The Nature of the Bridging Anion Controls the Single-Molecule Magnetic Properties of DyX₄M 12-Metallacrown-4 Complexes

Abstract

A family of DyXM(12-MC-4) compounds were synthesized and magnetically characterized (X = salicylate, acetate, benzoate, trimethylacetate, M = Na or K). The bridging ligands were systematically varied while keeping the remainder of the MC-geometry constant. The type of monovalent cation, necessary for charge balance, was also altered. The dc magnetization and susceptibility of all compounds were similar across the series. Regardless of the identity of the countercation, the Dy(Hsal)M 12-MC-4 compounds were the only compounds to show frequency-dependent ac magnetic susceptibility, a hallmark of single-molecule magnetism. This indicates that the nature of the bridging ligand in the 12-MC-4 compounds strongly affects the out-of-phase magnetic properties. The SMM behavior appears to correlate with the pK of the bridging ligand.

Synthesis, Structural, and Magnetic Characterization of a Mixed 3d/4f 12-Metallacrown-4 Family of Complexes

“…If we further restrict the above requirements, by exclusively using Mn III as the periphery ring metal ion, only a very few papers have been published featuring the above qualifications. Pecoraro and Zaleski reported a complex with the general formula being Ln III 4 ·6DMF where M I = Na I and K I , and Ln = various lanthanides [26][27][28]. This family of compounds has been extensively structurally studied but the authors did focus their investigations mainly towards the effect that the Na I or K I ions had on magnetic measurements and not on the pure {Mn 4 III Ln III (µ-NO)4} 11+ magnetic core, without emphasizing on the evaluation of exchange interactions by fitting of the data.…”

Crystal structures of two heterotrimetallic dysprosium–manganese–sodium 12-metallacrown-4 complexes with the bridging ligands 3-hydroxybenzoate and 4-hydroxybenzoate

“…The selfassembly synthetic strategy of MCs lends itself to the ability to place metal ions in specific positions in the molecules and the controllable formation of specific molecules. While heterobimetallic MCs have been known since the 1990s, heterotrimetallic MCs have only been recently reported (Azar et al, 2014;Travis et al, 2015Travis et al, , 2016Cao et al, 2016;Boron et al, 2016;Lutter et al, 2020). These structures are based on a 12-MC-4 framework with manganese(III) or gallium(III) as the ring metal, a central lanthanide ion, and typically an alkali metal ion bound opposite to the lanthanide ion -though in one case a tungsten(V) ion is bound opposite the lanthanide ion.…”

“…Since then we have reported other Ln III Na(X) 4 [12-MC Mn(III)N(shi) -4] complexes, where Ln III is Y III , Er III , and Dy III , and X À is 2-hydroxybenzoate, benzoate, and trimethylacetate, which demonstrate that the bridging carboxylate anion can be easily substituted in these structures (Travis et al, 2015(Travis et al, , 2016Boron et al, 2016). In addition, the identity of the bridging ligand affects the singlemolecule magnet (SMM) properties of a series of [12-MC Mn(III)N(shi) -4] complexes with Dy III as the central lanthanide ion (Boron et al, 2016). Specifically, the pK a value of the parent acid of the bridging ligand, which indicates the Lewis basicity of the anion, directly impacts the SMM behavior of the MCs.…”

“…1 for additional display details. [Symmetry codes: Boron et al, 2016), and Dy(2-OHben) 3.5 (OAc) 0.5 -K[12-MC Mn(III)N(shi) -4](DMF) 1.5 (H 2 O) 3.5 Á5DMF (HADDUO; Boron et al, 2016).…”

Iodinated Metallacrowns: Toward Combined Bimodal Near‐Infrared and X‐Ray Contrast Imaging Agents

“…Metallacrowns (MCs), originally described as an inorganic structurala nalogues to crown ethers [9] have been employedi n aw ide array of research topics [10][11][12][13][14][15][16][17][18][19][20][21] including NIR optical imaging. [22,23] Several familieso fM Cs have demonstrated an outstandinga bility to protecta nd efficiently sensitize the characteristic emissiono fl anthanide(III) ions (Ln 3 + )i nt he visible and in the NIR ranges.…”