Conversion from Heterometallic to Homometallic Metal-Organic Frameworks.

Two new heterometallic metal-organic frameworks (MOFs), LnZnTPO 1 and 2, and two homometallic MOFs, LnTPO 3 and 4 (Ln=Eu for 1 and 3, and Tb for 2 and 4; H3 TPO=tris(4-carboxyphenyl)phosphine oxide) were synthesized, and their structures and properties were analyzed. They were prepared by solvothermal reaction of the C3 -symmetric ligand H3 TPO with the corresponding metal ion(s) (a mixture of Ln3+ and Zn2+ for 1 and 2, and Ln3+ alone for 3 and 4). Single-crystal XRD (SXRD) analysis revealed that 1 and 3 are isostructural to 2 and 4, respectively. TGA showed that the framework is thermally stable up to about 400 °C for 1 and 2, and about 450 °C for 3 and 4. PXRD analysis showed their pore-structure distortions without noticeable framework-structure changes during drying processes. The shapes of gas sorption isotherms for 1 and 3 are almost identical to those for 2 and 4, respectively. Solvothermal immersion of 1 and 2 in Tb3+ and Eu3+ solutions resulted in the framework metal-ion exchange affording 4 and 3, respectively, as confirmed by photoluminescence (PL), PXRD, IR, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and energy-dispersive X-ray (EDX) analyses.

Luminescent Metal-Organic Framework Sensor: Exceptional Cd2+ Turn-On Detection and First In Situ Visualization of Cd2+ Ion Diffusion into a Crystal.

With regard to fluorescence quenching commonly observed during metal-ion detection, "turn-on" chemical sensing has been rarely reported, but could be extremely important because it facilitates the selective recognition of target objects of interest against a dark background. A metal-organic framework (MOF) chemosensor has been prepared that serves as an efficient platform for the selective detection of Cu2+ and Cd2+ ions over other metal ions. In particular, this framework shows the highest fluorescence enhancement (≈60-fold relative to Cd-free MOF) for the hazardous metal ion Cd2+ among luminescent MOFs and displays excellent reusability in repeated cycles. The direct diffusion of Cd2+ into the crystal pores has also been visualized for the first time.

Phase Transformation, Exceptional Quenching Efficiency, and Discriminative Recognition of Nitroaromatic Analytes in Hydrophobic, Nonporous Zn(II) Coordination Frameworks.

Five-fold interpenetrated Zn(II) frameworks (1 and 2) have been prepared, and an irreversible phase transformation from 1 to 2 is found to occur through a dissolution-recrystallization process. Compound 1 exhibits the highest quenching efficiency (>96%) for nitrobenzene at 7 ppm among luminescent coordination polymers. Selective discrimination of nitroaromatic molecules including o-nitrophenol (o-NP), p-nitrophenol (p-NP), 2,4-dinitrophenol (DNP), and 2,4,6-trinitrophenol (TNP) is realized in 1 and 2 as a result of the fact that the framework-analyte interaction affords characteristic emission signals. This observation is the first case of a nonporous coordination framework for such discriminative detection. Notably, significant hydrophobicity is evident in the framework 1 because of its surface roughness, which accounts for the enhanced quenching ability.

Control of Interchain Antiferromagnetic Coupling in Porous Co(II)-Based Metal-Organic Frameworks by Tuning the Aromatic Linker Length: How Far Does Magnetic Interaction Propagate?

Three MOF-74-type Co(II) frameworks with one-dimensional hexagonal channels have been prepared. Co(II) spins in a chain are ferromagnetically coupled through carboxylate and phenoxide bridges. Interchain antiferromagnetic couplings via aromatic ring pathways operate over a Co-Co length shorter than ∼10.9 Å, resulting in a field-induced metamagnetic transition, while being absent over lengths longer than ∼14.7 Å.

