Akl Hossam N, Salah Dina, Abdel-Samad Hesham S, Abdel Aziz Ayman A, Abdel-Shafi Ayman A
Department of Chemistry, Faculty of Science, Ain Shams University 11566 Abbassia Cairo Egypt
Department of Physics, Faculty of Science, Ain Shams University 11566 Abbassia Cairo Egypt.
RSC Adv. 2023 May 2;13(19):13314-13323. doi: 10.1039/d3ra01280h. eCollection 2023 Apr 24.
The photophysical characteristics of some homoleptic ruthenium(ii) phenanthroline derivatives are investigated in aqueous medium. The lifetimes of the excited MLCT state of the studied complexes were found to be very sensitive to the type of the substituents on the phenanthroline ligand and were found to increase from about 0.96 μs in case of the parent [Ru(Phen)] complex to 2.97 μs in case of [Ru(DPPhen)]. The transient absorption spectra of the current set of complexes were studied also in aqueous medium. Quenching of the excited MLCT states of the studied complexes by molecular oxygen were studied and quenching rate constants were found to be in the range 1.02-4.83 × 10 M s. Values of singlet oxygen quantum yields were found to be in the range 0.01 to 0.25, and the corresponding efficiencies of singlet oxygen thereby produced, , were in the range 0.03-0.52. The mechanism by which the excited MLCT state is quenched by oxygen is discussed in light of the spin statistical factor rate constants and the competition between charge transfer and non-charge transfer quenching pathways. The partial charge transfer parameters, , were obtained and found to be about 0.88 for all complexes except for complexes with values lower than 0.25. The correlation of the activation free energies Δ of the exciplexes formation with the driving force for charge transfer, Δ , gives a charge transfer character of the exciplexes of about 35.0%.
在水介质中研究了一些同配型钌（II）菲咯啉衍生物的光物理特性。研究发现，所研究配合物的激发态金属-配体电荷转移（MLCT）态的寿命对菲咯啉配体上取代基的类型非常敏感，并且发现其寿命从母体[Ru（Phen）]配合物的约0.96 μs增加到[Ru（DPPhen）]配合物的2.97 μs。还在水介质中研究了当前这组配合物的瞬态吸收光谱。研究了分子氧对所研究配合物激发态MLCT态的猝灭作用，发现猝灭速率常数在1.02 - 4.83×10 M s范围内。单线态氧量子产率的值在0.01至0.25范围内，由此产生的单线态氧的相应效率在0.03 - 0.52范围内。根据自旋统计因子速率常数以及电荷转移和非电荷转移猝灭途径之间的竞争，讨论了激发态MLCT态被氧猝灭的机制。获得了部分电荷转移参数，发现除了 值低于0.25的配合物外，所有配合物的该参数约为0.88。激基复合物形成的活化自由能Δ 与电荷转移驱动力Δ 的相关性表明激基复合物的电荷转移特征约为35.0%。
