Dual-Functional Eu-Metal-Organic Framework with Ratiometric Fluorescent Broad-Spectrum Sensing of Benzophenone-like Ultraviolet Filters and High Proton Conduction

The construction of attractive dual-functional lanthanide-based metal-organic frameworks (Ln-MOFs) with ratiometric fluorescent detection and proton conductivity is significant and challenging. Herein, a three-dimensional (3D) Eu-MOF, namely, [Eu4(HL)2(SBA)4(H2O)6]·9H2O, has been hydrothermally synthesized with a dual-ligand strategy, using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L = H2O3PCH2-NC5H9-COOH) and 4-sulfobenzoic acid monopotassium salt (KHSBA = KO3SC6H4COOH) as organic linkers. Eu-MOF showed ratiometric fluorescent broad-spectrum sensing of benzophenone-like ultraviolet filters (BP-like UVFs) with satisfactory sensitivity, selectivity, and low limits of detection in water/ethanol (1:1, v/v) solutions and real urine systems. A portable test paper was prepared for the convenience of actual detection. The potential sensing mechanisms were thoroughly analyzed by diversified experiments. The synergistic effect of the forbidden energy transfer from the ligand to Eu3+, the internal filtration effect (IFE), the formation of a complex, and weak interactions between the KHSBA ligand and BP-like UVFs is responsible for the ratiometric sensing effect. Meanwhile, Eu-MOF displayed relatively high proton conductivity of 2.60 × 10-4 S cm-1 at 368 K and 95% relative humidity (RH), making it a potential material for proton conduction. This work provides valuable guidance for the facile and effective design and construction of multifunctional Ln-MOFs with promising performance.

Two Stable Cd-MOFs as Dual-Functional Materials with Luminescent Sensing of Antibiotics and Proton Conduction

Construction and investigation of dual-functional metal-organic frameworks (MOFs) with luminescent sensing and proton conduction provide widespread applications in clean energy and environmental monitoring fields. By selecting a phosphonic acid ligand 4-pyridyl-CH₂N(CH₂PO₃H₂)₂ (H₄L) and coligand 2,2'-biimidazole (H₂biim), two cadmium-based MOFs [Cd_1.5(HL)(H₂biim)_0.5] (1) and (H₄biim)_0.5·[Cd₂(L)(H₂biim)Cl] (2) with different structures and properties have been hydrothermally synthesized by controlling reaction temperature. Based on the excellent thermal and chemical stabilities, and good luminescent stabilities in water solution, 1 and 2 can serve as luminescent sensors of chloramphenicol (CAP) with different quenching constant (K_SV) values and detection limits (LODs) in water, simulated environmental system, and real fish water system. Meanwhile, different sensing effects and possible sensing mechanisms are analyzed in detail. Moreover, 1 and 2 can also serve as good proton-conducting materials. The proton conductivities can reach up to 1.41 × 10^-4 S cm^-1 for 1 and 1.02 × 10^-3 S cm^-1 for 2 at 368 K and 95% relative humidity (RH). Among them, 2 shows better luminescent sensing and proton conduction performance than 1, which indicates that different crystal structures have a great impact on the properties of MOFs. Through the discussion of the relationship between structures and properties in detail, the possible reasons for the differences in properties are obtained, which can provide theoretical guidance for the rational design of this kind of dual-functional MOFs in the future.

Dual-Functional Metal-Organic Framework for Luminescent Detection of Carcinoid Biomarkers and High Proton Conduction

It remains a challenge to exploit dual-functional metal-organic frameworks (MOFs) for applications, including luminescence detection and proton conduction. With the deliberate selection of the bifunctional organic ligand 5-sulfoisophthalic acid monosodium salt (NaH₂bts), and the phosphonic acid ligand N,N'-piperazine (bismethylenephosphonic acid; H₄L), a robust three-dimensional (3D) noninterpenetrating dual-functional MOF, [Tb(H₂L)(H₂bts)(H₂O)]·H₂O (1), has been synthesized hydrothermally. On the basis of the excellent thermal and chemical as well as superior luminescence stabilities in water and solutions with different pHs, 1 can serve as the simple, rapid, and highly selective and sensitive luminescence detection of the carcinoid biomarkers 5-hydroxytryptamine (HT) and its metabolite 5-hydroxyindole-3-acetic acid (HIAA) with detection limits of nanomolar magnitude in water and in simulated blood plasma and urine systems. Due to the change in the signals that could be readily differentiated by the naked eye under a UV lamp, a portable test paper has been developed. The probable quenching mechanisms are discussed in detail. In addition, a great number of hydrogen-bonding networks are formed among the uncoordinated carboxylic oxygen atoms, sulfonate oxygen atoms, protonated nitrogen atoms, and water molecules, which provide potential proton-hopping sites for proton conduction, leading to a maximum proton conductivity of 2.3 × 10^-4 S cm^-1 at 368 K and 95% relative humidity. The above results suggest that rationally designed dual-functional MOFs can open an avenue for the development of occupational diagnostic tools and alternative energy technology.

