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Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets

Type of publication Peer-reviewed
Publikationsform Original article (peer-reviewed)
Author Dos Santos, Leonardo; Lanza, Arianna; Barton, A. M.; Brambleby, J.; Blackmore, W. J. A.; Goddard, P. A.; Xiao, F.; Williams, R. C.; Lancaster, T.; Pratt, F. L.; Blundell, S. J.; Singleton, J.; Manson, J. L. ; Macchi, P.
Project Physical and chemical properties from the electron density distribution of materials
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Original article (peer-reviewed)

Journal Journal of The American Chemical Society
Volume (Issue) 138
Page(s) 2280
Title of proceedings Journal of The American Chemical Society
DOI 10.1021/jacs.5b12817

Open Access

URL https://boris.unibe.ch/id/eprint/78906
Type of Open Access Repository (Green Open Access)

Abstract

The accurate electron density distribution and magnetic properties of two metal-organic polymeric magnets, the quasi-one-dimensional (1D) Cu(pyz)(NO3)2 and the quasi-two-dimensional (2D) [Cu(pyz)2(NO3)]NO3·H2O, have been investigated by high-resolution single-crystal X-ray diffraction and density functional theory calculations on the whole periodic systems and on selected fragments. Topological analyses, based on quantum theory of atoms in molecules, enabled the characterization of possible magnetic exchange pathways and the establishment of relationships between the electron (charge and spin) densities and the exchange-coupling constants. In both compounds, the experimentally observed antiferromagnetic coupling can be quantitatively explained by the Cu-Cu superexchange pathway mediated by the pyrazine bridging ligands, via a σ-type interaction. From topological analyses of experimental charge-density data, we show for the first time that the pyrazine tilt angle does not play a role in determining the strength of the magnetic interaction. Taken in combination with molecular orbital analysis and spin density calculations, we find a synergistic relationship between spin delocalization and spin polarization mechanisms and that both determine the bulk magnetic behavior of these Cu(II)-pyz coordination polymers.
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