Dinuclear CoIIYIII vs Tetranuclear Co2IIY2III complexes: The effect of increasing molecular size on magnetic anisotropy and relaxation dynamics Masegosa, Alberto Palacios López, María de los Ángeles Ruiz, Eliseo Gómez-Coca, Silvia Krzystek, J. Moreno Sánchez, José María Colacio Rodríguez, Enrique The authors acknowledge financial support from Ministerio de Economía y Competitividad (MINECO) for Project CTQ2014-56312-P. The authors also acknowledge a Maria de Maeztu grant (MDM-2017-0767) and thank Ministerio de Educación, Cultura y Deporte for projects PGC2018-093863-B-C21 and PGC2018-102052-B-C21, the Junta de Andalucía (FQM-195) and the Project of excellence P11-FQM-7756, the University of Granada and the Generalitat de Catalunya (SGR2017-1289). M. A. P. thanks MINECO for a Juan de la Cierva Incorporation contract (IJCI-2014-19485). E. R. thanks the Generalitat de Catalunya for an ICREA Academia fellowship and CSUC for computational resources. S. G.-C. thanks Generalitat de Catalunya for a Beatriu de Pinós Fellowship (2017 BP 00080). The HFEPR studies were supported by the NHMFL, which is funded by the National Science Foundation (Cooperative Agreement DMR 1157490) and the State of Florida. The authors thank Dr. A. Ozarowski (NHMFL) for his EPR software SPIN. A new CoII2YIII2 complex with the formula [{Co(u-L)Y(NO3)}2(u-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 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 = +82.62 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 the 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 Co2Y2 complex is faster that those observed for the CoY dinuclear counterparts. This fact and the existence of the persistent direct process at low temperature could be because the former molecule is larger and flexible than the latter ones. 2024-03-06T07:49:26Z 2024-03-06T07:49:26Z 2019 journal article Published version: Masegosa, Alberto et al. Dinuclear CoIIYIII vs Tetranuclear Co2IIY2III complexes: The effect of increasing molecular size on magnetic anisotropy and relaxation dynamics. Dalton Trans., 2019, 48, 14873. https://doi.org/10.1039/C9DT02969A https://hdl.handle.net/10481/89812 10.1039/C9DT02969A eng http://creativecommons.org/licenses/by-nc-nd/4.0/ open access Attribution-NonCommercial-NoDerivatives 4.0 Internacional Royal Society of Chemistry