The fundamental relationship between structure and diradical character is important for the development of open-shell diradicaloid-based materials. In this work, we synthesized two structural isomers bearing a 2,6-naphthoquinodimethane or a 1,5-naphthoquinodimethane bridge and demonstrated that their diradical characters and chemical reactivity are quite different. The mesityl-or pentafluorophenyl-substituted octazethrene derivatives OZ-M/OZ-F and their isomer OZI-M (with mesityl substituents) were synthesized via an intramolecular Friedel-Crafts alkylation followed by oxidative dehydrogenation strategy from the key building blocks 4 and 11. Our detailed experimental and theoretical studies showed that both isomers have an open-shell singlet ground state with a remarkable diradical character (y0 = 0.35 and 0.34 for OZ-M and OZ-F, and y0 = 0.58 for OZI-M). Compounds OZ-M and OZ-F have good stability in an ambient environment, while OZI-M has high reactivity and can be easily oxidized to a dioxo product 15, which can be correlated to their different diradical characters. Additionally, we investigated the physical properties of OZ-M, OZ-F, and 15.
Bibliographical noteFunding Information:
J.W. acknowledges financial support from the MOE Tier 3 Programme (MOE2014-T3-1-004), Tier 2 grant (MOE2014-T2-1-080), and A?STAR JCO grant (1431AFG100). This work at Yonsei University was supported by the Global Frontier R&D Program on Center for Multiscale Energy System funded by the National Research Foundation under the Ministry of Science, ICT & Future, Korea (NRF-2014M3A6A7060583). We thank Dr. Tan Geok Kheng and Dr. Bruno Donnadieu for the crystallographic analysis.
© 2016 American Chemical Society.
All Science Journal Classification (ASJC) codes
- Organic Chemistry