Molecular Geometry and Electronic Structure of Copper Corroles

Area of Science:

• Computational Chemistry
• Quantum Chemistry
• Materials Science

Background:

• Copper corroles possess complex multiconfigurational electronic structures.
• Density functional theory (DFT) struggles with accurate spin state and energetics determination, often due to Hartree-Fock exchange.
• Understanding these electronic properties is crucial for their applications.

Purpose of the Study:

• To investigate the molecular geometries and electronic structures of unsubstituted and meso-triphenyl copper corroles.
• To accurately determine the ground electronic state and energetics using advanced computational methods.
• To assess the performance of different density functional theory (DFT) functionals in describing these systems.

Main Methods:

• Employed extended multireference averaged quadratic stochastic perturbation theory (XMS-CASPT2) for electronic structure calculations.
• Utilized minimal and larger active spaces for structural and electronic characterization, respectively.
• Analyzed the potential energy surface (PES) between singlet and triplet states.

Main Results:

• Conclusively identified the ground state as a multiconfigurational singlet (S0) with a saddled structure.
• The planar triplet state (T0) was found to be approximately 5 kcal/mol higher in energy.
• XMS-CASPT2 revealed a transition towards a single electron configuration as the geometry approaches planarity.
• Only the TPSSh-D3 functional showed reasonable agreement with XMS-CASPT2 for the potential energy surface.

Conclusions:

• Copper corroles have a multiconfigurational singlet ground state with a characteristic saddled geometry.
• The choice of computational method and functional significantly impacts the accuracy of electronic structure and energetics.
• XMS-CASPT2 provides a reliable approach for studying the complex electronic behavior of copper corroles.