Experimental spin density in nitroxides

Brown, P.; Capiomont, A.; Gillon, B.; Schweizer, J.

doi:10.1080/00268978300100551

Cited by 28 publications

(11 citation statements)

References 9 publications

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“…It indicates that anisotropic exchange contributions to the zero-field splitting should be dominant. [24] Spin-density reconstruction: We used the so-called HansenCoppens model, adapted to spin density, [25] to reconstruct the spin density from the experimental magnetic structure factors. The spin density is written as a sum of atomic spin densities which are developed over the basis of multipolar functions centered on atom i:…”

mentioning

confidence: 99%

Structure, Magnetic Properties, Polarized Neutron Diffraction, and Theoretical Study of a Copper(II) Cubane

Aronica

Chumakov

Jeanneau

et al. 2008

Chemistry A European J

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The paper reports the synthesis, X-ray and neutron diffraction crystal structures, magnetic properties, high field-high frequency EPR (HF-EPR), spin density and theoretical description of the tetranuclear CuII complex [Cu4L4] with cubane-like structure (LH2=1,1,1-trifluoro-7-hydroxy-4-methyl-5-aza-hept-3-en-2-one). The simulation of the magnetic behavior gives a predominant ferromagnetic interaction J1 (+30.5 cm(-1)) and a weak antiferromagnetic interaction J2 (-5.5 cm(-1)), which correspond to short and long Cu-Cu distances, respectively, as evidence from the crystal structure [see formulate in text]. It is in agreement with DFT calculations and with the saturation magnetization value of an S=2 ground spin state. HF-EPR measurements at low temperatures (5 to 30 K) provide evidence for a negative axial zero-field splitting parameter D (-0.25+/-0.01 cm(-1)) plus a small rhombic term E (0.025+/-0.001 cm(-1), E/D = 0.1). The experimental spin distribution from polarized neutron diffraction is mainly located in the basal plane of the CuII ion with a distortion of yz-type for one CuII ion. Delocalization on the ligand (L) is observed but to a smaller extent than expected from DFT calculations.

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mentioning

confidence: 99%

Structure, Magnetic Properties, Polarized Neutron Diffraction, and Theoretical Study of a Copper(II) Cubane

Aronica

Chumakov

Jeanneau

et al. 2008

Chemistry A European J

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“…Such a study has been previously reported for an EO [24] compound, but not for an EE system, despite the relevant information it may bring with respect to spin delocalization. [24,[38][39][40][41][42][43] We also performed complementary spin-density calculations using the DFT formalism. We also carried out correlated ab initio calculations to obtain information on the electronic mechanism of the magnetic interaction.…”

mentioning

confidence: 99%

Ferromagnetic Interaction in an Asymmetric End‐to‐End Azido Double‐Bridged Copper(II) Dinuclear Complex: A Combined Structure, Magnetic, Polarized Neutron Diffraction and Theoretical Study

Aronica

Jeanneau

Moll

et al. 2007

Chemistry A European J

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A new end-to-end azido double-bridged copper(II) complex [Cu(2)L(2)(N(3))2] (1) was synthesized and characterized (L=1,1,1-trifluoro-7-(dimethylamino)-4-methyl-5-aza-3-hepten-2-onato). Despite the rather long Cu-Cu distance (5.105(1) A), the magnetic interaction is ferromagnetic with J= +16 cm(-1) (H=-JS(1)S(2)), a value that has been confirmed by DFT and high-level correlated ab initio calculations. The spin distribution was studied by using the results from polarized neutron diffraction. This is the first such study on an end-to-end system. The experimental spin density was found to be localized mainly on the copper(II) ions, with a small degree of delocalization on the ligand (L) and terminal azido nitrogens. There was zero delocalization on the central nitrogen, in agreement with DFT calculations. Such a picture corresponds to an important contribution of the d(x2-y2) orbital and a small population of the d(z2) orbital, in agreement with our calculations. Based on a correlated wavefunction analysis, the ferromagnetic behavior results from a dominant double spin polarization contribution and vanishingly small ionic forms.

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“…Finally, the distribution of spin density on N and O atoms in each nitroxide group has been quite controversial for several decades. While standard first-principle calculations, at the (unrestricted) Hartree-Fock or DFT levels tend to attribute a significantly stronger contribution to the oxygen sites (for example, Gillon et al, 1983;Delley et al, 1984;Improta et al, 2002;Barone et al, 2009), analysis from PND consistently showed that the distribution was more evenly distributed between both atoms and sometimes the spin on the nitrogen sites is even more significant than on the oxygen sites (Brown et al, 1983;Bordeaux et al, 1993; Here again, the CASSCF calculations of this work tend to confirm this early experimental prediction by attributing an almost equal spin population to the oxygen and nitrogen atomic basins.…”

Section: Discussionmentioning

confidence: 99%

When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical

Voufack

Claiser

Lecomte

et al. 2017

Acta Crystallogr B Struct Sci Cryst Eng Mater

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Joint refinement of X-ray and polarized neutron diffraction data has been carried out in order to determine charge and spin density distributions simultaneously in the nitronyl nitroxide (NN) free radical Nit(SMe)Ph. For comparison purposes, density functional theory (DFT) and complete active-space self-consistent field (CASSCF) theoretical calculations were also performed. Experimentally derived charge and spin densities show significant differences between the two NO groups of the NN function that are not observed from DFT theoretical calculations. On the contrary, CASSCF calculations exhibit the same fine details as observed in spin-resolved joint refinement and a clear asymmetry between the two NO groups.

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Experimental spin density in nitroxides

Cited by 28 publications

References 9 publications

Structure, Magnetic Properties, Polarized Neutron Diffraction, and Theoretical Study of a Copper(II) Cubane

Structure, Magnetic Properties, Polarized Neutron Diffraction, and Theoretical Study of a Copper(II) Cubane

Ferromagnetic Interaction in an Asymmetric End‐to‐End Azido Double‐Bridged Copper(II) Dinuclear Complex: A Combined Structure, Magnetic, Polarized Neutron Diffraction and Theoretical Study

When combined X-ray and polarized neutron diffraction data challenge high-level calculations: spin-resolved electron density of an organic radical

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