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By changing the transition metals (TMs) and polyanions, six polyoxometalate (POM)-based complexes 1–6 were synthesized by the hydrothermal method, namely [CdII(L1)2(HPMo12O40)]·2H2O (1), {MII2(H2O)4(L1)2[H2(β-Mo8O26)]}n·xH2O (n = 1, x = 1, M = Co (2), Cu (3), Fe (4); n = 0.5, x = 0, M = Ni (5), Zn (6)). The organic component 3,5-bis-(2,5-dihydro-imidazole-1-yl)benzoic acid (L1) is a tripodal ligand containing two imidazole and one carboxylic acid group. The N donors in the imidazole groups and the O donors in the carboxylic acid group of L1 can coordinate with different transition metal atoms to construct POM-based complexes. In complex 1, the Keggin anions are linked by [Cd(L1)2]2+ subunits to construct a chain. Complexes 2–6 are isostructural with [β-Mo8O26]4− anions linked by double metal–organic chains to build a 2D layer. The electrochemical behaviour and photocatalytic properties of these complexes were studied. These complexes can be used as amperometric sensors for the amperometric detection of Cr(VI), Fe(III) and H2O2. Moreover, these complexes can be used for fluorescence selective sensing of Cr3+. [ABSTRACT FROM AUTHOR]

By adding different proportions of N-butylimidazole and carboxyethylthiosuccinic acid (CETSA), three hybrid systems of ionic liquids were synthesized and named ILHS1, ILHS2 and ILHS3. Using the weight loss method, electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and contact angle test, it was determined that ILHS2 had the best corrosion inhibition among the three ionic liquid systems, and that the inhibition efficiency reached up to 90.63% when the concentration was 10 mM in 1 M HCl at 308 K. The adsorption isotherm was consistent with Langmuir adsorption, and combined with molecular dynamics simulation (MD), it was proved that mixed adsorption occurred on the metal interface. Polarization curves showed that the ionic liquid mixture systems could inhibit the corrosion of both poles, meaning that the anions and cations could act synergistically, and that the anions played a major role. The elemental and molecular structures of ILHS1, ILHS2 and ILHS3 were investigated using 1H NMR, which indicated that the three carboxyl groups on CETSA were regionally selective and combined with imidazole cations to form ionic liquid mixture systems. [ABSTRACT FROM AUTHOR]

Two 2,7-disubstituted spiro[fluorene-9,9′-xanthene] derivatives, 2,7-bis(4-(1-phenyl-1H-benzo[d]imidazol-2-yl)phenyl)spiro[fluorene-9,9′-xanthene] (SFX-2BI) and 2,7-bis(4-(1-(4-(tert-butyl)phenyl)-4,5-diphenyl-1H-imidazol-2-yl)phenyl)spiro[fluorene-9,9′-xanthene] (SFX-2IM), were synthesized by grafting imidazole-derived moieties with different electron-withdrawing abilities onto the 2- and 7-positions of a spiro[fluorene-9,9′-xanthene] (SFX) core. Their photophysical and electrochemical properties, thermal stability and electroluminescent properties were investigated. The results showed that these compounds have excellent thermal stability and exhibit strong deep-blue emission in dichloromethane solution. In addition, the vacuum-processed doped and non-doped devices based on SFX-2BI and SFX-2IM were fabricated, in which the device prepared using SFX-2BI as the emitting material exhibited the best device performance with a turn-on voltage of 5.5 V, a maximum brightness of 3984 cd m−2, a maximum current efficiency of 3.65 cd A−1 and a maximum external quantum efficiency of 2.61%. [ABSTRACT FROM AUTHOR]

Two cross-linkable iridium(III) complexes, Ir(L)2(acac) and Ir(L)2(Stpip), where L = 1-phenyl-2-(4′-vinyl-[1,1′-biphenyl]-4-yl)-1H-benzo[d]imidazole, acac = acetylacetonate, and Stpip = bis(diphenylphorothioyl)amide, were synthesized and characterized by elemental analysis, NMR (1H and 13C) spectroscopy and HRMS. The iridium(III) complexes exhibited excellent thermal stability and green–yellow emission with a maximum main peak at 563 nm. The photoluminescence quantum yields of Ir(L)2(acac) and Ir(L)2(Stpip) were 2.77% and 1.80%, respectively, in CH2Cl2 solution. The vacuum-processed electroluminescence device fabricated from Ir(L)2(acac) at 4 wt% doping concentration exhibited a maximum current efficiency (CEmax) of 26.3 cd A−1, a maximum brightness of 9645 cd m−2 and a maximum external quantum efficiency (EQEmax) of 14.7%. The solution-processed electroluminescence device based on Ir(L)2(acac) exhibited a maximum current efficiency (CEmax) of 3.71 cd A−1, a maximum brightness of 2237 cd m−2 and a maximum external quantum efficiency (EQEmax) of 1.36%. [ABSTRACT FROM AUTHOR]

In this paper, a rigid scaffold imposes the photophysics of chromophores with a benzylidene imidazolidinone core by mimicking the β-barrel structure of the green fluorescent protein (GFP) and its analogs. The designed artificial frameworks maintain fluorescence responses and, therefore, conformational rigidity of typically non-emissive GFP-related chromophores. To replicate a small weight percent of the chromophore inside the natural GFP, two synthetic approaches were utilized: coordinative immobilization and non-coordinative inclusion. Despite low chromophore loading in the rigid matrix, both approaches resulted in formation of photoluminescent hybrid materials. Furthermore, the rigid scaffold dictates chromophore fluorescence by replicating its behavior in solution or the solid state. The presented results open an avenue for utilization of rigid scaffolds in the engineering of materials with tunable photoluminescence profiles for a variety of practical applications.

The synthesis and anti-cancer activity evaluation of fused imidazoquinoline compounds is reported in this paper. Yb(OTf)3 has been utilized as a catalyst for the synthesis of 1,4-diaryl substituted imidazo[4,5-c]quinolines via a modified Pictet-Spengler approach. The desired imidazole ring was synthesized from imines using TosMIC (toluenesulfonylmethyl isocyanide) and subsequently functionalized at the C-4 position yielding an imidazoquinoline skeleton. Importantly, the final step was carried out without the aid of any prefunctionalization to obtain the resultant compounds in good yields. The synthesized compounds, when screened for anti-cancer activity, revealed the highest activity with 4-(2-bromophenyl)-1-phenyl-1H-imidazo[4,5-c]quinoline (IC50: 103.3 μM).

Considering the coordination advantage of N-heterocyclic carboxylate ligands in the construction of metal–organic frameworks (MOFs), we hope to adopt them to build up more structurally stable MOFs for proton conduction research. Therefore, the multifunctional ligand of 2-(2-carboxyphenyl)-4,5-imidazole dicarboxylic acid (o-CPH4IDC) was selected by us. Consequently, two highly water-stable Ba(II) and Cd(II) MOFs, {[Cd(o-CPH2IDC)(4,4′-bipy)0.5(H2O)2]·3H2O}n (1) (4,4′-bipy = 4,4′-bipyridine) and [Ba(o-CPH2IDC)]n (2) were made. The further study of water-assisted proton conduction for 1 and 2 demonstrated that both were temperature- and humidity-dependent proton conductors, and their best proton conductivities could reach 10−4 S·cm−1 at 100 °C and 98% RH. The vehicle mechanism can be proposed for 1 and 2 by calculating the activation energy and by analysing their crystal structures. Apparently, the adsorbed water molecules and carboxylate groups in the MOFs played an important role in the proton conduction process. Our work gives more choice for the design of novel proton conductive MOF materials. [ABSTRACT FROM AUTHOR]

