Two Zinc(II) Complexes with 1D Chain and 2D Layer Directed by Competitive Coordination of the Mixed Ligands: Syntheses, Crystal Structures, and Fluorescent Properties

<p>Two new competitive coordination-directed zinc(II) complexes, [Zn₂(bpp)₂(na)₄]<i>_n</i> (<b>1</b>) and [Zn(bpp)₂(nas)₂]<i>_n</i> (<b>2</b>) (bpp = 1,3-bi(4-pyridyl)propane, na⁻ = 1-naphthoate, and nas⁻ = 2-aminonaphthalene-1-sulfonate), were hydrothermally synthesized by varying carboxylate- or sulfonate-containing coligands. Structural analyses reveal that complex <b>1</b> modified by terminal na⁻ spacers possesses a bent one-dimensional chain bridged by ditopic bpp linkers. By contrast, complex <b>2</b> with two monodentate nas⁻ ligands exhibits a two-dimensional layered structure extended by four equatorial bpp connectors. Obviously, the increase on the dimensionality of <b>2</b> than <b>1</b> is significantly resulting from the competitive coordination of the two mixed ligands with differently tunable binding groups to variable metal polyhedra. In addition, both complexes with analogously high thermal stability display strong fluorescent emissions at room temperature resulting from the ligand-to-metal or intraligand charge-transfer, suggesting their hopeful applications as efficient fluorescent materials.</p

Three-Dimensional Hierarchical Nickel Cobalt Phosphide Nanoflowers as an Efficient Electrocatalyst for the Hydrogen Evolution Reaction under Both Acidic and Alkaline Conditions

The sustainable hydrogen fuel from water electrolysis demands the development of efficient and robust non-noble electrocatalysts for the hydrogen evolution reaction (HER). Tuning the morphology and chemical composition is paramount to constructing electrocatalysts with superior activity and stability. In this work, novel ternary nickel-doped cobalt phosphide (Ni–Co–P) nanoflowers assembled by porous and unltrathin nanosheets were first prepared by a facile solvothermal reaction following a phosphidation procedure. The Ni–Co–P nanoflowers exhibited remarkable electrocatalytic HER performance, exhibiting overpotentials of as low as 83 and 92 mV at 10 mA cm^–2 and small Tafel slopes of 46.6 and 49.6 mV dec^–1 under1 M KOH and 0.5 M H₂SO₄ conditions, respectively, which was one of the most active earth-abundant electrocatalysts. Additionally, the electrocatalysts exhibited high durability for HER under both alkaline and acidic conditions. Various techniques further demonstrated that the superior activity of Ni–Co–P nanoflowers was attributed to the unique 3D hierarchical morphology and the modified electron structure due to Ni incorporation. The superior activity and stability of novel Ni–Co–P nanoflowers hold promising potential for applications in the production of hydrogen fuel from water splitting

Diverse Self-Assembly from Predesigned Conformationally Flexible Pentanuclear Clusters Observed in a Ternary Copper(II)–Triazolate–Sulfoisophthalate System: Synthesis, Structure, and Magnetism

Self-assembly from the predesigned Cu^II₅ secondary building unit (SBU) in the ternary Cu^II–triazolate–sulfoisophthalate system generates three interesting magnetic samples: an open pillared-layer framework with nanosized Cu^II₃₀ metallamacrocycle-based sublayer (<b>1</b>), a (3,6)-connected 2-fold interpenetrating network consisting of alternating Cu^II₅ and Cu^II₁ cores (<b>2</b>), and a (4,8)-connected architecture constructed from centrosymmetric Cu^II₇ clusters and four-branched 5-sulfoisophthalate (sip^3–) connectors (<b>3</b>). These various structures significantly result from the variable connectivity and the slight expansion of the predetermined conformationally flexible Cu^II₅ SBUs. Furthermore, these intriguing structural motifs in <b>1</b>–<b>3</b> essentially induce different magnetic phenomena. A field-dependent metamagnetic transition from antiferromagnetic ordering to weak ferromagnetism is observed in the frustrated Cu^II₃₀-based sublayer of <b>1</b>. The paramagnetic Cu^II₁ core in <b>2</b> virtually contributes to an <i>S</i> = ¹/₂ spin ground state due to the completely compensated magnetic moment in the 1,2,3-triazolate (ta^–)-bridged Cu^II₅ cluster containing ribbon. In contrast, strong antiferromagnetic interactions in the locally centrosymmetric Cu^II₇ cluster lead to an overall <i>S</i> = ¹/₂ spin ground state of <b>3</b>. Thus, the SBU-derived self-assembly strategy provides important hints for polymetallic cluster based high-dimensional magnetic materials, which also brings a new vision for the design and construction of novel functional materials

