A new post-synthetic polymerization strategy makes metal-organic frameworks more stable.

Metal-organic frameworks are of interest in a number of host-guest applications. However, their weak coordination bonding often leads to instability in aqueous environments, particularly at extreme pH, and hence, is a challenging topic in the field. In this work, a two-step, post-synthetic polymerization method is used to create a series of highly hydrophobic, stable MOF composites. The MOFs are first coated with thin layers of polydopamine from free-base dopamine under a mild oxygen atmosphere, which then undergoes a Michael addition to covalently graft hydrophobic molecules to the external MOF surface. This easy, mild post-synthetic modification is shown to significantly improve the stability of a number of structurally diverse MOFs including HKUST-1 (Cu), ZIF-67 (Co), ZIF-8 (Zn), UiO-66 (Zr), Cu-TDPAT (Cu), Mg-MOF-74 (Mg) and MIL-100 (Fe) in wet, caustic (acidic and basic) environments as determined by powder X-ray diffraction and surface area measurements.

Recent Advances of MOFs and MOF-Derived Materials in Thermally Driven Organic Transformations.

Owing to the almost boundless structural tunability, MOF and MOF-derived catalysts have recently exhibited structures of higher complexity, and hence, have demonstrated activity in a wide array of organic transformations. These reactions have a broad range of important applications ranging from pharmaceuticals to agriculture. Given the increasing number of publications in the area, this Minireview is focused on the most recent advancements in thermally driven organic transformations using both MOFs, nanoparticle@MOF (NP@MOF) composites, and several classes of MOF-derived materials. The most recent advancements made in materials design and the utility of these materials in a broad range of reactions are discussed.

Efficient cleavage of aryl ether C-O linkages by Rh-Ni and Ru-Ni nanoscale catalysts operating in water.

Bimetallic Ru-Ni and Rh-Ni nanocatalysts coated with a phase transfer agent efficiently cleave aryl ether C-O linkages in water in the presence of hydrogen. For dimeric substrates with weaker C-O linkages, i.e. α-O-4 and ß-O-4 bonds, low loadings of the precious metal (Rh or Ru) in the nanocatalysts quantitatively afford monomers, whereas for the stronger 4-O-5 linkage higher amounts of the precious metal are required to achieve complete conversion. Under the optimized, relatively mild operating conditions, the C-O bonds in a range of substituted ether compounds are efficiently cleaved, and mechanistic insights into the reaction pathways are provided. This work paves the way to sustainable approaches for the hydrogenolysis of C-O bonds.

Metal-Organic-Framework-Derived Co3 S4 Hollow Nanoboxes for the Selective Reduction of Nitroarenes.

MOF-derived Co3 S4 /CN hollow nanoboxes (CN=nitrogen-doped carbon) was used to catalyze the chemoselective reduction of nitroarenes to anilines under mild reaction conditions with H2 as the reducing agent. The catalyst provides high conversion efficiencies and selectivities for a variety of nitroarene substrates that contain electron-donating or electron-withdrawing substituents under mild reaction conditions (in methanol at 60 °C). Further, the nanobox inhibits both dehalogenation and vinyl hydrogenation reactions, which are common limitations of state-of-the-art Pd-based catalysts. Because the reactions result in pure aniline products, the need for separation by column chromatography is eliminated. The resulting anilines are easily separated from the methanolic reaction solution in just three simple steps (centrifugation, decantation, and drying). If employed in industrial processes, catalysts of this kind would significantly reduce the amount of waste organic solvent generated and thus satisfy the need for sustainable chemical processes.

Selective CO2 adsorption by a new metal-organic framework: synergy between open metal sites and a charged imidazolinium backbone.

