Two bis-nitronyl-nitroxides linked by unsaturated non-aromatic spacers have been synthesized and investigated: 3D-NIT2 and DTD-NIT2. The magnetic properties of these diradicals have been investigated in the crystalline state by SQUID magnetometry and in dilute solution by EPR spectroscopy. According to magnetic measurements in the crystalline state both compounds experience strong antiferromagnetic exchange interactions. The singlet–triplet splitting has been estimated as ΔEST
= 95 K for 3D-NIT2, and ΔEST
= 75 K for DTD-NIT2. Solid-state MAS NMR spectroscopy has been used to determine the spin densities at the 1H and 13C nuclei of DTD-NIT2, thereby establishing spin polarization as the origin of the magnetic properties. The synthesis of an analogous mono-nitronyl-nitroxide has been undertaken in order to investigate the large intermolecular magnetic interactions observed in the crystalline state for 3D-NIT2.
已合成并研究了两个通过不饱和非芳香性间隔物连接的双硝基氮氧化物:3D-NIT2 和 DTD-NIT2。这些双自由基的磁性质在晶态中通过SQUID磁测量和在稀溶液中通过EPR光谱进行了研究。根据晶态的磁测量,两个化合物均经历了强反
铁磁交换相互作用。对于3D-NIT2,单态-三态的能量间隔估计为ΔEST = 95 K,而DTD-NIT2为ΔEST = 75 K。采用固态MAS NMR光谱法确定了DTD-NIT2中1H和13C核的自旋密度,从而确认自旋极化是其磁性质的来源。为研究在晶态中观察到的3D-NIT2的大型分子间磁相互作用,还进行了类似的单硝基氮氧化物的合成。