Fragmentation of some 4<Emphasis Type="Italic">H</Emphasis>-pyran-4-one and pyridin-4-one derivatives under electron impact

Fragmentation of 13 compounds of the 4H-pyran-4-one and pyridin-4-one series under electron impact involves formation of rearrangement ions stabilized by multiple bonds and oxygen atoms (mostly [RC≡O]⁺ and RCH=OR′]⁺), as well of neutral molecules with low enthalpies of formation (CO, H₂O, CH₂O, CO₂, CH₂=C=O, C₃O₂, and RCOOH; R = H, Me, HC≡C, HOC≡C).     

Transition‐Metal Complexes Based on the 1,3,5‐Triethynyl Benzene Linking Unit

The synthesis of a unique series of heteromultinuclear transition metal compounds is reported. Complexes 1‐I‐3‐Br‐5‐(FcC≡C)‐C₆H₃ ( 4 ), 1‐Br‐3‐(bpy‐C≡C)‐5‐(FcC≡C)‐C₆H₃ ( 6 ), 1,3‐(bpy‐C≡C)₂‐5‐(FcC≡C)‐C₆H₃ ( 7 ), 1‐(XC≡C)‐3‐(bpy‐C≡C)‐5‐(FcC≡C)‐C₆H₃ ( 8 , X = SiMe₃; 9 , X = H), 1‐(HC≡C)‐3‐[(CO)₃ClRe(bpy‐C≡C)]‐5‐(FcC≡C)‐C₆H₃ ( 11 ), 1‐[(Ph₃P)AuC≡C]‐3‐[(CO)₃ClRe(bpy‐C≡C)]‐5‐(FcC≡C)‐C₆H₃ ( 13 ), 1‐[(Ph₃P)AuC≡C]‐3‐(bpy‐C≡C)‐5‐(FcC≡C)‐C₆H₃ ( 14 ), [1‐[(Ph₃PAuC≡C]‐3‐[{[Ti](C≡CSiMe₃)₂}Cu(bpy‐C≡C)]‐5‐(FcC≡C)‐C₆H₃]PF₆ ( 16 ), and [1,3‐[(tBu₂bpy)₂Ru(bpy‐C≡C)]₂‐5‐(FcC≡C)‐C₆H₃](PF₆)₄ ( 18 ) (Fc = (η⁵‐C₅H₄)(η⁵‐C₅H₅)Fe, bpy = 2,2′‐bipyridiyl‐5‐yl, [Ti] = (η⁵‐C₅H₄SiMe₃)₂Ti) were prepared by using consecutive synthesis methodologies including metathesis, desilylation, dehydrohalogenation, and carbon–carbon cross‐coupling reactions. In these complexes the corresponding metal atoms are connected by carbon‐rich bridging units comprising 1,3‐diethynyl‐, 1,3,5‐triethynylbenzene and bipyridyl units. They were characterized by elemental analysis, IR and NMR spectroscopy, and partly by ESI‐TOF mass spectrometry., The structures of 4 and 11 in the solid state are reported. Both molecules are characterized by the central benzene core bridging the individual transition metal complex fragments. The corresponding acetylide entities are, as typical, found in a linear arrangement with representative M–C, C–C_C≡C and C≡C bond lengths.     

Molecular structure and dynamics in monolayers of long chain alkanes and alkyl-derivatives

Long chain alkanes (C₃₄H₇₀ and C₅₀H₁₀₂), a fatty acid (C₁₇H₃₅COOH) and an alkyl-substituted triiodobenzoate (I₃H₂C₆COOC₁₈H₃₇) have been adsorbed at the interface between organic solutions and the basal plane of graphite. In-situ scanning tunneling microscopy (STM) has been employed to investigate their structure and dynamics on the scale of 10 pm and 1 ms or longer. All adsorbates form two-dimensional polycrystals. The molecules tend to organize in lamellae with the extended alkyl chains oriented parallel to a lattice axis within the basal plane of graphite. The n-alkane chains pack in a lattice commensurate with the graphite lattice and the carbon skeleton planes approximately perpendicular to the substrate. Due to the additional space required by a carboxyl end group the alkyl lattice in the fatty acid is incommensurate with the substrate and the carbon skeleton planes lie approximately parallel to the surface. In the triiodobenzoate the headgroup takes the space of about two alkyl chains resulting in an interdigitated packing.     