Metal-organic frameworks (MOFs) are porous, tunable crystalline materials that are attracting widespread scientific attention for their potential use in post-combustion CO2 capture. In this work, we report the synthesis of a new ligand, 1,3-bis(4-carboxyphenyl)-4,5-dihydro-1H-imidazol-3-ium tetrafluoroborate, H2Sp5-BF4, that is subsequently used for the construction of a novel MOF, Cu-Sp5-EtOH. This highly crystalline material has a charged framework that is expected to give rise to high CO2/N2 selectivity. However, the pores of the parent structure could not be accessed due to the presence of strongly coordinated ethanol molecules. After solvent exchange with methanol and subsequently heating Cu-Sp5-MeOH under vacuum, we are able to liberate the solvent providing other small molecules like CO2 access to the inside of the now porous structure, Cu-Sp5. The combination of open metal sites and framework charge leads to an exceptionally high CO2/N2 selectivity, as determined by Ideal Adsorbed Solution Theory (IAST) calculations performed on single-component adsorption isotherms. The CO2/N2 selectivity of Cu-Sp5 reaches a value of over 200 at pressures typically found in post-combustion flue gas (0.15 bar CO2/0.85 bar N2), a value that is among the highest reported to date.

Catalyst-Free Synthesis of Aryl Diamines via a Three-Step Reaction Process.

The formation of C-N bonds with aryl amines is one of the most widely studied reactions in organic chemistry. Despite this, it is still highly challenging, often requiring expensive, precious metal-based catalysts. Here we report an easy catalyst-free methodology for constructing C-N bonds. The method, which proceeds via the in situ formation of closed ring amidinium ions, allows the preparation of a series of symmetrical and/or unsymmetrical aryl diamines in notably high yields (82-98%) and purity and with a variety of different substituents. The methodology is shown successful for the preparation of aryl diamines having para- and/or meta-substituted carboxyl, nitro, bromo, methoxy, or methyl groups. This green synthetic pathway, which is catalyst free, requires only three steps, and proceeds without the need for purification. Further, it is a new sustainable, economically viable method to achieve an otherwise challenging bond formation.

MOF-Derived Cobalt Phosphide/Carbon Nanocubes for Selective Hydrogenation of Nitroarenes to Anilines.

Transition-metal phosphides have received tremendous attention during the past few years because they are earth-abundant, cost-effective, and show outstanding catalytic performance in several electrochemically driven conversions including hydrogen evolution, oxygen evolution, and water splitting. As one member of the transition-metal phosphides, Cox P-based materials have been widely explored as electrocatalyts; however, their application in the traditional thermal catalysis are rarely reported. In this work, cobalt phosphide/carbon nanocubes are designed and their catalytic activity for the selective hydrogenation of nitroarenes to anilines is studied. A high surface area metal-organic framework (MOF), ZIF-67, is infused with red phosphorous, and then pyrolysis promotes the facile production of the phosphide-based catalysts. The resulting composite, consisting of Co2 P/CNx nanocubes, is shown to exhibit excellent catalytic performance in the selective hydrogenation of nitroarenes to anilines. To the best of our knowledge, this is the first report showing catalytic activity of a cobalt phosphide in nitroarenes hydrogenation.

Nerve/Glial Antigen 2: A Novel Target for Anti-Tumor Therapy in Colorectal Cancer.

BACKGROUND/AIMS: To identify cell surface markers selectively expressed by tumor cells and tumor vasculature is the current goal for tumor therapy. One such marker is nerve/glial antigen 2 (NG2), which is a transmembrane glycoprotein. We aimed to investigate the expression of NG2 in colorectal cancer (CRC) and its association with clinicopathological parameters. METHODS: Immunohistochemical staining of NG2, vascular endothelial growth factor, and CD34 in 65 patients diagnosed with CRC over a 5-year period was performed. NG2 expression in both tumor cells and tumor vasculature was scored according to the German Reactive Scoring System. The association between NG2 and patient and tumor characteristics was analyzed. RESULTS: NG2 was expressed by tumor cells in 56.9%, tumor vasculature in 43%, and simultaneously by both in 27.6% of the cases. Tumor cell NG2 was more common in elderly patients (p = 0.023) and vascular NG2 was associated with better tumor differentiation (p = 0.035). Notably, vascular NG2 was expressed in half of the patients with left colon cancer, although it was not expressed in a majority of those with right colon cancer (50.9 vs. 17.7%, p = 0.041). CONCLUSION: Both tumor cell and vascular NG2 expression were shown to be present in a significant number of patients with CRC and this makes NG2 a double target for anti-tumor therapies. Such therapies might be more effective for elderly patients with well-differentiated left colon cancer.

Using Predefined M3(µ3-O) Clusters as Building Blocks for an Isostructural Series of Metal-Organic Frameworks.

