Conjugated Polymers Carrying Stable Radicals and Their Spin Control

研究了新型携带稳定自由基共轭聚合物的合成及其与电子结构的关系。采用Vilsmeier法和有机锂试剂分别合成了乙炔单体（3,5 -二叔丁基-4-羟基苯基）乙炔和对乙基苯基氢galvinoxyl。这些单体通过复分解或威尔金森催化剂聚合得到聚乙炔衍生物聚[（3,5 -二叔丁基-4-羟基苯基）乙炔](1)和聚（对乙基苯基氢galvinoxyl）(2)，分子量约为10^4。该聚合物可溶于普通有机溶剂，并通过PbO_2或碱性K_3Fe (CN)_6的非均相化学氧化转化为相应的共轭多自由基。通过调节氧化条件，得到了具有极高自旋浓度的多自由基2。由于取代基的共振稳定和/或空间效应，多自由基在溶液中甚至在固态中都相当稳定。利用紫外光电子能谱（UPS）和溶液ESR谱分析了这些多自由基的电子态。用UPS检测了这些多自由基沿主链存在明显的偶联现象。侧链取代基的空间效应可以解释电离阈值的减小和增大。氧化1的超精细结构ESR谱表明，苯氧自由基通过聚乙炔主链在约7个单体单元上以“中性孤子”形式共轭。在1和ESR信号强度的温度依赖性中观察到未配对电子之间的反铁磁相互作用。本研究揭示了聚乙炔主链多自由基的磁性不仅与主链上的共轭电子态有关，还与侧链取代基的特殊排列有关。

Synthesis and magnetic properties of new conjugated polymers carrying stable radicals were studied in connection with their electronic structure.Acetylene monomers, (3, 5-di-tert-butyl-4-hydroxyphenyl) acetylene and p-ethynylphenyl hydrogalvinoxyl, were synthesized using Vilsmeier method, and organolithium reagents, respectively. These monomers were polymerized with metathesis or Wilkinson catalyst to yield their polyacetylene derivatives, poly[(3, 5-di-tert-butyl-4-hydroxyphenyl)acetylene] (1) and poly (p-ethynylphenyl hydrogalvinoxyl) (2), with molecular weight of ca. 10^4. The polymers were soluble in common organic solvents and converted to the corresponding conjugated polyradicals via heterogeneous chemical oxidation using PbO_2 or alkaline K_3Fe (CN)_6. The polyradical 2 with extremely high spin concentration were obtained by regulating the oxidative conditions. The polyradicals were quite stable in solution and even in the solid state because of resonance stabilization and/or a steric effect of the substituens.Electronic state of these polyradicals were analyzed using ultraviolet photoelectron spectroscopy (UPS) and solution ESR spectra. The existence of significant pi-conjugation along the main chain in these polyradicals were examined by UPS. Decrease and increase in ionization threshold could be explained by the steric effect of sidechain substituent. ESR spectra with hyperfine structure for the oxidized 1 indicated that the phenoxy radical conjugates through the polyacetylene main chain over ca. 7 monomer units as a "neutral soliton". Antiferromagnetic interaction between the unpaired electrons was observed in 1 and from the temperature dependency of the ESR signal intensity.This research project revealed that magnetic properties of polyradical with polyacetylene backbone depend both on conjugated electronic state along main chain and on special arrangement of sidechain radical substituent.