The synthesis of a doubly tert-butylated spirobiradical, 2,7-di-tert-butyl-9,9′(10H,10′H)-spirobiacridine-10,10′-dioxyl is reported. The X-ray diffraction study clarified that the two dihydroacridine skeletons were fused at the sp³-carbon atom affording a cruciform structure. The frozen-solution electron spin resonance spectrum showed a typical zero-field-splitting pattern. The magnetic study revealed the presence of an intramolecular ferromagnetic interaction with 2J/k_B = +22.3(5) K. The density-functional-theory calculation results are entirely consistent with the experimental results. After comparison with the known unsubstituted spirobiradical, we can conclude that tert-butylation is a useful method to reduce the intermolecular interaction without breaking the degeneracy of the singly occupied molecular orbitals.

合成的双叔-butylated spirobiradical，2,7-二-叔丁基- 9,9'（10 ħ，10' ħ）-spirobiacridine-10,10'- dioxyl报道。X-射线衍射研究表明，两个二氢ac啶骨架在sp ^3-碳原子上融合，形成十字形结构。冷冻溶液电子自旋共振谱显示出典型的零场分裂模式。磁性研究表明分子内铁磁相互作用存在2 J / k _B = +22.3（5）K。密度泛函理论的计算结果与实验结果完全一致。与已知的未取代螺双自由基比较后，我们可以得出结论，叔丁基化是减少分子间相互作用而不破坏单个占据的分子轨道的简并性的有用方法。