Real-space observation on standing configurations of phenylacetylene on Cu(111) by scanning probe microscopy

The adsorption configurations of molecules adsorbed on substrates can significantly affect their physical and chemical properties. A standing configuration can be difficult to determine by traditional techniques, such as scanning tunneling microscopy(STM) due to the superposition of electronic states. In this paper, we report the real-space observation of the standing adsorption configuration of phenylacetylene on Cu(111) by non-contact atomic force microscopy(nc-AFM).Deposition of phenylacetylene at 25 K shows featureless bright spots in STM images. Using nc-AFM, the line features representing the C–H and C–C bonds in benzene rings are evident, which implies a standing adsorption configuration. Further density functional theory(DFT) calculations reveal multiple optimized adsorption configurations with phenylacetylene breaking its acetylenic bond and forming C–Cu bond(s) with the underlying copper atoms, and hence stand on the substrate.By comparing the nc-AFM simulations with the experimental observation, we identify the standing adsorption configuration of phenylacetylene on Cu(111). Our work demonstrates an application of combining nc-AFM measurements and DFT calculations to the study of standing molecules on substrates, which enriches our knowledge of the adsorption behaviors of small molecules on solid surfaces at low temperatures.

Electronic transport properties of phenylacetylene molecular junctions

Electronic transport properties of a kind of phenylacetylene compound-- （4-mercaptophenyl）-phenylacetylene are calculated by the first-principles method in the framework of density functional theory and the nonequilibrium Green＇s function formalism. The molecular junction shows an obvious rectifying behaviour at a bias voltage larger than 1.0 V. The rectification effect is attributed to the asymmetry of the interface contacts. Moreover, at a bias voltage larger than 2.0 V, which is not referred to in a relevant experiment [Fang L, Park J Y, Ma H, Jen A K Y and Salmeron M 2007 Langmuir 23 11522], we find a negative differential resistance phenomenon. The negative differential resistance effect may originate from the change of the delocalization degree of the molecular orbitals induced by the bias.

Selective Hydrogenation of Phenylacetylene by Carbon Monoxide and Water

Catalytic selective hydrogenation of alkynes to the corresponding alkenes is an important process in industrial production.Modulating the selective hydrogenation of alkynes to the alkenes requires ingenuity since alkenes can easily be converted into the corresponding alkanes under reductive conditions.Applying different reductive reagents to prevent the direct usage of H_(2)can avoid difficulties in hydrogen storage and transportation.Herein,we demonstrate a tandem process to hydrogenate phenylacetylene by CO and H_(2)Oviathecouplingof thelow-temperaturewater-gas shift reaction and selective hydrogenation of phenylacetylene utilizing theα-MoC catalyst.The reductive reagent,CO,not only produces H_(2)from H_(2)O to drive the reaction forward,but it also regulates the selectivity of styrene by preventing further hydrogenation.

Construction of trace silver modified core@shell structured Pt-Ni nanoframe@CeO2 for semihydrogenation of phenylacetylene

The Pt-Ni nanoframe catalysts have attracted great interest owing to their unique electronic structure and excellent catalytic performance. However, the stability of the tenu ous edges of nano frame-structures is dissatisfactory and their un iversal applicati ons in catalytic market beyond electrocatalytic reactions are yet to be tapped and explored. Herein, we developed a new core@ shell structured Pt-Ni nanoframe@CeO2 (Pt-Ni NF@CeO2) composite via etching the Ni from inhomogeneous Pt-Ni rhombic dodecahedra (Pt-Ni RD) by cerium(lll) acetate hydrate (Ce(OAc)3). In this path, Pt-Ni RD was used as self-sacrificial 怕mplate, while the Ce(OAc)3 serves as the provider of the Ce3* source and OH' for the formation of CeO2 shell, etchant of Pt-Ni RD, and the surface modification agent. By this way, the etching of Pt-Ni RD and the formation of the CeO2 shell are simultaneously proceeded to form the final Pt-Ni NF@CeO2 in one step. The obtained Pt-Ni NF@CeO2 exhibits strong in terfacial charge tran sfer interactio n betwee n Pt-Ni NF core and CeO2 shell eve n without reductio n treatment, leading to enhan ced catalytic activity in the hydrogenation of phenylacetylene. After introduction of trace silver, the Pt-Ni-Ag4.9 NF@CeO2 achieves remarkable catalytic performa nee for the selective con versi on of phe ny lacetyle ne to styrene: high con version (100%), styre ne selectivity (86.5%), and good stability. It reveals that enc apsulatio n n oble metal nano frames into metal oxide to form core @ shell structured hybrids will in deed enhance their stability and catalytic properties. Particularly, this work expends the application of noble metal nanoframes materials to hydrogenation reacti ons.

Mesoporous silica stabilized MOF nanoreactor for highly selective semi-hydrogenation of phenylacetylene via synergistic effect of Pd and Ru single site

Selective semi-hydrogenation of phenylacetylene to styrene is a crucial step in the polystyrene industry.Although Pd-based catalysts are widely used in this reaction due to their excellent hydrogenation activity,the selectivity for styrene remains a great challenge.Herein,we designed a mesoporous silica stabilized Pd-Ru@ZIF-8(MS Pd-Ru@ZIF-8)nanoreactor with novel Pd and Ru single site synergistic catalytical system for semi-hydrogenation of phenylacetylene.The nanoreactor exhibited a superior performance,achieving 98%conversion of phenylacetylene and 96%selectivity to styrene.Turnover frequency(TOF)of nanoreactor was up to as high as 2,188 h^(−1),which was 25 times and 5 times more than the single metal species catalysts,mesoporous silica stabilized Pd@ZIF-8 nanoreactor(MS Pd@ZIF-8),and mesoporous silica stabilized Ru@ZIF-8 nanoreactor(MS Ru@ZIF-8).This catalytic activity was attributed to the synergistic effect of Pd and Ru single site anchored strongly into the framework of ZIF-8,which reduced the desorption energy of styrene and increased the hydrogenation energy barrier of styrene.Importantly,since the ordered mesoporous silica was introduced into the nanoreactor shell to stabilize ZIF-8,MS Pd-Ru@ZIF-8 showed excellent reusability and stability.After the five cycles,the catalytical activity and selectivity still remained.This work provides insights for a synergistic catalytic system based on single-site active sites for selective hydrogenation reactions.

