Roncero-Barrero C, Ribas-Ariño J, Moreira I de P R, Deumal M
Secció Química Física, Dept. Ciència de Materials i Química Física, and Institut de Química Teòrica i Computacional IQTCUB, Universitat de Barcelona, Martí i Franquès, 1, E08028 Barcelona, Spain.
Dalton Trans. 2022 Aug 30;51(34):13032-13045. doi: 10.1039/d2dt01340a.
The use of purely organic materials is a promising approach for the miniaturization of devices due to their interesting optical, electronic and magnetic properties. Bisdithiazolyl-based bisDTA compounds have emerged as promising candidates for radical-based single component conductors exhibiting simultaneously magnetic properties. Our computational work focuses on the intriguing magnetism of 4 isostructural pyridine-bridged bisDTA-multifunctional materials triggered by their magnetic and conducting properties being strongly dependent on the different S/Se ratios in the neutral radical skeleton: specifically, bisdithiazolyl (S,S) displays no magnetic order at low temperatures, thiaselenazolyl (Se,S) exhibits spin-canted antiferromagnetism (AFM), and both (S,Se) and bisdiselenazolyl (Se,Se) behave as bulk ferromagnets (FM). Our results reveal that (1) the magnetic response depends on the existence of an intricate network of both AFM and FM spin exchange couplings between neighbouring radicals; and (2) the structural arrangement of π-stacked pairs of radicals sits on a point in the configurational space that is very close to a crossover region where switches from AFM to FM. Indeed, for bulk FM, the experimental response is only accounted for when considering an optimised crystal structure able to portray adequately the electronic structure of bisDTAs in the region close to the temperature at which magnetic ordering emerges. Magneto-structural correlation maps show the large sensitivity of to very small structural changes with temperature along the π-stacks that lead to drastic changes in the magnetic properties. Clearly, the understanding of magnetism in the title bisDTA compounds is decisive to rationally tailor the properties of multifunctional materials by subtle structural modifications of their crystal packing.
由于其有趣的光学、电子和磁性特性，使用纯有机材料是实现器件小型化的一种有前景的方法。基于双二噻唑基的双DTA化合物已成为基于自由基的单组分导体的有前景的候选物，这些导体同时具有磁性。我们的计算工作聚焦于4种同构吡啶桥联双DTA多功能材料的有趣磁性，其磁性和导电性强烈依赖于中性自由基骨架中不同的S/Se比：具体而言，双二噻唑基（S,S）在低温下不显示磁有序，硫硒唑基（Se,S）表现出自旋倾斜反铁磁性（AFM），而（S,Se）和双二硒唑基（Se,Se）均表现为体铁磁性（FM）。我们的结果表明：（1）磁响应取决于相邻自由基之间复杂的AFM和FM自旋交换耦合网络的存在；（2）π堆叠自由基对的结构排列位于构型空间中非常接近从AFM转变为FM的交叉区域的一个点上。实际上，对于体FM，只有在考虑能够充分描绘双DTA在接近磁有序出现温度区域的电子结构的优化晶体结构时，才能解释实验响应。磁结构相关图显示，沿着π堆叠，随着温度的变化，磁对非常小的结构变化具有很大的敏感性，这会导致磁性性质的剧烈变化。显然，理解标题中双DTA化合物的磁性对于通过对其晶体堆积进行细微的结构修饰来合理调整多功能材料的性质起着决定性作用。
