Issue 39, 2019

Dinuclear CoIIYIIIvs. tetranuclear Co II2Y III2 complexes: the effect of increasing molecular size on magnetic anisotropy and relaxation dynamics

Abstract

A new CoII2YIII2 complex with the formula [{Co(μ-L)Y(NO3)}2(μ-CO3)2]·2CH3OH·2H2O (where H2L = N,N′,N′′-trimethyl-N,N′′-bis(2-hydroxy-3-methoxy-5-methylbenzyl)diethylenetriamine) has been prepared and its structure solved by single-crystal X-ray diffraction. The tetranuclear structure is formed by the connection of two [Co(μ-L)Y(NO3)] dinuclear units through two carbonate bridging ligands, which exhibit a μ32-O,O′:κ-O:κ-O′′ tetradentate coordination mode. The CoII ion exhibits a slightly distorted octahedral CoN3O3 coordination environment. From direct-current magnetic data a large and positive axial anisotropy parameter was extracted (D = +80.6 cm−1) and its sign unambiguously confirmed by HFEPR spectra and ab initio calculations. The extracted D value is rather larger than those previously reported for the analogous CoIIYIII dinuclear complexes, which agrees with the fact that the CoII ion in the CoII2YIII2 complex exhibits a lower distortion from the octahedral geometry in this family of CoIInYIIIn complexes. Dynamic ac magnetic measurements show that the reported compound presents field-induced slow relaxation for magnetization reversal, through a combination of direct and Raman processes. Magnetic measurements on the diluted magnetic counterpart (Zn/Co = 10/1) show the persistence of these processes, pointing out their single-ion origin. The Raman relaxation process for the CoII2YIII2 complex is faster that those observed for its CoIIYIII dinuclear counterparts. This fact and the existence of the persistent direct process at low temperature could be attributed to the former molecule being larger and more flexible than the latter ones.

Graphical abstract: Dinuclear CoIIYIIIvs. tetranuclear CoII2YIII2 complexes: the effect of increasing molecular size on magnetic anisotropy and relaxation dynamics

Supplementary files

Article information

Article type
Paper
Submitted
19 Jul 2019
Accepted
04 Sep 2019
First published
09 Sep 2019

Dalton Trans., 2019,48, 14873-14884

Author version available

Dinuclear CoIIYIIIvs. tetranuclear CoII2YIII2 complexes: the effect of increasing molecular size on magnetic anisotropy and relaxation dynamics

A. Masegosa, M. A. Palacios, E. Ruiz, S. Gómez-Coca, J. Krzystek, J. M. Moreno and E. Colacio, Dalton Trans., 2019, 48, 14873 DOI: 10.1039/C9DT02969A

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