A novel zinc-organic framework, {[Zn3(tza)2(μ2-OH)2(H2O)2]·H2O}n (1) (H2tza = 1H-tetrazolate-5-acetic acid), was synthesized through an in situ generated tetrazole ligand under hydrothermal conditions. In compound 1, tza2− ligands and Zn2+ are interlinked to form 2D layers, which are further pillared through μ2-OH groups to generate a 3D framework. Thermogravimetric analysis and powder X-ray diffraction confirm that 1 has high thermal stability, pH stability and solvent stability. Catalytic studies show that 1 exhibits excellent catalytic ability for the cycloaddition of CO2 with epoxides under 50 °C and 0.1 MPa. Importantly, 1 can be reused at least six times. Furthermore, luminescence investigations indicate that 1 can serve as a recyclable luminescence sensor to efficiently detect Cr2O72−/CrO42−, and the detection limit can reach 10−6 mol L−1 and 4 × 10−6 mol L−1, respectively.

•Three 2D coordination polymers based on M2 clusters synthesized under solvothermal conditions.•Complex 1 shows metamagnetic behavior and complex 2 exists antiferromagnetic interaction.•The emission peak of complex 3 is caused by intraligand transition.Three new coordination polymers, [M2(CDA)2(EG)2]n (M = Co (1), Ni (2) and Zn (3), H2CDA = 1,1′-cyclopropane-dicarboxylic acid and EG = ethylene glycol), have been synthesized under solvothermal conditions and characterized via single-crystal X-ray diffraction, PXRD, EA, FT-IR, and TGA. Structural analysis indicates that metal ions form M2 clusters through μ2-O, which are further linked by CDA2− to generate 2D sheet structure with sql topology. The EG molecule functions not only as solvent but also as the chelate ligand. Magnetic measurements of complexes 1 and 2 have been carried out, which indicate the existence of metamagnetic behavior in complex 1 and antiferromagnetic interaction in complex 2. Furthermore, the fluorescence property of complex 3 was investigated.Three new coordination polymers have been synthesized under solvothermal conditions. Magnetic measurements indicated the existence of metamagnetic behavior in complex 1 and antiferromagnetic interaction in complex 2. Furthermore, the fluorescence property of complex 3 was investigated.Download high-res image (80KB)Download full-size image

Five new tetranuclear complexes based on an 8-hydroxyquinoline Schiff base derivative and the β-diketone coligand, [Ln4(acac)4L6(μ3-OH)2]·CH3CN·0.5CH2Cl2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5); HL = 5-(benzylidene)amino-8-hydroxyquinoline; acac = acetylacetonate) have been synthesized, and structurally and magnetically characterized. Complexes 1–5 have similar tetranuclear structures. Each LnIII ion is eight coordinated and its coordination polyhedra can be described as being in a distorted square-antiprismatic geometry. The magnetic studies reveal that 1 features the magnetocaloric effect (MCE) with the magnetic entropy change of −ΔSm(T) = 25.08 J kg−1 K−1 at 2 K for ΔH = 7 T, and 3 displays the slow magnetic relaxation behavior of Single Molecule Magnets (SMMs) with the anisotropic barrier of 86.20 K and the pre-exponential factor τ0 = 2.99 × 10−8 s.

Two series of dinuclear LnIII complexes, namely, [Ln(tfa)2(L)]2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)) and [Ln(tfa)2(L′)]2 (Ln = Gd (6), Tb (7), Dy (8), Ho (9), Er (10)) (tfa = trifluoroacetylacetonate, HL = 2-[[(4-methylphenyl)imino]methyl]-8-hydroxyquinoline and HL′ = 2-[[(4-ethylphenyl)imino]methyl]-8-hydroxyquinoline), were synthesized, and structurally and magnetically characterized. Measurements of alternating-current (ac) susceptibility revealed that complexes 3 and 8 display significant zero-field single-molecule magnetic (SMM) behaviors with barrier energies of Ueff/kB = 9.14 K, τ0 = 4.76 × 10−6 s and Ueff/kB = 17.50 K, τ0 = 3.96 × 10−6 s, respectively. The magnetic studies also revealed that 1 and 6 feature a magnetocaloric effect with magnetic entropy change of −ΔSm values for 1 and 6 of 19.72 J kg−1 K−1 and 19.37 J kg−1 K−1 at T = 2 K and ΔH = 7 T, respectively.

•A 2D Cobalt(II) compound (1) has been synthesized and characterized.•The crystal structure analysis showed that 1 contains a helical Co(II) chain.•1 exhibits weak ferromagnetic at low temperature.•1 showed slow magnetic relaxation behavior under 0 Oe direct current field.A new Co(II) complex, {[Co(MPA)(4,4′-bpy)(H2O)]·2H2O}n (1) (H2MPA = 4-methylphthalic acid, 4,4′-bpy = 4,4′-bipyridine), has been prepared under solvothermal condition and fully characterized. The X-ray crystallography test demonstrates that 1 exhibits two-dimensional (2D) layer structure in which the helical Co(II) chains linked by syn-anti carboxylate bridges are connected by 4,4′-bpy ligands. Weak ferromagnetism was observed on direct-current (dc) susceptibility due to the collective effects of the helical chain structure and antiferromagnetic couplings between Co(II) ions transmitted by μ2-1,3-carboxylate groups. Interestingly, slow magnetic relaxation was observed in 1 at liquid helium temperatures without an external dc field.Download high-res image (430KB)Download full-size image

Five tetranuclear rare-earth complexes, [RE4(dbm)4L6(μ3-OH)2] [HL = 5- (4-fluorobenzylidene)-8-hydroxylquinoline; dbm = 1,3-diphenyl-1,3-propanedione; RE = Y (1), Eu (2), Tb (3), Dy (4), Lu (5)], have been synthesized and completely characterized. The X-ray structural analyses show that each [RE4] complex is of typical butterfly or rhombus topology. Each REIII center exists in an eight-coordinated square-antiprism environment. Magnetic studies reveal that complex 4 displays single-molecule-magnet behavior below 10 K under a zero direct-current field, with an effective anisotropy barrier (ΔE/kB = 56 K). The fluorescence properties of complexes 1–5 were also investigated. Complexes 2–4 showed their characteristic peaks for the corresponding REIII center, while complexes 1 and 5 showed the same emission peaks with the ligand when they were excited at the same wavelength.

