Interaction between copper(II) ions through the azido bridge:  concept of spin polarization and ab initio calculations on model systems

Charlot, Marie‐France; Kahn, Olivier; Chaillet, M.; Larrieu, C.

doi:10.1021/ja00270a014

Cited by 166 publications

(88 citation statements)

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“…In the azido complex the antiferromagnetic character of this contribution is larger ͑Ϫ59 cm Ϫ1 ͒. The role of spin polarization had been speculated to be very large 35 in this complex. It is actually large, but adding this contribution to the valence-only effects ͑SPCI results͒ the value of J only reaches Ϫ141 cm Ϫ1 , five times smaller than the experimental estimate ͑ϽϪ800 cm Ϫ1 ͒.…”

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confidence: 93%

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

Calzado

Cabrero

Malrieu

et al. 2002

The Journal of Chemical Physics

292

233

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Accurate estimates of the magnetic coupling in binuclear complexes can be obtained from ab initio configuration interaction ͑CI͒ calculations using the difference dedicated CI technique. The present paper shows that the same technique also provides a way to analyze the various physical contributions to the coupling and performs numerical analysis of their respective roles on four binuclear complexes of Cu (d 9 ) ions. The bare valence-only description ͑including direct and kinetic exchange͒ does not result in meaningful values. The spin-polarization phenomenon cannot be neglected, its sign and amplitude depend on the system. The two leading dynamical correlation effects have an antiferromagnetic character. The first one goes through the dynamical polarization of the environment in the ionic valence bond forms ͑i.e., the M ϩ¯MϪ structures͒. The second one is due to the double excitations involving simultaneously single excitations between the bridging ligand and the magnetic orbitals and single excitations of the environment. This dispersive effect results in an increase of the effective hopping integral between the magnetic orbitals. Moreover, it is demonstrated to be responsible for the previously observed larger metal-ligand delocalization occurring in natural orbitals with respect to the Hartree-Fock ones.

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confidence: 93%

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

Calzado

Cabrero

Malrieu

et al. 2002

The Journal of Chemical Physics

292

233

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“…This is why most previous theoretical studies focused on EO systems to explain such peculiar behavior, [24,[26][27][28][29][30] which was initially attributed to spin polarization effects. [28,30] However, a polarized neutron diffraction study has shown that spin delocalization is indeed the main effect and that spin polarization occurs only within the azido bridge. [24] Meanwhile, the magnetostructural independence of the ferromagnetic coupling was experimentally ruled out by Thompson et al who synthesized a series of dinuclear copper(II) complexes incorporating one symmetric m-1,1-azido bridge and one bridging diazine ligand to tune the opening of the Cu-N-Cu bridge angle.…”

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confidence: 99%

“…Moreover, at first sight, the antiferromagnetic coupling of the EE system seemed to be easy to explain if only the copper(II) coordination geometry and the bonding mode of the azido group were taken into consideration. [28] Thus, the strong antiferromagnetic interaction of symmetric EE systems was ascribed to the six-coordinate environment of the copper(II) ions with the two bridging azido groups favoring strong overlap between the d x 2 Ày 2 magnetic orbitals. [20,25] In the case of asymmetric EE systems, in which the copper generally has a square-pyramidal geometry, one terminal azido nitrogen atom points to the d x 2 Ày 2 magnetic orbital of one copper and the other to the d z 2 orbital of the second copper.…”

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confidence: 99%

“…This, combined with the long apical Cu À N azido bonds, was believed to give negligible interactions for pure square-pyramidal geometries that become sizeable antiferromagnetic interactions when the system evolves to a trigonal-bipyramidal geometry. [19,28] However, this interpretation appears no longer valid owing to the quite recent discovery of asymmetric EE systems showing ferromagnetic …”

