FTIR spectroscopic and quantum-chemical studies on some tribromoindenes and their isomers

Combined experimental and computational studies on molecular structure of newly synthesised transtirans 1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (TTTBI) were reported. Also, only computational studies were done for cis-trans-1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (CTTBI) and cis-cis-1,2,3-tribromo-1,2,3-trihydro-¹H-benz[f]indene (CCTBI) in order to understand the vibrational spectra and molecular parameters of them. The geometry optimization and vibrational wave numbers of the title molecules were carried out with the Gaussian98 program package by using Hartree-Fock (HF) and Density Functional Theory (DFT) with B3LYP functional and 6–31G (d) basis set. All calculations were done for the title compounds in their ground states. Especially for CTTBI and CCTBI, which could not be synthesized yet, these kind of pre-calculations take an important role for their synthesis process. Also crystal structural parameters of TTTBI by single-crystal X-ray diffraction method was used as input for computational study of it. Observed and calculated vibrational wave numbers were compared. Because the use of benz[f]indene as a cyclopentadienyl ligand attracted much attention because an annulated benzo ring might increase both the stereocontrol and productivity of catalytic system, TTTBI and other computationally studied and modeled two molecules may play an important role of other types of compounds as a starting structures.     

A facile and one pot synthesis of 1,4-disubstituted-1H-1,2,3-triazoles from terminal alkynes and phenacyl azides prepared from styrenes by CAN oxidant and sodium azide

A facile and green synthesis of 1,4-disubstituted-1H-1,2,3-triazoles is reported. The reaction of α-azido ketones and terminal alkynes in the presence of [CuSO₄ (H₂O)₅/sodium ascorbate] in a mixture of H₂O/polyethylene glycol 400 as solvent afforded the corresponding 1,4-disubstituted triazoles at ambient temperature with short reaction times and at high yields. The corresponding α-azido ketones were directly prepared in situ from various substituted styrenes using the oxidant cerium ammonium nitrate and sodium azide in oxygen-saturated methanol.     

High pressure assisted 1,3-dipolar cycloadditions: Synthesis of silylated triazoles from heteroaryl azides

Abstract

The 1,3-dipolar cycloaddition of 2- and 3-benzothiopheneazide with (trimethyl-sily1)acetylene to yield 1,2,3-triazoles has been studied at pressures up to 1GPa. The kinetics as a function of pressure was followed interfacing a diamond anvil cell to a FTIR spectrometer. Alike with aryl azides, the rate of reaction was found to increase logarithmically with pressure with a yield close to quantitative.     

Interaction mechanism between copolymer inhibitor and β-dicalcium silicate surface based on molecular dynamics simulation

Copolymer inhibitor with multifunctional groups has a good effect on inhibiting the secondary reaction in the clinker leaching process for alumina production, but the inhibition mechanism of the copolymer is not clear yet. In this paper, molecular dynamics simulation was used to study the adsorption process of the copolymer inhibitor with multifunctional groups, such as acrylic acid-vinyl alcohol copolymer (PAV) and acrylic acid-hydroxypropyl acrylate copolymer (PAH), on the β-dicalcium silicate (C₂S) crystal surface, and reveal its inhibiting mechanism. Meanwhile, the polyacrylic acid (PAA) with only the carboxyl group also is simulated for comparing the inhibition effect with copolymer inhibitors. The results show that the binding energy between copolymer (PAV, PAH) and β-C₂S is greater than that of PAA with a single functional group. The order of binding energy is as follows: PAH?>?PAV?>?PAA. In aqueous solution, the water molecule can restrict the degree of deformation of polymers, increase the distance between polymers and β-C₂S and then lead to weakening of the adsorption of polymers on the crystal surface. The comprehensive and coordination effect of carboxyl and hydroxyl functional groups in PAV and PAH can strengthen the adsorption of copolymers on the β-C₂S surface. The different spatial distribution of multifunctional groups in the molecular structure has a different influence on the adsorption of the copolymer. The results can provide a theoretical basis for researching new and highly effective copolymer inhibitors with multifunctional groups.

Compared the adsorption state: The comprehensive and coordinate action of carboxyl and hydroxyl groups of the inhibitor with multifunctional groups make the inhibitor have a stronger adsorption ability on the surface of β-C₂S than that with a single functional group. The results obtained in this paper can provide a theoretical basis for the research and development of new and highly effective polymeric inhibitors with multifunctional groups.