Nine dinuclear Ln(III) complexes, [Ln(dbm)2(L)]2 (Ln = Eu (1), Tb (2), Dy (3), Ho (4), Er (5)) and [Ln(dbm)2(L′)]2 (Ln = Tb (6), Dy (7), Ho (8), Er (9)) (dbm = 1,3-diphenyl-1,3-propanedione, HL = 2-[[(4-methoxy-phenyl)imino]methyl]-8-hydroxy-quinoline and HL′ = 2-[[(4-ethoxyphenyl)imino]methyl]-8-hydroxyquinoline) have been synthesized, and structurally and magnetically characterized. The nine complexes are all phenoxo-O bridged binuclear complexes, in which Ln1 and Ln1a are in an eight-coordinated environment bridged by two phenoxido oxygen atoms of two 8-hydroxyquinoline Schiff base ligands. Although complexes 3 and 7 have very similar structures, magnetic studies reveal that they exhibit different magnetic relaxation behaviors with the effective barriers (ΔE/kB) of 34.5 K for 3 and 67.6 K for 7. The dissimilar dynamic magnetic behaviors of 3 and 7 mostly result from the different electron-donating effect induced by the two alkoxy (–OCH3 and –OC2H5) of the 8-hydroxyquinoline Schiff base ligands. Meanwhile, for complexes 2, 5, 6 and 9, there are no observed magnetic relaxation behaviors under a zero dc field. In addition, the luminescence properties of 1, 2 and 6 were studied.

Seven dinuclear complexes based on 8-hydroxyquinoline Schiff base derivatives and β-diketone ligands, [RE2(hfac)4L2] (RE = Y (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6) and Lu (7); hfac− = hexafluoroacetylacetonate; HL = 2-[(4-chloro-phenylimino)-methyl]-8-hydroxyquinoline), have been synthesized, and structurally and magnetically characterized. Complexes 1–7 have similar dinuclear structures, in which each REIII ion is eight coordinated by two L− and two hfac− ligands in a distorted dodecahedron geometry. The luminescence spectra indicate that complex 3 exhibits characteristic TbIII ion luminescence, while 1 and 7 show HL ligand luminescence. The magnetic studies reveal that 2 features a magnetocaloric effect with the magnetic entropy change of −ΔSm = 16.83 J kg−1 K−1 at 2 K for ΔH = 8 T, and 4 displays slow magnetic relaxation behavior with the anisotropic barrier of 6.7 K and pre-exponential factor τ0 = 5.3 × 10−6 s.

Seven new tetranuclear rare earth (RE) complexes [RE4(acac)4L6(μ3-OH)2] (HL = 5-(4-fluorobenzylidene)-8-hydroxylquinoline; acac = acetylacetonate; RE = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Tm (6) and Lu (7)) have been synthesized and completely characterized. Complex 5 exhibits multiple zero-field slow magnetic relaxation processes typical of Single Molecule Magnets (SMMs). Two distinct slow magnetic relaxation processes, with effective energy barriers of Ueff = 48 K for the slow relaxation (SR) process and Ueff = 121 K for the fast relaxation (FR) process, are mainly attributed to the presence of two crystallographically independent Dy(III) sites. The magnetocaloric effect (MCE) was detected as −ΔSm(T) = 20.8 J kg−1 K−1 for complex 3. The fluorescence properties of complexes 1, 2, 4, 5 and 7 were also investigated. Complexes 2, 4 and 5 show the characteristic peaks for their corresponding RE(III) center, while complexes 1 and 7 show similar emission peaks to the Schiff base ligand when they are excited at the appropriate wavelength.

A new family of lanthanide complexes, [Ln2(dbm)4(OQ)2(CH3OH)2] (Ln = Nd (1), Tb (2), Dy (3), Ho (4); dbm = dibenzoylmethanate, OQ = 8-quinolinolate), and [Er2(dbm)4(OQ)2(CH3OH)]·CH3COCH3 (5) were synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–5 are μ-phenol bridged dinuclear complexes. For complexes 1–4, each LnIII ion is eight-coordinated with two bidentate dbm and two μ-phenol bridging OQ ligands and one methanol molecule. Complex 1 in the solid-state displays the typical emissions of the NdIII ions in the NIR region. Magnetic measurements were carried out on complexes 1–5. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 3. Fitting the dynamic magnetic data to the Arrhenius law gives the energy barrier ΔE/kB = 109.5 K and pre-exponential factor τ0 = 4.23 × 10−9 s under 3000 Oe dc field.

•Three dinuclear compounds, [Ln2(tfa)4L2] (Ln = Y(1), Tb (2)) and [Tb2(dbm)4L2·CH3CN·CH2Cl2] (3), have been synthesized and structurally characterized.•Magnetic study indicated that 2 shows SMMs behavior with the anisotropic barriers (ΔE/kB) of 1.51 K.•Magnetic study indicated that no χ″ ac signal is noticed for 3.Three dinuclear rare-earth complexes, [RE2(tfa)4L2] (RE = Y(1), Tb (2)) and [Tb2(dbm)4L2·CH3CN·CH2Cl2](3) (tfa = trifluoroacetylacetonate, dbm = dibenzoylmethane and HL = 2-[(4-bromophenyl)-imino]methyl]-8-hydroxyquinoline), have been synthesized and structurally characterized. Complexes 1–3 are phenoxo-O bridged dinuclear complexes, RE(III) ions are eight-coordinated with two bidentate β-diketonate and two μ2-O bridging 8-hydroxyquinoline Schiff base ligands. Magnetic studies reveal that 2 shows single-molecule-magnet behavior with the anisotropic barriers (ΔE/kB) of 1.18 K, while no out of-phase alternating-current (ac) signal is noticed for 3. The distinct magnetic behaviors of 2 and 3 are mainly due to the slightly different chemical environment around the center Tb(III) ions.Complexes 2 and 3 are all phenoxo-O bridged dinuclear complexes with similar structures, however, they have distinct magnetic behaviors. Complexe 2 shows single-molecule-magnet behavior with the anisotropic barriers (ΔE/kB) of 1.51 K, while no out of-phase alternating-current signal is noticed for 3. The distinct magnetic behaviors of 2 and 3 are mainly due to the slightly different chemical environment around the center Tb(III) ions.

