Three-dimensional 3d-4f polymers containing heterometallic rings: syntheses, structures, and magnetic properties

Two novel three-dimensional (3D) 3d-4f mixed complexes [Ln(H(2)O)(4)][Ni(2)TTHA(SCN)(2)].H(3)O+ [Ln = Pr (1), Ce (2); H(6)TTHA = triethylenetetraaminehexaacetic acid], based on the building blocks of [Ni(2)TTHA(SCN)(2)](4-), were synthesized and characterized by X-ray crystal diffraction and magnetic properties. The single-crystal structures show that these complexes form a 3D framework, comprised of an unusual infinite one-dimensional chain based on heterometallic Ln2Ni2 rings. The temperature-dependent magnetic susceptibilities were analyzed by an approximate model, leading to g = 2.06. Delta = 2.83, zJ' = -0.6 cm-1 for complex 1 and g = 2.07, Delta = 1.00, zJ' = -0.5 cm(-1) for complex 2.     

A series of 3d-4f heterometallic three-dimensional coordination polymers: syntheses, structures and magnetic properties

Seven lanthanide-cobalt heterometallic three-dimensional coordination polymers: {[Ln(3)Co(2)(BPDC)(5)(HBPDC)(H(2)O)(5)](ClO(4))(2)·mH(2)O}(n) (Ln = Eu (1, m = 10.25), Gd (2, m = 8), Tb (3, m = 9.5), Dy (4, m = 11), Ho (5, m = 10.5), Tm (6, m = 11), Lu (7, m = 10.25); BPDC = 5,5'-dicarboxylate-2,2'-dipyridine anion) were structurally and magnetically characterized. Compounds 1-7 crystallize in the orthorhombic space group Pbca, featuring a 3D sandwich framework. Magnetic properties of 2-6 have been investigated by using DC (direct current) and AC (alternating current) susceptibility measurements. Among these compounds, only compound 4 displays significant frequency dependence, albeit without reaching the characteristic maxima above 2 K, implying slow magnetic relaxation behavior in 4. After the application of a DC field, good peak shapes of AC signals were obtained and the energy barrier ΔE/k(B) = 62.89 K and the preexponential factor τ(0) = 6.16 × 10(-8) s. To our knowledge, 4 has the highest energy barrier in Ln-Co SMM systems hitherto.     

Synthesis, crystal structure, and magnetic properties of two 3d-4f heterometallic coordination polymers

Two new 4f-3d heterometallic coordination polymers, [Gd₂^IIICo^II(pydc)₃(ox)(H₂O)₄)·2H₂O] (1) and [Dy^IIICu^II(pydc)₂(ox)_1/2(H₂O)₂·H₂O] (2) (pydc = pyridine-2,5-dicarboxylate anion, ox = oxalate dianion) were successfully synthesized under hydrothermal condition. Structure and magnetism of the two coordination polymers were characterized by single crystal X-ray diffraction and Quantum Design (MPMS) SQUID magnetometer. In both compounds, metal centers were connected by double ligand bridges. In 1 the gadolinium ions were linked in sheets by OCO ligand bridges and these sheets were connected by separated cobalt coordination spheres to generate the overall 2-D structure. In 2 the dysprosium centers were constructed into one dimensional chain by OCO bridges from pydc ligand bridges and these chains were linked by oxalate bridges to form sheets and different sheets were connected by copper coordination planes. The copper centers in 2 were linked in chain by elongated OCO brides and the chains were connected by hydrogen bond to generate 3-D structure. Magnetic properties of the two complexes were investigated by variable temperature magnetic susceptibility. The magnetic data suggest that overall antiferromagnetic interactions are present in the two compounds.     

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).     

Novel heterometallic 3d-4f metal-azido complex of mixed ligands with unprecedented structure type: synthesis, structure, and magnetic properties

A novel heterometallic 3d-4f metal-azido complex of mixed ligands, showing unprecedented structure type and interesting magnetic properties, has been hydrothermally synthesized and characterized.     

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.     

Heterotrimetallic 4f-3d coordination polymers: synthesis, crystal structure, and magnetic properties

