Synthesis of new dyes containing double tetrazole groups for sensitization of TiO<Subscript>2</Subscript> nanoparticles in dye-sensitized solar cells

Di(1H-tetrazol-5-yl)methane is employed as a new electron acceptor group in the synthesis of two metal-free organic dyes containing triphenylamine donor group. Dye-sensitized nanocrystalline TiO₂ solar cell (DSSC) applying these novel dyes is constructed for consideration of their photovoltaic properties. The electronic properties of the dyes are also considered with the aid of theoretical calculations. The DSSC constructed from 4-(2,2-di(1H-tetrazol-5-yl)vinyl)-N,N-diphenylaniline (T1) shows a short-circuit photocurrent density of 13.38 mA cm^?2, an open circuit voltage of 578 mV, and a fill factor of 0.54, with a resulted solar energy-to-electricity conversion efficiency of 4.18% under simulated 1 sun irradiation (100 mW cm^?2). This result reveals that the dye with the di(1H-tetrazol-5-yl)methane anchoring group injects more electrons to the conduction band of TiO₂ in comparison with its analogs with single tetrazole ring in their anchoring group. It is found that in spite of a red-shift of the absorption spectrum resulted from the lengthening of the molecule, the dye with two di(1H-tetrazol-5-yl)methane groups gives lower performance than the dye with a single electron acceptor.     

A new scheme for solving nonlinear Stratonovich Volterra integral equations via Bernoulli’s approximation

In this paper, an efficient method for solving nonlinear Stratonovich Volterra integral equations is proposed. By using Bernoulli polynomials and their stochastic operational matrix of integration, these equations can be reduced to the system of nonlinear algebraic equations with unknown Bernoulli coefficient which can be solved by numerical methods such as Newton’s method. Also, an error analysis is valid under fairly restrictive conditions. Furthermore, in order to show the accuracy and reliability of the proposed method, the new approach is compared with the block pulse functions method by some examples. The obtained results reveal that the proposed method is more accurate and efficient than the block pulse functions method.     

Simple and efficient one-pot synthesis of N-phenyl-3,5-difunctionalized pyrazoles

A facile one-pot synthesis of N-phenyl-3,5-difunctionalized pyrazoles is described. The dialkyl 2-[(Z)-phenylhydrazono]succinate intermediate, which is prepared in situ from the mixture of phenylhydrazine and dialkyl acetylenedicarboxylate reacts with aroyl chloride or fumaryl chloride to afford the title compounds. Different types of compounds containing COCl functional group were used to investigate the scope and limitation of the reaction. Two -CO₂R and -O₂C groups at 3- and 5-position are potentially capable to convert to other functional groups. The reaction conditions are relatively mild and the yields are good.     

Synthesis and spectral characterization of mercury(II) complexes with the bidentate Schiff base ligand N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane: The crystal structures of [Hg((23-MeO-ba)2en)I2] and [Hg((23-MeO-ba)2en)Br2]

Three mercury(II) complexes, [Hg((23-MeO-ba)₂en)X₂] (X = I (1), Br (2) and Cl(3)), and the ligand (23-MeO-ba)₂en ((23-MeO-ba)₂en = N,N′-bis(2,3-dimethoxybenzylidene)-1,2-diaminoethane) have been synthesized and characterized by elemental analyses, FT-IR and ¹H NMR spectroscopy. The crystal and molecular structures of 1 and 2 were determined by X-ray crystallography from single-crystal data. The metal-to-ligand ratio was found to be 1:1. The mercury(II) center in 1 and 2 has a distorted tetrahedral geometry with HgN₂I₂ and HgN₂Br₂ chromophores, respectively. The Schiff base ligand (23-MeO-ba)₂en acts as a chelating ligand, coordinating via the two nitrogen atoms to the mercury(II) center, and it adopts an E,E conformation. The coordination sphere of the mercury(II) center in 1 and 2 is completed by the two I and Br atoms, respectively. In complex 1 an inter-molecular non-classical hydrogen bond of the type C-H?O was found, while in complex 2 inter- and intra-molecular non-classical hydrogen bonds of the type C-H?X (X = O and Br) were found. The ¹H NMR spectra of the complexes exhibit downfield as well as upfield shifts of the free ligand resonances, reflecting changes in the ligand’s geometry during its coordination.     

Theoretical Study of 13C Chemical Shifts Structures of Some ortho-Substituted 3-Anilino-2-nitrobenzo[b]thiophenes and 2-Anilino-3-nitrobenzo[b]thiophenes and Comparison with Experimental

¹³C NMR chemical shifts have been calculated for structures of some substituted 3‐anilino‐2‐nitrobenzo‐[b]thiophenes ( 2 o) and 2‐anilino‐3‐nitrobenzo[b]thiophenes ( 3 o) derivatives containing OH, NH₂, OMe, Me, Et, H, F, Cl and Br. The molecular structures were fully optimized using B3LYP/6‐31G(d,p). The calculation of the ¹³C shielding tensors employed the GAUSSIAN 03 implementation of the gauge‐including atomic orbital (GIAO) and continuous set of gauge transformations (CSGT) by using 6‐311++G(d,p) basis set at density functional levels of theories (DFT). The isotropic and the anisotropy parameters of chemical shielding for all compounds are calculated. The predicted ¹³C chemical shifts are derived from equation δ=δ₀+δ where δ is the chemical shift, δ is the absolute shielding, and δ₀ is the absolute shielding of the standard TMS. Excellent linear relationships have been observed between experimental and calculated ¹³C NMR chemical shifts for all derivatives     

