Tuning the Condensation Degree of {Fe^III_<i>n</i>} Oxo Clusters via Ligand Metathesis, Temperature, and Solvents

Trinuclear μ₃-oxo-centered iron­(III) isobutyrate clusters readily react with polyalcohol organic ligands under one-pot synthesis conditions. Depending on the ligand, solvent, and temperature, a range of hexa-, dodeca-, and doicosanuclear iron­(III) oxo-hydroxo condensation products, isolated as (mdeaH₃)₂[Fe₆O­(thme)₄Cl₆]·0.5­(MeCN)·0.5­(H₂O) (<b>1</b>), [Fe₁₂O₄(OH)₂(teda)₄(N₃)₄(MeO)₄]­N₃(NO₃)_0.5(MeO)_0.5·2.5­(H₂O) (<b>2</b>), [Fe₁₂O₆(teda)₄Cl₈]·6­(CHCl₃) (<b>3</b>), [Fe₂₂O₁₆(OH)₂(O₂CCHMe₂)₁₈(bdea)₆(EtO)₂(H₂O)₂]·2­(EtOH)·5­(MeCN)·6­(H₂O) (<b>4</b>), and [Fe₂₂O₁₄(OH)₄(O₂CCHMe₂)₁₈(mdea)₆(EtO)₂(H₂O)₂]­(NO₃)₂·EtOH·H₂O (<b>5</b>), where tedaH₄ = <i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetrakis­(2-hydroxyethyl)­ethylenediamine; thmeH₃ = 1,1,1-tris­(hydroxymethyl)­ethane; mdeaH₂ = <i>N</i>-methyldiethanolamine; and bdeaH₂ = <i>N</i>-butyldiethanolamine. Complete carboxylate metathesis in the {Fe₃} precursor complexes by thme^3– or teda^4– and the agglomeration of the formed species under solvothermal conditions afforded carboxylate-free {Fe₆} product (<b>1</b>) in MeCN/CH₂Cl₂ or {Fe₁₂} complexes (<b>2</b> and <b>3</b>) in MeOH/EtOH and CHCl₃/thf, respectively (thf = tetrahydrofuran). Single-crystal X-ray diffraction analyses revealed that <b>1</b> contains a [Fe₆O­(thme)₄Cl₆]^2– cluster anion with a Lindqvist-type {Fe₆(μ₆-O)} core motif, charge-compensated by two protonated mdeaH₃⁺ cations. <b>2</b> comprises a [Fe₁₂O₄(OH)₂(teda)₄­(N₃)₄(MeO)₄]²⁺ cation with a {Fe₁₂O₄(OH)₂}²⁶⁺ core, whereas <b>3</b> contains a charge-neutral [Fe₁₂O₆(teda)₄(Cl)₈] complex with an {Fe₁₂O₆}²⁴⁺ core. Finally, employing flexible bdeaH₂ or mdeaH₂ ligands under soft reaction conditions afforded giant {Fe₂₂} oxo-hydroxo complexes (<b>4</b> and <b>5</b>) with a central {Fe₆} layer sandwiched between two outer {Fe₈} groups. Magnetic studies of <b>1</b>–<b>5</b> revealed strong antiferromagnetic coupling between the Fe^III spin centers in all clusters

Ultralarge 3d/4f Coordination Wheels: From Carboxylate/Amino Alcohol-Supported {Fe₄Ln₂} to {Fe₁₈Ln₆} Rings

