Faculté des sciences

A DFT based ligand field study of the EPR spectra of Co(II) and Cu(II) porphyrins

Atanasov, Mihail ; Daul, Claude A. ; Rohmer, Marie-Madeleine ; Venkatachalam, Tamilmani

In: Chemical Physics Letters, 2006, vol. 427, no. 4-6, p. 449-454

Using a DFT based Ligand Field treatment (LFDFT) of the electronic structure of Co(II) and Cu(II) porphyrins (CoP and CuP) we analyse the origin of their EPR spectra. From a comparison between theoretical result on Co model clusters (CoP and CoP–ZnP dimer) we conclude that the g-tensor values are very sensitive to the axial coordination which stabilizes a ²A₁ ground state in good... More

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    Summary
    Using a DFT based Ligand Field treatment (LFDFT) of the electronic structure of Co(II) and Cu(II) porphyrins (CoP and CuP) we analyse the origin of their EPR spectra. From a comparison between theoretical result on Co model clusters (CoP and CoP–ZnP dimer) we conclude that the g-tensor values are very sensitive to the axial coordination which stabilizes a ²A₁ ground state in good agreement with experimental data. In contrast, DFT overestimates Cu–ligand covalency, leading to large discrepancy with experiments, and hence the orbital contribution to the computed g-values is too small. Using a numerical adjustment of nuclear charge for Cu, a good agreement between the computed and the experimental g-tensor values is observed. The influence of the DFT functional on the calculated g-tensor is also discussed.