Structural Studies of Some Compounds Containing C2 Fragments Attached to Various Metal‐Ligand End‐Groups

The preparation, characterisation and single‐crystal XRD molecular structure determinations of four complexes containing –CC–ML_n end‐groups, namely Ru{C≡CFc′(I)}(dppe)Cp ( 1 ), the vinylidene [Os(=C=CH₂)(PPh₃)₂Cp]PF₆ ( 2 ), trans‐Pt(C≡CC₆H₄‐4‐C≡CPh){C≡CC₆H₄‐4‐C₂Ph[Co₂(μ‐dppm)(CO)₄]}(PPh₃)₂ ( 3 ), and C₆H₄{μ₃‐C₂[AuRu₃(CO)₉(PPh₃)]}₂‐1,4 ( 4 ) are reported. In these compounds a range of –CC– environments is found, extending from the σ‐bonded alkynyl group in 1 to examples where the C₂ unit interacts with either a proton (in vinylidene 2 ), by bridging a dicobalt carbonyl moiety (in 3 ) or the AuRu₃ cluster in 4 . Changes in geometry are rationalised by considering the various bonding modes.     

Non-muffin-tin MS Xα total energies for H2, C2, N2 and CO

NMT (non-muffin-tin) MS Xα calculations for the ground state potential curves are reported for the molecules H₂, C₂, N₂, and CO. These calculations include corrections linear and second order in the NMT charge density and show great improvement over the MT (muffin-tin) curves. With these corrections, somewhat better agreement with experiment is also found. A comparison is made between tne Xα and the local spin density (LSD approximations for the H₂ and CO molecules.     

A DFT study of Lp···π/halogen bond competition in complexes of perhalogenated alkenes with oxygen/nitrogen containing simple molecules

The possible noncovalent lone pair‐π/halogen bond (lp···π/HaB) complexes of perhalogenated unsaturated C₂Cl_nF_4?n (n = 0–4) molecules with four simple molecules containing oxygen or nitrogen as electron donor, formaldehyde (H₂CO), dimethyl ether (DME), NH₃, and trimethylamine (TMA), have been systematically examined at the M062X/aug‐cc‐pVTZ level. Natural bond orbital (NBO) analysis at the same level is used for understanding the electron density distributions of these complexes. The progressive introduction of Cl atom on C₂Cl_nF_4?n influences more on the lp···π complexes over the corresponding HaB ones. Within the scope of this study, gem‐C₂Cl₂F₂ is the best partner molecule for lp···π interaction with the simple molecules, coupled with the greatest interaction energy (IE) and second‐order orbital interaction [E(2) value], whereas C₂F₄ is the poorest one. The C₂Cl₃F·H₂CO and C₂Cl₄·H₂CO complexes exhibit reverse lp···π bonding, while the Z/E‐C₂Cl₂F₂·NH₃, C₂Cl₃F·NH₃ and C₂Cl₄·NH₃ complexes perform half‐lp···π bonding according to the NBO analysis. The lp···π interaction involving the oxygen/nitrogen and the π‐hole of C₂Cl_nF_4?n overwhelms the HaB involving the oxygen/nitrogen and the σ‐hole of the Cl atom. The electron‐donating methyl groups contribute significantly to the two competitive interactions, therefore, DME and TMA engage stronger in the partner molecules than H₂CO and NH₃. Our theoretical study would be useful for future experimental investigation on noncovalent complexes. © 2016 Wiley Periodicals, Inc.     

