Ethylene Molecules Research Articles

Infrared spectroscopy of carbocations upon electron ionization of ethylene in helium nanodroplets

The electron impact ionization of helium droplets doped with ethylene molecules and clusters yields diverse CXHY + cations embedded in the droplets. The ionization primarily produces C2H2 +, C2H3 +, C2H4 +, and CH2 +, whereas larger carbocations are produced upon the reactions of the primary ions with ethylene molecules. The vibrational excitation of the cations leads to the release of bare cations and cations with a few helium atoms attached. The laser excitation spectra of the embedded cations show well resolved vibrational bands with a few wavenumber widths-an order of magnitude less than those previously obtained in solid matrices or molecular beams by tagging techniques. Comparison with the previous studies of free and tagged CH2 +, CH3 +, C2H2 +, C2H3 +, and C2H4 + cations shows that the helium matrix typically introduces a shift in the vibrational frequencies of less than about 20cm-1, enabling direct comparisons with the results of quantum chemical calculations for structure determination. This work demonstrates a facile technique for the production and spectroscopic study of diverse carbocations, which act as important intermediates in gas and condensed phases.

Novel nickel(II) coordination polymer based on a semi-rigid tricarboxylate acid ligand: synthesis, structure, and fluorescence recognition of acetylacetone in aqueous media

Through a solvothermal reaction between the corresponding nickel(II) sulfate, π-electron rich tri-carboxylate ligand 4-(2′,3′-dicarboxylphenoxy) benzoic acid (H3L) and 1,2-bis (4-pyridyl) ethylene (bpe) molecule, a novel three-dimensional (3D) nickel-based coordination polymer (Ni-CP), namely [Ni3(L)2(bpe)3(H2O)4]·(H2O)6 (1) was successfully constructed. The structure was established by single-crystal X-ray diffraction, which reveals that 1 features a new 3,4,4-connected topology with the point symbol of (105·12) (4·102)2 (4·85)2. Subsequently, some studies on optical properties of compound 1 were carried out. Interestingly, the results suggest that compound 1 exhibits excellent applications as a fluorescent sensor for the recognition of Hacac via a fluorescence quenching approach. The detection limit can be as low as 10.19 µM. The possible mechanisms of the fluorescence turn-off effect were also discussed in detail. This work presents a case for monitoring Hacac concentrations in water samples.

Different behavior of two iso-structural zeolitic imidazolate frameworks in ethane-ethylene separation: Study of H2 -CO2 and CH4 -CO2 separation capacity.

The separation of ethane-ethylene mixtures was evaluated using two zeolitic imidazolate frameworks, which are only different from the assemble metal, as stationary phase from inverse gas chromatography data. The chromatographic profiles exhibited peaks adequately resolved. Separation is attributed to the pore sizes of the adsorbents that discern between ethane and ethylene molecule shapes and closed kinetic diameters. The adsorption heats were estimated for each probe molecule from the slopes of the straight lines at four temperatures. The evaluated materials are iso-structural compounds with the unique difference of assembling metal (cobalt and zinc). Cobalt material showed atypical adsorption of ethane over ethylene, which was observed taking into account the retarded elution of the paraffin. Therefore, the anomalous behavior could be ascribed to the presence of cobalt(II). Structural characterization of both materials was performed by X-ray powder diffraction, X-ray photoelectronic spectroscopy, and thermogravimetry, while morphological characterization was performed by scanning electron microscopy. H2 -CO2 and CH4 -CO2 mixtures separation were also evaluated by inverse gas chromatography. Both materials were able to separate these two mixtures. CO2 was the highest retained probe molecule due to the presence of quadrupole moment.

Surface chemistry of reduced graphene oxide: H-atom transfer reactions

In the present work, the surface chemistry of reduced graphene oxide, modified with hydrocarbon, hydroxyl, aldehyde and carboxyl groups is studied by means of computational chemistry. The simulations by ab-initio molecular dynamics show that the reactions depend on the proximity of chemical groups and possibilities for H-atom transfer and gas evolution. Defects in close proximity can also promote certain reactions, especially in case of good leaving groups as products (CO2, H2O, CH3OH, CO). Parts of the surface, rich in sp2 carbon atoms (i.e. regular graphene surface) can significantly decrease the scission energy of CC bonds from the leaving groups, compared to gas phase ethane molecule or to the corresponding CC- bonds located at the edge (or defect) of the two-dimensional carbon material. This effect is caused by the unpaired electron, formed after bond dissociation, joining the global π system and restoring of the regular graphene structure. Decarboxylation reactions are found to be energetically favorable at both edge and surface. Generally, reactions at the edge are found to be disfavored energetically if they involve the participation of a C atom from the surface of the two-dimensional carbon material.

