Electronic structures of Group 9 metallocorroles with axial ammines

Area of Science:

• Inorganic Chemistry
• Computational Chemistry
• Quantum Chemistry

Background:

• Metallocorroles are macrocyclic complexes with diverse applications.
• Understanding their electronic structure is crucial for predicting reactivity and properties.
• Fluorinated corroles offer tunable electronic properties.

Purpose of the Study:

• To compute and analyze the electronic structures of fluorinated metallocorroles (tpfc)M(NH3)2 and (tfc)M(NH3)2 (M = Co, Rh, Ir).
• To investigate the oxidation mechanism and its effect on metal reduction potentials.
• To examine the energy levels of excited states in oxidized metallocorroles.

Main Methods:

• First-principles quantum mechanics calculations using Density Functional Theory (DFT) with B3LYP functional.
• Poisson-Boltzmann continuum solvation model for accurate electronic structure.
• Geometry optimization for neutral (M(III)) and one-electron oxidized (M(IV)) states.

Main Results:

• One-electron oxidation occurs from a ligand-based Highest Occupied Molecular Orbital (HOMO) of B(1) symmetry for all metals.
• The formal M(IV) state exhibits M(III)-Cπ character, with the hole localized in the corrole π system.
• Calculated M(IV/III) reduction potentials are similar across Co, Rh, and Ir analogues (0.56–0.67 V vs SCE).
• Excited states with metal character are well-separated in Co and Rh, but closer in Ir complexes.

Conclusions:

• The electronic structure and oxidation mechanism of these metallocorroles are primarily ligand-dominated.
• The similarity in reduction potentials is attributed to ligand-based oxidation.
• Electronic properties, particularly excited state energies, show variations across the metal series (Co, Rh, Ir).