Interaction Of Benzene Research Articles

Are C–H⋯O interactions linear? The case of aromatic CH donors

The angular distribution of the C–H⋯O interactions of aromatic C–H donors was studied by analyzing data in the Cambridge Structural Database (CSD) and by ab initio calculations. The analysis of the C–H⋯O interactions in the crystal structures from the CSD indicate that aromatic C–H donors do not show strong preference for linear contacts and that the preference depends on the type of the atom or group in the o-position to the interacting C–H group. Namely, the acceptor oxygen atom has possibility for simultaneous C–H⋯O interactions with the hydrogen atom in the o-position to the interacting C–H group. The C–H⋯O interactions of aromatic molecules with two hydrogen atoms in the o-positions do not show preference for linear contacts. Bifurcated interactions are observed in a substantial number of structures. Moreover, in the structures with a substituent in the o-position there is possibility for simultaneous interactions, depending on the nature of the substituent. The results of the ab initio calculations are in accord with the CSD data and show that the stabilization energy is larger for bifurcated than for linear interactions. The calculated energies at the MP2/cc-pVTZ level for linear C–H⋯O interactions of benzene with water, methanol, and acetone are 1.28, 1.47, 1.45 kcal mol−1; while for bifurcated interactions are 1.38, 1.63, and 1.70 kcal mol−1, respectively. Analysis of the data in the CSD and the ab initio calculations indicate that the vicinity of the other possible hydrogen donors in the aromatic molecules causes a small tendency for linear contact in the C–H⋯O interactions. The result that nonlinear interactions are not energetically disfavoured, because of the possibility for simultaneous interactions, can be very important for recognizing C–H⋯O interactions in biomolecules containing aromatic groups, like proteins.

ChemInform Abstract: The Interaction of Benzene and Toluene with Rh Dispersed on SiO2, Al2O3, and TiO2 Carriers.

The interaction of benzene and toluene with Rh dispersed on SiO[sub 2], Al[sub 2]O[sub 3], and TiO[sub 2] carriers is investigated employing temperature-programmed desorption, temperature-programmed reaction and steady-state hydrogenation techniques. It is found that the aromatic molecules are weakly adsorbed on the carriers and are readily hydrogenated by spill-over hydrogen at room temperature. The surface coverage of benzene and toluene on Rh is found to be 0.39-0.42 and 0.34-0.38, respectively, following room temperature adsorption of 0.1 bar benzene or 0.03 bar toluene. Aromatic molecules adsorbed on Rh do not desorb molecularly, but dissociate at high temperatures producing hydrogen. Dehydrogenation reactivity is found to follow the order: Rh/TiO[sub 2] > Rh/Al[sub 2]O[sub 3] > Rh/SiO[sub 2]. Under hydrogen flow, only a small fraction of the adsorbed aromatic molecules is hydrogenated, and at sufficiently high temperatures the remainder is converted to CH[sub 4]. Results of benzene hydrogenation under steady-state conditions are questioned in view of carrier participation in the reaction scheme. 37 refs., 7 figs., 3 tabs.

Study of Intermolecular Interactions of Acetophenone and Benzene at 303.15, 313.15 and 323.15 K

The behaviour of mixture of acetophenone and benzene as a function of temperature and composition has been investigated by measuring sound velocity in conjunction with density at 303.15, 313.15and 323.15 K. Derived parameters computed from density (?) and sound velocity (U) have been used to determine excess molar volumes (VME), excess isentropic compressibilities (KSE) and excess inter molecular free length (LfE).The excess functions have been discussed in terms of intermolecular interactions between the components of binary mixture. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature range 303.15-323.15K. The computed results have been fitted to the Redlich-Kister polynomial equation to estimate the smoothening coefficients and standard deviations for this system. The validity of various theoretical approaches of liquids has been tested for the system by comparing theoretical sound speeds with those experimentally determined over the entire composition range in the temperature303.15-323.15K.

