Electroswitching of the single-molecule magnet behaviour in an octahedral spin crossover cobalt(ii) complex with a redox-active pyridinediimine ligand.

Thermal-assisted spin crossover and field-induced slow magnetic relaxation coexist in the solid state for the mononuclear cobalt(ii) complex with the non-innocent 2,6-bis(N-4-methoxyphenylformimidoyl)pyridine ligand. One-electron oxidation of the paramagnetic low-spin Co ion (S = 1/2) to the diamagnetic low-spin Co ion (S = 0) leads to the electroswitching of the slow magnetic relaxation in acetonitrile solution.

Application of a Pillared-Layer Zn-Triazolate Metal-Organic Framework in the Dispersive Miniaturized Solid-Phase Extraction of Personal Care Products from Wastewater Samples.

The pillared-layer Zn-triazolate metal-organic framework (CIM-81) was synthesized, characterized, and used for the first time as a sorbent in a dispersive micro-solid phase extraction method. The method involves the determination of a variety of personal care products in wastewaters, including four preservatives, four UV-filters, and one disinfectant, in combination with ultra-high performance liquid chromatography and UV detection. The CIM-81 MOF, constructed with an interesting mixed-ligand synthetic strategy, demonstrated a better extraction performance than other widely used MOFs in D-µSPE such as UiO-66, HKUST-1, and MIL-53(Al).

Influence of Ligand Functionalization of UiO-66-Based Metal-Organic Frameworks When Used as Sorbents in Dispersive Solid-Phase Analytical Microextraction for Different Aqueous Organic Pollutants.

Four metal-organic frameworks (MOFs), specifically UiO-66, UiO-66-NH₂, UiO-66-NO₂, and MIL-53(Al), were synthesized, characterized, and used as sorbents in a dispersive micro-solid phase extraction (D-µSPE) method for the determination of nine pollutants of different nature, including drugs, phenols, polycyclic aromatic hydrocarbons, and personal care products in environmental waters. The D-µSPE method, using these MOFs as sorbents and in combination with high-performance liquid chromatography (HPLC) and diode-array detection (DAD), was optimized. The optimization study pointed out to UiO-66-NO₂ as the best MOF to use in the multi-component determination.

A green metal-organic framework to monitor water contaminants.

The CIM-80 material (aluminum(iii)-mesaconate) has been synthetized in high yield through a novel green procedure involving water and urea as co-reactants. The CIM-80 material exhibits good thermal stability with a working range from RT to 350 °C with a small contraction upon desolvation. Moreover, this material is stable in water at different pH values (1-10) for at least one week, and shows a LC value higher than 2 mg mL.

Insights in the analytical performance of neat metal-organic frameworks in the determination of pollutants of different nature from waters using dispersive miniaturized solid-phase extraction and liquid chromatography.

Five metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5(Zn), MIL-53(Al), UiO-64 and MOF-74(Zn) are synthesized, characterized, and utilized in a miniaturized solid-phase extraction method under dispersive mode (D-µSPE) for the determination of six pollutants of different nature, including one polycyclic aromatic hydrocarbon, two hormones, two drugs, and one disinfectant, from environmental waters (tap water and wastewater). A discussion of possible interactions justifying the partitioning of target analytes to the MOFs is included, considering not only the analytes' physicochemical characteristics but also those of MOFs: metal nature, structural environment of MOF pores, pore size and pore aperture widths, among others. MIL-53(Al) is selected for its versatility and high extraction efficiency for the target compounds.

Photoluminescent and Slow Magnetic Relaxation Studies on Lanthanide(III)-2,5-pyrazinedicarboxylate Frameworks.

In the series described in this work, the hydrothermal synthesis led to oxidation of the 5-methyl-pyrazinecarboxylate anion to the 2,5-pyrazinedicarboxylate dianion (2,5-pzdc) allowing the preparation of three-dimensional (3D) lanthanide(III) organic frameworks of formula {[Ln(2,5-pzdc)(HO)]·6HO} [Ln = Ce (1), Pr (2), Nd (3), and Eu (4)] and {[Er(2,5-pzdc)(HO)]·5HO} (5). Single-crystal X-ray diffraction on 1-5 reveals that they crystallize in the triclinic system, P1̅ space group with the series 1-4 being isostructural. The crystal structure of the five compounds are 3D with the lanthanide(III) ions linked through 2,5-pzdc dianions acting as two- and fourfold connectors, building a binodal 4,4-connected (4·68)(468)-mog network.

