Intramolecular proton transfer in the ground and the two lowest-lying singlet excited states of 1-amino-3-propenal and related species
The potential energy surfaces of the ground state and the two lowest-lying singlet excited states of 1-amino-3-propenal, the cyclic complex of 1-amino-3-propenal with water, and salicylaldimine (2-iminomethylphenol) have been investigated theoretically along the proton transfer (PT) reaction coordin...
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Published in | Chemical physics Vol. 234; no. 1; pp. 1 - 19 |
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Main Authors | , , |
Format | Journal Article |
Language | English |
Published |
Elsevier B.V
15.08.1998
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Online Access | Get full text |
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Summary: | The potential energy surfaces of the ground state and the two lowest-lying singlet excited states of 1-amino-3-propenal, the cyclic complex of 1-amino-3-propenal with water, and salicylaldimine (2-iminomethylphenol) have been investigated theoretically along the proton transfer (PT) reaction coordinate. All these three systems have in common the same intramolecular H-bond through an OCCCN backbone. It has been found that the PT in the ππ
* excited state of 1-amino-3-propenal has a very small energy barrier, which disappears after introduction of dynamic correlation, providing a pathway for an ultrafast photoinduced PT. The energy barriers for the PT processes of the ground and nπ
* states increase when the transfer of the proton is carried out through a water molecule bridge. Calculations reveal two main differences between 1-amino-3-propenal and salicylaldimine: (a) while in 1-amino-3-propenal the keto tautomer is the most stable in all the electronic states studied, the ground state of salicylaldimine favors the enol structure; (b) the near degeneracy between the nπ
* and ππ
* excited singlet states in 1-amino-3-propenal is lost in salicylaldimine, for which the ππ
* excited singlet state is stabilized as compared to the nπ
* state. These results suggest that care must be taken in generalizing to larger molecules the conclusions obtained with models as small as 1-amino-3-propenal. |
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ISSN: | 0301-0104 |
DOI: | 10.1016/S0301-0104(98)00165-7 |