The [4 + 2] cycloaddition of o-quinodimethanes, generated in situ from the sultine 4,5-benzo-3,6-dihydro-1,2-oxathiin 2-oxide and its derivative, to La metal-encapsulated fullerenes, La2@C80 or La@C82, afforded the novel derivatives of endohedral metallofullerenes (3a,b, 4a,b and 5b). Molecular structures of the resulting compounds were elucidated using spectroscopic methods such as MALDI–TOF mass, optical absorption, and NMR spectroscopy. The [4 + 2] adducts of La2@C80 (3a,b, and 4a,b) and La@C82 (5b), respectively, retain diamagnetic and paramagnetic properties, as confirmed by EPR spectroscopy. Dynamic NMR measurements of 4a at various temperatures demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral metallofullerene derivatives for the use in material science.
通过从4,5-苯并-3,6-二氢-1,2-噁
硫环己烯-2-氧化物及其衍
生物生成的现场产生的o-喹诺二
甲烷的[4 + 2]环加成反应,与
镧金属封装
富勒烯La
2@C
80或La@C
82反应,形成了新颖的内囊
金属
富勒烯衍
生物(3a、b、4a、b和5b)。通过MALDI-TOF质谱、光吸收和NMR光谱等光谱方法阐明了所得化合物的分子结构。分别对La
2@C
80(3a、b和4a、b)和La@C
82(5b)的[4 + 2]加合物进行了EPR光谱确认,保留了顺磁和顺磁性质。在不同温度下对4a的动态NMR测量显示了加成物的船对船倒转。此外,与报道的五
甲基环戊二烯和La@C
82(6)的[4 + 2]环加成物相比,5b表现出显著的热稳定性。这些发现证明了苯并
硫醚的实用性,可提供热力学稳定的内囊
金属
富勒烯衍
生物,用于材料科学中的应用。