Department of Chemistry and Biochemistry , Florida State University , Tallahassee , Florida 32306 , United States.
Department of Chemistry , University of Chicago , Chicago , Illinois 32306 , United States.
J Am Chem Soc. 2019 Nov 13;141(45):17989-17994. doi: 10.1021/jacs.9b09533. Epub 2019 Nov 4.
The nitroxyl radical 1-methyl-2-azaadamantane -oxyl (Me-AZADO) exhibits magnetic bistability arising from a radical/dimer interconversion. The transition from the rotationally disordered paramagnetic plastic crystal, Me-AZADO, to the ordered diamagnetic crystalline phase, (Me-AZADO), has been conclusively demonstrated by crystal structure determination from high-resolution powder diffraction data and by solid-state NMR spectroscopy. The phase change is characterized by a wide thermal hysteresis with high sensitivity to even small applied pressures. The molecular dynamics of the phase transition from the plastic crystal to the conventional crystalline phase has been tracked by solid-state (H and C) NMR and EPR spectroscopies.
氮氧自由基 1-甲基-2-氮杂金刚烷 -氧自由基（Me-AZADO）表现出磁双稳性，这是由自由基/二聚体的相互转化引起的。通过高分辨率粉末衍射数据的晶体结构测定和固态 NMR 光谱学，已经明确证明了从旋转无序的顺磁塑性晶体 Me-AZADO 到有序的反磁结晶相(Me-AZADO)的转变。相变的特点是宽的热滞后，对即使很小的外加压力也非常敏感。通过固态（H 和 C）NMR 和 EPR 光谱学跟踪了从塑性晶体到常规结晶相的相变的分子动力学。
