Photochemical E/Z isomerization of aryl-substituted methanimines. AM1-CI potential energy curves along the CN double bond twisting and the N atom in-plane inversion |
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Authors: | Katsunori Segawa Osamu Kikuchi Tatsuo Arai Katsumi Tokumaru |
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Affiliation: | a Department of Chemistry, University of Tsukuba Tsukuba 305 Japan |
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Abstract: | Potential energy curves of aryl-substituted methanimines along the C = N bond twisting and the in-plane inversion of the N atom were obtained by AM1-SDCI calculations, and the photochemical E/Z isomerization paths were elucidated. An aromatic group introduced at the C atom of the C = N group has little effect on the S0 surface for the inversion and rotation paths, while it has a significant effect on the shape of the T1 curve along the rotation path. It is suggested that phenylmethanimine and 2-anthrylmethanimine undergo photoisomerization by the rotation mechanism. The methoxy group introduced at the N atom raises the inversion barrier on the S0 state, while it lowers the 90°-twistedT1 energy. TheT1 potential energy curves of N-methoxy-1-phenylethanimine and N-methoxy-1-(2-anthryl)ethanimine indicate that the former undergoes a two-way isomerization and the latter a one-way isomerization by the rotation mechanism, which is in accordance with experiment. |
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