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A bipyridyl-based Mn2+-organic framework was synthesized. Activated Mn-MOF-1 could serve as an efficient heterogeneous catalyst for the cycloaddition of CO2 with epoxides and Knoevenagel condensation reactions.

A new family of isostructural 3d–4f heterometallic metal–organic frameworks (HMOFs), [Zn3EuxTb2−x(TZI)4(DMA)5(H2O)3]·4DMA [x = 0 (1), 0.3 (2), 0.6 (3), 0.9 (4), 1 (5), 1.2 (6), 1.5 (7), 1.8 (8), 2 (9)], has been synthesized using the 5-(4-(tetrazol-5-yl) phenyl)isophthalic acid (H3TZI) ligand, LnIII ions and ZnII ions under solvothermal conditions. All HMOFs exhibit a (3,3,4,5,5)-connected 63·63(42·62·82)(4·65·8)(4·66·83) topology, which features three different types of motifs: one is a mononuclear ZnII ion and the other two motifs are binuclear [Zn(COO)3Ln] clusters. The adsorption experiments indicate that Zn3Tb2 (1) could efficiently remove almost all I2 from cyclohexane solution after 12 h and also showed better adsorption towards neutral red (NR) dye (adsorption: only the Zn3Tb2 (1) was taken as one representative). Simultaneously, the luminescence sensing showed that Zn3Tb2 (1) and Zn3Eu2 (9) have excellent response and sensitivity towards pollutants such as Fe3+ ions and 2,4,6-trinitrophenol (TNP) with high selectivity and a fairly low limit of detection through luminescence quenching effect. Moreover, seven trimetallic-doped HMOFs 2–8 analogues of Zn3Ln2 (single) HMOFs were designed and prepared, showing different changes of luminescent color. More interestingly, Zn3Eu1.5Tb0.5 (7) with white-light emission was fabricated by doping relative concentrations of Eu3+ and Tb3+ ions. To the best of our knowledge, Zn3Eu1.5Tb0.5 (7) represents a novel kind of heterometallic Zn3Ln2 HMOFs with white-light emission. It could be deduced that the excellent characteristics, namely strong typical luminescence emission of ZnII and LnIII ions, microporous channels, active open metal sites (tetra-coordinated ZnII–metal sites), and uncoordinated carboxylate O atoms and uncoordinated tetrazolate N atoms, made the above HMOFs an ideal platform for adsorption, luminescence sensing, and white-light emission. More significantly, these HMOFs are the first reported Zn–Ln heterometallic materials with the H3TZI ligand.

Seven new water-soluble chiral/achiral SOD-mimicking metal complexes: NaK[Mn(R-L1)(C2H5OH)4] (Mn-1a), NaK[Mn(S-L1)(C2H5OH)4] (Mn-1b), NaK[Co(R-L1)]·3H2O (Co-2a), NaK[Co(S-L1)]·3H2O (Co-2b), NaK[(VO)(R-L1)(OH)]·5H2O (V-3a), NaK[(VO)(S-L1)(OH)]·5H2O (V-3b) and [MnL2]·[(CH3CH2)3NH]2·5H2O (Mn-4) were synthesized and fully characterized. Furthermore, hybrid protein, binding with complexes and bovine serum albumin (BSA) to enhance the antioxidant activity, were synthesized and evaluated by multispectroscopic techniques. The SOD activities of all complexes and their corresponding hybrid proteins were tested by xanthine/xanthine oxidase method, the antioxidant activity of them were determined by ABTS method. The results show that the SOD activities of the hybrid proteins are higher than that of the corresponding complexes. From the values of the antioxidant activity we obtained, there seems to be some connection between the configuration and antioxidant activity.

