Porous Coordination Polymers Based on {Mn₆} Single-Molecule Magnets

In this paper, three isostructural porous coordination polymers, namely, [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L¹)_2/3]·4DMF·2H₂O·2CH₃OH (<b>1</b>), [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L²)_2/3]·4DMF·2H₂O·2CH₃OH (<b>2</b>), and [Mn₆(μ₃-O)₂(sao)₆­(DMF)₄(L³)_2/3]·4DMF·4H₂O·2CH₃OH (<b>3</b>) (DMF = dimethylformamide, H₂sao = salicylaldoxime, H₃L¹ = benzene-1,3,5-trisbenzoic acid, H₃L² = 4,4′,4″-<i>s</i>-triazine-2,4,6-triyltribenzoic acid, and H₃L³ = 2,4,6-tris­(4-carboxyphenoxy)-1,3,5-<i>s</i>-triazine), based on the oximato-bridged {Mn₆} single-molecule magnet (SMM) and tricarboxylic acid ligands, were designed and synthesized. X-ray structural analysis shows that they possess a two-dimensional layered structure, where the {Mn₆} moieties are linked by the corresponding (L^<i>x</i>)^3– carboxylate ligands (<i>x</i> = 1, 2, 3) forming a huge honeycomb layer. These compounds not only show the SMM behavior as confirmed by alternative current susceptibility measurements but also show selectivity for CO₂ over N₂ at 273 K. On the basis of the magnetic fitting to the magnetic susceptibilities and the field dependence of magnetization for complexes <b>1</b>–<b>3</b>, the spin ground states are <i>S</i> = 4. Compared with isolated {Mn₆} SMMs with <i>S</i> = 4, the out-of-phase susceptibilities of <b>1</b>–<b>3</b> show obvious peaks only under the external direct-current field of 2 kOe. However, no peaks in χ_m″ are observed in the partially desolvated sample of compound <b>1</b>

Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Field-Induced Single-Ion Magnets Based on Enantiopure Chiral β‑Diketonate Ligands

A pair of homochiral β-diketonate ligands (+)-3-trifluoroacetyl)­camphor (<i>d</i>-Htfc) and (−)-3-trifluoroacetyl)­camphor (<i>l</i>-Htfc) were used to construct two enantiomeric pairs of Dy­(III) single-ion magnets [Dy­(<i>d</i>-tfc)₃(bpy)]₂ (<i>d</i>-<b>1</b>)/[Dy­(<i>l</i>-tfc)₃(bpy)]₂ (<i>l</i>-<b>1</b>) (bpy = 2,2′-bipyridine) and [Dy­(<i>d</i>-tfc)₃(phen)]·2H₂O (<i>d</i>-<b>2</b>)/[Dy­(<i>l</i>-tfc)₃(phen)] (<i>l</i>-<b>2</b>) (phen = 1,10-phenanthroline). The capping aromatic <i>N</i>,<i>N</i>′-donors have a dramatic influence on the structural and magnetic characteristics of the Dy­(III) β-diketonate enantiomeric pairs: the cocrystal of two homochiral Dy­(III) β-diketonate stereoisomers with the 2,2′-bipyridine ligand was formed, showing field-induced single-ion magnet behaviors with a two-step relaxation process, while no stereoisomerization happened for the homochiral Dy­(III) β-diketonate with the 1,10-phenanthroline coligand, exhibiting a single relaxation process of the magnetization only. The anisotropy barriers of <i>d</i>-<b>1</b> (36.5 and 46.1 K) are slightly smaller than those of <i>l</i>-<b>1</b> (37.0 and 49.3 K), while <i>d</i>-<b>2</b> has a larger energy barrier (30.5 K) with respect to <i>l</i>-<b>2</b> (25.1 K)

Field-Induced Relaxation of Magnetization in a Three-Dimensional LnMOF with the Second Bridging Ligand Squarate

A three-dimensional (3D) dysprosium­(III) metal-organic framework with nicotinate <i>N</i>-oxide (NNO^–) and squarate (C₄O₄^2–) mixed bridging ligands, [Dy­(NNO)­(C₄O₄)­(H₂O)]<i>_n</i> (<b>1</b>), has been hydrothermally synthesized. The dysprosium­(III) ions are linked to each other by the squarate anions to form a unique dysprosium­(III) squarate double-layered network; the NNO^– anions then bridge such layers to complete the 3D framework. Complex <b>1</b> exhibits a two-step relaxation of magnetization under a dc field of 1000 Oe, with effective energy barrier values of 8.5 and 14.3 K, respectively

Syntheses, Crystal Structures, and Magnetic Properties of Two <i>p</i>-<i>tert</i>-Butylsulfonylcalix[4]arene Supported Cluster Complexes with a Totally Disordered Ln₄(OH)₄ Cubane Core

Two new sandwich calix[4]­arene-supported cluster complexes, [Ln₄(OH)₄­(TBSOC)₂­(H₂O)₄­(CH₃OH)₄]­·4H₂O (H₄TBSOC = <i>p</i>-<i>tert</i>-butylsulfonylcalix­[4]­arene; Ln = Dy, <b>1</b>; Ln = Ho, <b>2</b>), have been prepared and characterized. An X-ray crystallographic study reveals that both complexes contain a holistically disordered [Ln₄(OH)₄]⁸⁺ cubane cluster core, which is sandwiched between two antiparallel calixarene macrocycles. Magnetic investigations indicate that complex <b>1</b> displays slow magnetization relaxation typical for single-molecule magnets in the absence of a static applied dc field, with the Δ<i><i>E</i>/k</i>_B parameter of 22.9 K, the largest value for the calixarene-supported pure 4f single-molecule magnets so far, whereas complex <b>2</b> does not show any relaxation of the magnetization above 2 K

