By utilizing the pre-designed bi-functional ligand 4-{bis(4-benzoic)amino}-4H-1,2,4-triazole (H2L), five new transition-metal-based coordination polymers, namely, {[Zn(L)]·H2O·DMA}n (1), {[Zn2(L)2]·DMF}n (2),{[Mn(L)]·DMF}n (3), {[Cd(L)]·DMA}n (4) and [Cu3(OH)2(L)2]n (5) have been constructed and structurally characterized. In 1, the tetrahedral zinc ion was incorporated in the final structure. However, complexes 2, 3 and 4 bear 1D Zn-, Mn- and Cd-chains composed of metal ions, triazole and carboxyl groups, respectively. Differently, 1D [Cu4(μ3-OH)2] chains had been stabilized in the 3D structure of 5. In addition, the luminescence or magnetic properties of 1–5 had been correspondingly investigated with the consideration of their crystal structure. The whole research results manifest that utilizing a bi-functional ligand containing carboxyl and triazole groups is an efficient building method in constructing functional CPs.

By utilizing a solvothermal method, a series of six-membered cyclic lanthanide(III) clusters, {Gd6(H3L)6(benzoate)6}·2H2O·C7H8 (1), {Tb6(H3L)6(benzoate)6}·2H2O·C7H8 (2) and {Dy6(H3L)6(benzoate)6}·2H2O (3), have been constructed with the pentol ligand, 2,2-bis(hydroxymethyl)-2,2′,2″-nitrilotriethanol (H5L). Similar hexa-nuclear ring structures were observed in each of the crystal structures. In addition, magnetization studies indicated that Gd6 displays large magnetic entropy changes in low temperature regions. What is particularly interesting about this ring is the presence of slow magnetic relaxation behavior under a zero dc field, indicating a non-magnetic ground state with a net toroidal magnetic moment. Compared to the other reported Dy6 clusters, modulation of the ligand fields, the presence of amine coordinating sites and the subsequent electron density of the Dy centers along with the utilized pentol ligand might be indeed responsible for the improved barrier to magnetic relaxation.

Two diynes bearing functional groups with different binding modes, 3,6-diethynylpyrazine (H2L1) and 3,8-diethynyl-1,10-phenanthroline (H2L2), were utilized as ligands to synthesize two new organometallic units, Ag2L1·3AgNO3 (1) and Ag2L2·6AgNO3 (2), in order to investigate the effect of the bridging and chelating modes of the ligands on the structures of networks constructed from silver-ethynide compounds. Structural studies show that in 1, silver-ethynide cluster units aggregate to form chair-like organometallic slides through Ag–N coordination bonds. These slides are linked through argentophilic interaction to generate novel 2D ladder-like layers, and are further bridged by nitrate anions to afford a 3D network in the solid state. It is observed that all the Ag ions in one layer interact to afford a 2D silver network. However, in 2, the silver-ethynide cluster units only interact to generate unique sine wave-like organometallic chains through argentophilic interaction, which are further connected by nitrate anions to form a 3D network. In the solid state, both 1 and 2 are luminescent at room temperature.

Two halogen-bridged di-nuclear Cu-based 3D porous metal–organic frameworks (MOFs), {[Cu2Cl(OH)(L)2]·(CH3OH)4}n (1) and {[Cu2Br(OH)(L)2]·(CH3OH)4}n (2), have been obtained via solvothermal methods with the bi-functional ligand (HL = 4,2′:6′,4′′-terpyridine-4′-carboxylic acid). These Cu-based frameworks exhibit similar two-interpenetrating frameworks, and 1D channels were left in the packing structures. These MOF materials were then applied as electrode active materials in supercapacitors. Compound 1 presents a high specific capacitance and good cycling stability in 6 M KOH electrolyte compared to 2. The maximum specific capacitance of electrode 1 could reach 1148 F g−1 at a current density of 0.5 A g−1, along with a high capacitance of 90% retained after 2000 cycles at a current density of 10 A g−1 in a 6 M KOH solution. The successful introduction of halogen and hydroxyl ions into the final structures might be responsible for the high performance of the supercapacitor, which makes these Cu MOFs a candidate for an electrode active material for electrochemical energy storage.