A bonding study of CO–benzene co-adsorption on Rh(1 1 1)

The co-adsorption of carbon monoxide and benzene on Rh(1 1 1) has been studied using density functional calculations. We used the ordered p(3 × 30) surface unit cell for the study. Besides, a comparison of the co-adsorption with CO and benzene two-dimensional networks is also given. The hydrogen of the benzene ring presents a bonding angle of 26°. The electronic structure reveals that the CO does not interact with benzene. Regarding the bonding, the Rh–Rh overlap population decreases 36.7% after co-adsorption, which is almost, the same decrease after CO adsorption. The CO–benzene interaction is very weak and a small H benzene–C CO OP of 0.001 is detected.

Study of complex formation between β-cyclodextrin and benzene

In this work study of complex formation of β-cyclodextrin with benzene was performed both experimentally and theoretically. Interaction of benzene with β-cyclodextrin in aqueous solutions was investigated by means of UV spectroscopy at temperatures in the range 291–303 K. The stoichiometric composition, stability constant, and thermodynamic parameters of “β-cyclodextrin-benzene” supramolecular structures formation were calculated from spectroscopic data. It was proved that 1:1 inclusion complex is mainly formed in aqueous solutions. The calculations of a spatial structure, formation energy, and vibration spectra in IR range for the complex of β-cyclodextrin with benzene were performed by Hartree–Fock–Roothaan method within PM3 semiempirical approximation with quantum chemistry package GAMESS (version 6.4). The calculated energy parameters for “β-cyclodextrin-benzene” inclusion complex are in agreement with experimental data.

Study of polycyclic aromatic hydrocarbons adsorbed on graphene using density functional theory with empirical dispersion correction

The interaction of polycyclic aromatic hydrocarbon molecules with hydrogen-terminated graphene is studied using density functional theory with empirical dispersion correction. The effective potential energy surfaces for the interaction of benzene, C(6)H(6), naphthalene, C(10)H(8), coronene, C(24)H(12), and ovalene, C(32)H(14), with hydrogen-terminated graphene are calculated as functions of the molecular displacement along the substrate. The potential energy surfaces are also described analytically using the lowest harmonics of the Fourier expansion. It is shown that inclusion of the dispersive interaction, which is the most important contribution to the binding of these weakly bound systems, does not change the shape of the interaction energy surfaces or the value of the barriers to the motion of polycyclic aromatic hydrocarbon molecules on graphene. The potential energy surfaces are used in the estimation of the friction forces acting on the molecules along the direction of motion. These results underpin the modelling, using density functional theory, of electromechanical devices based on the relative vibrations of graphene layers and telescoping carbon nanotubes.

The effects of perfluorination on carbohydrate–π interactions: computational studies of the interaction of benzene and hexafluorobenzene with fucose and cyclodextrin

The effect of benzene fluorination on C-H...pi interactions is studied using a number of computational methods applied to a range of intermolecular complexes. High level wavefunction methods (CCSD(T)) predict a slightly greater interaction energy for complexes of benzene with methane or fucose, compared to corresponding complexes involving hexafluorobenzene. A number of more approximate treatments, DFT with the M06-2X functional, PM3-D* and MM methods, give interaction energies within 1 kcal mol(-1) of the high level values, and also correctly predict that the interaction energy is slightly greater for benzene compared to hexafluorobenzene. However, the DFT-D model used here predicts that the interaction energy is slightly greater for hexafluorobenzene. Molecular dynamics simulations, employing the GLYCAM-06 force field, validated here, are used to model the complexes of benzene and hexafluorobenzene with beta-cyclodextrin in aqueous solution. We predict the binding free energies of the complexes to be within 0.5 kcal mol(-1), and suggest that the different chemical shifts of the H5 protons observed in the two complexes arise from their slightly different structures, rather than from different binding energies.

The ejection of triatomic molecular hydrogen ions H3+ produced by the interaction of benzene molecules with ultrafast laser pulses

