CH CH2 Research Articles

Experimental distribution of electron density in crystals of Ph3Sb(O2CCH=CH–CH=CH–CH3)2 complex: the selection of a reference point for the source function in the absence of a bond critical point between atoms

In this article, we report on the results of experimental and theoretical (DFT calculation of an isolated molecule) investigation of electron density in a triphenylantimony disorbate complex (triphenylantimony bis(hexa-2,4-dienoate), Ph3Sb(O2CCH=CH–CH=CH–CH3)2 (1)). A topological analysis of the electron density was carried out in the framework of the quantum theory of atoms in molecules (QTAIM), which allows to study the nature of chemical bonds and the molecular graph in Ph3Sb(O2CCH=CH–CH=CH–CH3)2 complex. The molecular graph is an important tool for determining the interacting atoms. However, the molecular graph of the triphenylantimony disorbate complex did not show the presence of the “expected” intramolecular interactions between the antimony atom and the carbonyl oxygen one. Such a situation can be caused by electron density low curvature between these atoms. It is extremely difficult case, and sometimes it is not possible to find all the “expected” bond paths and critical points (3,−1). Thus, the molecular graph for this class of compounds does not provide a definitive picture of the chemical bonding and should be complemented with other descriptors, such as а source function (SF) and non-covalent interaction (NCI) index. It was found that in some cases using the SF on the NCI isosurface allows to interpret intramolecular interactions in the absence of a bond critical point more correctly. In this article, presence of intramolecular interaction in the absence of a bond critical point between the antimony atom and the carboxylate oxygen one was shown. The carboxylate fragment always acts as a source of the electron density for the Sb…O(carbonyl) interactions, whereas the antimony atom can be both a source and a sink for it.

Two Rare-Earth Molecular Ferroelectrics with High Curie Temperatures, Large Spontaneous Polarization, Switchable Second Harmonic Generation Effects, and Strong Photoluminescence.

Smart multifunctional molecular ferroelectrics bearing high Curie temperatures and diverse excellent physical properties, such as second harmonic generation (SHG) responses, luminescence, and semiconductivity, among others, have significant applications but have seldom been documented. Herein, the rare-earth metals Nd and Pr are introduced into a simple molecular system (nBu4 N)3 [M(NO3 )x (SCN)y ] (nBu4 N= tetrabutyl ammonium, M=rare-earth metal, nBu=CH3 CH2 CH2 CH2 ), and two new multifunctional molecular ferroelectrics are obtained: (nBu4 N)3 [Nd(NO3 )4 (SCN)2 ] (1) and (nBu4 N)3 [Pr(NO3 )4 (SCN)2 ] (2). Their distinct heat and dielectric anomaly dependence on temperature verifies that compounds 1 and 2 experience high-temperature para-ferroelectric phase transitions at 408 and 413 K, respectively. Strikingly, both molecular ferroelectrics possess large spontaneous polarization with Ps values of 9.05 and 8.50 μC cm-2 , respectively, and are further characterized by the appearance of multiple intersecting non-180° domains and polarization switching behavior. In particular, compounds 1 and 2 show good stability with only a small decrease in SHG intensity after switching cycles, suggesting that they have great potential for application in nonlinear optical (NLO) switches. Simultaneously, the rare-earth compounds 1 and 2 present bright yellow-red and bright green fluorescence, respectively, at room temperature.

Photochemical removal of hexavalent chromium and nitrate from ion-exchange brine waste using carbon-centered radicals

Ion-exchange (IX) is a promising technology to remove hexavalent chromium Cr(VI) and nitrate from groundwater; however, its wide application is challenged by a costly disposal of spent brine. This study developed a novel photochemical process utilizing reductive carbon-centered radicals to remove Cr(VI) and nitrate in IX spent brine. In the presence of formate or alcohol additives, photolysis of nitrate in spent brine generated highly reductive carbon-centered radicals including ·CO2−, ·CH2OH, ·CH(OH)CH3, and ·C(OH)(CH3)2. Among them, ·CO2− exhibited the highest efficiency to reduce Cr(VI) to non-toxic Cr(III) solids. Increasing the dosage of formate additive promoted ·CO2− production and accelerated Cr(VI) removal. Decreasing pH enhanced Cr(VI) removal by increasing the yield of ·CO2− and thermodynamic favorability of Cr(VI) reduction while lowering total chromium removal because of the formation of soluble Cr(III) species. High levels of chloride in spent brine scavenged HO·, suppressed ·CO2− production, and inhibited Cr(VI) reduction. With an extended reaction time, nitrate was photochemically converted to gaseous nitrogen species. The denitrification process was favored at acidic pH due to the suppressed formation of nitrite. Findings from this study provides a new photochemical treatment technology for hazardous IX spent brine management.