Synthesis and structural characterization of ferrocenyl indenyl derivatives

In this study, four ferrocenyl indenyl derivatives, C₉H₇–C≡C–Fc (1), C₉H₇–C≡C–Ph–Fc (2), C₉H₇–C≡C–Ph–C≡C–Fc (3), and C₉H₇–Ph–C≡C–Fc (4) (where C₉H₇=indenyl; Fc=C₅H₅FeC₅H₄; Ph=C₆H₅), have been synthesized by Sonogashira and Suzuki cross-coupling reactions and characterized by elemental analysis, and FT-IR, ¹H, ¹³C-NMR, and MS spectroscopic methods, respectively. The molecular structures of 1, 2, and 4 were determined by X-ray single crystal diffraction. Two molecules appeared in the crystal structure of 4, and they interact through an intermolecular hydrogen bond. The electrochemical redox potential differences in 1–4 were investigated using cyclic voltammetry and calculations.     

Formation of Alkyne Bridged Multicobalt Carbonyl Complexes with Tris(2‐Thienyl)Phosphine or Bis(Trimethylsilylethynyl)Phenylphosphine Ligand

Treatment of Co₄(CO)₁₂ with an excess of trimethylsilylacetylene (TMSA) in the presence of tri(2‐thienyl)phosphine in THF at 25 °C for 2 hours yielded six compounds. Two pseudo‐octahedral, alkyne‐bridged tetracobalt clusters, [Co₄(μ₄‐η²‐HC≡CSiMe₃)(CO)₁₀(μ‐CO)₂] ( 4 ) and [Co₄(μ₄‐η²‐HC≡CSiMe³)‐(CO)₉(μ‐CO)₂{P(C₄H₄S)₃}] ( 6 ), along with an alkyne‐bridged dicobalt complex, [Co₂(CO)₅(μ‐HC≡CSiMe₃)‐{P(C₄H₄S)₃}] ( 5 ), were obtained as new compounds. The addition of the thienylphosphine ligand, in fact, facilitates the reaction rate. Reaction of an alkyne‐bridged dicobalt complex, [(η²‐H‐C≡C‐SiMe₃)Co₂(CO)₆] ( 3 ), with a bi‐functional ligand, PPh(‐C≡C‐SiMe₃)₂, yielded an unexpected six‐membered, cyclic compound, {(Ph)(Me₃Si‐C≡C)P‐[(η²‐C≡C‐SiMe₃)Co₂(CO)₅]}₂ ( 7 ). All of these new compounds were characterized by spectroscopic means; the solid‐state structures of ( 5 ), ( 6 ) and ( 7 ) have been established by X‐ray crystallography.     

The scattering of low energy C60 on graphite (0001) surfaces

The interaction between C₆₀ molecules with a graphite (0001) surface has been investigated by means of molecular dynamics simulations. The initial energies of the C60 molecules are 90 and 270 eV, respectively. An empirical model potential suggested by Takai et al. is used to describe the interaction between carbon atoms in the C₆₀ molecule and between the atoms forming the graphite substrate. The interaction between the C₆₀ atoms and the graphite atoms is modeled by a suitable Lennard-Jones potential. The resilience of scattered C₆₀ molecules is observed and its energy distribution is in reasonable agreement with available experimental data, showing no significant dependence of the rebounding translational energy on the incident kinetic energy. The energy partition in the collision has been analyzed in detail and a two-step collision model speculated in the experiments has been discussed based on the simulation results.     

Synthesis and characterization of complexes η5,η5-(CO)3Mn(C5H4-C5H4)(CO)2Fe-η1,η5-C5H4Mn(CO)3 and μ-(C≡C)[C5H4(CO)2Fe-η1,η5-C5H4Mn(CO)3]2

The complex η⁵,η⁵-(CO)₃Mn(C₅H₄-C₅H₄)(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ was synthesized by the reaction of η⁵-Cp(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ with BuⁿLi (THF, ?78 °C) and then with anhydrous CuCl₂. The complex μ-(C≡C)[C₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃]₂ was prepared by the reaction of η⁵-IC₅H₄(CO)₂Fe-η¹,η⁵-C₅H₄Mn(CO)₃ with Me₃SnC≡CSnMe₃ (2:1) in the presence of Pd(MeCN)₂Cl₂.     

