Weakening of the p*-p* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl 2 C 6 H 3 CNSSN
Weakening of the p*-p* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl 2 C 6 H 3 CNSSN
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1,2,3,5-二噻二唑基自由基中 p*-p* 二聚作用的减弱：二氯苯基二噻二唑基 Cl 2 C 6 H 3 CNSSN 的结构、EPR、磁性和计算研究
DOI：
10.1039/c4ce00308j
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发表时间：
2014
期刊：
影响因子：
3.1
通讯作者：
Constantinides C
中科院分区：
文献类型：
--
作者：
Constantinides C
合成了一系列二氯苯基二噻二唑类化合物（DCP-DTDA），并通过X射线衍射对其结构进行了表征（1 = 2，3-DCP-DTDA; 2 = 2，4-DCP-DTDA; 3 = 2，5-DCP-DTDA; 4 = 3，4-DCP-DTDA; 5 = 3，5-DCP-DTDA）。所有自由基均采用顺式共面π*-π* 二聚体，二聚体内S → S接触范围为3.119（8）-3.300（5）π。氯代芳烃采用β-折叠结构的倾向有助于在1-5中形成层状结构，其中叠层内Cl-Cl接触在3.44（1）-3.82（1）Ω范围内。在堆积方向上，堆积主要是由分子间S Cl接触形成的。变温磁化率测量1-5在5-300 K的范围内揭示了顺磁性的开始约。二十万固体EPR研究表明，这种顺磁性与三重态激发态的热布居有关。与Bleaney-Bowers模型的良好拟合确定了二聚体中自由基之间的交换相互作用（2 J）在−904至−1529 cm−1的范围内。二聚化过程的计算研究表明，在内部二聚体S S距离超过3.2 μ m的封闭壳层单线态变得不稳定相对于两个开放壳层单线态和三重态配置。
A series of dichlorophenyl dithiadiazolyls (DCP-DTDA) have been prepared and structurally characterized by X-ray diffraction (1 = 2,3-DCP-DTDA; 2 = 2,4-DCP-DTDA; 3 = 2,5-DCP-DTDA, 4 = 3,4-DCP-DTDA and 5 = 3,5-DCP-DTDA). All the radicals adopt cis-cofacial π*–π* dimers with intra-dimer S⋯S contacts in the range 3.119(8)–3.300(5) Å. The propensity for chloro-aromatics to adopt a β-sheet structure assists formation of lamellar structures in 1–5 with intra-stack Cl⋯Cl contacts in the range 3.44(1)–3.82(1) Å. Perpendicular to the stacking direction, the packing is dominated by formation of intermolecular S⋯Cl contacts. Variable-temperature magnetic susceptibility measurements on 1–5 in the range 5–300 K reveal the onset of paramagnetism around ca. 200 K. Solid-state EPR studies reveal that this paramagnetism is associated with thermal population of a triplet excited state. A good fit to the Bleaney–Bowers model determined the exchange interactions (2J) between the radicals in the dimers to be in the range −904 to −1529 cm−1. Computational studies of the dimerisation process indicate that at intra-dimer S⋯S distances in excess of 3.2 Å the closed-shell singlet becomes destabilized with respect to both the open-shell singlet and triplet state configurations.