Photoinduced One-Electron Chloride Oxidation in Water Using a Pentacationic Ir(III) Photosensitizer.

A novel iridium(III) photosensitizer containing pyridinium-decorated terpyridines has been used for the photo-oxidation of chloride in water. Despite its abundance, the very positive one-electron reduction potential (E° Cl•/- = 2.1-2.4 V vs NHE) restricted its use in energy conversion schemes and artificial photosynthesis. The kinetics of the photoinduced electron transfer process were investigated through Stern-Volmer quenching experiments and nanosecond transient absorption spectroscopy, which provided unambiguous evidence that photoinduced chloride oxidation occurred with a quenching rate constant kq = 5.0 × 1010 M-1 s-1. Complementary spectroelectrochemistry and photolysis experiments confirmed the formation of the reduced photosensitizer and showcased the redox and photostability of the Ir(III) photosensitizer that holds great promise for the HX splitting approach.

一种含有吡啶修饰的三联吡啶的新型铱（III）光敏剂已被用于水中氯离子的光氧化。尽管氯离子含量丰富，但其一电子还原电位非常正（相对于标准氢电极，$E^{\circ}_{Cl^{\bullet}/Cl^{-}} = 2.1 - 2.4\ V$），这限制了它在能量转换方案和人工光合作用中的应用。通过斯特恩 - 沃尔默猝灭实验和纳秒瞬态吸收光谱研究了光诱导电子转移过程的动力学，这提供了明确的证据，表明光诱导的氯离子氧化以猝灭速率常数$k_q = 5.0×10^{10}\ M^{-1}\ s^{-1}$发生。互补的光谱电化学和光解实验证实了还原态光敏剂的形成，并展示了铱（III）光敏剂的氧化还原和光稳定性，这对HX分解方法具有很大的应用前景。