# Mechanistic Insights and Catalytic Efficiency of a 2,2′‐Bipyridine–Coordinated Peroxidovanadium Complex as a Haloperoxidase Biomimetic

## TL;DR

A new vanadium complex mimics natural enzymes to efficiently and sustainably halogenate organic compounds under mild conditions.

## Contribution

A peroxidovanadium(V) complex is presented as an efficient biomimetic catalyst for halogenation, with mechanistic and catalytic insights revealed through computational and experimental studies.

## Key findings

- The complex catalyzes oxidative bromination of phenol red with a rate constant of 990 ± 90 mol−2 L2 min−1.
- High-yield halogenation of 8-hydroxyquinoline (73% and 86% for bromo and iodo products) occurs under mild conditions.
- Catalyst regeneration via H2O2 coordination is exergonic, supporting sustainable turnover.

## Abstract

The peroxidovanadium(V) complex [VVO(O2)(HO2)(bpy)]·3H2O·0.5bpy (1), where bpy = 2,2′‐bypiridine, featuring η
2‐coordinated peroxide and hydroperoxide ligands, is reported as an efficient functional model of vanadium haloperoxidases (VHPOs). Structural and spectroscopic analyses indicate similarities between 1 and VHPO active sites, including peroxide ligand protonation. Mechanistic studies employing ab initio computational methods are based on the presence of [VVO(O2)(HO2)(bpy)] and its aqueous equilibrium species [VVO(O2)(HO2)(H2O)], in solutions of 1 (pH = 5.8). For each compound, two reaction pathways are explored for the oxidation of iodide and bromide: 1) direct HOX, where X = Br or I, formation through nucleophilic attack on the protonated η
2‐peroxide, affording ΔG
‡ = 20.0–26.5 kcal mol−1 and 2) V–OX intermediate formation after the nucleophilic attack on the η
2‐peroxide resulting in ΔG
‡ = 15.6–17.6 kcal mol−1. Catalyst regeneration via end‐on H2O2 coordination is exergonic (ΔG = −15.2 and −21.6 kcal mol−1), indicating sustainable turnover. Complex 1 catalyzes the oxidative bromination of phenol red with a rate constant of 990 ± 90 mol−2 L2 min−1 and achieves high‐yield halogenation of 8‐hydroxyquinoline (73 and 86% for 5,7‐dibromoquinolin‐8‐ol and 5,7‐diiodoquinolin‐8‐ol) in mild conditions (30 °C, pH 5.8). The results highlight 1 as an efficient catalyst, with potential applications in the pharmaceutical and agrochemical industries.

A peroxidovanadium(V) complex mimics vanadium haloperoxidases for eco‐friendly halogenation of organic substrates. Density functional theory studies reveal two major reaction pathways for iodide/bromide oxidation. The catalyst offers high‐yield bromination/iodination of 8‐hydroxyquinoline (73/86%) under mild conditions (30 °C, pH 5.8), and it also oxidizes phenol red (990 ± 90 mol−2 L2 min−1) efficiently to bromophenol blue.© 2025 WILEY‐VCH GmbH