•Two cobalt(II) complexes derived from azolate-carboxylic acid were synthesized and characterized.•Dominant antiferromagnetic interactions between Co2 + ions in them were found.Two cobalt(II) homometallic complexes, [Co2(HTDA)2(H2O)6·2H2O] (1) and {[Co3(TDA)2(H2O)8]·H2O}n(2) (H3TDA = 1H-1,2,3-triazole-4,5-dicarboxylic acid) have been synthesized and structurally characterized in detail. Single-crystal X-ray crystallographic study reveals that they crystallize in trigonal space group R-3 and orthorhombic space group Pna21, respectively. In 1, two Co2 + cations are bonded by two HTDA2 − ligands to generate a binuclear CoII unit, which can further be extended to a 3D supermolecular structure via the hydrogen bonds. At variance with 1, the nearest Co2 + cations of 2 are connected via TDA3 − ligands to form a 1D coordination polymer and can be further linked to each other to result in a 3D supermolecular framework through the hydrogen bonding interactions as well. The magnetic properties of them were studied in detail.Two cobalt(II) homometallic complexes derived from 1H-1,2,3-triazole-4,5-dicarboxylic acid were synthesized and fully characterized. The magnetic properties were studied in detail to determine the following magnetic parameters: g = 2.47, D = 36.85 cm− 1, zJ = − 0.61 cm− 1, and R = 0.9979 for 1; A + B = 9.79 cm3 K mol− 1, E1 = − 31.27 K, E2 = − 1.55 K and R = 0.9998 for 2, respectively, suggesting dominant antiferromagnetic interaction between Co2 + ions.

•A phenoxo-O bridged compound, [Dy2(dbm)4(L)2]2 (1), have been synthesized and structurally characterized.•Magnetic measurements indicated that slow relaxation of the magnetization was clearly observed in 1, typical of SMM behavior.•The dinuclear dysprosium compound 1 possesses excellent solvent stabilities.A dinuclear dysprosium compound, [Dy2(dbm)4L2]2(1) (Hdbm = 1,3-diphenyl-1,3-propanedione, HL = 2-[[(4-fluorophenyl)imino]methyl]-8-hydroxyquinoline), have been synthesized, structurally and magnetically characterized. The X-ray structural analysis exhibits that the compound 1 is phenoxo-O bridged binuclear compound, in which two DyIII ions are bridged by two phenoxido oxygen atoms of two 8-hydroxyquinoline Schiff base ligands. Each DyIII centers exhibit an eight-coordinated environment. Magnetic measurements indicated that slow relaxation of the magnetization was clearly observed in 1, typical of SMM behavior.A dinuclear dysprosium compound, [Dy2(dbm)4(L)2]2 (1) (dbm = 1,3-diphenyl-1,3-propanedione, L = 2-[[(4-fluorophenyl)imino]methyl]-8-hydroxyquinoline), have been synthesized, structurally and magnetically characterized. Magnetic measurements indicated that slow relaxation of the magnetization was clearly observed in 1, typical of SMM behavior.

New dinuclear lanthanide(III) complexes based on an 8-hydroxyquinoline Schiff base derivative and β-diketonate ligands, [Ln2(hfac)4(L)2] (Ln(III) = Gd (1), Tb (2), Dy (3), Ho (4), Er (5)), [Ln2(tfac)4(L)2] (Ln(III) = Gd (6), Tb (7), Dy (8), Ho (9)), and [Dy(bfac)4(L)2·C7H16] (10) (L = 2-[[(4-fluorophenyl)imino] methyl]-8-hydroxyquinoline, hfac = hexafluoroacetylacetonate, tfac = trifluoroacetylacetonate, and bfac = benzoyltrifluoroacetone), have been synthesized. The single-crystal X-ray diffraction data show that complexes 1–10 are phenoxo-O-bridged dinuclear complexes; each eight-coordinated center Ln(III) ion is in a slightly distorted dodecahedral geometry with two bidentate β-diketonate coligands and two μ2-O bridging 8-hydroxyquinoline Schiff base derivative ligands. The magnetic study reveals that 1 and 6 display cryogenic magnetic refrigeration properties, whereas complexes 3, 8, and 10 show different SMM behaviors with energy barriers of 6.77 K for 3, 19.83 K for 8, and 25.65 K for 10. Meanwhile, slow magnetic relaxation was observed in 7, while no out-of-phase alternating-current signals were found for 2. The different dynamic magnetic behaviors of two Tb2 complexes and the three Dy2 complexes mainly derive from the tiny crystal structure changes around the Ln(III) ions. It is also proved that the β-diketonate coligands can play an important role in modulating magnetic dynamics of the lanthanide 8-hydroxyquinoline Schiff base derivative system.

A new family of lanthanide complexes, [Ln2(hfac)4L2] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Lu (7); hfac = hexafluoroacetylacetonate, HL = 2-(2′-benzothiazole)-8-hydroxyquinoline), was synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–7 are isomorphous and crystallize in the monoclinic space group C2/c. In these dinuclear complexes, each LnШ ion is eight-coordinated with two bidentate hfac and two μ-phenol bridging L ligands. The TGA results show that the complexes have relatively high thermal stabilities. Complexes 1 and 3 show the characteristic transitions of the corresponding lanthanide ions with ligand-related emission peaks. Meanwhile, complexes 4 and 7 exhibit ligand-centered fluorescence at room temperature. Magnetic measurements were carried out on complexes 2–6. The magnetic study reveals that 2 displays a magnetocaloric effect, with a maximum −ΔSm value of 16.89 J K−1 kg−1 at 2 K for ΔH = 8 T. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 4. Fitting the dynamic magnetic data to the Arrhenius law gives an energy barrier ΔE/kB = 50.33 K and pre-exponential factor τ0 = 1.05 × 10−8 s.

A helix chain Dy3+ compound, [Dy(HNA)(NA)2(NO3)]n (1, HNA = nicotinic acid), was synthesized under solvothermal conditions and fully characterized. The absolute configurations of the enantiomers in P61 and P65 space groups are characterized by single crystal X-ray diffraction and circular dichroism (CD). Magnetic studies reveal that compound 1 exhibits ferromagnetic interaction and slow magnetic relaxation at low temperatures with the energy barrier of 37 K under 900 Oe dc field.

