Issue 34, 2021

Effect of halogen substitution on energies and dynamics of reversible photomechanical crystals based on 9-anthracenecarboxylic acid

Abstract

9-Anthracene carboxylic acid derivatives comprise a family of thermally reversible photomechanical molecular crystals. The photomechanical response relies on a [4 + 4] photodimerization followed by dissociation that occurs on timescales of seconds to minutes. A combined theoretical and experimental investigation is undertaken to better understand how chemical modification of the anthracene core influences energetics of both the isolated molecule and the crystal lattice. We use both density functional theory and dispersion-corrected Moller–Plesset perturbation theory computational methods to establish orbital energies, photodimerization reaction energies, and lattice energies for a set of substituted 9-anthracene carboxylic acid molecules. The calculations reveal that steric interactions play a dominant role in the ability to form photodimers and indicate an energetic threshold of 80–90 kJ per mole for the dimerization reaction. Examination of intermolecular bonding in a subset of fluorinated 9ACs revealed the absence of H⋯F intermolecular bond formation and energy differences that can explain observed trends in the dissociation kinetics and mechanical reset times. Fluorescence recovery after photobleaching experiments shows that the photodimer dissociation kinetics depend on the amount of initial photodimer, preventing a straightforward correlation between halogen atom substitution and dissociation rates using the Bell–Evans–Polanyi principle. The results clarify how molecular structure affects intermolecular interactions and photoreactivity in this family of molecular crystals, but the origin of the complex photodimer dissociation dynamics remains an open question.

Graphical abstract: Effect of halogen substitution on energies and dynamics of reversible photomechanical crystals based on 9-anthracenecarboxylic acid

Supplementary files

Article information

Article type
Paper
Submitted
25 Jan 2021
Accepted
03 Pha 2021
First published
05 Pha 2021

CrystEngComm, 2021,23, 5931-5943

Author version available

Effect of halogen substitution on energies and dynamics of reversible photomechanical crystals based on 9-anthracenecarboxylic acid

T. J. Gately, W. Sontising, C. J. Easley, I. Islam, R. O. Al-Kaysi, G. J. O. Beran and C. J. Bardeen, CrystEngComm, 2021, 23, 5931 DOI: 10.1039/D1CE00846C

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements