Thermosalience in Macrocycle-Based Soft Crystals via Anisotropic Deformation of Disilanyl Architecture

Abstract

We describe here the preparation of soft crystals using disilanyl macrocycle C4 possessing four p-phenylenes circularly connected by four flexible disilane bonds. Single crystals of C4 exhibited a reversible thermal single-crystal-to-single-crystal (SCSC) phase transition behavior between two crystal phases accompanied by remarkable mechanical motion (thermosalient effect), as revealed by thermal analyses and X-ray diffraction measurements. Detailed structural analyses implied that flexibility of the parallelogram disilanyl architecture and molecular packing mode via weak intermolecular interactions facilitated a concerted structural transformation (parallel crank motion) of macrocycles in the crystal, thus resulting in the SCSC phase transition accompanied by anisotropic shrinking/elongation of the cells to induce the thermosalient effect. This work explores a new area of organosilicon chemistry and presents the potential utility of disilanyl macrocycles as soft crystals.

Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy

“…Dynamic crystals are mechanically active single-crystalline entities capable of amplifying small changes in molecular packing into large-scale anisotropic macroscopic motion. , These materials have CTEs over an order of magnitude higher than the best pure metals and undergo phase transitions at rates exceeding 10 5 times faster than non-thermosalient transitions. , This expansion is caused by a diffusionless phase transition that is initiated at crystalline extremities and rapidly propagates throughout the crystal. , In some of these systems, expansion can cause a sudden single-crystal-to-single-crystal (SCSC) phase transition with substantial changes in unit cell size, thus providing even greater material expansion. − In many of these SCSC thermosalient events, the transitions are typically irreversible and result in their destruction by splitting, , jumping, , or even dramatically exploding . These irreversible dynamic crystals have found applications as fuses, making use of their one-time ability to actuate to break a circuit; however, this irreversibility greatly limits their applications.…”

“…8 Dynamic crystals are mechanically active single-crystalline entities capable of amplifying small changes in molecular packing into large-scale anisotropic macroscopic motion. 9,10 These materials have CTEs over an order of magnitude higher than the best pure metals and undergo phase transitions at rates exceeding 10 5 times faster than non-thermosalient transitions. 9,11 This expansion is caused by a diffusionless phase transition that is initiated at crystalline extremities and rapidly propagates throughout the crystal.…”

Synthesis, Structure, and Photophysical Properties of Yellow-Green and Blue Photoluminescent Dinuclear and Octanuclear Copper(I) Iodide Complexes with a Disilanylene-Bridged Bispyridine Ligand

“…We recently investigated aromatic compounds connected with disilanylene groups (-SiR 2 SiR 2 -) [24][25][26][27][28][29][30][31][32][33]. Disilanylene-linkers extend the conjugated system through σ-π interaction, similarly to C=C double bonds.…”

Rapidly Reversible Organic Crystalline Switch for Conversion of Heat into Mechanical Energy

“…[9][10] These materials have CTEs over an order of magnitude higher than the best pure-metals and undergo phase transitions at rates exceeding 10 5 times faster than non-thermosalient transitions. 9,11 This expansion is caused by a diffusionless phase transition that is initiated at crystalline extremities and rapidly propagates throughout the crystal. [12][13] In some of these systems, expansion can cause a sudden single-crystal-to-single-crystal (SCSC) phase transition with substantial changes in unit cell size, thus providing even greater material expansion.…”