Adsorption of Carbon Dioxide on Unsaturated Metal Sites in M2 (dobpdc) Frameworks with Exceptional Structural Stability and Relation between Lewis Acidity and Adsorption Enthalpy.

A series of metal-organic frameworks (MOFs) M2 (dobpdc) (M=Mn, Co, Ni, Zn; H4 dobpdc=4,4'-dihydroxy-1,1'-biphenyl-3,3'-dicarboxylic acid), with a highly dense arrangement of open metal sites along hexagonal channels were prepared by microwave-assisted or simple solvothermal reactions. The activated materials were structurally expanded when guest molecules including CO2 were introduced into the pores. The Lewis acidity of the open metal sites varied in the order MnZn, as confirmed by C=O stretching bands in the IR spectra, which are related to the CO2 adsorption enthalpy. DFT calculations revealed that the high CO2 binding affinity of transition-metal-based M2 (dobpdc) is primarily attributable to the favorable charge transfer from CO2 (oxygen lone pair acting as a Lewis base) to the open metal sites (Lewis acid), while electrostatic effects, the underlying factor responsible for the particular order of binding strength observed across different transition metals, also play a role. The framework stability against water coincides with the order of Lewis acidity. In this series of MOFs, the structural stability of Ni2 (dobpdc) is exceptional; it endured in water vapor, liquid water, and in refluxing water for one month, and the solid remained intact on exposure to solutions of pH 2-13. The DFT calculations also support the experimental finding that Ni2 (dobpdc) has higher chemical stability than the other frameworks.

Switching of Slow Magnetic Relaxation Dynamics in Mononuclear Dysprosium(III) Compounds with Charge Density.

The symmetry around a Dy ion is recognized to be a crucial parameter dictating magnetization relaxation dynamics. We prepared two similar square-antiprismatic complexes, [Dy(LOMe)2(H2O)2](PF6) (1) and Dy(LOMe)2(NO3) (2), where LOMe = [CpCo{P(O)(O(CH3))2}3], including either two neutral water molecules (1) or an anionic nitrate ligand (2). We demonstrated that in this case relaxation dynamics is dramatically affected by the introduction of a charged ligand, stabilizing the easy axis of magnetization along the nitrate direction. We also showed that the application of either a direct-current field or chemical dilution effectively stops quantum tunneling in the ground state of 2, thereby increasing the relaxation time by over 3 orders of magnitude at 3.5 K.

Cost-Effective, High-Performance Porous-Organic-Polymer Conductors Functionalized with Sulfonic Acid Groups by Direct Postsynthetic Substitution.

We demonstrate the facile microwave-assisted synthesis of a porous organic framework 1 and the sulfonated solid (1S) through postsubstitution. Remarkably, the conductivity of 1S showed an approximately 300-fold enhancement at 30 °C as compared to that of 1, and reached 7.72×10-2  S cm-1 at 80 °C and 90 % relative humidity. The superprotonic conductivity exceeds that observed for any conductive porous organic polymer reported to date. This material, which is cost-effective and scalable for mass production, also revealed long-term performance over more than 3 months without conductivity decay.

Superprotonic conductivity of a UiO-66 framework functionalized with sulfonic acid groups by facile postsynthetic oxidation.

Facile postsynthetic oxidation of the thiol-laced UiO-66-type framework UiO-66(SH)2 enabled the generation of UiO-66(SO3 H)2 with sulfonic acid groups covalently linked to the backbone of the system. The oxidized material exhibited a superprotonic conductivity of 8.4×10(-2)  S cm(-1) at 80 °C and 90 % relative humidity, and long-term stability of the conductivity was observed. This level of conductivity exceeds that of any proton-conducting MOF reported to date and is equivalent to the conductivity of the most effective known electrolyte, Nafion.

Synthesis, structures, and magnetic properties of end-to-end azide-bridged manganese(III) chains: elucidation of direct magnetostructural correlation.