Assembly of tetra-nuclear YbIII-containing selenotungstate clusters: synthesis, structures, and magnetic properties

Two tetra-nuclear Yb^III-incorporated selenotungstate clusters, Keggin (C₂H₈N)₆Na₁₄[Yb₄Se₆W₄₄O₁₆₀(H₂O)₁₂]·40H₂O (1) and Wells-Dawson (C₂H₈N)₄Na₁₄[Yb₄Se₆W₄₅O₁₅₉(OH)₆(H₂O)₁₁]·38H₂O (2), have been isolated through a pH-controlled assembly, which exhibit the first Yb^III-containing polyoxotungstates with selenium heteroatoms. Their assemblies rely on the structure-directing effects of SeO₃^2- anion templates to give rise to available Se-containing Keggin-/Wells-Dawson-type motifs. Both compounds were characterized by single-crystal X-ray diffraction, IR spectroscopy, power X-ray diffraction (XRD), thermogravimetric analysis (TGA), X-ray photoelectron spectroscopy (XPS) as well as electrospray ionization mass spectrometry (ESI-MS). Furthermore, systematic magnetic studies revealed that 1 exhibits field-induced single-molecule magnetic behavior with a pre-exponential factor of τ₀ = 6.60(7) × 10^-8 s and a relaxation energy barrier of ΔE/k_B = 39.44(2) K, while 2 only displays antiferromagnetic interactions between the ytterbium centers.

Ferromagnetic Archimedean polyhedra {Fe24M18} (M = Fe, Ni, and Mn) with tunable electron configurations

Three symmetric nanocages {Fe24M18} that mimic the Archimedean polyhedra, namely pseudo-rhombicuboctahedron, were synthesized. Their electron configurations depend highly on the changes of metal ions and the deprotonation of auxiliary ligands.

Self-Assembly of Nanoscale Lanthanoid-Containing Selenotungstates: Synthesis, Structures, and Magnetic Studies

The reaction of mid-lanthanide (Ln) ions with the preformed {Se₆W₃₉} precursor under reasonably acidic aqueous conditions in the presence of organic amine cations results in an unprecedented nanoscale lanthanide-functionalized polyoxotungstate family, which are rare examples of mid-lanthanide-containing selenotungstates. (C₄H₁₀NO)₉Na₃[Dy₃Se_3.5W₃₀O_107.5(H₂O)₁₀]·22H₂O (1) and (NH₄)₃(C₂H₈N)Na₂[Dy₄Se₆W₃₈O₁₃₂(H₂O)₂₆(OH)₆]·18H₂O (2) reveal a trimeric Keggin assembly and a cyclic {Se₆W₃₈}-based chain, respectively, whereas (NH₄)₄Na₈[Gd₄Se₆W₄₈O₁₆₆(H₂O)₂₀(OH)₄]·21H₂O (3) and (NH₄)₉(C₂H₈N)₄Na₅[Ln₆Se₆W₅₈O₂₀₂(H₂O)₂₀(OH)₄]·58H₂O (4; Ln = Gd, Tb, or Dy) are a few examples of polyoxometalates consisting of both classical Keggin and Wells-Dawson building blocks, and (NH₄)₄(C₂H₈N)₅Na₁₃[Ln₄Se₈W₅₆O₁₉₆(H₂O)_x(OH)₁₀]·40H₂O (5; Ln = Gd, Tb, or Dy; x = 12 for Gd and Tb and 10 for Dy) features the largest "pure" Wells-Dawson selenotungstate {Se₈W₅₆} bearing a length of 3.73 nm. A library of Se-templated species involving the first reported Keggin {α-SeW₈} and Wells-Dawson {α-Se₂W₁₆} building blocks as well as some decisive assembly factors during the synthesis is responsible for these architectures. All of the compounds were structurally characterized in the solid and solution by single-crystal X-ray diffraction, IR, thermogravimetric-differential thermal analysis, and electrospray ionization mass spectrometry. Magnetic properties indicate that 1 and 4-Dy show probable single-molecule-magnet behavior with obvious frequency dependence, whereas 3 and 4-Gd present the antiferromagnetic interactions between the Gd^III centers.

