Benzene Solution Research Articles

Conformational Equilibria of Bridled Chiroporphyrins in Solution Investigated by Vibrational Circular Dichroism

A series of bridled chiroporphyrins (BCP) and their metal complexes were prepared, in which two n-methylene straps connect adjacent meso substituents by ester linkages. These compounds can exist as four atropisomers (αααα, αβαβ, αααβ, or ααββ) depending on the position of the meso groups relative to the macrocycle (α when above and β when below). We characterized the conformation of these chiral porphyrins and their metal (Zn, Ni, Mn) complexes by vibrational circular dichroism (VCD) associated with ab initio calculations. VCD spectra of the three metalloporphyrins were recorded in CDCl₃ and benzene solutions and ab initio calculations of their four atropoisomers were performed at the Density Functional Theory (DFT) level. The bridled chiroporphyrin with the longer straps (9 CH₂) and its nickel(II) complex can be isolated as the αβαβ atropisomer in the solid state and were found with the same conformation in CDCl₃ and benzene solutions. The bridled chiroporphyrin with the shortest straps (8 CH₂) and its zinc(II) complex can be isolated as the αααα atropisomer in the solid state, but in solution they are subject to atropisomeric equilibria, resulting in atropisomer distributions that are strongly solvent-dependent. Comparison of the experimental VCD spectra with the predicted spectra of the four atropisomers allowed the quantification of these distributions. Finally, the manganese(III) complex also exhibits an atropisomeric equilibria in solution which is slightly solvent-dependent.

Metal ion-TiO2 nanocomposites for the selective photooxidation of benzene to phenol and cycloalkanol to cycloalkanone

TiO2 has attracted a great deal of research attention for photochemical redox combined transformation of organic functional groups into useful products. In this context, various transition metal ions impregnated-TiO2 catalysts are prepared and characterised by SEM surface morphology, TEM size and shape analysis, magnetic susceptibility measurement and tested for benzene and cycloalkanol oxidation. The highest yield (14.8 μmol) and selectivity (80%–86%) of phenol as compared to hydroquinone (yield = 2%–8%) is achieved during 1–2-h irradiation (125 W Hg arc lamp, 10.4 mW/cm2) of aqueous suspension of 5 wt% Fe+3-TiO2 and 20 mM benzene solution. The co-catalytic activity of metal ions imparted to TiO2 during benzene oxidation was highly enhanced in the order Fe+3 > Ag+ > Au+3 > Cu+2 as compared to very low reactive elemental metal loading. Metal/metal ion deposition onto TiO2 highly reduces the cycloketone yield whereas bare TiO2 exhibits the maximum amount of cyclohexanone (60%) and cycloheptanone (50%) formation from respective cycloalkanol photooxidation up to 4-h irradiation.

Raman Second Hyperpolarizability Determination Using Computational Raman Activities and a Comparison with Experiments

Doubly vibrationally enhanced (DOVE) four-wave mixing spectroscopy, an optical analogue to 2D NMR, involves two infrared transitions and a Raman transition. The magnitude of the DOVE second hyperpolarizability γ (or third-order susceptibility χ((3))) can be theoretically estimated if the values of the dipolar moments of the two infrared transitions and the γ of the Raman transition are known. The Raman γ can be measured by using the four-wave mixing interferometric method or conventional Raman spectroscopy in the presence of an internal standard. In this work, we examine if one can use the Raman activity computed from density functional theory calculation to determine the Raman γ of selected vibrational modes of several samples including deuterated benzene, acetonitrile, tetrahydrofuran, and sodium benzoate aqueous solution. The 992 cm(-1) Raman band of benzene serves as an internal standard for organic solvents, and the 880 cm(-1) Raman band of hydrogen peroxide is for the aqueous solution sample with known γ values. We have found that the predicted Raman γ values from the computational Raman activities match experimental data reasonably well, suggesting a facile approach to predict the Raman γ of interested systems.