Metal-organic frameworks (MOFs) have attracted much attention in the past decade owing to their unprecedented internal surface areas, tunable topologies, designable surfaces, and various potential applications. One bottleneck in the field regarding MOF synthesis is controlling the metal-containing secondary building unit (SBU) incorporated into the structure. In this work we report the synthesis and characterization of five trimeric [M3(µ3-O)(CH3CO2)6]x clusters (where M = Fe3+, Cr3+, Fe3+/Cr3+, Fe3+/Co2+, or Fe3+/Ni2+ and x = +1 or 0). The monocarboxylate capping ligand, acetate in this case, readily undergoes exchange with several difunctional counterparts, including 1,4-benzenedicarboxylic acid (H2-BDC) and biphenyl-4,4'-dicarboxylic acid (H2-BPDC), for the formation of an isostructural series of MOFs, several of which are newly reported (for M = Fe3+/Cr3+, Fe3+/Co2+, and Fe3+/Ni2+) and show excellent CO2 adsorption properties. In this report, a host of techniques including NMR, ICP, and ESI-MS are used to probe the ligand exchange process and composition of the SBUs, and XAS is used to monitor the Fe3+ and Cr3+ environment throughout the reactions, giving strong evidence that the clusters stay intact throughout the MOF synthesis. This work reveals that predefined SBUs is an effective means to create metal-substituted analogues of known frameworks. Further, CO adsorption and in situ IR are used to probe accessibility of the metals after solvent removal. We show for the first time that the incorporation of the neutral clusters, containing weaker Lewis acids like Ni2+ and Co2+, can promote the formation of open metal sites in the MOF frameworks, structural features known to enhance the binding energy of small guest molecules like CO2.

Thiazolium carbene catalysts for the fixation of CO2 onto amines.

The catalytic N-formylation and N-methylation of amines using CO2 as the carbon source represents a facile and sustainable approach for the synthesis of pharmaceuticals and natural products. Herein, we describe highly effective and inexpensive thiazolium carbene-based catalysts derived from vitamin B1 for the N-formylation and N-methylation of amines, using polymethylhydrosiloxane (PMHS) as a reducing agent, which operate under ambient conditions.

Free volume in ionic liquids: a connection of experimentally accessible observables from PALS and PVT experiments with the molecular structure from XRD data.

In the current work, free volume concepts, primarily applied to glass formers in the literature, were transferred to ionic liquids (ILs). A series of 1-butyl-3-methylimidazolium ([C4MIM](+)) based ILs was investigated by Positron Annihilation Lifetime Spectroscopy (PALS). The phase transition and dynamic properties of the ILs [C4MIM][X] with [X](-) = [Cl](-), [BF4](-), [PF6](-), [OTf](-), [NTf2](-) and [B(hfip)4](-) were reported recently (Yu et al., Phys. Chem. Chem. Phys., 2012, 14, 6856-6868). In this subsequent work, attention was paid to the connection of the free volume from PALS (here the mean hole volume, ) with the molecular structure, represented by volumes derived from X-ray diffraction (XRD) data. These were the scaled molecular volume Vm,scaled and the van der Waals volume V(vdw). Linear correlations of at the "knee" temperature ((T(k))) with V(m,scaled) and V(vdw) gave good results for the [C4MIM](+) series. Further relationships between volumes from XRD data with the occupied volume Vocc determined from PALS/PVT (Pressure Volume Temperature) measurements and from Sanchez-Lacombe Equation of State (SL-EOS) fits were elaborated (V(occ)(SL-EOS) ≈ 1.63 V(vdw), R(2) = 0.981 and V(occ)(SL-EOS) ≈ 1.12 V(m,scaled), R(2) = 0.980). Finally, the usability of V(m,scaled) was justified in terms of the Cohen-Turnbull (CT) free volume theory. Empirical CT type plots of viscosity and electrical conductivity showed a systematic increase in the critical free volume with molecular size. Such correlations allow descriptions of IL properties with the easily accessible quantity V(m,scaled) within the context of the free volume.

Making sense of enthalpy of vaporization trends for ionic liquids: new experimental and simulation data show a simple linear relationship and help reconcile previous data.

