Sterically Frustrated Aromatic Enes with Various Colors Originating from Multiple Folded and Twisted Conformations in Crystal Polymorphs** |
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| Authors: | Dr Tomohiko Nishiuchi Seito Aibara Takuya Yamakado Ryo Kimura Prof Dr Shohei Saito Dr Hiroyasu Sato Prof Dr Takashi Kubo |
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| Institution: | 1. Department of Chemistry, Graduate School of Science, Osaka University, Machikaneyama, Toyonaka, Osaka, 560-0043 Japan;2. Department of Chemistry, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake, Sakyo, Kyoto, 606-8502 Japan;3. Rigaku Corporation, 3-9-12 Matsubara, Akishima, Tokyo, 196-8666 Japan |
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| Abstract: | Overcrowded ethylenes composed of 10-methyleneanthrone and two bulky aromatic rings contain a twisted carbon–carbon double (C=C) bond as well as a folded anthrone unit. As such, they are unique frustrated aromatic enes (FAEs). Various colored crystals of these FAEs, obtained in different solvents, correspond to multiple metastable conformations of the FAEs with various twist and fold angles of the C=C bond, as well as various dihedral angles of attached aryl units with respect to the C=C bond. The relationships between color and these parameters associated with conformational features around the C=C bond were elucidated in experimental and computational studies. Owing to the fact that they are separated by small energy barriers, the variously colored conformations in the FAE crystal change in response to various external stimuli, such as mechanical grinding, hydrostatic pressure and thermal heating. |
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| Keywords: | metastable structures mechanochromism overcrowded ethylene piezochromism thermochromism |
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