Three novel cobalt metal–organic frameworks (Co-MOFs), namely, {[Co3(L)3(bip)]·2H2O}n (1), [Co(L)(bibp)0.5]n (2) and [Co(L)(bbi)0.5]n (3) (H2L = 3-(3,5-dicarboxylphenoxy)pyridine, bip = 3,5-bis(1-imidazoly)pyridine, bibp = 4,4′-bis(imidazol-1-yl)biphenyl, bbi = 1,1′-(1,4-butanediyl)bis(imidazole)) have been successfully synthesized by a solvothermal method. Various auxiliary second ligands and different solvents led to the diversity of three Co-MOFs. Topological analysis exemplified 7-nodal (3,3,4,4,4,5,5)-connected net for 1, (3,5)-connected binodal net for 2, and (3,4)-connected binodal net for 3. The ability of MOFs 1–3 to remove dyes has been explored and among them, 1 could remove congo red (CR) dye with efficiency, selectivity and maintain excellent performance in various mixed dyes. The evaluation parameters, including adsorption capacity, reusability, adsorption isotherms and adsorption thermodynamics have been performed to investigate the adsorption of MOF 1. A possible mechanism has been studied through infrared spectroscopy and XPS analysis, and the chemical actions (hydrogen bonds and π–π stacking interactions) contributed much to the adsorption process. According to cyclic voltammetry (CV) experiments, MOFs 1–3 exhibited potential electrocatalytic water oxidation performances. Direct-current (dc) magnetic susceptibility of 1–3 indicated the presence of dominant antiferromagnetic coupling, which revealed their potential values in information storage, processing and transmission. [ABSTRACT FROM AUTHOR]

A series of stimuli-responsive AIEgens of tetraphenylethylene (TPE) fused imidazole derivatives (1–7) were synthesized, and their substituent controlled fluorescence properties in the solid state were explored. The structure of the synthesised compounds was characterized by NMR, mass and single crystal X-ray diffraction spectroscopy techniques. 1–7 exhibited a typical aggregation induced emissive (AIE) behaviour in the THF : water mixture. These compounds exhibited substituent dependent strong solid state fluorescence (Φf = 16.6–55.7%) with a tunable λmax between 458 and 496 nm. Chlorine substituted 6 showed the highest fluorescence efficiency (Φf = 55.7%), whereas acetyl substituted 3 exhibited the lowest fluorescence efficiency (Φf = 16.6%). All the seven compounds showed a mechanical pressure induced reversible fluorescence switching. Crushing 1–7 resulted in red shifted fluorescence, which was reversed to its initial state by heating/solvent vapour exposure. Interestingly, integration of 1–7 into a hydrophobic PMMA polymer resulted in blue shifted fluorescence at 470 nm, whereas that into hydrophilic PVA polymer resulted in red shifted fluorescence at 491 nm. Thus highly solid state emissive TPE fused imidazole compounds were prepared, and their stimuli-induced reversible fluorescence switching and polymer controlled tunable fluorescence were demonstrated. [ABSTRACT FROM AUTHOR]

With increasing industrial development, heavy metal ions have been widely released, and fluorescence detection is an effective approach owing to its high selectivity and sensitivity. Herein, a water-soluble luminescent sensor based on a spirobifluorene-based imidazolium polymer (IMSPF-Br-COOH) is developed from tetraimidazole spirobifluorene and 3-bromo-2-bromomethylpropionic acid through a quaternization reaction. IMSPF-Br-COOH has an imidazolium cationic network and carboxyl coordination groups. Consequently, fluorescence quenching of IMSPF-Br-COOH exhibits high selectivity for Fe3+ and Cr2O72−via coordination and anion exchange. The corresponding quenching coefficient (Ksv) is 2.0772 × 103 L mol−1 for Fe3+ and 1.0081 × 104 L mol−1 for Cr2O72−. The detection limit (LOD) is calculated to be 170.56 μmol L−1 for Fe3+ and 100.81 μmol L−1 for Cr2O72−. This work provides a novel approach for metal ion detection by water-soluble polymers. [ABSTRACT FROM AUTHOR]

Laser ignition of explosives is believed to be a safe and reliable initiation method to trigger the reaction of energetic materials. Energetic complexes including most primary explosives are a class of important explosives. The determinant of the laser initiation threshold of energetic complexes is still unclear. The coordination metal ions have a significant influence on the properties of energetic complexes. However, the effect of metal ions on the laser ignition ability has not attracted enough attention. To inspect the influence of alkali and alkaline earth metal ions on the laser initiation ability of energetic complexes, sodium(I) (1), potassium(I) (2), magnesium(II) (3), calcium(II) (4), and barium(II) (5) containing energetic complexes based on the ligand 4,4′,5,5′-tetranitro-2,2′-biimidazole (TNBI) were prepared. The crystal structures and thermal behaviors of four new complexes (1, 3, 4, and 5) were characterized. Laser initiation tests were carried out using different laser energy densities. TNBI and all complexes could be initiated and they all exhibited deflagration processes. It is found that the initiation delay times have a definite relationship with the metal ion type. Two alkali metal-containing complexes were easy to initiate, followed by the ligand TNBI, whereas the alkaline earth metal-containing complexes showed longer initiation delay times. [ABSTRACT FROM AUTHOR]

Creating more exposed active sites on the metal–organic framework (MOF) surface is crucial for enhancing the recognition ability of MOF artificial receptors. Here, a copper-based MOF Cu(im)2 (im = imidazole) was utilized to act as an artificial receptor, inhibiting the activity of α-chymotrypsin. The shortest diazole ligand reduced the distance between regenerative copper sites, creating as many active sites as possible on the MOF unit surface. The amount of copper(II) centers on the Cu(im)2 surface was calculated to be 4.96 × 106 μm−2. Thus, Cu(im)2 showed exceedingly higher inhibition performance than other copper-based MOFs. The ChT activity was almost inhibited (88.8%) after the incubation with only 20 μg mL−1 Cu(im)2 for 10 min. The binding between ChT and Cu(im)2 was very fast with high affinity. Further results proved that Cu(im)2 inhibited the activity of ChT through electrostatic interactions and coordination interactions via the mixed inhibition mode. This strategy to use short ligands to create more active sites on the MOF surface provides a new direction to enhance the inhibition efficiency. [ABSTRACT FROM AUTHOR]

An amazing and stable carbonized octahedral frame material Cu-PC@OFM was synthesized and characterized through HRTEM, SEM, XRD, XPS, and Raman spectroscopy and nitrogen adsorption/desorption analysis. In particular, the carbon matrix carrier loaded with nano-copper not only maintains the original structure, but also the nano copper particles generated in situ significantly improve the catalytic performance and stability. It was disclosed that the copper-based catalyst material Cu-PC@OFM showed high catalytic activity in the borrowing hydrogen reaction and the synthesis of 1-benzyl-2-aryl-1H-benzo[d]imidazole derivatives with high yields in water. This copper catalytic system provided a much greener and efficient catalyst for the synthesis of functionalized amines and 1-benzyl-2-aryl-1H-benzo[d]imidazoles with good recovery performance in water, which was the first example for the Cu-PC@OFM material-catalyzed synthesis of 1-benzyl-2-aryl-1H-benzo[d]imidazoles. In addition, a plausible reaction mechanism was proposed through some condition control experiments, deuterium labeling experiments and separation of intermediates experiments. [ABSTRACT FROM AUTHOR]