•A novel bi-triazole ligand was prepared and characterized.•Three copper-based coordination polymers were structurally characterized.•These compounds exhibit different EPR signals.Three Cu(II) coordination polymers: [Cu(XL)(NO3)2]n (1), {[Cu(XL)(4,4′-bpy)(NO3)2]·CH3CN}n (1a) and {[Cu(XL)3](NO3)2·3.5H2O}n (2) have been synthesized mainly based on a novel bi-triazole ligand N,N′-bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxdiimide bi(1,2,4-triazole) (XL) and characterized by X-ray crystallography, EPR spectra, elemental analyses, FT-IR spectra and PXRD patterns. Structure analyses reveal that compounds 1 and 1a exhibit 1D chains, and compound 2 features a 2D cationic framework. Additionally, the Cu(II) ions with various coordination environment in compounds 1, 1a and 2 exhibit different EPR properties.Three Cu(II) coordination polymers have been synthesized mainly based on a novel bi-triazole ligand. In these compounds, the Cu(II) ions with various coordination environments exhibit different EPR properties.

•Two new pyridine polycarboxylic acid complexes are obtained by hydrothermal syntheses.•The complexes are extended to high-dimensional networks by covalent bonds.•The complexes reveal different network structures.•The metal ions of the complexes show antiferromagnetic interactions.Two new complexes based on pyridine-2,3,5,6-tetracarboxylic acid(H4pdtc) as ligand, {[Co2(pdtc)(H2O)4] · H2O}n (1) and {Mn2(pdtc)(H2O)4}n (2), have been obtained by hydrothermal syntheses and characterized by IR, elemental analysis, X-ray diffraction single crystal structure analysis, PXRD, thermal gravimetric analysis, and magnetic measurements. Complex 1 is 3D coordination polymer and complex 2 belongs to 2D grid structure by covalent bonds. In 1 and 2, the metal ions show antiferromagnetic interactions.Two complexes based on pyridine-2,3,5,6-tetracarboxylic acid are prepared. Their structures and properties have been investigated. The pyridine-2,3,5,6-tetracarboxylic acid contains rich coordination sites, which can adopt a variety of coordination modes in the structure. Furthermore, the most interesting thing is that, the oxygen atoms and nitrogen atom in the same pdtc4 − anion are all coordinated with Mn(II) ions, which is reported the first time.

•A new 3D framework based on {Co6} cluster has been synthesized.•Framework 1 showed an 8-connected bcu topology.•Two coordination modes of the trz− ligand are observed in 1.•Compound 1 displays high thermal stability.•Compound 1 exhibits antiferromagnetic interaction among the CoII spin carries.A new 3D framework 1 based on {Co6} cluster as node was successfully synthesized and fully characterized, which showed an 8-connected bcu topology with the Schläfli symbol of {424,64}. Furthermore, the thermal stability and magnetic property reveal that 1 displays high thermal stability and antiferromagnetic interaction among the CoII spin carries.A new 3D framework 1 based on {Co6} cluster as node was successfully synthesized, which showed an 8-connected bcu topology. The thermal stability and magnetic property reveal that 1 display high thermal stability and antiferromagnetic interaction among the CoII spin carries.

Two three-dimensional polymeric Tb(III) and Yb(III) frameworks, namely, {[Tb3(Hptc)(ptc)(pdc)(H2O)6]·2H2O}n (1) and {[Yb2(ptc)(ox)(H2O)5]·7H2O}n (2) (H4ptc = pyridine-2,3,5,6-tetracarboxylic acid, H2pdc = pyridine-3,5-dicarboxylic acid, ox = oxalate), have been synthesized by a hydrothermal method and characterized by infrared spectra, elemental analysis, powder X-ray diffraction, thermogravimetric analysis, and single-crystal X-ray diffraction. Framework 1 shows an interesting three-dimensional (8,8)-connected net with a Schläfli symbol of (33·418·55·62)2(36·414·57·6), while 2 exhibits an unusual (4,8)-connected sqc21 net with a Schläfli symbol of (32·42·52)(34·48·512·64). Luminescence studies of 1 reveal that the luminescence intensity increases when the framework is dehydrated.

Triple core–shell structures in the Cu24Gd6 and Cu24Dy6 clusters were first observed and structurally characterized. The magnetic investigations reveal that Cu24Gd6 possesses the significant magnetic entropy change (−ΔSm) of 21.2 J kg−1 K−1 for ΔH = 7 T, and a slow magnetization relaxation is observed in Cu24Dy6.

Two novel tetra- and deca-nuclear dysprosium compounds, namely, [Dy4(μ3-OH)2(L)10(bipy)2(H2O)2]n (1) and {[Dy10(μ3-OH)8(L)22(bipy)2(H2O)2]·5H2O}n (2) (L = 3-fluoro-4-(trifluoromethyl)benzoic acid; bipy = 2,2′-bipyridine), have been successfully obtained by hydrothermal reaction at different pH values. The solid state structures of 1 and 2 were established by the single crystal X-ray diffraction technique, and both of them exhibit complicated 1D chains with [Dy4] (1) and [Dy10] (2) cluster units, respectively. Adjacent [Dy4] in 1 and [Dy10] in 2 are connected by two bridging carboxylate groups in the η1:η1:μ2 mode. Magnetic studies reveal that they exhibit different magnetic relaxation behaviors with the energy barrier of 23.6 K for 1 and 3.2 K for 2. Interestingly, the large divergence in both the structures and magnetic properties for 1 and 2 only originated from the different pH values in preparing them.

•Four new Ag-containing complexes are obtained.•The complexes are based on nitrogenous aromatic heterocyclic carboxylic acids.•The complexes are extended to high-dimensional supramolecular networks.•The complexes exhibit fluorescent properties in the solid state.Four new coordination complexes with silver(I) ions and nitrogenous aromatic heterocyclic carboxylic ligands, namely [Ag4(pztc)(phen)4] · 8H2O (1), {[Ag4(pztc)(bpe)3] · 5H2O}n (2), [Ag4(Hmptc)2(4,4′-bpy)3] · 4.5H2O (3), and [Ag2(H2mptc)2(2,2′-bpy)2] (4) (H4pztc = pyrazine-2,3,5,6-tetracarboxylic acid, H3mptc = 6-methyl-2,3,5-pyridine-tricarboxylic acid, phen = 1,10-phenanthroline, bpe = trans-1,2-bis(4-pyridyl)ethylene, 4,4′-bpy = 4,4′-bipyridine, 2,2′-bpy = 2,2′-bipyridine), have been synthesized by the self-assembly reactions and characterized by X-ray diffraction single crystal structure analysis, elemental analysis, IR, PXRD, fluorescence and thermal analysis. In 1, four crystallographically independent silver(I) atoms are found to coordinate with only one pztc4 − ligand. Complex 2 is a 2D grid structure. Complexes 3 and 4 are extended from 0D to 2D or 1D by the Ag⋯O interactions.Four Ag-containing complexes constructed from mixed ligand of pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) or 6-methyl-2,3,5-pyridinetricarboxylic acid (H3mptc) and N-donor ligands are designed and synthesized. Notably, H2O/ethanol/acetonitrile conditions have been the preferred method employed by our group to enhance the solubility of the silver carboxylates, which provide a new way of Ag complex synthesis.

