Off-campus UNL users: To download campus access dissertations, please use the following link to log into our proxy server with your NU ID and password. When you are done browsing please remember to return to this page and log out.

Non-UNL users: Please talk to your librarian about requesting this dissertation through interlibrary loan.

Synthesis of Stable Double Helical Diradical Dications and Nitronyl Nitroxide Blatter-Based Di- and Tri-Radicals

Chan Shu, University of Nebraska - Lincoln


This dissertation is mainly focused on the design and synthesis of stable highspin (S ≥ 1) N-radicals: the first project is designed based on the π-conjugated double bis[5]diazahelicenes and the second project is designed based on the stable nitronyl nitroxide and 1,2,4-benzotriazinyl (Blatter) radicals. The design, synthesis, and the properties of the molecules, characterized by NMR, EPR, UV-vis-NIR spectroscopies, SQUID magnetometry, X-ray crystallography and thermogravimetric analysis, are described. The π-systems of helicenes enhance the stabilization of radicals. Spin filtering effect is discovered in both radicals and helicenes. Thus, high-spin helical diradicals are attractive to the discovery of spin filters. The challenge is to design stable helical diradicals with large singlet-triplet energy gap (ΔEST). In the first project, the first chiral air-stable high-spin diradical dication of D2-symmetric conjoined bis[5]diazahelicene, with ΔEST = 0.3 kcal mol-1, was synthesized, which possesses a half-life of more than 2 weeks at ambient conditions in the presence of excess oxidant. Additionally, a C2- symmetric conjoined bis[5]diazahelicene was synthesized. After methylation, its radical cation and diradical dication were generated with different oxidants. The radical cation of C2-symmetric dimethyl-conjoined bis[5]diazahelicene was isolated as crystal, which owns an onset of decomposition at 203 °C based on the thermogravimetric analysis. High-spin radicals (S ≥ 1) with great stability are important to the further applications. However, only limited stable high-spin di- and tri-radicals are reported. In the second project, a high-spin triradical composed of Blatter radical and nitronyl nitroxide, with doublet-quartet energy gap ΔEDQ ≈ 0.2 – 0.3 kcal mol-1, was synthesized by radical-radical Pd(0)-catalyzed cross-coupling reaction. The triradical possesses great thermal stability, having an onset of decomposition at 166 °C based on the thermogravimetric analysis. The triradical was used to form the thin film under control conditions. Moreover, utilizing the Pd(0)-catalyzed cross-coupling reaction, a carbazole-nitronyl nitroxide-Blatter diradical was synthesized to investigate its fluorescence properties.

Subject Area


Recommended Citation

Shu, Chan, "Synthesis of Stable Double Helical Diradical Dications and Nitronyl Nitroxide Blatter-Based Di- and Tri-Radicals" (2022). ETD collection for University of Nebraska - Lincoln. AAI29323637.