Rajca Andrzej, Shiraishi Kouichi, Vale Matthew, Han Hongxian, Rajca Suchada
Department of Chemistry, University of Nebraska, Lincoln, Nebraska 68588-0304, USA.
J Am Chem Soc. 2005 Jun 29;127(25):9014-20. doi: 10.1021/ja052002v.
Hydrocarbon diradical 1, a new stable, 3-fold symmetric analogue of trimethylenemethane (TMM) with no heteroatom perturbation, is prepared and studied. Such diradicals should provide new building blocks for high-spin hydrocarbon polyradicals with very strong net ferromagnetic coupling. Magnetic studies (SQUID) and EPR spectroscopy indicate that 1 in tetrahydrofuran-d8 (THF-d8) possesses a triplet (S = 1) ground state, with strong ferromagnetic coupling. After annealing at room temperature, the EPR spectra of 1 (approximately 0.02 M in frozen THF-d8) consist of a single narrow resonance (deltaH(pp) < 1 G), and intermolecular antiferromagnetic coupling is increased by 1 order of magnitude. This behavior is consistent with the presence of exchange narrowing, thus suggesting aggregation of 1 in THF-d8. Blue solutions of 1 in THF-d8 possess a strong UV-vis absorption band at lambda(max) approximately 640 nm. Diradical 1 in THF-d8 is stable (or persistent) at room temperature, with no detectable decomposition for at least 2 days.
制备并研究了碳氢双自由基1，它是三亚甲基甲烷（TMM）的一种新型稳定的、无杂原子干扰的三重对称类似物。这种双自由基应为具有非常强的净铁磁耦合的高自旋碳氢多自由基提供新的结构单元。磁性研究（超导量子干涉仪）和电子顺磁共振光谱表明，在氘代四氢呋喃-d8（THF-d8）中的1具有三重态（S = 1）基态，具有强铁磁耦合。在室温下退火后，1（在冷冻的THF-d8中约为0.02 M）的电子顺磁共振光谱由单个窄共振组成（δH(pp) < 1 G），分子间反铁磁耦合增加了1个数量级。这种行为与交换变窄的存在一致，因此表明1在THF-d8中发生了聚集。1在THF-d8中的蓝色溶液在λ(max)约640 nm处具有很强的紫外-可见吸收带。1在THF-d8中在室温下是稳定的（或持久的），至少2天没有可检测到的分解。
