Interlayer interaction-force-tuned magnetic responses in CoII-tetrazolate-carboxylate system from canted antiferromagnet to field-induced metamagnet.

Interlayer magnetic couplings of low-dimensional magnets have significantly dominated magnetic behavior through skillful regulation of interlayer interacting forces. To identify interaction-force-regulated interlayer magnetic communications, two air-stable Co(II)-based coordination polymers (CPs), a well-isolated layered structure with approximately 12.6 Å interlayer separation and a carboxylate-extended three-dimensional framework with an inter-ribbon distance of 5.8 Å, have been solvothermally fabricated by varying polycarboxylate mediators in a ternary CoII-tetrazolate-carboxylate system. The layered CP with antiparallel-arranged {Co2(COO)2}n chains interconnected only via cyclic tetrazolyl linkages behaves as a spin-canted antiferromagnet with a Néel temperature of 2.6 K, due to strong intralayer antiferromagnetic couplings and negligible interlayer magnetic interactions. In contrast, the compact three-dimensional framework with corner-sharing Δ-ribbons tightly aggregated through µ2-η1:η1-COO- is a field-induced metamagnet from a canted antiferromagnet to a weak ferromagnet with a small critical field of Hc = 90 Oe. Apparently, these interesting magnetic responses reveal the importance of an interacting force from the magnetic subunits for the magnetic behavior of the molecular magnet, greatly enriching the magnetostructural correlations of transition-metal-based molecular magnets.

Side-Group Effect on the Slow Relaxations of {Dy2} Single-Molecule Magnets with Confined N2O6 Donors.

Deep insights into and substantial enhancement of the effective anisotropy energy barrier for magnetization reversal (Ueff) are vitally important for the technological applications of dysprosium(III)-based single-molecule magnets (Dy-SMMs). To fully refine the ligand-field effect on spin relaxation, four centrosymmetric {Dy2} entities with formula [Dy2(CH3OH)2L2(RCOO)2] (H2L = 2-hydroxy-N'-((pyridin-2-yl)methylene)benzohydrazide) have been solvothermally prepared by varying the side groups of carboxylate coligands (RCOO-, R = CF3 for 1, H for 2, CH3 for 3, and Cp2Fe for 4). Structural analyses reveal that all of the DyIII carriers in 1-4 have the same N2O6 donor environments, and the non-coordinative R groups attached to the equatorial carboxylate bridges have not substantially changed the binding ability of the shortest Dy-Ophenolate bonds located at the axial position of the ligand field. Interestingly, the side groups have monotonically decreased the zero-field Ueff barriers of these weak antiferromagnetically coupled {Dy2} analogues from 721 K down to 379 K. Further electronic structure calculations demonstrate that the main magnetic axes of 1-4 are highly dominated by these comparable Dy-Ophenolate short bonds, and the g tensors have produced gradually increased transverse components responsible significantly for the decreased Ueff barriers. Additionally, thermally assisted relaxations occur preferably through the second (for 1) and the first (for 2-4) Kramer doublets. These interesting findings afford a new side-group effect to comprehensively understand the magnetostructural relationships and advance the rational design of high-performance Dy-SMMs.

Photo-oligomerization by shifting the coordination site in a luminescent coordination polymer.

A layered coordination polymer (CP) with the fine-tuned alignment of four diolefinic ligands has been designed by shifting the coordination site of the ligand. The trimeric and tetrameric cyclobutane derivatives were reversely achieved by the photoinitiated [2+2] cycloaddition of the CP due to the favorable Schmidt's distance. More interestingly, a dynamic fluorescence shift was observed during the photo-oligomerization and heat-cycloreversion of the CP system.

Encapsulated anion-dominated photocatalytic and adsorption performances for organic dye degradation and oxoanion pollutant capture over cationic Cu(i)-organic framework semiconductors.