Low-Concentration C2 H6 Capture Enabled by Size Matching in the Ultramicropore.

Low-concentration ethane capture is crucial for environmental protection and natural gas purification. The ideal physisorbent with strong C2 H6 interaction and large C2 H6 uptake at low-concentration level has rarely been reported, due to the large pKa value and small quadrupole moment of C2 H6 . Herein, we demonstrate the perfectly size matching between the ultramicropore (pore size of 4.6 Å) and ethane (kinetic diameter of 4.4 Å) in a nickel pyridine-4-carboxylate metal-organic framework (IISERP-MOF2), which enables the record-breaking performance for low concentration C2 H6 capture. IISERP-MOF2 exhibits the large C2 H6 adsorption enthalpy of 56.7 kJ/mol, and record-high C2 H6 uptake at low pressure of 0.01-0.1 bar and 298 K (1.8 mmol/g at 0.01 bar). Molecule simulations and C2 H6 -loading crystal structure analysis revealed that the maximized interaction sites in IISERP-MOF2 with ethane molecule originates the strong C2 H6 adsorption. The dynamic breakthrough experiments for gas mixtures of C2 H6 /N2 (1/999, v/v) and C2 H6 /CH4 (5/95, v/v) proved the excellent low-concentration C2 H6 capture performance.

Chemoenzymatic synthesis of 3-ethyl-2,5-dimethylpyrazine by L-threonine 3-dehydrogenase and 2-amino-3-ketobutyrate CoA ligase/L-threonine aldolase

Pyrazines are typically formed from amino acids and sugars in chemical reactions such as the Maillard reaction. In this study, we demonstrate that 3-ethyl-2,5-dimethylpyrazine can be produced from L-Thr by a simple bacterial operon. We conclude that EDMP is synthesized chemoenzymatically from L-Thr via the condensation reaction of two molecules of aminoacetone and one molecule of acetaldehyde. Aminoacetone is supplied by L-threonine 3-dehydrogenase using L-Thr as a substrate via 2-amino-3-ketobutyrate. Acetaldehyde is supplied by 2-amino-3-ketobutyrate CoA ligase bearing threonine aldolase activity from L-Thr when CoA was at low concentrations. Considering the rate of EDMP production, the reaction intermediate is stable for a certain time, and moderate reaction temperature is important for the synthesis of EDMP. When the precursor was supplied from L-Thr by these enzymes, the yield of EDMP was increased up to 20.2%. Furthermore, we demonstrate that this reaction is useful for synthesizing various alkylpyrazines.

TPE based aggregation induced emission fluorescent sensors for viscosity of liquid and mechanical properties of hydrogel

Two amphiphilic TPE E / Z isomers with aggregation induced emission (AIE) property have been synthesized and characterized. The logarithmic fluorescent intensity of the two molecules was in positive relationship with logarithmic viscosity of liquid. To note, the Z -TPE isomer exhibited more sensitivity in the viscosity of liquid sensing in comparison with the corresponding E -TPE counterpart (around 1.80 folds). Furthermore, two molecules could be used as fluorescent sensors for mechanical properties (viscosity and storage modulus) of hydrogel as well. In addition, two sensors displayed low cytotoxicity in normal tissue cell line (L929) within the concentration range of 2–10 µmol/L. These results potentially promised their applications as fluorescent sensors for mechanical properties in the fields of biological and biomedical. Amphiphilic tetraphenyl ethylene molecules (E-TPE and Z-TPE) realized fluorescent sensing of liquid viscosity and mechanical properties (viscosity and storage modulus).

Revisit Electrolyte Chemistry of Hard Carbon in Ether for Na Storage.