Dynamics of intermolecular electron transfer from amines to the excited states of 9-fluorenone

Abstract Dynamics of photoinduced electron transfer (PET) reactions between the singlet (S 1 ) and the triplet (T 1 ) excited states of 9-fluorenone or simply fluorenone and a few aromatic and aliphatic amines have been investigated under both diffusive and non-diffusive conditions. Formation of the fluorenone anion radical confirms the electron transfer (ET) from the amines to the excited states of fluorenone. Rate constants for both the forward ET process, k CS , and the charge recombination (CR) process, k CR , have been determined in acetonitrile and benzene solutions. Sub-picosecond time-resolved transient absorption study reveals that quenching of the S 1 state in acetonitrile is biexponential. Lifetime of one of these two components is independent of quencher concentration and its values determined for aniline (7.1 ps), dimethylaniline (8.5 ps) and diethylaniline (6.8 ps) are very similar. It represents the non-diffusive component of the PET reaction. But the lifetime of the other component decreases with increasing quencher concentration and the rate of this diffusive component of the PET reaction nearly agrees with the value determined using steady state fluorescence quenching method. To determine the intrinsic values of the rates of the PET reactions involving the S 1 state of fluorenone, the PET dynamics have been studied in these three neat donor solvents. The forward ET process is biexponential and the lifetimes of these two components are very similar in these solvents and vary in the range 0.3–0.5 ps and 6–8 ps. Nonexponential dynamics of the PET reactions conducted in neat donor–solvents have been discussed using a simple solvent reorientational model.

Development of AgCl/poly(MMA-co-AM) hybrid pervaporation membranes containing AgCl nanoparticles through synthesis of ionic liquid microemulsions

AgCl nanoparticles were synthesized in a water-in-oil microemulsion using the ionic liquid 1-dodecyl-3-methyl imidazoium chloride (C12mimCl) as the surfactant and methyl methacrylate–acrylamide (MMA–AM) mixture as the oil phase. An aqueous AgNO3 solution was added to the microemulsion as the source of Ag+ ions. Subsequently, AgCl/poly(MMA-co-AM) hybrid membranes were prepared by in situ microemulsion polymerization, and applied for pervaporation of mixtures of benzene and cyclohexane. The effects of C12mimCl (CC12mimCl) and AgNO3 (CAgNO3) concentrations on the formation and morphology of AgCl nanoparticles were studied. The structure of AgCl/poly(MMA-co-AM) hybrid membranes was examined and analyzed with SEM and XRD. The swelling–sorption behavior of AgCl/poly(MMA-co-AM) hybrid membranes in the benzene and cyclohexane solutions, and their separation ability were measured. The AgCl nanoparticles that were formed in the ionic liquid-based microemulsion were found to be spherical with a mean diameter of 20nm within a narrow size range. The number of AgCl nanoparticles increased with increasing CC12mimCl, and the mean diameter of the AgCl nanoparticles increased with increasing CAgNO3. The AgCl/poly(MMA-co-AM) hybrid membranes were found to have a core–shell structure with AgCl as the core and poly(MMA-co-AM) as the shell. The AgCl nanoparticles were uniformly dispersed in the poly(MMA-co-AM) matrix. The AgCl/poly(MMA-co-AM) hybrid membranes displayed the characteristics of preferentially selective sorption–swelling benzene and demonstrated better pervaporation performance than that of the membrane without nanoparticles in separating the benzene/cyclohexane mixture.

Lanthanide pentafluorophenolates. Synthesis, structure and luminescent properties

