Journal
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
Volume -, Issue -, Pages -Publisher
WILEY-V C H VERLAG GMBH
DOI: 10.1002/anie.202313074
Keywords
Azides; Cycloaddition; Endohedral Fullerenes; Fullerenes; Structure Elucidation
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In this study, the divergent additions of 2,2'-diazidobiphenyls to C-60 and Sc3N@I-h-C-80 were reported. The unexpected cascade reaction led to the formation of various azafulleroids, and their molecular structures were determined by single-crystal X-ray diffraction analyses. Furthermore, these azafulleroids exhibited improved power conversion efficiencies when used in organic solar cells.
Herein, we report divergent additions of 2,2 '-diazidobiphenyls to C-60 and Sc3N@I-h-C-80. In stark contrast to that of the previously reported bis-azide additions, the unexpected cascade reaction leads to the dearomative formation of azafulleroids 2 fused with a 7-6-5-membered ring system in the case of C-60. In contrast, the corresponding reaction with Sc3N@I-h-C-80 switches to the C-H insertion pathway, thereby resulting in multiple isomers, including a carbazole-derived [6,6]-azametallofulleroid 3 and a [5,6]-azametallofulleroid 4 and an unusual 1,2,3,6-tetrahydropyrrolo[3,2-c]carbazole-derived metallofullerene 5, whose molecular structures have been unambiguously determined by single-crystal X-ray diffraction analyses. Among them, the addition type of 5 is observed for the first time in all reported additions of azides to fullerenes. Furthermore, unexpected isomerizations from 3 to 5 and from 4 to 5 have been discovered, providing the first examples of the isomerization of an azafulleroid to a carbazole-derived fullerene rather than an aziridinofullerene. In particular, the isomerism of the [5,6]-isomer 4 to the [5,6]-isomer 5 is unprecedented in fullerene chemistry, contradicting the present understanding that isomerization generally occurs between [5,6]- and [6,6]-isomers. Control experiments have been carried out to rationalize the reaction mechanism. Furthermore, representative azafulleroids have been applied in organic solar cells, thereby resulting in improved power conversion efficiencies.
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