Showing papers in "Australian Journal of Chemistry in 2014"
TL;DR: In this article, the authors introduce the methods available for predicting gas phase acidity and pKas in aqueous and non-aqueous solvents including high-level electronic structure methods, empirical linear free energy relationships (LFERs), implicit solvent methods, explicit solvent statistical free energy methods, and hybrid implicit-explicit approaches.
Abstract: Computational prediction of condensed phase acidity is a topic of much interest in the field today. We introduce the methods available for predicting gas phase acidity and pKas in aqueous and non-aqueous solvents including high-level electronic structure methods, empirical linear free energy relationships (LFERs), implicit solvent methods, explicit solvent statistical free energy methods, and hybrid implicit–explicit approaches. The focus of this paper is on implicit solvent methods, and we review recent developments including new electronic structure methods, cluster-continuum schemes for calculating ionic solvation free energies, as well as address issues relating to the choice of proton solvation freeenergytousewithimplicitsolvationmodels,andwhetherthermodynamiccyclesarenecessaryforthecomputationof pKas. A comparison of the scope and accuracy of implicit solvent methods with ab initio molecular dynamics free energy methods is also presented. The present status of the theory and future directions are outlined.
89 citations
TL;DR: In this article, an arsenic aptamer was used as a sensing probe and gold nanoparticles as a colorimetric indicator to detect trace arsenic(iii) (AsIII) in aqueous solution.
Abstract: In this study, trace arsenic(iii) (AsIII) in aqueous solution was detected by applying a classical aptamer-based gold nanoparticles colorimetric sensing strategy. An arsenic aptamer was used as a sensing probe and gold nanoparticles as a colorimetric indicator. In the absence of AsIII, the gold nanoparticles were stabilised by the arsenic aptamer and remained dispersed at high NaCl concentrations, displaying a red solution. Contrarily, in the presence of AsIII, the gold nanoparticles were prone to aggregation, owing to the formation of aptamer–AsIII complex between the arsenic aptamer and AsIII, and thus exhibited a blue solution. By monitoring the colour change, a simple and fast colorimetric assay for AsIII was established with a detection range of 1.26–200 ppb and a detection limit of 1.26 ppb. Because this colorimetric assay only involves common reagents and can be assessed visually, it holds great potential for arsenic(iii) monitoring in environment-related and other applications.
86 citations
TL;DR: In this paper, the authors summarize possible synthetic routes for the formation of these functional groups as well as highlight some of the most prominent applications of these exciting moieties in chemical biology and combinatorial chemistry.
Abstract: For more than 100 years, nitrogen-rich compounds such as azides, diazonium ions, and triazenes have proved to be extremely valuable. Because these functional groups can be easily introduced into various substrates, they are frequently used nowadays. More importantly, they can be converted into a great number of other functional groups. The scope of this article is thus to summarize possible synthetic routes for the formation of these functional groups as well as to highlight some of the most prominent applications of these exciting moieties in chemical biology and combinatorial chemistry. Many of the most famous name reactions such as the Staudinger reduction, Staudinger ligation, Sandmeyer reaction, Wallach reaction, Mitsunobu reaction, Huisgen reaction, Balz–Schiemann reaction, Meerwein arylation, Pschorr reaction or Gomberg–Bachmann reaction are covered.
66 citations
TL;DR: In this article, a point-charge self-consistent polarization model has been used to investigate the role of polarization in the CF3Cl:OH2 complex, and the polarised electron densities of the monomers component are shown to be a good representation of the electron density of complexes.
Abstract: A classical point-charge self-consistent polarization model has been used to investigate the role of polarization in the CF3Cl:OH2 complex. The polarised electron densities of the monomers component are shown to be a good representation of the electron densities of complexes, especially CF3Cl. The point-charge model overestimates the polarization of the water molecule, which is likely because exchange repulsion is unaccounted for in the classical model calculations.
63 citations
TL;DR: This review highlights pharmaceuticals currently used in Australia and New Zealand that have their origins in fungal metabolites, discussing the natural products chemistry and medicinal chemistry leading to their application as pharmaceuticals.
Abstract: Natural products, their derivatives or compounds based on natural product leads constitute ~50 % of clinically used pharmaceuticals. This review highlights pharmaceuticals currently used in Australia and New Zealand that have their origins in fungal metabolites, discussing the natural products chemistry and medicinal chemistry leading to their application as pharmaceuticals.