The pentafluorophenolates of lanthanides Ln(OC6F5)3 (Ln = Nd (1), Tb (2), Er (3)) were prepared by the reactions of pentafluorophenol with appropriate silylamides Ln[N(SiMe3)2]3 in benzene or toluene solution. The same reactions in ether or methanol medium afforded the solvated complexes Ln(OC6F5)3(Et2O)3 (Ln = Nd (4), Eu (5), Tb (6), Er (7), Gd (8)) or Nd(OC6F5)3(MeOH)3 (9), respectively. The phenanthroline complexes Ln(C6F5O)3(phen) (Ln = Pr (10), Nd (11), Er (12)), Ln(OC6F5)3(phen)2 (Ln = Sm (13), Tb (14), Ho (15), Ln(OC6F5)3(phen)2(Et2O) (Ln = Eu (16), Yb (17)), and Ln(OC6F5)3(phen)(Et2O)3 (Ln = Eu (18), Nd (19), Ce (20), Dy (21)), Ln(OC6F5)3(phen)2(H2O) (Ln = Sm (22), Ho (23)), and Gd(OC6F5)3(phen)2(MeOH) (24) were obtained when the reactions were carried out in the presence of 1,10-phenanthroline. The complexes with pyridine Tb(OC6F5)3(py)5 (25) and 2,2′-bipyridyl Ln(OC6F5)3(bpy)2 (Ln = Tb (26), Yb (27)) were synthesized similarly. Compounds 7, 22, 23, and 24 were characterized by X-ray analysis. The complexes Ln(OC6F5)3 decompose above 150 °C in vacuum to give lanthanide fluorides and octofluorodibenzo-p-dioxine. Phenanthroline derivatives are stable up to 310 °C. Luminescence spectra of all the obtained complexes in visible region contain a broad band of ligand-centered emission peaked at 405–415 nm. Spectra of samarium 13, europium 5, 16, 18 and terbium 14, 25, 26 derivatives display also the characteristic narrow bands of Sm3+, Eu3+ and Tb3+ ions.

Stereoselective thiirane desulfurization controlled by a bridging or terminal acyl ligand: Concerted vs. SN2 pathways

An acyl-bridged heterodinuclear Pt/Mn complex [(dppe)Pt(μ-C(O)Np-1κC,2κO)–Mn(CO)4] (Np = neopentyl, –CH2CMe3) has been prepared and unambiguously characterized. Upon reaction with thiiranes, this species is able to facilitate the direct desulfurization of three-membered S-heterocycles to produce olefins with complete retention of stereochemistry, with kinetic details supporting a concerted mechanism for thiirane desulfurization. Conversion of this species to a non-bridged, opened Pt/Mn complex [(dppe)(NpC(O))Pt–Mn(CO)5] can be effected by reaction with CO(g) in benzene solution. These non-bridged species display the opposite reactivity with thiiranes, generating the isomer with an inverted stereochemistry. Isolation of key thiamanganacyclic intermediates indicate that inversion occurs in the first C–S bond cleavage event, while the second desulfurization step proceeds with retention to produce the olefin. As a result, control of stereoselectivity in this process appears to be mediated by the existence or absence of forced Pt/Mn metal–metal proximity.

ZnIIBisterpyridine Metallopolymers: Improved Processability by the Introduction of Polymeric Side Chains

AbstractIntroducing well‐defined polymeric side chains to bisterpyridine coordination polymers enables the synthesis of materials with tailor‐made optical and mechanical properties. The polymers are introduced either by a copper‐catalyzed azide–alkyne cycloaddition (grafting‐onto) or an atom transfer radical polymerization (polymerization‐from) method. The resulting metallopolymers exhibit improved solubility in common organic solvents and can, therefore, be inkjet‐printed from chlorinated benzene solutions. The photophysical properties of the so‐produced homogeneous films are investigated and a proof‐of‐principle polymer light‐emitting device can be constructed. magnified image

Visible-Light-Induced Oxygenation of Benzene by the Triplet Excited State of 2,3-Dichloro-5,6-dicyano-p-benzoquinone

Photocatalytic oxygenation of benzene to phenol occurs under visible-light irradiation of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) in an oxygen-saturated acetonitrile solution of benzene and tert-butyl nitrite. The photocatalytic reaction is initiated by photoinduced electron transfer from benzene to the triplet excited state of DDQ.