A family of wheel-shaped charge-neutral heterometallic {Fe^III₄Ln^III₂}- and {Fe^III₁₈M^III₆}-type coordination clusters demonstrates the intricate interplay of solvent effects and structure-directing roles of semiflexible bridging ligands. The {Fe₄Ln₂}-type compounds [Fe₄Ln₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄]·2­(EtOH), Ln = Dy (<b>1a</b>), Er (<b>1b</b>), Ho (<b>1c</b>); [Fe₄Tb₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄] (<b>1d</b>); [Fe₄Ln₂(O₂CCMe₃)₆­(N₃)₄(Htea)₄]·2­(CH₂Cl₂), Ln = Dy (<b>2a</b>), Er (<b>2b</b>); [Fe₄Ln₂(O₂CCMe₃)₄­(N₃)₆(Htea)₄]·2­(EtOH)·2­(CH₂Cl₂), Ln = Dy (<b>3a</b>), Er (<b>3b</b>) and the {Fe₁₈M₆}-type compounds [Fe₁₈M₆(O₂CCHMe₂)₁₂­(Htea)₁₈(tea)₆(N₃)₆]·<i>n</i>(solvent), M = Dy (<b>4</b>, <b>4a</b>), Gd (<b>5</b>), Tb (<b>6</b>), Ho (<b>7</b>), Sm (<b>8</b>), Eu (<b>9</b>), and Y (<b>10</b>) form in ca. 20–40% yields in direct reaction of trinuclear Fe^III pivalate or isobutyrate clusters, lanthanide/yttrium nitrates, and bridging triethanolamine (H₃tea) and azide ligands in different solvents: EtOH for the smaller {Fe₄Ln₂} wheels and MeOH/MeCN or MeOH/EtOH for the larger {Fe₁₈M₆} wheels. Single-crystal X-ray diffraction analyses revealed that <b>1</b>–<b>3</b> consist of planar centrosymmetric hexanuclear clusters built from Fe^III and Ln^III ions linked by an array of bridging carboxylate, azide, and aminopolyalcoholato-based ligands into a cyclic structure with a cavity, and with distinct sets of crystal solvents (2 EtOH per formula unit in <b>1a</b>–<b>c</b>, 2 CH₂Cl₂ in <b>2</b>, and 2 EtOH and 2 CH₂Cl₂ in <b>3</b>). In <b>4</b>–<b>10</b>, the largest 3d/4f wheels currently known, nearly linear Fe₃ fragments are joined via mononuclear Ln/Y units by a set of isobutyrates and amino alcohol ligands into virtually planar rings. The magnetic properties of <b>1</b>–<b>10</b> reveal slow magnetization relaxation for {Fe₄Tb₂} (<b>1d</b>) and slow relaxation for {Fe₄Ho₂} (<b>1c</b>), {Fe₁₈Dy₆} (<b>4</b>), and {Fe₁₈Tb₆} (<b>6</b>)

A {Co^III₂Dy^III₄} Single-Molecule Magnet with an Expanded Core Structure

The coordination cluster compound [CoIII2DyIII4(OH)2­(ib)8(bdea)2(NO3)4­(H2O)2]·2MeCN (1) self-assembles in a high-yield reaction of cobalt(II) isobutyrate (ib) with Dy(NO3)3·6H2O and N-butyldiethanolamine (H2bdea) in air. The Ci-symmetric {CoIII2DyIII4} core fragment features two {CoDy2(μ3-OH)} triangles, joined by one of their Dy sites via μ-O and μ-carboxylate bridges. This results in a flat zigzag metal skeleton, in contrast to previously reported hexanuclear {Co2Ln4(μ3-OH)2} clusters, namely, exhibiting a more condensed combination of two {CoLn2(μ3-OH)} triangles that form a Dy4 rhombus. According to ac susceptibility measurements, this rearrangement in 1 reduces quantum tunneling of the magnetization and hence pushes up the onset of pronounced out-of-phase signals at zero bias field to 14 K, a significant change vs the more condensed {Co2Dy4} structures. As intermolecular interactions between coordination clusters in the solid state are well-known to also influence SMM features, comparative Hirshfeld surface analyses are also presented

Assembly of Cerium(III) 2,2′-Bipyridine-5,5′-dicarboxylate-based Metal–Organic Frameworks by Solvent Tuning

