title: Experimental and Theoretical Electron Density Analysis of Copper Pyrazine Nitrate Quasi-Low-Dimensional Quantum Magnets.
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.
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, 3012 Bern, Switzerland.
authors.forename: Leonardo H R
authors.initials: LH
authors.lastname: Dos Santos
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, 3012 Bern, Switzerland.
authors.forename: Arianna
authors.initials: A
authors.lastname: Lanza
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , 226 Science, Cheney, Washington 99004, United States.
authors.forename: Alyssa M
authors.initials: AM
authors.lastname: Barton
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.
authors.forename: Jamie
authors.initials: J
authors.lastname: Brambleby
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.
authors.forename: William J A
authors.initials: WJ
authors.lastname: Blackmore
authors.affiliation: Department of Physics, University of Warwick , Gibbet Hill Road, Coventry CV4 7AL, United Kingdom.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Goddard
authors.affiliation: Department of Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Fan
authors.initials: F
authors.lastname: Xiao
authors.affiliation: Department of Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Williams
authors.affiliation: Department of Physics, Durham University , South Road, Durham DH1 3LE, United Kingdom.
authors.forename: Tom
authors.initials: T
authors.lastname: Lancaster
authors.affiliation: ISIS Facility, STFC Rutherford Appleton Laboratory , Chilton, Oxon OX11 0QX, United Kingdom.
authors.forename: Francis L
authors.initials: FL
authors.lastname: Pratt
authors.affiliation: Clarendon Laboratory, Department of Physics, University of Oxford , Oxford OX1 3PU, United Kingdom.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Blundell
authors.affiliation: National High Magnetic Field Laboratory, Los Alamos National Laboratory , Los Alamos, New Mexico 87545, United States.
authors.forename: John
authors.initials: J
authors.lastname: Singleton
authors.affiliation: Department of Chemistry and Biochemistry, Eastern Washington University , 226 Science, Cheney, Washington 99004, United States.
authors.forename: Jamie L
authors.initials: JL
authors.lastname: Manson
authors.affiliation: Department of Chemistry and Biochemistry, University of Bern , Freiestrasse 3, 3012 Bern, Switzerland.
authors.forename: Piero
authors.initials: P
authors.lastname: Macchi