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Correlating EPR Parameters With Structural Anisotropy in Cu(II) Complexes
Sriparna Roy1, Anirban Misra1, Satadal Paul2
1Department of Chemistry, University of North Bengal, Darjeeling, India.
Journal of Computational Chemistry
|February 23, 2026
Summary
Quantum chemical calculations link molecular geometry to Electron Paramagnetic Resonance (EPR) parameters in Cu(II) complexes. Metal-ligand bonds influence spin orbit coupling and g-value shifts, revealing spin distribution patterns.
Area of Science:
- Computational Chemistry
- Quantum Chemistry
- Spectroscopy
Background:
- Electron Paramagnetic Resonance (EPR) parameters provide insights into the electronic structure and geometry of open-shell molecules.
- Interpreting EPR parameters like g-tensor and hyperfine coupling constants requires robust theoretical frameworks.
- Understanding the relationship between molecular geometry and spectroscopic features is crucial for characterizing transition metal complexes.
Purpose of the Study:
- To elucidate the electronic structure origins of spectroscopic behavior in pseudo-octahedral Cu(II) systems.
- To correlate molecular geometry with EPR parameters, specifically the g-tensor and hyperfine coupling constants.
- To determine the orientation of the g-tensor relative to the molecular coordinate frame using advanced computational methods.
Main Methods:
- Employed Density Functional Theory (DFT) and wave function-based theories to compute spin Hamiltonian parameters.
- Utilized multireference configuration interaction (MRCI) calculations to determine spin orbit coupling (SOC) and g-tensor orientation.
- Analyzed the shift in the free electron g-value (Δg) as a fingerprint of geometry and electronic structure.
Main Results:
- Established a correlation between metal-ligand bond characteristics, orbital degeneracy, SOC, and Δg values.
- Demonstrated that the isotropic (Aiso) and parallel (A∥) hyperfine coupling constants reflect spin distribution, with higher values indicating greater spin density on the ligand atom due to covalency.
- Successfully mapped EPR parameters to molecular geometry using electronic structure information.
Conclusions:
- Quantum chemical calculations provide a reliable interpretation of EPR parameters, linking molecular geometry and electronic structure in Cu(II) complexes.
- The study highlights the sensitivity of EPR parameters to subtle changes in metal-ligand bonding and molecular symmetry.
- This work offers a computational approach to orienting the g-tensor and understanding spin distribution in transition metal systems.
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