Two luminescence coordination polymers (CPs) formulated as {[Zn(L)(H2O)2]·H2O}n (1) and {[Cd(L)(H2O)2]·4H2O}n (2) are successfully prepared by solvothermal reactions between the corresponding metal(II) ions and 5-(4-pyridylamino)isophthalic acid (H2L). Crystallographic studies reveal that 1 and 2 exhibit similar 2D honeycomb layer networks, but have different numbers of lattice water molecules. The layers are connected through hydrogen bonds to give 3D supramolecular frameworks. CPs 1 and 2 possess coordinated water molecules and uncoordinated oxygen atoms as well as electron-rich amide groups, which are easy to recognize diverse analytes. Moreover, they show considerable stability in aqueous systems with a broad pH range from 3 to 12. Luminescence sensing experiments indicate that they can be regarded as highly sensitive sensors for detecting Fe3+ ions, CrVI anions (CrO42− and Cr2O72−) and 2,4,6-trinitrophenol (TNP) through luminescence quenching. In addition, the mechanisms for the luminescence response of CPs 1 and 2 towards Fe3+ ions, CrVI anions and TNP have been investigated in detail. Besides, CPs 1 and 2 represent two very good examples of versatile Zn/Cd-CP probes capable of sensing Fe3+ ions, CrVI anions and TNP.

Four new three-dimensional Mn(II) coordination polymers with two isomeric ligands, 5-(3-nitro-4-carboxylphenyl)isophthalic acid (H3L1) and 5-(2-nitro-4-carboxylphenyl)isophthalic acid (H3L2), have been prepared and structurally and magnetically characterized. They are of the formula [Mn(HL1)(CH3CN)] (1), [Mn(L2)]·H2O·H3O (2), [Mn3(L2)2(DMF)2]·H2O (3), [Mn4(HL2)4(H2O)5]·2H2O (4). Compounds 1–3 contain diverse alternating magnetic chain’s sequences in which the chains are linked by the organic spacers into 3D structures. In 1, the two double [(μ-Ocarboxylate)2 and (μ-syn-anti-COO)2] bridges with apparently different structural parameters alternate in the − ABAB − sequence. While in 2, the two sets of double μ-syn-anti-carboxylate bridges with slightly different structural parameters also alternate in the -ABAB- sequence. In 3, the double (μ-syn-anti-COO)2 bridges and (μ-ODMF)(μ-syn-anti-COO)(μ3-COO) triple bridges alternate in the -ABB- sequence. Compound 4 contains two sets of independent motifs: one is 1D chain based on three different double (μ-syn-anti-COO)2 bridges alternate in the -ABC- sequences; the other is 1D tape-like motifs with three different single μ-syn-anti-COO bridges. Two sets of motifs in 4 are alternately linked together by the organic backbones into a complicated 3D structure. Compounds 1, 2 and 4 exhibit weak antiferromagnetic couplings. A magnetostructural survey indicates that the antiferromagnetic coupling through the (μ-syn-anti-COO)2 bridges decreases as the Mn⋯Mn distances increases and the magnitude of antiferromagnetic coupling mainly depends on the Mn O Mn angle for the double (μ2-Ocarboxylate)2 bridges.

Five novel isomorphous 3D CoII2-xZnIIx (0 ≤x ≤ 2) coordination frameworks formulated as [CoII2-xZnIIx(pymtz)2(N3)2(H2O)2]·2H2O, (x = 0 (1), 1 (2), 1.5 (3), 1.7 (4), 2 (5), pymtz = 5-(3-pyrimidyl)tetrazolate) were synthesized by in situ hydrothermal reaction and then structurally and magnetically characterized. In these compounds, adjacent metal ions are linked by mixed double azide and tetrazolate bridges to give 1D coordination chains, and each chain is interlinked by pymtz ligands into 3D frameworks with (3,4,6)-connected net of (3.6.8)(32.61.73)(32.62.88.101.112) topology. Magnetic studies indicate that the homometallic CoII compound (1) exhibits the coexistence of antiferromagnetic ordering and slow magnetic dynamics, while the bimetallic CoII2-xZnIIx series (2-4) show the innocent blending effect which tends to decrease the blocking temperature (TB) of the spin slow dynamics. The homometallic ZnII compound (5) exhibits strong luminescence in the solid state at room temperature while the luminescent intensity of 5 gradually decreases as ZnII is replaced by CoII.

