3d-4f单分子磁体*

单分子磁体是指那些在磁场下能够被磁化,当磁场去除后仍能保持磁性的单个分子。由于在信息处理和储存方面具有潜在的广泛应用前景,单分子磁体日益成为化学、材料科学和物理等学科的研究热点。近年来,同时含有镧系金属离子和过渡金属离子的3d-4f单分子磁体更是引起了很多研究者的兴趣。本文阐述了3d-4f单分子磁体的优势,总结了3d-4f单分子磁体的常见合成方法及其磁性,分析了影响3d-4f单分子磁体磁性的因素。     

Polyoxometalate-supported 3d-4f heterometallic single-molecule magnets

The reactions of [CuTbL(Schiff)(H(2)O)(3)Cl(2)]Cl complexes with A- or B-type Anderson polyoxoanions lead to new polyoxometalate-supported 3d-4f heterometallic systems with single-molecule-magnet behavior.     

A series of heterometallic 3d-4f polyoxometalates as single-molecule magnets

Three sandwich-like [Ln₂Fe₂(B-α-FeW₉O₃₄)₂]^10? clusters (Ln₂Fe₄, Ln = Dy (1), Ho (2), and Y (3)) were obtained by reacting Na₉[B-α-SbW₉O₃₃], Ln₂O₃, FeCl₃·6H₂O and KH₂PO₄. The [B-α-FeW₉O₃₄]^11? units were formed via the in situ conversion of lacunary polyoxometalates (POM) [B-α-SbW₉O₃₃]^9? and the Ln³⁺ ions were generated from the slow dissolution of Ln₂O₃, both of which play important roles in the synthesis of Ln₂Fe₄. Ln₂Fe₄ is the first 3d-4f cluster assembled from d-metal heteroatom-containing POM. The Dy₂Fe₄ cluster exhibits single-molecule magnet properties with an 80 K energy barrier in an optimal DC field. Cyclic voltammetry tests and controlled-potential coulometry experiments show that the polyoxometalate Fe heteroatom in clusters 1–3 is also electrochemically active.     

Heptanuclear 3d-4f cluster complexes with a coaxial double-screw-propeller topology and diverse magnetic properties

Two novel coaxial double-screw-propeller heptanuclear 3d-4f cluster complexes are ferromagnetic: one exhibits a large magnetocaloric effect while the other a magnetic relaxation behavior, depending on the lanthanoid ions used.     

A heterotrimetallic 3d-3d'-4f single chain magnet constructed from anisotropic high-spin 3d-4f nodes and paramagnetic spacers

By connecting [LCuTb](3+) nodes with [Fe(CN)?]3? spacers a 1-D coordination polymer with slow relaxation of magnetization is obtained (L2? is the N,N'-propylene-bis(3-methoxysalicylideneiminato) anion).     

High-nuclearity 3d-4f clusters as enhanced magnetic coolers and molecular magnets

Four 52-metal-ion 3d-4f cluster complexes featuring a common core of Ln(42)M(10) (Ln = Gd(3+), Dy(3+); M = Co(2+/3+), Ni(2+)) were obtained through self-assembly of the metal ions templated by mixed anions (ClO(4)(-) and CO(3)(2-)). Magnetic studies revealed that the Gd(42)Co(10) and Gd(42)Ni(10) clusters exhibit the largest magnetocaloric effect (MCE) among any known 3d-4f complexes. Replacement of Gd(3+) ions with anisotropic Dy(3+) ions caused significant changes in the magnetic behavior of the clusters; both Dy(42)Co(10) and Dy(42)Ni(10) displayed slow relaxation of the magnetization.     

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a Ln6Cu24Na12 cluster as a node

Two three-dimensional 2p-3d-4f heterometallic frameworks featuring a nanosized Ln(6)Cu(24)Na(12) (Ln = Gd, Dy) cluster as a node have been obtained under microwave irradiation conditions through the reaction of H(2)ANMA (H(2)ANMA = L-alanine-N-monoacetic acid), Cu(NO(3))(2), and Ln(NO(3))(3) (Ln = Gd for 1, Dy for 2) with NaOH in deionized water. Investigations on the magnetic properties show that 1 exhibits ferrimagnetic behavior. The electrical conductivity measurements reveal that 1 behaves as a proton conductor.     

