Low-Temperature Dynamics at Nano- and Macroscales: Organic Crystal That Exhibits Low-Temperature Molecular Motion and the Thermosalient Effect

The thermosalient effect is a rarely observed, potentially
very
useful and at the present, unpredictable mechanical response during
a phase transition that is thought to hold the potential for rapid
and clean energy conversion devoid of gaseous products. Here, we report
the serendipitous discovery of a rare instance of a thermosalient
organic solid that exhibits the effect below room temperature. The
crystals of this carbazole-based material are dynamic at both molecular
and macroscopic scales. Using variable temperature synchrotron X-ray
diffraction and variable-temperature solid-state nuclear magnetic
resonance (ssNMR), we thoroughly examined the hysteretic structural
transition in this material, emphasizing its macroscopic reconfigurability.
We discovered unexpected large-amplitude molecular oscillations in
the low-temperature phase, which challenge conventional assumptions
about salient materials. Notably, we combined 2H ssNMR
with computational modeling to reveal this dual-scale dynamism, setting
the groundwork for advancements in energy-efficient actuators, sensors,
and intelligent materials. This work might open new avenues for developing
crystalline materials that can be implemented in innovative devices
operating seamlessly across various scales.