Prediction and characterization of halogen–hydride interaction in Cu n H n ···ClC2Z and Cu n H···ClC2Z complexes (n = 2–5; Z = H, F, CH3)

Halogen–hydride interactions between the lowest energy structure of Cu _n H _n and Cu _n H clusters (n = 2–5) as halogen acceptor and ClC₂Z (Z = H, F, CH₃) as halogen donor have been investigated at the MP2/6-311++G(d,p) level of theory. Different approaches based on structural parameters, energetic analysis, shift in vibrational frequencies, and molecular electrostatic potential were used to characterize the resultant halogen–hydride bonds. Upon complexation, the Cl–C bonds tend to elongate, concomitant with red shifts of the Cl–C vibrational frequencies. Interaction energies of this type of halogen bonds vary from ?2.34 to a maximum ?7.38 kJ mol^?1. The calculated interaction energies were found to be increased in magnitude with increasing of the negative electrostatic potential at a point on the outer side of hydrogen atom of halogen acceptor units. Moreover, decomposition of the interaction energies reveals that the electrostatic interaction plays a main role in the formation of the complexes. The quantum theory of atoms in molecules analysis has also been applied to provide more insight into the nature and properties of these interactions. Our results indicate pure closed-shell interactions in these systems with similar characteristics to the conventional halogen bonds.     

Cerium(IV) triflate-catalyzed domino annulation approaches to the synthesis of highly substituted piperidines

A simple, diastereoselective, inexpensive, and efficient route for the synthesis of highly functionalized piperidines by the condensation of β-keto-esters, aromatic aldehydes and anilines using cerium(IV) triflate as a catalyst is described. In most cases, the piperidine precipitates out of the solution.     

Effect of Ni loadings on the activity and coke formation of MgO-modified Ni/Al_2O_3 nanocatalyst in dry reforming of methane

MgO-modified Ni/Al2O3 catalysts with different Ni loadings were prepared and employed in dry reforming of methane （DRM）. The effect of Ni loadings on the activity and coke formation of Ni/MgO-A1203 catalysts were investigated. The synthesized catalysts were characterized by XRD, N2 adsorption-desorption, SEM, TPO and TPR techniques. The obtained results showed that increasing nickel loading decreased the BET surface area and increased the catalytic activity and amount of deposited carbon. In addition, the effect of gas hourly space velocity （GHSV） and feed ratio were studied.     

Development of Voltammetric Sensor for Determination of Tryptophan Using MWCNTs‐modified Sol‐gel Electrode

In the present work, an electrochemical sensor was developed for simple and sensitive determination of tryptophan (Trp) using multi‐walled carbon nanotubes modified sol‐gel electrode (MWCNTs/SGE). The electrocatalytic oxidation of tryptophan was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the oxidation peak current of Trp at the MWCNTs/SGE was greatly improved compared with that of the bare SGE. Furthermore, at the MWCNTs/SGE, the anodic peak potential of Trp is shifted about 220 mV to more negative value indicated that modified electrode has better electrocatalytic activity for electro‐oxidation of Trp. The anodic peak currents increased linearly with the concentration of tryptophan in the range of 0.2 × 10^?6 to 15 × 10^?6 M with a detection limit of 0.139 × 10^?6 M (at an S/N = 3).     

Synthesis of Isoindolo[2,1‐a]quinazoline‐5,11‐dione Derivatives via the Reductive One‐Pot Reaction of N‐Substituted 2‐Nitrobenzamides and 2‐Formylbenzoic Acids

Various isoindolo[2,1‐a]quinazoline‐5,11‐dione derivatives 3 were synthesized in good yields by means of the reductive reaction of N‐substituted 2‐nitrobenzamides 1 and 2‐formylbenzoic acids 2 in the presence of SnCl₂?2 H₂O under reflux in EtOH (Scheme, Table). The procedure needed two steps, the reduction of the nitro group of the 2‐nitrobenzamide and ring closure by nucleophilic addition of the NH₂ group to both the formyl and carboxylic acid C?O groups.     