Effects of cross-linking by MgCl2 as an initiator on the properties of EVOH

Ethylene vinyl alcohol (EVOH) with excellent barrier properties has insufficient thermomechanical properties. The introduction of magnesium chloride (MgCl2) as an initiator in EVOH blends improved its properties by cross-linking. Torque behavior and gel experiment analysis indicated that a cross-linking in EVOH was formed. The cross-linking mechanism was confirmed through 13C nuclear magnetic resonance spectroscopy (13C NMR) and Fourier-transform infrared (FTIR) spectrometry. In 13C NMR spectra, the splitting peaks of CH carbon and CH2 carbon tended to disappear, and the stretching vibration peak of –C=C– was observed in the FTIR spectra. The formation of hydrogen bond between MgCl2 and EVOH destroyed the intramolecular and intermolecular hydrogen bonds of EVOH, which contributed to the dehydration of –OH to form –C=C–, and –C=C– was the basis for a cross-linking reaction. The thermal analysis of blends demonstrated that the melting temperature and crystallization temperature decreased, and the crystallinity gradually disappeared when the MgCl2 content increased. Glass transition temperature significantly increased as the intermolecular force enhanced. Thermogravimetric analysis showed that a cross-linked structure could improve the thermostability of EVOH with an increase in the MgCl2 content. Mechanical test results revealed a remarkable increase in the tensile strength of EVOH as the MgCl2 content increased.

DFT Study on Interstellar PAH Molecules with Aliphatic Side Groups

Abstract Polycyclic aromatic hydrocarbon (PAH) molecules have been long adjudged to contribute to the frequently detected distinct emission features at 3.3, 6.2, 7.7, 8.6, 11.2, and 12.7 μm with weaker and blended features distributed in the 3–20 μm region. The comparatively weaker 3.4 μm emission feature has been attributed to have an aliphatic origin as carrier. PAH with an aliphatic functional group attached to it is one of the proposed potential candidate carriers for the 3.4 μm emission band, however, the assignment of carrier is still enigmatic. In this work, we employ density functional theory calculation on a symmetric and compact PAH molecule; coronene (C24H12) with aliphatic side group to investigate any spectral similarities with observed features at 3–4 μm. The side groups considered in this study are −H (hydrogenated), −CH3 (methyl), −CH2–CH3 (ethyl), and −CH=CH2 (vinyl) functional groups. Considering the possible presence of deuterium (D) in PAHs, we also include D in the aliphatic side group to study the spectral behavior. We present a detailed analysis of the IR spectra of these molecules and discuss possible astrophysical implications.

Neutral heteroleptic nickel complexes incorporating maleonitriledithiolate and bis(diphenylphosphanyl)amine as robust molecular electrocatalysts for hydrogen evolution

Five neutral heteroleptic maleonitriledithiolate nickel complexes [RN(PPh2)2Ni(mnt)] bearing bis(diphenylphosphanyl)amine ligands (where mnt2− = maleonitriledithiolate; R = CH3O(CH2)3 (1), CH3S(CH2)3 (2), (S)-CH3CHPh (3), (CH3)2CH(CH2)2 (4), and p-CH3C6H4 (5)) have been synthesized and fully characterized by elemental analysis, FTIR, NMR (1H, 13C, and 31P) spectroscopy, UV–Vis spectrum, single crystal X-ray diffraction, thermogravimetric analysis, and density functional theory (DFT) calculation. The nickel atom in 1, 2, 4, and 5⋅1.5CH2Cl2 adopts a slightly distorted square-planar coordination environment with two phosphorus atoms of RN(PPh2)2 and two sulfur atoms of mnt2−, respectively, while the nickel atom in 3 exhibits a pseudo square pyramid with HP2S2 chromophore. Furthermore, the electrochemical properties for 1–5 were also investigated by cyclic voltammetry. With the addition of 120 mM trifluoroacetic acid (TFA) to 1–5 in MeCN, the turnover frequency (TOF) values are estimated to be 368.59–585.17 s−1 with the corresponding overpotential (η) values of 0.59–0.73 V. The electrochemical studies indicate that all complexes can be used as low-cost robust molecular eletrocatalysts for the reduction protons to hydrogen in the presence of TFA and a possible ECEC mechanism for electrocatalytic hydrogen evolution has been also proposed.