Hard carbons (HCs) as an anode material in sodium ion batteries present enhanced electrochemical performances in ether-based electrolytes, giving them potential for use in practical applications. However, the underlying mechanism behind the excellent performances is still in question. Here, ex situ nuclear magnetic resonance, gas chromatography–mass spectrometry, and high-resolution transmission electron microscopy were used to clarify the insightful chemistry of ether- and ester-based electrolytes in terms of the solid–electrolyte interphase (SEI) on hard carbons. The results confirm the marked electrolyte decomposition and the formation of a SEI film in EC/DEC but no SEI film in the case of diglyme. In situ electrochemical quartz crystal microbalance and molecular dynamics support that ether molecules have likely been co-intercalated into hard carbons. To our knowledge, these results are reported for the first time. It might be very useful for the rational design of advanced electrode materials based on HCs in the future.

Extraction of Sr2+ from aqueous solutions using an asymmetric pulsed current-assisted electrochemical method

In this paper, 4′-aminobenzo-18-crown-6 ether was grafted onto the surface of carbon felt via a diazotization reaction, and a composite material (CE@CF) was obtained. Then, CE@CF was used as an electrode to extract Sr2+ from aqueous solutions and simulated seawater by an asymmetric pulsed current-assisted electrochemical (AP-CE) method. Due to the excellent conductivity of carbon felt and the selectivity of crown ether molecules, the CE@CF electrode exhibited excellent electrochemical extraction performance. Under the optimal alternating potential, the maximum removal efficiency and maximum adsorption capacity of Sr2+ reached 99.5% and 668.9 mg g−1, respectively. The Sr2+ ions adsorbed on the surface of the CE@CF electrode could be desorbed by applying a positive voltage without an eluent, and the CE@CF electrode displayed good recyclability. This work provides an effective strategy for developing covalently-decorated crown ether carbon felt electrodes. The AP-CE method is of great significance for the selective electrosorption of metal ions.

New insights on ultrafast Na[solv]+ coinserted graphite driven by an electric field

Sodium ions (Na+) and ether electrolyte co-inserted graphite possesses a considerable volume expansion effect. However, the mechanism fails to clearly explain its stability. In response to this deficiency, the co-inserted reaction is proposed, which is affected by the Lorentz force of the applied electric field under the high-current condition. The Na+ ions are separated out, while the ethylene glycol dimethyl ether molecules remain between the graphite layers. This insight provides a reasonable explanation for the extraordinary stability of this material. In situ X-ray diffraction and density functional theory calculations confirm the separation and release of Na+. On the basis of this result, unmodified commercial graphite was stably cycled 6400 times at a current density of up to 10 A g−1, and the capacity retention rate was as high as 97.2%. The full battery assembled in the laboratory has a maximum output power of 14,846 W kg−1 and an output energy density of 103 W h kg−1 (relative to the weight of anodic and cathodic active materials). The new mechanism provides innovative ideas for the design of large-scale energy storage devices.

Understanding the electronic metal-support interactions of the supported Ni cluster for the catalytic hydrogenation of ethylene

• The influences of electronic metal-support interactions (EMSI) on the catalytic hydrogenation of ethylene on three supported Ni catalysts (i.e. Ni 4 /TiO 2 , Ni 4 /CeO 2 and Ni 4 /BNO) have been studied systematically via DFT simulations. • When Ni cluster is loaded on the three substrates, the Ni cluster exhibits positive charge state with different charge density due to the EMSI. • The charges on Ni clusters are almost linearly correlated to both the adsorption energy of ethylene and the charge transfer from Ni to ethylene. • The charges on Ni could further affect the performance of the catalyst during the hydrogenation process of ethylene, where the Ni cluster with more electrons is beneficial for the hydrogenation reaction. • The coverage effect of hydrogen is also evaluated. At high H coverage, both the kinetics and thermodynamics of the hydrogenation reaction would be significantly promoted. The electronic metal-support interaction (EMSI) has a very profound impact on the catalytic activity of supported catalysts. In this paper, density functional theory calculations were utilized to understand the effect of EMSI between Ni cluster (Ni 4 ) and three substrates (CeO 2 , TiO 2 , and BNO) on the catalytic hydrogenation of ethylene. When Ni cluster was anchored on the surface of support, visibly electron transfer from Ni to substrate was observed, leading to positively charged Ni clusters with the sequence of Ni 4 /TiO 2 > Ni 4 /CeO 2 > Ni 4 /BNO. During the ethylene hydrogenation reaction, the electron rich Ni 4 /BNO exhibits superior performance in activating of both H 2 and ethylene molecules, while the electron deficient Ni 4 /TiO 2 shows the worst activation among the three catalysts. As a consequence, the activation energies of ethylene hydrogenation follow the same sequence of the charge state on the supported Ni clusters at both low and high H coverages. Our results suggest that the EMSI between metal nanoparticles and support materials is capable of tuning the charge state and electron density of supported metals, which further determines the activity of the catalyst. This work provides a potential approach for design new catalysts with desired activity by utilizing appropriate support materials.

