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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Topology, Distance, and Orbital Symmetry Effects on Electronic Spin-Spin Couplings in Rigid Molecular Systems: Implications for Long-Distance Spin-Spin Interactions
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Topology, Distance, and Orbital Symmetry Effects on Electronic Spin-Spin Couplings in Rigid Molecular Systems: Implications for Long-Distance Spin-Spin Interactions

机译：对刚性分子系统中电子自旋旋转耦合的拓扑，距离和轨道对称影响：对长距离旋转旋转相互作用的影响

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Understanding factors that underpin the signs and magnitudes of electron spin-spin couplings in biradicaloids, especially those that are integrated into highly delocalized electronic structures, promises to inform the design of molecular spintronic systems. Using steady-state and variable temperature electron paramagnetic resonance (EPR) spectroscopy, we examine spin dynamics in symmetric, strongly pi-conjugated bis [(porphinato)copper] (bis[PCu]) systems and probe the roles played by atom-specific macrocycle spin density, porphyrin-to-porphyrin linkage topology, and orbital symmetry on the magnitudes of electronic spin-spin couplings over substantial Cu-Cu distances. These studies examine the following: (i) meso-to-meso-linked bis[PCu] systems having oligoyne spacers, (ii) meso-to-meso-bridged bis[PCu] arrays in which the PCu centers are separated by a single ethynyl unit or multiple 5,15-diethynyl(porphinato)zinc(II) units, and (iii) the corresponding beta-to-beta-bridged bis[PCu] structures. EPR data show that, for beta-to-beta-bridged systems and meso-to-meso-linked bis[PCu] structures having oligoyne spacers, a through sigma-bond coupling average exchange interaction (j(avg)) In contrast, PCu centers separated by a single ethynyl or multiple 5,15-diethynyl(porphinato)-zinc(II) units display a phenomenological decay of ln[J(avg)] versus Cu-Cu sigma-bond separation number of similar to 0.115 per bond, half as large as for these other compositions, congruent with the importance of pi-mediated spin-spin coupling. These disparities derive from effects that trace their origin to the nature of the macrocycle-macrocycle linkage topology and the relative energy of the Cu d(x2-y2) singly occupied molecular orbital within the frontier orbital manifold of these electronically delocalized structures. This work provides insight into approaches to tune the extent of spin exchange interactions and distance-dependent electronic spin-spin coupling magnitudes in rigid, highly conjugated biradicaloids.
机译：理解施足于桦地面型中电子旋转旋转偶联的迹象和大小的因素，尤其是集成在高度划分的电子结构中的那些，有望通知分子旋转系统的设计。使用稳态和可变温度电子顺磁共振（EPR）光谱学，我们检查对称，强PI缀合的双[（卟啉）铜]（BIS [PCU]）系统中的旋转动力学，并探测由原子特异性宏观造成的角色旋转密度，卟啉至卟啉连杆拓扑，以及在基本上的Cu-Cu距离上的电子自旋旋转耦合幅度上的轨道对称性。这些研究审查以下内容：（i）具有寡磁羊座的Meso-to-Meso-Linked BIS [PCU]系统，（ii）中间桥接的BIS [PCU]阵列，其中PCU中心被单一分离乙炔基单元或多种5,15-二乙炔基（卟啉）锌（II）单位，和（iii）相应的β-β-桥接BIS [PCU]结构。 EPR数据表明，对于具有寡磁羊座的Beta-to-Beta-Bridged系统和具有寡氧织机间隔物的Meso-to-Meso-Latched BIS [PCU]结构，该结构与Σ-键耦合平均交换相互作用（J（AVG））相反，PCU由单个乙炔基或多个5,15-15-二乙炔基（卟啉）叠（卟啉）单位分离的中心显示LN的现象学衰减[J（AVG）]与Cu-Cu Sigma-Cold分离的数量相似至0.115，一半与这些其他组合物一样大，与PI介导的旋转旋转耦合的重要性一致。这些差异导出了将它们的来源追踪其宏细胞 - 宏细胞连杆性质的效果以及Cu D（X2-Y2）在这些电子移锁结构的前轨道歧管内单独占用的分子轨道的Cu D（X2-Y2）的相对能量。这项工作提供了深入了解旋转交换相互作用和距离依赖性电子旋转旋转型在刚性，高度共轭的Biradicaloids中的距离依赖性电子旋转偏振幅度的方法。

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