Diverse Self-Assembly from Predesigned Conformationally Flexible Pentanuclear Clusters Observed in a Ternary Copper(II)–Triazolate–Sulfoisophthalate System: Synthesis, Structure, and Magnetism

Self-assembly from the predesigned Cu^II₅ secondary building unit (SBU) in the ternary Cu^II–triazolate–sulfoisophthalate system generates three interesting magnetic samples: an open pillared-layer framework with nanosized Cu^II₃₀ metallamacrocycle-based sublayer (<b>1</b>), a (3,6)-connected 2-fold interpenetrating network consisting of alternating Cu^II₅ and Cu^II₁ cores (<b>2</b>), and a (4,8)-connected architecture constructed from centrosymmetric Cu^II₇ clusters and four-branched 5-sulfoisophthalate (sip^3–) connectors (<b>3</b>). These various structures significantly result from the variable connectivity and the slight expansion of the predetermined conformationally flexible Cu^II₅ SBUs. Furthermore, these intriguing structural motifs in <b>1</b>–<b>3</b> essentially induce different magnetic phenomena. A field-dependent metamagnetic transition from antiferromagnetic ordering to weak ferromagnetism is observed in the frustrated Cu^II₃₀-based sublayer of <b>1</b>. The paramagnetic Cu^II₁ core in <b>2</b> virtually contributes to an <i>S</i> = ¹/₂ spin ground state due to the completely compensated magnetic moment in the 1,2,3-triazolate (ta^–)-bridged Cu^II₅ cluster containing ribbon. In contrast, strong antiferromagnetic interactions in the locally centrosymmetric Cu^II₇ cluster lead to an overall <i>S</i> = ¹/₂ spin ground state of <b>3</b>. Thus, the SBU-derived self-assembly strategy provides important hints for polymetallic cluster based high-dimensional magnetic materials, which also brings a new vision for the design and construction of novel functional materials

Structural Transformation from a Discrete Cu^II₄ Cluster to Two Extended Cu^II₄ + Cu^II₁ Chain-Based Three-Dimensional Frameworks by Changing the Spacer Functionality: Synthesis, Crystal Structures, and Magnetic Properties

Three unique [Cu₄(μ₃-OH)₂]⁶⁺ core-based magnetic complexes, [Cu₄(amtrz)₂(μ₃-OH)₂(nb)₆]·2H₂O (<b>1</b>), {[Cu₅(H₂O)₆(trz)₂(μ₃-OH)₂(btc)₂]·0.6H₂O}_<i>n</i> (<b>2</b>), and {[Cu₅(H₂O)₂(Htrz)₂(μ₃-OH)₂(btec)₂]·0.125H₂O}_<i>n</i> (<b>3</b>) (amtrz = 4-amino-1,2,4-triazole, Htrz = 1,2,4-triazole, Hnb = 4-nitrobenzoic acid, H₃btc = 1,2,3-benzenetricarboxylic acid, and H₄btec = 1,2,4,5-benzenetetracarboxylic acid), were synthesized by varying the spacer functionality of the mixed ligands. Significantly resulting from the cooperative cocoordination of the metal ions with polytopic triazolyl and carboxylate groups, a structural transformation from a discrete Cu^II₄ cluster for <b>1</b> to two alternate Cu^II₄ + Cu^II₁ chain-based three-dimensional frameworks for <b>2</b> and <b>3</b> was achieved. Moreover, the connectivity manner of the structural subunits in <b>2</b> and <b>3</b> depends strongly on the number and position of the carboxylate group attached on the phenyl backbone. The nearest-neighbor interactions within the Cu^II₄ cluster and between Cu^II₄ cluster and Cu^II₁ core mediated by the mixed short bridges were quantitatively calculated and compared based on the established magneto-structural relationships. Strong antiferromagnetic coupling interactions up to −206(4) cm^–1 were observed in the isolated Cu^II₄ cluster due to the favorable spatial orientation of the mixed multiple heterobridges toward the spin carriers