Terbium Oxalatophosphonate as Efficient Multiresponsive Luminescent Sensors for Chromate Anions and Tryptophan Molecules

A stable 2D terbium oxalatophosphonate with green luminescence, namely, [Tb2(H3L)(C2O4)3(H2O)4]·2H2O (1), has been hydrothermally obtained by using (4-carboxypiperidyl)-N-methylenephosphonic acid (H3L) and oxalate ligand. The luminescent investigation indicates that the emission behavior of compound 1 shows high water and pH stabilities. It can be applied as a multiresponsive luminescent probe with high selectivity, high sensitivity, recycling capability, and fast sensing of CrO4 2-, Cr2O7 2- anions and tryptophan (Trp) molecules in aqueous solution through the luminescence quenching effect. Moreover, the sensing results can be distinguished by the naked eye under the irradiation of UV light of 254 nm. In addition, the probable mechanisms for the quenching behavior are also discussed, which can be mainly attributed to the competitive absorption of excitation energy between compound 1 and the analytes.

Manipulation of successive crystalline transformations to control electron transfer and switchable functions

Electron transfer in solid is crucial to switchable magnetic, electrical, optical and mechanical properties. However, it is a formidable challenge to control electron-transfer behaviors via manipulation of crystalline phases, especially through dynamic crystalline transformation. Herein, three crystalline phases of an {Fe2Co2} compound were obtained via enhancement of intermolecular π···π interactions inducing successive single-crystal-to-single-crystal transformations, from solvated 1·2CH3OH·4H2O, to desolvated 1 and its polymorph 1a accompanying electron transfer. 1·2CH3OH·4H2O showed thermally induced reversible intermetallic electron transfer in mother liquor. No electron-transfer behavior was observed in 1. 1a showed reversible intermetallic electron transfer upon thermal treatment or alternative irradiation with 808- and 532-nm lasers at cryogenic temperatures. The electron-transfer behaviors significantly change the magnetic and optical properties, providing a strategy to realize different electron-transfer behaviors and switchable functions via π···π interactions manipulated dynamic crystalline transformation.

Lanthanide oxalatophosphonates with two types of layered structures: syntheses, structures, luminescence and magnetic properties

Five novel lanthanide(iii) oxalatophosphonates with two types of 2D layered structures have been hydrothermally obtained and structurally characterized. The luminescence and magnetic properties of the title compounds have been studied.

Transition metal phosphonates with supramolecular structures: syntheses, structures, surface photovoltage and luminescence properties

Four new transition metal phosphonates with 2D and 3D supramolecular structures have been hydrothermally synthesized. The surface photovoltage and luminescence properties of the title compounds have also been studied.

Single-molecule magnet behavior in three cyano-bridged heterometallic Fe(III)-Ni(II) clusters

One trinuclear and two tetranuclear cyanide-bridged Fe(III)-Ni(II) complexes were synthesized via treatment of a tricyanometallate with divalent Ni salts in the presence of 1-butylimidazole, 2,2-bipyrimidyl and 1,10-phenanthroline, respectively. Magnetic property studies demonstrated that the three complexes exhibit single-molecule magnet behavior as a result of strong intracluster ferromagnetic coupling and weak intercluster magnetic interactions.

12-Metal 36-membered ring based WV–CoIIlayers showing spin-glass behavior

Two cyano-bridged bimetallic W^V–Co^IIlayers were synthesized, which contain 12 metal 36 membered rings and present spin-glass behavior.

Mixed-solvothermal synthesis, structures, surface photovoltage, luminescence and molecular recognition properties of three new transition metal phosphonates with 3D framework and supramolecular structures

Three new transition metal(ii) phosphonates have been synthesized under mixed-solvothermal conditions. Surface photovoltage and field-induced surface photovoltage spectroscopy of compounds 1 and 2 have been studied. Compound 3 could be used for the sensitive sensing of DMF.

Synthesis, structures, luminescent and molecular recognition properties of three new alkaline earth metal carboxyphosphonates with a 3D supramolecular structure

Three new alkaline earth metal carboxyphosphonates with a 3D supramolecular structure, namely, Ca[(H₃L)(H₂O)] (1), Sr[(H₃L)(H₂O)₂] (2) and Ba₂[(H₃L)₂(H₂O)₄] (3) have been hydrothermally synthesized. The luminescent and molecular recognition properties of compounds 1–3 were investigated.

Two novel cadmium(ii) carboxyphosphonates with 3D framework structure: synthesis, crystal structures, luminescence and molecular recognition properties

Two novel cadmium(ii) carboxyphosphonates with 3D framework structure have been synthesized under hydrothermal conditions. The luminescence properties and molecular recognition properties of the compounds have been investigated.

