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Organic spin ladders from tetrathiafulvalene (TTF) derivatives

机译：四硫富瓦烯（TTF）衍生物的有机自旋梯

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摘要

Starting from the first organic spin ladder reported, a dithiophene-tetrathiafulvalene salt ((DT-TTF)(2)[Au(mnt)(2)]) (mnt = maleonitriledithiolate), two different approaches to enlarge the family of organic spin-ladder systems are described. The first approach consists of a molecular variation of the donor; to that purpose, the new TTF derivative ethylenethiothiophene-tetrathiafulvalene (ETT-TTF, 3), is synthesized and structurally characterized. From this donor a new ladder-like structure compound, (ETT-TTF)(2)[Au(mnt)(2)] (4), isostructural with (DT-TTF)(2)[Au(mnt)(2)], is obtained. However, the magnetic properties of 4 do not follow the known spin-ladder behavior owing to orientational disorder exhibited by the ETT-TTF molecules in the crystal structure. In the second approach, the acceptor complex is changed, either in the nature of the ligand or in the metal. With the [Au(i-mnt)(2)](-) salt (i-mnt=iso-maleonitriledithiolate), the new ladder-like compound (DT-TTF)(2)[Au(i-mnt)(2)] (5), isostructural with 4, is obtained, but only as a minority product. Two other compounds with a different anion generated in situ bearing a Au(I) dimeric core, were also isolated; (DT-TTF)(9)[Au-2(i-mnt)(2)](2) (6) as the most abundant phase and (DT- TTF)(2)[Au-2(i-mnt)(2)] (7) as another minority phase. Salt 7 is characterized by X-ray crystallography as a chiral compound, due to the torsion of the ligands around the central Au-Au bond. The magnetic properties of (DT-TTF)(2)[Au(i-mnt)(2)] (5) indicate that it follows a spin-ladder behavior and the electron paramagnetic resonance (EPR) data is fitted to the Troyer and Barnes and Riera equations with the parameters Delta/k(B) = 71 K, J(parallel to)/k(B) = 86 K, and J(perpendicular to)/k(B) = 142 K, indicating a J(perpendicular to)/J(parallel to) ratio of 1.65. The change of the gold complex [Au(mnt)(2)] for its copper analogue, [Cu(mnt)(2)] also leads to a ladder-like structure, (DT-T'FF)(2)[Cu(mnt)(2)] (8), which is isostructural with the gold analogue and with salts 4 and 5. The fully ionic salt (DT-TTF)[Cu(mnt)(2)] (9) is also obtained. The magnetic properties demonstrated that compound 8 is the third organic spin-ladder system of this family, and the values found by a fitting to the ladder equations were Delta/k(B) = 123 K, J(parallel to)/k(B) = 121 K, and J(perpendicular to)/k(B) = 218 K, corresponding to a J(perpendicular to)/J(parallel to) ratio of 1.75, similar to that of 5 and close to that of an ideal spin ladder.
机译：从报道的第一个有机自旋梯开始，开始使用二噻吩-四硫富瓦烯盐（（DT-TTF）（2）[Au（mnt）（2）]）（mnt =马来三烯二硫代磺酸盐），两种扩大有机自旋家族的方法描述了梯子系统。第一种方法是供体的分子变异。为此，合成了新的TTF衍生物亚乙基噻吩-四硫富瓦烯（ETT-TTF，3）并对其结构进行了表征。从该供体得到的新梯形结构化合物（ETT-TTF）（2）[Au（mnt）（2）]（4）与（DT-TTF）（2）[Au（mnt）（2）等结构]。但是，由于晶体结构中的ETT-TTF分子表现出取向紊乱，因此4的磁性不遵循已知的自旋梯子行为。在第二种方法中，无论是配体的性质还是金属中的受体络合物都发生了变化。使用[Au（i-mnt）（2）]（-）盐（i-mnt =异马来酸三硫代磺酸盐），新的梯状化合物（DT-TTF）（2）[Au（i-mnt）（2 ）]（5），得到具有4的同构结构，但仅作为少数产物。还分离了另外两种带有原位生成的带有Au（I）二聚核的阴离子的化合物。 （DT-TTF）（9）[Au-2（i-mnt）（2）]（2）（6）作为最丰富的相，以及（DT-TTF）（2）[Au-2（i-mnt） （2）]（7）作为另一个少数派阶段。由于配体围绕中心Au-Au键的扭转，盐7通过X射线晶体学表征为手性化合物。 （DT-TTF）（2）[Au（i-mnt）（2）]（5）的磁性能表明，它遵循自旋梯子行为，并且电子顺磁共振（EPR）数据拟合到Troyer和参数Delta / k（B）= 71 K，J（平行于）/ k（B）= 86 K和J（垂直于）/ k（B）= 142 K的Barnes和Riera方程，表示J（垂直）/ J（平行）比率为1.65。铜类似物[Cu（mnt）（2）]的金配合物[Au（mnt）（2）]的变化也会导致梯形结构，（DT-T'FF）（2）[Cu （mnt）（2）]（8），其与金类似物以及盐4和5同构。还获得了全离子盐（DT-TTF）[Cu（mnt）（2）]（9）。磁性表明化合物8是该族的第三个有机自旋梯体系，通过对梯形方程的拟合得到的值是Delta / k（B）= 123 K，J（平行）/ k（B） ）= 121 K，并且J（垂直于）/ k（B）= 218 K，对应于J（垂直于）/ J（平行于）的比率为1.75，类似于5的比率，并且接近理想值旋转梯子。

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