Issue 4, 2023

A theoretical framework for the design of molecular crystal engines

Abstract

Photomechanical molecular crystals have garnered attention for their ability to transform light into mechanical work, but difficulties in characterizing the structural changes and mechanical responses experimentally have hindered the development of practical organic crystal engines. This study proposes a new computational framework for predicting the solid-state crystal-to-crystal photochemical transformations entirely from first principles, and it establishes a photomechanical engine cycle that quantifies the anisotropic mechanical performance resulting from the transformation. The approach relies on crystal structure prediction, solid-state topochemical principles, and high-quality electronic structure methods. After validating the framework on the well-studied [4 + 4] cycloadditions in 9-methyl anthracene and 9-tert-butyl anthracene ester, the experimentally-unknown solid-state transformation of 9-carboxylic acid anthracene is predicted for the first time. The results illustrate how the mechanical work is done by relaxation of the crystal lattice to accommodate the photoproduct, rather than by the photochemistry itself. The large ∼107 J m−3 work densities computed for all three systems highlight the promise of photomechanical crystal engines. This study demonstrates the importance of crystal packing in determining molecular crystal engine performance and provides tools and insights to design improved materials in silico.

Graphical abstract: A theoretical framework for the design of molecular crystal engines

Supplementary files

Article information

Article type
Edge Article
Submitted
06 Oct 2022
Accepted
19 Dec 2022
First published
21 Dec 2022
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY-NC license

Chem. Sci., 2023,14, 937-949

A theoretical framework for the design of molecular crystal engines

C. J. Cook, W. Li, B. F. Lui, T. J. Gately, R. O. Al-Kaysi, L. J. Mueller, C. J. Bardeen and G. J. O. Beran, Chem. Sci., 2023, 14, 937 DOI: 10.1039/D2SC05549J

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