TY - JOUR
T1 - [8]Cyclo-para-phenylmethine as A Super-Cyclooctatetraene: Dynamic Behavior, Global Aromaticity, and Open-Shell Diradical Character in The Neutral and Dicationic States
AU - Li, Zhengtao
AU - Hou, Xudong
AU - Han, Yi
AU - Fan, Wei
AU - Ni, Yong
AU - Zhou, Qifeng
AU - Zhu, Jun
AU - Wu, Shaofei
AU - Huang, Kuo-Wei
AU - Wu, Jishan
N1 - KAUST Repository Item: Exported on 2022-09-14
Acknowledgements: J.W. acknowledges financial support from MOE Tier 2 grant (MOE2019-T2-1-030), NRF Investigatorship (NRF-NRFI05-2019-0005)and Applied Materials-NUS Advanced Materials Corporate Lab(I1801E0022).
PY - 2022/8/25
Y1 - 2022/8/25
N2 - An [8]cyclo-para-phenylmethine derivative ([8]CPPM-Mes) was synthesized. X-ray analysis revealed a tub-shaped geometry similar to the cyclooctatetraene, with alternating benzenoid/quinoid structure. Variable-temperature NMR measurements disclosed a slow valence tautomerization process with an interconversion energy barrier of about 11.7 kcal/mol at coalescence temperature (273 K), and two more lower-barrier dynamic processes involving flipping of the 1,4-phenyl rings on the backbone and rotation of the mesityl substituents. Its dication ([8]CPPM-Mes2+) adopts a bowl-like geometry with a smaller depth of the cavity, and a slow bowl inversion process was observed by dynamic NMR. The bond lengths of the benzenoid/quinoid rings are more averaged via electron delocalization and the molecule shows global aromaticity, which was further validated by NMR and theoretical analysis. [8]CPPM-Mes2+ exhibits open-shell diradical character with a small singlet-triplet energy gap(-1.8 kcal/mol).
AB - An [8]cyclo-para-phenylmethine derivative ([8]CPPM-Mes) was synthesized. X-ray analysis revealed a tub-shaped geometry similar to the cyclooctatetraene, with alternating benzenoid/quinoid structure. Variable-temperature NMR measurements disclosed a slow valence tautomerization process with an interconversion energy barrier of about 11.7 kcal/mol at coalescence temperature (273 K), and two more lower-barrier dynamic processes involving flipping of the 1,4-phenyl rings on the backbone and rotation of the mesityl substituents. Its dication ([8]CPPM-Mes2+) adopts a bowl-like geometry with a smaller depth of the cavity, and a slow bowl inversion process was observed by dynamic NMR. The bond lengths of the benzenoid/quinoid rings are more averaged via electron delocalization and the molecule shows global aromaticity, which was further validated by NMR and theoretical analysis. [8]CPPM-Mes2+ exhibits open-shell diradical character with a small singlet-triplet energy gap(-1.8 kcal/mol).
UR - http://hdl.handle.net/10754/680537
UR - https://onlinelibrary.wiley.com/doi/10.1002/anie.202210697
U2 - 10.1002/anie.202210697
DO - 10.1002/anie.202210697
M3 - Article
C2 - 36008354
SN - 1433-7851
JO - Angewandte Chemie (International ed. in English)
JF - Angewandte Chemie (International ed. in English)
ER -