A series of water-stable isostructural mono/bimetallic lanthanide metal-organic frameworks (Ln-MOFs) {[Eu5xTb5(1−x)(OH)6(TZI)3(DMA)1.5(H2O)10.5]·DMA·0.5H2O}n (x = 1.0 (1), 0.5 (3), 0.4 (4), 0.3 (5), 0.2 (6), 0.1 (7), 0.05 (8), 0 (2), H3TZI = 5-(1H-tetrazol-5-yl)isophthalic acid) were synthesized. These Ln-MOFs exhibit 3D frameworks in which 1D chains based on pentanuclear [Ln5(µ3-OH)6(COO)5]4+ clusters are linked by TZI backbones. The luminescent investigations revealed that compounds 1 and 2 not only exhibit characteristic Eu3+ and Tb3+ emissions in the red and green regions, respectively, but also can sensitively and selectively detect Fe3+ cations, CO32−, PO43−, AsO43− anions and acetone molecules in aqueous solution. In addition, the luminescent colors of the bimetallic (Tb5(1−x):Eu5x) compounds can easily be tuned by doping isostructural Ln- MOFs with Eu3+ and Tb3+ ions. This work presents some good candidate materials for the potential multifunctional sensors.

Eight new 2D isostructural lanthanide coordination polymers (Ln-CPs), [Ln(HL)(H2O)2(NO3)]·NO3 (1-Ln), Ln = NdIII, SmIII, EuIII, GdIII, TbIII, DyIII, HoIII, and YbIII ions, H2L = 4-(3,5-dicarboxylphenyl)-2-methylpyridine, were synthesized by using solvothermal methods and studied by structural analyses, magnetic analyses and luminescent probes. Crystallographic studies revealed that these compounds are 2D frameworks in which dinuclear units with double μ-syn,syn-carboxylate bridges are interlinked by single μ-trans,trans-carboxylate bridges from organic spacers. The layers are further stabilized and combined into 3D architectures through intra- and interlayer π⋯π stacking interactions and hydrogen bonding, respectively. Magnetic investigations indicated that the carboxylate bridges transmit intralayer antiferromagnetic coupling in 1-Nd, 1-Gd and 1-Ho but transmit intralayer ferromagnetic coupling in 1-Dy. Furthermore, 1-Dy also displays slow magnetic relaxation behavior with a high relaxation energy barrier (ΔUeff) of 100.7 K and a pre-exponential factor (τ0) of 1.4 × 10−8 s under zero dc field. The luminescence investigations showed that CPs 1-Eu and 1-Tb can serve as highly selective and recyclable sensing materials for Fe3+, Cr2O72− and nitrobenzene. Thus, both 1-Eu and 1-Tb should be excellent candidates for multifunctional sensors.

Three lanthanide metal-organic frameworks (Ln-MOFs), [Ln(TZI)(H2O)4]·3H2O (Ln=Gd (1) and Tb (2) and Dy (3), H3TZI=5-(1H-tetrazol-5-yl)isophthalic acid), have been synthesized under hydrothermal conditions. Single crystal X-ray diffraction reveals that 1–3 are isostructural and display a 1D double chain based on dinuclear motifs with (μ-COO)2 double bridges. Magnetic studies indicate antiferromagnetic interactions in 1, ferromagnetic interactions in 2 and 3. Furthermore, compound 3 displays a slow relaxation behavior. Compound 2 exhibits intense characteristic green emission of Tb(III) ions in the solid state, which can be observed by the naked eye under UV light. Interestingly, 2 can selectively sense Pb2+ and Fe3+ ions through luminescence enhancement and quenching, respectively. The luminescence quenching mechanisms have been investigated in detail. The study on luminescence Ln-MOFs as a probe for sensing Pb2+ and Fe3+ ions is exceedingly rare example.