Decontamination of industrial wastewater containing toxic organic dye molecules and oxoanions is urgently desirable for environmental sustainability and human health. Water-stable porous metal-organic frameworks (MOFs) have emerged as highly efficient photocatalysts and/or adsorbents for water purification through controllable integration of the constitutive requirements. To reveal the inclusion anion effect of microporous MOFs on wastewater treatment, two isostructural MOFs incorporating positive charge and semiconductive characteristics, {[Cu(tpt)]·3H2O·0.5SO4}n (1) and {[Cu(tpt)]·2H2O·ClO4}n (2, tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), have been synthesized and employed as dual-functional materials for both dye photodegradation and oxoanion removal. The two MOFs possess the same 3-fold interpenetrating cationic backbones but are encapsulated by highly disordered sulfate or perchlorate in the open channels. These included anions have significantly tuned the hydrophilicity of the channels, extended the visible-light absorption, optimized the bandgap and decreased the conduction band potential. Under the low-energy irradiation of a 30 W LED lamp, MOF 1 has selectively and efficiently degraded rhodamine B compared to 2 with accelerated kinetics, resulting from the stronger reduction ability and less migration resistance of the photogenerated electrons. Instead, MOF 2 can quickly capture harmful MnO4- and Cr2O72- by exchanging with the entrapped ClO4-, with maximum adsorption amounts of 557 and 168 mg g-1, respectively, under ambient conditions. The improved decolorization of the aqueous solution over 2 benefits essentially from the shape and charge memory effect and the smaller hydration energy of ClO4- than SO42-. These interesting observations highlight the importance of the included anions inside the porous MOF semiconductors on wastewater treatment.

Photocatalytic hydrogen evolution activity over Pt-assisted metal-organic frameworks dominated by transition metal ions and local coordination environments.

Three isostructural pillared-layer frameworks with M-BDC-X layers supported by ditopic HL connectors, [M(HL)(BDC)0.5X] n (HL = 4'-(4-hydroxyphenyl)-4,2':6',4″-terpyridine, BDC = terephthalate, M = Cd, X = Cl for (1), M = Cd, X = formate for (2), and M = Co, X = formate for (3)), were solvothermally synthesized, and used as photocatalysts for Pt-assisted visible-light-initiated hydrogen evolution from water splitting. These water-durable frameworks exhibit varied hydrogen production rates of 361.2, 271.3, and 327.5 µmol · g-1 · h-1 in 12 h due to their slightly different donor environments of the octahedral CdII and CoII ions. Further experimental and theoretical investigations reveal that the metal ions and the local coordination surroundings have essentially dominated the conduction band minimum and electric resistance of the charge transport, which play highly important roles for the improved catalytic hydrogen evolution ability. These findings demonstrate the electronic effect of the slightly ligand field modifications on the boosting hydrogen generation activity in the noble metal-assisted MOF photocatalytic systems.

Self-supported Co-doped FeNi carbonate hydroxide nanosheet array as a highly efficient electrocatalyst towards the oxygen evolution reaction in an alkaline solution.

The evolution of molecular hydrogen from electrochemical water splitting has currently emerged as one of the promising strategies to address the ever-increasing energy crisis and environmental pollution. The development of low-cost, highly efficient and long-term durable electrocatalysts is still challenging for practical large-scale water splitting applications. Herein, a highly crystallized Co-doped FeNi carbonate hydroxide nanosheet array was strongly grown on a conductive nickel foam (Co-FeNi CH/NF) and was used as an oxygen evolution reaction (OER) electrocatalyst. The ternary Co-FeNi CH/NF electrode exhibited an improved OER activity and good durability for at least 20 hours. The electrode delivered current densities of 10 and 500 mA cm-2 at extremely low overpotentials of 202 and 254 mV along with a small Tafel slope of 37.5 mV dec-1 in a 1.0 M KOH electrolyte solution. The incorporation of an equivalent amount of cobalt into the trigonal FeNi CH crystal lattice significantly increased the electrochemical active surface area and reduced the electron transport resistance by effectively regulating the electronic structure of the resultant electrocatalyst. These interesting observations highlight the importance of the subtle combinations of the active earth-abundant metals with electronic structure modulations.

A heterometallic sodium(i)-europium(iii)-organic layer exhibiting dual-responsive luminescent sensing for nitrofuran antibiotics, Cr2O72- and MnO4- anions.