Numerical solution of nonlinear partial quadratic integro‐differential equations of fractional order via hybrid of block‐pulse and parabolic functions

In this paper, an effective numerical approach based on a new two‐dimensional hybrid of parabolic and block‐pulse functions (2D‐PBPFs) is presented for solving nonlinear partial quadratic integro‐differential equations of fractional order. Our approach is based on 2D‐PBPFs operational matrix method together with the fractional integral operator, described in the Riemann–Liouville sense. The main characteristic behind this approach is to reduce such problems to those of solving systems of algebraic equations, which greatly simplifies the problem. By using Newton's iterative method, this system is solved, and the solution of fractional nonlinear partial quadratic integro‐differential equations is achieved. Convergence analysis and an error estimate associated with the proposed method is obtained, and it is proved that the numerical convergence order of the suggested numerical method is O(h³) . The validity and applicability of the method are demonstrated by solving three numerical examples. Numerical examples are presented in the form of tables and graphs to make comparisons with the exact solutions much easier.     

Kinetic-catalytic determination of vanadium(IV) using methyl orange-bromate redox reaction.

Determination of V(IV) based on its catalytic effect on the reaction between Methyl Orange and bromate in thepresence of citric acid was studied. The calibration curve obtained by fixed-time method was linear in the range of 2.5-300 ng ml(-1). By use of slope method, a calibration curve containing two linear portions were obtained. Using fixed-time and slope methods, we obtained detection limits of 0.8 and 1.5 ng ml(-1), respectively. Fe2+, As(III), V(V) and Hg2+ interfered. The method was successful for analysis of water samples.     

A Novel Electrochemiluminesence Sensor Based on Silver Prussian Blue Analogue/Carboxylated Sulfur-doped Graphitic Carbon Nitride Nanocomposite for Determination of Lamotrigine

In this study, for the first time an electrochemiluminescence sensor for ultra-trace monitoring of lamotrigine is reported. The sensing probe was fabricated using silver prussian blue analogue as a new effective co-reaction accelerator and carboxylated sulfur-doped graphitic carbon nitride nanocomposite as a new green luminophore. Also potassium peroxydisulfate was utilized as a strong co-reactant. The proposed ECL sensor exhibited excellent wide linear range (3.45×10⁻¹⁵ to 2.98×10⁻⁸ M), low detection limit (4.89×10⁻¹⁶ M), the relative standard deviation of 1.07 %, outstanding reproducibility and superior long-term stability. The prominent advantages of the sensor showed that it can be used to determine LMT in clinical samples.     

Application of a new nanoporous sorbent for extraction and pre-concentration of lead and copper ions

The authors describe a method for the trace determination of copper (II) and lead (II) in water and fish samples using solid-phase extraction via siliceous mesocellular foam functionalised by dithizone. Siliceous mesocellular was functionalised with dithizone, and the resulting sorbent was characterised by scanning electron microscopy, surface area analysis, thermogravimetric/differential thermal analysis and FTIR. Following solid-phase extraction of target ions by the sorbent, copper and lead ions were quantified by flame atomic absorption spectrometry. Factors affecting the sorption and desorption of target ions by the sorbent were evaluated and optimised. The calibration plot is linear in the 1 – 500 μg L^?1 copper (II) and 3–700 μg L^?1 lead (II) concentration range. The relative recovery efficiency in real sample analysis is in the range from 96 to 102%, and precision varies between 1.7 and 2.8%. It is should be noted that the limits of detection for the copper and lead analysis were 0.8 and 1.6 μg L^?1, respectively. Also, the adsorption capacities for copper and lead ions were 120 and 160 mg g^?1, respectively. The obtained pre-concentration factor for the lead and copper ions by the proposed solid-phase extraction was 75. The method was successfully applied to the determination of low levels of copper (II) and lead (II) in tap, Caspian sea, Persian gulf and lake water and also their detection in fish samples.