Diverse Self-Assembly from Predesigned Conformationally Flexible Pentanuclear Clusters Observed in a Ternary Copper(II)–Triazolate–Sulfoisophthalate System: Synthesis, Structure, and Magnetism

Self-assembly from the predesigned Cu^II₅ secondary building unit (SBU) in the ternary Cu^II–triazolate–sulfoisophthalate system generates three interesting magnetic samples: an open pillared-layer framework with nanosized Cu^II₃₀ metallamacrocycle-based sublayer (<b>1</b>), a (3,6)-connected 2-fold interpenetrating network consisting of alternating Cu^II₅ and Cu^II₁ cores (<b>2</b>), and a (4,8)-connected architecture constructed from centrosymmetric Cu^II₇ clusters and four-branched 5-sulfoisophthalate (sip^3–) connectors (<b>3</b>). These various structures significantly result from the variable connectivity and the slight expansion of the predetermined conformationally flexible Cu^II₅ SBUs. Furthermore, these intriguing structural motifs in <b>1</b>–<b>3</b> essentially induce different magnetic phenomena. A field-dependent metamagnetic transition from antiferromagnetic ordering to weak ferromagnetism is observed in the frustrated Cu^II₃₀-based sublayer of <b>1</b>. The paramagnetic Cu^II₁ core in <b>2</b> virtually contributes to an <i>S</i> = ¹/₂ spin ground state due to the completely compensated magnetic moment in the 1,2,3-triazolate (ta^–)-bridged Cu^II₅ cluster containing ribbon. In contrast, strong antiferromagnetic interactions in the locally centrosymmetric Cu^II₇ cluster lead to an overall <i>S</i> = ¹/₂ spin ground state of <b>3</b>. Thus, the SBU-derived self-assembly strategy provides important hints for polymetallic cluster based high-dimensional magnetic materials, which also brings a new vision for the design and construction of novel functional materials

Molecular Binding Behaviors of Sulfonated Calixarenes with Phenanthroline-diium in Aqueous Solution and Solid State: Cavity Size Governing Capsule Formation

The molecular binding behaviors of <i>p</i>-sulfonatocalix­[4]­arene (SC4A), <i>p</i>-sulfonatocalix­[5]­arene (SC5A), and <i>p</i>-sulfonatothiacalix­[4]­arene (STC4A) with 5,6-dihydropyrazion­[1,2,3,4-<i>lmn</i>]­[1,10]­phenanthroline-4,7-diium (DP²⁺) were systematically investigated by crystallography, NMR spectroscopy, and microcalorimetry at pH 1–2. The obtained results showed that, in both aqueous solution and the solid state, DP²⁺ was immersed into the cavity of the sulfonated calixarene host in a slantwise degree with the aromatic moiety being included first. The different slantwise degree of the guest in the host cavity determined whether the host–guest capsule could be formed in the solid state. Furthermore, all three sulfonated calixarene hosts showed high affinities with DP²⁺ in the magnitude of 10⁵–10⁶ M^–1 in aqueous solution, and the binding modes for host–guest complexation were explained from a thermodynamic viewpoint

Three Isostructural One-Dimensional Ln^III Chains with Distorted Cubane Motifs Showing Dual Fluorescence and Slow Magnetic Relaxation/Magnetocaloric Effect

Three new homometallic lanthanide complexes with mixed carboxylate-modified rigid ligands, [Ln­(μ₃-OH)­(na)­(pyzc)]_<i>n</i> (na^– = 1-naphtholate, pyzc^– = 2-pyrazinecarboxylate, Ln = Dy (<b>1</b>), Yb (<b>2</b>), and Gd (<b>3</b>)), were solvothermally synthesized, and their structures and magnetic as well as photophysical properties were completely investigated. Complexes <b>1</b>–<b>3</b> are crystallographically isostructural, exhibiting linear chains with four bidentate bridging μ-COO^– moieties encapsulated cubic {Ln₄(μ₃-OH)₄}⁸⁺ clusters repeatedly extended by 4-fold chelating-bridging-pyzc^– connectors. Magnetically, the former two complexes with highly anisotropic Dy^III and weak anisotropic Yb^III ions in the distorted NO₇ triangular dodecahedron coordination environment display field-induced slow relaxation of magnetization. Fitting the dynamic magnetic data to the Arrhenius law gives energy barrier Δ<i>E</i>/<i>k</i>_B = 39.6 K and pre-exponential factor τ_o = 1.52 × 10^–8 s for <b>1</b> and Δ<i>E</i>/<i>k</i>_B = 14.1 K and τ_o = 2.13 × 10^–7 s for <b>2</b>. By contrast, complex <b>3</b> with isotropic Gd^III ion and weak intracluster antiferromagnetic coupling shows a significant cryogenic magnetocaloric effect, with a maximum −Δ<i>S</i>_m value of 30.0 J kg^–1 K^–1 at 2.5 K and 70 kOe. Additionally, the chromophoric na^– and pyzc^– ligands can serve as antenna groups, selectively sensitizing the Dy^III- and Yb^III-based luminescence of <b>1</b> and <b>2</b> in the UV–visible region by an intramolecular energy transfer process. Thus, complexes <b>1</b>–<b>3</b>, incorporating field-induced slow magnetic magnetization and interesting luminescence together, can be used as composite magneto-optical materials. More importantly, these interesting results further demonstrate that the mixed-ligand system with rigid carboxylate-functionalized chromophores can be excellent candidates for the preparations of new bifunctional magneto-optical materials