By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt–carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 63 cobalt–carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of −/+/− for syn–anti carboxylate bridges and −/−/− for syn–syn carboxylate bridges. Through HF-EPR measurements performed on polycrystalline samples over the frequency range of 60–260 GHz and field range of 0–12 T, the effective g-values of 1 and 2 were all larger than 2.00, and the signs of their D values were probably positive.

The hydrothermal reaction of CoCl2 and 4-((1-carboxy-2-(1H-imidazol-4-yl)ethylamino)methyl)benzoic acid (H2L) generated a {Co2(H2O)}-based 2D coordination framework, {(Co(L)(H2O))2(H2O)}n (1). Heterogeneous catalytic experiments on the allylic oxidation of cyclohexene show that activated 1 exhibits high catalytic activity using tert-butylhydroperoxide (t-BuOOH) as the oxidant toward the formation of tert-butyl-2-cyclohexenyl-1-peroxide. The activation energy for the oxidation of cyclohexene with catalyst 1 was approximately calculated as 91.98 kJ mol−1. This work demonstrates that a degree of creativity in the coordinatively unsaturated metal sites in CPs could significantly enhance their heterogeneous catalytic activity and selectivity.

Two silver(I)-organometallic polymers have been constructed by utilizing the different silver(I) salts and a bowl-shaped calix[4]arene functionalized with tetra-allyl groups on the upper rim (L). Reacted with AgClO4 to afford 1, 1 exhibits a two-dimensional (2D) structure, where tetra-allyl-functionalized calix[4]arene units are linked through Ag–alkene interaction to generate wave-like organometallic chains and further connected by bridging by acetone molecules to afford a 2D network, giving a 2,4,4-net with the point (Schläfli) symbol {42·82·102}{42·84}2{4}2. Substituting ClO4– by NO3– as the counteranion of silver(I) salt, a three-dimensional organometallic polymer (2) encapsulating solvent molecules in the cavities was generated by connection of 2D inorganic AgNO3 layers and pillared L ligands, which gave a 3,3,4,4-net with the point (Schläfli) symbol {6·7·8}2{62·7·82·9}2{62·72·92}{62·7}2. In addition, thermogravimetric analysis, luminescent properties, and voltammetric behavior of 1 and 2 also have been investigated. Structural results for these complexes show that the different counteranions play an important role in constructing silver(I)-organometallic polymers with thus flexible tetra-allylcalix[4]arene.

Two coordination polymers (CPs) with a novel bifunctional ligand, [ZnL]n (1) and [CdL(H2O)]n (2), (L = rigid 6-(1H-tetrazol-5-yl)-2-naphthoic acid), have been synthesized and structurally characterized, which reveal that the two constructed CPs exhibit three dimensional structures. The two CPs consist of a one-dimensional Zn-tetrazole chain and a double-layered two-dimensional Cd-tetrazole structure. In addition, IR, elemental analysis, and luminescent spectra of 1 and 2 were also examined. At room temperature, 1 exhibits an intense emission at around 421 nm upon 370 nm excitation, whereas 2 exhibits an intense emission at 381 nm upon 350 nm excitation. Through variable-temperature luminescent and quantum calculations, the blue-shift of the peaks from the ligand and 1 and 2 is ascribed to the different configurations of L caused by the different coordination environments of the metal ions.

Solvothermal reactions of tetrakis(4-pyridyloxymethyl)methane (TPOM) and 4,4′-oxybisbenzoic acid (H2oba) with different metal ions under different synthesis temperatures produced three new coordination polymers (CPs), namely, {[Co2(TPOM)(oba)2(H2O)2]}n (1), {[Zn2(TPOM)(oba)2]}n (2) and {[Cd2(TPOM)(oba)2(H2O)2]}n (3). 1 and 3 present similar topological structures which can be analyzed in two different ways. 2 exhibits a rare porous structure assembled by the tetra-pyridinate ligand TPOM. The luminescence properties of 2 and 3 as well as those of the corresponding samples immersed in different solvents have been investigated, and they suggested a potential application in luminescence sensing. In addition, the dye and iodine adsorption properties of an activated sample of 2 were also investigated. All of the results indicate that the proper selection of metal ions and auxiliary ligands plays an important role in constructing porous coordination polymers.