The ejection process of triatomic molecular hydrogen ions produced by the interaction of benzene with ultrafast laser pulses of moderate strong intensity ( approximately 10(14) W/cm(2)) is studied by means of TOF mass spectrometry. The H(3) (+) formation can only take place through the rupture of two C-H bonds and the migration of hydrogen atoms within the molecular structure. The H(3) (+) fragments are released with high kinetic energy (typically 2-8 eV) and at laser intensities >or=10(14) W/cm(2), well above that required for the double ionization of benzene, suggesting that its formation is taking place within multiply charged parent ions. The relative ejection efficiency of H(3) (+) molecular hydrogen ions with respect to the atomic ones is found to be strongly decreasing as a function of the laser intensity and pulse duration (67-25 fs). It is concluded that the H(3) (+) formation is only feasible within parent molecular precursors of relatively low charged states and before significant elongation of their structure takes place, while the higher multiply charged molecular ions preferentially dissociate into H(+) ions. The ejection of H(2) (+) ions is also discussed in comparison to the production of H(3) (+) and H(+) ions. Finally, by recording the mass spectra of two deuterium label isotopes of benzene (1,2-C(6)H(4)D(2), 1,4-C(6)H(4)D(2)) it is verified that the ejection efficiency of some molecular fragments, such as D(2)H(+), DH(+), is dependent on the specific position of hydrogen atoms in the molecular skeleton prior dissociation.

Polarizable Intermolecular Potentials for Water and Benzene Interacting with Halide and Metal Ions

A complete derivation of polarizable intermolecular potentials based on high-level, gas-phase quantum-mechanical calculations is proposed. The importance of appreciable accuracy together with inherent simplicity represents a significant endeavor when enhancement of existing force fields for biological systems is sought. Toward this end, symmetry-adapted perturbation theory (SAPT) can provide an expansion of the total interaction energy into physically meaningful e.g. electrostatic, induction and van der Waals terms. Each contribution can be readily compared with its counterpart in classical force fields. Since the complexity of the different intermolecular terms cannot be fully embraced using a minimalist description, it is necessary to resort to polyvalent expressions capable of encapsulating overlooked contributions from the quantum-mechanical expansion. This choice results in consistent force field components that reflect the underlying physical principles of the phenomena. This simplified potential energy function is detailed and definitive guidelines are drawn. As a proof of concept, the methodology is illustrated through a series of test cases that include the interaction of water and benzene with halide and metal ions. In each case considered, the total energy is reproduced accurately over a range of biologically relevant distances.

THE CO-ADSORPTION OF BENZENE ANDCOONCo(0001)

The co-adsorption of carbon monoxide and benzene on Co (0001) has been studied using density functional calculations. We used the ordered [Formula: see text] surface unit cell. A comparison of the co-adsorption with CO and benzene two-dimensional networks is also given. The electronic structure reveals that the CO orbitals interact with benzene and Co layer. Regarding the bonding, the Co–Co overlap population decrease 18% after benzene adsorption and increase a little after CO adsorption with a net 14.6% decrease in the co-adsorption system. The CO –benzene interaction is shown by the changes in the C – O ( CO ) and C – H (benzene) bonds.

Structural effects on the interactions of benzene and naphthalene sulfonates with activated carbon cloth during adsorption from aqueous solutions

Interactions of benzene and naphthalene sulfonates with activated carbon cloth (ACC) during adsorption from aqueous solutions were investigated. Systematically chosen sulfonates were sodium salt of benzene sulfonic acid (NaBS), disodium salt of 1,3-benzene disulfonic acid (Na2BDS), sodium salt of 1-naphthalene sulfonic acid (NaNS), disodium salt of 1,5-naphthalene disulfonic acid (Na2NDS) and trisodium salt of 1,3,(6 or 7)-naphthalene trisulfonic acid (Na3NTS). The adsorption behaviors of these adsorbates from solutions in water and in 0.01 M H2SO4 onto the ACC were monitored by in-situ UV–visible spectroscopic technique. The order of rates and extents of adsorption of sulfonates were explained in terms of acidity of the medium and structural factors influencing the interactions between sulfonates and the ACC surface. Kinetic data of adsorption were treated according to pseudo first-order, pseudo second-order, Elovich and intra-particle diffusion models. The best model representing the experimental kinetic data was found to be the pseudo second-order model. Adsorption isotherms of the sulfonates onto the ACC were derived at 30 °C. Isotherm data were found to fit the Freundlich model better than the Langmuir model.