Eight Cu(II) coordination compounds with cyclic triimidazole, triimidazo[1,2-a:1′,2′-c:1′′,2′′-e][1,3,5]-triazine (L1), its positional isomer, triimidazo[1,2-a:1′,2′-c:1′′,5′′-e][1,3,5]-triazine (L2), and two pyridine derivatives of L1, 3-(pyridin-2-yl)triimidazo[1,2-a:1′,2′-c:1′′,2′′-e][1,3,5]triazine (L3) and 3-(pyridin-4-yl)triimidazo[1,2-a:1′,2′-c:1′′,2′′-e][1,3,5]triazine (L4) are reported. All compounds represent neutral Cu(II) discrete complexes or coordination polymers comprising luminophore triimidazole molecules and charge-compensated anions. Starting from copper(II) acetate monohydrate with the paddle-wheel geometry, two binuclear complexes [Cu2(CH3COO)4(L1)2] (1) and [Cu2(CH3COO)4(L3)2] (2), a mixed-dimensional 0D/1D coordination compound {[Cu2(CH3COO)4(L2)]2[Cu2(CH3COO)4(H2O)(L2)]·2(H2O)}n (3), all with binuclear paddle-wheel [Cu2(CO2)4] secondary building units, and a mononuclear complex [Cu(CH3COO)2(L2)2] (4) with square-planar N2O2 Cu(II) coordination, were obtained. Starting from copper(II) nitrate trihydrate, three mononuclear complexes [Cu(NO3)2(L2)4]·2CH3CN (5), [Cu(NO3)2(L2)4]·1.5(dmf) (6), and [Cu(NO3)2(H2O)2(L4)2]·2H2O (7) with Cu(II) distorted octahedral N4O2 and N2O4 coordination cores, and 1D coordination polymer [Cu(NO3)2(L3)]n (8) with the distorted square pyramidal N2O3 Cu(II) coordination geometry were obtained. In the mono- and binuclear complexes, luminophores L1–L4 coordinate as monodentate terminal ligands. In the coordination chain 3 the L2 ligand acts as a bidentate-bridging exo-ligand, while in 8 the L3 ligand acts as a bidentate-chelate one, and the structure extension to 1D is achieved via the bridging nitrate-anions. The compromise between the hydrogen bonds and π⋯π stacking interactions defines the stacking patterns of bulky luminophores coordinated to the metal center that vary from the dimeric associates to the infinite 2D motifs with the different overlapping areas of the stacking ligands. The strong aggregation-induced emission demonstrated by pure luminophores was nearly quenched in the reported Cu(II) coordination compounds in the solid state. [ABSTRACT FROM AUTHOR]

Bismuth SBA-16 catalyst was synthesized by the hydrothermal method. Four kinds of p-toluenesulfonic acid functionalized imidazole ionic liquids were prepared by a two-step method and their molecular structures were characterized by 1H NMR and MS. The post-synthesis impregnation method was used to functionalize the Bi(10)-SBA-16 silicon mesoporous material with the ionic liquids and the obtained materials were characterized by FT-IR, XRD, BET, XPS, and TG. The results show that the volume and pore size of SBA-16 were changed by loading Bi and ionic liquids, while the three-dimensional cubic pore structure of SBA-16 was not destroyed. The composite catalyst was evaluated in Friedel–Crafts acylation of anisole with acetic anhydride. The effects of reaction temperature and the ratio of anisole and acylating agent on the acylation of anisole were investigated by experimental design. The results showed that 1.2ILc@Bi(10)-SBA-16 was used as the catalyst, the conversion of anisole was 85.41% and the yield of aromatic ketone was 69.19% under the conditions of a reaction temperature of 100 °C, a catalyst dosage of 0.5 g, a time period of 4 h and a molar ratio of 1 : 1.5. After 5 recycling runs, the reduction in the overall ratio of reactant conversion and product yield did not exceed 7.5%, indicating that 1.2ILc@Bi(10)-SBA-16 has good stability and reusability. [ABSTRACT FROM AUTHOR]

Luminescent materials with aggregation-induced emission enhancement (AIEE) have received increasing attention as chemosensors. Four AIEE active imidazole derivatives with TPA moieties, M-MAP, M01-DMAC, M-IF, and M01-IF, have been developed for the sensitive detection of NAC explosives. The luminescence behaviors of compounds were systematically measured. In 90% THF/H2O, 100–200 nm aggregated nanoparticles were formed with good regularity and stability. The intramolecular free rotations were restricted and emissions were enhanced within the aggregated state. The fluorescence of aqueous AIEE dispersions showed sensitive quenching by picric acid (PA), and the LOD was determined to be 30.99 nM for M-MAP. The intermolecular PIET mechanism was responsible for recognition and sensitive detection. Moreover, their AIEE luminescence behaviors respond weakly to other nitroaromatic compounds (NACs) or analogs. The quenching efficiencies, for M-MAP and M01-MAP, were almost consistent with the risk degrees of NACs. The test strips were easily prepared and the emission quenching effect was simply observed after contacting NACs. The potential of our new AIEEs was demonstrated for the fabrication of convenient and easily operating sensors for NACs. [ABSTRACT FROM AUTHOR]

We report the results of a series of molecular dynamics simulations on a number of zinc zeolitic imidazolate framework (ZIF) structures together with some lattice dynamics calculations on ZIF-4, providing information about the flexibilities of these structures. The simulations have used a force field we developed based on ab initio calculations of clusters of ligands and metal cations. We have shown that there are instabilities of the structures of some ZIF structures at low temperatures and high pressures. A rigidity analysis based on the Rigid Unit Mode model shows considerable degree of network flexibility, including a significant elastic flexibility. [ABSTRACT FROM AUTHOR]

A new intramolecular charge transfer (ICT) based fluorescent turn-on ratiometric probe 2(D–π–A type) has been designed and synthesized by bridging imidazole (donor, D) and benzothiazole (acceptor, A) moieties through a phenyl ring. The photophysical behavior of probe 2in solvents of different polarities and at different pH values has been investigated. Upon interaction with different types of anions probe 2showed selective high affinity for fluoride anions (F−) in aqueous DMSO (20%) solution. The ratiometric fluorescence turn-on behavior displayed by 2with F−is attributed to changes in the ICT process. Job's plot analysis revealed a 1 : 1 binding stoichiometry for 2+ F−interactions with a high binding constant and detection sensitivity (30 ppb). Moreover, a solution of 2+ F−enabled the detection of CO2(∼100 ppb; 2.29 μM) through enhanced emission. The mode of interaction has been confirmed by 1H NMR titration studies which suggested the deprotonation of the –NH fragment of an imidazolyl unit in the presence of F−. [ABSTRACT FROM AUTHOR]

The table of contents for the November 14, 2015 issue of "Dalton Transactions An International Journal of Inorganic Chemistry" is presented.

One-pot synthesis of POM-salt ([Himi]4[SiMo12O40] (1)) was achieved by mixing silicomolybdic acid and imidazole in acidic conditions and characterized by FTIR, TGA, SEM, EDX, ICP-OES and XPS. The structure of 1 was confirmed by single crystal X-ray analysis. The matching of the simulated PXRD pattern with the experimental pattern indicates the phase purity of 1. Interestingly, 1 showed highly selective and sensitive colorimetric detection of hydrated zinc chloride (ZnCl2·2H2O). The addition of ZnCl2·2H2O into 1 in the DMSO–H2O mixture shows the formation of blue colour. Furthermore, metal ions including other anionic zinc salts did not produce any colour change. The limit of detection was calculated to be 0.15 μM. Similarly, solid mixing of ZnCl2·2H2O with 1 can also produce a visible blue colour change. On the other hand, anhydrous ZnCl2 did not form any color change under the same conditions. The mechanistic studies indicate that the reduction of Mo6+ to Mo5+ might be responsible for the selective colour change. The reversible colour change between colorless and blue colour upon addition of EDTA into 1-ZnCl2·2H2O demonstrates the reusability of 1. Furthermore, microbial activity of 1 was investigated towards a series of Gram-positive and Gram-negative bacterial and fungal strains. Effective bactericidal activity of 1 was analyzed against Staphylococcus aureus. [ABSTRACT FROM AUTHOR]