Highlights

The interaction between copolymer and β-C₂S was investigated by MD simulation.

The binding energy order between polymers and β-C₂S is PAH?>?PAV?>?PAA.

The presence of water molecules can weaken the adsorption of the copolymer on the surface of β-C₂S.

The comprehensive and coordinate action of carboxyl and hydroxyl groups of the inhibitor with multifunctional groups make the inhibitor have a stronger adsorption ability on the surface of β-C₂S than that with a single functional group.     

α-Azido ketones. Part 7: synthesis of 1,4-disubstituted triazoles by the “click” reaction of various terminal acetylenes with phenacyl azides or α-azidobenzo(hetera)cyclanones

Copper(I)-catalyzed alkyne-azide 1,3-cycloaddition reaction (CuAAC, Sharpless–Meldal reaction) of various α-azido ketones such as substituted 2-azidoacetophenones, 2-azidobenzosuberone and 3-azido(thio)chromanones with terminal alkynes was studied. The reaction resulted in the formation of the expected 1,2,3-triazoles in moderate to good yields although the reactivity was somewhat lower than in the case of simple azides. Reaction of ethynylchromones as alkynes gave interesting dichromonoid systems bridged by a triazole unit.     

Structure and elastic properties of a nematic liquid crystal: A theoretical treatment and molecular dynamics simulation

The Frank elasticity constants which describe splay (K ₁), twist (K ₂), and bend (K ₃) distortion modes are investigated for 4-n-pentyl-4'-cyanobiphenyl (5CB) in the nematic liquid crystal. The calculations rest on statistical-mechanical approaches where the absolute values of K _i (i=1,2,3) are dependent on the direct correlation function (DCF) of the corresponding nematic state. The DCF was determined using the pair correlation function by solving the Ornstein-Zernike equation. The pair correlation function, in turn, was obtained from molecular dynamics (MD) trajectory. Three different approaches for calculations of the elasticity constants were employed based on different level of approximation about the orientational order and molecular correlations. The best agreement with experimental values of elasticity constants was obtained in a model where the full orientational distribution function was used. In addition we have investigated the approximation about spherical distribution of the intermolecular vectors in the nematic phase, often used in derivation of various mean-field theories and employed here for the construction of the DCF. We found that this assumption is not strictly valid, in particular a strong deviation from the isotropic distribution is observed for short intermolecular distances. Received 22 March 2000 and Received in final form 9 June 2000     

Theoretical study on interaction of cytochrome f and plastocyanin complex by a simple coarse-grained model with molecular crowding effect

ABSTRACT

We present a simple coarse-grained model with the molecular crowding effect in solvent to investigate the structure and dynamics of protein complexes including association and/or dissociation processes and investigate some physical properties such as the structure and the reaction rate from the viewpoint of the hydrophobic intermolecular interactions of protein complex. In the present coarse-grained model, a function depending upon the density of hydrophobic amino acid residues in a binding area of the complex is introduced, and the function involves the molecular crowding effect for the intermolecular interactions of hydrophobic amino acid residues between proteins. We propose a hydrophobic intermolecular potential energy between proteins by using the density-dependent function. The present coarse-grained model is applied to the complex of cytochrome f and plastocyanin by using the Langevin dynamics simulation to investigate some physical properties such as the complex structure, the electron transfer reaction rate constant from plastocyanin to cytochrome f and so on. We find that for proceeding the electron transfer reaction, the distance between metals in their active sites is necessary within about 18 Å. We discuss some typical complex structures formed in the present simulation in relation to the molecular crowding effect on hydrophobic interactions.     

Double exponential transformation for computing three-center nuclear attraction integrals

ABSTRACT

Three-center nuclear attraction integrals, which arise in density functional and ab initio calculations, are one of the most time-consuming computations involved in molecular electronic structure calculations. Even for relatively small systems, millions of these laborious calculations need to be executed. Highly efficient and accurate methods for evaluating molecular integrals are therefore all the more vital in order to perform the calculations necessary for large systems. When using a basis set of B functions, an analytical expression for the three-center nuclear attraction integrals can be derived via the Fourier transform method. However, due to the presence of the highly oscillatory semi-infinite spherical Bessel integral, the analytical expression still remains problematic. By applying the S transformation, the spherical Bessel integral can be converted into a much more favorable sine integral. In the present work, we then apply two types of double exponential transformations to the resulting sine integral, which leads to a highly efficient and accurate quadrature formula. This method facilitates the approximation of the molecular integrals to a high predetermined accuracy, while still keeping the calculation times low. The fast convergence properties analyzed in the numerical section illustrate the advantages of the method.     