Syntheses and Characterization of the Coordination Compounds of N-(2-hydroxymethylphenyl)-C-(3′-carboxy-2′-hydroxyphenyl)thiazolidin-4-one

A dry benzene solution of the Schiff base N-(2-hydroxymethylphenyl)-3′-carboxy-2′-hydroxybenzylideneimine upon reacting with mercaptoacetic acid undergoes cyclization and forms N-(2-hydroxymethylphenyl)-C-(3′-carboxy-2′-hydroxyphenyl)thiazolidin-4-one, LH3 (I). A MeOH solution of I reacts with Co(II), Ni(II), Cd(II), Zr(OH)2(IV), and UO2(VI) ions and forms the monomeric coordination compounds, [M(LH)(MeOH)3] [where M = Co(II), Ni(II)], [M′(LH)(MeOH)] [here M′ = Cd(II), UO2(VI)] and [Zr(OH)2(LH)(MeOH)]. The coordination compounds have been characterized on the bases of elemental analyses, molar conductance, molecular weight, spectral (IR, NMR, and reflectance) studies, and magnetic susceptibility measurements. I behaves as a dibasic tridentate OOS donor ligand in these compounds. The compounds are nonelectrolytes (ΛM = 3.8–8.9 mho cm2 mol−1) in DMF. A tetrahedral structure for [Cd(LH)(MeOH)] and an octahedral structure for the remaining compounds are suggested.

Bacillus drentensis sp. 사균과 polysulfone으로 이루어진 미생물담체를 이용한 수용액 내 벤젠 제거

Laboratory scale experiments to remove benzene in solution by using the bio-carrier composed of dead biomass have been performed. The immobilized bio-carrier with dead Bacillus drentensis sp. and polysulfone was manufactured as the biosorbent. Batch sorption experiments were performed with bio-carriers having various quantities of biomass and then, their removal efficiencies and uptake capacities were calculated. From results of batch experiments, 98.0% of the initial benzene (1 mg/L) in 1 liter of solution was removed by using 40 g of immobilized bio-carrier containing 5% biomass within 1 hour and the biosorption reaction reached in equilibrium within 2 hours. Benzene removal efficiency slightly increased (99.0 to 99.4% ± 0.05) as the temperature increased from 15 to 35 o C, suggesting that the temperature rarely affects on the removal efficiency of the bio-carrier. The removal efficiency changed under the different initial benzene concentration in solution and benzene removal efficiency of the bio-carrier increased with the increase of the initial benzene concentration (0.001 to 10 mg/L). More than 99.0% of benzene was removed from solution when the initial benzene concentration ranged from 1 to 10 mg/L. From results of fitting process for batch experimental data to Langmuir and Freundlich isotherms, the removal isotherms of benzene were more well fitted to Freundlich model (r 2 = 0.9242) rather than Langmuir model (r 2 = 0.7453). From the column experiment, the benzene removal efficiency maintained over 99.0% until 420 pore volumes of benzene solution (initial benzene concentration: 1 mg/L) were injected in the column packed with bio-carriers, investigating that the immobilized carrier containing Bacillus drentensis sp. and polysulfone is the outstanding biosorbent to remove benzene in solution.

Phenol Formation in Gamma Radiolysis of Aqueous Benzene Solution with Sodium Hypochlorite

Phenol formation by gamma radiolysis of an aqueous benzene solution containing sodium hypochlorite is reported. The phenol formation in a benzene solution containing sodium hypochlorite irradiated with (60)Co γ-rays is about six times higher than that without sodium hypochlorite. Ten micromolar sodium hypochlorite enhanced the formation of phenol up to a total dose of 6 Gy. Above 6 Gy in solutions containing sodium hypochlorite, the rate of phenol yield sharply decreased and was essentially the same as that without sodium hypochlorite. The yield of phenol with sodium hypochlorite is 0.89 μmol J(-1) and is larger than the sum of yield for the radicals and reactive oxygen species by water radiolysis such as •OH, e(-), H, H2, and H2O2. The formation of phenol with sodium hypochlorite was reduced by NaCl. Results suggest that the radiolytic formation of phenol in a benzene solution with sodium hypochlorite relates to the reaction process involving chlorine atoms. Sodium hypochlorite can be applied as a sensitizer for a benzene chemical dosimetry system. The lower limit of dose detection calculated from the detection limit of phenol and the G value of phenol was estimated to be 1 × 10(-3) Gy.

