Photocatalyst Assemblies with Two Halide Ions
Photocatalyst Assemblies with Two Halide Ions
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DOI：
10.1016/j.jpap.2021.100090
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发表时间：
2021-12
影响因子：
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通讯作者：
Michael D Turlington;Alexander M Deetz;Dylan Vitt;G. Meyer
中科院分区：
文献类型：
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作者：
Michael D Turlington;Alexander M Deetz;Dylan Vitt;G. Meyer
设计了一系列含酰胺官能团的Ru多吡啶基光催化剂，成功地促进了卤化物在CH2Cl2和CH3CN溶液中的组装。在CH2Cl2中，卤化物组装伴随着可见的颜色变化，光谱变化为两个卤化物结合事件提供了明确的证据，产生了1：2的Ru：Halide组装。在较极性的CH3CN溶剂中，与氯、溴和碘也观察到1：2的组装结构，测得第一和第二卤化物的缔合平衡常数较大(K11=0.04-2×106M−1，K12=0.010-3×105M−1)。改变辅助配体上的官能团可以调节激发态还原电位(Ru2+⁎/+)，从而得到能够进行碘化物氧化的光催化剂。光催化剂激发态的猝灭导致静态猝灭和动态猝灭，Stern-Volmer分析在低碘浓度和高碘浓度下产生两个线性区域。低碘和高碘浓度下的动态猝灭速率常数(Kq分别为66.8和4.00×1010M−1S−1)和静态猝灭常数(KS分别为22.4和0.13×104M−1)分别与Ru2+和[Ru2+，i−]+的动态猝灭和[Ru2+，i−]+和[Ru2+，2i−]+的静态猝灭相一致。瞬时吸收光谱表明，猝灭反应生成还原的Ru+作为初级光产物，二碘化合物(I2·−)作为次要光产物。测得I2·−生成的二级速率常数为2.5M×1010M−1S−1，与扩散限制反应一致。瞬时吸收数据表明，氧化卤化物光产物只是扩散猝灭反应的结果，而不是与伴生的碘离子静态猝灭的结果。在Ru：碘组件中，快速的背电子转移速率和低的笼逸出产率被用来解释为什么静态猝灭途径不会导致可测量的光产额。
A series of ruthenium polypyridyl photocatalysts bearing amide functional groups were designed that successfully promoted halide assembly in CH2Cl2and CH3CN solution. In CH2Cl2, halide assembly was accompanied by a visible color change, and the spectral changes presented clear evidence for two halide binding events, yielding a 1:2 ruthenium:halide assembly. In the more polar solvent CH3CN, 1:2 assembly structures were also observed with chloride, bromide, and iodide, and large equilibrium constants were measured for association of the first and second halide (K11= 0.04 – 2 × 106M−1, K12= 0.01 – 3 × 105M−1). Varying the functional groups on the ancillary ligands tuned the excited-state reduction potentials (Ru2+⁎/+), resulting in a photocatalyst capable of performing iodide oxidation. Quenching of the photocatalyst excited state resulted in static and dynamic quenching, and a Stern-Volmer analysis yielded two linear regions at low and high iodide concentrations. The dynamic quenching rate constants (kq= 6.8 and 4.0 × 1010M−1s−1) and static quenching constants (KS= 2.4 and 0.13 × 104M−1) at low and high iodide concentrations, respectively, were consistent with dynamic quenching of Ru2+and [Ru2+,I−]+, and static quenching of [Ru2+,I−]+and [Ru2+,2I−]. Transient absorption spectroscopy revealed that the quenching reaction yielded a reduced ruthenium (Ru+) as the primary photoproduct and diiodide (I2•−) as a secondary photoproduct. The second-order rate constant for I2•−formation was measured to be 2.5 × 1010M−1s−1, a value consistent with the diffusion limited reaction. The transient absorption data indicates that oxidized halide photoproducts only result from the diffusional quenching reactions, and not from static quenching with an associated iodide ion. Fast back-electron transfer rates and low cage-escape yields in the ruthenium:iodide assemblies are invoked to explain why the static quenching pathway does not lead to measurable photoproduct yields.