The detection of nitrofuran antibiotics and toxic inorganic anions is currently necessary and challenging because their abuse and/or residuals have caused severe environmental pollution and illness. A heterometallic two-dimensional (2D) layered complex, {[Eu2Na(Hpddb)(pddb)2(CH3COO)2]·2.5(DMA)}n (1), was solvothermally synthesized and structurally and photophysically characterized. Pairs of acetate aggregated {Eu2Na(CH3COO)2} chains are periodically interconnected by V-shaped 4,4'-(pyridine-2,6-diyl)dibenzolate (pddb) linkers. More interestingly, the layered complex exhibits a bright red emission and can efficiently discriminate nitrofuran antibiotics by luminescent quenching with a strong quenching constant (Ksv) and low detection limit (LOD) of 4.93 × 104 M-1 and 0.64 µM for nitrofurazone, 4.42 × 104 M-1 and 0.68 µM for nitrofurantoin as well as 2.13 × 104 M-1 and 1.06 µM for furazolidone. Additionally, 1 can also probe trace amounts of toxic Cr2O72- and MnO4- anions with Ksv = 6.45 × 103 M-1 and LOD = 5.35 µM for Cr2O72- and Ksv = 2.84 × 103 M-1 and LOD = 5.99 µM for MnO4- anions. These interesting results indicate that heteromatallic coordination polymers can serve as favorable dual- or even multiple-responsive luminescence sensors to selectively recognize different kinds of contaminants.

An Ideal Detector Composed of Two-Dimensional Cd(II)-Triazole Frameworks for Nitro-Compound Explosives and Potassium Dichromate.

The two-dimensional (2D) metal-organic framework (MOF) [Cd(TPTZ)(H2O)2(HCOOH)(IPA)2]n (1; TPTZ = {4-[4-(1H-1,2,4-triazol-1-yl)phenyl]phenyl}-1H-1,2,4-triazole, IPA = isophthalic acid) has been constructed with the π-electron-rich aromatic ligand TPTZ, auxiliary ligand IPA, and the metal Cd(2+) ion with a d(10) configuration under solvothermal conditions. Complex 1 exhibits a strong ligand-originated photoluminescence emission, which is selectively sensitive toward electron-deficient nitroaromatic compounds, such as nitrobenzene (NB), 1,3-dinitrobenzene (m-DNB), and 1,4-dinitrobenzene (p-DNB), and nitro-aliphatic compounds, such as nitromethane (NM) and tris(hydroxymethyl)nitromethane. This property makes complex 1 a potential fluorescence sensor for these chemicals. Single-crystal X-ray diffraction studies revealed that dinuclear cadmium building units were further bridged by TPTZ ligands to give a four-connected uninodal net with the Schläfli symbol of [4.6(3).4.6(3).6(2).6(4)].

Cation-Exchange Porosity Tuning in a Dynamic 4d-4f-3d Framework for Ni(II) Ion-Selective Luminescent Probe.

A heterometallic complex {[Yb2(L)6Cd2][Cd(H2O)6]·6H2O}n (Yb-Cd) (H2L = oxidiacetic acid) was synthesized under hydrothermal conditions. In Yb-Cd, each L chelates to one Yb(3+) center and bonds to two Cd(2+) ions in an anti-anti configuration. Yb and Cd atoms are arrayed alternatively and connected by O-C-O bridges to form a cubic octahedral cage as the secondary building unit. Consequently, topological NaCl nets with high symmetry in the cubic space group Fd-3c have been constructed. The [Cd(H2O)6](2+) moieties lying in the porosity of anionic metal-organic framework (MOF) act as the thermodynamically stable species, required to balance the two negative charges of [Yb2(L)6Cd2](2-) in Yb-Cd. Interestingly, when Yb-Cd was employed as a precursor and emerged in the aqueous solution of Mn(ClO4)2·6H2O or Zn(ClO4)2·6H2O, a reversible single-crystal-to-single-crystal transformation process driven by [Cd(H2O)6](2+) cations has been exhibited to generate the heterotrimetallic coordination polymer {[Yb2(L)6Cd2][Mn(H2O)6]·6H2O}n (Yb-Cd-Mn) or {[Yb2(L)6Cd2][Zn(H2O)6]·6H2O}n (Yb-Cd-Zn). To the best of out knowledge, Yb-Cd-Mn and Yb-Cd-Zn are the first examples representing 4d-4f-3d polymers based on multicarboxylic acid. Luminescent studies reveal that Yb-Cd-Zn may serve as a good candidate of Ni(2+) a luminescent probe. To our knowledge, Yb-Cd-Zn represent the fist example of the 4d-4f-3d framework to exhibit luminescent selectivity for Ni(2+).