The two one-dimensional chain compounds [Mn(L1)(N3)]·H2O (1·H2O; H2L1 = 2,2'-((1E,1'E)-ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(phenylmethan-1-yl-1-ylidene)diphenol) and [Mn(L2)(N3)] (2; H2L2 = 2,2'-((1E,1'E)-2,2-dimethylpropane-1,3-diyl)bis(azan-1-yl-1-ylidene)-bis(phenylmethan-1-yl-1-ylidene)diphenol) bridged by single end-to-end azides were prepared via a self-assembly process. Each Mn(III) ion exhibits a characteristic Jahn-Teller elongation along the chain direction. For both compounds, antiferromagnetic interactions between Mn(III) spins within a chain are transmitted through the azide ligands, together with the apparent occurrence of spin canting at low temperatures. Remarkably, the coupling constants (J) for 1 and 2 exceed those reported for end-to-end azide-linked Mn(III) systems. A systematic magnetostructural relationship based on the torsion angle is established in terms of the torsion angle Mn-N(ax)···N(ax)-Mn (ax = axial) for the first time.

Humidity-triggered single-crystal-to-single-crystal structural transformations in a Zn(ii) coordination polymer displaying unusual activation energy change in proton conductivity.

Single-crystal-to-single crystal structural conversions occur in a Zn(ii) coordination polymer, uniquely induced by fine-tuned relative humidity. Proton conductivity depends on the number of hydrogen bonds in the structures. Slope change in the Arrhenius plot is uncommon among coordination-based conductors and associated with temperature-dependent phase changes.

Opioid analgesics are the leading cause of adverse drug reactions in the obstetric population in South Korea.

Medication use during pregnancy is gradually increasing; however, the safety of this practice remains largely unknown.We investigated medications with the most adverse drug reactions (ADRs) among pregnant women and the clinical features of those medications.Reports of ADRs among pregnant women were extracted from the Korea Adverse Events Reporting System (January 2012-December 2015). We analyzed the data of drugs frequently reported to cause ADRs and their clinical features among 3 age groups.A total of 5642 ADRs among 3428 patients were analyzed. The number of ADR reports increased annually. The most common drug categories causing ADRs were analgesics, followed by gynecologic, uterotocolytic, anti-infective, antidiabetic, analgesic, and antihypertensive drugs. Analgesics comprised 6 opioids (morphine, fentanyl, hydromorphone, oxycodone, tramadol, pethidine) and an anti-pyretics (nefopam and ketorolac). As an individual drug, ritodrine (24.4%) was the most frequently reported, followed by morphine, 5-HT3 serotonin antagonist, nefopam, fentanyl, magnesium sulfate, insulin lispro, cefazedone, sodium chloride, hydromorphone, oxycodone, cefotetan, nifedipine, human insulin, tramadol, ketorolac, pethidine, methylergometrine, metoclopramide, and misoprostol (in that order). ADRs most frequently occurred in women aged 25 to 34 years, and the trend of ADR with the 20 most commonly reported medications significantly differed among the age groups (P = .011). In addition, the kind of common causative drugs was different among the age groups.Knowledge of medications and clinical conditions resulting in the highest ADR rates among pregnant women is necessary for medical practitioners to administer proper care.

Reversible crystal-to-amorphous structural transformations and magnetic variations in single end-on azide-bridged MII (M = Mn, Ni) coordination polymers.

MII (M = Mn, Ni) coordination frameworks, singly linked by end-on azide ligands, were prepared by employing the long, flexible spacer ligand, p-XBP4. These two-dimensional layer structures underwent reversible crystal-to-amorphous phase transformations during the hydration-dehydration process. Moreover, the magnetic nature changes from antiferromagnetic to ferromagnetic coupling when moving from Mn to Ni.

Slow relaxation dynamics of a mononuclear Er(iii) complex surrounded by a ligand environment with anisotropic charge density.