51 citations
TL;DR: A gold-catalyzed phenol synthesis was successfully used in the synthesis of dihydroisocoumarins for the first time as mentioned in this paper, and a large number of gold(i) complexes were prepared and tested; only complexes based on the biarylphosphine motif were successful.
Abstract: A gold-catalyzed phenol synthesis was successfully used in the synthesis of dihydroisocoumarins for the first time. A large number of gold(i) complexes were prepared and tested; only complexes based on the biarylphosphine motif were successful.
39 citations
TL;DR: This highlight describes enzyme immobilization on MOFs via covalent binding and its significance.
Abstract: Metal–organic frameworks (MOFs), possessing a well defined system of pores, demonstrate extensive potential serving as a platform in biological catalysis. Successful immobilization of enzymes in a MOF system retains the enzymatic activity, renders the active site more accessible to the substrate, and promises recyclability for reuse, and solvent adaptability in a broad range of working conditions. This highlight describes enzyme immobilization on MOFs via covalent binding and its significance.
36 citations
TL;DR: In this paper, a density functional theory study was carried out to examine the catalytic mechanism, activation mode, origin of stereoselectivity of a [5,5]-bicyclic guanidine-catalyzed Michael addition of dimethyl malonate to 2-cyclopenten-1-one.
Abstract: To illustrate the general principle of asymmetric organocatalysis of chiral bicyclic guanidine, a density functional theory study was carried out to examine the catalytic mechanism, activation mode, origin of stereoselectivity of a [5,5]-bicyclic guanidine-catalyzed Michael addition of dimethyl malonate to 2-cyclopenten-1-one. Two types of bifunctional activation modes were examined: Bronsted acid and Bronsted-Lewis acid. The calculated enantioselectivity (ee), based on eight C–C bond forming transition states and their pre-transition state complexes, is in excellent accord with experimental result. The ternary pre-transition state complexes are stable species, which strongly influence the stereoselectivity. Similar to enzyme catalysis, the bicyclic guanidinium catalyst plays an essential recognition role in assembling the substrates together via hydrogen bonds, multiple C–H···O interactions (as oxyanion hole), donor–acceptor, and electrostatic interactions.
35 citations
TL;DR: ZnO nanoparticles were prepared using the hydrothermal method, and then doped with Ag or Au NPs, yielding ZnO NPs 3, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 28, 29, 30, 31, 34, 34
Abstract: ZnO nanoparticles (NPs) were prepared using the hydrothermal method, and then doped with Ag or Au NPs, yielding ZnO NPs, ZnO–Ag NPs, and ZnO–Au NPs, which were characterized by transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The synthesized nanomaterials were analyzed for their antibacterial properties against bacterial strains (Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Salmonella typhi) by qualitative and quantitative assays. Minimal inhibitory concentration (MIC) results show that growth control is more effective for Gram-positive bacteria than for Gram-negative bacteria. Although ZnO NPs and Ag NPs are antibacterial agents, the lowest bacterial growth was observed for ZnO–Ag NPs, showing that the doped Ag NPs greatly facilitate the interaction between the microbial cells and the NP surface. Though the same antibacterial effect was expected for ZnO–Au NPs, the inhibition activity was very close to that of ZnO NPs. The order of bacterial cell growth inhibition was ZnO–Ag NPs >> ZnO–Au NPs ~ ZnO NPs >> ZnO powder. We also analyzed the morphology of bacterial cells treated with NPs by scanning electron microscopy.
35 citations
TL;DR: The history of pyrolysis equipment, methods, and reactions is narrated in the Introduction as mentioned in this paper, together with illustrations of apparatus and the solvent spray Flash Vapour Pyrolytic Potentials (SS-FVP).
Abstract: The history of pyrolysis equipment, methods, and reactions is narrated in the Introduction. Detailed descriptions of flash vacuum pyrolysis (FVP) (or thermolysis, FVT) apparatus for preparative and spectroscopic (UV, IR, electron spin resonance) purposes with product isolation at 77 K or in Ar matrices at ~10 K are presented. Very low pressure pyrolysis (VLPP), laser pyrolysis, and pulsed pyrolysis (jet flash pyrolysis) are also described together with illustrations of apparatus. The solvent spray flash vacuum pyrolysis (SS-FVP) of liquids or solutions of compounds of low volatility is described together with methods for the addition of solids to a pyrolysis tube, in particular details of pipto-pyrolysis (‘falling solid pyrolysis’). Methods used for catalytic vacuum gas–solid reactions (VGSR) are also summarised.
