Univ Lyon, Université Claude Bernard Lyon 1, Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, F-69622, Villeurbanne, France.
Département de Chimie Physique, Université de Genève , 30 Quai Ernest-Ansermet, 1211 Genève 4, Switzerland.
J Am Chem Soc. 2016 Dec 21;138(50):16493-16501. doi: 10.1021/jacs.6b10544. Epub 2016 Dec 12.
The manganese-nitronyl-nitroxide two-dimensional coordination polymer {[Mn(NITIm)]ClO} (1) (NITImH = 2-(2-imidazolyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-3-oxide-1-oxyl) undergoes an unusual hysteretic thermo-induced valence tautomeric transition near room temperature, during which the manganese(II) ions are oxidized to manganese(III) and two of the three deprotonated radicals (NITIm) are reduced to their diamagnetic aminoxyl form (denoted NIT). Upon cooling, the high-temperature species {[Mn(NITIm)]ClO} (1) turns into the low-temperature species {[Mn(NIT)(NITIm)]ClO} (1) around 274 K, while on heating the process is reversed at about 287 K. This valence tautomeric phenomenon is supported by temperature-dependent magnetic susceptibility measurements, differential scanning calorimetry (DSC), crystal structure determination, UV-vis absorption, X-ray absorption (XAS), and emission (XES) and electron paramagnetic resonance (EPR) spectroscopies in the solid state.
锰-亚硝酰基-氮氧自由基二维配位聚合物{[Mn(NITIm)]ClO}（1）（NITImH=2-（2-咪唑基）-4,4,5,5-四甲基-4,5-二氢-1H-3-氧化物-1-氧自由基）在室温附近经历了一种不寻常的滞后热诱导价互变异构转变，在此过程中，锰（II）离子被氧化为锰（III），三个去质子自由基（NITIm）中的两个被还原为其顺磁的氨基氧自由基形式（表示为 NIT）。冷却时，高温物种{[Mn(NITIm)]ClO}（1）在 274 K 左右转变为低温物种{[Mn(NIT)(NITIm)]ClO}（1），而在加热时，该过程在约 287 K 时反转。这种价互变异构现象得到了温度依赖的磁化率测量、差示扫描量热法（DSC）、晶体结构测定、紫外可见吸收、X 射线吸收（XAS）和发射（XES）以及固态电子顺磁共振（EPR）光谱的支持。
