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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >A solvent- and temperature-dependent intramolecular equilibrium of diamagnetic and paramagnetic states in Co complexes bearing triaryl amines
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A solvent- and temperature-dependent intramolecular equilibrium of diamagnetic and paramagnetic states in Co complexes bearing triaryl amines

机译：CO复合物中含有三芳基胺的CO复合物中的抗磁性和顺磁态的溶剂和温度依赖性分子内平衡

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摘要

Complexes [Co(L)(2)](ClO4)(2) (L = o-substituted 2-(pyridine-2-yl)-1,10-phenanthrolines 1a-c) containing three redox active centres (a Co2+ ion and two triaryl amine (Tara) units) have been synthesised. The order of oxidation steps in [Co(L)(2)](ClO4)(2) (L = 1a-c) was determined using cyclic voltammetry and EPR/UV-vis-NIR spectroelectrochemistry. In acetonitrile solutions, at room temperature, the first oxidation is Co-centred followed by the Tara oxidation at more anodic potentials. The order of oxidation is inverted in solutions of the less polar solvent dichloromethane. The Co3+/2+-centred redox event leads to a spin transition between the paramagnetic high-spin (HS) Co2+ and the diamagnetic low-spin (LS) Co3+ state, which was proven using H-1 NMR and EPR spectroscopy. After one-electron oxidation of [Co(L)(2)](ClO4)(2), an equilibrium between the diamagnetic [Co3+(L)](3+) and paramagnetic [Co2+(L)(L+)](3+) state in [Co(L)(2)](3+) (L = 1a-c) was found. Cyclic voltammetry showed enhanced intermolecular electron transfer between the [Co2+(L)(2)](2+) and [Co3+(L)(2)](3+) redox states mediated by [Co2+(L)(L+)](3+). Variable temperature vis-NIR spectroscopy of in situ generated [Co(L)(2)](3+) revealed a temperature-dependent redox equilibrium between the [Co3+(L)(2)](3+) and the [Co2+(L+)(L)](3+) states (L = 1a-c). Magnetic coupling between the HS-Co2+ ion and the Tara(+) radical in [HS-Co2+(L+)(L)](3+) (L = 1a,c) was deduced from broad and undetectable lines observed in the corresponding EPR spectra. Complete oxidation to [LS-Co3+(L+)(2)](5+) (L = 1a,c) leads to characteristic EPR spectra of Tara biradicals with non-interacting spins.
机译：复合物[Co（1）（2）]（CLO 4）（2）（L = O-取代的2-（吡啶-2-基）-1,10-菲咯啶1A-C），其含有三种氧化还原活性中心（CO 2 +离子和两个三芳基胺（塔拉）单位已经合成。使用循环伏安法和EPR / UV-Vis-Nir光谱电化学测定[CO（1）（2）]（CLO 4）（CLO 4）（2）（2）（2）（L = 1A-C）中的氧化步骤。在乙腈溶液中，在室温下，第一氧化在更多的阳极电位下是静脉氧化。氧化顺序在较低极性溶剂二氯甲烷的溶液中倒置。 CO3 + / 2 + - 姓氏氧化还原事件导致顺磁高旋转（HS）CO2 +和二磁性低旋转（LS）CO3 +状态之间的旋转转变，其使用H-1 NMR和EPR光谱证实。 [CO（1）（2）]（CLO4）（2）的单电子氧化后，二磁磁[CO 3 +（L）]（3+）和顺磁[CO 2 +（L）（L +）]（3）之间的平衡+）在[CO（1）（2）]（3+）（3 +）（L = 1A-C）中的状态。循环伏安法显示通过[CO 2 +（L）（L）（L +）]介导的[CO 2 +（2）（2）（2）（2）（2）]（2 +）和[CO 3 +（2）（2））和[CO 3 +（2）（2））（3 +）氧化还原状态之间增强的分子间电子传递）（ 3+）。可变温度Vis-nir光谱法产生的[CO（1）（2）]（3+）显示[CO 3 +（2）（2）]（3+）和[CO2 +]之间的温度依赖性氧化还原平衡。 L +）（L）]（3+）状态（L = 1A-C）。从相应的EPR中观察到的宽和未检测的线，推导出HS-CO2 +离子和塔拉（+）基团之间的磁偶联在[HS-CO2 +（L）]（3 +）（L = 1A，C）中光谱。完全氧化对[LS-CO 3 +（L +）（2）]（5 +）（L = 1A，C）导致TARA Biradicals的特征EPR光谱，具有非相互作用的旋转。

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