Syntheses, Crystal Structures, and Magnetic Properties of Two <i>p</i>-<i>tert</i>-Butylsulfonylcalix[4]arene Supported Cluster Complexes with a Totally Disordered Ln₄(OH)₄ Cubane Core

Two new sandwich calix[4]­arene-supported cluster complexes, [Ln₄(OH)₄­(TBSOC)₂­(H₂O)₄­(CH₃OH)₄]­·4H₂O (H₄TBSOC = <i>p</i>-<i>tert</i>-butylsulfonylcalix­[4]­arene; Ln = Dy, <b>1</b>; Ln = Ho, <b>2</b>), have been prepared and characterized. An X-ray crystallographic study reveals that both complexes contain a holistically disordered [Ln₄(OH)₄]⁸⁺ cubane cluster core, which is sandwiched between two antiparallel calixarene macrocycles. Magnetic investigations indicate that complex <b>1</b> displays slow magnetization relaxation typical for single-molecule magnets in the absence of a static applied dc field, with the Δ<i><i>E</i>/k</i>_B parameter of 22.9 K, the largest value for the calixarene-supported pure 4f single-molecule magnets so far, whereas complex <b>2</b> does not show any relaxation of the magnetization above 2 K

Arraying Octahedral {Cr₂Dy₄} Units into 3D Single-Molecule-Magnet-Like Inorganic Compounds with Sulfate Bridges

Two novel 3D pure inorganic compounds based on [Cr₂Dy₄(μ₄-O)₂(μ₃-OH)₄]¹⁰⁺ cluster units and sulfate anions are presented. Both complexes exhibit single-molecule-magnet (SMM)-like behavior. Permutation of the magnetic moment direction among SMM-like cluster units has a significant effect on the performance of molecular nanomagnets, and directional consistency shows obvious advantages

Field-Induced Slow Magnetic Relaxation and Gas Adsorption Properties of a Bifunctional Cobalt(II) Compound

A new compound, {[Co­(bmzbc)₂]·2DMF}_<i>n</i> (<b>JXNU-1</b>, <b>JXNU</b> denotes Jiangxi Normal University), based on the 4-(benzimidazole-1-yl)­benzoate (bmzbc^–) ligand has been synthesized and structurally characterized. The Co­(II) ions are bridged by the rod-like bmzbc^– ligands to give a two-dimensional (2D) sheet wherein the Co­(II) ions are spatially separated from each other by the long bmzbc^– rods. The 2D sheets are further stacked into a 3D framework with 1D channels occluding the guest DMF molecules. Detailed magnetic studies show that the individual octahedral Co­(II) ions in <b>JXNU-1</b> exhibit field-induced slow magnetic relaxation, which is characteristic behavior of single-ion magnets (SIMs). The rarely observed positive value of zero-field splitting (ZFS) parameter <i>D</i> for the Co­(II) ion in <b>JXNU-1</b> demonstrates that <b>JXNU-1</b> is a unique example of Co­(II)-based SIMs with easy-plane anisotropy, which is also confirmed by the calculations. The microporous nature of <b>JXNU-1</b> was established by measuring CO₂ sorption isotherms. The abrupt changes observed in the C₃H₈ and C₂H₆ adsorption isotherms indicate that a structural transformation occurred in the gas-loading process. The long connection between the magnetic metal centers in <b>JXNU-1</b> meets the requirements for construction of porosity and SIM in a well-defined network, harmoniously providing a good candidate of functional molecular materials exhibiting SIM and porosity

Rhodamine Salicylaldehyde Hydrazone Dy(III) Complexes: Fluorescence and Magnetism

Three new dysprosium­(III) complexes [Dy₂(HL¹-o)₂(L¹)­(NO₃)₃]­[Dy­(NO₃)₅]·1.5ACE·0.5Et₂O (<b>1</b>), [Dy­(L¹)₃]·2.5MeOH·MeCN (<b>2</b>), and [Dy­(L²)₃]·MeOH·MeCN (<b>3</b>) (HL¹ = rhodamine B salicylaldehyde hydrazine, HL² = rhodamine B 3-methylsalicylaldehyde hydrazine) were synthesized and characterized. Purple complex <b>1</b> contains two ring-open ligands HL¹-o and shows fluorescence of the rhodamine amide moiety, whereas yellow complexes <b>2</b> and <b>3</b> are comprised of ring-close ligands (L^1/2)⁻ and display fluorescence of the salicylaldehyde Schiff base part. For <b>2</b> and <b>3</b>, Dy­(III) ions are nine coordinated by the six oxygen and three nitrogen atoms of three chelate (L^1/2)⁻ ligands, but the arrangements of the three ligands are different owing to the methyl substituent on HL². There are three short predominant Dy–O_phenoxy bonds in <b>2</b> and <b>3</b>. The largest O_phenoxy–Dy–O_phenoxy angle is 148.64(17)° for <b>2</b> and 89.63(13)° for <b>3</b>. Magnetic studies reveal that complex <b>2</b> is a field-induced single-molecule magnet (<i>U</i>_eff = 104.2 K under a dc magnetic field of 2000 Oe), and <b>3</b> exhibits only a magnetic relaxation behavior owing to the quantum tunneling of magnetization (QTM). Furthermore, ab initio calculations illustrate that the disposition of predominant Dy–O_phenoxy bonds affects the magnetic anisotropy of the Dy­(III) ions and relaxation processes of complexes <b>2</b> and <b>3</b>