A rational synthetic route leading to 3d-3d'-4f heterospin systems: self-assembly processes involving heterobinuclear 3d-4f complexes and hexacyanometallates

A novel heterospin system, [(CuL)Gd(H2O)3(Fe(CN)6)] x 4H2O, is obtained by reacting the mononuclear complex, [CuL], with gadolinium(III) nitrate, followed by the substitution of the nitrato groups with [Fe(CN)6](3-) ions (L2- = N,N'-propylenedi(3-methoxysalicylideneiminato)).     

Hexameric polyoxometalates decorated by six 3d-4f heterometallic clusters

Two nanosized hexameric polyoxometalate-based solid state assemblies (H(2)en)(6)Na(15)K(9)[Dy(6)Fe(6)(H(2)O)(12)(SiW(10)O(38))(6)]·34H(2)O (1) and K(13)Na(17)[H(2)en](3)[Tb(6)Fe(6)(H(2)O)(12)(SiW(10)O(38))(6)]·40H(2)O (2) (en = 1,2-ethylenediamine), decorated by six [Ln-(μ(3)-O)(3)-Fe] 3d-4f heterometallic clusters, have been synthesized by the hydrothermal method, and characterized by IR, element analysis, magnetic studies and the single-crystal X-ray analyses. The detailed study of the synthetic conditions reveals that the use of the organic ligands, pH value and the reaction temperature all play important roles in the synthesis of the 3d-4f heterometallic POMs. Magnetic study suggests the presence of antiferromagnetic interactions in these two compounds.     

Bifunctional ligand approach for constructing 3d-4f heterometallic clusters

Using a predesigned Schiff-base tripodal ligand, a heptanuclear CuII-GdIII cluster with a spin ground state of S=17/2 has been synthesized.     

Heterometallic 3d-4f polyoxometalates: still an incipient field

Heterometallic 3d-4f polyoxometalates still remain as an almost unexplored class of polyoxoanions despite showing great potential in fields such as molecular magnetism. This Frontier reviews some of their synthetic, structural and magnetic features and gives a personal view on future research in this area.     

Synthesis and structural characterization of a novel two-dimensional 3d-4f heterometallic coordination framework based on pentanuclear lanthanide cluster

A novel 3d-4f heterometallic coordination polymer, {[Tm₅(μ₃-OH)₂(BDC)₆(IN)₂Cu(H₂O)₂]·(H₂O)₃}_n (1) [BDC = benzene-1,2-dicarboxylate, IN = isonicotinate], has been hydrothermally synthesized and structurally characterized by single crystal X-ray diffraction, FTIR, elemental analysis, powder X-ray diffraction and thermogravimetric analysis. The compound crystallizes in monoclinic system, space group P2₁/c (No. 14), a = 13.7302(5) Å, b = 23.5428(3) Å, c = 21.5789(2) Å, β = 91.491(3)°, V = 6973.0(3) ų, and Z = 4. The structure exhibits unusual two-dimensional Tm-carboxylate layer, which is constructed from the expansion of novel pentanuclear {Tm₅} clusters. More interestingly, the heterometallic Cu(I) ions were successfully planted into such Ln-carboxylate layer by the bifunctional IN bridging ligands, resulting in the formation of an unprecedented 2D heterometallic lanthanide-transition-metal framework.     

New type of heterometallic 3d-4f rhomblike core in Weakley-like polyoxometalates

The first heterometallic copper-cerium polyoxometalate, [{Ce(IV)(OAc)}Cu(II)(3)(H(2)O)(B-α-GeW(9)O(34))(2)](11-) (1), is composed of an unprecedented copper(II)-trisubstituted Weakley-type tungstogermanate subunit stabilized by coordination of a {Ce(OAc)}(3+) group at the vacant position. The title species contains a central {Ce(IV)Cu(II)(3)O(18)} rhomblike cluster that belongs to a new {(4f(ext))(3d(ext))(3d(int))(2)} type and magnetically behaves as a triangular Cu(3) system with overall antiferromagnetic exchange affected by the structural distortions the vicinity of diamagnetic Ce(IV) induces.     