Effect of longitudinal heat conduction on the catalytic ignition of carbon monoxide in a boundary layer

The catalytic ignition of dry carbon monoxide and air in a boundary layer flow over a palladium plate is studied in this paper. The heterogeneous reaction mechanism is modelled with the dissociative adsorption of the molecular oxygen and the non-dissociative adsorption of CO, together with a surface reaction of the Langmuir-Hinshelwood type and the desorption reaction of the adsorbed product, CO₂(s). The critical condition for catalytic ignition, represented by the ignition Damköhler number, has been deduced using high activation energy asymptotics of the desorption kinetics of the most efficiently adsorbed reactant, CO(s). Longitudinal heat conduction along the plate has been considered and its influence on the ignition temperature has been evaluated. This influence is rather weak, indicating that the flat plate boundary layer flow configuration is a robust device to determine the critical conditions for catalytic ignition.     

Initial vibrational energy distributions determined by infra-red chemiluminescence

The reaction of atomic hydrogen with molecular fluorine produces vibrationally excited hydrogen fluoride with v′ ? 8>. Maximum population is achieved in v′ = 6. It is estimated that 58 per cent of the available energy of reaction is initially present as HF _v′→0 ^?.

Trajectory calculations have been made using various types of modified London-Eyring-Polanyi-Sato (LEPS) surfaces to obtain the vibrational energy level distributions for comparison with experimental results. A general conclusion is that in all cases, the predicted distribution is too narrow. No one surface could simultaneously give an entirely satisfactory prediction of the product vibrational energy distribution, activation energy with related rate constant and reaction enthalpy. It is concluded that a systematic method of selection of the value for D_e ³ for the first ³Σ state will be necessary if a surface is to be transferred between related reactions. A ‘best’ surface is selected and shown to be compatible with the known activation energy and rate constant values for this reaction.     

Acid‐base properties and supramolecular structure of N‐[(hydroxymethyl)triazolyl]triflamides: DFT,ab initio,and FTIR study

For N‐{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}triflamide 1 , N‐{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}‐N‐phenyltriflamide 2 , and N,N‐bis{[2‐(hydroxymethyl)‐2H‐1,2,3‐triazolyl‐4‐yl]methyl}triflamide 3 , the proton affinities of the triazole nitrogen atoms and the hydroxy and sulfonyl oxygen atoms as well as the energies of formation of the conformers with intramolecular H‐bonds and dimers with intermolecular NH?N, OH?N, OH?O═S, and NH?O═S H‐bonds were calculated by density functional theory and second‐order Møller‐Plesset perturbation methods. Quantum Theory of Atoms in Molecules analysis was performed to investigate the nature of H‐bonds. According to Fourier transform infrared spectroscopy, in CH₂Cl₂ solution, the monomeric molecules of 1 to 3 exist in the equilibrium with cyclic dimers having the OH?N hydrogen bonds.     

Theoretical analysis of the astrophysical S-factor for the capture reaction α + d → 6Li + γ in the two-body model

Theoretical estimates for the astrophysical S-factor and the rate of the reaction d(α, γ)⁶Li were obtained on the basis of the two-body model involving an α−d potential that has a simple Gaussian form and which describes correctly S-, P-, and D-wave phase shifts, the binding energy, and the asymptotic normalization coefficient for the S-wave bound state. The wave functions for the bound and continuum channels were calculated with the aid of the highly precise Numerov algorithm. The results for the contributions of the E1 and E2 transition components reveal a good convergence as the upper limit in the effective integrals increases up to 40 fm. The results obtained for the astrophysical S-factor and the rate of the reaction d(α, γ)⁶Li in the temperature range of 10⁶ K ≤ T ≤ 10¹⁰ K agree well with the results of the calculations performed by A.M. Mukhamedzhanov and his coauthors [Phys. Rev. C 83, 055805 (2011)] by using the known asymptotic form of the wave function at low energies and a complicated two-body potential at higher energies.

     

Electron paramagnetic relaxation in aqueous solutions of manganese (II) ions

The processes of the electron paramagnetic relaxation, molecular motions and structural changes in aqueous solutions of manganese nitrate have been investigated by direct measurement of spin-lattice (T ₁) and spin-spin (T ₂) relaxation times for a wide range of concentrations, temperatures and viscosities. T ₁ and T ₂ were measured by a non-resonance absorption method.

