Department of Chemistry - PhD Student Seminar - Redox-inactive Lewis Acids in Metal-oxo Chemistry

Student: Mr. Chun Yin HO

Department: Department of Chemistry, HKUST

Supervisor: Prof. Wa Hung LEUNG

Abstract

Redox-inactive metal ions are often found alongside redox-active transition-metal species in biological and synthetic systems. Although they do not directly participate in electron transfer, they can strongly influence the electronic structure, stability, and reactivity of nearby metal centers. A prominent example is Ca²⁺ in the Mn₄CaO₅ cluster of Photosystem II, where it is essential for efficient water oxidation despite remaining redox-inactive.

This seminar describes how Lewis-acidic metal ions such as Ca²⁺, Sr²⁺, Sc³⁺, Zn²⁺, Y³⁺, and Lu³⁺, affect and regulate the reactivity of metal–oxo complexes through electrostatic, structural, and coordination effects. The effects of redox-inactive metal ions on the electron transfer (ET), oxygen-atom transfer (OAT), O-O bond cleavage and evolution, and hydrogen-atom transfer (HAT) of metal-oxo complexes will be discussed. Selected molecular and multimetallic systems illustrating how changes in Lewis acidity of metal ions alter the reduction potentials, bond cleavage and formation, reaction rates, and reaction mechanisms of metal oxo complexes will be presented.