Construction of 1-D 4f and 3d-4f coordination polymers with flexible Schiff base ligands

Three new lanthanide 1-D coordination polymers ({[Ln(2)(H(2)L)(OAc)(6)]·EtOH·2H(2)O}(n) (Ln = Eu (1), Er (2)) and {YbNiLCl(OAc)(2)(H(2)O)}(n) (3)) and a heterobinuclear complex [YbNiLCl(3)(H(2)O)(3)] (4) are reported which are formed from salen type Schiff-base ligands H(2)L (H(2)L = N,N'-bis(3-methoxysalicylidene)butane-1,4-diamine). The polymeric structures are formed by bridging H(2)L units in the case of 1 and 2, and by acetate groups in 3. The structures of 1-4 were determined by single crystal X-ray crystallographic studies and their luminescence properties in MeCN solution were determined.     

A tetranuclear, macrocyclic 3d-4f complex showing single-molecule magnet behavior

[Cu(II)(3)Tb(III)(L(Pr))(NO(3))(2)(MeOH)(H(2)O)(2)](NO(3))·3H(2)O is a rare example of a 3d-4f single-molecule magnet prepared using a macrocyclic ligand: at low T, it exhibits frequency-dependent alternating-current susceptibility, indicative of slow relaxation of the magnetization.     

Two-dimensional 3d-4f networks containing planar Co4Ln2 clusters with single-molecule-magnet behaviors

Two novel two-dimensional 3d-4f networks based on planar Co(4)Ln(2) clusters supported by rigid 4'-(4-carboxyphenyl)-2,2':6',2"-terpyridine afford the first examples of high-dimensional networks with 3d-4f clusters behaving as single-molecule magnets.     

A family of three-dimensional 3d-4f and 4d-4f heterometallic coordination polymers based on mixed isonicotinate and 2-sulfobenzoate ligands: syntheses, structures and photoluminescent properties

Hydrothermal reactions of isonicotinic acid (Hina), 2-sulfobenzoic acid (H(2)sba), d-block metal salts and lanthanide oxides/hydroxides yielded 17 three-dimensional (3D) 3d-4f and 4d-4f heterometallic coordination polymers (HCPs). They are formulated as [LaAg(sba)(ina)(2)](n) (1), [Ln(2)Ag(2)(sba)(2)(ina)(4)(H(2)O)(2)](n) [Ln = Pr (2), Nd (3), Sm (4), Eu (5), Gd (6), Tb (7), Dy (8), Ho (9), Er (10)] and [Ln(2)Cu(2)(sba)(2)(ina)(4)(H(2)O)(2)](n) [Ln = La (11), Pr (12), Nd (13), Sm (14), Eu (15), Gd (16), Tb (17)]. Their structures were characterized by single crystal X-ray diffraction, powder X-ray diffraction (XRD), infrared (IR) spectroscopy, elemental analysis (EA), and thermogravimetric analysis (TGA). It reveals that they represent two structural types of 3D HCPs. Furthermore, the investigations of their solid-state photoluminescent (PL) property demonstrate the extraordinary emission behaviors. HCP 1(La-Ag) exhibits tunable blue-to-green PL emissions by variation of excitation light. HCPs 6(Gd-Ag), 11(La-Cu), 12(Pr-Cu) and 16(Gd-Cu) show d(10)-metal-based ligand-to-metal charge transfer (LMCT) or metal-to-ligand charge transfer (MLCT) emissions. HCPs 3(Nd-Ag), 4(Sm-Ag), 5(Eu-Ag), 7(Tb-Ag), 8(Dy-Ag), 13(Nd-Cu), 14(Sm-Cu), 15(Eu-Cu) and 17(Tb-Cu) display characteristic PL emissions of the corresponding Ln(III) ions, while both d(10)-metal-based and 4f-metal-centered emissions are observed in the emission spectra of 4(Sm-Ag), 8(Dy-Ag), 14(Sm-Cu) and 17(Tb-Cu).