Two coordination polymers, [Co(L1)0.5(N3)2]n·3nH2O (1), [Cu3(OH)3(L2)3(H2O)1.5]n·nH2O (2), (H2L1 = 1,4-bis(4-carboxylatopyridinium-4-benzoate-1-methylene)benzene, HL2 = 4-(4-oxypyridinium-1-yl)benzotetrazolate) have been synthesized and studied by means of X-ray crystallography and magnetic analyses. Compound 1 exhibits a 2D braided grid structure, in which 1D [Co(N3)2(COO)]n chains are cross-linked by the cationic bis(pyridinium) spacers of the L1 ligand. Compound 2 is a 1D coordination chain in which the Cu(II) ions are linked by the mixed (μ-OH)(μ-N,N-tetrazolate) double bridges. The mixed (μ-EO-N3)2(COO) triple bridges transmits the ferromagnetic interaction between Co(II) ions, while the antiferromagnetic interaction between Cu(II) ions was induced by the mixed (μ-OH)(μ-N,N-tetrazolate) double bridges.

Two Cu(II) coordination polymers with two isomeric pyridylbenzoate N-oxide ligands, 4-(4-pyridyl)benzoic acid N-oxide (4,4-Hopybz) or 4-(3-pyridyl)benzoic acid N-oxide (4,3-Hopybz), were synthesized and structurally and magnetically characterized. They are formulated as [Cu(4,4-opybz)(OH)]n (1) and [Cu(4,3-opybz)(OH)]n (2). The two compounds show similar layer structures, in which 1D coordination chains with uniform [(μ-OH)(μ-COO)] double bridges are linked by the 4,4-opybz or 4,3-opybz ligands. Magnetic studies revealed that the mixed double bridges transmit ferromagnetic coupling in the compound 1, and the antiferromagnetic interactions exist in the compound 2. The magnetic differences can be related to the Cu–O–Cu angles influenced by isomeric pyridylbenzoate N-oxide ligands.

A novel 3D Co(II) coordination polymer, [Co6(4-ptz)6(N3)6]n (1) (4-ptz = 4-(pyridinyl)tetrazole), was synthesized by in situ hydrothermal reaction and characterized magnetically. Compound 1 consists of ferrimagnetic-like Co(II) layers with the title heterobridges and exhibits the spin-glass slow dynamics. The study on spin-glass behavior in mixed azide and tetrazolate bridged compounds is the first example.

A new cubane-based Co(ii) compound, [Co(12)(5-PT)(6)(CO(3))(N(3))2(O)(4)(CH(3)O)(6)(H(2)O)(18)] (1) (5-HPT = 5-phenyl-1H-tetrazole), was synthesized by reaction of 5-HPT, CoCl(2)·6H(2)O and NaN(3) in a methanol solution. In 1, a Co(12) cluster based on three identical Co(4)O(2)(ON)(2) cubane units bridged by a μ(6)-carbonate ligand is linked by π-π stacking interactions between phenylene groups, forming a 3D supramolecular structure. Magnetic investigations indicate that compound 1 exhibits long-range ferromagnetic ordering at about 9 K. The cube-based Co(12) clusters with μ(6)-CO(3)(2-) bridges are unprecedented.

Three coordination polymers of different transition metal ions with azide and the zwitterionic dicarboxylate ligand 1-carboxymethylpyridinio-3-benzoate (L) were synthesized, and structurally and magnetically characterized. They are formulated as [M(L)(N3)·2H2O] (M = Co, 1; Mn, 2) and [Cu(L)(N3)·H2O] (3). In the isomorphous compounds 1 and 2, octahedrally coordinated metal ions are linked by the (μ-EO-N3)2 (EO = end-on) double bridges to give dinuclear motifs, which are linked by the zwitterionic dicarboxylate ligands to produce one-dimensional (1D) coordination chains. Compounds 3 and 1 (and 2) are pseudo-isomorphous, since they crystallize in the same space group, exhibit similar crystal structures, but have different numbers of coordinated water molecules. The chains are further stabilized and packed into 3D architectures through intra- and interchain hydrogen bonding and/or π–π stacking interactions. Magnetic studies on 1 and 3 reveal that the (μ-EO-N3)2 double bridges mediate ferromagnetic coupling between metal(II) ions.

