A Dodecanuclear Dysprosium Wheel Assembled by Six Vertex-Sharing Dy₃ Triangles Exhibiting Slow Magnetic Relaxation

Reactions of lanthanide­(III) (Ln^III) perchlorate (Ln = Dy and Ho) and a polydentate Schiff base resulted in the unprecedented assembly of novel Ln₁₂ wheels containing six vertex-sharing Ln₃ triangles. The Dy₁₂ derivative represents the largest lanthanide wheel based on the peculiar Dy₃ triangles showing slow magnetic relaxation

Exploiting Miraculous Atmospheric CO₂ Fixation in the Design of Dysprosium Single-Molecule Magnets

A system of CO₃^2–-bridged polynuclear dysprosium complexes has been complemented with the emergence of a key component, namely, [Dy₆(μ₄-CO₃)₃­(μ₃-OH₂)­(spch)₆­(MeOH)₆­(H₂O)₃]­·4MeOH­·3H₂O (<b>3</b>), and thus four dysprosium­(III) clusters (<b>1</b>–<b>4</b>) spontaneously fixing one, two, three, and four atmospheric CO₂ molecules, respectively, have been successfully assembled. Compound <b>1</b> is a Dy₆ single-molecular magnet (SMM) (<b>1</b>) based on Dy₃ triangles, with one CO₃^2– group being derived from atmospheric CO₂. The incorporation of an ortho-methoxy substituent into the ligand enables access to a double-CO₃^2– bridged Dy₆ SMM (<b>2</b>), where two CO₃^2– groups occupy the two bases of the triangular prism. The trapping of three CO₂ molecules of the atmosphere results in the formation of compound <b>3</b>, where the three CO₃^2– groups reside on the lateral faces of a triangular prismoid. Finally, a Dy₈ SMM (<b>4</b>) with four CO₃^2– bridges on the four lateral faces of the square prismoid can be isolated by converting four CO₂ molecules. The magnetic investigations reveal that all four complexes exhibit SMM behavior with a gradual transition from the multiple to single relaxation process observed in their relaxation of the magnetization. This synthetic approach represents an efficient method to develop novel CO₃^2–-bridged lanthanide clusters through spontaneous fixation of atmospheric CO₂ for magnetic dynamic studies

A Dodecanuclear Dysprosium Wheel Assembled by Six Vertex-Sharing Dy₃ Triangles Exhibiting Slow Magnetic Relaxation

Reactions of lanthanide­(III) (Ln^III) perchlorate (Ln = Dy and Ho) and a polydentate Schiff base resulted in the unprecedented assembly of novel Ln₁₂ wheels containing six vertex-sharing Ln₃ triangles. The Dy₁₂ derivative represents the largest lanthanide wheel based on the peculiar Dy₃ triangles showing slow magnetic relaxation

Family of Defect-Dicubane Ni₄Ln₂ (Ln = Gd, Tb, Dy, Ho) and Ni₄Y₂ Complexes: Rare Tb(III) and Ho(III) Examples Showing SMM Behavior

Reactions of Ln^III perchlorate (Ln = Gd, Tb, Dy, and Ho), NiCl₂·6H₂O, and a polydentate Schiff base resulted in the assembly of novel isostructural hexanuclear Ni₄Ln₂ complexes [Ln = Gd (<b>1</b>), Tb (<b>2</b>), Dy (<b>3</b>), Ho (<b>4</b>)] with an unprecedented 3d–4f metal topology consisting of two defect-dicubane units. The corresponding Ni₄Y₂ (<b>5</b>) complex containing diamagnetic Y^III atoms was also isolated to assist the magnetic studies. Interestingly, complexes <b>2</b> and <b>3</b> exhibit SMM characteristics and <b>4</b> shows slow relaxation of the magnetization. The absence of frequency-dependent in-phase and out-of-phase signals for the Ni–Y species suggests that the Ln ions’ contribution to the slow relaxation must be effectual as previously observed in other Ni–Dy samples. However, the observation of <i>χ″</i> signals with zero dc field for the Ni–Tb and Ni–Ho derivatives is notable. Indeed, this is the first time that such a behavior is observed in the Ni–Tb and Ni–Ho complexes

Pd-Catalyzed Intramolecular Cyclization via Direct C–H Addition to Nitriles: Skeletal Diverse Synthesis of Fused Polycyclic Indoles

