Cho Byungmoon, Swain Alicia, Gautam Ritika, Tomat Elisa, Huxter Vanessa M
Department of Chemistry and Biochemistry, The University of Arizona, Tucson, Arizona, 85721, USA.
Department of Physics, The University of Arizona, Tucson, Arizona, 85721, USA.
Phys Chem Chem Phys. 2022 Jul 6;24(26):15718-15725. doi: 10.1039/d2cp00632d.
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.
六乙基三吡咯-1,14-二酮（TD1）的稳定开壳和闭壳钯（II）和铜（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、二重态或单重态。钯（II）和铜（II）形成具有基于配体自由基的中性TD1配合物，因此分别产生二重态和三重态。配合物的可逆单电子氧化从配体中去除一个未配对电子，产生单重态和二重态。这里使用稳态和超快瞬态吸收（泵浦-探测）测量研究了这些体系的光学性质和时间分辨动力学。对于铜中性自由基和氧化配合物以及钯中性自由基配合物，观察到在几十皮秒内快速弛豫并恢复基态。对于氧化钯配合物，观察到显著更长的时间尺度。通过其稳定的开壳构型调节配合物的整体自旋态的能力以及三吡咯体系的可逆氧化还原活性，使得它们在催化应用以及探索磁性和导电性方面特别有趣。
