Evidence for Site-Specific Tunneling in H Atom Uptake at the Surface of Polyoxovanadate-Alkoxides

IF 8.5 Q1 CHEMISTRY, MULTIDISCIPLINARY

JACS Au Pub Date : 2026-09-28 Epub Date: 2026-08-19 DOI:10.1021/jacsau.6c00947

M. Rebecca A. Walls, Shannon E. Cooney, Ellen M. Matson

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Abstract

Lindqvist-type polyoxovanadate-alkoxides are used as atomically precise, soluble analogs of metal oxides to interrogate site-dependent (e.g., μ₂-oxido vs terminal oxido) tunneling in proton-coupled electron transfer (PCET). Variable-temperature kinetic isotope effect (VT-KIE) analysis reveals that H atom uptake at the μ₂-oxido site of [TBA]₂[V₆O₈(OCH₃)₁₁] proceeds via quantum mechanical tunneling in acetonitrile, evidenced by a temperature-independent KIE, a small isotopic effect on activation energy, and positive Arrhenius prefactor ratio. This behavior is in contrast to PCET at the terminal vanadyl site of [TBA][V₆O₇(OCH₃)₁₂], which follows a semiclassical, concerted proton–electron transfer mechanism. Tunneling effects are solvent dependent; switching to dimethylformamide, a more basic solvent, results in a reduction in H-bonding interactions with the acceptor, lowering the observed rate of H atom uptake at the bridging site. This work highlights the role of site-specific basicity on tunneling in metal oxides, where competitive H-bonding with solvent disrupts tunneling.

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多氧钒酸盐-烷氧化合物表面H原子吸收的位点特异性隧穿证据

林德奎斯特型多氧钒酸盐烷氧化合物是一种原子精确的、可溶的金属氧化物类似物，用于检测位点依赖性(例如：质子耦合电子转移（PCET）中μ2-氧化物与末端氧化物的隧道效应。变温动力学同位素效应（VT-KIE）分析表明，[TBA]2[V6O8(OCH3)11]的μ2氧化位点的H原子吸收是通过量子力学隧道在乙腈中进行的，证明了温度无关的KIE、对活化能的小同位素效应和正的Arrhenius前因子比。这种行为与[TBA][V6O7(OCH3)12]末端钒基位的PCET形成对比，后者遵循半经典的协调质子-电子转移机制。隧道效应与溶剂有关；切换到二甲基甲酰胺，一种碱性更强的溶剂，会导致与受体的氢键相互作用减少，降低桥接部位的氢原子吸收的观察值。这项工作强调了特定碱度在金属氧化物中隧穿的作用，其中与溶剂的竞争性氢键破坏了隧穿。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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