Ab initio theoretical description of low-lying (ππ) excited states of trans-1,3,5-hexatriene using slater-type orbitals
✍ Scribed by D.A. Luippold
- Publisher
- Elsevier Science
- Year
- 1976
- Tongue
- English
- Weight
- 593 KB
- Volume
- 43
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Excitation energies and out-of-plane spatial character tz2) of the lowest nn* sinplet and triplet states of tranr-1-3&hexatricne were described as a function of various basis sets and ciectron correlation procedures. Confiration interaction (Cl) utilized all single and double excitations, (1+2)CI, arisinp within the h-system. Excitation cnergics and u*) values were 1 'Ag$O.OOeV, 33.2ai). 1 3Bu(4.11 cV, 34.1 &, 1 3Ag(5.80cV. 34.4~:). 2 'Ag(6.83cV, 35.7&.and 1 'Bu(7.40eV, 54.8 ~0). These calculations suggest that hexotriene may be the shortest polyene to evidence the na* singlet state ordering characteristic of longer polyencs such as carotenoid pigments and the visual chromophore. Implications for the photochemistry of the vitamin D field are also discussed. * Supported in part by a Harvard Scholarship (1972-74) and a grant from the William F. Milton Fund of Harvard University (1974-X). * Although the extensive butadienc calcufations of Dunning et al. [2J yielded 2 tAg(6.77 cV) < 1 tBu(7.05 ev), their fig. 1 caption noicd that from more thorough ethylene rcsuits, 1 'B, + 1 'Ag was calculated ZJ 1 eV too high, while 2 'Ag -1rAg should on!y bc high by -0.06 cV. Thus, they predicted 1 'Bu C 2 fAg for butadienc. ** A preliminar-. account of this work was presented by the author elsewhere 131.