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Crystals 2017, 7(3), 84;

A Structural Analysis of Spiropyran and Spirooxazine Compounds and Their Polymorphs

Institute of Condensed Matter and Nanosciences (IMCN), Université catholique de Louvain, 1, Place Louis Pasteur, B-1348 Louvain-la-Neuve, Belgium
Unité de Chimie Physique, Théorique et Structurale, UNamur, 61, rue de Bruxelles, B-5000 Namur, Belgium
Author to whom correspondence should be addressed.
Academic Editor: Helmut Cölfen
Received: 9 February 2017 / Revised: 27 February 2017 / Accepted: 9 March 2017 / Published: 13 March 2017
(This article belongs to the Special Issue Thermo- and Photochromic Molecular Crystals)
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In this work, crystal structures of commercially available photochromic compounds, i.e., spiropyrans and spirooxazines, were investigated by single-crystal X-ray diffraction. A total of five new structures were obtained via isothermal evaporation experiments under different conditions, namely 1,3,3-Trimethylindolino-benzopyrylospiran (I), 1,3,3-Trimethylindolinonaphtospirooxaxine (II), 1-(2-Hydroxyethyl)-3,3-dimethylindolino-6′-nitrobenzopyrylospiran (III), and 1,3,3-Trimethylindolino-8′-methoxybenzopyrylospiran (IVa and IVb). Since the basic structure of a spiropyran/-oxazine does not present typical hydrogen bond accepting and donating groups, this study illustrates the importance of additional functional groups connected to this kind of molecules to induce specific intermolecular interactions. Our results show that possible hydrogen bonding interactions are rather weak due to the high steric demand of these compounds. These results are supported by a search of the Cambridge structural database focused on related structures. View Full-Text
Keywords: spiropyran; spirooxazine; crystal engineering; photochromic compounds; crystal structure spiropyran; spirooxazine; crystal engineering; photochromic compounds; crystal structure

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Seiler, V.K.; Tumanov, N.; Robeyns, K.; Wouters, J.; Champagne, B.; Leyssens, T. A Structural Analysis of Spiropyran and Spirooxazine Compounds and Their Polymorphs. Crystals 2017, 7, 84.

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