An original approach to achieve the C(sp2)–H azolation of cyclic aldonitrones mediated by Selectfluor® has first been employed. By exploiting a metal-free, visible-light-promoted cross-dehydrogenative C–N coupling reaction between model aldonitrones, 2H-imidazole 1-oxides, and NH-containing azoles, a series of novel azaheterocyclic derivatives have been obtained in yields up to 94%. The elaborated protocol has proved to be appropriate for gram-scale processes and displayed potential for utilization in the synthesis of novel structural analogues of lanabecestat. Besides, mechanistic studies have revealed that this coupling reaction is likely to proceed via a nitroxide-involving radical pathway, encompassing a chain of electron transfer events, such as hydrogen atom transfer (HAT) and single electron transfer (SET). [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) are receiving growing interest as highly tunable, multifunctional materials. Remarkably for liquids, they tend to display a high level of structural order. This structural order may even lead to the formation of mesophases such as liquid crystals (LCs). Imidazolium compounds are by far the most popular ILs, because they offer a widely versatile platform for property tuning. To investigate what is driving structural order in imidazolium-based ILs a series of asymmetrical 1-dodecyl-2-methyl-3-alkylimidazolium bromides, [C12C1Cnim][Br] with n = 0–12 have been synthesized, fully characterized and their structures and properties compared with the analogous 1-dodecyl-3-alkylimidazolium as well as the 1,2,3-triazolium bromides. The aim is to examine the influence of the replacement of the most acidic 2-H proton on the imidazolium head group by methylation on the properties and structure of ILs. For all compounds, except for compounds with butyl- and hexyl-chains as well as the protonated species, mesophase formation can be observed. Obviously, the simple presence of long alkyl chains such as dodecyl (a design concept frequently put forward in the literature) is not sufficient to support mesophase formation alone. Rather, for the formation of a liquid crystalline phase, a balance between attractive van der Waals forces, hydrogen bonds, and electrostatic interactions is required. Data from temperature-dependent small-angle X-ray scattering (SAXS) and polarizing optical microscopy (POM) suggest three different cation conformations for the studied [C12C1Cnim][Br]: cations with 0 ≤ n ≤ 4 exhibit a near-linear conformation; for 5 ≤ n ≤ 10 a V-shape is adopted, and for n = 11 or 12 a U-shape is found. We demonstrated that the structural possibility for an interdigitation of the long chains is an influential factor for the formation of a mesophase. [ABSTRACT FROM AUTHOR]

Alcoholysis is a potential method for the degradation of polyesters to their precursor building blocks, which can then be polymerized again to form new qualified polyester materials. This method therefore makes recycling possible in a permanent polymer–monomer–polymer loop. In this study, a series of metal-free tetrabutylphosphonium-based ionic liquids (ILs) were prepared as catalysts for the methanolysis of poly(ethylene 2,5-furandicarboxylate) (PEF), which is well known as an ideal alternative to the petroleum-based plastic poly(ethylene terephthalate) (PET). It was found that anions with stronger electronegativity were more efficient for the methanolysis of PEF. By adjusting the structures of the anions and cations of ILs, 1-butyl-3-methylimidazole acetate ([BMIm][OAc]) exhibited excellent catalytic activity in the methanolysis of PEF. The optimization of reaction parameters enabled the [BMIm][OAc]-catalyzed methanolysis of PEF with nearly 100% PEF degradation and a 77.6% dimethyl furan-2,5-dicarboxylate (DMFD) yield at 130 °C for 30 min. Furthermore, [BMIm][OAc] could keep high-activity after using for six times under the optimum conditions. Assisting with 1H NMR, FT-IR and density functional theory (DFT) calculations, an in-depth study was performed on the feasible synergetic catalytic mechanism of [BMIm][OAc] for the methanolysis of PEF, induced by hydrogen bonds formed between reactants and [BMIm][OAc]. Finally, on the basis of experimental results and scanning electron microscopy (SEM), it was confirmed that PEF with the spiral motif could be degraded under milder conditions than PET. Therefore, this strategy of using adjustable cation and anion structures in ILs provides an opportunity to develop other more efficient ILs for the alcoholysis of furan-based polymers via a green and mild pathway. [ABSTRACT FROM AUTHOR]

Six new Co(II)/Ni(II) coordination polymers, [Ni3(opda)3(mbib)4(H2O)4]·2H2O (1), [Ni(mpda)(mbib)]·H2O (2), [Ni(ppda)(mbib)]·H2O (3), [Co(opda)(pbib)(H2O)] (4), [Co(mpda)(pbib)1.5] (5), and [Co(ppda)(pbib)(H2O)2]·2H2O (6) (H2opda = 1,2-phenylenediacetic acid, H2mpda = 1,3-phenylenediacetic acid, H2ppda = 1,4-phenylenediacetic acid, mbib = 1,3-bis(1-imidazoly)benzene, and pbib = 1,4-bis(1-imidazoly)benzene), were synthesized using Co(II)/Ni(II) salts and the bis(imidazole) ligand in the presence of three different flexible phenylenediacetate isomers under hydrothermal conditions. In 1, the opda2− ligand exhibits a trans-conformation and acts as a bridging building block extending a 1D loop-containing (Ni–mbib) polymer chain into a 2D network. In 2 and 3, mpda2− and ppda2− ligands possess a cis-conformation and can be seen as a "V"-type building block, linking Ni(II) atoms to form a 1D loop-containing chain together with the mbib ligand. Utilizing the isomer bridging ligand pbib and a different metal ion, Co(II), instead of the mbib ligand and Ni(II) ion, 2D (4), 1D (5), and 2D (6) coordination polymers were obtained. The structural diversity of these complexes is mainly attributed to the different coordination modes and isomer conformations of flexible phenylenediacetic acids and the bis(imidazole) ligand. Furthermore, six Co(II)/Ni(II) coordination polymers could accelerate the degradation rate of methylene blue (MB) under visible light irradiation, especially complex 4. Complex 2 exhibited a high performance in the oxygen evolution reaction (OER). Results will provide an effective way to develop coordination polymers towards electrochemical applications. [ABSTRACT FROM AUTHOR]

Based on a novel pyridinephenyl bifunctional ligand of 5-(6-carboxypyridin-2-yl)benzene-1,3-dicarboxylic acid (H3L), four Zn(II)/Co(II) coordination polymers (CPs), {[Zn(BIMB)(HL)]·H2O}n (1), [Co(BIMB)(HL)(H2O)]n (2), {[Zn2(BIBP)2(HL)2]·2H2O}n (3), and {[Co3(BIBP)3(L)2(H2O)2]·5H2O}n (4), have been constructed with the introduction of two length-suitable bis(imidazole) linkers (BIMB = 4,4-bis(imidazol-1-ylmethyl)biphenyl; BIBP = 4,4-bis(imidazol-1-yl)diphenyl). Structural analysis shows that CP 1 exhibits a 2D wave 4-c {44·62} sql sheet, and CP 2 shows an interesting 2D + 2D → 2D interpenetrating structure with ABAB sql packing. CP 3 displays an unprecedented 3D (4,4)-c {42·83·10}-tcj net. CP 4 presents a 2D (3,4,4)-c {62·7·82·10}{62·73·8}2{63}2 trilayer structure reported for the first time. Luminescence sensing exploration reflected two luminescent Zn(II) CPs possessing excellent performances in sensing Fe3+ cation, Cr2O72−/CrO42− anions, and NFT/NZF antibiotics in aqueous solution. Besides, the four obtained CPs also demonstrated outstanding potential as photocatalysts in the degradation of methylene blue (MB). [ABSTRACT FROM AUTHOR]

