Molecules in these high‐symmetry crystals interact through electrostatic forces (B−−N+) to form columnar structures with multiple slip planes and weak dispersive forces between columns. On the other hand, the limited number of facile slip planes and strong dihydrogen bonding in BH3NHMe2 negates ductility. Our study has implications for the design of soft ferroelectrics, solid electrolytes, barocalorics, and soft robotics. Slip slidin’ away: Aminoborane crystals can be deformed mechanically while retaining high crystallinity because multiple slip planes exist in their high‐symmetry structures. The presence of dihydrogen bonds in a similar semiglobular system, BH3NHMe2, negates ductility. Mechanically castable plastic crystals are appealing for applications such as ferroelectrics and soft robotics.
ISSN:0044-8249
1521-3757
DOI:10.1002/ange.202001060