A Pseudo‐Octahedral Cobalt(II) Complex with Bispyrazolylpyridine Ligands Acting as a Zero‐Field Single‐Molecule Magnet with Easy Axis Anisotropy. Issue 35 (30th May 2018)

• Record Type: Journal Article
• Authors: Rigamonti, Luca; Bridonneau, Nathalie; Poneti, Giordano; Tesi, Lorenzo; Sorace, Lorenzo; Pinkowicz, Dawid; Jover, Jesus; Ruiz, Eliseo; Sessoli, Roberta; Cornia, Andrea
• Is Part Of: Chemistry. Volume 24:Issue 35(2018)
• Page Start: 8857
• Page End: 8868
• Publication Date: 2018-05-30
• Subjects: ab initio calculations -- cobalt -- EPR spectroscopy -- single-molecule magnets -- torque magnetometry; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201801026
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: The homoleptic mononuclear compound [Co(bpp‐COOMe)2 ](ClO4 )2 (1 ) (bpp‐COOMe=methyl 2, 6‐di(pyrazol‐1‐yl)pyridine‐4‐carboxylate) crystallizes in the monoclinic C 2/ c space group, and the cobalt(II) ion possesses a pseudo‐octahedral environment given by the two mer ‐coordinated tridentate ligands. Direct‐current magnetic data, single‐crystal torque magnetometry, and EPR measurements disclosed the easy‐axis nature of this cobalt(II) complex, which shows single‐molecule magnet behavior when a static field is applied in alternating‐current susceptibility measurements. Diamagnetic dilution in the zinc(II) analogue [Zn(bpp‐COOMe)2 ](ClO4 )2 (2 ) afforded the derivative [Zn0.95 Co0.05 (bpp‐COOMe)2 ](ClO4 )2 (3 ), which exhibits slow relaxation of magnetization even in zero field thanks to the reduction of dipolar interactions. Theoretical calculations confirmed the overall electronic structure and the magnetic scenario of the compound as drawn by experimental data, thus confirming the spin‐phonon Raman relaxation mechanism, and a direct quantum tunneling in the ground state as the most plausible relaxation pathway in zero field. Abstract : Distorted relaxation : The homoleptic high‐spin cobalt(II) compound [Co(bpp‐COOMe)2 ](ClO4 )2 (bpp‐COOMe=methyl 2, 6‐di(pyrazol‐1‐yl)pyridine‐4‐carboxylate) with two mer tridentate nitrogen‐rich ligands possesses the right distortion from the octahedral coordination geometry in order to show dominant easy‐axis anisotropy and slow relaxation of magnetization in the absence of an applied field once magnetically diluted in its zinc analogue.