Three coordination polymers of different transition metal ions with azide and flexible zwitterionic dicarboxylate ligand 1-carboxymethylpyridinium-4-benzoate (L) were synthesized and structurally and magnetically characterized. They are formulated as [M(L)(N 3 )]·H 2 O (M = Co, 1 and Ni, 2 ) and [Cu 3 (L) 2 (N 3 ) 4 ]·7H 2 O ( 3 ). In the isomorphous compounds 1 and 2 , neighboring metal ions are linked by mixed triple (μ-EO-N 3 )(μ-COO) 2 bridges to give an anionic chain of [M(N 3 )(COO) 2 ] n , and each chain is cross-linked by the cationic 1-methylpyridinium-4-phenyl spacers to give a two-dimensional coordination layer. Magnetic studies demonstrated that the triple bridge transmits intrachain ferromagnetic interactions but show different bulk properties: compound 1 diplays a new SCM-based material exhibiting antiferromagnetic ordering, metamagnetic transition, and field-modulated slow dynamics, while compound 2 shows the usual one-dimensional ferromagnetism. Compound 3 consists of three-dimensional coordination framework in which Cu(II) chains with alternating double (μ-EO-N 3 ) 2 bridges and triple (μ-EO-N 3 )(μ-COO)(μ-O carboxylate ) bridges are interlinked by the organic spacer. Magnetic studies suggested that ferromagnetic interactions between the neighboring Cu(II) ions through the alternating bridges.

Two Mn(II) and Cu(II) coordination polymers with azide and 4-(3-pyridyl)benzoic acid N-oxide (4,3-Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as [M(4,3-opybz)(μ-N3)]n (M = Mn, 1 and Cu, 2). Compound 1 consists of 2D coordination layers in which 1D coordination chains with uniform [(μ-EO-N3)(μ-COO)(μ-O)] (EO = end-on, μ-O from N-oxide group) triple bridges are interlinked by the 4,3-opybz spacers. Compound 2 also presents a 2D coordination layers in which the Cu(II) ions are triply bridged in a fashion similar to 1, while the azide ions reside at different positions around the metal ions. Magnetic studies demonstrated that the magnetic coupling through the mixed triple bridge is antiferromagnetic in the Mn(II) compound (1) but ferromagnetic in the Cu(II) species (2).

A new one-dimensional Co(II) coordination polymer, Co(L)(N3)2 (L = pyridinio-N-acetate), has been synthesized by a diffusion method and characterized by single crystal X-ray diffraction. In the compound, Co(II) ions are linked by mixed triple bridges (two end-on azides and a syn–syn carboxylate), which transmit ferromagnetic coupling with J = 13.96 cm− 1. The compound exhibits field-induced metamagnetic behaviors below TN = 2.3 K with Hc = 100 Oe, due to weak antiferromagnetic interactions between chains.

Three copper(II) coordination polymers, namely, {[CuL(H2O)2]·4H2O}n(1), [CuL(H2O)(DMF)]n(2), and [CuL(2, 2′-bipy)(DMSO)]·DMSO (3) [H2L = 2, 2′-(4, 6-dinitro-1, 3-phenyl-enedioxy)diacetic acid] were synthesized in different solvents (H2O, DMF, and DMSO). X-ray single crystal diffraction studies show that both complexes 1 and 3 belong to triclinic crystal system and P space group and complex 2 belongs to the monoclinic crystal system and P21/c space group. In three complexes, all the central CuII ions coordinate with the ligand, forming a square pyramidal configuration. Both complexes 1 and 2 show similar 1D chain-like structure and the chains are further connected by hydrogen bonds, forming 3D frameworks. Complex 3 exhibits a 0D structure due to the introduction of the ligand 2, 2′-bipy. In addition, the luminescence properties of these complexes were investigated.

Two azide-bridged coordination polymers, [Cu(mptz)(N3)2] (1) and [Mn(mptz)(N3)2H2O] (2), (mptz = N-methyl-4-pyridinium tetrazolate), were synthesized and crystallographically and magnetically characterized. Compound 1 is a neutral 1D coordination polymer in which the CuII ions, which are in a square pyramidal surrounding, are linked by double end-on azide bridges in an alternating basal–basal and basal–apical fashion. Compound 2 exhibits a 3D MnII–azide coordination framework with the (10,3)-b net topology, in which the double end-on–azide-bridged dimanganese units are interlinked by single end-to-end azide bridges. The magnetic analyses indicated that 1 behaves magnetically as a quasi-dimer with an S = 1 ground state due to a strong ferromagnetic interaction through the basal–basal azide bridges and a very weak antiferromagnetic coupling through the basal–apical azide bridges. Compound 2 exhibits 3D antiferromagnetic behaviors with TN = 24.0 K, where the end-to-end and end-on azide bridges mediate the antiferromagnetic and ferromagnetic interactions, respectively.

