Ethylenic Bond Research Articles

Substituent effects on the stretching vibration frequencies of C=C bridge bond in aryl ethylene with furyl or thienyl group

AbstractTo explore the substituent effects on the stretching vibration frequencies νC=C of C=C bridge bond in 1‐furyl/thienyl‐2‐aryl ethylene XCH=CHArYs, 60 samples of XCH=CHArYs were synthesized, and their infrared absorption spectra were recorded. The regression analyses between the νC=C values of XCH=CHArYs and the substituent parameters of X and Y were made in detail. Finally, an optimality equation (shown as Equation 3) quantifying the νC=C values of XCH=CHArYs was obtained. It shows that the substituent effects on the νC=C values of XCH=CHArYs mainly reflect in Hammett constant of X and the excited‐state substituent constants of X and Y. Among the parameters in Equation (3), the excited‐state substituent constant of X contributes the most to the νC=C values of XCH=CHArYs as seen from the fraction contributions. On the whole, the contribution of X to the νC=C values of XCH=CHArYs is larger than that of Y.

Cucurbit[7]uril‐Encapsulation‐Controlled Supramolecular Photoproduct and Radical Fluorescence Emission

Herein, a host-guest interaction-controlled photoproduct created by using cucurbit[7]uril (Q[7])-based pseudorotaxane structures is reported. The assembly exhibited controlled behavior towards the reduction of the ethylene (C=C) bond in the tetrakis(pyridin-4-yl)ethylene (TPyE) guest molecule under UV light irradiation. This can be attributed to the Q[7] encapsulation masking the four pyridinium arms of the guest, which inhibits planarization of the TPyE core to form the cyclization product. In particular, the strong affinity of Q[7] for the butyl-substituted guest (TPyE-4C) led to an unusual radical fluorescence emission of the photoirradiation-triggered intermediate of the guest molecule being observed in aqueous solution. This work provides a valuable paradigm and new insight for macrocycle-based host-guest interactions in supramolecular catalysis and luminescent radical materials.

Variational Density Functional Calculations of Excited States: Conical Intersection and Avoided Crossing in Ethylene Bond Twisting.

Theoretical studies of photochemical processes require a description of the energy surfaces of excited electronic states, especially near degeneracies, where transitions between states are most likely. Systems relevant to photochemical applications are typically too large for high-level multireference methods, and while time-dependent density functional theory (TDDFT) is efficient, it can fail to provide the required accuracy. A variational, time-independent density functional approach is applied to the twisting of the double bond and pyramidal distortion in ethylene, the quintessential model for photochemical studies. By allowing for symmetry breaking, the calculated energy surfaces exhibit the correct topology around the twisted-pyramidalized conical intersection even when using a semilocal functional approximation, and by including explicit self-interaction correction, the torsional energy curves are in close agreement with published multireference results. The findings of the present work point to the possibility of using a single determinant time-independent density functional approach to simulate nonadiabatic dynamics, even for large systems where multireference methods are impractical and TDDFT is often not accurate enough.

Dicoordinate Au(I)-Ethylene Complexes as Hydroamination Catalysts.

A series of gold(I)–ethylene π-complexes containing a family of bulky phosphine ligands has been prepared. The use of these sterically congested ligands is crucial to stabilize the gold(I)–ethylene bond and prevent decomposition, boosting up their catalytic performance in the highly underexplored hydroamination of ethylene. The precatalysts bearing the most sterically demanding phosphines showed the best results reaching full conversion to the hydroaminated products under notably mild conditions (1 bar of ethylene pressure at 60 °C). Kinetic analysis together with density functional theory calculations revealed that the assistance of a second molecule of the nucleophile as a proton shuttle is preferred even when using an extremely congested cavity-shaped Au(I) complex. In addition, we have measured a strong primary kinetic isotopic effect that is consistent with the involvement of X–H bond-breaking events in the protodeauration turnover-limiting step.

Polydatin: A Critical Promising Natural Agent for Liver Protection via Antioxidative Stress.