The first example of Pd-catalyzed intramolecular C–H addition of indoles bearing cyanohydrin components at the C(3), C(2), and N(1) positions to nitriles is described. A wide range of functionalized partially saturated carbazoles, tetrahydro­pyrido­[1,2-<i>a</i>]­indole, and carbazoles can be prepared in good to excellent yields under the optimal conditions. In addition, fused polycyclic indoles with seven- or eight-membered rings can also be formed smoothly

Enhancement of Magnetocaloric Effect through Fixation of Carbon Dioxide: Molecular Assembly from Ln₄ to Ln₄ Cluster Pairs

A series <b>1.Ln</b> of tetranuclear lanthanide clusters [Ln₄(μ₄-O)­L₂­(PhCOO)₆]·solvent (Ln = Gd (<b>1.Gd</b>), Dy (<b>1.Dy</b>), Ho (<b>1.Ho</b>)) and octanuclear lanthanide Ln₄ cluster pairs <b>2.Ln</b> [Ln₈(μ₃–OH)₄(CO₃)₂L₄­(PhCOO)₈]·solvent (Ln = Gd (<b>2.Gd</b>), Dy (<b>2.Dy</b>), Tb (<b>2.Tb</b>)) were assembled by using a bi-Schiff-based ligand H₂L and characterized structurally and magnetically. Interestingly, the octanuclear Ln₄ cluster pairs <b>2.Ln</b> are proposed to be assembled from the tetranuclear clusters <b>1.Ln</b> through the uptake of CO₂ from air in a more basic media. X-ray structural analyses approved the possible evolution mechanism. Magnetic studies reveal the coexistence of ferro- and anti-ferromagnetic interaction in <b>1.Gd</b> and <b>2.Gd</b> by simulating the direct-current magnetic susceptibility and indicate the CO₃^2– bridges produce weak ferromagnetic interaction in <b>2.Gd</b> rather than anti-ferromagnetic interaction by benzoate bridges in <b>1.Gd</b>. The magnitude of the magnetocaloric effect has been examined and shows that complex <b>2.Gd</b> exhibits larger magnetocaloric effect than <b>1.Gd</b>, which could be probably ascribed to the weak ferromagnetic interaction produced by the CO₃^2– bridges

Molecular Magnetic Investigation of a Family of Octanuclear [Cu₆Ln₂] Nanoclusters

Reaction of in situ prepared acylhydrazone ligand with Ln­(NO₃)₃·6H₂O and Cu­(OAc)₂·H₂O resulted in the formation of novel isostructural octanuclear Cu₆Ln₂ compounds (Ln = Dy (<b>1</b>), Tb (<b>2</b>), Gd (<b>3</b>), Y (<b>4</b>)) with an unprecedented octametallic structure, which can be described as an oblate wheel built up from two structurally similar Cu₃ fragments linked together by two nodelike mononuclear lanthanide units. A detailed magnetic analysis reveals that the strong antiferromagnetic Cu···Cu interactions via the Cu–N–N–Cu–N–N–Cu linkage and the anticipated ferromagnetic Cu···Gd coupling makes an overall high-spin ground state in favor of the observation of significant magnetic caloric and SMM-like properties in the isotropic and anisotropic derivatives

Enhancement of Magnetocaloric Effect through Fixation of Carbon Dioxide: Molecular Assembly from Ln₄ to Ln₄ Cluster Pairs

A series <b>1.Ln</b> of tetranuclear lanthanide clusters [Ln₄(μ₄-O)­L₂­(PhCOO)₆]·solvent (Ln = Gd (<b>1.Gd</b>), Dy (<b>1.Dy</b>), Ho (<b>1.Ho</b>)) and octanuclear lanthanide Ln₄ cluster pairs <b>2.Ln</b> [Ln₈(μ₃–OH)₄(CO₃)₂L₄­(PhCOO)₈]·solvent (Ln = Gd (<b>2.Gd</b>), Dy (<b>2.Dy</b>), Tb (<b>2.Tb</b>)) were assembled by using a bi-Schiff-based ligand H₂L and characterized structurally and magnetically. Interestingly, the octanuclear Ln₄ cluster pairs <b>2.Ln</b> are proposed to be assembled from the tetranuclear clusters <b>1.Ln</b> through the uptake of CO₂ from air in a more basic media. X-ray structural analyses approved the possible evolution mechanism. Magnetic studies reveal the coexistence of ferro- and anti-ferromagnetic interaction in <b>1.Gd</b> and <b>2.Gd</b> by simulating the direct-current magnetic susceptibility and indicate the CO₃^2– bridges produce weak ferromagnetic interaction in <b>2.Gd</b> rather than anti-ferromagnetic interaction by benzoate bridges in <b>1.Gd</b>. The magnitude of the magnetocaloric effect has been examined and shows that complex <b>2.Gd</b> exhibits larger magnetocaloric effect than <b>1.Gd</b>, which could be probably ascribed to the weak ferromagnetic interaction produced by the CO₃^2– bridges

