Antiferromagnetism in a Family of S = 1 Square Lattice Coordination Polymers NiX ₂ (pyz) ₂ (X = Cl, Br, I, NCS; pyz = Pyrazine)

Journal Article · Mon Apr 04 00:00:00 EDT 2016 · Inorganic Chemistry

DOI:https://doi.org/10.1021/acs.inorgchem.5b02991· OSTI ID:1392921

Liu, Junjie; Goddard, Paul A.; Singleton, John; Brambleby, Jamie; Foronda, Francesca; Möller, Johannes S.; Kohama, Yoshimitsu; Ghannadzadeh, Saman; Ardavan, Arzhang; Blundell, Stephen J.; Lancaster, Tom; Xiao, Fan; Williams, Robert C.; Pratt, Francis L.; Baker, Peter J.; Wierschem, Keola; Lapidus, Saul H.; Stone, Kevin H.; Stephens, Peter W.; Bendix, Jesper ; Woods, Toby J.; Carreiro, Kimberly E.; Tran, Hope E.; Villa, Cecelia J.; Manson, Jamie L.

The crystal structures of NiX2(pyz)(2) (X = Cl (1), Br (2), I (3), and NCS (4)) were determined by synchrotron X-ray powder diffraction. All four compounds consist of two-dimensional (2D) square arrays self-assembled from octahedral NiN4X2 units that are bridged by pyz ligands. The 2D layered motifs displayed by 1-4 are relevant to bifluoride-bridged [Ni(HF2) (pyz)(2)]EF6 (E = P, Sb), which also possess the same 2D layers. In contrast, terminal X ligands occupy axial positions in 1-4 and cause a staggered packing of adjacent layers. Long-range antiferromagnetic (AFM) order occurs below 1.5 (Cl), 1.9 (Br and NCS), and 2.5 K (I) as determined by heat capacity and muon-spin relaxation. The single-ion anisotropy and g factor of 2, 3, and 4 were measured by electron-spin resonance with no evidence for zero field splitting (ZFS) being observed. The magnetism of 1-4 spans the spectrum from quasi-two-dimensional (2D) to three-dimensional (3D) antiferromagnetism. Nearly identical results and thermodynamic features were obtained for 2 and 4 as shown by pulsed-field magnetization, magnetic susceptibility, as well as their Neel temperatures. Magnetization curves for 2 and 4 calculated by quantum Monte Carlo simulation also show excellent agreement with the pulsed-field data. Compound 3 is characterized as a 3D AFM with the interlayer interaction (j(perpendicular to)) being slightly stronger than the intralayer interaction along Ni-pyz-Ni segments (j(pyz)) within the two-dimensional [Ni(pyz)(2)](2+) square planes. Regardless of X, j(pyz), is similar for the four compounds and is roughly 1 K.

• Research Organization: Argonne National Lab. (ANL), Argonne, IL (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 1392921
• Journal Information: Inorganic Chemistry, Vol. 55, Issue 7; ISSN 0020-1669
• Publisher: American Chemical Society (ACS)
• Country of Publication: United States
• Language: English