Energy and Environment Directorate, Pacific Northwest National Laboratory , Richland, Washington 99352, United States.
J Phys Chem A. 2013 Dec 5;117(48):12749-58. doi: 10.1021/jp406365c. Epub 2013 Nov 20.
The ligand-to-metal charge transfer (LMCT) excited state luminescence of Tc(dmpe)3 (dmpe is 1,2-bis-(dimethylphosphino)ethane) has been measured in solution at room temperature and is compared to its Re analogue. Surprisingly, both M(dmpe)3* (M = Re, Tc) species have extremely large excited-state potentials (ESPs) as oxidants, the highest for any simple coordination complex of a transition metal. Furthermore, this potential is available using a photon of visible light (calculated for M = Tc; E°'* = +2.48 V versus SCE; λmax = 585 nm). Open shell time-dependent density functional theory (TDDFT) calculations support the assignment of the lowest energy transition in both the technetium and rhenium complexes to be a doublet-doublet process that involves predominantly LMCT (dmpe-to-metal) character and is in agreement with past assignments for the Re system. As expected for highly oxidizing excited state potentials, quenching is observed for the excited states of both the rhenium and technetium complexes. Stern-Volmer analysis resulted in quenching parameters for both the rhenium and technetium complexes under identical conditions and are compared using Rehm-Weller analysis. Of particular interest is the fact that both benzene and toluene are oxidized by both the Re and Tc systems.
Tc(dmpe)3（dmpe 是 1,2-双（二甲基膦基）乙烷）的配体到金属电荷转移（LMCT）激发态发光在室温下的溶液中进行了测量，并与 Re 类似物进行了比较。令人惊讶的是，M(dmpe)3 （M = Re，Tc）两种物质都具有极高的激发态电势（ESP）作为氧化剂，这是任何过渡金属简单配合物中最高的。此外，使用可见光光子（对于 M = Tc 计算；E°' = +2.48 V 相对于 SCE；λmax = 585 nm）可以获得此电势。开壳层时间相关密度泛函理论（TDDFT）计算支持在锝和铼配合物中，最低能量跃迁都被分配为涉及主要 LMCT（dmpe 到金属）特征的双重过程，这与过去对 Re 系统的分配一致。如预期的那样，对于高氧化激发态电势，观察到铼和锝配合物的激发态的猝灭。在相同条件下对铼和锝配合物进行了 Stern-Volmer 分析，并使用 Rehm-Weller 分析进行了比较。特别有趣的是，事实证明，苯和甲苯都被 Re 和 Tc 系统氧化。
