Experimental and theoretical investigations of four 3d–4f butterfly single-molecule magnets

Abstract

The syntheses, structures, and characterization of four 3d-4f butterfly clusters are described. With different polyhydroxy Schiff-base ligands 2-(((2-hydroxy-3-methoxyphenyl)methylene)amino)-2-(hydroxymethyl)-1,3-propanediol (H4L1) and 2-(2,3-dihydroxpropyliminomethyl)-6-methoxyphenol (H3L2), three heterotetranuclear NiLn complexes (NiDy-L1 (1), NiTb-L2 (2), NiDy-L2 (3)) and one heterohexanuclear CoDy complex (4) were obtained. The three heterotetranuclear NiLn complexes display a central planar butterfly topology. The heterohexanuclear complex was built from butterfly CoDy clusters and two Dy(III) ions by the bridging of pivalate. The vertices of the body positions of the butterfly are occupied by transition metal ions in all four complexes. Magnetic analyses indicate that the complexes exhibit typical single-molecule magnet behaviour with anisotropy barriers of 33.7 cm(-1), 60.3 cm(-1), 39.6 cm(-1), and 18.4 cm(-1) for 1-4, respectively. Ab initio calculations were performed on these complexes, and the low lying electronic structure of each Ln(III) (Ln = Dy, Tb) ion and the magnetic interactions were determined. It was found that the two Ln ions may have much more contribution to the total relaxation barrier through the stronger 3d-4f exchange couplings compared to weak Ln-Ln interactions.

Selective arc-discharge synthesis of Dy2S-clusterfullerenes and their isomer-dependent single molecule magnetism

“…At the lowest accessible temperatures (1.6–5 K), all three Dy-EMFs exhibit a linear regime with a relatively small barrier, U1eff, presumably corresponding to the energy difference between the states with ferromagnetically and antiferromagnetically coupled Dy ions (it has contributions from both dipolar and exchange interactions, see more detailed discussion below). Magnetization relaxation pathways proceeding through excited “exchange states” are well documented for 3d–4f complexes, albeit usually with much shorter τ 0 values than those observed in EMFs 20,21,23,68–71. In Dy 2 S@C 82 - C 3v , the U1eff barrier amounts to 6.5 K versus 15.2 K in Dy 2 S@C 82 - C s and 17.4 K in Dy 2 C 2 @C 82 - C s .…”

“…One of the ways to improve the situation is to increase the local symmetry of the crystal field acting on the lanthanide ion, and some of the best single-ion Dy-SMM have been obtained following this strategy 10,13–15. Another approach is to combine two or more lanthanide ions in one molecule,5,16–19 or combine lanthanides with transition metals in 3d–4f complexes 20–25. Exchange and dipolar coupling in polynuclear complexes create a manifold of additional states and an additional barrier to relaxation, thus preventing QTM.…”

Slow Magnetic Relaxation in a Co2Dy Trimer and a Co2Dy2 Tetramer

“…Adjacent to the phenolate O atom on one side there is a 1,2‐propanediolamine group and on the other side a methoxy group. This ligand has also been used by other groups to design promising homo and heterometallic 3d, 4f, 1s–3d and 1s–2p–3d complexes [27–33] . The coordination modes adopted by the ligand in complexes 1 and 2 are depicted in Figure S3 in the Supporting Information.…”

Zwitterionic 4-bromo-6-methoxy-2-{[tris(hydroxymethyl)methyl]iminiumylmethyl}phenolate: crystal structure and Hirshfeld surface analysis

“…More recently, the adipogenic (cell differentiation) capacity of vanadium (Halevas et al, 2015) and zinc complexes has been described (Tsave et al, 2015). Over and above these considerations, magnetochemistry motivates on-going investigations, especially single-molecule (Wu et al, 2007;Chandrasekhar et al, 2013;Dey et al, 2015) and lanthanide-containing species (Zou et al, 2015;Das et al, 2015). It was during on-going biological assays (Lee et al, 2015) that the title compound, (I), became available.…”