The [FeN6] chromophores found in [Fe(didentate)3]2+ complexes, where didentate is a non-symmetrical 2-(6-membered-heterocyclic ring)-benzimidazole ligand (Lk), exist as mixtures of two geometrical mer (C1-symmetry) and fac (C3-symmetry) isomers. Specific alkyl-substituted six-membered heterocyclic rings connected to the benzimidazole unit (pyridines in ligands L1–L3, pyrazines in L4–L5 and pyrimidines in L6–L7) control the ligand field strength and the electron delocalization so that [FeII(Lk)3]2+ display tunable thermally-induced spin transitions in solution. Thermodynamic, spectroscopic (UV-Vis, NMR) and magnetic studies in solution demonstrate that [Fe(L6)3]2+ (L6 = 1-methyl-2-(pyrimidin-2-yl)-1H-benzo[d]imidazole) exhibits a close to room temperature spin transition (T1/2 = 273(3) K) combined with a high stability formation constant (in acetonitrile), which makes this complex suitable for the potential modulation of lanthanide-based luminescence in polymetallic helicates. A novel method is proposed for assigning specific thermodynamic spin crossover parameters to fac-[Fe(L6)3]2+ and mer-[Fe(L6)3]2+ isomers in solution. The observed difference relies mainly on the entropic content ΔS merSCO − ΔS facSCO = 11(1) J mol−1 K−1, which favors the spin transition for the meridional isomer. Intermolecular interactions occurring in the crystalline state largely overcome minor thermodynamic trends operating in diluted solutions and a single configurational isomer is usually observed in the solid state. Among the thirteen solved crystal structures 1–13 containing the [M(Lk)3]2+ cations (M = Fe, Ni, Zn, Lk = L6–L7), pure meridional isomers are observed six times, pure facial isomers also six times and a mixture (44% mer and 56% fac) is detected only once. Solid-state magnetic data recorded for the FeII complexes show the operation of slightly cooperative spin transitions in 7 (fac-[Fe(L6)3]2+) and 12 (mer-[Fe(L7)3]2+). For the meridional isomer in 6, a two-step spin state transition curve, associated with two phase transitions, is detected. [ABSTRACT FROM AUTHOR]

In this study, a series of high-activity imidazole-based dicationic ionic liquids (DILs) were designed and prepared as efficient catalysts for balancing the reactivity between the endo-hydroxyl group (endo-OH) and the exo-hydroxyl group (exo-OH) of isosorbide (ISO) to synthesize high molecular weight poly(isosorbide carbonate) (PIC). Meanwhile, the thermal performance of PIC was precisely optimized by regulating the chain configuration. The results showed that when the trace amounts (4.5 × 10−5 based on the ISO molar amount) of bis-(3-methyl-1-imidazole)-ethylene dibromide ([C2(Min)2][Br]2) were used, the weight average molecular weight (Mw) of PIC reached 98 700 g mol−1. It could be concluded from the results of the experiment and the stimulation that the high catalytic activity of DILs was attributed to the strong electrostatic interaction between the cation and the substrate and the effective balance of the reactivity of the endo-OH and the exo-OH. Furthermore, we found that the reduction of hydroxyl groups in the terminal groups and the increase of endo–endo (a1) structure in the repeating unit improved the thermal properties of PIC. Finally, 1H NMR, Fourier infrared spectroscopy, and density functional theory (DFT) calculations were used to verify the reaction process through anion and cation multi-site synergistic effect and a possible electrophilic–nucleophilic reaction mechanism was successfully obtained. [ABSTRACT FROM AUTHOR]

Novel V-shaped fluorophores with an imidazole skeleton composed of arylethynyl moieties were developed. Their HOMO–LUMO energy gaps were well controlled by the introduction of electron-withdrawing or -donating groups in the aryl moiety. Compounds with different substituents at the 4- and 5-positions were selectively synthesized exploiting the difference in reactivity between the iodo and bromo groups. All compounds synthesized displayed fluorescence not only in solution but also in the solid state. The compound with a donor–acceptor structure displayed a fluorescence maximum with a wavelength over 500 nm and a large Stokes shift of about 150 nm, due to its intramolecular charge transfer character. In the solid state, the synthesized compounds have planar structures, indicating an expansion of π-conjugation. Upon exposure of the compounds in the solid state to acid vapor, the fluorescence of the compounds with acceptor groups was quenched, and that of the others shifted to longer wavelengths. [ABSTRACT FROM AUTHOR]

This paper reports for the first time in situ crystal growth of ZIF-8 on electrospun polyurethane (PU) nanofibers. In SEM images, continuous and compact ZIF-8 nanocrystals grow along electrospun PU nanofibers. The highest loading capacity of ZIF-8 on PU reaches 63%. By N2 adsorption-desorption, ZIF-8-PU shows a high surface area of 566 cm(2) g(-1). Combining the good flexibility of PU with the high adsorption properties of ZIF-8, ZIF-8-PU can be easily tailored into clothes or other forms as adsorption material. Furthermore, the gas adsorption ability of ZIF-8-PU was measured for H2, N2, O2 and CO2 at room temperature (20 °C) under different pressure gradients. The results show that the adsorption capacity of ZIF-8-PU for CO2 is nearly 11 times that for H2, 50 times that for O2 and 75 times that for N2 at 800 mmHg.

Novel antimony(III) imidazole selone complexes in a super crowded environment are reported for the first time. The super bulky selone antimony complexes, [{IPr*Se}(SbCl3)2] (1) and [{IPr*Se}(SbBr3)2] (2), were isolated from the reactions between IPr*Se (IPr*Se = [1,3-bis(2,6-diphenylmethylphenyl)imidazole selone]) and suitable antimony(III) halides. 1 and 2 are dinuclear complexes with a Sb : Se ratio of 1 : 0.5 with an unusual coordination mode of selone. The molecules 1 and 2 consist of both Menshutkin-type Sb⋯πaryl interactions and a Sb–Se coordination bond. However, the reaction between antimony(III) halides and [(IPaul)Se] ([(IPaul)Se] = [1,3-bis(2,4-methyl-6-diphenyl phenyl)imidazole selone]) with a spatially defined steric impact gave the dinuclear complex [{(IPaul)Se}(SbCl3)]2 (3) and the mononuclear complex [{(IPaul)Se}(SbBr3)] (4) without Menshutkin-type interactions. The Sb : Se ratio in 3 and 4 is 1 : 1. Interestingly, the Menshutkin-type interaction was absent in 3 and 4 due to the efficient coordinating ability of the ligand [(IPaul)Se] with the Sb(III) center compared to that of the super bulky ligand IPr*Se. The thermal property of these antimony selone complexes was also investigated. Density functional theory (DFT) calculations were carried out on the model systems [L(SbCl3)2] (1A), [L(SbCl3)] (1B), [L′(SbCl3)2] (1C), and [L′(SbCl3)] (1D), where L = [1,3-bis(2,6-diisopropyl-4-methyl phenyl)imidazole selone] and L′ = [1,3-bis(phenyl)imidazole selone], to understand the nature of orbitals and bonding situations. The computed metrical parameters of 1A are in good agreement with the experimental values. Natural population analysis of the model system reveals that the natural charge and total population of antimony(III) are comparable. The unequal interaction between selenium and antimony obtained using Wiberg bond indices (WBIs) is fully consistent with the findings of the single-crystal X-ray studies. [ABSTRACT FROM AUTHOR]

The synthesis of a novel poly(ionic liquid) adsorbent (PIL-APIBCl) through the modification of poly(styrene-co-maleic anhydride) (PSMA) composites with N-(3-aminopropyl)imidazole (API) and benzyl chloride (BCl) is presented. The structural analysis was carried out by nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscopy (FESEM) and Fourier transform infrared (FT-IR). Batch adsorption experiments revealed that the investigated adsorbent exhibited good selectivity and a high adsorption capacity of 236.68 mg g−1 towards tetrachloroaurate (Au(III)) ions at pH 1.0 over a wide temperature range. The adsorption isotherms and kinetics of Au(III) on the PIL-APIBCl were fitted well by the Langmuir isotherm model and pseudo-second-order model, respectively, indicating successful chemical adsorption of Au(III) ions on the adsorbent surfaces. According to FESEM, FT-IR, XPS and NMR analysis, the adsorption mechanisms of Au(III) on PIL-APIBCl could be ascribed to electrostatic and intermolecular interactions. Therefore, due to its good cyclability and low cost, PIL-APIBCl is a promising adsorbent for Au(III) recovery from wastewater on a large scale. [ABSTRACT FROM AUTHOR]

