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首页> 外文期刊>Polyhedron: The International Journal for Inorganic and Organometallic Chemistry >Beyond the active-electron approximation: Origin of ferromagnetic exchange in donor-acceptor heterospin biradicals
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Beyond the active-electron approximation: Origin of ferromagnetic exchange in donor-acceptor heterospin biradicals

机译：超越有源电子近似：供体-受体异旋双自由基中铁磁交换的起源

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The complex, (NNSQ)CuTp(Cum,Me), is comprised of three different spin carrying units. These three S = 1/2 sites are comprised of Cu(II), nitronyl nitroxide (NN), and 5-tert-butyl-semiquinone (SQ). Both the Cu(II)-SQ and SQ-NN pairwise interactions are strongly exchange coupled resulting an S-T = 3/2 ground state due to ferromagnetic interactions. Low-temperature EPR spectroscopy confirms the S-T = 3/2 ground state determined from magnetic susceptibility studies and indicates that the quartet is zero-field split by vertical bar D vertical bar similar to 0.5 cm(-1). We have probed the origin of the strong ferromagnetic exchange within the NNSQ heterospin biradical ligand by a combination of electronic absorption, and low-temperature magnetic circular dichroism spectroscopies. The origin of the strong intraligand NNSQ ferromagnetic exchange has been suggested to result from an intraligand charge transfer (ILCT) transition transition that possesses appreciable SQ pi -> NN pi* charge transfer character. The magnitude of the ferromagnetic exchange has been related to the energy of this ILCT transition, the magnitude of the NN single site exchange integral, and the magnitude of the electronic coupling matrix element that connects the SQ SOMO with the NN LUMO. (c) 2005 Elsevier Ltd. All rights reserved.
机译：络合物（NNSQ）CuTp（Cum，Me）由三个不同的自旋携带单元组成。这三个S = 1/2的位点由Cu（II），硝酰基硝基氧（NN）和5-叔丁基-半醌（SQ）组成。 Cu（II）-SQ和SQ-NN的成对相互作用都是强交换耦合的，由于铁磁相互作用，导致S-T = 3/2基态。低温EPR光谱证实了根据磁化率研究确定的S-T = 3/2基态，并表明四重奏是由垂直条D垂直条（类似于0.5 cm（-1））零场分裂的。我们已经通过电子吸收和低温磁性圆二色性光谱学的组合探索了NNSQ异旋双自由基配体内强铁磁交换的起源。有人提出强内配体NNSQ铁磁交换的起源是由具有明显SQ pi-> NN pi *电荷转移特性的配体内电荷转移（ILCT）跃迁转变引起的。铁磁交换的大小与该ILCT跃迁的能量，NN单点交换积分的大小以及将SQ SOMO与NN LUMO连接的电子耦合矩阵元素的大小有关。 （c）2005 Elsevier Ltd.保留所有权利。

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