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Assessment of Quantum Mechanical Methods for Copper and Iron Complexes by Photoelectron Spectroscopy.

Niu S, Huang DL, Dau PD, Liu HT, Wang LS, Ichiye T - J Chem Theory Comput (2014)

Bottom Line: The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by ∼400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree-Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes.Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC-ωPBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still ∼150 meV too low for the Cu complexes and ∼50 meV too high for the Fe complexes.Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Georgetown University , Washington, DC 20057, United States.

ABSTRACT
Broken-symmetry density functional theory (BS-DFT) calculations are assessed for redox energetics [Cu(SCH3)2](1-/0), [Cu(NCS)2](1-/0), [FeCl4](1-/0), and [Fe(SCH3)4](1-/0) against vertical detachment energies (VDE) from valence photoelectron spectroscopy (PES), as a prelude to studies of metalloprotein analogs. The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by ∼400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree-Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes. Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC-ωPBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still ∼150 meV too low for the Cu complexes and ∼50 meV too high for the Fe complexes. Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

No MeSH data available.


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Schematic Kohn–Sham molecular orbitalinteraction diagramsbased on M06/DZVP2 calculations (a) between Cu+ and SCH3–and the HOMOs of [Cu(SCH3)2]1– and (b) between Cu+ and NCS–and the HOMOs of [Cu(NCS)2]1–.
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fig3: Schematic Kohn–Sham molecular orbitalinteraction diagramsbased on M06/DZVP2 calculations (a) between Cu+ and SCH3–and the HOMOs of [Cu(SCH3)2]1– and (b) between Cu+ and NCS–and the HOMOs of [Cu(NCS)2]1–.

Mentions: KS MO interactiondiagrams between the Cu1+ and the ligands for [Cu(SCH3)2]1– and [Cu(NCS)2]1– (Figure 3) were examinedto consistency with the PES results. This figure is based on the M06/DZVP2calculations but is representative of the B3LYP results as well. Afull analysis of the calculated electronic structure and the PES spectrumwill be presented elsewhere.


Assessment of Quantum Mechanical Methods for Copper and Iron Complexes by Photoelectron Spectroscopy.

Niu S, Huang DL, Dau PD, Liu HT, Wang LS, Ichiye T - J Chem Theory Comput (2014)

Schematic Kohn–Sham molecular orbitalinteraction diagramsbased on M06/DZVP2 calculations (a) between Cu+ and SCH3–and the HOMOs of [Cu(SCH3)2]1– and (b) between Cu+ and NCS–and the HOMOs of [Cu(NCS)2]1–.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3958136&req=5

fig3: Schematic Kohn–Sham molecular orbitalinteraction diagramsbased on M06/DZVP2 calculations (a) between Cu+ and SCH3–and the HOMOs of [Cu(SCH3)2]1– and (b) between Cu+ and NCS–and the HOMOs of [Cu(NCS)2]1–.
Mentions: KS MO interactiondiagrams between the Cu1+ and the ligands for [Cu(SCH3)2]1– and [Cu(NCS)2]1– (Figure 3) were examinedto consistency with the PES results. This figure is based on the M06/DZVP2calculations but is representative of the B3LYP results as well. Afull analysis of the calculated electronic structure and the PES spectrumwill be presented elsewhere.

Bottom Line: The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by ∼400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree-Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes.Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC-ωPBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still ∼150 meV too low for the Cu complexes and ∼50 meV too high for the Fe complexes.Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Georgetown University , Washington, DC 20057, United States.

ABSTRACT
Broken-symmetry density functional theory (BS-DFT) calculations are assessed for redox energetics [Cu(SCH3)2](1-/0), [Cu(NCS)2](1-/0), [FeCl4](1-/0), and [Fe(SCH3)4](1-/0) against vertical detachment energies (VDE) from valence photoelectron spectroscopy (PES), as a prelude to studies of metalloprotein analogs. The M06 and B3LYP hybrid functionals give VDE that agree with the PES VDE for the Fe complexes, but both underestimate it by ∼400 meV for the Cu complexes; other hybrid functionals give VDEs that are an increasing function of the amount of Hartree-Fock (HF) exchange and so cannot show good agreement for both Cu and Fe complexes. Range-separated (RS) functionals appear to give a better distribution of HF exchange since the negative HOMO energy is approximately equal to the VDEs but also give VDEs dependent on the amount of HF exchange, sometimes leading to ground states with incorrect electron configurations; the LRC-ωPBEh functional reduced to 10% HF exchange at short-range give somewhat better values for both, although still ∼150 meV too low for the Cu complexes and ∼50 meV too high for the Fe complexes. Overall, the results indicate that while HF exchange compensates for self-interaction error in DFT calculations of both Cu and Fe complexes, too much may lead to more sensitivity to nondynamical correlation in the spin-polarized Fe complexes.

No MeSH data available.


Related in: MedlinePlus