32 citations
TL;DR: Guanidinate ligands have proven their utility for CVD and ALD precursors for a broad range of metal centres as mentioned in this paper, and have been used to deposit metal oxides, metal nitrides and pure metal films by tuning process parameters.
Abstract: Volatile metal complexes are important for chemical vapour deposition (CVD) and atomic layer deposition (ALD) to deliver metal components to growing thin films. Compounds that are thermally stable enough to volatilize but that can also react with a specific substrate are uncommon and remain unknown for many metal centres. Guanidinate ligands, as discussed in this review, have proven their utility for CVD and ALD precursors for a broad range of metal centres. Guanidinate complexes have been used to deposit metal oxides, metal nitrides and pure metal films by tuning process parameters. Our review highlights use of guanidinate ligands for CVD and ALD of thin films over the past five years, design trends for precursors, promising precursor candidates and discusses the future outlook of these ligands.
TL;DR: In this article, a mini review describes the recent developments on the thermal and photocatalytic production of hydrogen peroxide and its use in hydrogen peroxy fuel cells, which can be operated with a one-compartment structure without a membrane.
Abstract: This mini review describes our recent developments on the thermal and photocatalytic production of hydrogen peroxide and its use in hydrogen peroxide fuel cells. Selective two-electron reduction of dioxygen to hydrogen peroxide by one-electron reductants has been made possible by using appropriate metal complexes with an acid. Protonation of the ligands of the complexes facilitates the reduction of O2. The photocatalytic two-electron reduction of dioxygen to hydrogen peroxide also occurs using organic photocatalysts and oxalic acid as an electron source in buffer solutions. The control of the water content and pH of a reaction solution is significant for improving the catalytic activity and durability. A hydrogen peroxide fuel cell can be operated with a one-compartment structure without a membrane, which is certainly more promising for the development of low-cost fuel cells as compared with two compartment hydrogen fuel cells that require membranes. Utilisation of iron complexes as cathode materials are reviewed.
TL;DR: The role of β-cyclodextrin on the binding of Coumarin 314 with calf thymus DNA was investigated in this paper, showing a hyperchromic shift of absorption and quenching of fluorescence due to binding with β-cycle.
Abstract: This paper discusses the binding of a laser dye, Coumarin 314 with β-cyclodextrin, studied mainly by UV-visible spectroscopy, 2D rotating-frame nuclear Overhauser effect spectroscopy (ROESY), steady-state spectroscopy and time-resolved fluorescence spectroscopy. The role of β-cyclodextrin on the binding of Coumarin 314 with calf thymus DNA was investigated. Coumarin 314 shows a hyperchromic shift of absorption and a quenching of fluorescence due to binding with β-cyclodextrin. The fluorescence quenching is non-linear and the reason for the non-linearity is discussed. The unusual fluorescence quenching on Coumarin 314–β-cyclodextrin binding is rationalised from the effect of acidity on absorption, fluorescence, and molecular modelling studies. Additional proof for the mode of binding is given by 2D ROESY. The capped and exposed portions of the Coumarin 314 molecule in the Coumarin 314–β-cyclodextrin complex when binding with calf thymus DNA were visualised based on spectral and molecular modelling studies.
TL;DR: In this article, 10 very different structural families of polyoxometalates have been found to exhibit slow magnetic relaxation due to single-molecule magnet (SMM) behaviour associated with the lanthanoid ions.
Abstract: Polyoxometalates are robust and versatile multidentate oxygen-donor ligands, eminently suitable for coordination to trivalent lanthanoid ions. To date, 10 very different structural families of such complexes have been found to exhibit slow magnetic relaxation due to single-molecule magnet (SMM) behaviour associated with the lanthanoid ions. These families encompass complexes with between one and four of the later lanthanoid ions: Tb, Dy, Ho, Er, and Yb. The lanthanoid coordination numbers vary between six and eleven and a range of coordination geometries are evident. The highest energy barrier to magnetisation reversal measured to date for a lanthanoid–polyoxometalate SMM is Ueff/kB = 73 K for the heterodinuclear Dy–Eu compound (Bu4N)8H4[DyEu(OH)2(γ-SiW10O36)2].
TL;DR: In this paper, a mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry.