A magnetic-based dispersive micro-solid-phase extraction method using the metal-organic framework HKUST-1 and ultra-high-performance liquid chromatography with fluorescence detection for determining polycyclic aromatic hydrocarbons in waters and fruit tea infusions.

A hybrid material composed by the metal-organic framework (MOF) HKUST-1 and Fe3O4 magnetic nanoparticles (MNPs) has been synthetized in a quite simple manner, characterized, and used in a magnetic-assisted dispersive micro-solid-phase extraction (M-d-μSPE) method in combination with ultra-high-performance liquid chromatography (UHPLC) and fluorescence detection (FD). The application was devoted to the determination of 8 heavy polycyclic aromatic hydrocarbons (PAHs) in different aqueous samples, specifically tap water, wastewaters, and fruit tea infusion samples. The overall M-d-μSPE-UHPLC-FD method was optimized and validated.

The metal-organic framework HKUST-1 as efficient sorbent in a vortex-assisted dispersive micro solid-phase extraction of parabens from environmental waters, cosmetic creams, and human urine.

Three metal-organic frameworks (MOFs), specifically HKUST-1, MOF-5, and MIL-53(Al), have been synthetized, characterized, studied and compared in a vortex-assisted dispersive micro-solid-phase extraction (VA-D-µ-SPE) procedure in combination with high-performance liquid chromatography (HPLC) with diode-array detection (DAD) for determining seven parabens in environmental waters (tap water, swimming pool water, and water coming from a spa pool), human urine (from two volunteers), and cosmetic creams (two commercial brands). Experimental parameters, such as nature and amount of MOF, sample volume, nature of elution solvent and its amount, vortex and centrifugation time, among others, were properly optimized. HKUST-1 was the most adequate MOF to work with.

Two-dimensional 3d-4f heterometallic coordination polymers: syntheses, crystal structures, and magnetic properties of six new Co(II)-Ln(III) compounds.

Six new heterometallic cobalt(II)-lanthanide(III) complexes of formulas [Ln(bta)(H2O)2]2[Co(H2O)6]·10H2O [Ln = Nd(III) (1) and Eu(III) (2)] and [Ln2Co(bta)2(H2O)8]n·6nH2O [Ln = Eu(III) (3), Sm(III) (4), Gd(III) (5), and Tb(III) (6)] (H4bta = 1,2,4,5-benzenetretracaboxylic acid) have been synthesized and characterized via single-crystal X-ray diffraction. 1 and 2 are isostructural compounds with a structure composed of anionic layers of [Ln(bta)(H2O)2]n(n-) sandwiching mononuclear [Co(H2O)6](2+) cations plus crystallization water molecules, which are interlinked by electrostatic forces and hydrogen bonds, leading to a supramolecular three-dimensional network. 3-6 are also isostructural compounds, and their structure consists of neutral layers of formula [Ln2Co(bta)2(H2O)8]n and crystallization water molecules, which are connected through hydrogen bonds to afford a supramolecular three-dimensional network.

Synthesis, crystal structure, and magnetic characterization of the three-dimensional compound [Co2(cbut)(H2O)3]n (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid).

A novel cobalt(II) complex of formula [Co2(cbut)(H2O)3]n (1) (H4cbut = 1,2,3,4-cyclobutanetetracarboxylic acid) has been synthesized under hydrothermal conditions and its crystal structure has been determined by means of synchrotron radiation and neutron powder diffraction. The crystal structure of 1 consists of layers of cobalt(II) ions extending in the bc-plane which are pillared along the crystallographic a-axis through the skeleton of the cbut(4-) ligand. Three crystallographically independent cobalt(II) ions [Co(1), Co(2), and Co(3)] occur in 1.

Three new europium(III) methanetriacetate metal-organic frameworks: the influence of synthesis on the product topology.