A Computational Understanding of Solvent Effect on the Structure,Electronic, Thermochemical,and Spectroscopic Properties of Ni(η2‐C6H4)(H2PCH2CH2PH2) Complex

Here we report the density functional calculations of the molecular parameters including the energy, geometries, electric dipole moments, vibrational IR frequencies, and ¹H and ¹³C NMR chemical shifts of Ni(η²‐C₆H₄ )(H₂PCH₂CH₂PH₂ ) (a benzyne complex). Based on the polarizable continuum model (PCM ), the effect of polarity of the solvent on these parameters was explored. The wavenumbers of υ(C1–C2 ) as well as the ¹H and ¹³C NMR chemical shift values of complex in various solvents were calculated and correlated with the Kirkwood–Bauer–Magat equation (KBM ), the solvent acceptor numbers (ANs ), and the linear solvation energy relationship (LSER ). The bonding interaction between the benzyne and Ni(H₂PCH₂CH₂PH₂ ) fragment was analyzed by means of the energy decomposition analysis (EDA ). The character of the Ni–C bonds of the molecules was analyzed by natural bond orbital (NBO ) analysis. Also, Monte Carlo simulations were used for the calculation of the total energy and solvation free energy of the complex in water.     

A unique Janus PdZn-Co catalyst for enhanced photocatalytic syngas production from CO2 and H2O

The development of excellent catalyst to achieve photocatalytic syngas production from CO₂ and H₂O is a prospective and sustainable strategy to alleviate environment and energy crisis. In this study, a unique Janus PdZn-Co catalyst is prepared by annealed the Pd/IRMOF-3(Co, Zn) precursor. Due to the strong interaction, the electron transfers from PdZn terminal to Co terminal in the Janus structure. The electron-received Co terminal facilitates Co sites coordinate with the electrophilic C atom of CO₂ and the electron-donated PdZn center is easier to coordinate with nucleophilic O atoms of H₂O or CO bonds. The charge redistribution enhances the absorption of CO₂ and H₂O, which promotes H₂ evolution and CO production. In addition, the carbon shell effectively suppresses the metal core agglomeration and facilitates the electron transmission from photosensitizer to metallic active sites. Meanwhile, the ratio of CO/H₂ can be regulated (∼3:1 to 2:1) by adjusting the proportion of Co and PdZn. The Janus structure and graphite carbon synergistically play a profound impact on improving the photocatalytic performance. The optimized PdZn-Co catalyst exhibits a superior photocatalytic CO production rate (20.03 µmol/h) and the H₂ generation rate (9.90 µmol/h) with a ratio of CO/H₂ = 2.02.     

Computational Study of the Substitution Effect on the Mechanism for the Gold(I)‐Catalyzed Ring Expansions of Unactivated Alkynylcyclopropanes

The ring expansion reactions of unactivated alkynylcyclopropanes X‐C≡C‐C₃H₅ → X‐C=C₄H₅ (X = H, F, Cl, Me, OMe, NMe₂, CMe₃) were examined using the density functional theory calculations. All of the structures were completely optimized at the B3LYP/6‐311++G** level of theory. For clarify the effect of the cationic gold(I), we also added AuPH₃⁺ as the catalyst into the system and the structures for Au were calculated at the B3LYP/LANL2DZ level of theory. The main finding of this work is that the singlet‐triplet splitting of X‐C≡C‐C₃H₅ play an important role in determining the kinetic and thermodynamic stability of the unactivated ring expansion reactions. When X‐C≡C‐C₃H₅ with a smaller singlet‐triplet splitting is utilized, the reaction has a smaller activation energy and a larger exothermicity.     