GSH-Sensitive Nanoscale Mn3+-Sealed Coordination Particles as Activatable Drug Delivery Systems for Synergistic Photodynamic-Chemo Therapy.

Activatable nanoscale drug delivery systems (NDDSs) are promising in maximizing cancer specificity and anticancer efficacy, and a multifunctional metal-organic nanomaterial is one of the new star NDDSs which requires further exploration. Herein, a novel DOX@MnCPs/PEG NDDSs were constructed by first synthesizing Mn3+-sealed coordination particles (MnCPs), modified with a targeted PEGylated polymer, and then loading anticancer drug doxorubicin (DOX). MnCPs were prepared from the assembly of Mn3+ ions and hematoporphyrin monomethyl ether (HMME) molecules. Furthermore, MnCPs had an average size of ∼100 nm and a large surface area (∼52.6 m2 g-1) and porosity (∼3.6 nm). After the loading of DOX, DOX@MnCPs/PEG exhibited a high DOX-loading efficacy of 27.2%, and they reacted with glutathione (GSH) to confer structural collapse, leading to the production of Mn2+ ions for enhanced magnetic resonance imaging (MRI), free HMME for augmented photodynamic effect, and free DOX for chemotherapy. As a consequence, these DOX@MnCPs/PEG NDDSs after intravenous injection showed efficient tumor homing and then exerted an obvious suppression for tumor growth rate by synergistic photodynamic-chemo therapy in vivo. Importantly, most of the DOX@MnCPs/PEG NDDSs could be gradually cleared through the renal pathway, and the remaining part could slowly be metabolized via the feces, enabling high biosafety. Therefore, this work provides a type of GSH-sensitive NDDS with biosafety, caner specificity, and multifunctionality for high synergistic treatment efficacy.

Molecular Selectivity of CH4–C2H6 Mixed Hydrates: A GCMC Study

In this paper, we report the first grand canonical Monte Carlo simulation study aiming at characterizing the competitive trapping of CH4 and C2H6 molecules into clathrate hydrates under temperature conditions typical of those encountered at the surface of Titan. Various compositions of the fluid in contact with the clathrate phase have been considered in the simulations, including pure methane, pure ethane, and mixed fluids made of various methane/ethane ratios. The trapping isotherms obtained from the simulations clearly show that ethane molecules can be enclathrated at lower pressures than methane molecules. In addition, they provide evidence that the methane molecules can occupy both small and large cages of the clathrate lattice, whereas the ethane molecules have a strong preference for the large cages, in accordance with experimental conclusions. However, increasing the pressure may also lead to the trapping of ethane in the small cages of the clathrates, leading to a possible competition between methane and ethane molecules for these small cages at high pressure, if both molecules are concomitantly present in the fluid phase. The abovementioned features could strongly influence the composition of a mixed methane/ethane fluid phase in contact with the clathrate phase, which might thus be first impoverished in ethane before methane starts getting trapped into the clathrate. However, this conclusion strongly depends on the clathrate structure considered in the simulations.

Surface modification of 2-D Ti3C2Tx for the effective capture and elimination of acetaldehyde as a co-catalyst: A theoretical and experimental study

