Synthesis of metal–organic materials is often dependent on the reaction conditions of suitable solvent/solvent mixture and temperature. A new finding based on a previously described protocol is ...reported: instead of obtaining metal–organic polyhedra (MOP), a metal–organic framework (MOF) with a 2D layered structure is obtained, following the same reported protocol. The 2D Cu(II)–5‐prop‐2‐ynoxyisophthlate MOF, crystallized in a kagomé‐type structure, is synthesized using different solvent systems at room temperature, as well as under solvothermal (nonhydrothermal) conditions. Under harsh reaction conditions, alkyne functional groups maintain their integrity and the copper does not catalyze the oxidative coupling of the terminal alkyne groups. X‐ray diffraction analyses confirm the structure and phase purity of the product. Based on the present results and the previous work reported by Zhao et al., it seems that two products, namely 0D MOP and 2D MOF, are equally possible when using the same reactants under same reaction conditions. However, the materials obtained in all the trials are MOF instead of MOP. From the structure point of view, there is a difference in connectivity of the initial building units that determines whether the product is MOP or MOF.
Reaction conditions like the temperature and solvent system are very critical for solid‐state materials involving metal–organic self‐assembly. Instead of metal–organic polyhedra, a 2D Cu(II)–5‐prop‐2‐ynoxyisophthalate metal–organic framework is reported, based on a previously described protocol. Different solvent systems under room temperature and solvothermal synthesis are employed, and all end up with a metal–organic framework crystallized with a kagomé‐type structure.
An efficient metal‐free cascade reaction between 1‐dibromovinyl‐2‐nitro‐substituted arenes and secondary amines results in the formation of polycyclic pseudoindoxyls in a single step. The reaction ...mechanism leading to these fused ring systems was investigated, and is believed to involve the initial formation of nitroarylated ynamines/ynamides. These intermediates cycloisomerize towards N‐alkenyl‐tethered 2‐aminoisatogens via a carbene intermediate as demonstrated by QTAIM (quantum theory of atoms in molecules) and ELF (electron localization function) analysis. A subsequent intramolecular dipolar cycloaddition afforded the title compounds.
Three in one: A metal‐free cascade reaction between ortho‐nitroaryl dibromoalkenes and secondary amines generates spiropseudoindoxyls. These reactions proceed via an ortho‐nitroaryl ynamine or ynamide, which is generated in situ and cycloisomerizes to afford three new rings in one step.
Pyrrolidinium Ionic Liquid Crystals Goossens, Karel; Lava, Kathleen; Nockemann, Peter ...
Chemistry : a European journal,
01/2009, Letnik:
15, Številka:
3
Journal Article
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N‐Alkyl‐N‐methylpyrrolidinium cations have been used for the design of ionic liquid crystals, including a new type of uranium‐containing metallomesogen. Pyrrolidinium salts with bromide, ...bis(trifluoromethylsulfonyl)imide, tetrafluoroborate, hexafluorophosphate, thiocyanate, tetrakis(2‐ thenoyltrifluoroacetonato)europate(III) and tetrabromouranyl counteranions were prepared. For the bromide salts and tetrabromouranyl compounds, the chain length of the alkyl group CnH2n+1 was varied from eight to twenty carbon atoms (n=8, 10–20). The compounds show rich mesomorphic behaviour: highly ordered smectic phases (the crystal smectic E phase and the uncommon crystal smectic T phase), smectic A phases, and hexagonal columnar phases were observed, depending on chain length and anion. This work gives better insight into the nature and formation of the crystal smectic T phase, and the molecular requirements for the appearance of this highly ordered phase. This uncommon tetragonal mesophase is thoroughly discussed on the basis of detailed powder X‐ray diffraction experiments and in relation to the existing literature. Structural models are proposed for self‐assembly of the molecules within the smectic layers. In addition, the photophysical properties of the compounds containing a metal complex anion were investigated. For the uranium‐containing mesogens, luminescence can be induced by dissolving them in an ionic liquid matrix. The europium‐containing compound shows intense red photoluminescence with high colour purity.