Anions Influence the Relaxation Dynamics of Mono‑μ₃‑OH-Capped Triangular Dysprosium Aggregates

A family of four Dy₃ triangular circular helicates, namely, [Dy₃(HL)₃(μ₃-OH)­(CH₃OH)₂(H₂O)₄]­Cl_1.5(OH)_0.5·0.5H₂O (<b>1</b>), [Dy₃(HL)₃(μ₃-OH)­(CH₃OH)₃(H₂O)₂Cl]­Cl·CH₃OH (<b>2</b>), [Dy₃(HL)₃(μ₃-OH)­(CH₃OH)₃(H₂O)₂(NO₃)]­(NO₃) (<b>3</b>), and [Dy₃(HL)₃(μ₃-OH)­(CH₃OH)₄(ClO₄)]­(ClO₄) (<b>4</b>), were assembled by the reaction of a new acylhydrazone ligand H₃L [(3-hydroxy)-<i>N</i>′-((8-hydroxyquinolin-2-yl)­methylene)­picolinohydrazide] with different dysprosium­(III) salts. These compounds represent the first examples of μ-O_{acylhydrazone}-bridged triangular Dy₃ SMMs reported to date. Alternating-current magnetic susceptibility measurements revealed that compounds <b>1</b> and <b>2</b> show typical SMM behavior with the occurrence of multiple relaxation processes, whereas frequency-dependent relaxation signals without χ″ peaks were observed in <b>3</b> and <b>4</b> under zero dc field. Such distinct dynamic behaviors are attributed to the different sizes of the terminal coordination solvent/anions (H₂O, Cl^–, NO₃^–, and ClO₄^– for <b>1</b>–<b>4</b>, respectively) at the Dy₃ site. Here, similar deviations from the ideal monocapped square-antiprismatic (<i>C</i>_4<i>v</i>) geometry defined by SHAPE software were observed around local Dy centers in <b>1</b> and <b>2</b>, whereas the situation was completely different in <b>3</b> and <b>4</b> as a result of the presence of relatively large anions in the limited space defined by three intercrossing rigid hydrazone ligands

Two Bulky-Decorated Triangular Dysprosium Aggregates Conserving Vortex-Spin Structure

The self-assembly of dysprosium­(III) with the tailored chemical modification of the vanillin group affords two decorated Dy₃ compounds, namely, [Dy₃(μ₃-OH)₂­(Hpovh^–)₃­(NO₃)₃­(CH₃­OH)₂­H₂O]·NO₃·3CH₃OH·2H₂O (<b>2</b>) and [Dy₃­(μ₃-OH)₂­(H₂­vovh^–)₃­Cl₂­(CH₃­OH)­(H₂O)₃]­[Dy₃­(μ₃-OH)₂­(H₂­vovh^–)₃­Cl₂­(H₂O)₄]·Cl₄·2CH₃­OH·2CH₃­CN·7H₂O (<b>3</b>), where H₂povh = <i>N</i>-(pyridylmethylene)-<i>o</i>-vanilloylhydrazone and H₃vovh = <i>N</i>-vanillidene-<i>o</i>-vanilloylhydrazone. Of particular interest is that those two title Dy₃ compounds maintain the peculiar vortex-spin structure of the ground nonmagnetic doublet. Complex <b>2</b> displays frequency-dependent slow magnetic relaxation, while <b>3</b> still inherits the single-molecule-magnet behavior as the parent Dy₃ prototype. The dissimilar dynamic magnetic behavior originates from the structural differences in light of the coordination environment of Dy^III ions, which influence the local tensor of anisotropy and crystal-field splitting on each Dy site