As a newly explored 2-D material with metallic conductivity, Ti3C2 has drawn much attention as co-catalysts for the photocatalytic oxidation (PCO) of indoor air pollutants. Herein, we implement the periodic density functional theory calculations to study the interaction between Ti3C2 and acetaldehyde molecules and Ti atoms in Ti3C2 are identified as the active sites for the capture of acetaldehyde molecules. When fully saturated with surface terminators (Ti3C2T2, T stands for -F, -O and -OH groups), the Ti3C2F2 and Ti3C2O2 have weak affinity to acetaldehyde while Ti3C2(OH)2 could provide moderate adsorption strength by forming H-bonds with acetaldehyde. Creating T vacancies in Ti3C2T2 monolayers through surface modification could effectively improve its affinity to acetaldehyde with the adsorption energy increasing from 0.281, 0.235 and 0.878 to 1.750, 1.830 and 1.960 eV for Ti3C2Fx, Ti3C2Ox and Ti3C2(OH) x, respectively. The positive effect of Ti3C2Tx as a co-catalyst is also verified by constructing Ti3C2Tx-TiO2 composite photocatalysts. The introduction of Ti3C2Tx flakes effectively promote the PCO of acetaldehyde by improving the adsorption of target molecules and accelerate the separation of electron-hole pairs in TiO2. This work provides a promising 2-D Ti3C2Tx material as a co-catalyst for the capture and photocatalytic elimination of indoor air pollutants.

Density Functional Theory Guide for an Allyl Monomer Polymerization Mechanism: Photoinduced Radical-Mediated [3 + 2] Cyclization.

Polymerization of allyl ether monomers has previously been considered a free-radical addition polymerization mechanism, but it is difficult to achieve because of the high electron density of their double bond. To interpret the mechanism of photopolymerization, we therefore proposed a radical-mediated cyclization (RMC) reaction, which has been validated by results from quantum chemistry calculations and real-time infrared observation. Our RMC reaction begins with the radical abstracting one allylic hydrogen atom from the methylene group of allyl ether to generate an allyl ether radical with a delocalized π33 bond. Then, the radical reacts with the double bond of a second allyl ether molecule to form a five-membered cyclopentane-like ring (CP) radical. The CP radical abstracts a hydrogen atom from a third ether molecule. At last, a new allyl ether radical is generated and the next circulation as chain propagation begins. The distortion/interaction model was employed to explore the transient state of reaction, and real-time infrared was chosen to clarify the RMC reaction mechanism initiated by different photoinitiators. These results demonstrated that the RMC mechanism can give new insights into these fundamental processes.

(Invited) Enhancement of Oxidation of Dimethyl Ether through Applicationof Metal-Oxide-Supported Noble Metal Catalytic Nanoparticles: Comparison to Behavior of Other Simple Organic Fuels

There has been growing interest in utilizing small (simple) organic molecules, as alternative fuels to hydrogen, in electrochemical energy conversion systems. In addition to ethanol (biofuel), that can be ideally oxidized to carbon dioxide thus delivering twelve electrons, recent important systems include dimethyl ether as well. But realistically the respective reaction is rather slow at ambient conditions. Obviously, there is a need to develop novel electrocatalytic materials.Platinum has been recognized as the most active catalytic metal towards oxidation of ethanol at low and moderate temperatures. But Pt anodes are readily poisoned by the strongly adsorbed intermediates, namely by CO-type species, requiring fairly high overpotentials for their removal. To enhance activity of Pt catalysts towards methanol and ethanol oxidation, additional metals including ruthenium, tin, molybdenum, tungsten or rhodium are usually introduced as the alloying component. More recently it has been demonstrated that catalytic activity of platinum-based nanoparticles towards electrooxidation of ethanol has been significantly enhanced through interfacial modification with ultra-thin monolayer-type films of metal oxo species of tungsten, titanium or zirconium.We pursue a concept of utilization of zirconia nad mixed metal (e.g. zirconium/tungsten or titanium/tungsten) oxide matrices for supporting and activating noble metal nanoparticles (e.g. PtRu) during electrooxidation of dimethyl ether relative to methanol, formic acid and ethanol. Among important issues is incorporation of additional metal (e.g. Rh or Pt) nanostructures capable of weakening, or even breaking, the C-C and C-O bonds in the ethanol and dimethyl ether molecules. On the other hand, rhodium itself is not directly electrocatalytic toward oxidation of ethanol. The oxides and noble metal nanoparticles have been deposited in a controlled manner using the layer-by-layer method. Remarkable increases of electrocatalytic currents measured under voltammetric and chronoamperometric conditions have been observed. The most likely explanation takes into account possibility of specific interactions of noble metals with transition metal oxide species as well as existence of active hydroxyl groups in the vicinity of catalytic noble metal sites. In addition, formation of “nanoreactors” where ethanol and dimethyl ether are partitioned (at Rh, Pt or Pd) to methanolic residues and further oxidized at PtRu cannot be excluded.

