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首页> 外文期刊>Polyhedron: The International Journal for Inorganic and Organometallic Chemistry >The competing roles of topology and spin density in the magnetic behavior of spin-delocalized radicals: Donor-acceptor annelated nitronyl nitroxides
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The competing roles of topology and spin density in the magnetic behavior of spin-delocalized radicals: Donor-acceptor annelated nitronyl nitroxides

机译：拓扑和自旋密度在自旋离域自由基的磁性行为中的竞争作用：供体-受体退火的亚硝酰基氮氧化物

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摘要

The effects of acceptor-donor interactions in thienyl substituted benzimidazole-nitronyl nitroxides (TBNN) on the absorption spectroscopy, spin density distribution, magnetic behavior, and crystallographic packing were explored through spectroscopy, computation. and characterization of structure and magnetic properties in the crystalline phase. The electronic spectra of the radicals exhibit a strong broad absorption in the NIR (lambda(max) similar to 1000 nm) that exhibits solvatochromism consistent with charge transfer between the thienyl (donor) and benzonitronyl nitroxide (acceptor) dyads. Computational analysis allowed assignment of the transition as a HOMO-SOMO transition (TD-DFT UB3LYP/6-31G**). The TBNN radicals form highly disordered slipped pi-stacks in the solid state that give rise to antiferromagnetic interactions consistent with 1D chain interactions. The magnetic behavior was well-fit to a Bonner-Fisher model to give exchange parameters of J = -2 to -10 cm(-1) depending on substitution. The weak exchange parameters are attributed to the degree of solid-state disorder, and the observed properties can be rationalized by the effects of substitution on the electronic structure and topology of the radicals.
机译：通过光谱学和计算，研究了噻吩基取代的苯并咪唑-亚硝基硝基氮氧化物（TBNN）中受体-供体的相互作用对吸收光谱，自旋密度分布，磁行为和晶体堆积的影响。结晶相的结构和磁性能的表征。自由基的电子光谱在NIR中表现出很强的宽吸收性（λ（最大值）类似于1000 nm），并表现出与噻吩基（供体）和苯并亚硝基硝基氮氧化物（受体）二元体之间的电荷转移一致的溶剂变色现象。计算分析允许将过渡指定为HOMO-SOMO过渡（TD-DFT UB3LYP / 6-31G **）。 TBNN自由基在固态下形成高度无序的滑动pi堆栈，从而引起与一维链相互作用一致的反铁磁相互作用。磁行为与Bonner-Fisher模型非常吻合，根据取代给出的交换参数为J = -2至-10 cm（-1）。弱交换参数归因于固态无序度，并且可以通过取代对自由基的电子结构和拓扑的影响来使观察到的性质合理化。

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