A new three-dimensional magnetic network, [Co9(OH)6(C42H24O18P3N3)2(H2O)8] (1), has been successfully prepared by utilizing the flexible hexacarboxylate ligand derived from cyclotriphosphazene, which had been characterized by single-crystal X-ray diffraction and magnetic measurement. This compound consists of one-dimensional (1D) cobalt-hydroxyl chains based on planar nonanuclear clusters, which are located in the b–c plane to form the nearly two-dimensional cobalt layer. Magnetic measurements reveal that 1 shows spin-canted antiferromagnetism with spin-glass behavior. These results suggest that reasonable design and choice of large carboxylate ligand based on a specific scaffold could be effective for the construction of magnetic materials based on a novel 1D magnetic chain.

By utilizing two similar flexible quadritopic ligands, tetrakis(4-pyridyloxymethyl)methane (4-TPOM) and tetrakis(3-pyridyloxymethyl)methane (3-TPOM), four new azido-containing coordination polymers with formulas [Mn3(4-TPOM)3(N3)6(H2O)6]n (1), [Ni(4-TPOM)(N3)2]n (2), [Mn(3-TPOM)2(N3)2(H2O)3(CH3OH)4]n (3) and [Co(3-TPOM)(N3)2]n (4) have been synthesized and structurally characterized. Compound 1 shows a 1D helical chain composed of six-coordinated MnII geometries and two-connected tetra-pyridinate ligands. Compound 2 exhibits a three-dimensional framework based on 1D Ni(II) chains with alternating double end-to-end (EE) and double end-on (EO) azide bridges and tetrapyridyl ligands in a highly distorted conformation. Compound 3 shows a 2D layer composed of six-coordinated MnII geometries with mono-dentate azide ions and two types of two-connected tetra-pyridinate ligands. Compound 4 exhibits a three-dimensional framework based on 1D Co(II) chains with double end-to-end (EE) azide bridges and tetrapyridyl ligands in a cross-shaped conformation. Magnetic investigations on complexes 2 and 4 revealed antiferromagnetic interactions through the bridged azide ligands. In addition, the magnetic measurement reveals that 2 exhibits weak antiferromagnets, which might be caused by spin canting.

Two distinct template mediated coordination polymers, [Co3(ina)4(N3)2(CH3OH)2] with tri-nuclear nodes (1) and [Co8(OH)(ina)8(N3)8·X] with dual tetra-nuclear cobalt nodes (2), have been synthesized under hydrothermal conditions by utilizing the template agent of pentaerythritol. 1 shows a 2D layer comprised of linear tri-nuclear CoII clusters, in which the central cobalt ion is inter-linked with two terminal ones via mixed bridges as syn–syn carboxylates and end-on azide ions. In contrast, compound 2 exhibits a three-dimensional framework based on two kinds of six-connected tetra-nuclear cobalt clusters: square-planar node and cuboidal node. Both 1 and 2 might exhibit spin-canted magnetism. In addition, the activated sample of 2 exhibits the sorption ability of H2 and CO2 molecules.

•One mono-nuclear iron(III) complex was synthesized.•An incomplete spin transition is exhibited.•The tripodal ligand plays the important role in affecting the SCO behavior.A new mononuclear Fe(III)–catecholate complex, which exhibits an incomplete spin transition without hysteresis, had been synthesized and structurally characterized. Analyzed from the structural characteristics, the tripodal ligand must play the important role in affecting the spin crossover (SCO) behavior. The larger steric strain effect and weak cooperativity existed in the crystal lattice are inclined to favor the incomplete transition.A new mononuclear Fe(III)–catecholate complex, which exhibits an incomplete spin transition without hysteresis, had been synthesized and structurally characterized. Analyzed from the structural characteristics, the tripodal ligand must play the important role in affecting the SCO behavior.