Vaporization enthalpy of an ionic liquid (IL) is a key physical property for applications of ILs as thermofluids and also is useful in developing liquid state theories and validating intermolecular potential functions used in molecular modeling of these liquids. Compilation of the data for a homologous series of 1-alkyl-3-methylimidazolium bis(trifluoromethane-sulfonyl)imide ([C(n)mim][NTf2]) ILs has revealed an embarrassing disarray of literature results. New experimental data, based on the concurring results from quartz crystal microbalance, thermogravimetric analyses, and molecular dynamics simulation have revealed a clear linear dependence of IL vaporization enthalpies on the chain length of the alkyl group on the cation. Ambiguity of the procedure for extrapolation of vaporization enthalpies to the reference temperature 298 K was found to be a major source of the discrepancies among previous data sets. Two simple methods for temperature adjustment of vaporization enthalpies have been suggested. Resulting vaporization enthalpies obey group additivity, although the values of the additivity parameters for ILs are different from those for molecular compounds.

Role of cytological characteristics of benign thyroid nodules on effectiveness of their treatment with levothyroxine.

INTRODUCTION: Levothyroxine (LT4) therapy has been used for the treatment of euthyroid nodular goiter, but there are controversial results about its usefulness. We aimed to evaluate the possible role of benign nodules' cytological characteristics in response to LT4 therapy. MATERIAL AND METHODS: In total, 93 patients with 128 nodules were included in the study; 74 of the nodules were treated with LT4 (group 1), and 54 of them had no medication (group 2). The subgroups consisted of adenomatous nodules, colloid nodules and cystic nodules. RESULTS: In group 1, mean thyroid volume and mean nodule volume were reduced significantly (p = 0.002 and p = 0.022, respectively) with low-normal level thyrotropin (TSH) suppression (between 0.3 mIU/ml and 1.0 mIU/ml), while there were no significant changes in group 2. When we evaluated changes of the initial and last nodule volumes in cytological subgroups, only colloid nodules in group 1 had significant reduction (p = 0.040) and the others had no significant changes. By omitting the colloid nodules, when the other nodules were revaluated, there were no significant changes in either group. CONCLUSIONS: On the basis of these results, obtained from a large sample of Anatolian patients, it is possible that LT4 therapy leads to significant reductions of both thyroid volume and nodule size in colloid nodules, but not in other kinds of benign nodules.

Free volume and phase transitions of 1-butyl-3-methylimidazolium based ionic liquids from positron lifetime spectroscopy.

Positron annihilation lifetime spectroscopy (PALS) was used to study a series of ionic liquids (ILs) with the 1-butyl-3-methylimidazolium cation ([C4MIM](+)) but different anions [Cl](-), [BF4](-), [PF6](-), [OTf](-), [NTf2](-), and [B(hfip)4](-) with increasing anion volumes. Changes of the ortho-positronium (o-Ps) lifetime parameters with temperature were observed for crystalline and amorphous (glass, supercooled, and normal liquid) states. Evidence for distinct phase transitions, e.g. melting, crystallization and solid-solid transitions, was observed in several PALS experiments. The o-Ps mean lifetime τ3 showed smaller values in the crystalline phase due to dense packing of the material compared to the amorphous phase. The o-Ps lifetime intensity I3 in the liquid state is clearly smaller than in the crystallized state. This behaviour can be attributed to a solvation of e(+) by the anions, which reduces the Ps formation probability in the normal and supercooled liquid. These phenomena were observed for the first time when applying the PALS technique to ionic liquids by us in one preliminary and in this work. Four of the ionic liquids investigated in this work ([BF4](-), [NTf2](-), [PF6](-) and [Cl](-) ILs) exhibit supercooled phases. The specific hole densities and occupied volumes of those ILs were obtained by comparing the local free volume with the specific volume from pressure-volume-temperature (PVT) experiments. From the o-Ps lifetime, the mean size vh of free volume holes of the four samples was calculated and compared with that calculated according to Fürth's hole theory. The hole volumes from both methods agree well. From the Cohen-Turnbull fitting of viscosity and conductivity against PALS/PVT results, the influence of the free volume on molecular transport properties was investigated.

Preparation of [Al(hfip)4](-)-based ionic liquids with siloxane-functionalized cations and their physical properties in comparison with their [Tf2N]- analogues.

