The structures and stabilities of [Cu₂(μ-η2:η2- peroxo)]2+ (A) and [Cu₂(μ-oxo)]2+ (B) complexes with three NH₃ ligands per copper are investigated using DFT and high-level ab initio methods. These are model systems for active centers in enzymes like hemocyanine and tyrosinase. Previous studies have shown that at the DFT/B3LYP level the peroxo form A is more stable than the μ-oxo form B, while the opposite was found using CASPT2 (Flock M, Pierloot K (1999) J Phys Chem 103:95). At the two computational levels, the energy difference of the isomers differed by more than 30 kcal/mol. In this work this problem is reinvestigated using a localized orbital description and multireference configuration interaction (MRCI) methods. It is found that CASPT2 strongly over-corrects the correlation effect and MRCI predicts structure A to be energetically lower than B, in qualitative agreement with B3LYP and experiment. However, B3LYP seems to stabilize the biradicalic structure A too much, and this effect depends approximately linearly on the amount of exact exchange in the B3LYP density functional. Reducing the amount of exact exchange to 10–15% yields good agreement between MRCI and B3LYP.
%0 Journal Article
%1 publ9336179
%A Rode, Michal F
%A Werner, Hans Joachim
%D 2005
%J Theor. Chem. Acc.
%K Ab complexes,[Cu₂(μ-η2:η2- werner theoretische stuttgart calculations,CASPT2,DFT,MRCI,Oxygen chemie activation,[Cu₂(μ-oxo)]2+dicopper-oxygen from:alexanderdenzel peroxo)]2+ initio theochem
%N 4-5
%P 309–317
%R 10.1007/s00214-005-0692-6
%T Ab initio study of the O₂ binding in dicopper complexes
%U http://dx.doi.org/10.1007/s00214-005-0692-6
%V 114
%X The structures and stabilities of [Cu₂(μ-η2:η2- peroxo)]2+ (A) and [Cu₂(μ-oxo)]2+ (B) complexes with three NH₃ ligands per copper are investigated using DFT and high-level ab initio methods. These are model systems for active centers in enzymes like hemocyanine and tyrosinase. Previous studies have shown that at the DFT/B3LYP level the peroxo form A is more stable than the μ-oxo form B, while the opposite was found using CASPT2 (Flock M, Pierloot K (1999) J Phys Chem 103:95). At the two computational levels, the energy difference of the isomers differed by more than 30 kcal/mol. In this work this problem is reinvestigated using a localized orbital description and multireference configuration interaction (MRCI) methods. It is found that CASPT2 strongly over-corrects the correlation effect and MRCI predicts structure A to be energetically lower than B, in qualitative agreement with B3LYP and experiment. However, B3LYP seems to stabilize the biradicalic structure A too much, and this effect depends approximately linearly on the amount of exact exchange in the B3LYP density functional. Reducing the amount of exact exchange to 10–15% yields good agreement between MRCI and B3LYP.
@article{publ9336179,
abstract = {The structures and stabilities of [Cu₂(μ-η2:η2- peroxo)]2+ (A) and [Cu₂(μ-oxo)]2+ (B) complexes with three NH₃ ligands per copper are investigated using DFT and high-level ab initio methods. These are model systems for active centers in enzymes like hemocyanine and tyrosinase. Previous studies have shown that at the DFT/B3LYP level the peroxo form A is more stable than the μ-oxo form B, while the opposite was found using CASPT2 (Flock M, Pierloot K (1999) J Phys Chem 103:95). At the two computational levels, the energy difference of the isomers differed by more than 30 kcal/mol. In this work this problem is reinvestigated using a localized orbital description and multireference configuration interaction (MRCI) methods. It is found that CASPT2 strongly over-corrects the correlation effect and MRCI predicts structure A to be energetically lower than B, in qualitative agreement with B3LYP and experiment. However, B3LYP seems to stabilize the biradicalic structure A too much, and this effect depends approximately linearly on the amount of exact exchange in the B3LYP density functional. Reducing the amount of exact exchange to 10–15% yields good agreement between MRCI and B3LYP.},
added-at = {2019-03-01T15:49:40.000+0100},
author = {Rode, Michal F and Werner, Hans Joachim},
biburl = {https://puma.ub.uni-stuttgart.de/bibtex/29a14a122551103dbc39dc833c51afb38/theochem},
doi = {10.1007/s00214-005-0692-6},
interhash = {2e4a5440ae27b54ce82e0797d51d96cd},
intrahash = {9a14a122551103dbc39dc833c51afb38},
issn = {1432881X},
journal = {Theor. Chem. Acc.},
keywords = {Ab complexes,[Cu₂(μ-η2:η2- werner theoretische stuttgart calculations,CASPT2,DFT,MRCI,Oxygen chemie activation,[Cu₂(μ-oxo)]2+dicopper-oxygen from:alexanderdenzel peroxo)]2+ initio theochem},
number = {4-5},
pages = {309–317},
timestamp = {2019-03-01T14:49:40.000+0100},
title = {{Ab initio study of the O₂ binding in dicopper complexes}},
url = {http://dx.doi.org/10.1007/s00214-005-0692-6},
volume = 114,
year = 2005
}