A series of phenanthroimidazole (PI) derivatives (M1–M3): 2-phenyl-1H-phenanthro [9,10-d]imidazole (M1), 2-anthryl-1H-phenanthro[9,10-d]imidazole (M2), and 2-pyrenyl-1H-phenanthro[9,10-d]imidazole (M3) were synthesized and characterized using various spectroscopic techniques. The fluorescence quenching studies or sensing properties of the molecules M1–M3 with picric acid (PA) were studied. The molecules (M1–M3) exhibit strong fluorescence with a peak emission wavelength at 386, 486 and 456 nm. This emission gets quenched with the addition of PA. The mechanism of fluorescence quenching involves proton transfer from PA to M in the ground state, followed by the formation of a complex between the cation (M+) and picrate anion (PA−). The proton transfer breaks the conjugation inside the imidazole ring which in turn leads to loss of fluorescence. The proof of proton transfer was evident from the single X-ray crystal structure of the co-crystals (M1+–PA− and M3+–PA−) and their Hirshfeld surface analysis. Time-resolved fluorescence measurements reveal that quenching is static. The complex formation constant (Ks) and life-time for all the molecules are measured. [ABSTRACT FROM AUTHOR]

The enantiomeric separation of seven imidazole antifungals was first systematically examined on a derivative polysaccharide chiral stationary phase (CSP), i.e. Chiralcel OD-RH in the reversed phase mode. The influence of the type and content of the organic modifier, the pH of buffer solution, type and concentration of buffer salt, and column temperature on enantiomeric separation were evaluated and optimized. The maximum resolution values for flutrimazole, econazole, miconazole, butoconazole, isoconazole, sulconazole, and climbazole were 2.36, 1.55, 0.89, 1.51, 0.96, 1.13, and 2.30. For a better understanding of the chiral recognition mechanism, detailed computational simulations of Chiralcel OD-RH interaction with seven pairs of enantiomers were carried out using the molecular docking software AutoDock. The various interactions affecting enantiomeric separation were confirmed in detail from the the molecular level. The modeling data were in agreement with the chromatographic results concerning enantioselectivity. It was found that the enantiomeric separation of imidazole analytes on Chiralcel OD-RH was the result of a mixture of hydrogen bonds, π–π, hydrophobic, dipole–dipole, and some special interactions. The docking results showed good agreement with our experimental results. [ABSTRACT FROM AUTHOR]

Imidazole (Im) and imidazolium (ImH+) cations play a vital role in the stability of biomolecules in an aqueous environment. The importance of water molecules in the interaction between ImH+ and aromatic amino acids (AAs) is unprecedented. Thus, we have used both quantum mechanical (QM) and molecular dynamics (MD) simulation approaches to understand the nature of interactions between AAs and ImH+ with water molecules. The microscopic studies of AA models and ImH+–water (ImH+Wn, where n = 0–4) clusters were calculated using the M05-2X/6-31+G** method. From DFT calculations, it is observed that the absence of water molecules in ImH+ favors the N–H⋯π interactions (i.e., T-shape) with AAs, whereas the microhydrated clusters of ImH+ prefer to stabilize the stacking conformation. The presence of water-mediated hydrogen bonding (H-bonding) interactions is highly favorable for the stacked confirmation of AAs–ImH+ complexes. This also directly influences the energetics of the cluster. The magnitude of the interaction strength between ImH+Wn and the selected AAs is in the order of Phe < Tyr ∼ Trp. The water-mediated H-bonding interactions act as the main driving force for the stability of π-stacking complexes. Both DFT and MD studies reveal that the ImH+ cation and water molecules play a vital role in the protein stability and also this can intuitively initiate the denaturation process. [ABSTRACT FROM AUTHOR]

Ionic liquids (ILs) as additives were used in the selective conversion of bio-based carbohydrates to 5-hydroxymethylfurfural (HMF) in this work. The effect of adding various imidazole-based ionic liquids with different anion structures on the production of HMF from fructose was firstly investigated in aqueous media. The presence of 15 wt% 1-butyl-3-methylimidazole chloride ([Bmim]Cl) ionic liquids in water with Fe2(SO4)3 as the homogeneous catalyst provided a more effective HMF synthesis compared to that without [Bmim]Cl addition. The enhanced HMF yield was mainly attributed to the fact that [Bmim]Cl might play a vital role in stabilizing the HMF molecule, which could thereby suppress side reactions involving HMF (e.g., its rehydration to levulinic acid or/and polymerization to humins). NMR and FTIR analyses suggested that such a stabilization effect stemmed from the interaction of [Bmim]Cl with the hydroxyl and aldehyde groups of HMF through hydrogen bonding. By performing the operation in a biphasic system (i.e., with the biomass-derived THF solvent as the organic phase and the addition of NaCl salt into water for improving HMF partition), the HMF yield over the Fe2(SO4)3 catalyst in the presence of the [Bmim]Cl additive could be further improved. The catalyst and ionic liquids were quite stable, and could be reused for more than five cycles with a consistent activity. A similar enhancement effect of [Bmim]Cl was also demonstrated in HMF synthesis with better yields from other biomass feedstocks or derivatives (including glucose, sucrose, cellobiose, inulin and starch) in aqueous media. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate framework-8 (ZIF-8) with different sizes and morphologies were successfully synthesized using a membrane dispersion reactor (MDR). The MDR synthesis applied in this paper was expected to be an efficient and economical way to synthesize ZIF materials. [ABSTRACT FROM AUTHOR]

Zeolitic imidazolate frameworks (ZIFs) have attracted considerable attention for many potential applications because they have a unique porous structure and excellent thermal and chemical stabilities. In recent years, significant efforts have been made to develop different methods for the controllable synthesis of ZIFs with desirable crystal structure and morphologies, and for decreasing the excessive amounts of organic ligands and solvents used in the synthesis process to reduce the costs and environmental impacts. This paper highlights the strategies recently reported, including the controllable synthesis of ZIFs with desirable morphologies and pore structure using a surfactant and a template in aqueous solution, the synthesis of ZIF particles and nanocrystals in base solution, and the dry gel and mechanochemical syntheses of ZIFs with minimal solvent usage. [ABSTRACT FROM AUTHOR]

The physical dissolution of carbohydrates (cellulose, chitin, and starch), i.e., without the formation of covalent bonds requires the solvent to possess certain physicochemical properties. Concentrating on cellulose, the solvent should act both as a Lewis acid and a Lewis base, and disrupt the present hydrophobic interactions, as the biopolymer exhibits amphiphilic characteristics. The quantification of the relative importance of these physicochemical properties helps in predicting the solvent structures, which are expected to be efficient as cellulose solvents. Ionic liquids (ILs) are extensively used as carbohydrate solvents because they disrupt the intramolecular-, intermolecular-, and hydrophobic interactions within the biopolymer structure, leading to its dissolution. Solvatochromic substances (probes) are especially sensitive to one or more of the above-mentioned biopolymer–solvent interactions. Consequently, they are used to predict and rationalize the solvent efficiency. The solvent parameters (descriptors) most widely employed are empirical polarity, ET(probe), Lewis acidity (SA); Lewis basicity (SB), dipolarity (SD), and polarizability (SP); S refers to the solvent. We synthesized 18 ILs, including derivatives of imidazole, 1,8-diazabicyclo[5.4.0]undec-7-ene, and tetramethylguanidine; the corresponding anions are carboxylates, chloride and dimethylphosphate. We used solvatochromic probes to calculate the descriptors of IL–DMSO (at fixed DMSO mole fraction of 0.6; 40 °C), and correlated ET(probe) with the other descriptors. We also tested the correlations by using a molar volume of the IL (VM) instead of SD, and the Lorentz–Lorenz refractive index function f(n) of the IL–DMSO mixture instead of SP. The quality of the regression analysis increased noticeably when we limited the ILs correlated with those based on imidazole (13 ILs), and used (VM) and f(n). The regression coefficients showed that SA is the most important descriptor; the solvent empirical polarity is inversely dependent on VM. The value of f(n) shows the importance of hydrophobic interactions. By using different probes, we showed that the observed small contribution of SB reflects the steric crowding around the positive nitrogen atoms in some probes. The results obtained help in selecting ILs as solvents for cellulose and other carbohydrates, based on the expected strength of their interactions with the biopolymers. Therefore, using solvatochromism for solvent efficiency screening saves labor and cost. [ABSTRACT FROM AUTHOR]