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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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“…We report herein the synthesis, the structural characterization, and the magnetic properties of complex KRb 5 9À species in solution, is known. [6] Crystal structure analysis of compound 1 [7] shows that 1 can be described as the result of the formal removing of a {W 3 O 13 } group from the [a-PW 12 O 40 ] 3À ion followed by its replacement by a {WO 10 Ni 2 -(H 2 O) 2 [6a] for which, a treatment of the magnetic data revealed a mixture of several isomers. Two isomers contain neighboring Cu II ions, connected through a corner oxygen atom and an edge of their coordination octahedra, the other isomers being constructed of nonadjacent CuO 6 octahedra.…”

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A Polyoxometalate Containing the {Ni₂N₃} Fragment: Ferromagnetic Coupling in a Ni^II μ‐1,1 Azido Complex with a Large Bridging Angle

et al. 2004

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Dedicated to Professor M. T. Pope on the occasion of his 70th birthday.The chemistry of polyoxometalates (POMs) continues to attract much attention, particularly with respect to potential catalytic activity. [1] In the last few years it has also been noted that POMs are ideal models for the study of exchange interactions in magnetic clusters, as they represent a class of well-insulated complexes of controlled nuclearity and topology.[ [5] and that N 3 À is certainly one of the most interesting magnetic couplers known in molecular chemistry, we have decided to investigate the interaction of this ligand with magnetic POMs. Very recently, we have shown that the paramagnetic center of a Cu II POM can bind an azido group;[3e] nevertheless, the lack of structural information prevents any investigation of the magnetic properties of the compound obtained. We report herein the synthesis, the structural characterization, and the magnetic properties of complex KRb 5 [(PW 10 O 37 )(Ni(H 2 O)) 2 (m-N 3 )]·19 H 2 O (1), which is the first example of a fully characterized azido polyoxometalate. Moreover, the topology of the {Ni(m-1,1-N 3 )Ni} core in 1 is unprecedented, as no corner-sharing azido-bridged Ni II complex has been obtained to date. It follows that the Ni-N-Ni angle q in 1 is by far the largest observed in azido-ligand bridged Ni II compounds, a feature which should help the understanding of the relationships between structural parameters and the value of the magnetic exchange parameter J for m-1,1-N 3 complexes.Compound 1 9À species in solution, is known. [6] Crystal structure analysis of compound 1 [7] shows that 1 can be described as the result of the formal removing of a {W 3 O 13 } group from the [a-PW 12 O 40 ] 3À ion followed by its replacement by a {WO 10 Ni 2 -(H 2 O) 2 N 3 } fragment (Figure 1). Two crystallographically non-6À subunits (1 a and 1 b, containing the ions Ni(1) and Ni(2), respectively) have been found in the unit cell. The dinuclear {[Ni(H 2 O)] 2 N 3 } entities are highly similar in 1 a and 1 b (see Figure 1), and will be considered as identical for the forthcoming discussion. The paramagnetic centers are in an axially distorted octahedral environment. Indeed, an elongated NiÀO(PO 3 ) bond (d Ni-O = 2.273(5), 2.283(4) ) is observed in the position trans to the Ni À OH 2 bond (d NiÀOH 2 = 2.007(2), 2.018(4) ), the remaining Ni-O/N bonds are in the range 1.990(5)-2.081(5) . The two paramagnetic centers are bridged by one of the terminal nitrogen atoms of the azido ligand, which connects the

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Interaction between copper(II) ions through the azido bridge: concept of spin polarization and ab initio calculations on model systems

Cited by 166 publications

References 3 publications

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

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

A Polyoxometalate Containing the {Ni₂N₃} Fragment: Ferromagnetic Coupling in a Ni^II μ‐1,1 Azido Complex with a Large Bridging Angle

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Interaction between copper(II) ions through the azido bridge: concept of spin polarization and ab initio calculations on model systems

Cited by 166 publications

References 3 publications

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

Analysis of the magnetic coupling in binuclear complexes. I. Physics of the coupling

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

A Polyoxometalate Containing the {Ni2N3} Fragment: Ferromagnetic Coupling in a NiII μ‐1,1 Azido Complex with a Large Bridging Angle

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A Polyoxometalate Containing the {Ni₂N₃} Fragment: Ferromagnetic Coupling in a Ni^II μ‐1,1 Azido Complex with a Large Bridging Angle