Two sets of isostructural mononuclear compounds, [Ln(LOMe)2(H2O)2](PF6) [1, Ln = Er; 3, Ln = Gd; LOMe = CpCo{P(O)(O(CH3))2}3] and Ln(LOMe)2(NO3) (2, Ln = Er and 4, Ln = Gd), are synthesized by self-assembly of the respective lanthanide ions and tripodal chelate ligands. The Ln ions are encircled by two LOMe ligands, and two water molecules or one nitrate anion. Each octacoordinated Ln center adopts a distorted square antiprism geometry. The Er complex (2) chelated by a nitrate anion shows slow dynamics in magnetic relaxation, diagnostic of a single-ion magnet. Quantum tunneling in 2 is effectively blocked by application of an external field. Weak intermolecular magnetic interactions occur in 2, and are supported by the magnetic behavior of 4. Chemical dilution of Er with the diamagnetic Y ion can nullify magnetic interactions and suppress quantum tunneling. Generation of slow relaxation dynamics in the Er system is related to the anisotropic charge distribution supplied by the coordination of ligands with different charge densities, as observed in the Dy analogue. This suggests that magnetic anisotropy arises in a coordination system when an anisotropic lanthanide ion (Dy and Er) is surrounded by a ligand environment with anisotropic charge density, resulting in slow magnetic relaxation.

Tuning of chain chirality by interchain stacking forces and the structure-property relationship in coordination systems constructed by meridional FeIII cyanide and MnIII Schiff bases.

We synthesized six Fe(iii)-Mn(iii) bimetallic compounds by self-assembling the newly developed mer-Fe cyanide PPh4[Fe(Clqpa)(CN)3]·H2O (1) and PPh4[Fe(Brqpa)(CN)3]·H2O (2) with Mn Schiff base Mn(5-Xsalen)+ cations. These compounds include [Fe(Xqpa)(CN)3][Mn(5-Ysalen)]·pMeOH·qH2O [qpaH2 = N-(quinolin-8-yl)picolinamide; salen = N,N'-ethylenebis(salicylideneiminato) dianion; X = Cl, Y = H (3); X = Cl, Y = Br (4); X = Br, Y = H (5); X = Br, Y = F (6); X = Br, Y = Cl (7); X = Br, Y = Br (8)]. When precursor 1 was used, compounds 3 and 4 were isolated to give a dinuclear entity and a linear chain structure, respectively. The reaction of precursor 2 with the Schiff bases afforded four linear Fe(iii)-Mn(iii) chain complexes. Chain chirality with P- and M-helicity emerges in 4, 7, and 8, while 5 exhibits chain helicity opposite to the previous chain complexes and 6 presents no chain helicity. Such a structural feature is heavily dependent on the interchain π-π contacts and the Fe precursor bridging unit. Chiral induction from a local ethylenediamine link of Y-salen is propagated over the chain via noncovalent π-π interactions. All the bimetallic compounds show antiferromagnetic interactions transmitted by the cyanide linkage. A field-induced metamagnetic transition is involved in 4, 7, and 8, while a field-induced two-step transition is evident in 6. From a magnetostructural viewpoint, the coupling constant is primarily governed by the Mn-Nax-Cax angle (ax = axial) in the bimetallic chain complexes composed of mer-Fe(iii) tricyanides, although the torsion angle plays a role.

Exceptional CO2 working capacity in a heterodiamine-grafted metal-organic framework.

An amine-functionalized metal-organic framework (MOF), dmen-Mg2(dobpdc) (dmen = N,N-dimethylethylenediamine), which contains a heterodiamine with both primary and tertiary amines, was prepared via a post-synthetic method. This material exhibits a significant selectivity factor for CO2 over N2 that is commensurate with top-performing MOFs. It is remarkable that the solid is fully regenerated under vacuum or flowing Ar at low desorption temperatures, and following this can take up CO2 at more than 13 wt%. An exceptionally high working capacity is achieved at low regeneration temperatures and after exposure to humid conditions, which are important parameters for a real post-combustion CO2 capture process.