Polydatin, one of the natural active small molecules, was commonly applied in protecting and treating liver disorders in preclinical studies. Oxidative stress plays vital roles in liver injury caused by various factors, such as alcohol, viral infections, dietary components, drugs, and other chemical reagents. It is reported that oxidative stress might be one of the main reasons in the progressive development of alcohol liver diseases (ALDs), nonalcoholic liver diseases (NAFLDs), liver injury, fibrosis, hepatic failure (HF), and hepatocellular carcinoma (HCC). In this paper, we comprehensively summarized the pharmacological effects and potential molecular mechanisms of polydatin for protecting and treating liver disorders via regulation of oxidative stress. According to the previous studies, polydatin is a versatile natural compound and exerts significantly protective and curative effects on oxidative stress-associated liver diseases via various molecular mechanisms, including amelioration of liver function and insulin resistance, inhibition of proinflammatory cytokines, lipid accumulation, endoplasmic reticulum stress and autophagy, regulation of PI3K/Akt/mTOR, and activation of hepatic stellate cells (HSCs), as well as increase of antioxidant enzymes (such as catalase (CAT), glutathione peroxidase (GPx), glutathione (GSH), superoxide dismutase (SOD), glutathione reductase (GR), and heme oxygenase-1 (HO-1)). In addition, polydatin acts as a free radical scavenger against reactive oxygen species (ROS) by its phenolic and ethylenic bond structure. However, further clinical investigations are still needed to explore the comprehensive molecular mechanisms and confirm the clinical treatment effect of polydatin in liver diseases related to regulation of oxidative stress.

Synthesis and characteristic applications of silicon resins for the modifying agent in heat conduction

Heat energy retention and dissipation have become key points of global smart textiles in recent years. This study describes the designing of silicon resin by using a sol–gel process, which acts as the modifying agent for siloxane substrate. The modifying agent was effectively blocked by silicon resin mixed with the ethylene or aluminum bond group, to control the molecular weight. Advanced polymer chromatography confirmed that the number average molecular weight (Mn) of silicon resin is 41,301 g mol−1, the weight average molecular weight (Mw) is 47,982 g mol−1, and the molecular weight distribution is 1.1617, which is relatively narrow. When the addition of vinyl groups is 5%, the silicone resin Mn decreases to 18,906 g mol−1 and Mw decreases to 28,641 g mol−1. When the addition of aluminum bond groups is 5%, the silicone resin Mn decreases to 17,497 g mol−1 and Mw decreases to 27,114 g mol−1. The result of thermogravimetric analysis shows that the pyrolysis temperature rises from 265.43°C to 266.17°C after the ethylene is added to the silicon resin, and the index of heat tolerance increases from 179.14°C to 191.38°C. After the addition of aluminum bond groups, the pyrolysis temperature rises from 265.43°C to 309.37°C, and the index of heat tolerance increases from 179.14°C to 193.09°C, meaning the silicone resin has higher thermal stability.

MODIFIED CARBON-CONTAINING ALUMINUM CHLORIDE CATALYSTS


 
 
 
 Catalytic systems based on metallic aluminum Al and carbon tetrachloride CCl4, modified by Mg, CuCl2, NiCl2, MgCl2, have been developed. EPR and IR spectroskopiya studies of synthesized samples of catalysts were carried out. Based on the EPR spectrum, the presence of a Cu-C -bond was revealed in the Al + CCl4 catalyst with the modifying additive CuCl2.
 Using IR spectra, it was determined that catalysts without modifiers and with modifiers are a mixture of two complexes based on Corbin-type structures. In this case, the catalysts differ in the ratio of the main structures with double C=C and triple C≡C bonds. Catalysts with modifying additives NiCl2 and Mg have significantly fewer of these structures than a catalyst without modifiers, and a catalyst with Mg is characterized by the smallest number of structures containing C=C bonds.
 It is shown that the catalysts obtained on the basis of Al and CCl4 and its various modifications are complexes, the carbon-containing part of which is represented by polycumulene and polyine structures containing ethylene and acetylene bonds.
 
