ground-state singlet with a thermally accessible triplet at ca. 4 cm^(-1) higher in energy with a conformational dependence of intramolecular exchange in solution. This coupling may present evidence for spiroconjugation as an exchange pathway. Density functional calculations (B3/6-311G(D)) have been performed to investigate this possibility.
螺共轭
硝酰基氮氧双自由基,6,6'-(4,4,5,5-tetramethylimidazolidine-3-oxide-1-oxyl)-3,3,3',3'-tetramethyl-1,1'-spirobindane ( 1),已通过功能化 3,3,3',3'-四甲基-1,1'-螺双
茚烷骨架,然后进行 Ullman 缩合和随后的氧化制备。双自由基在单斜空间群 C2/c 中结晶,在尺寸为 a = 24.861(10) A、b = 12.129(3) A 和 c = 12.258(6) A 的晶胞中有四个分子。 X 射线分析蓝板单晶显示
硝酰基硝基氧部分和芳香环之间的二面角为 28°,分子内通过空间自由基的距离为 8.25 和 10.11 A。在固态下,摩尔磁化率的温度依赖性显示出反
铁磁性相互作用。这些相互作用最适合使用配对模型,提供值 J = -4.0 cm^(-1) 其中 J 是出现在自旋哈密顿量