The effect of terminal groups of viologens on their binding behaviors and thermodynamics upon complexation with sulfonated calixarenes.

The binding modes, inclusion abilities, and thermodynamic parameters for the intermolecular complexation of p-sulfonatocalix[4]arene (SC4A), p-sulfonatocalix[5]arene (SC5A), and p-sulfonatothiacalix[4]arene (STC4A), with methyl viologen (MV(2+)), ethyl viologen (EV(2+)), propyl viologen (PV(2+)), butyl viologen (BV(2+)), and benzyl viologen (BnV(2+)), were systematically investigated by NMR spectroscopy, molecular mechanics calculation, and microcalorimetry in neutral aqueous solutions. The obtained results show that all the sulfonated calixarene hosts can form stable inclusion complexes with viologen guests driven by much favorable enthalpy changes. All the viologen guests are encapsulated into the smaller SC4A cavity in their axial orientation. The larger SC5A cavity can accommodate all the viologen guests at its upper-rim midsection in the latitudinal orientation. The binding modes of more flexible STC4A with the smaller MV(2+) and EV(2+) guests are similar to those of SC5A with the two guests, while the binding modes of STC4A with the larger PV(2+) and BV(2+) guests are similar to those of SC4A with the two guests. The host selectivity for all the investigated viologen guests is the same: SC5A > SC4A > STC4A. The magnitude of the host selectivity is associated with the size of the guest. Moreover, the thermodynamic origin of the host selectivity for these viologen guests can be explained well by host-guest binding modes.

Turn-on fluorescence and unprecedented encapsulation of large aromatic molecules within a manganese(II)-triazole metal-organic confined space.

For the purpose of investigating the coordination behavior of sterically congested alkenes and exploring the possibility of cofacial complexation in the polycyclic aromatic system for the formation of extended polymeric networks, a new tetradentate ligand, 1,1,2,2-tetrakis[4-(1H-1,2,4-triazol-1-yl)phenyl]ethylene (TTPE), has been designed and synthesized. By using TTPE as a building block with regard to the self-assembly with MnCl2 ⋅4 H2 O, a novel two-dimensional coordination framework {[Mn(TTPE)Cl2 ]⋅4 CHCl3 }n (1) can be isolated. Anion-exchange and organic-group-functionalized aromatic guest TTPE-loaded host-guest complex experimental results indicate that coordinated Cl(-) anions in the 2D framework of 1 can be completely replaced with dissociative ClO4 (-) groups in an irreversible single-crystal-to-single-crystal transformation fashion, as evidenced by the anion-exchange products of {[Mn(TTPE)(H2 O)2 ](ClO4 )2 ⋅0.5 TTPE⋅5.25 H2 O}n (2). Interestingly, TTPE, acting as an organic template, was encapsulated in the confined space of the 2D grid of 2. To the best of our knowledge, such large organic molecules encapsulated in the reactive organic-group-functionalized aromatic-guest-loaded host-guest complex are unprecedented up to now. Luminescence measurements illustrate that 1 and 2 represent novel examples of sensing materials based on triazole derivatives. Further, 2 has been demonstrated by tuning the fluorescence response of porous metal-organic frameworks as a function of adsorbed small analytes.

Cobalt(II), copper(II), zinc(II) and cadmium(II) complexes based on dibenzimidazolyl bidentate ligands with alkanyl linkers: crystal structure, weak interactions and conformations.