Three transition-metal coordination polymers with azide and/or carboxylate bridges have been synthesized from 4-(3-pyridyl)benzoic acid (4,3-Hpybz) and 4-(4-pyridyl)benzoic acid (4,4-Hpybz) and characterized by X-ray crystallography and magnetic measurements. Compound 1, [Cu(4,3-pybz)(N(3))](n), consists of 2D coordination networks in which the uniform chains with (μ-EO-N(3))(μ-COO) double bridges are cross-linked by the 4,3-pybz ligands. Compound 2, [Cu(2)(4,4-pybz)(3)(N(3))](n)·3nH(2)O, consists of 2-fold interpenetrated 3D coordination networks with the α-Po topology, in which the six-connected dinuclear motifs with mixed (μ-EO-N(3))(μ-COO)(2) (EO = end-on) triple bridges are linked by the 4,4-pybz spacers. Compound 3, [Mn(4,4-pybz)(N(3))(H(2)O)(2)](n), contains 2D manganese(II) coordination networks in which the chains with single μ-EE-N(3) bridges (EE = end-to-end) are interlinked by the 4,4-pybz ligands, and the structure also features a 2D hydrogen-bonded network in which Mn(II) ions are linked by double triatomic bridges, (μ-EE-N(3))(O-H···N) and (O-H···O)(2). Magnetic studies indicated that the mixed azide and carboxylate bridges in 1 and 2 induce ferromagnetic coupling between Cu(II) ions and that 3 features antiferromagnetic coupling through the EE-azide bridge. In addition, compound 1 exhibits antiferromagnetic ordering below 6.2 K and behaves as a field-induced metamagnet. A magnetostructural survey indicates a general trend that the ferromagnetic coupling through the mixed bridges decreases as the Cu-N-Cu angle increases.

Three coordination polymers of the iron-series transition metal ions with 4-(3-pyridyl)benzoic acid (4,3-Hpybz) ligand were synthesized and structurally and magnetically characterized. They have the formulas [M2(4,3-pybz)4(H2O)] (M = Fe, 1; Co, 2; and Ni, 3). In these isomorphous compounds, octahedrally coordinated metal ions are linked by the mixed (μ-syn, syn-COO)2(μ-H2O) triple bridges to give dinuclear motifs, which serves as tetrahedral building units and are further linked by 4,3-Hpybz to give rise to diamond networks. Magnetic studies demonstrated that the (COO)2(H2O) triple bridges induce antiferromagnetic coupling between metal ions in 1 and 2, but compound 3 with the same mixed triple bridges exhibits ferromagnetic coupling, which may be related to orbital countercomplementarity.

Two Cu II complexes with the new zwitterionic ligand 1-carboxymethylpyridinio-3-benzoate (L), (Cu 4 L 4 (OH) z] (ClO 4 ) 2 · 8H 2 O (1) and [Cu 4 L 4 (OH) 2 ]Cl 2 ·8H 2 O (2), have been synthesized and characterized crystallographically and magnetically. The two compounds contain isostructural chains, in which the anionic basic copper(II) carboxylate clusters [Cu 4 (μ 3 -OH) 2 (RCOO) 8 ] 2- are quadruply interlinked by cationic organic spacers. Magnetic analyses using a tetranuclear model indicate that antiferromagnetic interactions between neighboring copper(II) ions are operative through the double hydroxo bridges and the mixed hydroxo/carboxylato bridges.