The Reaction of (N‐Isocyanimino)triphenylphosphorane with Biacetyl in the Presence of Aromatic Carboxylic Acids: Efficient One‐Pot Three‐Component Reaction for the Synthesis of 3‐(5‐Aryl‐1,3,4‐oxadiazol‐2‐yl)‐3‐hydroxybutan‐2‐one Derivatives

Reactions of biacetyl (=butane‐2,3‐dione) with (N‐isocyanimino)triphenylphosphorane in the presence of aromatic carboxylic acids proceed smoothly at room temperature and under neutral conditions to afford 3‐(5‐aryl‐1,3,4‐oxadiazol‐2‐yl)‐3‐hydroxybutan‐2‐one derivatives in high yields.     

A helix-forming αβγ-chimeric peptide with catalytic activity: a hybrid peptide ligase

We describe the catalytic activity of the first chimeric ligase containing a foldameric sequence of β- and γ-amino acids. The chimeric backbone provides for the spatial arrangement of all functional groups involved in the formation of the catalytic site to allow efficient catalysis to take place. Our finding indicates significant progress in the field of functionally active artificial motifs.     

Infrared spectrum of the CS2 trimer: observation of a structure with D3 symmetry

Infrared spectra of a carbon disulfide trimer formed in a pulsed supersonic slit-jet expansion are obtained via direct absorption of a tuneable diode laser in the region of the CS(2)ν(3) fundamental (～1535 cm(-1)). This is the first high-resolution spectroscopic observation of (CS(2))(3). Two bands sharing the same lower state are assigned to ((12)C(32)S(2))(3). These correspond to the two infrared active trimer vibrations (a parallel and a perpendicular band) of the constituent CS(2) monomer asymmetric stretches. The weaker perpendicular band is centered at 1524.613 cm(-1), shifted by -10.74 cm(-1) with respect to the free CS(2) monomer. The parallel band is centered at 1545.669 cm(-1), a vibrational shift of +10.31 cm(-1). Transitions with K≠ 3n and those with K = 0, J = odd in the ground state are absent, establishing that this trimer has D(3) symmetry. The two parameters required to define this structure are determined to be 3.811 ? for the C-C bond distance and 61.8° for the angle between a monomer axis and the plane containing the C atoms. In addition, a parallel band arising from trimers with a single (34)S substitution is observed around 1544.46 cm(-1). Together with the recently observed cross-shaped CS(2) dimer, these results indicate a tendency for CS(2) to form highly symmetric clusters.     

The Effect of Reservoir Wettability on the Production Characteristics of the VAPEX Process: An Experimental Study

The impact of fractional wettability on the production characteristics of a VAPEX process at the macroscale was investigated. Conventional VAPEX experiments were conducted in a 220 Darcy random packing of glass beads in a rectangular physical model and n-pentane was used to recover the Cold Lake bitumen from the oil-saturated model in the absence of connate water. The composition of oil-wet beads in the packed bed was altered from completely water-wet beads to completely oil-wet beads at different proportions of oil-wet beads mixed with water-wet beads. A substantial increase (about 40%) in the production rate of live oil was observed during the VAPEX process when the wettability of the porous packing was entirely oil-wet beads. A critical oil-wet fraction of 0.66 was found for the heterogeneous packing of water-wet and oil-wet beads of similar size distribution. Above this critical composition, the live oil production rate was not affected by further increase in the proportion of the oil-wet beads. It is believed that above this critical composition of the oil-wet beads, the crevice flow process is dominated by the continuity of higher conductivity live oil films between particles through the oil-wet regions. Below this critical composition, the live oil production rate increased linearly with the fraction of the oil-wet beads in the packing. The oil-wet regions favor the live oil drainage compared to that of the water-wet regions as they enhance the rate of imbibition of the live oil from the oil-filled pores to the vacated pores near the nominal VAPEX interface. These two factors enhance the live oil production rate during the VAPEX process. The solvent content of the live oil, the solvent-to-oil ratio (SOR), and the residual oil saturation did not correlate strongly with the proportion of the oil-wet beads in the packing. The average solvent content of the live oil and the residual oil saturation were measured to be 48% by weight and 7% by volume respectively.     

A numerical approach for solving weakly singular partial integro‐differential equations via two‐dimensional‐orthonormal Bernstein polynomials with the convergence analysis

In this paper, we develop an efficient matrix method based on two‐dimensional orthonormal Bernstein polynomials (2D‐OBPs) to provide approximate solution of linear and nonlinear weakly singular partial integro‐differential equations (PIDEs). First, we approximate all functions involved in the considerable problem via 2D‐OBPs. Then, by using the operational matrices of integration, differentiation, and product, the solution of Volterra singular PIDEs is transformed to the solution of a linear or nonlinear system of algebraic equations which can be solved via some suitable numerical methods. With a small number of bases, we can find a reasonable approximate solution. Moreover, we establish some useful theorems for discussing convergence analysis and obtaining an error estimate associated with the proposed method. Finally, we solve some illustrative examples by employing the presented method to show the validity, efficiency, high accuracy, and applicability of the proposed technique.