Synthesis and magnetic behaviour of polyradical: poly(1,3-phenyleneethynylene) with π-toporegulated pendant stable aminoxyl and imine N-oxide–aminoxyl radicals
作者:Yozo Miura、Tsuneki Issiki、Yukio Ushitani、Yoshio Teki、Koichi Itoh
DOI:10.1039/jm9960601745
日期:——
The palladium-catalysed polycondensation of N-tert-butyl-N-(3,5-diethynylphenyl)aminoxyl with 2-(3,5-diiodophenyl)-4,4,5,5-tetramethyl-3-oxido-2-imidazolin-3-ium-1-yloxyl in pyridineâtriethylamine at room temperature afforded poly(1,3-phenyleneethynylene) with pendant aminoxyl and imine N-oxideâaminoxyl radicals as a light blue powder in 78â83% yields. The number-average molecular weights (n) of the polyradical determined by GPC were 2670â3030 and the spin concentrations determined by EPR were 1.91â2.02 à 1021 spins gâ1. Both solution (CH2Cl2) and powder EPR measurements of the polyradicals gave a hyperfine-smeared single line spectrum, suggesting that spin-exchange narrowing took place due to the high spin concentrations of the polyradicals. The magnetic susceptibility (Ï) measurements of the polyradicals were carried out on a superconducting quantum interference device (SQUID) magnetometer in the temperature range of 1.8â300 K. The Ï Tvs. T plots showed that the polyradicals were a paramegnetic species yielding a weak antiferromagnetic coupling (θ = â1.5 K) below 30 K. The absence of the through-bond ferromagnetic interaction is accounted for by masking of the interaction by the stronger through-space antiferromagnetic interactions.
钯催化的N-叔丁基-N-(3,5-二乙炔苯基)氨氧基与2-(3,5-二碘苯基)-4,4,5,5-四甲基-3-氧化-2-咪唑啉-3-铵-1-氧基的聚缩合反应在常温下于吡啶-三乙胺中进行,得到了一种带有氨氧基和亚胺N-氧基-氨氧基自由基的聚(1,3-苯乙炔基)的浅蓝色粉末,产率为78-83%。通过凝胶渗透色谱法(GPC)测定的聚自由基的数均分子量(n)为2670-3030,通过电子顺磁共振(EPR)测定的自旋浓度为1.91-2.02 × 10²¹ spins·g⁻¹。对聚自由基的溶液(CH₂Cl₂)和粉末的EPR测量均显示出高频细化的单线谱,表明由于聚自由基的高自旋浓度,发生了自旋交换收窄。聚自由基的磁导率(χ)测量是在1.8-300 K的温度范围内使用超导量子干涉装置(SQUID)磁强计进行的。χT对T的图谱显示聚自由基为一种顺磁性物质,在30 K以下呈现出微弱的反铁磁耦合(θ = -1.5 K)。通过由于较强的空间反铁磁相互作用掩盖了通过键的铁磁相互作用,来解释其缺失。