Three new metal-organic framework structures containing Eu(III) and the little explored methanetriacetate (C7H7O6(3-), mta(3-)) ligand have been synthesized. Gel synthesis yields a two-dimensional framework with the formula [Eu(mta)(H2O)3]n·2nH2O, (I), while two polymorphs of the three-dimensional framework material [Eu(mta)(H2O)]n·nH2O, (II) and (III), are obtained through hydrothermal synthesis at either 423 or 443 K. Compounds (I) and (II) are isomorphous with previously reported Gd(III) compounds, but compound (III) constitutes a new phase.

Neutron diffraction studies of the molecular compound [Co2(bta)]n (H4bta =1,2,4,5-benzenetetracarboxylic acid): in the quest of canted ferromagnetism.

The exchange mechanism and magnetic structure of the organic-inorganic layered molecule-based magnet [Co2(bta)]n (1) (H4bta =1,2,4,5-benzenetetracarboxylic acid) have been investigated through variable-temperature magnetic susceptibility measurements and supported with a series of neutron diffraction experiments. Cryomagnetic studies have shown an antiferromagnetic ordering at a transition temperature of 16 K that is followed by the appearance of a weak ferromagnetism below 11 K. The weak antiferromagnetic interlayer interaction plays an important role in this system in spite of the long interlayer separation.

Dicopper(II) Metallacyclophanes with Electroswitchable Polymethyl-Substituted para-Phenylene Spacers.

Double-stranded anionic dinuclear copper(II) metallacyclic complexes of the paracyclophane type [Cu2L2](4-) have been prepared by the Cu(II)-mediated self-assembly of different para-phenylenebis(oxamato) bridging ligands with either zero-, one-, or four-electron-donating methyl substituents (L=N,N'-para-phenylenebis(oxamate) (ppba; 1), 2-methyl- N,N'-para-phenylenebis(oxamate) (Meppba; 2), and 2,3,5,6-tetramethyl- N,N'-para-phenylenebis(oxamate) (Me4ppba; 3)). These complexes have been isolated as their tetra-n-butylammonium (1 a-3 a), lithium(I) (1 b-3 b), and tetraphenylphosphonium salts (1 c-3 c). The X-ray crystal structures of 1 a and 3 c show a parallel-displaced π-stacked conformation with a smaller deviation from perpendicularity between the two benzene rings and the basal planes of the square planar Cu(II) ions when increasing the number of methyl substituents (average dihedral angles (ϕ) of 58.

Copper(II) assembling with bis(2-pyridylcarbonyl)amidate and N,N'-2,2-phenylenebis(oxamate).

We herein present the synthesis and X-ray structures of five copper(II) complexes of formulae [Cu(bpca)(CF3SO3)(H2O)]·H2O (1), [Cu(bpca)(Phpr)(H2O)]·3/2H2O (2), {[Cu(bpca)]2[Cu(opba)(H2O)]}·H2O (3), {[Cu(bpca)]2(H2opba)}2·6H2O (4) and [Cu(bpca)(EtH2opba)]n (5), where bpca = bis(2-pyridylcarbonyl)amidate, Phpr = 3-phenylpropionate, CF3SO3(−) = triflate (anion of the trifluoromethanesulphonic acid), H4opba = N,N′-1,2-phenylenebis(oxamic acid), and EtH3opba = monoethyl ester derivative of the H4opba. 1 and 2 are mononuclear copper(II) complexes where the copper atom is five-coordinate in distorted square pyramidal surroundings with a tridentate bpca and a water molecule (1)/carboxylate oxygen (2) building the basal plane and a triflate oxygen (1)/water molecule (2) filling the apical position. 3 is a neutral tricopper(II) complex where the [Cu(opba)(H2O)]2− unit acts as a bis-bidentate ligand toward two peripheral [Cu(bpca)]+ fragments.

Low-dimensional 3d-4f complexes assembled by low-spin [Fe(III)(phen)(CN)4]- anions.