CH/π Interaction in Benzene and Substituted Derivatives with Halomethane: A Combined Density Functional and Dispersion-Corrected Density Functional Study

The present work intends to establish the efficiency of dispersion-corrected density functionals in explaining the potential energy curves of benzene-methane, benzene-fluoroform, and 1,3,5-trifluoro benzene-methane complexes. The interaction energies of all of the complexes under investigation have been evaluated using both van der Waals-corrected and normal gradient-corrected Perdew-Burke-Ernzerhof and Becke-Lee-Yang-Parr density functionals. Our analyses suggest that the potential energy curves for both benzene-methane and benzene-fluoroform complexes are in excellent agreement with highly accurate coupled cluster (CCSD(T)) results as well as high-level counterpoise-corrected MP2 results. Remarkably, the interaction energies of the benzene-fluoroform complex are fairly higher than those of the other two complexes. This is primarily attributed to the dispersion correction present in it. Finally, the overall study highlights the importance of halogen substitution in strengthening the CH/pi interactions.

First-principles study of benzene on noble metal surfaces: Adsorption states and vacuum level shifts

We have studied the interaction of benzene with Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces using density functional theory (DFT) within a generalized gradient approximation (GGA) and the van der Waals density functional [vdW-DF; M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401]. The adsorption energies using vdW-DF are significantly more accurate than those using GGA, while the equilibrium adsorption distances between benzene and metal substrates ( Z C eq ) calculated by both GGA and vdW-DF are almost identical. The work function changes induced by the adsorption of benzene are significantly underestimated compared with the experimental values, as a result of the overestimation of Z C eq by both GGA and vdW-DF. Instead of determining the Z C eq values from first-principles calculations, we deduced the most probable adsorption distances in such a way as to reproduce the experimentally-observed work function changes. The deduced adsorption distance ( Z C ded ) is shortest on Cu(1 1 1) while it is longest on Ag(1 1 1), reflecting the strength of the interactions between benzene and the metal surfaces. It turns out that the substrate dependence of the work function change is mainly ascribed to the difference in the benzene–metal distance ( Z C). Charge transfer and work function changes by the adsorption of benzene were analyzed by means of the induced density of interface states (IDIS) model [H. Vázquez, R. Qszwaldowski, P. Pou, J. Ortega, R. Pérez, F. Flores, A. Kahn, Europhys. Lett. 65 (2004) 802], and compared with the self-consistent GGA calculations. The vacuum level shifts estimated by the IDIS model agree with the GGA results for Z C ⩾ 0.3 nm . On the other hand, the discrepancy between the two methods becomes larger for Z C ⩽ 0.3 nm , where the back donation from the metal substrates to the adsorbate becomes significant. We show that the IDIS model reasonably works well for benzene on Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces because Z C ded ≈ 0.3 nm on all surfaces. However, our analysis reveals that the actual charge density redistribution induced by the adsorption of benzene is more complicated than that assumed in the IDIS model.

Electronic structure of poly(azomethine) thin films

Poly(1,4-phenylene-methylidynenitrilo-1,4-phenylenenitrilomethylidyne) (PPI) backbone approximated with poly(p-phenylene vinylene)like polymer composed of alternate phenylene and vinylenelike units is treated within pi electron approximation in terms of the chain composed of united atoms built up of virtual benzene and ethylene atoms. Electronic structure of the united atom is derived from interactions of benzene p and beta bands with V band of ethylene, taking into account that continuity of their pi systems results from overlap of vinylenelike highest occupied molecular orbital and lowest unoccupied molecular orbital orbitals with relevant components of benzene molecular orbitals having phase at parapositions. Electronic band structure has been derived within pi-electron approximation in a way resembling tight binding approximation usually applied to semiconductors. The proposed model is suitable to interpret UV-visible spectra of PPI with additional explaining vibronic progressions. Additionally, an expected location of lone pair related level is proposed.

