Goodwin Matthew J, Deetz Alexander M, Griffin Paul J, Meyer Gerald J
Department of Chemistry, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599, United States.
Inorg Chem. 2024 Aug 26;63(34):15772-15783. doi: 10.1021/acs.inorgchem.4c01726. Epub 2024 Aug 9.
The preassociation of reactants in a photoinitiated redox reaction through the use of noncovalent interactions can have a significant impact on excited state reactivity. As these noncovalent interactions render some stabilization to the associated species, they impact the kinetics and thermodynamics of photoinitiated electron transfer. Reported herein is a novel iridium(III) photocatalyst, equipped with an anion-sensitive, amide-substituted bipyridine ligand, and its reactivity with the halides (X = I, Br, Cl) in acetonitrile and dichloromethane. A noteworthy periodic trend was observed, where the size and electron affinity dramatically altered the observed photoredox behavior. The binding affinity for the halides increased with decreasing ionic radius ( ∼10 to >10) in a polar medium but association was stoichiometric for each halide in a nonpolar medium. Evidence for the static quenching of iodide and bromide is presented while dynamic quenching was observed with all halides. These results highlight how the photophysics of halide adducts and the thermodynamics of intra-ionic photo-oxidation are impacted as a consequence of preassociation of a quencher through hydrogen bonding.
通过使用非共价相互作用使反应物在光引发的氧化还原反应中预先缔合，这可能对激发态反应性产生重大影响。由于这些非共价相互作用会使相关物种具有一定的稳定性，它们会影响光引发电子转移的动力学和热力学。本文报道了一种新型铱（III）光催化剂，其配备了对阴离子敏感的酰胺取代联吡啶配体，以及它在乙腈和二氯甲烷中与卤化物（X = I、Br、Cl）的反应性。观察到了一个值得注意的周期性趋势，即尺寸和电子亲和力极大地改变了观察到的光氧化还原行为。在极性介质中，对卤化物的结合亲和力随着离子半径的减小（约10至>10）而增加，但在非极性介质中，每种卤化物的缔合是化学计量的。给出了碘化物和溴化物静态猝灭的证据，而所有卤化物均观察到动态猝灭。这些结果突出了由于猝灭剂通过氢键预先缔合，卤化物加合物的光物理性质和离子内光氧化的热力学是如何受到影响的。