Two new ionic liquids (ILs) with siloxane-functionalized cations and the weakly coordinating tetraalkoxyaluminate [Al(hfip)(4)](-) (hfip=hexafluoroisopropoxy) are prepared and characterized by nuclear magnetic resonance (NMR), infrared (IR) and Raman spectroscopy. With melting points below 0 °C they qualify as room temperature ILs (RTILs). Their temperature-dependent viscosities and conductivities, together with those of two [Tf(2)N](-) ILs with the same cations and a further siloxane-functionalized [Tf(2)N](-) IL, are measured between 0 and 80 °C, and all are described by the Vogel-Fulcher-Tammann (VFT) equations. We note that the [Al(hfip)(4)](-) ILs have lower viscosities than their [Tf(2)N](-) analogues at all measured temperatures and higher conductivities at room temperature.

Pheochromocytoma presented with vertebral artery dissection.

BACKGROUND: Pheochromocytoma may rarely cause arterial dissection. Here the authors report a patient with pheochromocytoma complicated with vertebral artery dissection (VAD) and stroke. CASE HISTORY: A 48-year-old man presented with probable diagnosis of myocardial infarction. Following premedication with methylprednisolone for coronary artery angiography, he had unstable hypertension. Three days later, he had right cerebellar and left occipital lobe infarction in association with VAD. Urinary cathecolamines and MR scan of the abdomen suggested a diagnosis of phaeochromocytoma, which was later histopathologically confirmed. CONCLUSION: This case is interesting in that there is no previous report of the combination of pheochromocytoma, VAD, and stroke. Awareness of the atypical clinical presentations of this tumor is important for definitive treatment.

Temperature dependence of the viscosity and conductivity of mildly functionalized and non-functionalized [Tf2N](-) ionic liquids.

A series of bis(trifluoromethylsulfonyl)imide ionic liquids (ILs) with classical as well as mildly functionalized cations was prepared and their viscosities and conductivities were determined as a function of the temperature. Both were analyzed with respect to Arrhenius, Litovitz and Vogel-Fulcher-Tammann (VFT) behaviors, as well as in the context of their molecular volume (V(m)). Their viscosity and conductivity are highly correlated with V(m)/T or related expressions (R(2) ≥0.94). With the knowledge of V(m) of new cations, these correlations allow the temperature-dependent prediction of the viscosity and conductivity of hitherto unknown, non- or mildly functionalized ILs with low error bars (0.05 and 0.04 log units, respectively). The influence of the cation structure and mild functionalization on the physical properties was studied with systematically altered cations, in which V(m) remained similar. The T(o) parameter obtained from the VFT fits was compared to the experimental glass temperature (T(g)) and the T(g)/T(o) ratio for each IL was calculated using both experimental values and Angell's relationship. With Walden plots we investigated the IL ionicity and interpreted it in relation to the cation effects on the physical IL properties. We checked the validity of these V(m)/T relations by also including the recently published variable temperature viscosity and conductivity data of the [Al(OR(F))(4)](-) ILs with R(F) =C(H)(CF(3))(2) (error bars for the prediction: 0.09 and 0.10 log units, respectively).

Na[B(hfip)4] (hfip = OC(H)(CF3)2): a weakly coordinating anion salt and its first application to prepare ionic liquids.

The fast, high yield synthesis and full characterization of Na[B(hfip)(4)] (hfip: OC(H)(CF(3))(2)) from NaBH(4) and hexafluoroisopropanol (hfipH) is presented. By anion metathesis, five [B(hfip)(4)](-) salts with classical/functionalized ionic liquid (IL) cations with melting points between 0 ([C(6)MIM](+)[B(hfip)(4)](-)) and 113 °C ([C(4)MMorph](+)[B(hfip)(4)](-)) were prepared. Four of these qualify as ILs and one as room temperature IL (RTIL). The properties of the borate anion [B(hfip)(4)](-) and its aluminum analogue [Al(hfip)(4)](-) were compared based on the available structural information from XRD. Viscosities (10.3 (90 °C) to 855 (0 °C) mPa s(-1)) and conductivities (0.603 (30 °C) to 4.844 (90 °C) mS cm(-1)) were measured between 0 and 90 °C, and described by the Vogel-Fulcher-Tammann (VFT) equations. The properties of the [B(hfip)(4)](-) ILs were analyzed in the context of the anion-dependent molecular volume V(m)-viscosity-/conductivity-correlations, also in comparison to ILs with [BF(4)](-)/[PF(6)](-), [N(CN)(2)](-), [Tf(2)N](-) and [Al(hfip)(4)](-) counterions. The viscosities and conductivities of [B(hfip)(4)](-) ILs are slightly inferior to [Al(hfip)(4)](-) ILs, similar to/better than all other anions given above. According to the Walden plots, the ionicity of the [B(hfip)(4)](-) ILs may at least be classified as "good". By sharp contrast to the [Al(hfip)(4)](-) ILs, the [B(hfip)(4)](-) ILs have good stability against humidity/water. Thus, handling of [B(hfip)(4)](-) ILs in an open laboratory atmosphere over hours and days is allowed and further facilitates the use of this new IL class.