Organometallic dithiolene complexes of benzenedithiolate analogues with π-coordinating and π-interacting Cp* ligand

Organometallic dithiolene complexes, which were formulated as [Cp *M(dcbdt)] and [Cp *M(dcdmp)] (M = Co, Rh, Ir; Cp * = η 5-pentamethylcyclopentadienyl, dcbdt = 4,5-dicyanobenzene-1,2-dithiolate, dcdmp = 2,3-dicyano-5,6-dimercaptopyrazine) were prepared from a low valent Cp *Co I or high valent Cp *M III species (M III = Co III, Rh III, Ir III). The UV–Vis absorption spectral and electrochemical data of them were obtained. The lowest absorption (HOMO–LUMO) energies of them became redshift in order of the Co > Rh > Ir complexes. The reduction potentials suggested that the central metal modifies their LUMO levels. The molecular and crystal structures of [Cp *Co(dcbdt)] ( 3a), [Cp *Co(dcdmp)] ( 4a) and [Cp *Rh(dcdmp)] ( 4b) were determined by X-ray diffraction studies. The cobalt complexes 3a and 4a were monomeric, formally 16-electron complexes and have two-legged piano-stool geometries. The crystal structure of 3a indicated some plane-to-plane intermolecular interactions such as benzene⋯benzene interaction on the dcbdt ligand and two Cp *⋯benzene π–π stackings. 4a showed plane-to-plane interaction with a pseudo-4-fold-symmetry arrangement between the pyrazine moieties on the dcdmp ligand. The rhodium complex 4b was dimeric in the crystal to form a criss-cross arrangement and had a three-legged piano-stool geometry, but it was monomerized in solution. The dimer of 3b was observed in the oxidation process of the cyclic voltammogram.

Interaction of Benzene with Transition Metal Cations: Theoretical Study of Structures, Energies, and IR Spectra.

The cation-π interactions have been intensively studied. Nevertheless, the interactions of π systems with heavy transition metals and their accurate conformations are not well understood. Here, we theoretically investigate the structures and binding characteristics of transition metal (TM) cations including novel metal cations (TM(n+) = Cu(+), Ag(+), Au(+), Pd(2+), Pt(2+), and Hg(2+)) interacting with benzene (Bz). For comparison, the alkali metal complex of Na(+)-Bz is also included. We employ density functional theory (DFT) and high levels of ab initio theory including Møller-Plesset second-order perturbation (MP2) theory, quadratic CI method with single and double substitutions (QCISD), and the coupled cluster theory with single, double, and perturbative triple excitations (CCSD(T)). Each of the transition metal complexes of benzene exhibits intriguing binding characteristics, different from the typical cation-π interactions between alkali metal cations and aromatic rings. The complexes of Na(+), Cu(+), and Ag(+) favor the conformation of C6v symmetry with the cation above the benzene centroid (πcen). The formation of these complexes is attributed to the electrostatic interaction, while the magnitude of charge transfer has little correlation with the total interaction energy. Because of the TM(n+)←π donation, cations Au(+), Pd(2+), Pt(2+), and Hg(2+) prefer the off-center π conformation (πoff) or the π coordination to a C atom of the benzene. Although the electrostatic interaction is still important, the TM←π donation effect is responsible for the binding site. The TM(n+)-Bz complexes give some characteristic IR peaks. The complexes of Na(+), Cu(+), and Ag(+) give two IR active modes between 800 and 1000 cm(-1),which are inactive in the pure benzene. The complexes of Au(+), Pd(2+), Pt(2+), and Hg(2+) give characteristic peaks for the ring distortion, C-C stretching, and C-H stretching modes as well as significant red-shifts in the CH out-of-plane bending.

Strong N−H···π Hydrogen Bonding in Amide−Benzene Interactions

Among the weak intermolecular interactions found in proteins, the amide N--H...pi interaction has been widely observed but remains poorly characterized as an individual interaction. We have investigated the isolated supersonic-jet-cooled dimer of the cis-amide and nucleobase analogue 2-pyridone (2PY) with benzene and benzene-d6. Both MP2 and SCS-MP2 geometry optimizations yield a T-shaped structure with a N--H...pi hydrogen bond to the benzene ring and the C=O group above, but far from the C--H bonds of benzene. The CCSD(T) calculated binding energy at the optimum geometry is De = 25.2 kJ/mol (dissociation energy D0 = 21.6 kJ/mol), corresponding to the H-bond strength of the water dimer or of N--H...O hydrogen bonds. The T-shaped geometry is supported by the infrared-ultraviolet depletion spectra of 2PY x benzene: The N--H stretch vibrational frequency is lowered by 56 cm(-1), and the C=O stretch vibration is lowered by 10 cm(-1), relative to those of bare 2PY, indicating a strong N--H...pi interaction and a weak interaction of the C=O group. The benzene C--H infrared stretches exhibit very small shifts (approximately 2 cm(-1)) relative to benzene, signaling the absence of interactions with the benzene C--H groups. The infrared spectral shifts are consistent with a strong nonconventional pi hydrogen bond and a T-shaped structure for 2PY x benzene. Symmetry-adapted perturbation theory calculations show that the N--H...pi interaction is by far the dominant stabilization factor.

