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Bridging photochemistry and photomechanics with NMR crystallography: the molecular basis for the macroscopic expansion of an anthracene ester nanorod.

Authors :
Chalek KR
Dong X
Tong F
Kudla RA
Zhu L
Gill AD
Xu W
Yang C
Hartman JD
Magalhães A
Al-Kaysi RO
Hayward RC
Hooley RJ
Beran GJO
Bardeen CJ
Mueller LJ
Source :
Chemical science [Chem Sci] 2020 Oct 30; Vol. 12 (1), pp. 453-463. Date of Electronic Publication: 2020 Oct 30.
Publication Year :
2020

Abstract

Crystals composed of photoreactive molecules represent a new class of photomechanical materials with the potential to generate large forces on fast timescales. An example is the photodimerization of 9- tert -butyl-anthracene ester ( 9TBAE ) in molecular crystal nanorods that leads to an average elongation of 8%. Previous work showed that this expansion results from the formation of a metastable crystalline product. In this article, it is shown how a novel combination of ensemble oriented-crystal solid-state NMR, X-ray diffraction, and first principles computational modeling can be used to establish the absolute unit cell orientations relative to the shape change, revealing the atomic-resolution mechanism for the photomechanical response and enabling the construction of a model that predicts an elongation of 7.4%, in good agreement with the experimental value. According to this model, the nanorod expansion does not result from an overall change in the volume of the unit cell, but rather from an anisotropic rearrangement of the molecular contents. The ability to understand quantitatively how molecular-level photochemistry generates mechanical displacements allows us to predict that the expansion could be tuned from +9% to -9.5% by controlling the initial orientation of the unit cell with respect to the nanorod axis. This application of NMR-assisted crystallography provides a new tool capable of tying the atomic-level structural rearrangement of the reacting molecular species to the mechanical response of a nanostructured sample.<br />Competing Interests: There are no conflicts to declare.<br /> (This journal is © The Royal Society of Chemistry.)

Details

Language :
English
ISSN :
2041-6520
Volume :
12
Issue :
1
Database :
MEDLINE
Journal :
Chemical science
Publication Type :
Academic Journal
Accession number :
34163608
Full Text :
https://doi.org/10.1039/d0sc05118g