Fat-water separation by fast metabolite cycling magnetic resonance spectroscopic imaging at 3 T: A method to generate separate quantitative distribution maps of musculoskeletal lipid components.

To provide a rapid, noninvasive fat-water separation technique thatallows producing quantitative maps of particular lipid components. The calf muscles in 5 healthy adolescents (age 12-16 years; body mass index = 20 ± 3 kg/m2 ) were scanned by two different fat fraction measurement methods. A density-weighted concentric-ring trajectory metabolite-cycling MRSI technique was implemented to collect data with a nominal resolution of 0.25 mL within 3 minutes and 16 seconds. For comparative purposes, the standard Dixon technique was performed. The two techniques were compared using structural similarity analysis. Additionally, the difference in the distribution of each lipid over the adolescent calf muscles was assessed based on the MRSI data. The proposed MRSI technique provided individual fat fraction maps for eight musculoskeletal lipid components identified by LCModel analysis (IMC/L [CH3 ], EMCL [CH3 ], IMC/L [CH2 ]n , EMC/L [CH2 ]n , IMC/L [CH2 -CH], EMC/L [CH2 -CH], IMC/L [-CH=CH-], and EMC/L [-CH=CH-]) with mean structural similarity indices of 0.19, 0.04, 0.03, 0.50, 0.45, 0.04, 0.07, and 0.12, respectively, compared with the maps generated by the used Dixon method. Further analysis of voxels with zero structural similarity demonstrated an increased sensitivity of fat fraction lipid maps from the data acquired using this MRSI technique over the standard Dixon technique. The lipid spatial distribution over calf muscles was consistent with previously published findings in adults. This MRSI technique can be a useful tool when individual lipid fat fraction maps are desired within a clinically acceptable time and with a nominal spatial resolution of 0.25 mL.

C-C Bond Formation in Syngas Conversion over Zinc Sites Grafted on ZSM-5 Zeolite.

Despite significant progress achieved in Fischer-Tropsch synthesis (FTS) technology, control of product selectivity remains a challenge in syngas conversion. Herein, we demonstrate that Zn2+ -ion exchanged ZSM-5 zeolite steers syngas conversion selectively to ethane with its selectivity reaching as high as 86 % among hydrocarbons (excluding CO2 ) at 20 % CO conversion. NMR spectroscopy, X-ray absorption spectroscopy, and X-ray fluorescence indicate that this is likely attributed to the highly dispersed Zn sites grafted on ZSM-5. Quasi-in-situ solid-state NMR, obtained by quenching the reaction in liquid N2 , detects C2 species such as acetyl (-COCH3 ) bonding with an oxygen, ethyl (-CH2 CH3 ) bonding with a Zn site, and epoxyethane molecules adsorbing on a Zn site and a Brønsted acid site of the catalyst, respectively. These species could provide insight into C-C bond formation during ethane formation. Interestingly, this selective reaction pathway toward ethane appears to be general because a series of other Zn2+ -ion exchanged aluminosilicate zeolites with different topologies (for example, SSZ-13, MCM-22, and ZSM-12) all give ethane predominantly. By contrast, a physical mixture of ZnO-ZSM-5 favors formation of hydrocarbons beyond C3+ . These results provide an important guide for tuning the product selectivity in syngas conversion.

