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- Publisher Website: 10.1021/jacs.4c03815
- Scopus: eid_2-s2.0-85193004860
- PMID: 38720418
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Article: Nonalternant Nanographenes Containing N-Centered Cyclopenta[ef]heptalene and Aza[7]Helicene Units
Title | Nonalternant Nanographenes Containing N-Centered Cyclopenta[ef]heptalene and Aza[7]Helicene Units |
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Authors | |
Issue Date | 8-May-2024 |
Publisher | American Chemical Society |
Citation | Journal of the American Chemical Society, 2024, v. 146, n. 23, p. 16161-16172 How to Cite? |
Abstract | Introducing helical subunits into negatively curved π-systems has a significant effect on both the molecular geometry and photophysical properties; however, the synthesis of these helical π-systems embedded with nonbenzenoid subunits remains challenging due to the high strain deriving from both the curvature and helix. Here, we report a family of nonalternant nanographenes containing a nitrogen (N)-doped cyclopenta[ef]heptalene unit. Among them, CPH-2 and CPH-3 can be viewed as hybrids of benzoannulated cyclopenta[ef]heptalene and aza[7]helicene. The crystal structures revealed a saddle geometry for CPH-1, a saddle-helix hybrid for CPH-2, and a twist-helix hybrid for CPH-3. Experimental measurements and theoretical calculations indicate that the saddle moieties in CPHs undergo flexible conformational changes at room temperature, while the aza[7]helicene subunit exhibits a dramatically increased racemization energy barrier (78.2 kcal mol-1 for CPH-2, 143.2 kcal mol-1 for CPH-3). The combination of the nitrogen lone electron pairs of the N-doped cyclopenta[ef]heptalene unit with the twisted helix fragments results in rich photophysics with distinctive fluorescence and phosphorescence in CPH-1 and CPH-2 and the similar energy fluorescence and phosphorescence in CPH-3. Both enantiopure CPH-2 and CPH-3 display distinct circular dichroism (CD) signals in the UV-vis range. Notably, compared to the reported fully π-extended helical nanographenes, CPH-3 exhibits excellent chiroptical properties with a |gabs| value of 1.0 × 10-2 and a |glum| value of 7.0 × 10-3; these values are among the highest for helical nanographenes. |
Persistent Identifier | http://hdl.handle.net/10722/348540 |
ISSN | 2023 Impact Factor: 14.4 2023 SCImago Journal Rankings: 5.489 |
DC Field | Value | Language |
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dc.contributor.author | Qiu, Shuhai | - |
dc.contributor.author | Valdivia, Abel Cárdenas | - |
dc.contributor.author | Zhuang, Weiwen | - |
dc.contributor.author | Hung, Faan Fung | - |
dc.contributor.author | Che, Chi Ming | - |
dc.contributor.author | Casado, Juan | - |
dc.contributor.author | Liu, Junzhi | - |
dc.date.accessioned | 2024-10-10T00:31:26Z | - |
dc.date.available | 2024-10-10T00:31:26Z | - |
dc.date.issued | 2024-05-08 | - |
dc.identifier.citation | Journal of the American Chemical Society, 2024, v. 146, n. 23, p. 16161-16172 | - |
dc.identifier.issn | 0002-7863 | - |
dc.identifier.uri | http://hdl.handle.net/10722/348540 | - |
dc.description.abstract | Introducing helical subunits into negatively curved π-systems has a significant effect on both the molecular geometry and photophysical properties; however, the synthesis of these helical π-systems embedded with nonbenzenoid subunits remains challenging due to the high strain deriving from both the curvature and helix. Here, we report a family of nonalternant nanographenes containing a nitrogen (N)-doped cyclopenta[ef]heptalene unit. Among them, CPH-2 and CPH-3 can be viewed as hybrids of benzoannulated cyclopenta[ef]heptalene and aza[7]helicene. The crystal structures revealed a saddle geometry for CPH-1, a saddle-helix hybrid for CPH-2, and a twist-helix hybrid for CPH-3. Experimental measurements and theoretical calculations indicate that the saddle moieties in CPHs undergo flexible conformational changes at room temperature, while the aza[7]helicene subunit exhibits a dramatically increased racemization energy barrier (78.2 kcal mol-1 for CPH-2, 143.2 kcal mol-1 for CPH-3). The combination of the nitrogen lone electron pairs of the N-doped cyclopenta[ef]heptalene unit with the twisted helix fragments results in rich photophysics with distinctive fluorescence and phosphorescence in CPH-1 and CPH-2 and the similar energy fluorescence and phosphorescence in CPH-3. Both enantiopure CPH-2 and CPH-3 display distinct circular dichroism (CD) signals in the UV-vis range. Notably, compared to the reported fully π-extended helical nanographenes, CPH-3 exhibits excellent chiroptical properties with a |gabs| value of 1.0 × 10-2 and a |glum| value of 7.0 × 10-3; these values are among the highest for helical nanographenes. | - |
dc.language | eng | - |
dc.publisher | American Chemical Society | - |
dc.relation.ispartof | Journal of the American Chemical Society | - |
dc.title | Nonalternant Nanographenes Containing N-Centered Cyclopenta[ef]heptalene and Aza[7]Helicene Units | - |
dc.type | Article | - |
dc.identifier.doi | 10.1021/jacs.4c03815 | - |
dc.identifier.pmid | 38720418 | - |
dc.identifier.scopus | eid_2-s2.0-85193004860 | - |
dc.identifier.volume | 146 | - |
dc.identifier.issue | 23 | - |
dc.identifier.spage | 16161 | - |
dc.identifier.epage | 16172 | - |
dc.identifier.eissn | 1520-5126 | - |
dc.identifier.issnl | 0002-7863 | - |