Structural Transformations in Crystals Induced by Radiation and Pressure. Part 10. The Crystallographic Picture of Photochemical Behaviour of bi(anthracene-9,10-dimethylene) under High Pressure

Julia Bąkowicz,Ilona Turowska-Tyrk

doi:10.3390/cryst10111031

Julia Bąkowicz, Ilona Turowska-Tyrk

Open Access

https://doi.org/10.3390/cryst10111031

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Abstract

The results of the monitoring of the [4 + 4] photocycloaddition reaction path in single crystals of bi(anthracene-9,10-dimethylene) at high pressure are presented. The crystal structures for several steps of the phototransformation at 0.3 GPa and 1.0 GPa were determined and analysed. The applied high pressure did not halt the photochemical reaction and almost 100% of the product molecules were obtained, although the reaction was very slowly reversible similarly to that of ambient conditions. During the crystal phototransformation the intramolecular geometry, molecular orientation and intermolecular interactions of the reactant changed more and more towards the values observed for the product. The initial increase in the unit cell volume brought about by the photochemical reaction was diminished by high pressure. High pressure itself did not significantly influence the intramolecular geometry of the reactant and product molecules, but it influenced the intermolecular interactions.

Highlights

Mechanochemistry is the broad field of research where external mechanical force is used to induce the breaking of intramolecular chemical bonds, which is followed subsequently by a chemical reaction [1]
The [4 + 4] photocycloaddition in single crystals of (1) occurs in ambient conditions as is known from the literature [5], and at high pressure, as is demonstrated by the studies presented in this paper
We monitored the course of this reaction by X-ray structure analysis to almost 100% of the reaction progress for two different values of high pressure: 0.3 GPa and 1.0 GPa

Summary

Introduction

Mechanochemistry is the broad field of research where external mechanical force is used to induce the breaking of intramolecular chemical bonds, which is followed subsequently by a chemical reaction [1]. The mechanical force can be generated inter alia by isotropic hydrostatic pressure [2,3]. The mechanochemical approach was applied to a variety of compounds and reactions [1,4]. Molecules of bi(anthracene-9,10-dimethylene), (1), are sensitive to visible light and undergo the intramolecular [4 + 4] photocycloaddition in solution and solid state [5,6,7,8,9]. The molecules of the photoproduct in a crystalline state slowly convert back to the reactant during ca. The molecules of the photoproduct in a crystalline state slowly convert back to the reactant during ca. 40-days in ambient conditions [5]

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