Effect of substrate interaction on the degradation of methyl tert-butyl ether, benzene, toluene, ethylbenzene, and xylene by Rhodococcus sp

It was examined the substrate interactions of benzene (B), tolulene (T), ethylbenzene (E), xylene (X), and methyl tert-butyl ether (M) in binary, ternary, quaternary, and quinary mixtures by Rhodococcus sp. EH831 that could aerobically degrade all of five single components. The specific degradation rates (SDRs) of B, T, E, X, and M were 234, 913, 131, 184 and 139 μmol g-dry cell weight (DCW) −1 h −1, respectively. In binary, ternary, quaternary, and quinary mixtures of them, ethylbenzene was the strongest inhibitor for the other substrates, and methyl tert-butyl ether was the weakest inhibitor. Interestingly, no degradation of benzene and methyl tert-butyl ether was found in the coexistence of ethylbenzene. The degradation of benzene followed only after toluene became exhausted when both was present. Ethylbenzene was least inhibited by methyl tert-butyl ether and most inhibited by toluene.

Enhanced ferromagnetic interaction in metallacyclic complexes incorporating m-phenylenediamidato bridges.

The double stranded Cu(II)2-metallacyclic complex of formula [Cu2(mbpb)2].2H2O (1) and the triple stranded Ni(II)2-metallacyclic complexes of formula [Ni2(Hmbpb)3]PF6.21H2O (2), [Co(H2O)6][Ni2(mbpb)3)]THF.10H2O (3) and {Ag2(H2O)[Ni2(mbpb)3]}.11H2O (4) (where H2mbpb is the bisbidentate dinucleating bridging ligand 1,3-bis(pyridine-2-carboxamide) benzene) have been synthesised and characterised by single-crystal X-ray diffraction. Within the dinuclear molecules, metal ions are bridged by either fully or semideprotonated bisbidentate ligands, which are coordinated through the pyridine and amidato nitrogen donor atoms. In complex 4 the triple stranded dinuclear Ni2 units are connected to the Ag+ cations through O-amidato bridges and Ag-pi(benzene) interactions to afford a 1D bimetallic chain. Cu2 (1) and Ni2 (2-4) complexes exhibit ferromagnetic coupling between the metal ions through the bridging ligand with J(Cu-Cu) = 21.1 cm(-1) and J(Ni-Ni) in the range of 2.9-3.6 cm(-1), respectively. Amongst copper(II) dinuclear complexes bearing m-phenylenediamidato bridges, complex 1 exhibits the stronger ferromagnetic exchange coupling reported so far. DFT calculations firstly confirm that the spin polarisation mechanism is responsible for the ferromagnetic coupling, and secondly allows us to predict stronger ferromagnetic couplings in Cu(II)(2) complexes with larger tetrahedral distortions of the CuN4 coordination environment.

Water−Benzene Interactions: An Effective Fragment Potential and Correlated Quantum Chemistry Study

Structures and binding in small water-benzene complexes (1-8 water molecules and 1-2 benzene molecules) are studied using the general effective fragment potential (EFP) method. The lowest energy conformers of the clusters were found using a Monte Carlo technique. The binding energies in the smallest clusters (dimers, trimers, and tetramers) were also evaluated with second order perturbation theory (MP2) and coupled cluster theory (CCSD(T)). The EFP method accurately predicts structures and binding energies in the water-benzene complexes. Benzene is polarizable and consequently participates in hydrogen bond networking of water. Since the water-benzene interactions are only slightly weaker than water-water interactions, structures with different numbers of water-water, benzene-water, and benzene-benzene bonds often have very similar binding energies. This is a challenge for computational methods.