μ-Methyl-ene-bis-[di-bromido(diethyl ether-κO)aluminium(III)]: crystal structure and chemical exchange in solution.

In the title compound, [Al2Br4(CH2)(C4H10O)2], the mol-ecule lies on a crystallographic twofold axis passing through the bridging C atom. Each AlIII atom is four-coordinate, being bonded to two bromide ions, bridging the CH2 group as well as the oxygen atom of a diethyl ether ligand in a slightly distorted tetra-hedral arrangement with angles ranging from 101.52 (8) to 116.44 (5)°. The Al-CH2-Al angle, 118.4 (2)°, is the smallest observed for a structure where this moiety is not part of a ring. In the crystal, weak C-H⋯Br inter-actions, characterized as R 2 2(12) rings, link the mol-ecules into ribbons in the [101] direction. The title compound is monomeric and coordinatively saturated in the solid state, as each aluminum is four-coordinate, but in solution the ether mol-ecules from either or both Al atoms can dissociate, and would be expected to rapidly exchange, and this is supported by NMR data.

Oxidation of Ethanol in Cu-Faujasites Studied by IR Spectroscopy

In this study, IR studies of the coadsorption of ethanol and CO on Cu+ cations evidenced the transfer of electrons from ethanol to Cu+, which caused the lowering of the frequency of the band attributed to CO bonded to the same Cu+ cation due to the more effective π back donation of d electrons of Cu to antibonding π* orbitals of CO. The reaction of ethanol with acid sites in zeolite HFAU above 370 K produced water and ethane, polymerizing to polyethylene. Ethanol adsorbed on zeolite Cu(2)HFAU containing acid sites and Cu+exch also produced ethene, but in this case, the ethene was bonded to Cu+ and did not polymerize. C=C stretching, which is IR non-active in the free ethene molecule, became IR active, and a weak IR band at 1538 cm−1 was present. The reaction of ethanol above 370 K in Cu(5)NaFAU zeolite (containing small amounts of Cu+exch and bigger amounts of Cu+ox, Cu2+exch and CuO) produced acetaldehyde, which was further oxidized to the acetate species (CH3COO−). As oxygen was not supplied, the donors of oxygen were the Cu species present in our zeolite. The CO and NO adsorption experiments performed in Cu-zeolite before and after ethanol reaction evidenced that both Cu+ox and Cu2+ (Cu2+exch and CuO) were consumed by the ethanol oxidation reaction. The studies of the considered reaction of bulk CuO and Cu2O as well as zeolites, in which the contribution of Cu+ox species was reduced by various treatments, suggest that ethanol was oxidized to acetaldehyde by Cu2+ox (the role of Cu+ox could not be elucidated), but Cu+ox was the oxygen donor in the acetate formation.

Interaction of ethane with singlet oxygen: A theoretical study of potential energy surfaces

A study of the C2H6+O2 reaction system was carried out using ab initio quantum chemistry methods. The main reaction and quenching channels were identified, corresponding activation energies were calculated, and the pathways of the minimum reaction energy were constructed. It was found that the reaction channels of ethane molecule with singlet delta oxygen proceed with a lower barrier than with the oxygen molecule in the ground state. The reaction of ethane with singlet sigma oxygen, in turn, proceeds through the dissociation of the O2 molecule; however, the quenching channel is still possible because of the intersystem crossings. Based on the obtained data, the appropriate reactions rate constants can be estimated by using variational and nonadiabatic transition state theories.

An ab initio study of some halogen-bonded complexes containing cyclic ethers

The binary complexes formed between the dihalogens fluorine, chlorine and bromine, and the cyclic ethers oxirane, oxetane, tetrahydrofuran and tetrahydropyran, have been studied by means of ab initio calculations at the second-order level of Møller–Plesset perturbation theory. The properties of interest are the interaction energies, the intermolecular geometries, the perturbations of the intramolecular dihalogen and ether geometries, the wavenumber shifts of the dihalogen and ether molecules, and the variations of the natural atomic charges resulting from complexation. The trends observed are discussed in terms of the physical properties of the interacting monomers, such as the polarizabilities of the dihalogen molecules and the gas phase basicities of the ethers.