In silico predictions of the temperature-dependent viscosities and electrical conductivities of functionalized and nonfunctionalized ionic liquids.

The viscosity (η) and electrical conductivity (κ) of ionic liquids are, next to the melting point, the two key properties of general interest. The knowledge of temperature-dependent η and κ data before their first synthesis would permit a much more target-oriented development of ionic liquids. We present in this work a novel approach to predict the viscosity and electrical conductivity of an ionic liquid without further input of experimental data. For the viscosity, only some basic physical observables like the Gibbs solvation energy (ΔG(solv)(*,∞)), which was calculated at the affordable DFT-level (RI-)BP86/TZVP/COSMO, the molecular radius, calculated from the molecular volume V(m) of the ion volumes, and the symmetry number (σ), according to group theory, are necessary as input. The temperature dependency (253-373 K) of the viscosity (4-19000 mPa s) was modeled by an Arrhenius approach. An alternative way, which avoids the deficits of the Arrhenius relation by a series expansion in the exponential term, is also presented. On the basis of their close connection, the same set of parameters is suitable to describe the electrical conductivity as well (238-468 K, 0.003-193 mS/cm). Nevertheless, more elegant alternatives like the usage of the Stokes-Einstein/Nernst-Einstein relation or the Walden rule are highlighted in this work. During this investigation, we additionally found an approach to predict the dielectric constant ε* of an ionic liquid at 298 K by using V(m) and ΔG(solv)(*,∞) between ε* = 9 and 43.

Synthesis of room-temperature ionic liquids with the weakly coordinating [Al(ORF)4]- anion (RF=C(H)(CF3)2) and the determination of their principal physical properties.

A large series of ionic liquids (ILs) based on the weakly coordinating alkoxyaluminate [Al(hfip)(4)](-) (hfip: hexafluoroisopropoxy) with classical as well as functionalized cations were prepared, and their principal physical properties determined. Melting points are between 0 ([C(4)MMIM][Al(hfip)(4)]) and 69 °C ([C(3)MPip][Al(hfip)(4)]); three qualify as room-temperature ILs (RTILs). Crystal structures for six ILs were determined; their structural parameters and anion-cation contacts are compared here with known ILs, with a special focus on their influence on physical properties. Moreover, the biodegradability of the compounds was investigated by using the closed-bottle and the manometric respirometry test. Temperature-dependent viscosities and conductivities were measured between 0 and 80 °C, and described by either the Vogel-Fulcher-Tammann (VFT) or the Arrhenius equations. Moreover, conductivities and viscosities were investigated in the context of the molecular volume, V(m). Physical property-V(m) correlations were carried out for various temperatures, and the temperature dependence of the molecular volume was analyzed by using crystal structure data and DFT calculations. The IL ionicity was investigated by Walden plots; according to this analysis, [Al(hfip)(4)](-) ILs may be classified as "very good to good ILs"; while [C(2)MIM][Al(hfip)(4)] is a better IL than [C(2)MIM][NTf(2)]. The dielectric constants of ten [Al(hfip)(4)](-) ILs were determined, and are unexpectedly high (ε(r)=11.5 to 16.8). This could be rationalized by considering additional calculated dipole moments of the structures frozen in the solid state by DFT. The determination of hydrogen gas solubility in [Al(hfip)(4)](-) RTILs by high-pressure NMR spectroscopy revealed very high hydrogen solubilities at 25 °C and 1 atm. These results indicate the significant potential of this class of ILs in manifold applications.