It was discovered that some structural regions exist at the different concentrations of Mn(II) ions in solution. So, the structure of highly concentrated solutions may be considered as one of the corresponding crystallohydrate. The structural microinhomogeneities were observed also in the intermediate concentration range at definite temperatures. It is shown that the relaxation mechanism proposed by Bloembergen and Morgan is not effective in the concentration range studied by us.

The analysis of relaxation times and E.P.R. spectra has shown the formation of ‘liquid microphases’ at the freezing point of the solution. Such microphases can exist at temperatures a few tenths of a degree below the solvent freezing point, and its composition considerably differs from the initial solution.

The correlation times for intramolecular and intermolecular electron relaxation mechanisms are evaluated and their nature is discussed.     

Design and synthesis of novel (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-3-((1-substituted phenyl-1H-1,2,3-triazol-4-yl)methyl)thiazolidine-2,4-diones: a potential cytotoxic scaffolds and their molecular modeling studies

In an effort to discover potential cytotoxic agents, a series of novel (Z)-5-((1,3-diphenyl-1H-pyrazol-4-yl)methylene)-3-((1-substituted phenyl-1H-1,2,3-triazol-4-yl)methyl)thiazolidine-2,4-dione derivatives (8a–n) were designed and synthesized in various steps with acceptable reaction procedures with quantitative yields and characterized by ¹H NMR, ¹³C NMR, IR, HRMS and ESI–MS spectra. These newly synthesized novel derivatives were screened for their in vitro cell viability/cytotoxic studies against human breast cancer cell line (MCF-7) with various concentrations of 0.625 µM, 1.25 µM, 2.5 µM, 5 µM and 10 µM, respectively. The biological interpretation assay outcome was demonstrated in terms of cell viability percentage reduction and IC₅₀ values against standard reference drug cisplatin. Based on these results, most of the derivatives exhibited promising cytotoxic activity. Among them, particularly compounds 8j (R₁?=?OMe and R₃?=?NO₂) and 8e (R₃?=?CF₃) demonstrate remarkable cytotoxic activity with IC₅₀ values 0.426 µM?±?0.455 and 0.608 µM?±?0.408, which are even better than the standard drug cisplatin 0.636 µM?±?0.458 and compounds 8m (R₂?=?OMe and R₃?=?OMe) and 8c (R₃?=?OMe) exhibited closely equivalent IC₅₀ values to the standard drug with IC₅₀ values 0.95 µM?±?0.32 and 0.976 µM?±?0.313 and rest of the compounds exhibits moderate cytotoxic activity. Moreover, molecular modeling studies and ADME calculations of the novel synthesized derivatives are in adequate consent with the pharmacological screening results.

     

Classical trajectory calculations for state-resolved Penning ionisation reactions of polycyclic aromatic hydrocarbon C10H8 in collision with He*(23S)

ABSTRACT

The reaction dynamics of Penning ionisation of a polycyclic aromatic hydrocarbon (PAH), naphthalene C₁₀H₈, in collision with the metastable He*(2³S) atom is studied by classical trajectory calculations using an approximate interaction potential energy surface between He* and the molecule, which is constructed based on ab initio calculations for the isovalent Li?+?C₁₀H₈ system. The ionisation width (rate) around the molecular surface are obtained from overlap integrals of the He 1s orbital and the molecular orbital. The calculated collision energy dependences of partial Penning ionisation cross sections (CEDPICS) in the range 50–500?meV at 300?K have reproduced the experimental results semi-quantitatively. The opacity functions, which represent the reaction probability with respect to the impact parameter b, are discussed in connection with collision energy, interaction with He* and the exterior electron density of molecular orbitals. They indicate that the collisional ionisations of C₁₀H₈ can be classified into three types: π electron ionisations with negative collision energy dependences which are predominantly determined by attractive interaction with He*; σ orbitals ionisations of the hardcore type; σ orbital ionisations which reflect interaction potentials around CH bonds. The critical impact parameters b_c become larger with increasing collision energy due to the centrifugal barrier.     

Synthetic applications and methodology development of Chan–Lam coupling: a review

Chan–Lam coupling is one of the most popular and easy methods to perform arylation of amines (N-arylations). This cross-coupling is generally performed by reacting aryl boronate derivatives with a variety of substrates involving nitrogen containing functional groups such as amines, amides, ureas, hydrazine, carbamates. This article summarizes the synthetic applications of this reaction and the efforts of scientists to develop novel and efficient methodologies for this reaction.