Multicomponents adsorption of modified cellulose microfibrils

Jute has been used as a raw material to chemically modified cellulose microfibres. For this purpose three chemical treatments were used: mercerization with NaOH, acetylating with nitric acid and acetic acid and finally hydrolysis with sulphuric acid. The isolated microfibrils were characterized by Fourier transform infrared spectroscopy (FTIR) and Technical Association of the Pulp and Paper Industry standards have been applied before and after chemical treatment to determine the composition of the cellulosic materials which was decreased considerably the lignin content from 17 to 1.7%. The microfibrils were treated with palmitic acid to graft a long hydrocarbon chain and able to retain organic molecules such as toluene or benzene in water. In this way, after elimination of water from the cellulose microfibrils by azeotropic distillation; palmitic acid, N-N’-Dicyclohexylcarbodiimide and 4-(Dimethylamino)pyridine catalyst were added to esterify cellulose microfibrils. Treated fibres were characterized by FTIR to follow the ester carbonyl formation peak and contact angle measurements to determine the decrease in the hydrophilic character of the initial untreated fibres. The adsorption capacity of these microfibrils has been studied using various solutions of different organic components, benzene or toluene, and then, we have studied the retention capacity in a multicomponent solution, i.e. with two organic components in the same solution.

Synthesis of Silica-Coated Uranium Oxide Nanoparticles by Surfactant-Templated Sol-Gel Process for Use as Catalysts

Uranium oxide (U3O8) nanoparticles were synthesized and coated in situ with porous, mesostructured silica using a modified sol-gel method for use as a catalyst. The catalytic property of coated U3O8 nanoparticles was evaluated by exposing them to an aqueous solution of benzene at 500 mg/l at room temperature. The presence of benzene was not detected by an ultraviolet (UV)-visible (UV-vis) spectrometer after 6 weeks of exposure to coated uranium oxide nanoparticles, indicating the particles’ potential as a catalyst. Based on the results of the benzene destruction, it may be suggested that the coated U3O8 nanoparticle-based catalyst has the potential to destroy hydrocarbons, aromatics, and various toxic substances such as perchlorates and 1,4-dioxane from groundwater. However, further experiments are necessary to explore the full potential of the catalyst. Pluronic-123, n-butanol, and 2-propanol were used as surfactant, cosurfactant, and continuous phase, respectively, for the synthesis of the U3O8 nanoparticles, which were formed through nucleation, growth, and subsequent aggregation in the solution phase. The nanoparticles were coated in situ using an aqueous solution of tetraethyl orthosilicate. The coated particles were characterized using transmission electron microscopy, diffuse reflectance infrared Fourier transform spectroscopy, nitrogen physisorption, X-ray diffraction, and diffuse reflectance UV-vis spectroscopy. These measurements revealed that U3O8 particles ranging from 4- to 10-nm were distributed exclusively inside the silica matrix.

Synthesis, structure, and catalytic activity of benzyl thorium metallocenes

Treatment of the chloride metallocene [η5-1,3-(Me3C)2C5H3]2ThCl2 or [η5-1,2,4-(Me3C)3C5H2]2ThCl2 with 2 equiv of PhCH2K in diethyl ether at room temperature gives, after recrystallization from a benzene solution, the benzyl metallocenes [η5-1,3-(Me3C)2C5H3]2Th(CH2Ph)2 (1) and [η5-1,2,4-(Me3C)3C5H2]2Th(CH2Ph)2 (2), respectively, in good yields. Complexes 1 and 2 have been characterized by various spectroscopic techniques, elemental analyses, and X-ray diffraction analyses. They are active catalysts for the polymerization of rac-lactide, leading to the atactic polylactides with high molecular weights and narrow molecular weight distributions.

Antioxidant Efficiency of Oxovitisin, a New Class of Red Wine Pyranoanthocyanins, Revealed through Quantum Mechanical Investigations

Oxovitisin is a natural antioxidant present in aged wine and comes from the chemical transformation undergone by anthocyanins and pyranoanthocyanins. Its antioxidant radical scavenging capacity was theoretically explored by density functional theory (DFT)/B3LYP methods. The O-H bond dissociation energy (BDE), the ionization potential (IP), the proton affinity (PA), and the metal-oxovitisin binding energy (BE) parameters were computed in the gas-phase and in water and benzene solutions. Results provided molecular insight into factors that influence radical scavenging potential of this new class of anthocyanins.

Spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene and their resistance to protolytic dissociation and photochemical destruction

The spectral and photophysical properties of zinc(II) complexes with alkylsubstituted derivatives of dipyrrolylmethene, along with the kinetics of their protolytic dissociation and photochemical degradation in organic solvents of different natures, are studied by means of electronic absorption and fluorescence spec� troscopy. It is found that protic solvents have the strongest effect on absorption spectra, while electron donors affect fluorescence spectra due to differences in the mechanisms of solvation for the ground and excited states of molecules. It is shown that the reaction product of the protolytic dissociation of complexes in benzene solutions of acetic acid is a protonated form of ligand. The observable and genuine rate constants of dissoci� ation reactions are determined and activation parameters are calculated. A kinetic model of the process is proposed, and the regularities of the effect the nature of ligand has on the kinetics of dissociation are estab� lished. The photochemical degradation of compounds proceeds on monopyrrole products, the photolysis rate falls as the a degree of alkylation increases, and the nature of the substituent in the β�position of the ligand's pyrrole ring has a greater effect on the stability of a compound.

Morphology and Capacitance Properties of Nanostructured Composites of Carbon Nanostructures and C60-Pd Nanoparticles

The composites of C60-Pd polymer and carbon nanostructures, single walled carbon nanotubes (SWCNTs), multi walled carbon nanotubes (MWCNTs), and graphene, were synthesized chemically in benzene solution containing zero-valent Pd complex, C60, and carbon nanostructure. Two kinds of morphologies are observed on the surface of carbon nanoparticles during polymer deposition. Initially, a thin layer of 5 nm C60-Pd polymeric nanoparticles is formed. Next, these particles aggregate into bigger spherical structures ca. 150 nm in diameter. The capacitance performance of synthetized materials was investigated. Specific capacitances per mass of the polymer in the composite are significantly higher in comparison to pure chemically formed polymeric material. This effect is related to the nanostructured morphology of composite resulting in the higher efficiency of charge accumulation.

Stability and structural phase transitions of cobalt porphyrin adlayers on Au(100) surfaces

The stability and phase transitions of adlayers of two cobalt(II) porphyrins, 5,10,15,20-tetraphenyl-21H,23H-porphine cobalt(II) (CoTPP) and 2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphine cobalt(II) (CoOEP), formed on Au(100) were investigated under electrochemical conditions. In situ scanning tunneling microscopy (STM) was employed to investigate the structure of CoTPP and CoOEP adlayers in 0.1 M HClO4. The CoTPP and CoOEP adlayer structures were varied with the modification time and the concentration. The in situ STM observations showed that the underlying reconstructed atomic structure was lifted to a (1 × 1) atomic arrangement by either the adsorption of CoTPP/CoOEP during modification in a benzene solution or positive potential manipulation in 0.1 M HClO4. Ordered CoTPP arrays with two different hexagonal and square packing arrangements were found on an Au(100)-(1 × 1) surface, along with characteristic Au islands. The CoOEP molecules also formed a close-packed hexagonal structure on an Au(100)-(hex) surface; CoOEP molecules were arranged in a semi-square structure on the Au(100)-(1 × 1) surface by the lifting of reconstruction. The results of this study showed that the interaction between the cobalt porphyrins and the Au(100) substrate depended on the modification conditions and the electrochemical potential.

Thermal decomposition of solid azobisisobutyronitrile

The rate of the thermal decomposition of solid azobisisobutyronitrile was measured under conditions such that the side processes, such as gas-phase decomposition, the formation of liquid products, crystal cracking, and polymorphic transitions, had no effect on the process rate. The reaction occurs on the inner crystal surface, and its rate depends on the method of crystallization. The sample crystallized under conditions of low supersaturation is the most stable. The kinetic parameters of the reaction are E = 134.9 ± 3.5 kJ/mol and log A = 14.12 ± 1.5 [s−1]. The decomposition rate constant of solid azobisisobutyronitrile is 50 times lower than that of azobisisobutyronitrile in benzene solution. The low reaction rate in the solid phase is explained in terms of the additional-volume model proposed for unimolecular reactions in molecular crystals.