Magnetic Relaxation Dynamics of a Centrosymmetric <b>Dy₂</b> Single-Molecule Magnet Triggered by Magnetic-Site Dilution and External Magnetic Field

A centrosymmetric <b>Dy</b>_<b>2</b> single-molecule magnet (SMM) and its doped diamagnetic yttrium analogues, <b>Dy</b>_<b>0.19</b><b>Y</b>_<b>1.81</b> and <b>Dy</b>_<b>0.10</b><b>Y</b>_<b>1.90</b>, were solvothermally synthesized to investigate the effects of intramolecular exchange coupling and quantum tunneling of magnetization (QTM) on the magnetic relaxation dynamics. Constructed from two hula-hoop-like Dy^III ions and a pair of phenoxido groups, the antiferromagnetically coupled <b>Dy</b>_<b>2</b> exhibits a thermal-activated zero-field effective energy barrier (<i>U</i>_eff) of 277.7 K and negligible hysteresis loop at 2.0 K. The doping of a diamagnetic Y^III matrix with 90.5% and 95.0% molar ratios reveals the single-ion origin of the Orbach channel, increases the relaxation time by partially quenching the QTM process, and induces an open hysteresis loop until 5.0 K. In contrast, an optimal dc field of 1.0 kOe improves the barrier height up to 290.1 K through complete elimination of the QTM and delays the relaxation time of the direct relaxation pathway. More interestingly, the collaborative dual effects of magnetic-site dilution and external magnetic field make the effective energy barrier and relaxation time increase 8.1% and 49 times, respectively. Thus, the overall magnetization dynamics of the <b>Dy</b>_<b>2</b> system systematically elaborate the inherent interplay of the QTM and Orbach processes on the effective energy barrier, highlighting the vital role of the relaxation time on the coercive hysteresis loop

Two 3-Amino-1,2,4-triazole-based Manganese(II) Complexes Incorporated With Different Dicarboxylate Coligands: Synthesis, Structure, and Magnetism

<div><p>Two 3-amino-1,2,4-triazole (Hatz)-based magnetic complexes, {[Mn₃(H₂O)₂(Hatz)₂(sip)₂]·2H₂O}<i>_n</i> (<b>1</b>) and {[Mn(H₂O)₃(Hatz)(bda)]·H₂O}<i>_n</i> (<b>2</b>) (sip³⁻ = 5-sulfoisophthalate and bda²⁻ = <i>trans</i>-butenedioate), were respectively prepared by varying dicarboxylate-containing coligands, and were structurally and magnetically characterized. Structural determinations reveal that <b>1</b> exhibits a two-dimensional layered structure with linear {Mn₃(μ-N1,N2-Hatz)₂}⁶⁺ subunits extended by tritopic sip³⁻ connectors. By contrast, <b>2</b> is an infinite <i>zigzag</i> chain constructed from octahedral Mn(II) ions and μ-N1,N4-Hatz linkers. Magnetically, typically antiferromagnetic interaction observed in the local Mn^II₃ subunit of <b>1</b> mediated by mixed μ-<i>syn, syn</i>-COO⁻ and μ-N1,N2-Hatz heterobridges is slightly stronger than that of <b>2</b> transmitted by single μ-N1,N4-Hatz mediator.</p></div