     

Establishment and Clinical Application of a Highly Sensitive Time-Resolved Fluorescence Immunoassay for Tumor-Associated Trypsinogen-2

To establish a rapid and highly sensitive assay for tumor-associated trypsinogen-2 (TAT-2) based on the time-resolved fluorescence immunoassay (TRFIA) and evaluate its potential clinical value in patients with lung cancer. The double-antibody sandwich method was used in detecting TAT-2 antigen concentrations, and two types of TAT-2 antibodies (coating antibodies and Eu³⁺ labeled antibodies) were used. A TAT-2–TRFIA method was then established, evaluated, and used in detecting the serum TAT-2 levels of healthy subjects and patients with lung cancer. The linear range of the TAT-2–TRFIA method was 1.53–300 ng/mL, the intra-assay coefficient of variation (CV) were between 1.67% and 8.42%, and the inter-assay CV were between 4.29% and 11.44%. The recovery rates of TAT-2–TRFIA were between 99.17% and 107.06%. The cross-reactivities of trypsin and T-cell immunoglobulin mucin 3 were 0.02% and 0.82%, respectively. The serum TAT-2 levels of patients with lung cancer were higher than those of healthy subjects (P?<?0.001). Combined with TAT-2, the sensitivity and specificity of CEA and CA-125 for lung cancer improved significantly.

Conclusion: We successfully established a highly sensitive TAT-2–TRFIA method, which was able to facilitate the timely diagnosis of lung cancer.

     

Structural Assignments of 1‐(β‐d‐Glucopyranosyl)‐1,2,3‐triazoles by 1H‐ and 13C‐NMR Study

The ¹H‐ and ¹³C‐NMR spectra of 1‐β‐d‐glucopyranosyl‐1,2,3‐triazole‐4,5‐dimethyl carboxylate, 1‐β‐d‐glucopyranosyl‐1,2,3‐triazole‐4,5‐dicarboxamide, ‐dialkylcarboxamide‐N‐nucleosides 4–18, and 6‐amino‐4H‐1‐(1‐β‐d‐glucopyranosyl)‐8‐hydroxy‐1,2,3‐triazolo[4,5‐e][1,3]‐diazepin‐4‐one 19 had been studied. Resonance signals and anomeric configurations were assigned by homo‐ and heteronuclear two dimensional methods (DQF‐COSY, HSQC, HMBC, HMQC, ROESY).     

Nuclear Magnetic Resonance Spectra of 1,2,3- and 1,2,4- Tribromobenzenes

Abstract

The nmr spectra of trisubstituted benzenes such as 1,2,4-chloro⁽¹⁾ and 1,2,5-bromo⁽²⁾ compounds have been reported already. We will report here the results on 1,2,3- and 1,2,4-tribromobenzenes. The samples were synthesized and purified by zone melting- method at the Chiba Institute of Technology. They were dissolved in CCl⁴ with the concentrations of ca. 20 and 75 wt % for 1,2,3- and 1,2,4-compounds, respectively. The spectrometers used are the ones of the types of JNMC-6OH and 100H of Japan Electron Optics Company. The nmr paparameters of 1,2,3- halogenocompounds were obtained by the direct analysis of the spectra taking the system as the one of the AB² type. Those for 1,2,4-compounds were obtained with the use of the electronic computer HITAC-5020 at the University of Tokyo and with the program supplied by Bothner-By. Tetramethyl silane, TMS, was used as the internal standard and the results of the analysis of the spectra at 60 MHz are shown in Table 1. Those values for 1,2,3-trichloro benzene were compared with those obtained from the spectrum at 100 MHz and those in the literature.⁽¹⁾     

Excitation transfer into bound and continuum states investigated by optical and electron spectroscopy

We present energy spectra of electrons formed in the reaction of He(2³ S, 2¹ S) with NO₂ which have significantly improved counting statistics and resolution compared to earlier work. Further, we show spectra of the fluorescence light emitted in these reactions. The data are recorded in the same molecular beam apparatus as the electron spectra. For the metastable singlet state He(2¹ S) the spectra have not been measured before. We find that in addition to ionization excitation transfer takes place into Rydberg states of NO₂**. Subsequently, the highly excited NO₂** molecules dissociate into NO and atomic O* Rydberg atoms.