By introducing a series of pyridine derivatives as organic moieties, four Keggin-based compounds were synthesized, namely [Ag(Py2Piz)2(H2PW12O40)]·2H2O (1), [Ag4(AcyPh)4(H2SiMo12O40)2]·2H2O (2), [Ag2(Py3Piz)2(H2O)2(H3SiMo12O40)2]·8H2O (3) and {Ag4(Py2TTz)4[Ag(PMo12O40)2]}·Ag(Py2TTz)·2(Py2TTz)·6H2O (4) (Py2Piz = 4,5-bis(2-pyridinyl)imidazole, Py3Piz = 2-(4-pyridyl)4,5-di(2-pyridinyl)imidazole and Py2TTz = 2,5-bis(4-pyridyl)thiazolo[5,4-d]thiazole). In compound 1 the [Ag(Py2Piz)2]+ subunits link Keggin anions through weak Ag-O interactions to form a 1D chain. In compound 2 two mono-supporting Keggin anions are fused by two [Ag(AcyPh)]+ subunits to construct a dimer. In compound 3 there is a mono-capped Keggin anion with an [Ag(Py3Piz)(H2O)]+ subunit. Compound 4 contains a Keggin-dimer linked by an Ag ion. Each dimer is further connected by four sets of [Ag(Py2TTz)]+ lines to construct a 3D framework. All these compounds can be used as nitrite electrochemical sensors. All of them show good photocatalytic activity for MB. In addition, compound 4 shows a selective response to Hg2+ ions. [ABSTRACT FROM AUTHOR]

A synthetic pathway for the directed preparation of three novel polyoxovanadate-based copper frameworks (POVCFs), i.e., [Cu0.5(1-ipIM)2]2[V4O11] (POVCF 1), [Cu(1-ipIM)2](VO3)2 (POVCF 2) and [Cu(1-pIM)4](HpIM)4[V10O28] (POVCF 3) (1-ipIM = 1-isopropylimidazole; 1-pIM = 1-propylimidazole) using bifunctional imidazole molecules as organic ligands and base has been developed. Systematic studies revealed that the variable base enviroment in the reaction is the key step in the preparation of 1D to 3D supermolecular networks of POVCFs 1–3. Single crystal X-ray diffraction analyses demonstrated that the Cu2+ atoms of POVCFs 1–2 were coordinated with four imidazole derivative molecules and two different polyoxovanadate {[V4O11]2− and [V10O28]6−} clusters, respectively, exhibiting a [CuN4O2] binding set and a distorted octahedral geometry. Specifically, POVCF 1 exhibited adjacent [V4O11]2− that dangle up and down arranged in a parallel 2D network and further coordinated with [Cu(1-ipIM)4]2+ to form a 3D supramolecular structure. However, POVCF 3 presented one tetrahedral coordinated vanadium atom and one four-coordinated copper atom and they further gave rise to a 1D network by the Cu–O and V–O bonds. More importantly, these POVCFs were further studied in the construction of C–N bond reactions of primary amines under mild conditions, and it was found that POVCF 1 displayed efficient heterogeneous catalytic activities in the Chan–Lam reaction (yields up to 89%). [ABSTRACT FROM AUTHOR]

Here, we have demonstrated the visible LED light-promoted synthesis of poly functionalized imidazole derivatives by a four component condensation of 1,2-diphenyl 1,2-diketone aromatic aldehydes and ammonium acetate and/or amines in excellent yields. The solvent- and catalyst-free reaction conditions, excellent isolated yields of the products, shorter reaction times, and simple isolation and purification of the products make the present protocol efficient and a green alternative to existing protocols. [ABSTRACT FROM AUTHOR]

Stimuli-responsive supramolecular gels and metallogels have been widely explored in the past decade, but the fabrication of metallogels with reversible photoresponsive properties remains largely unexplored. In this study, we report the construction of photoresponsive hybrid zinc-based metallohydrogel systems coassembled from an imidazole functionalized phenylalanine derivative gelator (ImF) and carboxylic acid functionalized arylazopyrazole (AzoPz) molecular photoswitches in the presence of Zn2+ ions. Unlike traditional covalent conjugation, noncovalent introduction of small molecular switches into the gel matrix provides a convenient route to generate photoresponsive functional materials with tunable properties and expands the scope of optically controlled molecular self-assemblies. It has been found that the carboxylic acid functionalized AzoPz derivatives alone or mixed with the ImF moiety could not self-assemble to form any gels. However, in the presence of Zn2+ ions they readily formed the coassembled hybrid metallogels in an alkaline aqueous solution with various morphologies. These results suggest that the gelation process was triggered by the Zn2+ ions. In addition, the ImF gelator shows specific response to Zn2+ ions only. The presence of the AzoPz moiety in the gel matrix makes the metallogel coassemblies photoresponsive and the reversible gel-to-sol phase transition was studied by UV-vis spectroscopy. The gels showed a slow reversible light-induced gel-to-sol phase transition under UV (λ = 365 nm) and then sol-to-gel transition by green light (λ = 530) irradiation resulting in the reformation of the original gel state. The morphology and viscoelastic properties of the fibrillar opaque metallogels have been characterized by transmission electron microscopy (TEM) and rheological measurement, respectively. [ABSTRACT FROM AUTHOR]

A series of systematically tailored aryl acyclic (biphenyl, dye 1 and 2), cyclic (phenanthrene, dye 3 and 4) and methyl-substituted (dye 5) imidazole derivatives were synthesized and characterized for application in dye-sensitized solar cells (DSSCs). The anisole ancillary donor was attached to the –NH position in the imidazole center to obtain dyes 2 and 4. Cyclic voltammetry and UV-visible studies of all the dyes indicate their suitability for DSSC applications. Among the as-synthesized dyes, dye 4 with a phenanthrene donor and anisole ancillary donor showed the highest power conversion efficiency (PCE) of 7.16% (JSC = 13.07 mA cm−2, VOC = 0.831 V, FF = 0.659). Dye 2 displayed the highest electron lifetime in the conduction band of the photoanode; hence, the open circuit voltage of the DSSC based on dye 2 was the highest among the studied dyes (0.865 V). By using a novel potential-assisted dye staining process, the dye loading on the photoanode was enhanced by 18% in 1 h, which in turn enhanced the PCE to 8.10%. [ABSTRACT FROM AUTHOR]

