作者:Carlos Bartual-Murgui、Cristian Pérez-Padilla、Simon J. Teat、Olivier Roubeau、Guillem Aromí
DOI:10.1021/acs.inorgchem.0c01061
日期:2020.9.8
The spin crossover (SCO) phenomenon represents a source of multistability at the molecular level, and dilution into a nonactive host was originally key to understand its cooperative nature and the parameters governing it in the solid state. Here, we devise a molecular alloying approach in which all components are SCO-active, but with significantly different characteristic temperatures. Thus, the molecular material [Fe(Mebpp)2](ClO4)2 (2) has been doped with increasing amounts of the ligand Me2bpp (Mebpp and Me2bpp = methyl- and bis-methyl-substituted bis-pyrazolylpyridine ligands), yielding molecular alloys with the formula [Fe(Mebpp)2–2x(Me2bpp)2x](ClO4)2 (4x; 0.05 < x < 0.5). The effect of the composition on the SCO process is studied through single-crystal X-ray diffraction (SCXRD), magnetometry, and differential scanning calorimetry (DSC). While the attenuation of intermolecular interactions is shown to have a strong effect on the SCO cooperativity, the spin conversion was found to occur at intermediate temperatures and in one sole step for all components of the alloys, thus unveiling an unprecedented allosteric SCO process. This effect provides in turn a means of tuning the SCO temperature within a range of 42 K.
自旋交叉(SCO)现象是分子水平多稳定性的一个来源,而稀释到非活性宿主中原本是理解其合作性质以及固态中控制其参数的关键。在这里,我们设计了一种分子合金化方法,其中所有成分都具有 SCO 活性,但特征温度却大不相同。因此,分子材料[Fe(Mebpp)2](ClO4)2 (2)中掺入了越来越多的配体 Me2bpp(Mebpp 和 Me2bpp = 甲基和双甲基取代的双吡唑吡啶配体),产生了分子合金,其化学式为[Fe(Mebpp)2-2x(Me2bpp)2x](ClO4)2 (4x;0.05 < x < 0.5)。通过单晶 X 射线衍射 (SCXRD)、磁力测定法和差示扫描量热法 (DSC) 研究了组成对 SCO 过程的影响。虽然分子间相互作用的衰减对 SCO 合作性有很大影响,但发现自旋转换发生在中间温度下,而且合金的所有成分都只需一步,从而揭示了一种前所未有的异构 SCO 过程。这种效应反过来又提供了一种在 42 K 范围内调节 SCO 温度的方法。