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Bonding quandary in the [Cu3S2]3+ core: Insights from the analysis of domain averaged fermi holes and the local spin

The electronic structure of the trinuclear symmetric complex [(tmedaCu)3S2 ]3+, whose Cu3S 2 core represents a model of the active site of metalloenzymes involved in biological processes, has been in recent years the subject of vigorous debate. The complex exists as an open-shell triplet, and discussions concerned the question whether there is a direct S-S bond in the [Cu 3S2]3+ core, whose answer is closely related to the problem of the formal oxidation state of Cu atoms. In order to contribute to the elucidation of the serious differences in the conclusions of earlier studies, we report in this study the detailed comprehensive analysis of the electronic structure of the [Cu3S2]3+ core using the methodologies that are specifically designed to address three particular aspects of the bonding in the core of the above complex, namely, the presence and/or absence of direct S-S bond, the existence and the nature of spin-spin interactions among the atoms in the core, and the formal oxidation state of Cu atoms in the core. Using such a combined approach, it was possible to conclude that the picture of bonding consistently indicates the existence of a weak direct two-center-three-electron (2c-3e) S-S bond, but at the same time, the observed lack of any significant local spin in the core of the complex is at odds with the suggested existence of antiferromagnetic coupling among the Cu and S atoms, so that the peculiarities of the bonding in the complex seem to be due to extensive delocalization of the unpaired spin in the [Cu 3S2]3+ core. Finally, a scrutiny of the effective atomic hybrids and their occupations points to a predominant formal CuII oxidation state, with a weak contribution of partial Cu I character induced mainly by the partial flow of electrons from S to Cu atoms and high delocalization of the unpaired spin in the [Cu 3S2]3+ core

This study was supported by the grant of the Grant Agency of the Czech Republic (grant No: 203/09/0118). This support is gratefully acknowledged by R.P. P.S. and E.RC. also acknowledge financial support from the Spanish Ministerio de Ciencia y Tecnologia (project No. MAT2008-04834 and CTQ2011-23441/BQU) and from the Spanish FPU program (Grant No. AP2008-01231)

© Journal of Physical Chemistry A, 2013, vol. 117, núm. 9, p. 1975-1982

American Chemical Society (ACS)

Author: Ponec, Robert
Ramos-Cordoba, Eloy
Salvador Sedano, Pedro
Date: 2013 March 7
Abstract: The electronic structure of the trinuclear symmetric complex [(tmedaCu)3S2 ]3+, whose Cu3S 2 core represents a model of the active site of metalloenzymes involved in biological processes, has been in recent years the subject of vigorous debate. The complex exists as an open-shell triplet, and discussions concerned the question whether there is a direct S-S bond in the [Cu 3S2]3+ core, whose answer is closely related to the problem of the formal oxidation state of Cu atoms. In order to contribute to the elucidation of the serious differences in the conclusions of earlier studies, we report in this study the detailed comprehensive analysis of the electronic structure of the [Cu3S2]3+ core using the methodologies that are specifically designed to address three particular aspects of the bonding in the core of the above complex, namely, the presence and/or absence of direct S-S bond, the existence and the nature of spin-spin interactions among the atoms in the core, and the formal oxidation state of Cu atoms in the core. Using such a combined approach, it was possible to conclude that the picture of bonding consistently indicates the existence of a weak direct two-center-three-electron (2c-3e) S-S bond, but at the same time, the observed lack of any significant local spin in the core of the complex is at odds with the suggested existence of antiferromagnetic coupling among the Cu and S atoms, so that the peculiarities of the bonding in the complex seem to be due to extensive delocalization of the unpaired spin in the [Cu 3S2]3+ core. Finally, a scrutiny of the effective atomic hybrids and their occupations points to a predominant formal CuII oxidation state, with a weak contribution of partial Cu I character induced mainly by the partial flow of electrons from S to Cu atoms and high delocalization of the unpaired spin in the [Cu 3S2]3+ core
This study was supported by the grant of the Grant Agency of the Czech Republic (grant No: 203/09/0118). This support is gratefully acknowledged by R.P. P.S. and E.RC. also acknowledge financial support from the Spanish Ministerio de Ciencia y Tecnologia (project No. MAT2008-04834 and CTQ2011-23441/BQU) and from the Spanish FPU program (Grant No. AP2008-01231)
Format: application/pdf
ISSN: 1089-5639 (versió paper)
1520-5215 (versió electrònica)
Document access: http://hdl.handle.net/10256/11531
Language: eng
Publisher: American Chemical Society (ACS)
Collection: MICINN/PN 2012-2014/CTQ2011-23441
MEC/2009-2011/MAT2008-04834
Reproducció digital del document publicat a: http://dx.doi.org/10.1021/jp309295r
Articles publicats (D-Q)
Is part of: © Journal of Physical Chemistry A, 2013, vol. 117, núm. 9, p. 1975-1982
Rights: Tots els drets reservats
Subject: Complexos metàl·lics de transició
Transition metal complexes
Enllaços químics
Chemical bonds
Funcions d’ona
Wave functions
València (Química teòrica)
Valence (Theoretical chemistry)
Title: Bonding quandary in the [Cu3S2]3+ core: Insights from the analysis of domain averaged fermi holes and the local spin
Type: info:eu-repo/semantics/article
Repository: DUGiDocs

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