Polyoxometalate (POM) cluster organic frameworks (POMCOFs) are an emerging class of catalytic materials, providing an opportunity to develop fascinating catalysts with well-defined, tunable, active sites for a range of chemical transformations. Although remarkable progress on numerous POMCOF materials has been reported, the synthesis of polyoxovanadate (POV) cluster organic frameworks (POVCOFs) has seldom been reported. Thus, the exploration of novel POVCOFs still attracts considerable research interest. Additionally, Knoevenagel condensation as a versatile tool for the construction of C＝C bonds still continues to be a challenge at room-temperature and under solvent-free conditions. Herein, three POV-based clusters, [Ni(1-bIm)4]2(V4O12)·H2O (1), [Ni(1-eIm)(H2O)4]2(V10O28)(1-eImH)2·2H2O (2) and [Ni(H2O)5]2(V10O28)(1-pImH)2·4H2O (3) (1-bIm = 1-butylimidazole; 1-eIm = 1-ethylimidazole and 1-pIm = 1-propylimidazole), have been made. 1 was controllably achieved by an imidazole-induced self-assembly strategy and exhibited a 2D POVCOF in which circular [V4O12]4− clusters are bridged by four six-coordinated Ni(II) atoms (NiN4O2 model). 2 and 3 are obtained at lower pH values. Notably, among the three POV-based clusters, POVCOF 1 displays highly efficient heterogeneous solvent-free catalytic activity (yields of up to 99%) and excellent recyclability in Knoevenagel condensation at room temperature. [ABSTRACT FROM AUTHOR]

Three new 3D lanthanide-based metal–organic frameworks (MOFs), [Ln2(ImBDC)3(2H2O)]n (where Ln = Tb3+ (1)/Sm3+ (2)/Eu3+ (3), ImBDC = 2-(imidazol-1-yl)terephthalic acid), have been synthesized solvothermally and characterized with single-crystal X-ray diffraction and other physicochemical methods. MOFs1–3 are isostructural and feature a 3D framework structure with 1D channels of dimension 3.91 × 5.27 Å2 decorated with basic imidazole groups. Owing to imidazole functionalized pores, MOF1 exhibits selective adsorption properties for CO2 with a high interaction energy (Qst) of 37.1 kJ mol−1. The activated samples of the MOFs act as efficient heterogeneous catalysts for the cycloaddition reaction of CO2 to epoxides to generate value-added cyclic carbonates. Interestingly, due to the narrow pore channels of the MOFs, preferential conversion of smaller size epoxides over the larger epoxides is observed. Furthermore, the MOF catalyst could be recycled and reused for up to five cycles without significant reduction in the catalytic activity. Thus the present study demonstrates size-selective catalytic activity for the conversion of smaller epoxides to cyclic carbonates under mild reaction conditions. [ABSTRACT FROM AUTHOR]

Narrow band red emitting phosphors play a vital role in high performance smart white LEDs. In this context, a series of new Eu(III) complexes have been synthesized with neutral ligands (C1-functionalised phenanthro-imidazole-based ancillary ligands substituted with phenyl moieties (m-CF3, p-CF3, p-CH3 and 1-naphthyl and 2-naphthyl group)) and dibenzoylmethane (DBM) as an anionic ligand. All the newly synthesized Eu-complexes showed extremely narrow band red emission due to the electric dipole transition (5D0–7F2, both in solid and thin film) with high quantum efficiency. A combined experimental and theoretical study indicates that the energy transfer from the ligand to the metal ion is complete. A temperature dependent photoluminescence (PL) study in solution reveals that the red emission is retained (only the ED (5D0–7F2) intensity decreases with increasing temperature). Red LEDs and hybrid white LEDs were fabricated by using a near UV LED chip with europium complexes and a near UV/blue LED conjugated with a yellow organic dye and europium complex mixture, respectively. Hybrid white LEDs (Eu(DBM)3Phen-pCN-pCF3 + yellow organic dye) showed superior CRI (84%) and CIE (x = 0.36, y = 0.39) values (near UV based) and CRI (82%) and CIE (x = 0.34, y = 0.36) values (blue LED based). In addition, the studied Eu-complexes herein showed excellent reversible on–off–on luminescence behavior with exposure to acid–base vapours. Detailed spectroscopic investigation reveals that the protonation of the Eu-complexes (ligands) plays a key role in the on–off–on luminescence. [ABSTRACT FROM AUTHOR]

We prepared five diarylethenes containing 2-aryl-imidazole as the ethene bridge (L1–L5), and introduced response sites in imidazole rather than in the traditional appended aryl units to regulate their photochromism and thermal stability under acid stimulus. The results show that we can change the thermal stability from P- to T-type, and prevent their photoactivity by acidification, and it is clarified that the stronger the acid or the more acid added, the faster the decay rate of the diarylethene photostability. Furthermore, the prohibited photoactivity could be restored by neutralization with an equimolar amount of base. [ABSTRACT FROM AUTHOR]

Liquid-phase hydroxylation of benzene to phenol using Schiff base complexes anchored on a mesoporous organosilica support was investigated in various solvents when molecular oxygen was utilized as a green oxidant. The mesoporous organosilica support was prepared through the condensation of tetraethyl orthosilicate (TEOS) and (3-aminopropyl)triethoxysilane (APTES) in different ratios, and then Schiff base complexes were anchored on it. Various aromatic heterocycles such as imidazole, 1-methyl imidazole, pyridine, and some pyridine derivatives were used as a proximal axial ligand, and their role in the reactivity of the catalyst was investigated experimentally and theoretically. Impressive promotion of the reactivity of the catalyst was the result of this coordination. Although all the synthesized catalysts showed catalytic reactivity, the vanadyl complex showed higher activity. The results show that SiO2-Pro-Sal-VO was extremely stable concerning leaching of the vanadyl group and rendered excellent recyclability in the hydroxylation of benzene to phenol with a yield of 11.3% and selectivity of >95%. The activity of the other catalysts was as follows: SiO2-Pro-Sal-Co > SiO2-Pro-Sal-Cu > SiO2-Pro-Sal-Fe > SiO2-Pro-Sal-Zn > SiO2-Pro-Sal-Mn. [ABSTRACT FROM AUTHOR]

Design and development of drugs in multi-drug resistant (MDR) infections have been of growing interest. We report the syntheses, and antibacterial and antifungal activities of imidazole-based 1,4-naphthoquinones (I-1 to I-4; 1-alkyl-2-methyl-1H-naphtho[2,3-d]imidazole-4,9-dione (alkyl = methyl to butyl)) and their precursors (B-3; N-(3-chloro-1,-dioxo-1,4-dihydronaphthalen-2-yl)acetamide) and A-1 to A-4; N-(3-(alkylamino)-1,4-dioxo-1,4-dihydronaphthalen-2-yl)acetamide (alkyl = methyl to butyl). Crystal structures of B-3, A-1 to A-3 and I-2 to I-4 were obtained through single crystal X-ray diffraction experiments. Electronic structure and charge distribution have further been characterized with the use of Density Functional Theory. Seven of these derivatives display a broad spectrum of antibacterial activity against few selected bacterial strains (Gram-positive and Gram-negative). As demonstrated MIC values with B-2 and B-3 against bacterial isolates were 8–64 μg ml−1 and those against pathogenic yeast, C. albicans, were observed in the range of 128–256 μg ml−1. MIC data of these derivatives suggest them to be promising against pathogens. [ABSTRACT FROM AUTHOR]

Chemotherapeutic metal-based compounds are effective anticancer agents; however, their cytotoxic profile and significant side effects limit their wide application. Natural products, especially flavonoids, are a prominent alternative source of anticancer agents that can be used as ligands for the generation of new bioactive complexes with metal ions of known biochemical and pharmacological activities. Herein, we present the synthesis and detailed structural and physicochemical characterizations of three novel complex assemblies of Ga(III) with the flavonoid chrysin and the ancillary aromatic chelators 1,10-phenanthroline, 2,2′-bipyridine and imidazole. The complexes constitute the only crystallographically characterized structures having a metal core from the boron group elements and a flavonoid as the ligand. The in vitro biological evaluation of the three complexes in a series of cancer cell lines of different origin established their cytotoxicity and ROS generating potential. In particular, the Ga(III)–chrysin–imidazole complex displayed the highest anticancer efficacy against all cancer cell lines with IC50 values in the low micromolar range (<1.18 μM), a result worth further investigation. [ABSTRACT FROM AUTHOR]