 
 

Synthesis, structure and cytotoxic activity of trans-[PtCl2(EugH)(Caffeine)] and [PtCl(Eug)(Caffeine)] (EugH: eugenol) complexes

Interaction between K[PtCl3(EugH)] (1) and [PtCl(Eug)]2 (2) with Caf afforded two new complexes, trans-[PtCl2(EugH)(Caf)] (3) and [PtCl(Eug)(Caf)] (4), respectively. The procedure to synthesize complex 2 was improved. The structures of two new complexes were characterized by elemental analyses, MS, IR, 1H NMR and NOESY spectroscopies. The result indicated that EugH coordinates with Pt(II) at ethylenic double bond of the allyl group in complex 3, but in complex 4 it is deprotonated and bound with Pt(II) at both the double bond and C5 of the benzene ring. The donor N of caffein is in trans-position in 3 and in cis-position in 4 with respect to the ethylenic double bond. In chloroform solvent, 4 exists in two forms 4a and 4b corresponding to the strong intermolecular hydrogen bond Cl3C-H…ClPt(II) and the strong halogen bond Cl2HC-Cl…Pt(II). The result of testing cytotoxicity of 3 and 4 against four human cancer cells KB, Lu, Hep-G2 and MCF7 showed that complex 3 exhibits good activities on the KB and Hep-G2 with IC50 values of 81,03 and 89,29 μg/mL, respectively.

Bis{N'-[3-(4-nitro-phen-yl)-1-phenyl-prop-2-en-1-yl-idene]-N-phenyl-carbamimido-thio-ato}zinc(II): crystal structure, Hirshfeld surface analysis and computational study.

The title zinc bis-(thio-semicarbazone) complex, [Zn(C22H17N4O2S)2], comprises two N,S-donor anions, leading to a distorted tetra-hedral N2S2 donor set. The resultant five-membered chelate rings are nearly planar and form a dihedral angle of 73.28 (3)°. The configurations about the endocyclic- and exocyclic-imine bonds are Z and E, respectively, and that about the ethyl-ene bond is E. The major differences in the conformations of the ligands are seen in the dihedral angles between the chelate ring and nitro-benzene rings [40.48 (6) cf. 13.18 (4)°] and the N-bound phenyl and nitro-benzene ring [43.23 (8) and 22.64 (4)°]. In the crystal, a linear supra-molecular chain along the b-axis direction features amine-N-H⋯O(nitro) hydrogen bonding. The chains assemble along the 21-screw axis through a combination of phenyl-C-H⋯O(nitro) and π(chelate ring)-π(phen-yl) contacts. The double chains are linked into a three-dimensional architecture through phenyl-C-H⋯O(nitro) and nitro-O⋯π(phen-yl) inter-actions.

1-{(E)-[4-(4-Hy-droxy-phen-yl)butan-2-yl-idene]amino}-3-phenyl-thio-urea: crystal structure, Hirshfeld surface analysis and computational study.

The title thio-urea derivative, C17H19N3OS, adopts a U-shaped conformation with the dihedral angle between the terminal aromatic rings being 73.64 (5)°. The major twist in the mol-ecule occurs about the ethane bond with the Ci-Ce-Ce-Cb torsion angle being -78.12 (18)°; i = imine, e = ethane and b = benzene. The configuration about the imine bond is E, the N-bound H atoms lie on opposite sides of the mol-ecule and an intra-molecular amine-N-H⋯N(imine) hydrogen bond is evident. In the mol-ecular packing, hydroxyl-O-H⋯S(thione) and amine-N-H⋯O hydrogen bonding feature within a linear, supra-molecular chain. The chains are connected into a layer in the ab plane by a combination of methyl-ene-C-H⋯S(thione), methyl-ene-C-H⋯O(hydrox-yl), methyl-C-H⋯π(phen-yl) and phenyl-C-H⋯π(hy-droxy-benzene) inter-actions. The layers stack without directional inter-actions between them. The analysis of the calculated Hirshfeld surface highlights the presence of weak methyl-C-H⋯O(hydrox-yl) and H⋯H inter-actions in the inter-layer region. Computational chemistry indicates that dispersion energy is the major contributor to the overall stabilization of the mol-ecular packing.

