Organic Chemistry

Sterically Frustrated Aromatic Enes with Various Colors Originating from Multiple Folded and Twisted Conformations in Crystal Polymorphs



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 using 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 using experimental and theoretical 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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Supplementary material

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Supporting information
Experimental Details, Synthesis of Materials, Supplementary Figures and Tables, and Charts of 1H and 13C NMR Spectra
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Cif file of 1-AO
Crystal data of 1-AO
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Cif file of 1-AD
Crystal data of 1-AD
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Cif file of 1-C6F6
Crystal data of 1-C6F6
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Cif file of 1-DH
Crystal data of 1-DH
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Cif file of 1-DMF
Crystal data of 1-DMF
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Cif file of 1-TCE
Crystal data of 1-TCE
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Cif file of 2-O_120K
Crystal data of 2-O_120K
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Cif file of 2-O_293K
Crystal data of 2-O_293K
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Cif file of 2-O_443K
Crystal data of 2-O_443K
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Cif file of 2-Y_120K
Crystal data of 2-Y_120K
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Cif file of 2-Y_293K
Crystal data of 2-Y_293K
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Cif file of 2-Y_403K
Crystal data of 2-Y_403K
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Cif file of 2-Y_0.8GPa
Crystal data of 2-Y under high pressure (0.8 GPa)
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Cif file of 2-Y_3.5GPa
Crystal data of 2-Y under high pressure (3.5 GPa)