Abstract: Continuous-flow microreactors offer major advantages for photochemical applications. This mini-review summarizes the technological development of microflow devices in the Applied and Green Photochemistry Group at James Cook University, and its associates, from fixed microchips for microscale synthesis to flexible multicapillary systems for parallel photochemistry. Whereas the enclosed microchip offered high space–time-yields, the open capillary-type reactor showed a greater potential for further modifications. Consequently, a 10-microcapillary reactor was constructed and used successfully for process optimization, reproducibility studies, scale-up, and library synthesis. To demonstrate the superiority of microflow photochemistry over conventional batch processes, the reactors were systematically evaluated using alcohol additions to furanones as model reactions. In all cases, the microreactor systems furnished faster conversions, improved product qualities, and higher yields. UVC-induced [2+2] cycloadditions of furanone with alkenes were exemplarily examined in a capillary reactor, thus proving the broad applicability of this reactor type.
TL;DR: The HERON reactions of N,N-dimethoxyacetamide (5) and alicyclic models 6 and 8 have been modelled computationally in this paper.
Abstract: Cyclic N,N-dialkoxyamides have been made, for the first time, by hypervalent iodine oxidation of β- and γ-hydroxyhydroxamic esters 17, 19, and 21. The fused γ-lactam products, N-butoxy- and N-benzyloxybenzisoxazolones (22a and 22b), are stable while alicyclic γ-lactam and δ-lactam products, 24 and 25, although observable by NMR spectroscopy and ESI-MS are unstable at room temperature, undergoing HERON reactions. The γ-lactam 24 undergoes exclusive ring opening to give a butyl ester-functionalised alkoxynitrene 28. The δ-lactam 25, instead, undergoes a HERON ring contraction to give butyrolactone (27). The structures of model γ- and δ-lactams 6, 7, and 8 have been determined at the B3LYP/6-31G(d) level of theory and the γ-lactams are much more twisted than the acyclic N,N-dimethoxyacetamide (5) resulting in a computed amidicity for 6 of only 25 % that of N,N-dimethylacetamide (3). The HERON reactions of N,N-dimethoxyacetamide (5) and alicyclic models 6 and 8 have been modelled computationally. The facile ring opening of 6 (EA = 113 kJ mol–1) and ring contraction of 8 (EA = 145 kJ mol–1) are predicted well, when compared with the HERON rearrangement of 5 (EA = 178 kJ mol–1).
TL;DR: In this article, the rheological properties of the solution of a hydrophobically associating acrylamide-based copolymer (HA-PAM) consisting of a modified monomer and a sodium 2-acrylamido-2-methylpropanesulfonic sulfonate were investigated.
Abstract: The rheological properties of electrolyte solution of a hydrophobically associating acrylamide-based copolymer (HA-PAM) containing hydrophobically modified monomer and sodium 2-acrylamido-2-methylpropanesulfonic sulfonate were investigated in this paper. The study mainly focussed on effects of electrolyte concentration, temperature, and shear rate on the solution rheological properties. HA-PAM exhibited much stronger salt tolerance and shearing resistance than the commonly used partially hydrolyzed polyacrylamide, and has great potential for application in tertiary oil recovery of oilfields with high salinity. The salt resistance mechanism of HA-PAM in solution was investigated by combining molecular simulation and experimental methods. The structure–performance relationship of the salt-resisting polymer may provide useful guidance for design and synthesis of novel water-soluble polymers with high salt resistance.
TL;DR: In this article, a model for the homogeneous Cr-PNP (PNP = diphosphinoamine) trimerization and tetramerization catalyst system has been studied theoretically, with the aim of identifying suitable density functional theory methods for treatment of this catalyst, and evaluating the likely oxidation and spin states of the active species.
Abstract: A model for the homogeneous Cr-PNP (PNP = diphosphinoamine) ethylene trimerisation and tetramerisation catalyst system has been studied theoretically, with the aim of identifying suitable density functional theory methods for treatment of this catalyst, and evaluating the likely oxidation and spin states of the active species. Benchmarking studies involving high-level treatment reveal the difficulty of accurately calculating the thermochemistry of this system, and suggest that local density functionals, such as M06L, probably provide the best option. Density functional theory modelling of catalyst activation and the first steps of oligomerisation up until 1-hexene formation appears to favour a CrI–CrIII mechanism, involving spin surface crossing from sextet to quartet states.
TL;DR: In this article, the synthesis and characterisation of a single source molecular precursor 1-(2-fluorolbenzoyl)-3-(3-ferrocenylphenyl)selenourea (M2F) was presented.
