Combined Experimental and Theoretical Investigation of the Origin of Magnetic Anisotropy in Pentagonal Bipyramidal Isothiocyanato Co(II), Ni(II), and Fe(III) Complexes with Quaternary-Ammonium-Functionalized 2,6-Diacetylpyridine Bisacylhydrazone

• Published in: Journal of physical chemistry. C 2019-12, Vol.123 (51), p.31142-31155
• Main Authors: Darmanović, Darinka, Shcherbakov, Igor N, Duboc, Carole, Spasojević, Vojislav, Hanžel, Darko, Anđelković, Katarina, Radanović, Dušanka, Turel, Iztok, Milenković, Milica, Gruden, Maja, Čobeljić, Božidar, Zlatar, Matija
• Format: Article
• Language: English
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.9b08066

Magnetic anisotropy in pentagonal bipyramidal complexes of Co­(II) (1 and 2), Fe­(III) (3 and 4), and Ni­(II) (5) with a 2,2′-[2,6-pyridinediylbis­(ethylidyne-1-hydrazinyl-2-ylidene)]­bis­[N,N,N-trimethyl-2-oxoethanaminium] equatorial ligand and isothiocyanato axial ligands has been investigated by magnetic susceptibility measurements, powder X-band electron paramagnetic resonance (EPR) spectroscopy, Mössbauer spectroscopy, ab initio, and ligand-field density functional theory (LFDFT) calculations. The studied complexes display three distinct types of magnetic anisotropy. Co­(II) complexes (1 and 2) show an easy plane anisotropy with large and positive D values and negligible rhombicity. The Ni­(II) complex (5) has uniaxial magnetic anisotropy with a negative D value. Fe­(III) complexes (3 and 4) have small zero-field splitting (ZFS) parameters. Theoretical modeling is used to rationalize the magnetic anisotropy in these systems and to identify the most important excited states that are responsible for the zero-field splitting. These excitations are a consequence of the electronic structure of the central metal ion in ideal pentagonal bipyramidal coordination.