Reactions of a Bis(vinyltrimethylsilane)nickel(0) N-Heterocyclic carbene complex with organic azides

The reactions of three-coordinate iron(0) and cobalt(0) alkene complexes (NHC)M(η2-CH2CHSiMe3)2 (NHC = N-heterocyclic carbene, M = Fe, Co) with organic azides proved an effective way for the preparation of iron and cobalt terminal imido complexes. The relevant reactions of nickel(0) alkene complex (NHC)Ni(η2-CH2CHSiMe3)2 with organic azides, however, have remained unexplored. Herein, we report the study on the reactions of [(IPr)Ni(η2-CH2CHSiMe3)2] (IPr = 1,3-bis(2′,6′-diisopropylphenyl)imidazole-2-ylidene) with organic azides. The interaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with 2,6-dimesitylphenyl azide (DmpN3) produced the two-coordinate imido complex [(IPr)Ni(NDmp)] (1) in a trace amount with the starting materials being largely remained. The reaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with 2,6-diisopropylphenyl azide (DippN3) gave IPrNNNDipp (2) as the only isolable product. The interaction of [(IPr)Ni(η2-CH2CHSiMe3)2] with PhC(CF3)2N3 produced an azanickelacyclobutane compound [(IPr)Ni(κ-C,N–N(C(CF3)2Ph)CH(SiMe3)CH2)] (3) in high yield. The different products formed in these reactions reflect the influence of the steric and electronic nature of organic azides on reaction outcomes. Further study on the azanickelacyclobutane complex 3 indicated that it can convert into a new azanickelacyclobutane [(IPr)Ni(κ-C,N–N(C(CF3)2Ph)CH2CHSiMe3)] (4). A nickel(II) amido alkyl complex [(IPr)Ni(NHC(CF3)2Ph)(CH2CHNC(CF3)2Ph)] (5) was also isolated from the decomposition reaction of 3.

Visible-light-driven integrated organic synthesis and hydrogen evolution over 1D/2D CdS-Ti3C2Tx MXene composites

Exploiting solar energy to photocatalyze integrated selective conversion of bioethanol into fine chemicals and hydrogen (H2) is a promising avenue in response to current energy and environmental crises. Herein, we have reported the mild synthesis of a binary heterostructure of CdS-Ti3C2Tx MXene (CdS-MX) combining one-dimensional (1D) CdS nanowires (NWs) with two-dimensional (2D) MXene structure, and its application in photocatalytic coupling redox reaction of H2 evolution and selective conversion of bioethanol into 1,1-diethoxyethane (DEE) under acidic conditions. The results reveal that the synergistic effect of the intimate interfacial contact and matched energy level alignment between electrically conductive 2D MXene and semiconductor 1D CdS NWs benefits the separation and migration of charge carriers. Furthermore, CH(OH)CH3 has been proven to be the pivotal radical intermediate during photoredox process. This work is anticipated to stimulate further interest on rational construction of MXene-semiconductor based composites toward photoredox coupling organic synthesis and H2 evolution in a sustainable manner.

Nine supramolecular adducts of 4-dimethylaminopyridine and organic acids constructed by classical H-Bonds and some noncovalent interactions

Cocrystallization of the commonly available 4-dimethylaminopyridine with a sets of acidic coformers gave a total of nine anhydrous and hydrous multicomponent adducts (4-dimethylaminopyridine): (2,4-dinitrobenzenesulfonic acid) [(HDMAP) · (dnbsa), dnbsa = 2,4-dinitrobenzenesulfonate] (1), (4-dimethylaminopyridine): (2-chloro-4-nitrophenol) [(HDMAP) · (cnpa), cnpa = 2-chloro-4-nitrophenolate] (2), (4-dimethylaminopyridine): (2,4,6-tribromophenol)2 [(HDMAP) · (tbp) · (Htbp), tbp = 2,4,6-tribromophenolate] (3), (4-dimethylaminopyridine): (4-chlorocinnamic acid)2: (H2O)3 [(HDMAP+)2 · (ccina−)2 · (H2O)3, ccina− = 4-chlorocinnamate] (4), (4-dimethylaminopyridine): (3,4,5-trimethoxycinnamic acid) [(HDMAP+) · (tmcina−), tmcina− = 3,4,5-trimethoxycinnamate] (5), (4-dimethylaminopyridine): (3,4-dichlorobenzoic acid): (H2O) [(HDMAP+) · (dcbza−) · (H2O), dcbza− = 3,4-dichlorobenzoate] (6), (4-dimethylaminopyridine): (2,5-dihydroxybenzoic acid) [(HDMAP) · (dhba), dhba = 2,5-dihydroxybenzoate] (7), (4-dimethylaminopyridine) (5-hydroxyisophthalic acid): [(HDMAP) · (Hipta), Hipta = hydrogen 5-hydroxyisophthalate] (8) and (4-dimethylaminopyridine): (tetrachlorophthalic acid) [(HDMAP) · (Htcpta), Htcpta = hydrogen tetrachlorophthalate] (9). The nine adducts have been characterized by XRD, IR and EA and the melting points of all adducts were also reported. Their structural and supramolecular facets are fully analyzed. The result reveals that all the studied crystals are organic salts with only the aryl N in DMAP protonated and the crystal packing is mediated via the strong N–H⋯O, N–H⋯S, N–H⋯Br, O–H⋯O and O–H⋯Br H-bonds from DMAP and the acidic bodies. Further analysis of the crystal piling of the salts told that a different series of additional CH–O/CH3–O, CH-π/CH3-π, CH3–CH, CH3–Cl, CH–Cl, CH3–Br, CH3–C, CH–C, CH–Br, C–C, O–O, O–C, O–N, O-π and π-π contacts helped the stabilization and expansion of the whole high-dimensional (1D-3D) packing. For the subtle balance of the various nonbonding associations these structures exhibited homo or hetero supramolecular synthons or both.

