Synthesis and magnetic behaviour of poly(1,3-phenylene)-based polyradical carrying N-tert-butylaminoxyl radicals
作者:Hiroyuki Oka、Tomoki Tamura、Yozo Miura、Yoshio Teki
DOI:10.1039/a901944h
日期:——
The synthesis and magnetic behaviour of poly[6-(N-oxyl-N-tert-butylamino)biphenyl-3,3′-ylene] 2 are described. Polyradical 2 was prepared by the Pd-catalyzed polycondensation of N-tert-butyl-2,4-dibromoaniline and 1,3-phenylenebis(trimethylene boronate), followed by oxidation with 3-chloroperoxybenzoic acid. The degree of polymerisation determined by SEC (size exclusion chromatography) was ∼18. Polyradical 2 was stable in both solution and the solid state. The spin concentrations of 2 determined by EPR and SQUID were 0.75 and 0.82 spin per repeating unit, respectively. Magnetic susceptibility (χ) measurements on 2 were carried out on a SQUID magnetometer and these showed that the magnetic interaction between the unpaired electron spins was antiferromagnetic (θ=–0.98 K). The fact that no ferromagnetic interaction was observed was ascribed to a twisting of the nitroxide moieties from the π-conjugated main chain, and this was confirmed by X-ray crystallographic analysis of the corresponding model monoradical, N-tert-butyl-N-(2,4-diphenylphenyl)aminoxyl.
描述了聚[6-(N-氧基-N-叔丁基氨基)联苯-3,3'-亚基] 2 的合成和磁性行为。多自由基2是通过N-叔丁基-2,4-二溴苯胺和1,3-亚苯基双(三亚甲基硼酸酯)在Pd催化下缩聚,然后用3-氯过苯甲酸氧化制备的。通过 SEC(尺寸排阻色谱法)测定的聚合度为~18。多自由基2在溶液和固态下都是稳定的。由EPR和SQUID测定的2的自旋浓度分别为每个重复单元0.75和0.82个自旋。在 SQUID 磁力计上对 2 进行磁化率 (χ) 测量,结果表明不成对电子自旋之间的磁相互作用是反铁磁性的 (θ=–0.98 K)。没有观察到铁磁相互作用的事实归因于 π 共轭主链的硝基氧部分的扭曲,这一点通过相应模型单自由基 N-叔丁基-N-( 2,4-二苯基苯基)氨氧基。