TY - JOUR

T1 - Analysis of Magnetic Anisotropy and the Role of Magnetic Dilution in Triggering Single-Molecule Magnet (SMM) Behavior in a Family of CoIIYIII Dinuclear Complexes with Easy-Plane Anisotropy

AU - Palacios, María A.

AU - Nehrkorn, Joscha

AU - Suturina, Elizaveta A.

AU - Ruiz, Eliseo

AU - Gómez-Coca, Silvia

AU - Holldack, Karsten

AU - Schnegg, Alexander

AU - Krzystek, Jurek

AU - Moreno, José M.

AU - Colacio, Enrique

N1 - Publisher Copyright: © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim

PY - 2017/8/25

Y1 - 2017/8/25

N2 - Three new closely related CoIIYIII complexes of general formula [Co(μ-L)(μ-X)Y(NO3)2] (X−=NO3 − 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L). In these complexes, CoII and YIII are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L2−) and one ancillary anion X−. The change of the ancillary bridging group connecting CoII and YIII ions induces small differences in the trigonally distorted CoN3O3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that CoII ions in compounds 1–3 have large and positive D values (≈50 cm−1), which decrease with increasing the distortion of the pseudo-octahedral CoII coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic ZnII (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that “hidden single-ion magnet (SIM)” behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K.

AB - Three new closely related CoIIYIII complexes of general formula [Co(μ-L)(μ-X)Y(NO3)2] (X−=NO3 − 1, benzoate 2, or 9-anthracenecarboxylato 3) have been prepared with the compartmental ligand N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine (H2L). In these complexes, CoII and YIII are triply bridged by two phenoxide groups belonging to the di-deprotonated ligand (L2−) and one ancillary anion X−. The change of the ancillary bridging group connecting CoII and YIII ions induces small differences in the trigonally distorted CoN3O3 coordination sphere with a concomitant tuning of the magnetic anisotropy and intermolecular interactions. Direct current magnetic, high-frequency and -field EPR (HFEPR), frequency domain Fourier transform THz electron paramagnetic resonance (FD-FT THz-EPR) measurements, and ab initio theoretical calculations demonstrate that CoII ions in compounds 1–3 have large and positive D values (≈50 cm−1), which decrease with increasing the distortion of the pseudo-octahedral CoII coordination sphere. Dynamic ac magnetic susceptibility measurements indicate that compound 1 exhibits field-induced single-molecule magnet (SMM) behavior, whereas compounds 2 and 3 only display this behavior when they are magnetically diluted with diamagnetic ZnII (Zn/Co=10:1). In view of this, it is always advisable to use magnetically diluted complexes, in which intermolecular interactions and quantum tunneling of magnetism (QTM) would be at least partly suppressed, so that “hidden single-ion magnet (SIM)” behavior could emerge. Field- and temperature-dependence of the relaxation times indicate the prevalence of the Raman process in all these complexes above approximately 3 K.

KW - ab initio calculations

KW - cobalt

KW - EPR spectroscopy

KW - intermolecular interactions

KW - magnetic properties

KW - INDUCED SLOW RELAXATION

KW - ANO BASIS-SETS

KW - ZERO-FIELD

KW - TRANSITION-METAL-COMPLEXES

KW - STATE PERTURBATION-THEORY

KW - MONONUCLEAR COBALT(II) COMPLEX

KW - ION-MAGNET

KW - ZETA VALENCE QUALITY

KW - ORGANIC FRAMEWORK

KW - POSITIVE ANISOTROPY

UR - http://www.scopus.com/inward/record.url?scp=85026319644&partnerID=8YFLogxK

U2 - 10.1002/chem.201702099

DO - 10.1002/chem.201702099

M3 - Article

C2 - 28605076

AN - SCOPUS:85026319644

VL - 23

SP - 11649

EP - 11661

JO - Chemistry - A European Journal

JF - Chemistry - A European Journal

SN - 0947-6539

IS - 48

ER -