Towards a better understanding of magnetic interactions within m-phenylene alpha-nitronyl nitroxide and imino nitroxide based radicals, part III: Magnetic exchange in a series of triradicals and tetraradicals based on the phenyl acetylene and biphenyl coupling units.
Towards a better understanding of magnetic interactions within m-phenylene alpha-nitronyl nitroxide and imino nitroxide based radicals, part III: Magnetic exchange in a series of triradicals and tetraradicals based on the phenyl acetylene and biphenyl coupling units.
复制标题
为了更好地理解间亚苯基 α-硝酰基氮氧自由基和亚氨基氮氧自由基内的磁相互作用，第三部分：基于苯乙炔和联苯偶联单元的一系列三自由基和四自由基中的磁交换。
作者：
L. Catala;J. Le Moigne;N. Gruber;J. Novoa;P. Rabu;E. Belorizky;P. Turek
本工作完成并扩展了我们之前关于磁性基态的测定和双基系列中通过键交换耦合强度的报告。这一知识随后被用于分析它们晶体中的磁相互作用。我们在这里报道了一系列以α -硝基氮氧化物（NN）或α -亚硝基氮氧化物（IN）为末端自由基片段的三自由基的研究，一种情况下通过间苯偶联单元连接，另一种情况下通过苯乙炔单元连接。对四自由基衍生物也进行了研究。孤立分子的研究（溶液中的EPR和DFT计算）允许通过磁耦合单元评估磁相互作用。发现所有的三基衍生物都表现出四重奏基态，而四基衍生物则确定为单线态基态。最后的结果强化了先前的发现，即单线态基态在涉及类似间苯偶联剂的相关双基中更有利。此外，通过键磁交换耦合的正交元连接可以证明是铁磁性的，从而确定了我们之前的假设。通过使用先前提出的方法，可以确定最相关的磁性途径，使固态三自由基和四自由基的磁性特性合理化。
The present work completes and extends our previous reports on the determination of the magnetic ground state and on the strength of the through bond exchange coupling within series of biradicals. This knowledge was subsequently exploited for the analysis of the magnetic interactions in their crystals. We report here the studies of series of triradicals incorporating alpha-nitronyl nitroxides (NN) or alpha-imino nitroxides (IN) as terminal radical fragments connected through a m-phenylene coupling unit in one case and a phenyl acetylene unit in other case. Tetraradical derivatives have also been studied. The studies of isolated molecules (EPR in solution and DFT calculations) allow the assessment of the magnetic interactions through the magnetic coupling unit. All triradical derivatives are found to exhibit a quartet ground state, whereas a singlet ground state is determined for the tetraradical. This last result reinforces previous findings that the singlet ground state is favoured in related biradicals involving similar m-phenylene couplers. Moreover, the through bond magnetic exchange coupling for the ortho-meta connectivity could be demonstrated as being ferromagnetic, thus ascertaining our previous hypotheses. The magnetic properties of the triradicals and tetraradicals in their solid state have been rationalized by using a previously proposed methodology, allowing to identify the most relevant magnetic pathways.