•Two novel coordination polymers have been synthesized and characterized.•Coordination polymer 1 contains a rarely reported 1D CuII chain.•Non-coordinated groups of the ligands greatly influence the formations of 1 and 2.•1 and 2 exhibit very different antiferromagnetic dominant behaviors.Two coordination polymers: {[Cu3(MPA)2(trz)(μ3-OH)(H2O)]∙2H2O}n (1) and {[Cu6(NPA)4(trz)2(μ3-OH)2(H2O)2]∙H2O}n (2) (H2MPA = 4-methylphthalic acid, Htrz = 1H-1,2,4-triazole, H2NPA = 4-nitrophthalic acid) were synthesized under identical reaction conditions by changing the non-coordinated methyl group to nitro group of phthalic acid and characterized by elemental analysis, powder X-ray diffraction (PXRD), IR spectrum, thermo-gravimetric (TG) analysis and single crystal X-ray diffraction. Direct-current magnetic susceptibility measurements reveal that relatively strong antiferromagnetic couplings between the CuII spin carriers exist in 1 and 2.By employing the mixed-linker synthetic strategy, two novel two-dimensional (2D) coordination polymers (1 and 2) were obtained. 1 and 2 exhibit strong antiferromagnetic interactions between CuII carriers.

•Five complexes based on 5-nitro-quinoline-8-yl acetate were obtained.•The complexes reveal different network structures.•The complexes exhibit interesting fluorescent properties in the solid state.Five new complexes of Cd(II) and Zn(II), [M(C9H5N2O3)2(CH3OH)2] (1, 2) and [M(C9H5N2O3)2(C2H8N2)] (3, 4) (M = Zn(II) and Cd(II)) and [Zn(C9H5N2O3)2(C10H8N2)] (5), have been prepared by the slowly release methods of 5-nitro-8-hydroxyquinoline from 5-nitro-quinoline-8-yl acetate and characterized by elemental analysis, IR, thermal gravimetric analysis, fluorescence measurement and single crystal X-ray diffraction analysis. All the complexes are mononuclear and show excellent luminescence properties in the solid state at room temperature.

Three metal–organic frameworks (MOFs) with d10 metal ions, namely, {[Zn3(TDA)2(bpy)3]·(bpy)·10.5H2O}n (1), {[Zn3(TDA)2(azopy)2.5(H2O)]·4H2O}n (2) and {[Cd2K3(TDA)(HTDA)2(H2O)4]}n (3) (KH2TDA = potassium 1H-1,2,3-triazole-4,5-dicarboxylic acid, bpy = 4,4′-bipridine, azopy = 4,4′-azobispridine), have been successfully synthesized from KH2TDA with the aid of three different length-controllable auxiliary ligands and characterized by infrared spectra, elemental analysis, thermogravimetric analysis, powder X-ray diffraction and single-crystal X-ray diffraction. MOF 1 shows an interesting three-dimensional (3D) (3,4,4,4)-connected KAVGAQ framework with a Schläfli symbol of {63}2{64·102}{64·82}2, which can be extended by 2D layers and bpy pillars. MOFs 2 and 3 also display 3D framework structures, corresponding to a 6-connected {44·611} net and a (6,12)-connected {312·430·520·64}{36·48·5} net, respectively. Moreover, a novel coordination mode of H3TDA is observed in 3. The luminescence properties of 1–3 are investigated.

Six novel three-dimensional (3D) lanthanide metal–organic frameworks (LnMOFs), {[Ln2(ispc)3(H2O)3]·mH2O}n (Ln = Pr (1, m = 5); Eu (2, m = 5); Gd (3, m = 4); Tb (4, m = 5); Dy (5, m = 5) and Ho (6, m = 4)), ispc = 3-(4-carboxyphenylsulfonyloxy)-4-methoxybenzoic anion) have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction revealed they are isostructural and crystallize in the triclinic crystal system, space group P. The investigations on luminescent properties and lifetimes of 2 (EuIII), 4 (TbIII), and 5 (DyIII) exhibit characteristic emissions of EuIII, TbIII and DyIII ions and the corresponding luminescent lifetimes are 0.14 ms, 9.93 μs and 1.25 ms, respectively. The different luminescent intensities and lifetimes among them were further discussed. Furthermore, magnetic studies of 1–6 reveal that 3–6 exhibit ferromagnetic coupling, and 5 (DyIII) exhibits remarkably slow magnetic relaxation behavior with the energy barrier ΔE/kB = 49.2 K.

Three novel coordination polymers, {[cis-K2Zn2Mn(μ7-pdtc)2(H2O)10]·H2O}n (1), {[cis-K2Zn3(μ7-pdtc)2(H2O)10]·0.5H2O}n (2) and [trans-K2Zn3(μ5-pdtc)2(H2O)12]n (3), were synthesized by the self-assembly of potassium pyridine-2,3,5,6-tetracarboxylate (K4pdtc) with metal salts. 1 is the first Zn/Mn/K heterotrimetallic complex with H4pdtc. 1 and 2 have 3D network structures, while 3 is a 2D coordination polymer, which are due to the different bonding modes of H4pdtc with K(I) and metal(II) ions. The fluorescence spectroscopy measurements reveal that strong photo-luminescent characteristics exhibit in 1–3 in aqueous solution at room temperature.Self-assembly of pyridine-2,3,5,6-tetracarboxylic acid(H4pdtc) with metal salts gave three novel coordination polymers, {[cis-K2Zn2Mn(μ7-pdtc)2(H2O)10]·H2O}n (1), {[cis-K2Zn3(μ7-pdtc)2(H2O)10]·0.5H2O}n (2) and [trans-K2Zn3(μ5-pdtc)2(H2O)12]n (3). 1 is the first Zn/Mn/K heterotrimetallic complex. The structure of 2 is similar to that of 1. 3 is a 2D coordination polymer. Strong photo-luminescent characteristics exhibit in 1–3.Highlights► Three polymers with H4pdtc have been synthesized and characterized. 1 is the first Zn/Mn/K heterotrimetallic complex. ► The H4pdtc molecules show 7-coordinated modes in 1–2 and a 5-coordinated mode in 3. ► Strong photo-luminescent characteristics exhibit in 1–3 in aqueous solution at room temperature.