Novel Photocycloaddition Reactions of N-Methyl-2, 3-naphthalenedicarboximide with Phenylacetylene

UV irradiation of N-methyl-2,3-naphthalenedicarboximide with phenylacetylene in benzene solution afforded a novel hexacyclic adduct 2 confirmed unambiguously by single crystal X-ray diffraction.

Gold-catalyzed Intermolecular Oxidation of Phenylacetylene and Allylic Sulfides： an Efficient and Practical Synthesis of α-Phenylthio Ketone

An efficient and practical synthesis of α-phenylthio ketone through gold-catalyzed intennolecular oxidation of phenylacetylene and substituted aryl（benzyl） allylic sulfides was developed. The reaction scope is fairly good with substituted aryl（beazyl） allylic sulfides, tolerating various functional groups, and the reaction affords the yields of 63%-85%.

SYNTHESIS OF THE COPOLYMERS OF p-DIETHYNYLBENZENE WITH OTHER ACETYLENIC DERIVATIVE S INITIATED BY (Ph_3P)_2 PdCl_2

The copolymerization of p-diethynylbenzene (PDEB) with phenylacetylene (PhA), 4, 4'-diethynylbiphenyl (DEBP)or m-diethynylbenzene (MDEB) are studied by varying mole ratios of monomers. When the mole ratios of PDEB/PhA are less or equal to 1/5, the copolymers are soluble and fusible, but the other copolymers are insoluble and infusible. The results show that the good solvent of cross-linked copolymers is benzene and their solubility parameter is 9.15 cal^(0.5).cm(-1.5). And their swellability (θ_p), Huggins parameter (χ), density (d_4^(25)) and the average molecular weights between crosslinks (c) are measured. It is found that θp and c of copolymers are greater but d_4^(25) is less than that of respective homopolymers. IR spectra show that the copolymers have transoid configuration and small number of unreacted ethynyl groups exist in the copolymers. The mechanism about the polymerization or acetylenic derivatives initiated by (Ph_3P)_2PdCl_2 is discussed.

INFLUENCE OF BACKBONE RIGIDITY ON THE LIQUID CRYSTALLINITY OF MESOGEN-CONTAINING POLYACETYLENES

Two acetylene polymers containing cyanobiphenyl-based mesogens, poly{10-[((4'-cyano-4-biphenylyl)oxy)carbonyl]-1-decyne} (PA8CN), which has a relatively flexible polyalkyne backbone, and poly {[4-(((12-((4'-cyano-4-biphenylyl)oxy)dodecyl)oxy) carbonyl) phenyl]-acetylene} (PB12CN), which has a fairly rigid poly(phenylacetylene) backbone, were synthesized using respectively WCl6 and [Rh(nbd)Cl](2) as the catalysts. PA8CN exhibits enantiotropic interdigitated smectic A phase (S-Ad) over a temperature range as wide as ca. 100 degrees C, whereas PB12CN is non-mesomorphic, demonstrating that the backbone rigidity plays an important role in determining the liquid crystallinity of the polyacetylenes.

Synthesis and Crystal Structure of[（2 , 4-Me2C5H5）2NdC ＝CC6H5]2

he reaction of (2, 4-C_7H_11)_3Nd with HC=CC_6H_5 in toluene leads to [(2, 4-C_7H_11)_2NdC = CC_6H_5]_2 , which crystallizes in the space group P_cab with unit cell pa-rameters a=1 . 0489 (11), b=1.8033 (12), c=2. 1064 (15)nm and Z=4 , least-squares refinement based on 2323 observed reflections converged to a final R valueof 0. 08. The molecular structure shows that the complex is a dimer, in which two(2,4-C_7H_11)_2Nd units are connected by asymmetrical alkynide bridges with indepen-dent Nd-C(alkynide) bond lengths of 0. 2552(25)and 0. 2560(24)nm, Nd-C=C angles of 124. 1(17)° and 134. 2(17)°.

Catalytic Hydration of Aromatic Alkynes to Ketones over H-MFI Zeolites

The hydration of alkyne represents the most straightforward and simplest route toward the synthesis of ketone. Herein, Brønsted acidic zeolites are explored as potential catalysts for the liquid-phase phenylacetylene hydration. The topology structure and Si/Al ratio are disclosed to be key factors controlling the catalytic activity of zeolites. Typically, H-MFI zeolite with a Si/Al molar ratio of 13 exhibits the highest catalytic activity, with turnover frequency of 6.0 h-1 at 363 K. Besides, H-MFI zeolite shows good catalytic stability and recyclability in the reaction of phenylacetylene hydration, and the substrate scope can be simply extended to other soluble aromatic alkynes. The reaction mechanism of phenylacetylene hydration is investigated by means of kinetic and spectroscopic analyses. The Markovnikov electrophilic addition of phenylacetylene by hydrated protons is established as the rate-determining step, followed by deprotonation and enol isomerization to derive acetophenone product.