Multi-stimuli-responsive fluorescence of axially chiral 4-ene-β-Diketones

A unique series of simple, smart, and chiral binaphthalene-substituted 4-ene-β-diketones molecules has been designed and prepared. Their optical properties, charge contribution, and transition process highly depend on their chemical structures. These π-conjugated materials are highly emissive in both solution and solid (emission quantum yield up to 68%), owing to the inhibition of enol-keto tautomerization and the effect of steric hindrance from binaphthalene. Through ethylenic bond hydrolysis, they can be used for not only cation/anion sensing but also chiral amino acids recognition. Moreover, at low concentrations, they have little cytotoxicity to living cells and can stain cytoplasm. Therefore, they afford a new platform in the design of multi-stimuli-responsive, smart, and chiral materials.

Radical-Triggered Reaction Mechanism of the Green-to-Red Photoconversion of EosFP.

Reaction intermediates in the green-to-red photoconversion of the photochromic fluorescent protein EosFP have been observed using high-intensity continuous blue illumination. An intermediate was identified through light-induced accumulation that continues to convert the green form in subsequent darkness, putatively containing a tyrosyl radical, albeit with anomalously shifted features in both the electronic and FTIR spectra. Lowering the pH to 5.5 significantly delays the decay of this tyrosyl intermediate, which is accompanied by Stark-shifted features in the electronic spectra of reactants and products. Vibrational mode assignments for the high-frequency and fingerprint FTIR spectral regions of the reaction intermediates support a proposed sequence of events where the newly formed Cα═Cβ ethylenic bond precedes modifications on the His-62 imidazole ring and confirms a C═O(NH2) product group on Phe-61. We propose a reaction mechanism that involves tyrosyl generation via singlet excited-state-mediated oxidation which subsequently triggers the covalent reactions by oxidation of the green chromophore.

Structure and mechanistic relevance of Ni2+–NO adduct in model HC SCR reaction over NiZSM-5 catalyst – Insights from standard and correlation EPR and IR spectroscopic studies corroborated by molecular modeling

Mechanistic aspects of model selective catalytic reduction (SCR) of NO with C2H4 over Ni/ZSM-5 zeolite were investigated by means of advanced correlation EPR/HYSCORE and IR time-resolved Rapid-Scan 2D COS techniques combined with DFT/CASSCF calculations. It was shown that two types of the active centers, bare isolated Ni2+ and dual oxo Ni2+–O2––Ni2+, are involved in this reaction, acting in different ways. NO interaction with the former center results in a Ni2+–NOδ+ moiety, the unique nature of which was ascertained by HYSCORE studies, and accounted for by the spin-polarized DFT/CASSCF calculations in detail. The electrophilic nature of the bound NOδ+ moiety is crucial for its successful insertion into the >C=C< bond of ethylene. This process involves formation of isolated nickel adducts with the co-ligated C2H4 and NO molecules, and the resultant cyanide and isocyanate intermediates are next hydrolyzed into ammonia or oxidized by NOx. The dual nickel-oxo centers provide the active sites for development of nitrate/nitro species and next mixed-ligand nitrate/nitro-ammonia adducts. Selective catalytic reduction results from the NOx/cyanide and nitrate/nitro-ammonia routes, which both are featured by reversal of the partial charge on the nitrogen atom from positive in Nδ+O into negative in –CNδ–/–Nδ–CO or Nδ–H3, giving rise to the key nitrogen charge comproportionation step. In both pathways, the nickel(II) mononitrosyls play a pivotal function as the primary source of the N–containing intermediates (–CN/–NCO/NH3). It acts also as a species hindering the undesired oxidation of C2H4 by dioxygen.

Acetylene/Ethylene Separation and Solid-State Structural Transformation via [2 + 2] Cycloaddition Reactions in 3D Microporous ZnII Metal-Organic Frameworks.

