Hydrogen Bonding Effect on the Oxygen Binding and Activation in Cobalt(III)-Peroxo Complexes

Area of Science:

• Inorganic Chemistry
• Coordination Chemistry
• Bioinorganic Chemistry

Background:

• Cobalt(III)peroxo complexes are crucial models for understanding oxygen activation in biological and chemical systems.
• Hydrogen bonding plays a significant role in modulating the reactivity and stability of metal complexes.

Purpose of the Study:

• To systematically investigate the impact of hydrogen bonding on O2 binding energy and O-O bond activation in cobalt(III)peroxo complexes.
• To explore the influence of varying numbers of amino groups in the secondary coordination sphere on these properties.

Main Methods:

• Synthesis of tris(pyridin-2-ylmethyl)amine-based cobalt(III)peroxo complexes with varying secondary coordination spheres.
• Gas-phase investigation using helium tagging infrared photodissociation spectroscopy.
• Energy-resolved collision-induced dissociation experiments and density functional theory calculations.

Main Results:

• Hydrogen bonding provides moderate stabilization (10-20 kJ mol⁻¹) to the cobalt(III)peroxo core.
• The first amino group in the secondary sphere yields the largest stabilization; additional groups offer diminishing returns.
• Hydrogen bonding facilitates O-O bond cleavage via hydrogen atom transfer, a thermodynamically favorable but entropically disfavored process.

Conclusions:

• Secondary coordination sphere hydrogen bonding is a key factor in tuning the stability and reactivity of cobalt(III)peroxo complexes.
• The extent of O-O bond activation is influenced by the interplay between thermodynamic favorability and entropic penalties.
• These findings offer insights into the mechanisms of oxygen activation relevant to catalysis and biological systems.