The thiosemicarbazide and hydrazide Cu(II) complexes, [Cu3L21(py)4Cl2] (1), [Cu(HL2)py] (2) and [Cu(HL3)py] (3), (H2L1 = 1-picolinoylthiosemicarbazide, H3L2 = N′-(2-hydroxybenzylidene)-3-hydroxy-2-naphthohydrazide, H3L3 = 2-hydroxy-N′-((2-hydroxy-naphthalen-1-yl)methylene)benzohydrazide) have been prepared and characterized through physicochemical and spectroscopic methods as well as X-ray crystallography. Complex 1 has a centrosymmetric structure with –N–N– bridged Cu3 skeleton. Neighboring molecules are linked into a 3D supermolecular framework by π–π stacking interactions, N–H···Cl and C–H···Cl hydrogen bonds. Complexes 2 and 3 have similar planar structures but different dimers formed by concomitant Cu···N and Cu···O interactions, respectively. Solvent accessible voids with a volume of 391 Å3 are included in the structure of complex 2, indicating that this complex is a potential host candidate. Thermogravimetric analysis shows that the three complexes are stable up to 100 °C.

Four coordination polymers with lanthanide ions and the novel ligand 6-methyl-2,3,5-pyridinetricarboxylic acid (H3mptc), {[Ln(mptc)(H2O)4]·3H2O}n, [Ln = Pr (1), Nd (2), Sm (3), Tb (4)], have been synthesized by the self-assembly reaction of potassium 6-methyl-2,3,5-pyridinetricarboxylate (K3mptc) and rare earth salts in aqueous solution. The complexes were characterized by X-ray diffraction single crystal structure analysis, elemental analysis, IR, fluorescence and thermal analysis. The four coordination polymers are isotypics and crystallize in the monoclinic system with the P21/n space group. The Ln(III) ions are coordinated by three carboxylate groups with different coordination modes and link to form an infinite two-dimensional (2D) polymer. Infinite T6(2) water tapes containing puckered-boat hexameric water rings exist in the space between the metal crystal building layers. The T6(2) water tapes self-assemble into novel 2D L6(5)14(8) water layers through (H2O)2 dimers between adjacent water tapes.

A C3-symmetric terbium complex {[Tb2(pztc)3]⋅6.5H2O}n (1) (pztc = pyrazine-2,3,5,6-tetracarboxylate), with hexagonal cavities, has been synthesized under hydrothermal conditions and characterized by X-ray single-crystal diffraction, elemental analysis, IR, TGA, PXRD and fluorescence measurements. The layer structure of the 2D complex is just like the structure of graphite. The most appealing structure is that a hexagonal C3-symmetric (H2O)7 guest fits into the hexagonal C3-symmetric terbium complex cavity very fitly. Furthermore, when the water clusters are driven off, the framework does not collapse and the luminescence intensity increases.A hexagonal C3-symmetric terbium complex {[Tb2(pztc)3]⋅6.5H2O}n (1) (pztc = pyrazine-2,3,5,6-tetracarboxylate), with hexagonal cavities, has been synthesized under hydrothermal conditions. The layer structure of the infinite 2D complex is just like the structure of the graphite. The most appealing structure is that a hexagonal C3-symmetric (H2O)7 guest fits into the hexagonal C3-symmetric terbium complex cavity very fitly.

Four novel 3D coordination polymers, {[K3Cu2(H0.5pdtc)2 (H2O)6]·(H2O)2}n (1), {[trans-K2Mn3(pdtc)2 (H2O)11]·H2O}n (2), {[trans-K2Mn3(pdtc)2 (H2O)10]·H2O}n (3) and {[cis-K2Cu2Mn(pdtc)2 (H2O)10]·H2O}n (4), were synthesized by the self-assembly of potassium pyridine-2,3,5,6-tetracarboxylate (K4pdtc) with metal salts. All of them contain infinite 1D stepwise chain. Notably, 2–4 have 2D network structures depending on the trans- and cis- hexacoordinated Mn(II) acting as connecters between the chains. Then, they further assemble into 3D or twin-plane structures by K(I) ions. 4 is the first Cu/Mn/K heterotrimetallic complex with H4pdtc. The (H2O)6 clusters in 1 arranged stepwise along the complex chains owing to the host chains' template effect. The variable–temperature magnetic measurements reveal that weak antiferromagnetic interactions exist in complexes 1 and 4.Self-assembly of pyridine-2,3,5,6-tetracarboxylic acid(H4pdtc) with metal salts gave four 3D coordination polymers, {[K3Cu2(H0.5pdtc)2(H2O)6]·(H2O)2}n (1), {[trans-K2Mn3(pdtc)2 (H2O)11]·H2O}n (2), {[trans-K2Mn3(pdtc)2(H2O)10]·H2O}n (3), and {[cis-K2Cu2Mn(pdtc)2(H2O)10]·H2O}n (4). They all contain stepwise chains. 2-4 are connected into 2D layers through trans-/ cis-[Mn(H2O)4]2+ units. 4 is the first Cu/Mn/K heterotrimetallic complex with H4pdtc.

Pyrazine-2,3,5,6-tetracarboxylic acid (H4pztc) reacted with Ni(ClO4)2·6H2O and 1,10-phenanthroline (phen) in aqueous solutions to form two different complexes, [Ni(H2pztc)(phen)H2O]·H2O (1), [Ni(phen)3](H2pztc)·10.5H2O (2), under hydrothermal conditions and at room temperature respectively. In 1, Ni(II) ion is coordinated by tridentate chelated H2pztc2−. The carboxyl and carboxylate groups of H2pztc2− are roughly coplanar with the pyrazine ring and form intramolecular hydrogen bonds. While in 2, H2pztc2− remains uncoordinated, the carboxyl and carboxylate groups of H2pztc2− are out of plane of the pyrazine ring and do not form intramolecular hydrogen bonds. H2pztc2− and water molecules form negatively-charged channels and the channels are filled with [Ni(phen)3]2+ in the 3D supramolecular structure of 2. In addition, a novel water tape is present in 2.

