Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University , Katsura, Nishikyo-ku, Kyoto 615-8510, Japan.
J Org Chem. 2013 Sep 20;78(18):9282-90. doi: 10.1021/jo4015062. Epub 2013 Sep 11.
A series of nitronyl nitroxide radicals having different lengths of phenylene ethynylene molecular wire were synthesized to investigate the decay constant of p-phenylene ethynylene. By the measurement and simulation of the ESR spectra of the biradicals, it was found that the exchange interaction decreased with a decay constant (β) of 0.39 Å(-1) as the length of the molecule increased. This result indicates that the spin-spin exchange interaction between neutral radicals has a decay constant similar to that of the molecular conductance. This value of the decay constant indicates that a hopping mechanism does not take place in the measurement of the exchange interaction between neutral radicals even when the molecular wire has enough length to show hopping conduction of electrons.
合成了一系列具有不同苯乙炔分子链长度的硝酰氮氧自由基，以研究对苯撑的衰减常数。通过对双自由基的 ESR 光谱的测量和模拟，发现随着分子链长度的增加，交换相互作用以 0.39Å^(-1) 的衰减常数（β）降低。这一结果表明，中性自由基之间的自旋-自旋交换相互作用具有类似于分子电导率的衰减常数。该衰减常数的值表明，即使分子链足够长以显示电子的跳跃传导，在测量中性自由基之间的交换相互作用时也不会发生跳跃机制。
