Stable open- and closed-shell Pd(II) and Cu(II) complexes of hexaethyl tripyrrin-1,14-dione (TD1) produce triplet, doublet or singlet states depending on the metal center and the redox state of the ligand. Pd(II) and Cu(II) form neutral TD1 complexes featuring ligand-based radicals, thus resulting in doublet and triplet states, respectively. The reversible one-electron oxidation of the complexes removes an unpaired electron from the ligand, generating singlet and doublet states. The optical properties and time-resolved dynamics of these systems are studied here using steady-state and ultrafast transient absorption (pump-probe) measurements. Fast relaxation with recovery of the ground state in tens of picoseconds is observed for the copper neutral radical and oxidized complexes as well as for the palladium neutral radical complex. Significantly longer timescales are observed for the oxidized palladium complex. The ability to tune the overall spin state of the complexes through their stable open-shell configurations as well as the reversible redox activity of the tripyrrolic systems makes them particularly interesting for catalytic applications as well as exploring magnetism and conductivity properties.

中文翻译：

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稳定的开壳和闭壳中性自由基和氧化三吡啶二酮配合物的时间分辨动力学

hexaethyl tripyrrin-1,14-dione (TD1)的稳定开壳和闭壳 Pd( II ) 和 Cu( II ) 配合物根据金属中心和配体的氧化还原状态产生三重态、双重态或单重态。Pd( II )和Cu( II) 形成具有基于配体的自由基的中性 TD1 配合物，从而分别产生双重态和三重态。配合物的可逆单电子氧化从配体中去除未配对电子，产生单重态和双重态。这些系统的光学特性和时间分辨动力学在这里使用稳态和超快瞬态吸收（泵探头）测量进行研究。对于铜中性自由基和氧化络合物以及钯中性自由基络合物，观察到在数十皮秒内恢复基态的快速弛豫。对于氧化的钯络合物，观察到明显更长的时间尺度。