Synthesis, structures, surface photovoltage and luminescence properties of two new nickel(ii) carboxyphosphonates with a 3D framework structure

Two new 3D nickel(ii) carboxyphosphonates 1 and 2 were synthesized under hydrothermal conditions. The surface photovoltage and luminescent properties were studied.

Syntheses, structures, luminescence and molecular recognition properties of four new cadmium carboxyphosphonates with 2D layered and 3D supramolecular structures

Four new cadmium carboxyphosphonates with 2D layered and 3D supramolecular structure have been hydrothermally synthesized. Their luminescence and molecular recognition properties have been studied.

A series of novel lanthanide carboxyphosphonates with a 3D framework structure: synthesis, structure, and luminescent and magnetic properties

By introduction of 1,4-benzenedicarboxylic acid as the second organic ligand, a series of novel lanthanide carboxyphosphonates with a 3D framework structure, namely, [Ln(3)(H(2)L)(HL)(2)(bdc)(2)(H(2)O)]·7H(2)O (Ln = La (1), Ce (2), Pr (3), Nd (4), Sm (5), Eu (6), Gd (7), Tb (8); H(3)L = H(2)O(3)PCH(2)NC(5)H(9)COOH; H(2)bdc = HOOCC(6)H(4)COOH) have been synthesized under hydrothermal conditions. Compounds are isostructural and feature a 3D framework in which Ln(III) polyhedra are interconnected by bridging {CPO(3)} tetrahedra into 2D inorganic layers parallel to the ab plane. The organic groups of H(2)L(-) are grafted on the two sides of the layer. These layers are further cross-linked by the bdc(2-) ligands from one layer to the Ln atoms from the other into a pillared-layered architecture with one-dimensional channel system along the a axis. The thermal stability of compounds has been investigated. Luminescent properties of compounds , and the magnetic properties of compound have also been studied.

Hydrothermal synthesis, structures, and luminescent properties of zinc(II) and cadmium(II) phosphonates with a 3D framework structure using terephthalate as second linkers

By introduction of 1,4-benzenedicarboxylic acid as a second organic ligand, two new divalent metal(II) phosphonates with a 3D framework structure, namely, [Zn(HL1)(bdc)(0.5)] (1) and [Cd(1.5)(HL2)(bdc)(0.5)] (2) (H(2)L1 = H(2)O(3)PCH(NH(2))C(6)H(5), H(3)L2 = H(2)O(3)PCH(2)-NC(5)H(9)-COOH, H(2)bdc = HOOCC(6)H(4)COOH), have been synthesized under hydrothermal conditions. The two compounds show three-dimensional (3D) framework structure with infinite two-dimensional (2D) networks pillared by H(2)bdc. For compound 1, the {ZnO(4)} polyhedra are interconnected by phosphonate groups into a 2D layer, and the adjacent layers are further cross-linked via the bdc(2-) anions to generate a three-dimensional framework structure with two types of channel system along the c-axis. A notable feature of compound 1 is the presence of alternate left- and right-handed helical chains in the structure. In compound 2, the inorganic chains, composed of {Cd(1)O(7)}, {Cd(2)O(4)} and {CPO(3)} polyhedra, are linked by HL2(2-) ligands to form a double layer structure in the ab plane, and the adjacent layers are further linked by the bdc(2-) anions to form a 3D framework structure with one-dimensional channel systems along the a-axis. Luminescence properties of compounds 1 and 2 have also been studied.

A pulsed-leak valve for use with ion trapping mass spectrometers

A pulsed-leak valve that allows the introduction of a prolonged, flat, and controllable pulse of gas is described. Test results from the valve that utilized a Fourier transform ion cyclotron resonance mass spectrometer with Ar and C2H6 as the sample gases indicate that the valve functions as expected and yields basically rectangular pressure profiles in the cell region. The rise and fall times are similar to those of just the stand-alone pulsed valve and are believed to be determined mainly by the design of the vacuum system, rather than the design of the pulsed-leak valve. Kinetic data for the reaction of Nb(+) with C2H6, acquired with the use of the pulsed-leak valve to introduce the C2H6 gas, demonstrates the practical application of this valve for kinetic and other analogous studies. Use of the pulsed-leak valve greatly reduces the loss of the reactant ion signal during the cooling period.

An electrospray ionization mass spectrometry study of copper adducts of protonated ubiquitin

A study of the addition of Cu(II) to a ubiquitin electrospray solution shows that the copper ion in the ubiquitin remains doubly charged and displaces two protons on the protonated protein molecule. This observation indicates a chelating bond between the protein and the Cu(II) species. The addition of Cu(I) also was studied and significant intensity was observed for adducts with up to four Cu(I) species attached, with each Cu(I) bonded to one basic site on the protein.