Cyclohexylethynyl complexes of CoII and FeII

This paper deals with the synthesis of six σ-cyclohexylethynyl complexes of Co^II and Fe^II and their characterization by chemical analysis, infrared and ¹H NMR spectra, and magnetic measurements. Four of them are six-coordinate complexes, unsubstituted or substituted, namely K₄[M(C≡C—C₆H₁₁)₆] nNH₃(M = Co, n = 2; M = Fe, n = 0), K₂[Co(C≡C₆H₁₁)₄(NH₃)₂] and K₄[Fe(CN)₄-(C≡C—C₆H₁₁)₂]. Two are four-coordinate complexes of formula [(Ph₃P)₂M-(C≡C₆H₁₁)₂] (M = Co, Fe). All are low-spin complexes, the magnetic moment for the six-coordinate Co(II) complexes, measured at various temperatures, being intermediate between low- and high-spin values.     

A benchmark quantum chemical study of the stacking interaction between larger polycondensed aromatic hydrocarbons

Large-scale electronic structure calculations were performed for the interaction energy between coronene, C₂₄H₁₂ with circumcoronene, C₅₄H₁₈, and between two circumcoronene molecules, in order to get a picture of the interaction between larger graphene sheets. Most calculations were performed at the SCS-MP2 level but we have corrected them for higher-order correlation effects using a calculation on the coronene-circumcoronene system at the quadratic CI, QCISD(T) level. Our best estimate for the interaction energy between coronene and circumcoronene is 32.1?kcal/mol. We estimate the binding of coronene on a graphite surface to be 37.4 or 1.56?kcal/mol per carbon atom (67.5?meV/C atom). This is also our estimate for the exfoliation energy of graphite. It is higher than most previous theoretical estimates. The SCS-MP2 method which reproduces the CCSD(T) and QCISD(T) values very well for smaller aromatic hydrocarbons, e.g., for the benzene dimer, increasingly overestimates dispersion as the bandgap (the HOMO-LUMO separation) decreases. The barrier to the sliding motion of coronene on circumcoronene is 0.45?kcal/mol, and for two circumcoronene molecules 1.85?kcal/mol (0.018 and 0.034?kcal/mol per C atom, respectively). This means that larger graphenes cannot easily glide over each other.     

The Chemical Bond in C2

Quantum chemical calculations using the complete active space of the valence orbitals have been carried out for H_nCCH_n (n=0–3) and N₂. The quadratic force constants and the stretching potentials of H_nCCH_n have been calculated at the CASSCF/cc‐pVTZ level. The bond dissociation energies of the C?C bonds of C₂ and HC≡CH were computed using explicitly correlated CASPT2‐F12/cc‐pVTZ‐F12 wave functions. The bond dissociation energies and the force constants suggest that C₂ has a weaker C?C bond than acetylene. The analysis of the CASSCF wavefunctions in conjunction with the effective bond orders of the multiple bonds shows that there are four bonding components in C₂, while there are only three in acetylene and in N₂. The bonding components in C₂ consist of two weakly bonding σ bonds and two electron‐sharing π bonds. The bonding situation in C₂ can be described with the σ bonds in Be₂ that are enforced by two π bonds. There is no single Lewis structure that adequately depicts the bonding situation in C₂. The assignment of quadruple bonding in C₂ is misleading, because the bond is weaker than the triple bond in HC≡CH.     

Surface Adsorbed Hydroxyl: A Double-Edged Sword in Electrochemical CO2 Reduction over Oxide-Derived Copper

Oxide-derived Cu (OD−Cu) featured with surface located sub-20 nm nanoparticles (NPs) created via surface structure reconstruction was developed for electrochemical CO₂ reduction (ECO₂RR). With surface adsorbed hydroxyls (OH_ad) identified during ECO₂RR, it is realized that OH_ad, sterically confined and adsorbed at OD−Cu by surface located sub-20 nm NPs, should be determinative to the multi-carbon (C₂) product selectivity. In situ spectral investigations and theoretical calculations reveal that OH_ad favors the adsorption of low-frequency *CO with weak C≡O bonds and strengthens the *CO binding at OD−Cu surface, promoting *CO dimerization and then selective C₂ production. However, excessive OH_ad would inhibit selective C₂ production by occupying active sites and facilitating competitive H₂ evolution. In a flow cell, stable C₂ production with high selectivity of ∼60 % at −200 mA cm⁻² could be achieved over OD−Cu, with adsorption of OH_ad well steered in the fast flowing electrolyte.     

