Halide Ligated Iron Porphines: A DFT plus U and UB3LYP Study


Panchmatia, P. M., Ali, M. E., Sanyal, B. and Oppeneer, P. M., 2010. Halide Ligated Iron Porphines: A DFT plus U and UB3LYP Study. The Journal of Physical Chemistry A, 114 (51), pp. 13381-13387.

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We apply the density functional theory + U (DFT+U) and unrestricted hybrid functional DFT-UB3LYP methods to study the electronic structure and magnetic properties of two prototypical iron porphines: porphine chloride (FePCl) and difluoro iron(III-IV) porphine. Plain DFT within the generalized gradient approximation (GGA) implementation fails in describing the correct high-spin ground state of these porphine molecules, whereas DFT+U and UB3LYP provide an improved description. For a range of U values (4-8 eV), we compare the results of the DFT+U approach to those obtained previously with the hybrid functional (B3LYP) and with the CASPT2 approach. The DFT+U and UB3LYP methods successfully predict the molecular high spin (S = 5/2) ground state of FePCl, and also provide the nontrivial S = 3 high spin ground state for FePF2. For the latter six-coordinated Fe porphine, our DFT+U calculations show that the S = 2, S = 5/2, and S = 3 states are energetically very close together (differences of 30 meV). Nonetheless, S = 3 is obtained as the ground state of the whole molecule, in accordance with the spin expected from the electron count. Our DFT+U calculations show furthermore that the Fe 3d occupancy is similar for FePF2 and FePCl, i.e., DET+U does not support Fe(IV) for FePF2, but rather an Fe(III) porphyrin pi-cation radical species, with an Fe high spin S-Fe = 5/2, and an additional S = 1/2 stemming from spin density distributed over the porphine ring. This observation is also supported by our UB3LYP calculations.


Item Type Articles
CreatorsPanchmatia, P. M., Ali, M. E., Sanyal, B. and Oppeneer, P. M.
DepartmentsFaculty of Science > Chemistry
ID Code22603


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