Het N‐alkyl‐N‐methylpyrrolidiniumkation werd gebruikt voor de bereiding van ionische vloeibare kristallen, waaronder een nieuw type uraniumhoudend metallomesogeen. Er werden pyrrolidiniumzouten met bromide‐, bis(trifluoromethylsulfonyl)imide‐, tetrafluoroboraat‐, hexafluorofosfaat‐, thiocyanaat‐, tetrakis(2‐thenoyl‐trifluoroacetonato)europaat(III)‐ en tetrabromouranyl‐anionen gesynthetiseerd. In het geval van de bromidezouten en de tetrabromouranylverbindingen werd de ketenlengte gevarieerd van acht tot twintig koolstofatomen (n=8, 10, 11, 12 ,13, 14, 15, 16, 17, 18, 19, 20). De verbindingen vertonen een rijk mesofasegedrag, van hooggeordende smectische fasen (de kristal‐smectische E fase en de zeldzame kristal‐smectische T fase) over smectische A fasen tot hexagonaal kolomvormige fasen, afhankelijk van de ketenlengte en het anion. Dit werk geeft een beter inzicht in de aard en vorming van de kristal‐smectische T fase, en de moleculaire vereisten voor het voorkomen van deze hooggeordende fase. Er wordt een nauwkeurige beschrijving gegeven van de mesofasestructuur, op basis van gedetailleerde poeder X‐stralendiffractie‐experimenten en door het verband te leggen met de bestaande literatuur omtrent deze ongewone tetragonale mesofase. Er worden structurele modellen voorgesteld die de zelforganisatie van de moleculen in de smectische lagen verduidelijken. Daarnaast werden de fotofysische eigenschappen van de verbindingen met een anionisch metaalfragment onderzocht. Voor de uraniumhoudende metallomesogenen werd aangetoond dat luminescentie geïnduceerd kan worden door deze op te lossen in een ionische vloeistof. De europiumhoudende verbinding vertoont een intense rode fotoluminescentie met een hoge kleurzuiverheid.
Rich smectic mesomorphism, including uncommon crystal smectic T phases, is exhibited by ionic liquid crystals based on N‐alkyl‐N‐methylpyrrolidinium cations and various counteranions, including a new type of uranium‐containing metallomesogens (e.g., see picture; C grey, Br green, N blue, O red, U yellow, H omitted). The U‐containing mesogens are photoluminescent when dissolved in an ionic liquid, and the EuIII‐based liquid crystal shows intense red photoluminescence with high colour purity.
A stereoselective synthetic method is reported for the molecular framework found in common daucane and isodaucane sesquiterpenoid natural products. The synthetic method constitutes a scalable, ...modular, and also asymmetric access to a complex natural product scaffold, wherein the substitution pattern and the stereochemistry can be adjusted simply by choosing different starting materials. The method allows the rapid introduction of diverse heterocyclic substructures such as (benzo)furans, (benzo)thiophenes, dithiins, thiazoles, and indoles, which actually also facilitate and direct the key intramolecular annulation step.
One, two, terpene: starting from diverse simple heterocyclic building blocks that are common drug fragments, a complex natural product carbon skeleton can be assembled in two robust synthetic operations, wherein the substitution pattern and the stereochemistry of the resulting fused polycycle can be adjusted simply by choosing different starting materials.
New metal‐containing ionic liquids Cu(CH3CN)nTf2N (n=2, 4; Tf2N=bis(trifluoromethylsulfonyl)‐ amide) have been synthesised and used as a non‐aqueous electrolyte for the electrodeposition of copper at ...current densities greater than 25 A dm−2. The tetrahedral copper(I)‐containing cation in Cu(CH3CN)4Tf2N is structurally analogous to quaternary ammonium and phosphonium ionic liquids and overcomes problems of metal solubility and mass transport. Two CH3CN ligands are removed at elevated temperatures to give Cu(CH3CN)2Tf2N, which can be used as a concentrated non‐aqueous electrolyte. The structural and electrochemical characterisation of these compounds is described herein.
Liquid metal salts: New metal‐containing ionic liquids Cu(CH3CN)nTf2N (n=2, 4; Tf2N=bis(trifluoromethylsulfonyl)amide; see figure) have been synthesised and used as a non‐aqueous electrolyte for the electrodeposition of copper to give current densities of greater than 25 A dm−2.