Abstract: This article presents the synthesis and characterisation (Fourier transform infrared spectroscopy, 1H NMR and 13C NMR spectroscopy, CHNS (carbon, hydrogen, nitrogen, sulfur) analysis, atomic absorption spectrometry, and single-crystal X-ray diffraction) of a single source molecular precursor 1-(2-fluorolbenzoyl)-3-(3-ferrocenylphenyl)selenourea (M2F). This precursor has been used for the fabrication of FeSe thin films by aerosol-assisted chemical vapour deposition (AACVD) in the presence of different concentrations of two different surfactants (triton and span) keeping all other conditions the same. Fabricated thin films have been characterised with powder X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. The interaction of the surfactants with the precursor (M2F) has been evaluated with cyclic voltammetry and UV–vis spectroscopy.
TL;DR: Guanidine compounds and their derivatives can be developed as catalysts, additives, or promoters in organic synthesis due to their unique chemical properties, which have attracted much attention in the chemistry and catalysis communities as discussed by the authors.
Abstract: Guanidine compounds and their derivatives can be developed as catalysts, additives, or promoters in organic synthesis due to their unique chemical properties, which have attracted much attention in the chemistry and catalysis communities. Particularly, the strong basicity and ease of structural modification allow them to offer wide applications in the field of CO2 capture and conversion. Guanidine compounds modified as ionic liquids or heterogeneous catalysts have also been developed for CO2 capture and conversion. In this context, the latest progress on CO2 capture using guanidine and their derivatives as absorbents with high capacity will be summarized. Furthermore, guanidine-catalyzed transformation of CO2 to a series of value-added chemicals with mechanistic consideration on a molecular level will be particularly elaborated in this article.
TL;DR: In this article, a novel recyclable and flexible membrane was prepared for the removal of oil spills and organic dye pollutants by functionalizing polyester textiles with reduced graphene oxide@ZnO nanocomposites using a layer-by-layer technique.
Abstract: A novel recyclable and flexible membrane was prepared for the removal of oil spills and organic dye pollutants, by functionalizing polyester textiles with reduced graphene oxide@ZnO nanocomposites using a layer-by-layer technique. The membrane showed efficient water/oil separation, and the amount of oil adsorbed by the membrane could be up to 23 times its own weight. The adsorption capacity was largely retained during many adsorption recycling cycles. The membrane also displayed highly efficient removal of a dye pollutant from water under simulated sunlight. The membrane maintained a near-original removal efficiency after five cycles of dye removal. This new type of membrane may find practical applications in the large-scale separation of organic pollutants from water, particularly in the field of oil spills clean-up and dye removal from industrial effluent.
TL;DR: Two spin crossover (SCO)-active 2D Hofmann-type framework materials, Fe(3-PAP)2Pd(CN)4] (A) and Fe(4-Pap)2PCN(CN), were prepared in this article.
Abstract: Two spin crossover (SCO)-active 2D Hofmann-type framework materials, [Fe(3-PAP)2Pd(CN)4] (A) and [Fe(4-PAP)2Pd(CN)4] (B) containing the photoactive azo-benzene-type ligands 3-phenylazo-pyridine (3-PAP) and 4-phenylazo-pyridine (4-PAP) were prepared. These materials form non-porous Hofmann-type structures whereby 2D [FeIIPd(CN)4] grids are separated by 3- or 4-PAP ligands. The iron(ii) sites of both materials (A and B) undergo abrupt and hysteretic spin transitions with characteristic transition temperatures T1/2↓,↑: 178, 190 K (ΔT: 12 K) and T1/2↓,↑: 233, 250 K (ΔT: 17 K), respectively. Photo-magnetic characterisations reveal light-induced excited spin state trapping (LIESST) activity in both A and B with characteristic T(LIESST) values of 45 and 40 K. Although both free ligands show trans- to-cis isomerisation in solution under UV-irradiation, as evidenced via absorption spectroscopy, such photo-activity was not observed in the ligands or complexes A and B in the solid state. Structural analysis of a further non-SCO active isomer to B, [Fe(4-PAP)2Pd(CN)4]·1/2(4-PAP) (B·(4-PAP)), which contains free ligand in the pore space is reported.
TL;DR: In this article, an azomethine 1,3-dipolar cycloaddition reaction with carbon fiber was used to graft complex molecules onto the fiber surface to enhance the interfacial interaction of the fibre to the matrix, the functionalised fibres possessed a pendant amine that is able to interact with epoxy resins.