Eight metal complexes, {[Co(bibim-4)2(H2O)2](NO3)2}n (1), {[Cu(bibim-4)2(NO3)](NO3)}n (2), [Co(bibim-3)(TP)]n (3), [Zn2(bibim-3)]2(OAc)4] (4), [Co(bibim-2)(NO3)2]n (5), [Zn(bibim-4)(NO3)2]n (6), [Zn(bibim-4)(OAc)2]n (7) and [Cd(bibim-4)(NO3)2(DMF)]n (8) (bibim-2 = 1,2-bis(benzimidazol-l-yl)ethane, bibim-3 = 1,3-bis(benzimidazol-l-yl)propane, bibim-4 = 1,4-bis(benzimidazol-l-yl)butane and TP = terephthalate) have been prepared by means of the self-assembly of Co(II), Cu(II), Zn(II) or Cd(II) salts, dibenzimidazolyl bidentate ligands bearing alkanyl linkers and terephthalic acid. These complexes are structurally characterized by X-ray diffraction analyses. In complexes 1 and 2, 2D network layers with macrometallocycles are formed via metal centers and the ligand bibim-4. A 2D network layer with macrometallocycles in 3 is formed via Co(II) centers, the ligand bibim-3 and terephthalate molecules. In complex 4, a 20-membered macrometallocycle is formed by two bibim-3 ligands and two Zn(II) atoms. In complexes 5­8, 1D polymeric chains are formed via metal centers and the bibim-2 or bibim-4 ligands. In the crystal packings of complexes 1­8, 2D supramolecular layers and 3D supramolecular frameworks are formed via intermolecular weak interactions, including π­π interactions and hydrogen bonds. The different types of π­π interactions from the benzimidazole ring as well as the conformations of the ligands and metal complexes are described. Additionally, the fluorescence emission spectra of the ligands and metal complexes are reported.

1,4-Bis(4H-1,2,4-triazol-4-yl)benzene dihydrate.

The asymmetric unit of the title compound, C(10)H(8)N(6)·2H(2)O, comprises half the organic species, the mol-ecule being completed by inversion symmetry, and one water mol-ecule. The dihedral angle between the 1,2,4-triazole ring and the central benzene ring is 32.2 (2)°. The water mol-ecules form O-H⋯N hydrogen bonds with N-atom acceptors of the triazole rings. C-H⋯N hydrogen bonds are also observed, giving a three-dimensional framework.

Bis(2-amino-6-methyl-1,3-benzothia-zole-κN)bis-(4-nitro-benzoato-κO)zinc.

In the title mononuclear complex, [Zn(C(7)H(4)NO(4))(2)(C(8)H(8)N(2)S)(2)], the Zn(II) atom is coordinated by two N atoms from two 2-amino-6-methyl-1,3-benzothia-zole and by two carboxylate O atoms from two 4-nitro-benzoate ligands, adopting a slightly distorted tetra-hedral coordination geometry. In the crystal, inter-molecular N-H⋯O hydrogen bonds between the amino group of 2-amino-6-methyl-1,3-benzothia-zole and the carboxyl-ate group of 4-nitro-benzoate link these discrete mononuclear units into a one-dimensional supra-molecular chain extending parallel to [100].

Poly[aqua-bis-[µ(2)-2-(pyridin-4-ylsulfan-yl)acetato]-zinc].

The crystal structure of the title complex, [Zn(C(7)H(6)NO(2)S)(2)(H(2)O)](n), consists of extended layers parallel to (001) with 2-(pyridin-4-ylsulfan-yl)acetate ligands bridging the Zn(II) atoms. The Zn(II) atom shows a distorted penta-gonal-bipyramidal coordination environment. The Zn(II) and one O atom are situated on a crystallographic twofold rotation axis. In the crystal, intra-layer O-H⋯O hydrogen-bond inter-actions help to consolidate the coordination layer.

5-Chloro-1-phenyl-1H-tetra-zole.

The tetra-zole and phenyl rings of the title compound, C(7)H(5)ClN(4), form a dihedral angle 64.5°.

