Cook Emma N, Flaxman Luke A, Reid Amelia G, Dickie Diane A, Machan Charles W
Department of Chemistry, University of Virginia, PO Box 400319, Charlottesville, Virginia 22904-4319, United States.
J Am Chem Soc. 2024 Sep 11;146(36):24892-24900. doi: 10.1021/jacs.4c05708. Epub 2024 Aug 29.
Development of earth-abundant catalysts for the reduction of dioxygen (ORR) is essential for the development of alternative industrial processes and energy sources. Here, we report a transition metal-free dicationic organocatalyst () for the ORR. The ORR performance of this compound was studied in acetonitrile solution under both electrochemical conditions and spectrochemical conditions, using halogenated acetic acid derivatives spanning a p range of 12.65 to 20.3. Interestingly, it was found that under electrochemical conditions, a kinetically relevant peroxo dimer species forms with all acids. However, under spectrochemical conditions, strong acids diminish the kinetic contribution of this dimer to the observed rate due to lower catalyst concentrations, whereas weaker acids were still rate-limited by the dimer equilibrium. Together, these results provide insight into the mechanisms of ORR by organic-based, metal-free catalysts, suggesting that balancing redox activity and unsaturated character of these molecules with respect to the p of intermediates can enable reaction tuning analogous to transition metal-based systems.
开发用于还原氧气（ORR）的地球丰富型催化剂对于替代工业流程和能源的发展至关重要。在此，我们报告了一种用于ORR的无过渡金属双阳离子有机催化剂（）。在电化学条件和光谱化学条件下，使用pKa范围为12.65至20.3的卤代乙酸衍生物，在乙腈溶液中研究了该化合物的ORR性能。有趣的是，发现在电化学条件下，与所有酸都会形成动力学相关的过氧二聚体物种。然而，在光谱化学条件下，强酸由于催化剂浓度较低而降低了该二聚体对观察到的速率的动力学贡献，而弱酸仍然受二聚体平衡的速率限制。这些结果共同为基于有机的无金属催化剂的ORR机制提供了见解，表明相对于中间体的pKa平衡这些分子的氧化还原活性和不饱和特性可以实现类似于基于过渡金属的系统的反应调控。
