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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Very Strongly Ferromagnetically Coupled Diradicals from Mixed Radical Centers: Nitronyl Nitroxide Coupled to Oxoverdazyl via Polyene Spacers
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Very Strongly Ferromagnetically Coupled Diradicals from Mixed Radical Centers: Nitronyl Nitroxide Coupled to Oxoverdazyl via Polyene Spacers

机译：来自混合自由基中心的非常强的铁磁耦合双自由基：硝基氧化亚硝基通过多烯间隔基耦合至过氧叠氮基

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摘要

We predict extremely large and positive intramolecular magnetic exchange coupling constants (J) for coupled diradicals constructed from nitronyl nitroxide (NN) and oxoverdazyl (o-VER). These radicals have the general formula o-VER(N)-nC-NN where nC represents an olefinic spacer with n = 0, 2, 4, 6, and 8. Species like o-VER(C)-nC-NN have negative coupling constants. The atoms in the parentheses show the point of attachment of the coupler to the verdazyl moiety. Both the N-linked series and C-linked series have comparable stability. The triplet molecular geometries were optimized by the density functional (UB3LYP) method using the 6-311 g(d,p) basis set. This was followed by single-point UB3LYP calculations using 6-311++g(3df,3pd) basis. To calculate J, single-point broken-symmetry computations were performed on the optimized triplet geometries and using the same basis set. The N-linked diradicals coupled through conjugated polyenes are topologically different. These are found to have coupling constants of the order of 1000 cm(-1), whereas the C-linked diradicals show coupling constants of the order of -100 cm(-1). In general, for both cases, the absolute magnitude of the coupling constant decreases with the increase in the length of the spacer.
机译：我们预测由硝酰基硝基氧（NN）和氧杂二氮杂基（o-VER）构成的偶合双自由基的极大和正分子内磁交换耦合常数（J）。这些基团的通式为o-VER（N）-nC-NN，其中nC代表n = 0、2、4、6和8的烯烃间隔基。诸如o-VER（C）-nC-NN的物种具有负数。耦合常数。括号中的原子表示成色剂与Verdazyl部分的连接点。 N-连接系列和C-连接系列均具有相当的稳定性。通过使用6-311 g（d，p）基组的密度泛函（UB3LYP）方法优化了三重态分子的几何形状。随后是使用6-311 ++ g（3df，3pd）的单点UB3LYP计算。为了计算J，在优化的三重态几何体上使用相同的基集执行单点破碎对称计算。通过共轭多烯偶联的N-联双自由基在拓扑上是不同的。发现它们具有大约1000 cm（-1）的耦合常数，而C联双基表明耦合常数为-100 cm（-1）。通常，对于这两种情况，耦合常数的绝对大小都随着间隔物长度的增加而减小。

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