Purification of ethylene by removing acetylene from an ethylene/acetylene (99/1 v/v) mixture is a challenging task in the petrochemical industry. Our effort toward finding new porous materials that can selectively uptake acetylene resulted in two 3D metal-organic frameworks. Compound 1, {[Zn(p-pda)(bpee)]} (p-pda = p-phenylenediacetate and bpee = 1,2-bis(4-pyridyl)ethylene) turned out to be a nonporous structure due to the presence of a bulky and rigid aromatic ring in the p-pda ligand. Interestingly, replacement of p-pda with succinic acid yields the microporous framework {[Zn2(μ3-OH)(suc)1.5(bpee)]·CH3OH·2H2O} (2; suc = succinate), which offers a 1D channel along the a direction occupied by guest methanol and water molecules. Remarkably, the desolvated framework of 2 shows selective uptake of C2H2 over other gas molecules such as C2H4, C2H6, CO2 and CH4 at 293 K. An ideal absorbed solution theory (IAST) study predicts a high selectivity value for acetylene adsorption over the other gas molecules mentioned above. The efficiency of removal of acetylene from ethylene/acetylene mixtures containing 1% acetylene was established through a column breakthrough experiment performed at room temperature. The performance of our material in the purification of ethylene by removing acetylene is comparable with those reported in the literature. In the frameworks of both 1 and 2, the ethylenic double bonds of adjacent bpee linkers are aligned parallel and readily undergo [2 + 2] cycloaddition reactions upon UV-light irradiation to yield {[Zn2(p-pda)2(rctt-tpcb)]} (1IR) and {[Zn4(μ3-OH)2(suc)3(rctt-tpcb)]·2CH3OH·4H2O} (2IR), respectively (rctt-tpcb = regio-cis,trans,trans-tetrakis(4-pyridyl)cyclobutane). Photochemical structural transformations of 100% were observed in single-crystal to single-crystal fashions, which were also supported by 1H NMR spectroscopy. The structures of both 2 and 2IR underwent temperature-dependent reversible structural transformations, which was confirmed by SCXRD and DSC analysis. Selective C2H2 uptake of the dehydrated framework of 2IR was also examined, which demonstrates results similar to those of 2.

Structural, Hirshfeld and DFT studies of conjugated D-π-A carbazole chalcone crystal.

A new conjugated carbazole chalcone compound, (E)-3-[4-(9,9a-di-hydro-8aH-carbazol-9-yl)phen-yl]-1-(4-nitro-phen-yl)prop-2-en-1-one (CPNC), C27H18N2O3, was synthesized using a Claisen-Schmidt condensation reaction. CPNC crystallizes in the monoclinic non-centrosymmetric space group Cc and adopts an s-cis conformation with respect to the ethyl-enic double bonds (C=O and C=C). The crystal packing features C-H⋯O and C-H⋯π inter-actions whose percentage contribution was qu-anti-fied by Hirshfeld surface analysis. Quantum chemistry calculations including geometrical optimization and mol-ecular electrostatic potential (MEP) were analysed by density functional theory (DFT) with a B3LYP/6-311 G++(d,p) basis set.

Post-polymerization modification of Poly(vinylcyclopropanes): A potential route to periodic copolymers

Poly(1,1-disubstituted-2-vinylcyclopropanes) were submitted to various substitution and addition reactions in order to modify the side chain and ethylenic moiety within the polymer backbone. Explicitly, bromination, epoxidation and thiol-ene addition reactions were performed on the ethylenic bond that is present in the main chain of poly(vinycyclopropanes) with varying ester and amide side chains. Bromination and epoxidation reactions proceeded with up to 90% conversion, while thiol-ene additions resulted in substantially lower conversions, i.e. <50%. The scope of this study is to reveal the potential of 1,1-disubstituted-2-vinylcyclopropanes as appealing monomers for the efficient synthesis of periodic copolymers with precise positioning of substituents within the constitutional repeating units.

Photochemical cycloaddition and temperature-dependent breathing in pillared-layer metal–organic frameworks

Single crystallinity of metal–organic frameworks (MOFs) enables the studies of their flexible behaviors with atomic precision. Here, we investigated the structural transformations triggered by photochemical cycloaddition and with temperature-dependent breathing in a series of pillared-layer MOF structures using a variety of pyrazolecarboxylate linkers for the layers and bipyridyl linkers as the pillars. The ethylenic double bonds from the pillars in close proximity undergo quantitative and seteroselective photochemical [2 + 2] cycloaddition upon UV irradiation, transforming the MOFs into structures with cyclobutane-based pillars. Furthermore, reversible breathing of the new pillared-layer MOF was evidenced by the 10.8% unit cell parameter change along c axis upon temperature change between 298 and 173 K. As revealed by single crystal X-ray diffraction, this transformation originates from the relative flattening of the wavy layers upon cooling. These two different types of characteristic structural transformations responding to inherent reactions and external stimuli happen at single crystalline state, providing a well-defined robust system with controlled flexibility.

