Quasi-2D Heisenberg Antiferromagnets [CuX(pyz) 2 ](BF 4 ) with X = Cl and Br

Kubus, Mariusz; Lanza, Arianna; Scatena, Rebecca; Dos Santos, Leonardo H. R.; Wehinger, Björn; Casati, Nicola; Fiolka, Christoph; Keller, Lukas; Macchi, Piero; Rüegg, Christian; Krämer, Karl (2018). Quasi-2D Heisenberg Antiferromagnets [CuX(pyz) 2 ](BF 4 ) with X = Cl and Br. Inorganic chemistry, 57(9), pp. 4934-4943. American Chemical Society 10.1021/acs.inorgchem.7b03150

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Two Cu2+ coordination polymers [CuCl(pyz)2](BF4) 1 and [CuBr(pyz)2](BF4) 2 (pyz = pyrazine) were synthesized in the family of quasi two-dimensional (2D) [Cu(pyz)2]2+ magnetic networks. The layer connectivity by monatomic halide ligands results in significantly shorter interlayer distances. Structures were determined by single-crystal X-ray diffraction. Temperature-dependent X-ray diffraction of 1 revealed rigid [Cu(pyz)2]2+ layers that do not expand between 5 K and room temperature, whereas the expansion along the c-axis amounts to 2%. The magnetic susceptibility of 1 and 2 shows a broad maximum at ∼8 K, indicating antiferromagnetic interactions within the [Cu(pyz)2]2+ layers. 2D Heisenberg model fits result in J∥ = 9.4(1) K for 1 and 8.9(1) K for 2. The interlayer coupling is much weaker with |J⊥| = 0.31(6) K for 1 and 0.52(9) K for 2. The electron density, experimentally determined and calculated by density functional theory, confirms the location of the singly occupied orbital (the magnetic orbital) in the tetragonal plane. The analysis of the spin density reveals a mainly σ-type exchange through pyrazine. Kinks in the magnetic susceptibility indicate the onset of long-range three-dimensional magnetic order below 4 K. The magnetic structures were determined by neutron diffraction. Magnetic Bragg peaks occur below TN = 3.9(1) K for 1 and 3.8(1) K for 2. The magnetic unit cell is doubled along the c-axis (k = 0, 0, 0.5). The ordered magnetic moments are located in the tetragonal plane and amount to 0.76(8) μB/Cu2+ for 1 and 0.6(1) μB/Cu2+ for 2 at 1.5 K. The moments are coupled antiferromagnetically both in the ab plane and along the c-axis. The Cu2+ g-tensor was determined from electron spin resonance spectra as gx = 2.060(1), gz = 2.275(1) for 1 and gx = 2.057(1), gz = 2.272(1) for 2 at room temperature.

Item Type:

Journal Article (Original Article)

Division/Institute:

08 Faculty of Science > Departement of Chemistry and Biochemistry

UniBE Contributor:

Macchi, Piero and Krämer, Karl

Subjects:

500 Science > 570 Life sciences; biology
500 Science > 540 Chemistry

ISSN:

0020-1669

Publisher:

American Chemical Society

Funders:

[4] Swiss National Science Foundation

Language:

English

Submitter:

Piero Macchi

Date Deposited:

29 May 2018 15:10

Last Modified:

20 Jul 2018 13:59

Publisher DOI:

10.1021/acs.inorgchem.7b03150

BORIS DOI:

10.7892/boris.116882

URI:

https://boris.unibe.ch/id/eprint/116882

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