Structural dynamics of photoinduced molecular switching in the solid state

• Published in: Acta crystallographica. Section A, Foundations of crystallography Vol. 66; no. 2; pp. 189 - 197
• Main Authors: Cailleau, Hervé, Lorenc, Maciej, Guérin, Laurent, Servol, Marina, Collet, Eric, Buron-Le Cointe, Marylise
• Format: Journal Article
• Language: English
• Published: 5 Abbey Square, Chester, Cheshire CH1 2HU, England International Union of Crystallography 01.03.2010; Wiley Subscription Services, Inc
• Subjects: Chemical Sciences; Condensed Matter; Diffraction; Kinetics; Lasers; Material chemistry; Materials Science; molecular switching; photoinduced transformation; Physics; Solid state physics; time-resolved diffraction; time-resolved diffraction; photoinduced transformation; molecular switching
• ISSN: 0108-7673; 1600-5724; 2053-2733
• DOI: 10.1107/S0108767309051046

Fast and ultra‐fast time‐resolved diffraction is a fantastic tool for directly observing the structural dynamics of a material rearrangement during the transformation induced by an ultra‐short laser pulse. The paper illustrates this ability using the dynamics of photoinduced molecular switching in the solid state probed by 100 ps X‐ray diffraction. This structural information is crucial for establishing the physical foundations of how to direct macroscopic photoswitching in materials. A key feature is that dynamics follow a complex pathway from molecular to material scales through a sequence of processes. Not only is the pathway indirect, the nature of the dynamical processes along the pathway depends on the timescale. This dictates which types of degrees of freedom are involved in the subsequent dynamics or kinetics and which are frozen or statistically averaged. We present a recent investigation of the structural dynamics in multifunctional spin‐crossover materials, which are prototypes of molecular bistability in the solid state. The time‐resolved X‐ray diffraction results show that the dynamics span from subpicosecond molecular photoswitching followed by volume expansion (on a nanosecond timescale) and additional thermoswitching (on a microsecond timescale).