Abstract: We demonstrate the utilisation of an azomethine 1,3-dipolar cycloaddition reaction with carbon fibre to graft complex molecules onto the fibre surface. In an effort to enhance the interfacial interaction of the fibre to the matrix, the functionalised fibres possessed a pendant amine that is able to interact with epoxy resins. Functionalisation was supported by X-ray photoelectron spectroscopy and the grafting process had no detrimental effects on tensile strength compared with the control (untreated) fibres. Also, microscopic roughness (as determined by atomic force microscopy) and fibre topography were unchanged after the described treatment process. This methodology complements existing methodology aimed at enhancing the surface of carbon fibres for advanced material applications while not compromising the desirable strength profile. Single-fibre fragmentation tests show a statistically significant decrease in fragment length compared with the control fibres in addition to transverse cracking within the curing resin, both of which indicate an enhanced interaction between fibre and resin.
TL;DR: In this paper, a series of new anthranilic diamide derivatives containing sulfide, N-cyanomethylsulfilimine, and N-cyclanomethemine groups were designed and synthesized by coupling the active substructures of anthraniles and sulfoxaflor and the structures of the synthesized compounds were confirmed by infrared spectroscopy, 1H and 13C NMR, and elemental analysis.
Abstract: Three series of new anthranilic diamide derivatives containing sulfide, N-cyanomethylsulfilimine, and N-cyanomethylsulfoximine groups were designed and synthesized by coupling the active substructures of anthranilic diamides and sulfoxaflor. The structures of the synthesized compounds were confirmed by infrared spectroscopy, 1H and 13C NMR, and elemental analysis. Several unique structural characteristics were revealed via the crystal structure analysis of compound N-(2-(2-methyl-2-(methylthio)propylcarbamoyl)-4-chloro-6-methylphenyl)-3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxamide 16e. Bioassay results indicated that most of the synthesized compounds showed superior insecticidal activities against Mythimna separata and Plutella xylostella when compared with the positive control cyantraniliprole. In particular, N-(2-(2-methyl-2-(N-cyanomethylsulfideimino)propylcarbamoyl)-4-chloro-6-methylphenyl)-3-bromo-1-(3-chloropyridin-2-yl)-1H-pyrazole-5-carboxamide 17e showed excellent insecticidal activity against Mythimna separata, with a mortality rate of 100 % at a concentration of 1 µg mL–1. These results indicated that sulfide, N-cyanomethylsulfilimine, and N-cyanomethylsulfoximine moieties, as important active substructures, could improve or maintain the activity of the anthranilic diamide and promote novel pesticide development.
TL;DR: In this article, a general reaction mechanism for the formation of carbodiimides, nitrile imines, and photochromism is put forward, which is also likely in the case of diphenylsydnone.
Abstract: The matrix photolyses of 3-phenyl-, 3-pyridyl, and 3,4-diphenylsydnones 16, 19, and 22 were investigated by matrixisolation infrared spectroscopy. The formation of the neutral, bicyclic lactone valence isomers postulated by Earl – the oxadiazabicyclo[2.1.0]pentanones exo-17 and exo-20 – was clearly observed in the first two cases and is also likely in the caseofexo-23(C¼OabsorptionsintheIRat1881,1886,and1874cm � 1 ,respectively).Theefficientphotodecomposition of sydnones to carbodiimides RN¼C¼NR 0 (18, 21, and 24) and CO2 was established in all three cases. The formation of benzonitrile 27 and azacycloheptatetraene 29 in the matrix photolysis of diphenylsydnone 22 is indicative of diphenylnitrile imine PhCNNPh 26 as an intermediate (2340cm � 1 ). Neither bicyclic lactones nor carbodiimides have been observed previously in sydnone photochemistry. A general reaction mechanism for the formation of carbodiimides, nitrile imines, and photochromism is put forward.
TL;DR: In this paper, a review of single (once only) and repeatable interfacial complexation by hydrogen bonding, the available hydrogen bonding pairs for complexation, the thermodynamics and kinetics of complexation and construction schemes is presented.