Pair interaction energy decomposition analysis (PIEDA) and experimental approaches for investigating water interactions with hydrophilic and hydrophobic membranes

The origins of low and high interactions of polar groups with water molecules are still unknown and need to be further examined for effective future membrane synthesis and modification. The primary aim of this research study is to provide a comprehensive overview of the interactions at the molecular level occurring between water molecules and the fragments of hydrophobic and hydrophilic membranes based on pair interaction energy decomposition analysis (PIEDA) as part of the fragment molecular orbital (FMO) method’s framework. This direction is critical, since a research study of the reasons for water and membrane interactions can help design groundbreaking membranes with superior hydrophilicity characteristics. To accomplish this, the computational studies, the Polyvinylidene fluoride (PVDF [H(–CH2–CF2–)4CH3]) and Polyacrylonitrile (PAN [(H(–CH2–CH(CN)–)4CH3]) membranes were considered as models for hydrophobic and hydrophilic membranes, respectively. Density-functional theory (DFT), based on B3LYP functional and split-valance 6-311+G (d,p) basis sets, was used in order to optimize the geometry of PAN, PVDF, and their complexes with different numbers of water molecules. Furthermore, fragment molecular orbit (FMO) and the Pair Interaction Energy Decomposition Analysis (PIEDA) were carefully interrogated. These types of analyses included the inter fragment interaction energy (IFIE), like the electrostatic (ES), exchange repulsion (EX), charge-transfer and mixing term (CT + mix) energies. Furthermore, the hydrophilicity and hydrophobicity of the origins of membrane function groups were experimentally evaluated through Fourier-transform infrared spectroscopy (FTIR- ATR), 13C cross polarization magic angle spinning (13C CP MAS) Solid State Nuclear magnetic resonance SSNMR, and Fourier transform Raman (FT-Raman) spectroscopies. Confocal microscopic approach was used to interrogate water transport and the interactions between fluorescence particles and membrane layers. Furthermore, the Infrared (IR) spectroscopy was performed to investigate interaction between water molecules and PVDF and PAN. The theoretical results had a good agreement with experimental result.

An Acetal Acylation Methodology for Producing Diversity of Trihalomethyl- 1,3‑dielectrophiles and 1,2-Azole Derivatives

A series of functionalized 1,1,1-trihalo-4-methoxy-3-alken-2-ones [CX3C(O)CR1=CROMe, where X = F or Cl; R = n-heptyl, n-octyl, n-nonyl, n-decyl, n-undecyl, n-tridecyl, (CH2)2CH=C(Me)2, (CH2)2Ph, (CH2)2-(4-HOC6H4), (CH2)2-(4-MeOC6H4), (CH2)2CO2Me, (CH2)3CO2Me, CH(SMe)CH3, CH2(2-MeOC6H4), and R1 = H, and R = H and R1 = n-decyl] were synthesized from respective alkyl methyl ketones or aldehyde via acetal acylation using trifluoroacetic anhydride and trichloroacetyl chloride. 1,1,1-Trihalo-4-methoxy-3-alken-2-ones with acid-compatible substituents were easily hydrolyzed to respective trihalomethyl-1,3-diketones. The 1,1,1-trihalo-4-methoxy-3-alken-2-ones and/or respective trihalomethyl-1,3-diketones were reacted regiospecifically with hydroxylamine hydrochloride, leading to isoxazole derivatives, and with hydrazines, leading to respective 1H-pyrazole derivatives. The structures of all compounds were assigned based on nuclear magnetic resonance (NMR) and mass spectrometric data. This method represents an efficient pathway for the regioselective trihaloacetylation of asymmetrically substituted alkyl methyl ketones and highly self-condensing aldehydes. Moreover, this approach allows the introduction of biologically recognizable moieties, such as those from levulinic acid, sulcatone (prenyl), benzylacetone, anisylacetone, and raspberry ketone, as synthetic molecular targets.

