Issue 46, 2015

A single-crystal-to-single-crystal Diels–Alder reaction with mixed topochemical and topotactic behaviour

Abstract

Electron donor/acceptor (EDA) interactions have been found to be very useful in engineering reactive heteromolecular crystals, but few examples have been reported in the literature. By utilising EDA interactions, crystals of charge-transfer (CT) complexes were formed with bis(N-allylimino)-1,4-dithiin as the electron acceptor and 9-bromoanthracene as the electron donor. The CT complex crystallised in the monoclinic P21/n space group with the crystal structure consisting of stacks of alternating electron donor and acceptor molecules in a 1 : 1 ratio. These crystals are able to undergo a solid-state Diels–Alder reaction with bis(N-allylimino)-1,4-dithiin as the dienophile and 9-bromoanthracene as the diene. Examination of close contacts indicates that the diene can theoretically react with the dienophile above or below it within a stack as the reaction distances are less than 3.5 Å in both directions. A single crystal was selected and allowed to react at 30 °C, was analysed at various states of conversion by single-crystal X-ray diffraction, and was found to react by approximately 10% every 6 days, with the reaction occurring in a single direction along the CT stack axis. The solid-state reaction creates a void space which leads to a molecular conformational change within the crystal. Consequently, the single crystal started to show significant signs of deterioration after approximately 28% conversion but remained intact upon further reaction and was found to anneal as 100% conversion was approached, leading to the formation of new intermolecular interactions not present in the starting crystal. The solid-state reaction occurs topochemically when fewer than 28% or more than 80% of the molecules have reacted, with minimal motion during the reaction. In the conversion range of 28–80%, the reaction occurs in an almost topotactic manner with significant molecular motion and associated crystal deterioration.

Graphical abstract: A single-crystal-to-single-crystal Diels–Alder reaction with mixed topochemical and topotactic behaviour

Supplementary files

Article information

Article type
Paper
Submitted
04 Jul 2015
Accepted
20 Aug 2015
First published
10 Sep 2015
This article is Open Access
Creative Commons BY-NC license

CrystEngComm, 2015,17, 8933-8945

Author version available

A single-crystal-to-single-crystal Diels–Alder reaction with mixed topochemical and topotactic behaviour

S. Khorasani, D. S. Botes, M. A. Fernandes and D. C. Levendis, CrystEngComm, 2015, 17, 8933 DOI: 10.1039/C5CE01301A

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, 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 commercial 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