Impact of short and long-range effects on the magnetic interactions in neutral organic radical-based materials
Impact of short and long-range effects on the magnetic interactions in neutral organic radical-based materials
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DOI：
10.1039/c3cp44647f
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发表时间：
2013-01-01
影响因子：
3.3
通讯作者：
Robert, Vincent
中科院分区：
文献类型：
--
作者：
Domingo, Alex;Verot, Martin;Robert, Vincent
通过波函数计算（Difference Dedicated Configuration Interaction，DDCI）分析中性有机自由基基材料（自由基二聚体）的组成单元的电子结构和环境的相互影响。通过检查短程和长程效应，重点关注两类中性有机材料的磁性能调制。 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA)材料高温相的交换耦合常数J在DDCI水平下计算为J= -95 cm(-1)。使用晶格有限块（离散反应场，DRF）中原子的个体极化率自洽地考虑环境电子极化，并占 TTTA 中计算的 J 值的不到 5%。此外，利用四氮唑基自由基家族的化学灵活性，通过从取代的四氮唑基自由基对中提取J、U、t和K参数来分析强吸电子基团的贡献。我们对 verdazyl 自由基对的从头计算表明，NO2 基团的添加会导致 (i) 铁磁和反铁磁贡献的变化相互抵消，留下几乎恒定的交换耦合常数，约 100。 J接近20cm(-1)，并且(ii)可以预期增强的传导性能。与无机类似物相比，人们可以得出这样的结论：中性有机自由基基材料的磁性行为主要由超分子排列决定，而环境影响的影响较小。
The mutual influence of electronic structure and environment of the constituent units of neutral organic radical-based materials (radical dimers) is analysed by means of wave function calculations (Difference Dedicated Configuration Interaction, DDCI). Focus is put on the magnetic property modulations of two classes of neutral organic materials by inspecting both short- and long-range effects. The exchange coupling constant J for the high-temperature phase of the 1,3,5-trithia-2,4,6-triazapentalenyl (TTTA) material is calculated to be J= -95 cm(-1) at the DDCI level. The environmental electronic polarization is taken into account self-consistently using the individual polarizabilities of the atoms in a finite block of the crystal lattice (Discrete Reaction Field, DRF) and accounts for less than 5% of the calculated J value in TTTA. Furthermore, taking advantage of the chemical flexibility of the verdazyl radical family, the contribution of strong electron-withdrawing groups is analysed by extracting the J, U, t and K parameters from pairs of substituted verdazyl-based radicals. Our ab initio calculations of verdazyl radical pairs suggest that the addition of NO2 groups cause (i) the variations of the ferromagnetic and antiferromagnetic contributions to cancel out, leaving an almost constant exchange coupling constant, ca. J approximate to 20 cm(-1), and that (ii) enhanced conduction properties can be anticipated. In contrast to inorganic analogues, one may conclude that the magnetic behaviour of neutral organic radical-based materials is mostly governed by the supramolecular arrangement, whereas environmental effects have a lesser impact.