Designing new donor materials based on functionalized DCCnT with different electron‐donating groups: A density functional theory (DFT) and time dependent density functional theory (TDDFT)‐based study

AbstractFinding a promising donor/acceptor material of organic solar cells is one of the most important ways to improve their power conversion efficiency. Extensive studies have focused on designing and synthesizing new and suitable materials. Small organic molecule materials, different from polymers, have many merits, such as easy synthesis and modification, less by‐products, and crystallinity. In the present work, we theoretically design a series of new donor materials based on 1‐(1,1‐dicyanomethylene)‐cyclohex‐2‐ene‐substituted oligothiophenes, that is, DCCnT (n = 1‐4) series. Furthermore, we model and predict photoelectric properties of functionalized DCCnT with different electron‐donating groups (─CH3/─CHCH2/─OCH3/─NH2/─OH). The calculated results, based on density functional theory and time‐dependent functional theory, show that DCCnT‐X (X = OH, NH2, and OCH3) series show odd‐even effect of dipole moments when n varies from 1 to 4, whereas DCCnT‐CH3 and DCCnT‐CHCH2 do not. Finally, we find that DCC3T‐X (X = OH, OCH3, and NH2) may be better candidates of donor materials because of their larger dipole moments, stronger electron donating ability, and smaller exciton binding energy with respect to prototype DCCnT molecules.

Universal Group 14 Free Radical Photoinitiators for Vinylidene Fluoride, Styrene, Methyl Methacrylate, Vinyl Acetate, and Butadiene

Group 14 (Mt = Sn, Ge, Pb) R3MtX, R4Mt, and R6Mt2 complexes (R = alkyl, aryl; X = H, halide, etc.) are introduced as novel, universal, visible and black light bulb (BLB)/UV photoinitiators for free radical photopolymerization of alkenes, including vinylidene fluoride (VDF), vinyl acetate, methyl methacrylate, styrene, and butadiene. A comprehensive solvent, ligand and metal comparison for VDF indicates progressively faster BLB photopolymerizations in acetonitrile (ACN) ∼ dimethylacetamide (DMAc) < dimethyl sulfoxide (DMSO) < butanone < propylene carbonate < acetic anhydride ∼ cyclohexanone < dimethyl carbonate and especially in the photosensitizing acetone, where Me2SnI2 ∼ Ph3SnI ∼ Bu3Sn–N3 ∼ Bu3Sn–CH2–CH═CH2 ≪ Bu3Sn–S–SnBu3 < Ph4Ge < Ph6Pb2 < Bu3Sn–I < Bu4Sn < Ph6Sn2 < Bu3Sn–Br < Ph6Ge2 < Oct4Sn < Bu4Ge < Bu3Sn–Cl < Ph4Pb < Bu3Sn–H ≪ Bu6Sn2 ≪ Me6Sn2 and where Mn is controlled by solvent chain transfer. Photoinitiation results from a combination of R3Mt·, R·, and solvent (S·, e.g., CH3–CO–CH2·) radicals, ...