The synthesis, crystal structure, and magnetic properties of four new mixed 3d-4f complexes with formulas [{Fe(III)(phen)(CN)(4)}(4)Gd(2)(III)(bpym)(NO(3))(2)(H(2)O)(4)]·2CH(3)CN·2H(2)O}(n) (1), [{Fe(III)(phen)(CN)(4)}(4)Tb(2)(III)(bpym)(H(2)O)(8)]·(NO(3))(2)·2CH(3)CN}(n) (2), [{Fe(III)(phen)(CN)(4)}(4)Sm(III)(bpym)(NO(3))(2)(H(2)O)(5)]·2CH(3)CN}(n) (3), and [{Fe(III)(phen)(CN)(4)}(2)Pr(2)(III)(bpym)()(NO(3))(4)(H(2)O)(2)](n) (4) (phen = 1,10-phenanthroline and bpym = 2,2'-bipyrimidine) are discussed here. Compounds 1-3 are isomorphous and their structure consists of neutral ladder-like motifs where the rungs are made up by bpym-bridged dilanthanide(III) cations and the rods are defined by [Fe(phen)(CN)(4)](-) units adopting a bis-monodentate coordination mode through two of its four cyanide ligands. The electroneutrality in this family is achieved by either a chelating [at the Gd(III) (1) and Sm(III) (3)] or free [at the Tb(III) (2)] nitrate group and a peripheral [Fe(phen)(CN)(4)](-) entity, which act as a monodentate ligand across one of its four cyanide groups toward the rare-earth cation (1-3).

[Fe(III)(dmbpy)(CN)4]-: a new building block for designing single-chain magnets.

We herein present the synthesis and magneto-structural study of a new family of heterobimetallic chains of general formula {[Fe(III)(dmbpy)(CN)(4)](2)M(II)(H(2)O)(2)}(n)·pnH(2)O [dmbpy = 4,4'-dimethyl-2,2'-bipyridine; M = Mn (2), Cu (3), Ni (4) and Co (5) with p = 4 (2), 3 (3), 9 (4) and 3.5 (5)] which were prepared by using the mononuclear PPh(4)[Fe(III)(dmbpy)(CN)(4)]·3H(2)O (1) building block (PPh(4)(+) = tetraphenylphosphonium) as a ligand toward fully solvated M(II) ions. The structure of 1 consists of discrete [Fe(III)(dmbpy)(CN)(4)](-) anions, tetraphenylphosphonium cations and noncoordinated water molecules.

Selective gas and vapor sorption and magnetic sensing by an isoreticular mixed-metal-organic framework.

A novel isoreticular oxamato-based manganese(II)-copper(II) open metal-organic framework H(2)O@iso1 featuring a pillared square/octagonal layer structure with alternating open and closed octagonal pores has been rationally prepared. The open-framework topology is responsible for a large selectivity in the separation of small gas (CO(2) over CH(4)) and vapor molecules (CH(3)OH over CH(3)CN and CH(3)CH(2)OH). H(2)O@iso1 displays a long-range three-dimensional ferromagnetic ordering with a drastic variation of the critical temperature as a function of the guest molecule [T(C) < 2.

Molecular engineering to control the magnetic interaction between single-chain magnets assembled in a two-dimensional network.

Two two-dimensional (2D) systems having the formula [{Fe(III)(dmbpy)(CN)(4)}(2)Co(II)L](n) [L = pyetNO (1), tvpNO (2)] and consisting of single-chain magnets connected through organic ligands (L) have been prepared, and their magnetic properties have been investigated. The overall magnetic behavior depends on the capacity of the organic pillars to transmit long-range magnetic interactions. 1 is the first example of a 2D compound exhibiting double relaxation of the magnetization, whereas 2 behaves as a metamagnet.

Redox switching of the antiferromagnetic coupling in permethylated dicopper(II) paracyclophanes.

A unique magnetic electroswitching behavior has been observed in an oxamato-based permethylated dicopper(II) paracyclophane; upon reversible one-electron oxidation of the double tetramethyl-substituted p-phenylenediamidate bridging skeleton, the spin alignment of the two Cu(II) ions (S(Cu) = ½) changes from antiparallel (OFF) to parallel (ON) in the resulting dicopper(II) π-radical cation species.

