Bridged tolanes: a twisted tale
The rotational motion of tolanes along their acetylene axis is not fully understood. What happens to the optical and electronic properties if the tolane backbone is forced into a twisted conformation? Several tethers were investigated to obtain tolanophanes, fixing the torsion angle of the two pheny...
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| Main Authors: | , , , , |
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| Format: | Article (Journal) |
| Language: | English |
| Published: |
June 17, 2014
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| In: |
The journal of organic chemistry
Year: 2014, Volume: 79, Issue: 14, Pages: 6571-6578 |
| ISSN: | 1520-6904 |
| DOI: | 10.1021/jo5010235 |
| Online Access: | Verlag, Volltext: http://dx.doi.org/10.1021/jo5010235
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| Author Notes: | Sebastian Menning, Maximilian Krämer, Andrew Duckworth, Frank Rominger, Andrew Beeby, Andreas Dreuw, and Uwe H. F. Bunz |
| Summary: | The rotational motion of tolanes along their acetylene axis is not fully understood. What happens to the optical and electronic properties if the tolane backbone is forced into a twisted conformation? Several tethers were investigated to obtain tolanophanes, fixing the torsion angle of the two phenyl rings. X-ray crystal structures revealed tether-specific torsion angles in the solid state. The absorption, emission, and excitation spectra were recorded. Twisted tethered tolane conformers showed blue-shifted absorption; emission spectra were all torsionally independent and identical. The tethered tolanes were embedded in a rigid matrix by freezing to 77 K; well-resolved emission spectra were recorded for planar tolanes, but for twisted systems unexpectedly long-lived phosphorescence was observed. How is this triplet emission explained? Quantum chemical calculations (TDDFT/cam-B3LYP/6-31G*) of the unsubstituted tolane showed that intersystem crossing (ISC) is favored with large spin-orbit coupling, which occurs when the molecular orbitals are orthogonal to each other; this is the case at the crossing of S1/T7. Also, a small energy difference between singlet and triplet states is required; we found that ISC can favorably take place at four crossings: S1/T6, S1/T7, S1/T8,9, S1/T10. |
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| Item Description: | Gesehen am 11.12.2017 |
| Physical Description: | Online Resource |
| ISSN: | 1520-6904 |
| DOI: | 10.1021/jo5010235 |