Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

Zbiri, Mohamed

doi:10.1016/j.ica.2006.05.020

Cited by 6 publications

(5 citation statements)

References 46 publications

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“…The “boat” and “chair” conformations refer to the orientations of the BF 2 caps with respect to the macrocycle plane. Unlike the four-coordinate Co(II) complexes investigated by Zbiri, our calculated g values do not change significantly when other hybrid functionals are used. Before discussing in detail the results of the calculations, some critical issues regarding the accuracy and reliability of the calculations are addressed briefly.…”

Section: Dft Resultscontrasting

confidence: 61%

“…To the best of our knowledge, these are the first published EPR parameter calculations for singly and doubly ligated Co(II) cobaloxime complexes. Previous semiempirical calculations focused on the effect of the cobalt displacement on the energetics of the compound and four-coordinate Co(II) complexes without axial ligands being reported . Recent DFT studies on cobaloxime did not report any magnetic parameters. , The structure of the cobaloxime complex allows multiple conformations of each cobaloxime–ligand(s) complex.…”

Section: Dft Resultsmentioning

confidence: 99%

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The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

et al. 2012

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Solar fuels research aims to mimic photosynthesis and devise integrated systems that can capture, convert, and store solar energy in the form of high-energy molecular bonds. Molecular hydrogen is generally considered an ideal solar fuel as its combustion is essentially pollution-free. Cobaloximes rank among the most promising earth-abundant catalysts for the reduction of protons to molecular hydrogen. We have used multifrequency EPR spectroscopy at X-band, Q-band, and D-band combined with DFT calculations to reveal electronic structure and establish correlations between structure, surroundings and catalytic activity of these complexes. To assess the strength and nature of ligand cobalt interactions, the BF2-capped cobaloxime, Co(dmgBF2)2, was studied in a variety of different solvents with a range of polarities and stoichiometric amounts of potential ligands to the cobalt ion. This allows the differentiation of labile and strongly coordinating axial ligands for the Co(II) complex. Labile, or weakly coordinating, ligands like methanol result in larger g-tensor anisotropy than strongly coordinating ligands like pyridine. Additionally, a coordination number effect is seen for the strongly coordinating ligands with both singly-ligated LCo(dmgBF2)2 and doubly-ligated L2Co(dmgBF2)2. The presence of two strongly coordinating axial ligands leads to the smallest g-tensor anisotropy. The relevance of the strength of the axial ligand(s) to the catalytic efficiency of Co(dmgBF2)2 is discussed. Finally, the influence of molecular oxygen and formation of Co(III) superoxide radicals LCo(dmgBF2)2O2• is studied. The experimental results are compared with a comprehensive set of DFT calculations on Co(dmgBF2)2 model systems with various axial ligands. Comparison with experimental values for the “key” magnetic parameters like g-tensor and 59Co hyperfine coupling tensor allows the determination of the conformation of the axially ligated Co(dmgBF2)2 complexes. The data presented here are vital for understanding the influence of solvent and ligand coordination on the catalytic efficiency of cobaloximes.

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Section: Dft Resultscontrasting

confidence: 61%

Section: Dft Resultsmentioning

confidence: 99%

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

et al. 2012

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“…The complexes Co(acacen) and [Co(Cp)(CO) 2 ] − have both been investigated using EPR − and for Co(acacen) also using X-ray crystallography . Theoretical investigations of EPR parameters for Co(acacen) and [Co(Cp)(CO) 2 ] − have also been conducted. − Turning to the nickel compounds, [Ni(mnt) 2 ] − (training set 1 ) has undergone intense investigation, and both structural and EPR data − are known. Theoretical data on EPR parameters also exist from several sources. ,, The corresponding complex in training set 2 is [Ni(en) 3 ] 2+ .…”

Section: Methodsmentioning

confidence: 99%

Optimized Basis Sets for Calculation of Electron Paramagnetic Resonance Hyperfine Coupling Constants: aug-cc-pVTZ-J for the 3d Atoms Sc–Zn

Hedegård

Kongsted

Sauer

2011

J. Chem. Theory Comput.

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The hyperfine coupling tensor of electron paramagnetic resonance (EPR), describing the interaction between an electron and a given nuclei, depends strongly on the electron density at the nucleus. With standard Gaussian-type orbital basis sets (GTOs), employed in most calculations, it is difficult to obtain converged results of the hyperfine coupling tensor, and basis sets with more flexible core regions have therefore been devised. To this class of core property basis sets belong the aug-cc-pVTZ-J basis sets developed for the s- and p-block atoms. Here, we extend the aug-cc-pVTZ-J basis sets to include the 3d elements Sc-Zn. The converged optimal basis sets are throughout the series described by a (25s17p10d3f2g)/[17s10p7d3f2g] contraction scheme, where four tight s-, one tight p-, and one tight d-type function have been added to the original aug-cc-pVTZ basis sets. The basis sets are generally contracted, and molecular orbital coefficients are used as contraction coefficients. By validation studies with different functionals and compounds, it is shown that the values of the contraction coefficient are effectively independent of the compound used in their generation and the exchange-correlation functional employed in the calculation.

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“…Here g RMC is the relativistic mass correction, g DC is the diamagnetic correction, and g OZ/SOC represents the orbital Zeeman and spin−orbit coupling contributions. 53 Potentiometric Studies. Equipment and Work Conditions.…”

Section: ■ Experimental Sectionmentioning

confidence: 99%

Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu²⁺and⁶⁴Cu²⁺

et al. 2013

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The synthesis and characterization of Hno1pa2py, a new tacn-based ligand, is reported. The complexation process with Cu(2+) was proved to be very fast even in acidic medium. Potentiometric titrations allowed us to establish that Hno1pa2py exhibits an overall low basicity as well as a high selectivity for Cu(2+) over Zn(2+) cations. The copper(II) complex was synthesized and characterized using UV-vis and EPR spectroscopies and density functional theory (DFT) calculations. The studies clearly showed that the [Cu(no1pa2py)](+) complex is present in solution as a mixture of two isomers in which the ligand is coordinated to the metal center using a N5O donor set with the metal center in a distorted octahedral geometry. The very high kinetic inertness of the [Cu(no1pa2py)](+) complex was demonstrated by using acid-assisted dissociation assays as well as cyclic voltammetry. Preliminary investigations of (64)Cu complexation were performed to validate the potential use of such chelating agent for further application in nuclear medicine. The X-ray crystal structures of copper(II) complexes of L1, the ester derivative of Hno1pa2py, have been determined.

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Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

Cited by 6 publications

References 46 publications

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

Optimized Basis Sets for Calculation of Electron Paramagnetic Resonance Hyperfine Coupling Constants: aug-cc-pVTZ-J for the 3d Atoms Sc–Zn

Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu²⁺and⁶⁴Cu²⁺

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Accurate predictions of the EPR parameters in planar cobalt(II) complexes by hybrid density functional theory

Cited by 6 publications

References 46 publications

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

The Hydrogen Catalyst Cobaloxime: A Multifrequency EPR and DFT Study of Cobaloxime’s Electronic Structure

Optimized Basis Sets for Calculation of Electron Paramagnetic Resonance Hyperfine Coupling Constants: aug-cc-pVTZ-J for the 3d Atoms Sc–Zn

Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu2+and64Cu2+

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Monopicolinate-dipicolyl Derivative of Triazacyclononane for Stable Complexation of Cu²⁺and⁶⁴Cu²⁺