A series of cyano-bridged heterotrimetallic complexes [CuL](2)Ln(H(2)O)(2)M(CN)(6).7H(2)O have been synthesized by the reactions of CuL (L(2)(-) = dianion of 1,4,8,11-tetraazacyclotradecane-2,3-dione), Ln(3+) (Ln = Gd or La), and [M(CN)(6)](3)(-) (M = Co, Fe, or Cr). X-ray diffraction analysis reveals that these complexes are isostructural and have a novel chain structure. The Ln(3+) ion is eight-coordinated by six oxygen atoms of two CuL and two water molecules and two nitrogen atoms of the bridging cyano ligands of two [M(CN)(6)](3)(-), while the [M(CN)(6)](3)(-) anion connects two Ln(3+) using two trans-CN(-) ligands giving rise to a chainlike structure. In the chain, every CuL group tilts toward the CN(-) ligand of adjacent [M(CN)(6)](3)(-) with the Cu-N(cyano) contacts ranging from 2.864(6) to 2.930(6) A. Magnetic studies on the CuGdCo complex (1) indicate the presence of ferromagnetic coupling between Cu(II) and Gd(III). The CuLaCr (5) and CuLaFe (2) complexes exhibit ferromagnetic interaction between paramagnetic Cu(II) and Cr(III)/Fe(III) ions through the weak cyano bridges (Cu-N(cyano) = 2.930(6) A for 2). A global ferromagnetic interaction is operative in the CuGdFe complex (3) with the concurrence of dominant ferromagnetic Cu(II)-Gd(III) and minor antiferromagnetic Gd(III)-Fe(III) as well as the ferromagnetic Cu(II)-Fe(III) interaction. For the CuGdCr complex (4), an overall antiferromagnetic behavior was observed, which is attributed to the presence of dominant antiferromagnetic Cr(III)-Gd(III) coupling and the minor ferromagnetic Cu(II)-Gd(III) and Cu(II)-Cr(III) interaction. Moreover, a spin frustration phenomenon was found in complex 4, which results from the ferro-ferro-antiferromagnetic exchanges in the trigonal Cu-Gd-Cr units. The magnetic susceptibilities of these complexes were simulated using suitable models. The magneto-structural correlation was investigated. These complexes did not show a magnetic phase transition down to 1.8 K.     

One pot synthesis of heterometallic 3d-3d azido architectures: assembling strategy and magnetic properties

The Cu(II) ions usually have different coordinated geometry to other 3d ions, especially Ni(II) and Co(II) ions, in azido-carboxylate mixed ligand systems. That provides a potential way to synthesize rare heterometallic 3d-3d azido complexes with peculiar magnetic properties. Assembling Cu(II), M(II) (M = Ni and Co), azido and nicotinic acid in hydrothermal condition, two novel isomorphic 3D heterometallic 3d-3d azido complexes, [CuM(N(3))(2)(nicotinate)(2)](∞) (M = Ni(II) for 1 and Co(II) for 2) were obtained. The structure of the complexes can be described as EO azido and syn,syn carboxylate mixed bridged spin sequence chains (-1/2-J(1)-1-J(2)-1/2- for 1 and -1/2-J(1)-3/2-J(2)-1/2- for 2) linked by the pyridyl groups. Dominant ferromagnetic interactions were observed between the Cu(II) and M(II) ions in the chains despite the largest M-N-M angle of about 129° in the 3d metal azido-carboxylate mixed coordinated systems and weak antiferromagnetic interactions between the chains. At low temperature, a spin-flop phase transition was present in the Co(II) involved complex 2.     

A new polyoxometalate-based 3d-4f heterometallic aggregate: a model for the design and synthesis of new heterometallic clusters

A new polytungstoarsenate-based 3d-4f heterometallic aggregate has been synthesized, consisting of three {alpha-AsW10 O 38} fragments bridged by three {Fe-(mu3-O)3-Ce} heterometallic clusters.     

New heterometallic coordination polymers derived form chalcogenocyanates: synthesis,characterization and electrical properties

A series of conducting mixed-metallic coordination polymers: Cu₂Pb(SCN)₄, CuPb(SeCN)₄, Cu^II _0.50Cu^IPb (SCN·SeCN)₂, CuAg(SCN)₂, CuAg(SeCN)₂ and CuAg(SCN·SeCN) have been synthesized by the reaction of Cu and Pb^II or Ag^Initrates with KSCN or KSeCN, or both KSCN and KSeCN in H₂O. Of significance are the aerobic reactions which yield heterometallic complexes viaoxidation of SCN^– and SeCN^– into (SCN)₂ and (SeCN)₂ followed by quantitative reduction of Cu^II into Cu^I; in the case of CuPb(SeCN)₄ reduction of Cu^II into Cu^I is not observed, while in Cu^{II 0.50}Cu^IPb(SCN·SeCN)₂, Cu^II is partially reduced to Cu^I. These compounds have been characterized by elemental (C, N, S and Se) analyses, magnetic moment measurements, relevant spectroscopies (i.r., far i.r., Raman, u.v.–vis. and e.p.r.), powder X-ray diffraction pattern and conductivity technique. The v(CN) vibrations in 2162–2087cm^–1 and far i.r. bands (500–100cm^–1) corroborated by Raman bands are conclusive of the bridging (N, S/Se) mode and metal-NCS and metal-SCN/SeCN^– bonding respectively in the complexes. Room temperature magnetic moment, electronic absorption spectra and e.p.r. active/silent nature confirm the oxidation state of copper in these solids. Room temperature compressed pellet conductivities _rt, 10^–9to 10^–7Scm^–1 with activation energies, E _a=0.19–0.25eV and increase in the conductivity with increase in temperature in the 305–423K, range and decrease in conductivity with decrease in temperature in the 295–200K range, show their semiconductor properties.     