Solid-state aggregation of metallacyclophane-based Mn(II)Cu(II) one-dimensional ladders.

Two distinct one-dimensional (1) and two-dimensional (2) mixed-metal-organic polymers have been synthesized by using the "complex-as-ligand" strategy. The structure of 1 consists of isolated ladderlike Mn(II)(2)Cu(II)(2) chains separated from each other by neutral Mn(II)(2) dimers, whereas 2 possesses an overall corrugated layer structure built from additional coordinative interactions between adjacent Mn(II)(2)Cu(II)(2) ladders. Interestingly, 1 and 2 show overall ferri- and antiferromagnetic behavior, respectively, as a result of their distinct crystalline aggregation in the solid state.

Ligand effects on the dimensionality of oxamato-bridged mixed-metal open-framework magnets.

Increasing dimensionality [from 2D (1) to 3D (2)] and T(C) [from 10 (1) to 20 K (2)] in two new oxamato-bridged heterobimetallic Mn(II)(2)Cu(II)(3) open-frameworks result from the steric hindrance provided by the different alkyl substituents of the N-phenyloxamate bridging ligands.

Theoretical insights into the ferromagnetic coupling in oxalato-bridged chromium(III)-cobalt(II) and chromium(III)-manganese(II) dinuclear complexes with aromatic diimine ligands.

Two novel heterobimetallic complexes of formula [Cr(bpy)(ox)(2)Co(Me(2)phen)(H(2)O)(2)][Cr(bpy)(ox)(2)]·4H(2)O (1) and [Cr(phen)(ox)(2)Mn(phen)(H(2)O)(2)][Cr(phen)(ox)(2)]·H(2)O (2) (bpy = 2,2'-bipyridine, phen = 1,10-phenanthroline, and Me(2)phen = 2,9-dimethyl-1,10-phenanthroline) have been obtained through the "complex-as-ligand/complex-as-metal" strategy by using Ph(4)P[CrL(ox)(2)]·H(2)O (L = bpy and phen) and [ML'(H(2)O)(4)](NO(3))(2) (M = Co and Mn; L' = phen and Me(2)phen) as precursors. The X-ray crystal structures of 1 and 2 consist of bis(oxalato)chromate(III) mononuclear anions, [Cr(III)L(ox)(2)](-), and oxalato-bridged chromium(III)-cobalt(II) and chromium(III)-manganese(II) dinuclear cations, [Cr(III)L(ox)(μ-ox)M(II)L'(H(2)O)(2)](+)[M = Co, L = bpy, and L' = Me(2)phen (1); M = Mn and L = L' = phen (2)]. These oxalato-bridged Cr(III)M(II) dinuclear cationic entities of 1 and 2 result from the coordination of a [Cr(III)L(ox)(2)](-) unit through one of its two oxalato groups toward a [M(II)L'(H(2)O)(2)](2+) moiety with either a trans- (M = Co) or a cis-diaqua (M = Mn) configuration.

Slow relaxation of the magnetization in a 4,2-wavelike Fe(III)2Co(II) heterobimetallic chain.

The reaction of the low-spin iron(III) complex [Fe(dmbpy)(CN)(4)](-) (1) with fully solvated cobalt(II) ions affords the cyanide-bridged heterobimetallic chain {[Fe(III)(dmbpy)(CN)(4)](2)Co(II)(H(2)O)(2)}(n) · 4nH(2)O (2), which exhibits intrachain ferromagnetic coupling and double slow relaxation of the magnetization.

Reversible solvatomagnetic switching in a spongelike manganese(II)-copper(II) 3D open framework with a pillared square/octagonal layer architecture.

The concept of "molecular magnetic sponges" was introduced for the first time in 1999 by the creative imagination of the late Olivier Kahn. It refers to the exotic spongelike behavior of certain molecule-based materials that undergo a dramatic change of their magnetic properties upon reversible dehydration/rehydration processes. Here we report a unique example of a manganese(II)-copper(II) mixed-metal-organic framework of formula [Na(H(2)O)(4)](4)[Mn(4){Cu(2)(mpba)(2)(H(2)O)(4)}(3)]·56.