Descriptors for terpene esters from chromatographic and partition measurements: Estimation of human odor detection thresholds

We have used gas chromatographic retention data together with other data to obtain Abraham descriptors for 30 terpene esters. These include the air-water partition coefficient, as log Kw, for which no experimental values are available for any terpene ester. The other descriptors are the ester dipolarity, S, the hydrogen bond basicity, B, (the ester hydrogen bond acidity is zero for the esters studied), and L the logarithm of the air-hexadecane partition coefficient. Both S and B are larger than those for simple aliphatic esters, as expected from the terpene ester structures that include ring systems and ethylenic double bonds. These descriptors can then be used to obtain a large number of physicochemical and environmental properties of terpene esters. We have analyzed experimental results on human odor detection thresholds and have constructed another equation for the calculation of these thresholds, to go with a previous equation that we have reported. Then the descriptors for terpene esters can be used to estimate the important odor detection thresholds.

Hydrocarbons as Proton Receptors and Evidences of Unconventional and Unusual π···H, p-π···H and C···H Hydrogen Bonds

In this current work, a brief historical narrative of the most popular theories that decisively aid in the comprehension of the hydrogen bond formation is presented. As is well-known, the valence bond theory was efficiently suitable to certify the electronic structure of Lewis acids/bases, in particular the fluorine, oxygen and nitrogen as high charge density sources, and as such the homodimers of 2(HF), 2(H 2 O) and 2(NH 3 ) were framed as reference systems. Regarding the π bonds of acetylene and ethylene as well as the p-π (pseudo unsaturated bond) clouds of cyclopropane, these compounds belong to a distinct group of proton receptors by which the π···H, p-π···H and C···H hydrogen bonds are formed. DOI: http://dx.doi.org/10.17807/orbital.v11i3.1399

Chemical analysis of Ricinus communis L. (Euphorbiaceace) seed kernel extract and its in-vitro toxicity in two Podagrica Species (Coleoptera: Chrysomelidae)

Since synthetic pesticides are associated with many toxicological problems against untargeted subjects, pesticides from botanical sources become a better option. This study obtained R. communis seed kernel extract (RCSKE) through acidified aqueous extraction. The extract was screened using Infra red (IR) and Ultraviolet (UV) spectroscopy, High-Performance Liquid Chromatography (HPLC) and Cass Chromatography (GC) for bioactive agents. In-vitro effects of RCSKE, chlorpyrifos (CPF) and cypermethrin (CYPER-M) on superoxide dismutase (SOD), Catalase (CAT), acetylcholinesterase (AChE) and Carboxylesterase (CE) activities in Podagrica sjosdteti and Podagrica uniforma were determined spectrophotometrically. The IR and UV of RCSKE majorly depict the presence of aromatic ring, ethylenic bond, carbonyl bond, hydroxyl and carboxylic groups. The HPLC and GC majorly show the presence of ricinoleic acid, ricinine and ricin. The RCSKE, CYPER-M and CPF increased CAT activity in P. sjosdteti , but reduced it in P. uniforma . The RCSKE and CYPER-M significantly reduced SOD, and elevated AChE activities in P. sjosdteti . The IC 50 values of RCSKE, CYPER-M and CPF against CE activity in P. sjosdteti were IC 50 = 2.66 µg/ml, IC 50 = 2.37µg/ml and IC 50 = 2.65 µg/ml), respectively, while that of RCSKE against P. uniforma was IC 50 = 2.49 µg/ml. This study suggests that the extract of Ricinus communis seed kernel contains bioactive substances, capable to inhibit the antioxidant, acetylcholinesterase and carboxylesterase enzymes in Podagrica species flea beetles, comparable to commercial pesticides, Cypermethrin and Chlorpyrifos. Key words: Ricinus communis , Chemical screening, Podagrica sjosdteti , Podagrica uniforma , antioxidant enzymes, hydrolytic enzymes DOI : 10.7176/ALST/75-05 Publication date :June 30 th 2019