Tetra-aqua-bis-[2-(4-pyridyl-sulfan-yl)acetato-κN]nickel(II).

In the centrosymmetric title complex, [Ni(C(7)H(6)NO(2)S)(2)(H(2)O)(4)], the Ni(II) atom, located on a centre of inversion, is coordinated by two N atoms from two 2-(4-pyridyl-sulfan-yl)acetate ligands and four water O atoms in an octa-hedral geometry. In the crystal, inter-molecular O-H⋯O hydrogen bonds between the coordinated water mol-ecules and the carboxyl-ate group of the anionic 2-(4-pyridyl-sulfan-yl)acetate ligands link these discrete mononuclear units into a three-dimensional network.

Diaqua-bis-[5-(2-pyridyl-meth-yl)tetra-zol-ato-κN,N]zinc(II).

In the title mononuclear complex, [Zn(C(7)H(6)N(5))(2)(H(2)O)(2)], the Zn(II) atom, located on an inversion centre, is in a distorted octa-hedral coordination geometry formed by four N atoms from two chelating 5-(2-pyridyl-meth-yl)tetra-zolate ligands and two O donors from two water mol-ecules. Inter-molecular O-H⋯N hydrogen bonds between the coordinated water mol-ecule and the tetra-zolyl group of the 5-(2-pyridyl-meth-yl)tetra-zolate ligand lead to the formation of a three-dimensional network.

Benzimidazolium 3,5-dicarb-oxy-benzoate trihydrate.

Cocrystallization of benzimidazole with benzene 1,3,5-tricarb-oxy-lic acid in slightly basic medium afforded the title compound, C(7)H(7)N(2) (+)·C(9)H(5)O(6) (-)·3H(2)O, in which one of the imidazole N atom is protonated and one carb-oxy-lic group of aromatic acid is deprotonated. In the crystal structure, inter-molecular N-H⋯O hydrogen-bonding connects the two organic components into dimers, which are further linked into a three-dimensional network by O-H⋯O and N-H⋯O inter-actions between the water mol-ecules and the dimers.

Molecular tectonics of metal-organic frameworks (MOFs): a rational design strategy for unusual mixed-connected network topologies.

To systematically explore the higher-dimensional network structures with mixed connectivity, a series of two-dimensional (2D) and three-dimensional (3D) metal-organic frameworks (MOFs) with unusual (3,6)-connected net topologies are presented. These crystalline materials include [{[Mn(btza)2(H2O)2].2 H2O}n] (1), [{[Zn(btza)2(H2O)2].2 H2O}n] (2), [{[Cu(btza)2].H2O}n] (3), and [{[Cd(btza)2].3 H2O}n] (4), which have been successfully assembled through a predesigned three-connected organic component bis(1,2,4-triazol-1-yl)acetate (btza) with a variety of octahedral metal cores based on the modular synthetic methodology. The topological paradigms shown in this work cover the 2D CdCl2, 3D (4(2).6)2(4(4).6(2).8(7).10(2)), and pyrite (pyr) types. That is, when properly treated with the familiar first-row divalent metal ions, btza may perfectly furnish the coordination spheres for effective connectivity to result in diverse (3,6)-connected nets. Beyond this, a detailed analysis of network topology for all known 3D (3,6)-connected frameworks in both inorganic and inorganic-organic hybrid materials is described. Specific network connectivity of these MOFs indicates that the metal centers represent the most significant and alterable factor in structural assembly, although they show reliable and similar geometries. In this context, the combination of the distinct d10 AgI ion with btza in different solvents affords two isomorphous MOFs [{[Ag(btza)].glycol}n] (5) and [{[Ag(btza)]CH3OH}n] (6) with a binodal 4-connected 3D SrAl2 (sra) topology. The network structures of MOFs 1-3 and 5 turn out to be more complicated and interesting if one considers the hydrogen bonding between the host coordination frameworks and the intercalated solvent molecules. Furthermore, the role of the included solvents in the generation and stabilization of MOFs 1-6 is also investigated.