Two new 1D slide-fastener-like coordination polymers {[Mn2(pztc)(phen)2(H2O)2]·4H2O}n (1) and {[Mn2(pztc)(bpy)2(H2O)2]·2H2O}n (2) have been synthesized by the reactions of pyrazine-2,3,5,6-tetracarboxylic acid (pztcH4) and Mn(OAc)2·4H2O in the presence of 1,10-phenanthroline (phen) or 2,2′-bipyridine (bpy) under hydrothermal conditions and characterized by elemental analyses, FT-IR, TGA and X-ray diffraction. In complex 1 and 2, metal ions are bridged by pyrazine-2,3,5,6-tetracarboxylate, coordinating in a hexadentate manner, so forming 1D polymeric chains. The remaining coordination sites of the metal ions are occupied by one O atom of water molecule and two N atoms of the terminal ligand (phen or bpy). IR spectra and thermal analysis data are in agreement with the crystal structure.

Two thiocyanate-bridged hetero-pentanuclear complexes (CuL)3[Mn(NCS)5]2(1) and (NiL)3[Mn(NCS)5]2(2) have been successfully synthesized and characterized by X-ray single crystal diffraction, elemental analysis, IR, TGA and magnetic measurements. (L = N-dl-5,7,7,12,14,14-hexamethyl-1,4,8,11-tetraazacyclotetradeca-4,11-diene). Single crystal structure analysis indicates that complex 1 and 2 have similar structures in which the Mn(II) atom is five-coordinated in a trigonal bipyramidal geometry by five N atoms from five thiocyanate ligands. The Cu(II) and Ni(II) both show two different coordination environments, square pyramidal and distorted octahedron. Three Cu(II) (or Ni(II)) ions and two Mn(II) ions are bridged by the end-to-end thiocyanate ligands to form pentanuclear entities. The pentanuclear entities are further linked to 3D framework by the hydrogen bonds. The variable-temperature magnetic measurements for 1 indicated weak antiferromagnetic interaction between the Cu(II) and Mn(II) ions.The thiocyanate-bridged pentanuclear (CuL)3[Mn(NCS)5]2(1) and (NiL)3[Mn(NCS)5]2(2) are isomorphic, and Mn(II) is coordinated by five N atoms from five thiocyanate ligands in a trigonal bipyramidal geometry, which is a novel coordination mode and observed in the complexes for the first time.

A new complex [Co(H2pztc)(bpy)H2O] (H4pztc = pyrazine-2,3,5,6-tetracarboxylic acid, bpy = 2,2′-bipyridine) has been synthesized by hydrothermal reactions of Co(NO3)2 · 6H2O with H4pztc and bpy and characterized by IR and X-ray diffraction single crystal structure analysis. It belongs to monoclinic system, P21/c space group with a = 13.454(2) Å, b = 12.939(2) Å, c = 11.4993(19) Å, α = 90°, β = 111.640(3)°, γ = 90°. This complex is assembled into 3D supramolecular architecture by hydrogen bonds (O–H···O, C–H···O).

Seven dinuclear complexes based on 8-hydroxyquinoline Schiff base derivatives and β-diketone ligands, [RE2(hfac)4L2] (RE = Y (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6) and Lu (7); hfac− = hexafluoroacetylacetonate; HL = 2-[(4-chloro-phenylimino)-methyl]-8-hydroxyquinoline), have been synthesized, and structurally and magnetically characterized. Complexes 1–7 have similar dinuclear structures, in which each REIII ion is eight coordinated by two L− and two hfac− ligands in a distorted dodecahedron geometry. The luminescence spectra indicate that complex 3 exhibits characteristic TbIII ion luminescence, while 1 and 7 show HL ligand luminescence. The magnetic studies reveal that 2 features a magnetocaloric effect with the magnetic entropy change of −ΔSm = 16.83 J kg−1 K−1 at 2 K for ΔH = 8 T, and 4 displays slow magnetic relaxation behavior with the anisotropic barrier of 6.7 K and pre-exponential factor τ0 = 5.3 × 10−6 s.

Nine dinuclear Ln(III) complexes, [Ln(dbm)2(L)]2 (Ln = Eu (1), Tb (2), Dy (3), Ho (4), Er (5)) and [Ln(dbm)2(L′)]2 (Ln = Tb (6), Dy (7), Ho (8), Er (9)) (dbm = 1,3-diphenyl-1,3-propanedione, HL = 2-[[(4-methoxy-phenyl)imino]methyl]-8-hydroxy-quinoline and HL′ = 2-[[(4-ethoxyphenyl)imino]methyl]-8-hydroxyquinoline) have been synthesized, and structurally and magnetically characterized. The nine complexes are all phenoxo-O bridged binuclear complexes, in which Ln1 and Ln1a are in an eight-coordinated environment bridged by two phenoxido oxygen atoms of two 8-hydroxyquinoline Schiff base ligands. Although complexes 3 and 7 have very similar structures, magnetic studies reveal that they exhibit different magnetic relaxation behaviors with the effective barriers (ΔE/kB) of 34.5 K for 3 and 67.6 K for 7. The dissimilar dynamic magnetic behaviors of 3 and 7 mostly result from the different electron-donating effect induced by the two alkoxy (–OCH3 and –OC2H5) of the 8-hydroxyquinoline Schiff base ligands. Meanwhile, for complexes 2, 5, 6 and 9, there are no observed magnetic relaxation behaviors under a zero dc field. In addition, the luminescence properties of 1, 2 and 6 were studied.

Seven new tetranuclear rare earth (RE) complexes [RE4(acac)4L6(μ3-OH)2] (HL = 5-(4-fluorobenzylidene)-8-hydroxylquinoline; acac = acetylacetonate; RE = Y (1), Eu (2), Gd (3), Tb (4), Dy (5), Tm (6) and Lu (7)) have been synthesized and completely characterized. Complex 5 exhibits multiple zero-field slow magnetic relaxation processes typical of Single Molecule Magnets (SMMs). Two distinct slow magnetic relaxation processes, with effective energy barriers of Ueff = 48 K for the slow relaxation (SR) process and Ueff = 121 K for the fast relaxation (FR) process, are mainly attributed to the presence of two crystallographically independent Dy(III) sites. The magnetocaloric effect (MCE) was detected as −ΔSm(T) = 20.8 J kg−1 K−1 for complex 3. The fluorescence properties of complexes 1, 2, 4, 5 and 7 were also investigated. Complexes 2, 4 and 5 show the characteristic peaks for their corresponding RE(III) center, while complexes 1 and 7 show similar emission peaks to the Schiff base ligand when they are excited at the appropriate wavelength.

