Four isomeric di-6-oxoverdazyl diradicals connected at their N(1) or C(3) positions with either 1,3- or 1,4-phenylene linkers were obtained and characterized by spectroscopic, electrochemical, magnetic, and structural methods. These results were compared to those for the corresponding 6-oxoverdazyl monoradicals. UV–vis spectroscopy demonstrated that only the N(1)-connected para-through-benzene diradical has a distinct spectrum with significant bathochromic and hypsochromic shifts relative to the remaining species. Electrochemical analysis revealed two one-electron reduction processes in all diradiacals, while only the N(1)-connected para-through-benzene diradical exhibits two one-electron oxidation processes separated by 0.10 V. Variable temperature EPR measurements in polystyrene solid solutions gave negative mean exchange interaction energies J for all diradicals, suggesting the dominance of conformers with significant intramolecular antiferromagnetic interactions for the meta-through-benzene isomers. DFT calculations predict a small preference for the triplet state with the ΔE_S–T of about 0.25 kcal mol^–1 for both meta-through-benzene connected diradicals.

中文翻译：

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6-Oxoverdazyl Diradicals 中的电子和磁相互作用：重新审视通过 N(1) 与 C(3) 的连接

获得了四种异构二-6-氧代过达唑双自由基，其 N(1) 或 C(3) 位与 1,3- 或 1,4-亚苯基连接体连接，并通过光谱、电化学、磁性和结构方法进行了表征。将这些结果与相应的 6-氧代二氮基单自由基的结果进行比较。紫外可见光谱表明，只有 N(1) 连接的对通苯双自由基具有独特的光谱，相对于其余物种具有显着的红移和低色位移。电化学分析显示所有双自由基中都有两个单电子还原过程，而只有 N(1) 连接的对位苯双自由基表现出两个相距 0.10 V 的单电子氧化过程。聚苯乙烯固溶体中的变温 EPR 测量给出了负值所有双自由基的平均交换相互作用能J ，表明间位苯异构体中具有显着分子内反铁磁相互作用的构象异构体占主导地位。 DFT 计算预测，对于间位通过苯连接的双自由基，其 Δ E _S–T约为 0.25 kcal mol ^–1的三线态具有较小的偏好。