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.     

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.     

High-nuclearity 3d-4f [FeIII5LnIII8] complexes: synthesis, structure and magnetic properties

The isostructural tridecanuclear mixed-metal [FeIII5LnIII8] (Ln = Pr, Nd, Gd) aggregates are the largest [Fe-Ln] clusters reported to date and the magnetic properties suggest a ferrimagnetic arrangement in [Fe5Pr8] and [Fe5Nd8], whereas for [Fe5Gd8] ferromagnetic interactions are dominant leading to a large spin ground state.     

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.     

Syntheses,structures and magnetic studies of three heterometallic Fe2Ln 1D coordination polymers

Three new heterometallic 1D coordination polymers [Fe^III₂Pr(4-Me-sal)₄(2,2′-bipy)₂(H₂O)₆](NO₃) · 2MeOH · 1.5H₂O (1), [Fe^III₂Gd(4-Me-sal)₄(2,2′-bipy)₂(H₂O)₅]Cl_1/2(NO₃)_1/2 · 5H₂O (2) and [Fe^III₂Dy(4-Me-sal)₄(2,2′-bipy)₂(H₂O)₅]Cl_1/2(NO₃)_1/2 · 5H₂O (3) have been synthesized. 1 and 2 were characterized by single-crystal X-ray crystallography, and 3 was shown to be isomorphous to 2 by X-ray powder diffraction. Magnetic studies show that the three compounds show a similar temperature dependence of their magnetic susceptibilities over the range 1.8–300 K. The observed decrease of χT with decreasing temperature for all three compounds could be the result of antiferromagnetic interactions between Fe–Ln centres and/or the depopulation of the Stark sublevels in the case of the anisotropic Ln ions (Pr^III and Dy^III).     

Syntheses, crystal structures and properties of two unusual pillared-layer 3d-4f Ln-Cu heterometallic coordination polymers

Two unusual pillared-layer 3d-4f Ln-Cu heterometallic coordination polymers, {[Ln₂Cu₅Br₄(IN)₇(H₂O)₆]·H₂O}_n (Ln=Eu (1) and Gd (2), HIN=isonicotinic acid), have been synthesized under hydrothermal conditions, and characterized by elemental analysis, IR, thermal analysis and single-crystal X-ray diffraction. The structure determination reveals that 1 and 2 are isostructural and feature a novel three-dimensional pillared-layer hetrometallic structure built upon the linkages of one-dimensional (1D) linear Ln-carboxylate chains, zero-dimensional (0D) Ln-carboxylate Ln₂(IN)₈ dimers, rare 1D zigzag [Cu₅Br₄]_n inorganic chains and IN⁻ pillars. In both 3D structures, there are Ln-carboxylate layers resulted from the connections of 1D Ln-carboxylate chains and 0D Ln₂(IN)₈ dimers through O-H?O hydrogen bondings. The luminescent properties of 1 have been investigated. The magnetic properties of 1 and 2 have also been studied.     

Two novel heterometallic Cu(II)-Sr(II) coordination polymers based on 3,5-pyrazoledicarboxylic acid: synthesis, crystal structures and magnetic properties

The syntheses, crystal structures and magnetic properties are described for two novel 2D heterometallic Cu(II)-Sr(II) coordination polymers {Sr(H(2)O)(6)[(Im)(4)Cu(4)(pdc)(4)Sr(H(2)O)(4)]·6H(2)O}(n) (1) and [Cu(2)(H(2)O)(2)(pdc)(2)Sr(H(2)O)(3)](n) (2) (H(3)pdc = 3,5-pyrazoledicarboxylic acid; Im = imidazole). The 1 : 1 : 1 : 5 reaction of SrCl(2)·6H(2)O, Cu(NO(3))(2)·3H(2)O, H(3)pdc and imidazole in H(2)O-EtOH at 120 °C under autogenous pressure gave 1. Complex 2 was obtained from the 1 : 1 : 1 H(3)pdc/Sr(OH)(2)·8H(2)O/Cu(NO(3))(2)·3H(2)O reaction mixture in H(2)O-EtOH under solvothermal conditions. Complex 1 can be described as a 2D grid-shaped network with the four Cu(II) ions in a saddle-like conformation. In complex 2, Sr(II) ions link metalloligands [Cu(2)(pdc)(2)(H(2)O)(2)](2-) to generate a 2D layer framework. Variable-temperature solid-state dc magnetic susceptibility studies have been performed in the temperature range 2.0-300 K for complexes 1 and 2. Antiferromagnetic Cu(II)···Cu(II) exchange interactions were found for both 1 and 2.