Effect of Ligand Substitution around the Dy^III on the SMM Properties of Dual-Luminescent Zn–Dy and Zn–Dy–Zn Complexes with Large Anisotropy Energy Barriers: A Combined Theoretical and Experimental Magnetostructural Study

Abstract

The new dinuclear Zn(II)-Dy(III) and trinuclear Zn(II)-Dy(III)-Zn(II) complexes of formula [(LZnBrDy(ovan) (NO3)(H2O)](H2O)·0.5(MeOH) (1) and [(L(1)ZnBr)2Dy(MeOH)2](ClO4) (3) (L and L(1) are the dideprotonated forms of the N,N'-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato and 2-{(E)-[(3-{[(2E,3E)-3-(hydroxyimino)butan-2-ylidene ]amino}-2,2-dimethylpropyl)imino]methyl}-6-methoxyphenol Schiff base compartmental ligands, respectively) have been prepared and magnetostructurally characterized. The X-ray structure of 1 indicates that the Dy(III) ion exhibits a DyO9 coordination sphere, which is made from four O atoms coming from the compartmental ligand (two methoxy terminal groups and two phenoxido bridging groups connecting Zn(II) and Dy(III) ions), other four atoms belonging to the chelating nitrato and ovanillin ligands, and the last one coming to the coordinated water molecule. The structure of 3 shows the central Dy(III) ion surrounded by two L(1)Zn units, so that the Dy(III) and Zn(II) ions are linked by phenoxido/oximato bridging groups. The Dy ion is eight-coordinated by the six O atoms afforded by two L(1) ligands and two O atoms coming from two methanol molecules. Alternating current (AC) dynamic magnetic measurements of 1, 3, and the previously reported dinuclear [LZnClDy(thd)2] (2) complex (where thd = 2,2,6,6-tetramethyl-3,5-heptanedionato ligand) indicate single molecule magnet (SMM) behavior for all these complexes with large thermal energy barriers for the reversal of the magnetization and butterfly-shaped hysteresis loops at 2 K. Ab initio calculations on 1-3 show a pure Ising ground state for all of them, which induces almost completely suppressed quantum tunnelling magnetization (QTM), and thermally assisted quantum tunnelling magnetization (TA-QTM) relaxations via the first excited Kramers doublet, leading to large energy barriers, thus supporting the observation of SMM behavior. The comparison between the experimental and theoretical magnetostructural data for 1-3 has allowed us to draw some conclusions about the influence of ligand substitution around the Dy(III) on the SMM properties. Finally, these SMMs exhibit metal- and ligand-centered dual emissions in the visible region, and, therefore, they can be considered as magnetoluminescent bifunctional molecular materials.

Teaching an old molecule new tricks: evidence and rationalisation of the slow magnetisation dynamics in [DyTp2Acac]

“…33,48 Nevertheless, it is generally assumed that n values between 1 and 6 are acceptable, and most likely stem from deviations from the Debye phonon model. [49][50][51] If we fix n = 3 (closest integer value), we retain a good agreement with the experimental data, and the QTM frequency does only slightly vary (to v QT M = 1971(4) Hz).…”

Antimony-ligated dysprosium single-molecule magnets as catalysts for stibine dehydrocoupling

“…Although relaxation via higher-lying Kramers' doublets is known, 35–37 it remains a relatively uncommon phenomenon, with thermally activated relaxation thought to proceed via the first-excited doublet in most SMMs. 38 In both cases, magnetic dilution does not significantly alter the a.c. susceptibility properties, hence the discrepancy between theory and experiment for 2-Dy cannot arise from intramolecular interactions. Despite the differing ligand environments in 1-Dy and 2-Dy , the properties of the low-lying Kramers doublets in both complexes are remarkably similar, as are the orientations of the ground-state anisotropy axes.…”

Filling Tricompartmental Ligands with GdIII and ZnII Ions: Some Structural and MRI Studies

“…In particular, among common 3d ions used for these latter purposes, the combination of zinc ions with lanthanoids in heteronuclear complexes is especially significant. Thus, it appears to influence the anisotropy barrier [7,8,[10][11][12], in some case by simple changes in the ancillary ligands [10]. Furthermore, its presence can also influence on different luminescent properties [10,11,13,14].…”

“…Furthermore, we have recently presented the structure of [Zn 2 Ho(L)(ald)(HO)(H 2 O)(MeCN)](NO 3 ) 2 •EtOH (Hald = 5-bromo-2-hydroxy-3-methoxy benzaldehyde) with a curious 2D H-bonded network [17]. Concurrently, a particular interest has been devoted to heteronuclear {3d-4f}-coordination complexes [2][3][4][5][6][7][8][9][10][11], this combination can lead to interesting results, since it appears that it could modulate some properties, or even afford other remarkable properties, and hence, new polyfunctional molecules could arise from this combination [10,11].…”