•A new di-nuclear valence tautomeric complex was formed.•Valence tautomeric transition with a small hysteresis around room temperature and photo-excited phenomenon is exhibited.•Temperature-dependent hs–ls relaxation of the converted high-spin fraction after irradiation was also studied.A di-nuclear compound, [(CoTPA)2(1,4-BQ)][AsF6]3 (1) (TPA = tris(2-pyridylmethyl)amine, 1,4-BQ = deprotonated 2,5-dihydroxy-1,4-benzoquinone), was formed by one electron oxidation of [(CoTPA)2(1,4-BQ)]2+ cations. The compound was characterized by X-ray diffraction, electrochemistry, ESR, thermal- and photo-induced magnetic measurements. Variable temperature magnetic measurements have demonstrated that valence tautomeric transition with a small hysteresis around room temperature and photo-excited phenomenon is exhibited. In addition, temperature-dependent hs–ls relaxation of the converted high-spin fraction after irradiation was also studied.A new di-nuclear valence tautomeric complex was formed and characterized by X-ray diffraction, electrochemistry, ESR, thermally and photo-induced magnetic measurements. Variable temperature magnetic measurements have demonstrated that valence tautomeric transition with a small hysteresis around room temperature and photo-excited phenomenon is exhibited. In addition, temperature-dependent hs–ls relaxation of the converted high-spin fraction after irradiation was also studied.

Reactions of 3-(2-hydroxy-5-methylphenyl)pyrazole (H2Meppz) with different iron salts and bases in solutions lead to compounds [Fe(HMeppz)2Cl] (1) and [Na3Fe6O(OH)7(Meppz)6] (2). These two compounds are then structurally characterized. In mono-nuclear complex 1, iron(III) ion has a square-pyramidal geometry. The mono-nuclear units are further inter-connected by the hydrogen bonds between the N–H of pyrazole ring and the halogen of neighboring molecule to form ladder-like 1D chain. In contrast, substituting the chloride salt with acetate salt, a hexa-nuclear iron(III) cluster 2 is obtained. In 2, the octa-hedral iron ions are interacted with eachother by the hydroxyl bridges, and stabilized by the fully deprotonated Meppz2– ligands. In addition, the magnetic properties of compound 2 had been investigated. Magnetic analysis indicates the presence of antiferromagnetic interactions within the Fe6 cluster.

Utilizing the flexible hexa-carboxylate ligand derived from cyclotriphosphazene, a novel anionic metal–organic framework based on an octa-nuclear zinc cluster has been synthesized, showing the variable luminescent properties controlled by different guest cations.

Three coordination polymers, {[Co2(L)2(H2O)8]·(H2O)2·(DMF)2}n (1), {[Cd2(L)2(H2O)5]·(H2O)2·(DMF)2}n (2), and {[Eu(L)1.5(H2O)3]·(H2O)·(DMF)2}n (3) (H2L = 4,4′-(diethynylanthracene-9,10-diyl) dibenzoic acid) based on a new dicarboxylate ligand have been synthesized and structurally characterized, in which the di-carboxylate ligand could act as multi-dentate bridging linker with different connection modes to connect various metal ions. Complex 1 exhibits an oligomer structure containing a mono-dentate dicarboxylate ligand and di-nuclear cobalt joint. Complex 2 is a double-chained 1D wire based on a bidentate-chelating/bridging ligand and mono-Cd ion. In contrast, complex 3 possesses a 3D open framework based on an infinite Eu-(μ2-OOC) chain and bridging ligands. In terms of the distinction between the three crystal structures, it is concluded that the coordination number and mode of metal ions and ligands play important roles in constructing the final crystal structure. In addition, the thermal stabilities and photoluminescence behavior of 1–3 and the gas sorption of 3 are further discussed in relative detail.