Abstract: Polymer complexes can form in the bulk and at interfaces. Polymer complex formation in the bulk has been studied for a long time. The recently developed layer-by-layer assembly technique well realizes polymer complexation at interfaces. The layer-by-layer assembly of polymers based on Coulomb forces or hydrogen bonding is a repeated complexation process conducted at a surface. This paper reviews both single (once only) and repeatable interfacial complexation by hydrogen bonding, the available hydrogen bonding pairs for complexation, the thermodynamics and kinetics of complexation, and construction schemes.
TL;DR: Following the publication in 2012 of the first compelling evidence of the synthesis of silicene, the silicon based counterpart of graphene, the last two years have seen a surge of articles on elemental, novel two-dimensional materials beyond graphene as mentioned in this paper.
Abstract: Following the publication in 2012 of the first compelling evidence of the synthesis of silicene, the silicon based counterpart of graphene, the last two years have seen a surge of articles on elemental, novel two-dimensional materials beyond graphene. Here, research in this burgeoning field is highlighted
TL;DR: In this paper, the nucleophilic fluorination of substituted benzenes using fluoride ions under mild reaction conditions has been one of the most important challenges for the synthesis of biologically active fluorinated aromatic compounds; however, only a few synthetically useful methods are known.
Abstract: The fluorination of substituted benzenes using fluoride ions under mild reaction conditions has been one of the most important challenges for the synthesis of biologically active fluorinated aromatic compounds; however, only a few synthetically useful methods are known. In this paper, it is reported that the nucleophilic fluorination of benzynes, generated from either 2-(trialkylsilyl)phenyl nonafluorobutanesulfonates or 2-(trialkylsilyl)phenols, meets this challenge. In particular, the fluorination starting from 2-(trialkylsilyl)phenols for fabricating aryl fluorides involves three sequential reactions in one-pot: the nonaflylation of phenols, benzyne generation, and nucleophilic fluorination of the benzynes. The regioselectivities of these reactions are controlled by the substituents at the C3-position of the benzynes.
TL;DR: The use of UAA probes in applications relying on FRET, PET, and environmental sensitivity are discussed and small probes that have thus far been used only in synthetic peptides are discussed, but which have unusual value and may be candidates for incorporation using UAA methods.
Abstract: Fluorescence methods allow one to monitor protein conformational changes, protein–protein associations, and proteolysis in real time, at the single molecule level and in living cells. The information gained in such experiments is a function of the spectroscopic techniques used and the strategic placement of fluorophore labels within the protein structure. There is often a trade-off between size and utility for fluorophores, whereby large size can be disruptive to the protein’s fold or function, but valuable characteristics, such as visible wavelength absorption and emission or brightness, require sizable chromophores. Three major types of fluorophore readouts are commonly used: (1) Forster resonance energy transfer (FRET); (2) photoinduced electron transfer (PET); and (3) environmental sensitivity. This review focuses on those probes small enough to be incorporated into proteins during ribosomal translation, which allows the probes to be placed on the interiors of proteins as they are folded during synthesis. The most broadly useful method for doing so is site-specific unnatural amino acid (UAA) mutagenesis. We discuss the use of UAA probes in applications relying on FRET, PET, and environmental sensitivity. We also briefly review other methods of protein labelling and compare their relative merits to UAA mutagenesis. Finally, we discuss small probes that have thus far been used only in synthetic peptides, but which have unusual value and may be candidates for incorporation using UAA methods.
TL;DR: Cell viability studies indicated the ‘safe’ concentration for these polymers is within a suitable window for the delivery of siRNA therapeutics, potentially improving the biodistribution of the stars in vivo.
Abstract: 16- and 32-arm star polymers were synthesised using poly(amido amine) (PAMAM) dendrimers as multifunctional initiators for the ring-opening polymerisation (ROP) of ϵ-Z-l-lysine N-carboxyanhydride (Lys NCA) via the core-first approach. The resulting star polymers were subsequently post-functionalised with poly(ethylene glycol) (PEG) via carbodiimide coupling, potentially improving the biodistribution of the stars in vivo. De-protection of the carboxybenzyl (Cbz)-protected star arms yielded water-soluble cationic poly(l-lysine) (PLL) star polymers with hydrodynamic radii ranging from 2.0 to 3.3 nm. Successful complexation of the PLL star polymers with double-stranded oligodeoxynucleotides (ODNs)—a mimic for small interfering RNA (siRNA)—was achieved at a nitrogen-to-phosphate (N/P) ratio of 5. Cell viability studies using HEK293T cells indicated the ‘safe’ concentration for these polymers is within a suitable window for the delivery of siRNA therapeutics.