Three isostructural Mn(II) compounds with a zwitterionic dicarboxylate ligand and different pseudohalides were synthesized, and then structurally and magnetically characterized. They are formulated as [Mn(L)(X)(2)(H(2)O)(2)](n) [X = N(3)(-) (1), NCO(-) (2), NCS(-) (3), L = 1,4-bis(4-carboxylato-1-pyridinium)butane]. In these compounds, adjacent Mn(II) ions are connected into coordination chains by long zwitterionic linkers and into hydrogen-bonded chains by short double O-H···N bridges involving coordinated water and pseudohalide ligands. Magnetic studies revealed for the first time that the double hydrogen bridges induce ferromagnetic coupling between the Mn(II) ions.

Two novel Mn(II) coordination polymers with azide and 4-(4-pyridyl)benzoic acid N-oxide (4,4-Hopybz) were synthesized and structurally and magnetically characterized. They are formulated as {[Mn(2)(4,4-opybz)(2)(N(3))(2)(H(2)O)(2)]·H(2)O}(n) (1) and {[Mn(4)(4,4-opybz)(5)(N(3))(H(2)O)(8)](N(3))(2)·2H(2)O}(n) (2). Compound 1 contains 2D coordination layers in which the infinite Mn(II) chains with alternating (μ-EO-N(3))(2)(μ-COO) (EO = end-on) and (μ-COO)(μ-O) bridges are interlinked by the backbones of the organic ligands. Compound 2 is a 3D metal-organic framework in which the unique linear tetranuclear clusters with (μ-EO-N(3))(μ-COO) and (μ-COO)(μ-O) bridges are cross-linked by organic backbones, and it represents a new example of the rare 8-connected self-catenated 3D net with the point symbol 4(16)·6(12). Magnetic analyses on the compounds have been performed in the classical-spin approximation, revealing that all the above-mentioned mixed bridging motifs induce weak antiferromagnetic interactions between Mn(II) ions.

Two coordination polymers formulated as [{[Co(2)(L)(N(3))(4)]·2DMF}(n) (1) and [Mn(2)(L)(H(2)O)(0.5)(N(3))(8)](n) (2) (L = 1,4-bis(4-carboxylatopyridinium-1-methyl)benzene) were synthesized and structurally and magnetically characterized. In compound 1, the anionic uniform Co(II) chains with mixed (μ-EO-N(3))(2)(μ-COO) triple bridges (EO = end-on) are cross-linked by the cationic bis(pyridinium) spacers to generate 2D coordination layers. It was demonstrated that the triple bridges mediate ferromagnetic coupling and that the compound represents a new example of the rare systems exhibiting the coexistence of antiferromagnetic ordering, metamagnetism, and slow magnetic dynamics. Compound 2 features the magnetic Δ-chain formed from isosceles triangular units with single μ-EE-N(3) and double (μ-EO-N(3))(μ-COO) bridges (EE = end-to-end). The Δ-chains are interlinked by long organic ligands into a 3D framework with novel net topology and 3-fold interpenetration. The magnetic properties of 2 indicate the presence of spin frustration characteristic of Δ-chains with antiferromagnetic interactions.

Two isomorphous Co(II) and Ni(II) coordination polymers with azide and the 4-(4-pyridyl)benzoic acid N-oxide ligand (4,4-Hopybz) were synthesized, and structurally and magnetically characterized. They are formulated as [M(4,4-opybz)(N(3))(H(2)O)](n) (M = Co, 1 and Ni, 2). The compounds consist of 2D coordination networks, in which 1D coordination chains with (μ-N(3))(μ-COO) bridges are interlinked by the 4,4-opybz spacers, and the structure also features intra- and interchain O-HO hydrogen-bonding bridges between metal ions. Both compounds exhibit ferromagnetic interactions through the intrachain (μ-N(3))(μ-COO)(O-HO) bridges and antiferromagnetic interactions through the interchain O-HO bridges. The ferromagnetic chains are antiferromagnetically ordered, and the antiferromagnetic phases exhibit field-induced metamagnetic transition. It is found that 1 displays slow relaxation of magnetization, typical of single-chain magnets, while 2 does not. The difference emphasizes the great importance of large magnetic anisotropy for single-chain-magnet dynamics.