Solvothermal reactions of two ligands with different geometries, derived from cyclotriphosphazene, hexakis(4-carboxylato-phenoxy)cyclotriphosphazene (H6L1) and hexakis(3-carboxylato-phenoxy)cyclotriphosphazene (H6L2) with Eu(NO3)3·6H2O in H2O/DMF under similar synthesis conditions produced three new compounds, namely, {[Eu2(L1)(H2O)4]·(H2O)4·(DMA)2}n (1), {[Eu2(L1)(H2O)8]·(H2O)2·DMA}n (2), and {[Eu2(L2)(H2O)3(DMF)]·(H2O)2·(DMA)}n (3). Compounds 1 and 2 display a 2D layer crystal structure with a distinct topological network incorporating the extended hexa-carboxylate ligand L1; in contrast, 3 has a 1D crystal structure with the highly distorted hexa-carboxylate ligand L2. In these three compounds, the ligands L1 and L2 are fully deprotonated, whose six extended carboxyl arms connect six different/same metallic nodes to generate metal–organic frameworks. The luminescence properties of three compounds have been studied at room temperature in relative detail.

•One hepta-bimetallic complex has been synthesized.•Very weak intercluster antimagnetic coupling is exhibited.•The weak coupling might be mediated via the –NC-Mo-CN- bridging units.A new heptanuclear complex [{Cu(TPA)CN}6Mo(CN)2][ClO4]8 (1) (TPA = tris(2-pyridylmethyl)amine) was formed by the reaction of [Cu(TPA)]2 + cations and K4Mo(CN)8. The octacyanomolybdate core is encapsulated by six mononuclear copper cations via cyano bridges. 1 Crystallizes in monoclinic space group P21/n with a = 22.30(2) Å, b = 27.13(3) Å, c = 24.35(2) Å, β = 94.10(2)°, and Z = 4. Variable temperature magnetic measurements have demonstrated that very weak antimagnetic interaction between the nearest paramagnetic CuII centers at low temperature is exhibited, transferred by ―NC―Mo―CN― bridging units.A new heptanuclear complex was formed by the utilization of K4Mo(CN)8. The octacyanomolybdate core is encapsulated by six mononuclear copper cations via cyano bridges. Variable temperature magnetic measurements have demonstrated that very weak antimagnetic interaction between the nearest paramagnetic CuII centers at low temperature is exhibited.

Two diynes bearing functional groups with different binding modes, 3,6-diethynylpyrazine (H2L1) and 3,8-diethynyl-1,10-phenanthroline (H2L2), were utilized as ligands to synthesize two new organometallic units, Ag2L1·3AgNO3 (1) and Ag2L2·6AgNO3 (2), in order to investigate the effect of the bridging and chelating modes of the ligands on the structures of networks constructed from silver-ethynide compounds. Structural studies show that in 1, silver-ethynide cluster units aggregate to form chair-like organometallic slides through Ag–N coordination bonds. These slides are linked through argentophilic interaction to generate novel 2D ladder-like layers, and are further bridged by nitrate anions to afford a 3D network in the solid state. It is observed that all the Ag ions in one layer interact to afford a 2D silver network. However, in 2, the silver-ethynide cluster units only interact to generate unique sine wave-like organometallic chains through argentophilic interaction, which are further connected by nitrate anions to form a 3D network. In the solid state, both 1 and 2 are luminescent at room temperature.

By utilizing well-designed bifunctional ligands derived from 1H-imidazole-4,5-dicarboxylic acid, magnetic coordination polymers (CPs) that exhibit slow magnetic relaxation at the low temperature regions were constructed and further structurally characterized. In 1, 1D cobalt–carboxyl chains were stabilized in the final structure. In contrast, by adjusting the length of the substituted arms on imidazole-4,5-dicarboxylic acid, a novel 3D CP, 2 containing 2D 63 cobalt–carboxyl layer was obtained. A combination of Quantum Monte Carlo (QMC) simulations and the first-principles Density functional theory (DFT) calculations showed that compound 2 features weak ferro- and antiferro-magnetic coupling mechanisms with two different super-exchange paths of −/+/− for syn–anti carboxylate bridges and −/−/− for syn–syn carboxylate bridges. Through HF-EPR measurements performed on polycrystalline samples over the frequency range of 60–260 GHz and field range of 0–12 T, the effective g-values of 1 and 2 were all larger than 2.00, and the signs of their D values were probably positive.