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首页> 外文期刊>Chemistry: A European journal >Greatly enhanced intermolecular π-dimer formation of a porphyrin trimer radical trications through multiple πbonds
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Greatly enhanced intermolecular π-dimer formation of a porphyrin trimer radical trications through multiple πbonds

机译：通过多个π键极大地增强了卟啉三聚体自由基分子间的π-二聚体形成

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摘要

A trefoil-like porphyrin trimer linked by triphenylamine (TPA-TPZn _3) was synthesized. A three-electron oxidation of TPA-TPZn _3 forms a radical trication (TPA-TPZn_3~(3+)), in which each porphyrin ring undergoes a one-electron oxidation. The radical trication TPA-TPZn_3~(3+) spontaneously dimerizes to afford (TPA-TPZn_3)_2~(6+) in CH_2Cl_2. The characteristic charge-resonance band due to the charge delocalization over the πsystem of (TPA-TPZn_3)_2~(6+) was observed in the NIR region. The initial oxidation potential of TPA-TPZn_3 is negatively shifted relative to that of the corresponding monomer porphyrin, which results from the stabilization of the oxidized state of TPA-TPZn _3 associated with the dimerization. The thermodynamic parameters (i.e., ΔH, ΔS, and ΔG) for the formation of (TPA-TPZn _3)_2~(6+) were determined by measuring Vis/NIR spectra at various temperatures. The formation constant of (TPA-TPZn _3)_2~(6+) is significantly larger than that of the radical cation dimer of the corresponding monomer porphyrin (e.g., over 2000-fold at 233K). The electronic states were investigated using EPR spectroscopic analysis. The greatly enhanced dimerization of TPA-TPZn _3~(3+) results from multiple π-bond formation between the porphyrin radical cations. Multiple π bonds: A three-electron oxidation of a trefoil-like porphyrin trimer generates a radical trication, which spontaneously dimerizes. The dimerization of the trimer is much more favorable relative to the corresponding monomer, which results from the intermolecular multiple π-bond formation between porphyrin radical cations of the trimer (see picture).
机译：合成了由三苯胺（TPA-TPZn_3）连接的三叶状卟啉三聚体。 TPA-TPZn _3的三电子氧化形成自由基三阳离子（TPA-TPZn_3〜（3+）），其中每个卟啉环均经历单电子氧化。自由基三阳离子TPA-TPZn_3〜（3+）自发二聚，得到CH_2Cl_2中的（TPA-TPZn_3）_2〜（6+）。在NIR区域观察到由于（TPA-TPZn_3）_2〜（6+）的π系统上的电荷离域而引起的特征电荷共振带。 TPA-TPZn_3的初始氧化电位相对于相应的单体卟啉发生负移，这是由于与二聚化相关的TPA-TPZn_3氧化态的稳定所致。通过在各种温度下测量Vis / NIR光谱来确定用于形成（TPA-TPZn _3）_2〜（6+）的热力学参数（即，ΔH，ΔS和ΔG）。 （TPA-TPZn _3）_2〜（6+）的形成常数明显大于相应单体卟啉的自由基阳离子二聚体的形成常数（例如，在233K时超过2000倍）。使用EPR光谱分析研究了电子态。 TPA-TPZn _3〜（3+）的二聚化大大增强是由于卟啉自由基阳离子之间形成多个π键。多个π键：三叶状卟啉三聚体的三电子氧化产生自由基三阳离子，该自由基自发二聚。相对于相应的单体，三聚体的二聚化更为有利，这是由于三聚体的卟啉自由基阳离子之间形成了分子间多重π键（参见图片）。

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