Influence of HF2− geometry on magnetic interactions elucidated from polymorphs of the metal–organic framework [Ni(HF2)(pyz)2]PF6 (pyz = pyrazine)

Jamie L. Manson; Kimberly E. Carreiro; Saul H. Lapidus; Peter W. Stephens; Paul A. Goddard; Rico E. Del Sesto; Jesper Bendix; Saman Ghannadzadeh; Isabel Franke; John Singleton; Tom Lancaster; Johannes S. Möller; Peter J. Baker; Francis L. Pratt; Stephen J. Blundell; Jinhee Kang; Changhoon Lee; Myung-Hwan Whangbo

doi:10.1039/C2DT30113J

Influence of HF₂⁻ geometry on magnetic interactions elucidated from polymorphs of the metal–organic framework [Ni(HF₂)(pyz)₂]PF₆ (pyz = pyrazine)†

Jamie L. Manson,*^a Kimberly E. Carreiro,^a Saul H. Lapidus,^b Peter W. Stephens,^bc Paul A. Goddard,^d Rico E. Del Sesto,^e Jesper Bendix,^f Saman Ghannadzadeh,^d Isabel Franke,^d John Singleton,^g Tom Lancaster,^d Johannes S. Möller,^d Peter J. Baker,^h Francis L. Pratt,^h Stephen J. Blundell,^d Jinhee Kang,ⁱ Changhoon Leeⁱ and Myung-Hwan Whangboⁱ

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^a Department of Chemistry and Biochemistry, Eastern Washington University, 226 Science, Cheney, WA 99004, USA
E-mail: jmanson@ewu.edu
Fax: +(509)359-6973
Tel: +(509)359-2878

^b Department of Physics and Astronomy, State University of New York, Stony Brook, NY 11794, USA

^c Photon Sciences Directorate, Brookhaven National Laboratory, Upton, NY 11973, USA

^d Clarendon Laboratory, Department of Physics, University of Oxford, Oxford OX1 3PU, UK

^e MPA, Los Alamos National Laboratory, Los Alamos, NM 87545, USA

^f Department of Chemistry, University of Copenhagen, Copenhagen DK-2100, Denmark

^g NHMFL, Los Alamos National Laboratory, Los Alamos, NM 87545, USA

^h ISIS Pulsed Muon Facility, Rutherford-Appleton Laboratory, Chilton, Oxfordshire OX11 0QX, UK

ⁱ Department of Chemistry, North Carolina State University, Raleigh, NC 27695, USA

Abstract

A tetragonal polymorph of [Ni(HF₂)(pyz)₂]PF₆ (designated β) is isomorphic to its SbF₆-congener at 295 K and features linear Ni–FHF–Ni pillars. Enhancements in the spin exchange (J_FHF = 7.7 K), Néel temperature (T_N = 7 K), and critical field (B_c = 24 T) were found relative to monoclinic α-PF₆. DFT reveals that the HF₂⁻ bridges are significantly better mediators of magnetic exchange than pyz (J_pyz), where J_FHF ≈ 3J_pyz, thus leading to quasi-1D behavior. Spin density resides on all atoms of the HF₂⁻ bridge whereas N-donor atoms of the pyz ring bear most of the density.

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Influence of HF₂⁻ geometry on magnetic interactions elucidated from polymorphs of the metal–organic framework [Ni(HF₂)(pyz)₂]PF₆ (pyz = pyrazine)†

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Influence of HF₂⁻ geometry on magnetic interactions elucidated from polymorphs of the metal–organic framework [Ni(HF₂)(pyz)₂]PF₆ (pyz = pyrazine)

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