Seven supramolecular adducts of 4-dimethylaminopyridine and carboxylic acids constructed by classical H-Bonds and some noncovalent interactions

Abstract Cocrystallization of the commonly available pyridine derivative, 4-dimethylaminopyridine, with a series of carboxylic acids gave a total of seven anhydrous and hydrous multicomponent adducts (4-dimethylaminopyridine): (4-methoxybenzoic acid) [(HDMAP) · (mba) · (Hmba), mba = 4-methoxybenzoate] (1), (4-dimethylaminopyridine): (4-(aminosulphonyl)benzoic acid) [(HDMAP) · (aspba), aspba = 4-(aminosulphonyl)benzoate] (2), (4-dimethylaminopyridine): (3-methylsalicylic acid)2 [(HDMAP) · (msal) · (Hmsal), msal = 3-methylsalicylate] (3), (4-dimethylaminopyridine): (3,5,6-trichlorosalicylic acid) [(HDMAP+) · (tcsal−), tcsal− = 3,5,6-trichlorosalicylate] (4), (4-dimethylaminopyridine): (2-pyrazinecarboxylic acid): 4H2O [(HDMAP+) · (pyza−) · 4H2O, pyza− = 2-pyrazine carboxylate] (5), (4-dimethylaminopyridine): (2,2′-biphenyldicarboxylic acid) [(HDMAP+) · (Hbpda−), Hbpda = hydrogen 2,2′-biphenyldicarboxylate] (6) and (4-dimethylaminopyridine)2: (dibenzoyltartaric acid) [(HDMAP) · (Hdbta) · CH3OH · H2O, Hdbta = hydrogen dibenzoyltartarate] (7). The seven adducts have been characterized by XRD technique, IR and elemental analysis, and the melting points of all adducts were also reported. Their structural and supramolecular aspects are fully analyzed. The result reveals that all the investigated crystals are organic salts with only the aryl N in DMAP protonated and the crystal packing is interpreted in terms of the strong N–H⋯O, N–H⋯N, O–H⋯N and O–H⋯O H-bond from DMAP and the acidic groups. Further analysis of the crystal packing of the salts indicated that a different family of additional CH–N, CH–O/CH3–O, CH-π/CH3-π, CH3–CH, CH3–Cl, C-π, O-π, Cl–Cl and π-π associations contribute to the stabilization and expansion of the total high-dimensional (1D-3D) structures. For the delicate balance of the various weak nonbonding interactions these structures adopted homo or hetero supramolecular synthons or both.

Comparison of thermal, thermomechanical, and rheological properties of blends of divinylbenzene‐based hyperbranched and linear functionalized polymers

ABSTRACTA range of polymer blends were prepared via a solvent‐based film casting process using highly/hyperbranched (HB) polydivinylbenzenes (PDVB) polymers of two different molecular weights, linear functionalized (LF), hydrogenated hyperbranched (H‐HB2) PDVB, and linear polystyrene (LP). The thermal, thermomechanical, and rheological properties of the pure polymers and blends were then investigated and the results related to the concentration of “branched” polymer in the blend and the level of branching/polymer end groups present in the “branched” polymers used. Differential scanning calorimetry (DSC) analysis revealed an increase of the glass transition temperature (Tg) for the blends containing the nonhydrogenated HBs (~108 °C compared to ~102 °C for LP), which was attributed to crosslinking via the unsaturated reactive chain end/pendant groups in the HB (CHCH2). In contrast at the blends, containing the hydrogenated polymers H‐HB2, exhibited the same Tg as LP (~102°C) due to absence of crosslinking from the (H‐HB2) polymer. As the unsaturated HBs were found to be thermally curable, curing temperature rheology measurements were carried out employing a temperature ramp. No specific Tgel (the temperature at which HB gets crosslinked) was identified for LP‐HB1 and LP‐HB2 blends, which might be suggested to be due to the fact that both chain entanglement from linear polystyrene. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48547.

Iron Oxide as a Promoter for Toluene Catalytic Oxidation Over Fe–Mn/γ-Al2O3 Catalysts

Fe–Mn/γ-Al2O3 catalysts that prepared by the wet-impregnation method were used to degrade toluene, a VOCs model compound. The results indicated that the 10Fe–15Mn/γ-Al2O3 exhibited 95% of toluene conversion as well as 95% of CO2 yield at 300 °C. The Fe–Mn/γ-Al2O3 showed a better toluene oxidation activity with respect to the Fe/γ-Al2O3 and Mn/γ-Al2O3. The introduction of Fe into the Mn/γ-Al2O3 resulted in higher surface area, higher Mn3+/(Mn3+ + Mn4+) ratio, lower reduction temperature, and homogenous distribution of Mn. Meanwhile, the co-exist of the Fe3+ and Mn3+ over the 10Fe–15Mn/γ-Al2O3 also favored for the oxygen transfer, which may enhance the catalytic oxidation performance. The initial toluene was adsorbed on surface of the catalysts and formed benzoyl oxide (C6H5–CH2–O), and then the benzoyl oxide (C6H5–CH2–O) was oxidized to benzaldehyde. Furthermore, the benzaldehyde was further oxidized to form benzoic acid that could be converted to CO2 and H2O.

