Kamebuchi Hajime, Tamaki Satoshi, Okazawa Atsushi, Kojima Norimichi
Department of Chemistry, College of Humanities and Sciences, Nihon University, Sakurajosui 3-25-40, Setagaya-ku, Tokyo 156-8550, Japan.
Graduate School of Arts and Sciences, The University of Tokyo, Komaba 3-8-1, Meguro-ku, Tokyo 153-8902, Japan.
Membranes (Basel). 2021 May 27;11(6):400. doi: 10.3390/membranes11060400.
The development and the photophysical behavior of a transparent ion-exchange membrane based on a pH-sensitive polypyridyl ruthenium(II) complex, (bpy)Ru(Hbpib)Ru(bpy) (bpy = 2,2'-bipyridine, Hbpib = 1,4-bis([1,10]phenanthroline[5,6-]-imidazol-2-yl)benzene), are experimentally and theoretically reported. The emission spectra of [(bpy)Ru(Hbpib)Ru(bpy)]@Nafion film were observed between pH 2 and pH 11 and showed the highest relative emission intensity at pH 5 ( = 594.4 nm). The relative emission intensity of the film significantly decreased down to 75% at pH 2 and 11 compared to that of pH 5. The quantum yields () and lifetimes () showed similar correlations with respect to pH, = 0.13 and = 1237 ns at pH 5, and = 0.087 and = 1014 ns and = 0.069 and = 954 ns at pH 2 and pH 11, respectively. These photophysical data are overall considerably superior to those of the solution, with the radiative- () and non-radiative rate constants () at pH 5 estimated to be = 1.06 × 10 s and = 7.03 × 10 s. Density functional theory calculations suggested the contribution of ligand-to-ligand- and intraligand charge transfer to the imidazolium moiety in Ru-Hbpib species, implying that the positive charge on the Hbpib ligand works as a quencher. The Ru-Hbpib species seems to enhance non-radiative deactivation by reducing the energy of the upper-lying metal-centered excited state. These would be responsible for the pH-dependent "" emission behavior.
实验和理论报道了一种基于pH敏感的聚吡啶钌（II）配合物（bpy）Ru（Hbpib）Ru（bpy）（bpy = 2,2'-联吡啶，Hbpib = 1,4-双（[1,10]菲咯啉[5,6-]咪唑-2-基）苯）的透明离子交换膜的发展及其光物理行为。观察了[(bpy)Ru(Hbpib)Ru(bpy)]@Nafion膜在pH 2至pH 11之间的发射光谱，在pH 5（λ = 594.4 nm）时显示出最高的相对发射强度。与pH 5相比，该膜在pH 2和pH 11时的相对发射强度显著降低至75%。量子产率（Φ）和寿命（τ）在pH方面表现出相似的相关性，在pH 5时，Φ = 0.13且τ = 1237 ns，在pH 2和pH 11时，分别为Φ = 0.087且τ = 1014 ns以及Φ = 0.069且τ = 954 ns。这些光物理数据总体上明显优于溶液中的数据，在pH 5时的辐射速率常数（kr）和非辐射速率常数（knr）估计分别为kr = 1.06×10⁻⁵ s⁻¹和knr = 7.03×10⁻⁵ s⁻¹。密度泛函理论计算表明配体间和配体内电荷转移对Ru - Hbpib物种中咪唑鎓部分有贡献，这意味着Hbpib配体上的正电荷起到淬灭剂的作用。Ru - Hbpib物种似乎通过降低较高的以金属为中心的激发态的能量来增强非辐射失活。这些因素将导致pH依赖的“λ”发射行为。