Small changes to the reaction conditions differentiate between two metal–organic frameworks (MOFs), {[Ce₂(H₂O)­(bpdc)₃(dmf)₂]·2­(dmf)}_<i>n</i> (<b>1</b>) and {[Ce₄(H₂O)₅(bpdc)₆(dmf)]·<i>x</i>(dmf)}_<i>n</i> (<b>2</b>), that were solvothermally synthesized from cerium­(III) nitrate hexahydrate and 2,2′-bipyridine-5,5′-dicarboxylic acid (H₂bpdc) in dimethylformamide (dmf). The two compounds illustrate how the flexibility of the coordination geometry of Ce^III translates into MOFs, the formation of which readily adapts to different solvent environments

Avoiding Magnetochemical Overparametrization, Exemplified by One-Dimensional Chains of Hexanuclear Iron(III) Pivalate Clusters

One-dimensional chain coordination polymers based on hexanuclear iron­(III) pivalate building blocks and 1,4-dioxane (diox) or 4,4′-bipyridine (4,4′-bpy) bridging ligands, [Fe₆O₂(O₂CH₂)­(O₂CCMe₃)₁₂(diox)]_<i>n</i> (<b>1</b>) and [Fe₆O₂(O₂CH₂)­(O₂CCMe₃)₁₂(4,4′-bpy)]_<i>n</i> (<b>2</b>), showcase the utility of the angular overlap model, implemented in the program <i>wxJFinder</i>, in the predictive identification of the relative role of intra- and intercluster coupling

Linear, Zigzag, and Helical Cerium(III) Coordination Polymers

Five novel one-dimensional cerium­(III) carboxylate coordination polymers, [Ce­(O₂CCH₂CHMe₂)₃(EtOH)₂]_<i>n</i> (<b>1</b>), {[Ce­(O₂CCH₂Me)₃(H₂O)]·0.5­(4,4′-bpy)}_<i>n</i> (<b>2</b>; 4,4′-bpy = 4,4′-bipyridine), {[Ce₂(O₂CCHMe₂)₆(H₂O)₃]}_<i>n</i> (<b>3</b>), {[Ce₃(O₂CCHMe₂)₉(<i>n</i>PrOH)₄]}_<i>n</i> (<b>4</b>), and {[Ce₃(O₂CCHMe₂)₉(HO₂CCHMe₂)₂(H₂O)₂]·2Me₂CHCO₂H}_<i>n</i> (<b>5</b>), showcase the surprisingly consistent tendency of Ce­(III) coordination network structures to adopt one-dimensional connection modes. The type of carboxylate as well as the reaction solvents determines the exact bridging versus end-on coordination modes for the carboxylates and, in turn, discriminate between linear, zigzag, and helical arrangements. Detailed magnetochemical analyses reveal pronounced single-ion effects and the expected weak antiferromagnetic coupling

Linear, Zigzag, and Helical Cerium(III) Coordination Polymers

Five novel one-dimensional cerium­(III) carboxylate coordination polymers, [Ce­(O₂CCH₂CHMe₂)₃(EtOH)₂]_<i>n</i> (<b>1</b>), {[Ce­(O₂CCH₂Me)₃(H₂O)]·0.5­(4,4′-bpy)}_<i>n</i> (<b>2</b>; 4,4′-bpy = 4,4′-bipyridine), {[Ce₂(O₂CCHMe₂)₆(H₂O)₃]}_<i>n</i> (<b>3</b>), {[Ce₃(O₂CCHMe₂)₉(<i>n</i>PrOH)₄]}_<i>n</i> (<b>4</b>), and {[Ce₃(O₂CCHMe₂)₉(HO₂CCHMe₂)₂(H₂O)₂]·2Me₂CHCO₂H}_<i>n</i> (<b>5</b>), showcase the surprisingly consistent tendency of Ce­(III) coordination network structures to adopt one-dimensional connection modes. The type of carboxylate as well as the reaction solvents determines the exact bridging versus end-on coordination modes for the carboxylates and, in turn, discriminate between linear, zigzag, and helical arrangements. Detailed magnetochemical analyses reveal pronounced single-ion effects and the expected weak antiferromagnetic coupling