Thermal behavior of crosslinking polystyrene resin to carbon material by one-step carbonization

Crosslinking polystyrene (CPS), which is an inexpensive porous resin synthesized by waste polystyrene and CCl4, can be precursor for carbon material. Carbonization with KOH or steam activation was usually needed for the carbonization, but that without any activation was rarely reported. By the carbonization (room temperature to 900 °C; heating rate of 3 °C/min; N2 atmosphere), the carbon prepared had no pores. Interestingly, the carbonization modified by five temperature platforms (150 °C, 200 °C, 300 °C, 400 °C and 500 °C) before 900 °C can produce the porous carbon with high surface area (SBET = 849 m2/g) and rich micropores (Vmic = 0.306 cm3/g). The thermal behavior of the CPS was studied under different carbonization conditions. The temperature platforms that made the heating milder was found to be crucial for the porous structure. They promoted the hydrolysis of Ph2CCl2 to Ph2C=O stabilizing the skeleton and slowed down the escape of the pore-creating substances, i.e., Ph2C=O, PhCOOH and –[CH–CH2]n–. Thereby, the carbonization with the temperature platforms not only kept the pores but also constructed the new pores. Moreover, the porous carbon prepared had the rich micropores from 0.6 to 0.8 nm and from 1.0 to 1.2 nm, showing a high S-capacity (34.2 mg S/g) for the adsorption of dibenzothiophene from oil.

Formation and hydrolysis of gas-phase [UO2 (R)]+ : R═CH3 , CH2 CH3 , CH═CH2 , and C6 H5.

The goals of the present study were (a) to create positively charged organo-uranyl complexes with general formula [UO2 (R)]+ (eg, R═CH3 and CH2 CH3 ) by decarboxylation of [UO2 (O2 C─R)]+ precursors and (b) to identify the pathways by which the complexes, if formed, dissociate by collisional activation or otherwise react when exposed to gas-phase H2 O. Collision-induced dissociation (CID) of both [UO2 (O2 C─CH3 )]+ and [UO2 (O2 C─CH2 CH3 )]+ causes H+ transfer and elimination of a ketene to leave [UO2 (OH)]+ . However, CID of the alkoxides [UO2 (OCH2 CH3 )]+ and [UO2 (OCH2 CH2 CH3 )]+ produced [UO2 (CH3 )]+ and [UO2 (CH2 CH3 )]+ , respectively. Isolation of [UO2 (CH3 )]+ and [UO2 (CH2 CH3 )]+ for reaction with H2 O caused formation of [UO2 (H2 O)]+ by elimination of ·CH3 and ·CH2 CH3 : Hydrolysis was not observed. CID of the acrylate and benzoate versions of the complexes, [UO2 (O2 C─CH═CH2 )]+ and [UO2 (O2 C─C6 H5 )]+ , caused decarboxylation to leave [UO2 (CH═CH2 )]+ and [UO2 (C6 H5 )]+ , respectively. These organometallic species do react with H2 O to produce [UO2 (OH)]+ , and loss of the respective radicals to leave [UO2 (H2 O)]+ was not detected. Density functional theory calculations suggest that formation of [UO2 (OH)]+ , rather than the hydrated UV O2 + , cation is energetically favored regardless of the precursor ion. However, for the [UO2 (CH3 )]+ and [UO2 (CH2 CH3 )]+ precursors, the transition state energy for proton transfer to generate [UO2 (OH)]+ and the associated neutral alkanes is higher than the path involving direct elimination of the organic neutral to form [UO2 (H2 O)]+ . The situation is reversed for the [UO2 (CH═CH2 )]+ and [UO2 (C6 H5 )]+ precursors: The transition state for proton transfer is lower than the energy required for creation of [UO2 (H2 O)]+ by elimination of CH═CH2 or C6 H5 radical.