A helix chain Dy3+ compound, [Dy(HNA)(NA)2(NO3)]n (1, HNA = nicotinic acid), was synthesized under solvothermal conditions and fully characterized. The absolute configurations of the enantiomers in P61 and P65 space groups are characterized by single crystal X-ray diffraction and circular dichroism (CD). Magnetic studies reveal that compound 1 exhibits ferromagnetic interaction and slow magnetic relaxation at low temperatures with the energy barrier of 37 K under 900 Oe dc field.

Six novel three-dimensional (3D) lanthanide metal–organic frameworks (LnMOFs), {[Ln2(ispc)3(H2O)3]·mH2O}n (Ln = Pr (1, m = 5); Eu (2, m = 5); Gd (3, m = 4); Tb (4, m = 5); Dy (5, m = 5) and Ho (6, m = 4)), ispc = 3-(4-carboxyphenylsulfonyloxy)-4-methoxybenzoic anion) have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction revealed they are isostructural and crystallize in the triclinic crystal system, space group P. The investigations on luminescent properties and lifetimes of 2 (EuIII), 4 (TbIII), and 5 (DyIII) exhibit characteristic emissions of EuIII, TbIII and DyIII ions and the corresponding luminescent lifetimes are 0.14 ms, 9.93 μs and 1.25 ms, respectively. The different luminescent intensities and lifetimes among them were further discussed. Furthermore, magnetic studies of 1–6 reveal that 3–6 exhibit ferromagnetic coupling, and 5 (DyIII) exhibits remarkably slow magnetic relaxation behavior with the energy barrier ΔE/kB = 49.2 K.

Two novel tetra- and deca-nuclear dysprosium compounds, namely, [Dy4(μ3-OH)2(L)10(bipy)2(H2O)2]n (1) and {[Dy10(μ3-OH)8(L)22(bipy)2(H2O)2]·5H2O}n (2) (L = 3-fluoro-4-(trifluoromethyl)benzoic acid; bipy = 2,2′-bipyridine), have been successfully obtained by hydrothermal reaction at different pH values. The solid state structures of 1 and 2 were established by the single crystal X-ray diffraction technique, and both of them exhibit complicated 1D chains with [Dy4] (1) and [Dy10] (2) cluster units, respectively. Adjacent [Dy4] in 1 and [Dy10] in 2 are connected by two bridging carboxylate groups in the η1:η1:μ2 mode. Magnetic studies reveal that they exhibit different magnetic relaxation behaviors with the energy barrier of 23.6 K for 1 and 3.2 K for 2. Interestingly, the large divergence in both the structures and magnetic properties for 1 and 2 only originated from the different pH values in preparing them.

Triple core–shell structures in the Cu24Gd6 and Cu24Dy6 clusters were first observed and structurally characterized. The magnetic investigations reveal that Cu24Gd6 possesses the significant magnetic entropy change (−ΔSm) of 21.2 J kg−1 K−1 for ΔH = 7 T, and a slow magnetization relaxation is observed in Cu24Dy6.

A new family of lanthanide complexes, [Ln2(hfac)4L2] (Ln = Eu (1), Gd (2), Tb (3), Dy (4), Ho (5), Er (6), Lu (7); hfac = hexafluoroacetylacetonate, HL = 2-(2′-benzothiazole)-8-hydroxyquinoline), was synthesized and characterized using single-crystal X-ray diffraction, elemental analysis (EA), thermal gravimetric analysis (TGA), powder X-ray diffraction (PXRD) and UV-vis spectra. X-ray crystallographic analyses reveal that 1–7 are isomorphous and crystallize in the monoclinic space group C2/c. In these dinuclear complexes, each LnШ ion is eight-coordinated with two bidentate hfac and two μ-phenol bridging L ligands. The TGA results show that the complexes have relatively high thermal stabilities. Complexes 1 and 3 show the characteristic transitions of the corresponding lanthanide ions with ligand-related emission peaks. Meanwhile, complexes 4 and 7 exhibit ligand-centered fluorescence at room temperature. Magnetic measurements were carried out on complexes 2–6. The magnetic study reveals that 2 displays a magnetocaloric effect, with a maximum −ΔSm value of 16.89 J K−1 kg−1 at 2 K for ΔH = 8 T. Dynamic magnetic studies reveal single-molecule magnet (SMM) behavior for complex 4. Fitting the dynamic magnetic data to the Arrhenius law gives an energy barrier ΔE/kB = 50.33 K and pre-exponential factor τ0 = 1.05 × 10−8 s.

Three dinuclear Dy(III) complexes, [Dy2(tfa)4L2] (1), [Dy2(TTA)4L2] (2) and [Dy2(dbm)4L2·2CH3CN·0.5H2O] (3) (tfa = trifluoroacetylacetonate, TTA = 2-thenoyltrifluoroacetone, dbm = dibenzoylmethane and HL = 2-[((4-bromophenyl)-imino)methyl]-8-hydroxyquinoline, have been synthesized, and structurally and magnetically characterized. The Dy(III) ions are eight-coordinated with two bidentate β-diketonate and two μ2-O bridging 8-hydroxyquinoline Schiff base ligands. Magnetic studies reveal that 1–3 exhibit different magnetic relaxation behaviors with the anisotropic barriers of 9.61 K (1), 54.81 K (2) and 30.98 K (3), respectively. The different magnetic relaxation behaviors of the three Dy2 complexes originate from the different chemical environments of the central Dy3+ ions with different β-diketonate coligands.

Five new tetranuclear complexes based on an 8-hydroxyquinoline Schiff base derivative and the β-diketone coligand, [Ln4(acac)4L6(μ3-OH)2]·CH3CN·0.5CH2Cl2 (Ln = Gd (1), Tb (2), Dy (3), Ho (4) and Er (5); HL = 5-(benzylidene)amino-8-hydroxyquinoline; acac = acetylacetonate) have been synthesized, and structurally and magnetically characterized. Complexes 1–5 have similar tetranuclear structures. Each LnIII ion is eight coordinated and its coordination polyhedra can be described as being in a distorted square-antiprismatic geometry. The magnetic studies reveal that 1 features the magnetocaloric effect (MCE) with the magnetic entropy change of −ΔSm(T) = 25.08 J kg−1 K−1 at 2 K for ΔH = 7 T, and 3 displays the slow magnetic relaxation behavior of Single Molecule Magnets (SMMs) with the anisotropic barrier of 86.20 K and the pre-exponential factor τ0 = 2.99 × 10−8 s.