Insight into the Magnetic Exchange Interactions and Anisotropy in Heterobimetallic Cu^II-Ln^III Complexes: A Rare Example of Cu-Gd Single-Molecule Magnets

abstract

The exploration of heterometallic complexes containing both 3d and 4f metal ions has been on the rise with advancements in the field of 3d-4f single-molecule magnets. The motivation stemmed from early investigations into the Cu-II-Ln(III) systems, particularly the Cu-II/Gd-III one, that revealed a ferromagnetic interaction between these ions, irrespective of the complex's topology or nuclearity. In this context, we have synthesized three new isostructural and isomorphous [CuLn(L)(NO3)(3)(H2O)] complexes (Ln = Gd (1), Tb (2), and Dy (3)) derived from a compartmental Schiff base ligand H2L. All three complexes were structurally characterized in which Cu-II and Ln(III) ions occupy inner N2O2 and outer O2O '(2) compartments of the doubly deprotonated Schiff base ligand, respectively. Moreover, another closely related complex [Cu(L)](2)[CuDy(L)(OAc)(NO3)(H2O)](NO3)5H(2)O (4) has been synthesized starting from the same Schiff base ligand H2L to examine the effect of the coordination environment around the Dy-III ion on the dynamic magnetic behavior in these systems. Variable-temperature direct-current magnetic susceptibility measurements suggest a ferromagnetic exchange interaction between Cu-II and Ln(III) ions, especially in 1-3, which is further supported by DFT calculations. However, alternating-current magnetic susceptibility measurements resulted in the most interesting part of this report. Remarkably, despite the isotropic nature of the Gd-III ion, compound 1 displayed slow relaxation of the magnetization in the presence of an applied field together with its anisotropic counterparts Tb-III (2) and Dy-III (3). Based on the literature study, this is a rare system in which Cu-II-Gd-III complexes showed single-molecule magnet behavior. Moreover, theoretical calculations were also performed by means of DFT and CASSCF levels of theory to obtain precise information on the magnetic exchange coupling between Cu-II and Ln(III) ions together with the distinct magnetic dynamics in these systems.

keywords

BASIS-SETS; LANTHANIDE COMPLEXES; SLOW RELAXATION; GROUND-STATE; ION; LN; TB; THERMOCHEMISTRY; BLOCKING; ORIGIN

subject category

Chemistry; Crystallography; Materials Science

authors

Jana, NC; Jaglicic, Z; Herchel, R; Brandao, P; Nandy, R; Panja, A

Groups

G1 - Porous Materials and Nanosystems

Projects

CICECO - Aveiro Institute of Materials (UIDB/50011/2020)

CICECO - Aveiro Institute of Materials (UIDP/50011/2020)

Associated Laboratory CICECO-Aveiro Institute of Materials (LA/P/0006/2020)

acknowledgements

A.P. gratefully acknowledges financial support of this work by the CSIR, New Delhi, India (sanction no. 01/3118/23/EMR-II dated 08/07/23). R. H. acknowledges the financial support from the institutional sources of the Department of Inorganic Chemistry, Palacky University Olomouc, Czech Republic. Z.J. acknowledges financial support of the Slovenian Research Agency (grant no. P2-0348). P.B. gratefully acknowledges financial support of this work by the project CICECO-Aveiro Institute of Materials, UIDB/50011/2020, UIDP/50011/2020 and LA/P/0006/2020, financed by national funds through the FCT/MCTES (PIDDAC).