Linear, Zigzag, and Helical Cerium(III) Coordination Polymers

Five novel one-dimensional cerium­(III) carboxylate coordination polymers, [Ce­(O₂CCH₂CHMe₂)₃(EtOH)₂]_<i>n</i> (<b>1</b>), {[Ce­(O₂CCH₂Me)₃(H₂O)]·0.5­(4,4′-bpy)}_<i>n</i> (<b>2</b>; 4,4′-bpy = 4,4′-bipyridine), {[Ce₂(O₂CCHMe₂)₆(H₂O)₃]}_<i>n</i> (<b>3</b>), {[Ce₃(O₂CCHMe₂)₉(<i>n</i>PrOH)₄]}_<i>n</i> (<b>4</b>), and {[Ce₃(O₂CCHMe₂)₉(HO₂CCHMe₂)₂(H₂O)₂]·2Me₂CHCO₂H}_<i>n</i> (<b>5</b>), showcase the surprisingly consistent tendency of Ce­(III) coordination network structures to adopt one-dimensional connection modes. The type of carboxylate as well as the reaction solvents determines the exact bridging versus end-on coordination modes for the carboxylates and, in turn, discriminate between linear, zigzag, and helical arrangements. Detailed magnetochemical analyses reveal pronounced single-ion effects and the expected weak antiferromagnetic coupling

Linear, Zigzag, and Helical Cerium(III) Coordination Polymers

Five novel one-dimensional cerium­(III) carboxylate coordination polymers, [Ce­(O₂CCH₂CHMe₂)₃(EtOH)₂]_<i>n</i> (<b>1</b>), {[Ce­(O₂CCH₂Me)₃(H₂O)]·0.5­(4,4′-bpy)}_<i>n</i> (<b>2</b>; 4,4′-bpy = 4,4′-bipyridine), {[Ce₂(O₂CCHMe₂)₆(H₂O)₃]}_<i>n</i> (<b>3</b>), {[Ce₃(O₂CCHMe₂)₉(<i>n</i>PrOH)₄]}_<i>n</i> (<b>4</b>), and {[Ce₃(O₂CCHMe₂)₉(HO₂CCHMe₂)₂(H₂O)₂]·2Me₂CHCO₂H}_<i>n</i> (<b>5</b>), showcase the surprisingly consistent tendency of Ce­(III) coordination network structures to adopt one-dimensional connection modes. The type of carboxylate as well as the reaction solvents determines the exact bridging versus end-on coordination modes for the carboxylates and, in turn, discriminate between linear, zigzag, and helical arrangements. Detailed magnetochemical analyses reveal pronounced single-ion effects and the expected weak antiferromagnetic coupling

Linear, Zigzag, and Helical Cerium(III) Coordination Polymers

Five novel one-dimensional cerium­(III) carboxylate coordination polymers, [Ce­(O₂CCH₂CHMe₂)₃(EtOH)₂]_<i>n</i> (<b>1</b>), {[Ce­(O₂CCH₂Me)₃(H₂O)]·0.5­(4,4′-bpy)}_<i>n</i> (<b>2</b>; 4,4′-bpy = 4,4′-bipyridine), {[Ce₂(O₂CCHMe₂)₆(H₂O)₃]}_<i>n</i> (<b>3</b>), {[Ce₃(O₂CCHMe₂)₉(<i>n</i>PrOH)₄]}_<i>n</i> (<b>4</b>), and {[Ce₃(O₂CCHMe₂)₉(HO₂CCHMe₂)₂(H₂O)₂]·2Me₂CHCO₂H}_<i>n</i> (<b>5</b>), showcase the surprisingly consistent tendency of Ce­(III) coordination network structures to adopt one-dimensional connection modes. The type of carboxylate as well as the reaction solvents determines the exact bridging versus end-on coordination modes for the carboxylates and, in turn, discriminate between linear, zigzag, and helical arrangements. Detailed magnetochemical analyses reveal pronounced single-ion effects and the expected weak antiferromagnetic coupling