Article ; Online: Structure, NMR and Electronic Spectra of [m.n]Paracyclophanes with Varying Bridges Lengths (m, n = 2-4).
The journal of physical chemistry. A
2016 Volume 120, Issue 5, Page(s) 724–736
Abstract: ... spin coupling constants, absorption and emission properties of [m.n]paracyclophanes, m, n = 2-4 ... carbon atoms of all the [m.n]paracyclophanes in the excited state decrease compared to the ground-state ...
| Abstract | Extending our earlier studies on cyclophanes, we here report the structure, chemical shifts, spin-spin coupling constants, absorption and emission properties of [m.n]paracyclophanes, m, n = 2-4, obtained using a combination of experimental and computational techniques. Accurate values of proton chemical shifts as well as of JHH for the bridges are determined. The experimental chemical shifts, coupling constants, absorption and emission wavelengths are satisfactorily reproduced using density functional theory calculations, using both the B3LYP and ωB97X-D functionals. The geometries predicted using a functional that includes dispersion corrections (ωB97X-D) are in a better agreement with available experimental values than those obtained using the B3LYP method. Up to 8 UV-vis absorption/emission bands have been observed (or anticipated in the region below 200 nm) and assigned on the basis of quantum-chemical calculations. Optimized excited-state geometries showed that the distances between the aromatic bridgehead carbon atoms of all the [m.n]paracyclophanes in the excited state decrease compared to the ground-state geometries by ca. 0.2-0.9 Å, the largest being for [4.4]paracyclophane, though the rather large differences in the calculated emission wavelength compared to experiment cast some doubts on the accuracy of the excited-state geometries. |
|---|---|
| Language | English |
| Publishing date | 2016-02-11 |
| Publishing country | United States |
| Document type | Journal Article ; Research Support, Non-U.S. Gov't |
| ISSN | 1520-5215 |
| ISSN (online) | 1520-5215 |
| DOI | 10.1021/acs.jpca.5b12168 |
| Database | MEDical Literature Analysis and Retrieval System OnLINE |
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