Intermolecular interactions of formic acid with benzene: Energy decomposition analyses with ab initio MP2 and double‐hybrid density functional computations

The intermolecular interactions of formic acid (HCOOH) with benzene (C₆H₆) have been investigated using localized molecular orbital energy decomposition analyses (LMO‐EDA) with ab initio MP2 and several double‐hybrid density functionals. The molecular geometries of five HCOOH…C₆H₆ complexes and corresponding benchmark total interaction energies at the CCSD(T)/CBS level are taken from literature (Zhao et al., J. Chem. Theory Comput. 2009, 5, 2726). According to the results of LMO‐EDA with the MP2 method, the dispersion energies are found to be as important as the electrostatic energies for the total interaction energies of the five HCOOH…C₆H₆ complexes. Based on LMO‐EDA with the double‐hybrid density functionals of B2PLYP, B2K‐PLYP, B2T‐PLYP, and B2GP‐PLYP computations, two new parameters for the framework of B2PLYP are extrapolated. These two new parameters are tested with other 10 complexes involving C₆H₆ (Crittenden, J. Phys. Chem. A 2009, 113, 1663), and they perform well on predicting the corresponding total interaction energies. Interestingly, these two new parameters for the framework of B2PLYP also perform well on the noncovalent complexation energies database (NCCE31/05) developed by Truhlar's group (Zhao and Truhlar, J. Phys. Chem. A 2005, 109, 5656). Therefore, these two new parameters appear to be suitable for investigating the noncovalent interactions, and they are denoted as B2N‐PLYP, where N stands for the noncovalent interaction. This study is expected to provide new insight into the derivation of double‐hybrid density functionals for studying the noncovalent interactions. © 2013 Wiley Periodicals, Inc.     

Zur Kenntnis der Chemie und der Struktur von Olefin-monocyano-dicarbonyl-ferrat-Anionen

About Chemistry and Structure of Olefin-monocyano-dicarbonyl-ferrate Anions By the reactions of olenFe(CO)₃ [olen = C₅H₈(isoprene), C₇H₁₀(cycloheptadiene-1,3), C₈H₁₄(2,5-dimethylhexadiene-1,3)] with sodium bis [trimethylsilyl]amide the new anions [olenFe(CO)₂CN]^? are formed. All so far known [olenFe(CO)₂CN]^? complexes [olen = C₅H₈(isoprene), C₇H₁₀[cycloheptadiene-1,3], C₄H₆(butadiene), C₅H₈(pentadiene-1,3), C₆H₈(cyclohexadine-1,3), C₆H₁₀(2,3-dimethylbutadiene), C₈H₈(cyclooctatetraene)] have fluctional structures in solution as shown by ¹³C NMR spectroscopic investigations. At low temperatures only the isomer exists, in which the CN^? ligand and one of the two CO molecules occuppy the basal positions of a square pyramide together with 2 C atoms of the diene part.     

X-ray spectroscopic study of graphite fluoride (C2F) n intercalated with benzene

Samples of intercalated graphite fluoride of the C₂F·zR type (R is C₆H₆) before and after heating to 150 °C in a spectrometer vacuum chamber were studied by X-ray fluorescence spectroscopy. The C-Kα differential spectra of the samples mainly characterizes the electron state of carbon atoms in the benzene molecule inside the C₂F matrix. The differential spectrum is distinct from the spectrum of solid benzene by additional maxima, which indicate the interaction between the benzene molecules and the graphite fluoride matrix. Comparative analysis of the spectrum of the heated sample and those of graphite and graphite fluoride (CF) _n suggests that the layers of the C₂F matrix contain considerable regions of both completely fluorinated and graphite-like regions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 705–708, April, 2000.