The anti‐atherogenic (anti‐inflammatory) properties of various aurate(I) salts, of the general formula NHC⋅HAuCl2 (NHC=N‐heterocyclic carbene) were investigated. The aurates were easily synthesized ...and obtained in analytically pure form. In addition, the biological activity of these compounds against atheromatosis via in vitro inhibition of platelet‐activating factor (PAF)‐induced platelet aggregation was probed. All complexes were found to possess anti‐aggregatory properties in vitro with IPr*⋅HAuCl2 (6) being the most potent inhibitor of PAF at micromolar concentration. Based on our findings, we conclude that these simply assembled aurates are a very promising class of PAF inhibitors and anti‐inflammatory drugs.
Good as gold: A series of N‐heterocyclic carbene (NHC)–aurates were synthesized and evaluated for their anti‐atherogenic properties toward platelet‐activating factor (PAF)‐induced aggregation of human platelet‐rich plasma (PRP). Both the gold and NHC moieties were shown to be crucial for good activity. All complexes were found to possess in vitro anti‐aggregatory properties.
Water splitting is the key step towards artificial photosystems for solar energy conversion and storage in the form of chemical bonding. The oxidation of water is the bottle‐neck of this process that ...hampers its practical utility; hence, efficient, robust, and easy to make catalytic systems based on cheap and earth‐abundant materials are of exceptional importance. Herein, an in situ generated cobalt catalyst, CoII(TCA)2(H2O)2 (TCA=1‐mesityl‐1,2,3‐1H‐triazole‐4‐carboxylate), that efficiently conducts photochemical water oxidation under near‐neutral conditions is presented. The catalyst showed high stability under photolytic conditions for more than 3 h of photoirradiation. During electrochemical water oxidation, the catalytic system assembled a catalyst film, which proved not to be cobalt oxide/hydroxide as normally expected, but instead, and for the first time, generated a molecular cobalt complex that incorporated the organic ligand bound to cobalt ions. The catalyst film exhibited a low overpotential for electrocatalytic water oxidation (360 mV) and high oxygen evolution peak current densities of 9 and 2.7 mA cm−2 on glassy carbon and indium‐doped tin oxide electrodes, respectively, at only 1.49 and 1.39 V (versus a normal hydrogen electrode), respectively, under neutral conditions. This finding, exemplified on the in situ generated cobalt complex, might be applicable to other molecular systems and suggests that the formation of a catalytic film in electrochemical water oxidation experiments is not always an indication of catalyst decomposition and the formation of nanoparticles.
Finding active catalytic species: An in situ generated cobalt catalyst efficiently conducts photo‐ and electrochemical water oxidation under near‐neutral conditions. This work sheds light upon the ability to directly assemble molecular metal–organic catalyst films on the surface of different conducting electrodes for the potential molecular engineering of cobalt‐based electrocatalytic films.
Mechanically responsive organic luminescent crystals are one of the promising choices of materials for flexible photonic devices. However, the change in phosphorescence emission as a function of the ...flexibility of a crystal has never been reported. Our current findings demonstrate two-dimensional (2D) and one-dimensional (1D) macroscopic elastic deformability, under mechanical stress, in elastically flexible single crystals of dibenzothiophene, and its brominated derivative, respectively. Unlike the presence of dual fluorescence (FL) and room temperature phosphorescence (RTP) in dibenzothiophene single crystals, the derivative was found to show only RTP. Interestingly, upon elastic deformation, single crystals of the dual emissive dibenzothiophene show a noticeable blue shift (∼20 nm) of RTP emission when compared to their pristine crystals (straight and naturally bent). However, their FL peaks remain nearly unchanged irrespective of the crystal deformation. A hierarchy of structure-elastic functionality to RTP modulation has been quantitatively mapped by rationalizing the role of chalcogen-involved weak interactions.
In response to macroscopic elastical bending, single crystals of dual emissive dibenzothiophene depict a significant blue shift (∼20 nm) of RTP emission when compared to their pristine crystals (straight and naturally bent).
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