Chiroptical properties of 12,15-dichloro[3.0]orthometacyclophane—correlations between molecular structure and circular dichroism spectra of a biphenylophane

The valence excited electronic states and the circular dichroism (CD) spectra of the recently synthesized 12,15-dichloro[3.0]orthometacyclophane 1 are discussed by means of quantum chemical calculations which combine density functional theory with the single-excitation configuration interaction approach (DFT/SCI). The X-ray structure of this highly strained biphenylophane is presented. In order to investigate the influence of the cyclophane-type distortions on the CD spectrum of 1, the CD spectra of three model geometries (2a–2c) are also calculated. It appears that the CD spectrum of the biphenylophane 1 differs substantially from that of the corresponding unstrained biphenyl 2c. Furthermore, it is found that the pyramidalization of the bridging atoms of the cyclophane ring is an important factor for the red shift of the first band with respect to that of an unstrained benzene chromophore.     

DFT study of the electronic and charge transfer properties of perfluoroarene–thiophene oligomers

The ground state structures of 5,5″-diperfluorophenyl-2,2′:5′,2″:5″,2‴-quaterthiophene (1), 5,5′-bis{1-[4-(thien-2-yl)perfluorophenyl]}-2,2′-dithiophene (2), 4,4′-bis[5-(2,2′-dithiophenyl)]-perfluorobiphenyl (3), 5,5″-diperfluorophenyl-2,2′:5′,2″-tertthiophene (4), 5,5′-diperfluorophenyl-2,2′-dihiophene (5), and 5,5-diperfluorophenylthiophene (6) have been optimized at the B3LYP/6-31G(d), B3LYP/6-31G(d,p), PBE0/6-31G(d), and PBE0/6-31G(d,p) level of theories. The B3LYP/6-31+G(d) and PBE0/6-31+G(d) level of theories have been applied to investigate the absorption spectra. The PBE0 functional is good to predict the C–S bond lengths while the C–F bond lengths are good envisaged with B3LYP functional. The increment of thiophene rings between two perfluoroarene rings leads to red shift in absorption spectra. The electron affinities are energetically destabilized while energetic stabilization of the radical-cation increases by decreasing the thiophene rings from four to one. The perfluoroarene rings leads to enhance the electron injection.     

Theoretical study of dynamical properties on reaction path in molecular internal coordinates

The dynamical properties on reaction path (IRC) in internal coordinates have been obtained, which in. clude ω_K (frequencies orthogonal to IRC), L_K (vibrational modes), B_(KF) (coupling constants between the IRC and vibra tions orthogonal to it), B_(KL) (coupling constants between every two vibrations orthogonal to IRC). A set of theory of teac. tion path in molecular internal coordinates has been also constructed. The dynamical properties, including ω_K, B_(KF) B_(KL) of the reaction H~1O~2H~3 H~4→H~1O~2 H~3H~4 have been calculated, which explicitly explain the interaction, chang ing trend and contribution of each chemical bond (including bond angle) in the reaction.     

Molecular structure,vibrational spectra and nonlinear optical properties of orthoarsenic acid–tris-(hydroxymethyl)-aminomethane DFT study

In this work, we report a theoretical study on molecular structure, vibrational spectra and nonlinear optical properties of orthoarsenic acid–tris-(hydroxymethyl)-aminomethane (OATA). The theoretical geometrical parameters in the ground state have been investigated by density functional method (B3LYP and BLYP) with 6-311G(d,p) basis set. The influence of intermolecular interactions effects on molecular properties has been considered by calculation performed on (OATA) dimer. The optimized geometric bond lengths and bond angles are in well agreement with the experimental data. As compared to theoretical frequencies of the monomer, the calculated values obtained for (OATA) dimer are in much better agreement with the experiment. All experimental vibrational bands have been discussed and assigned to normal modes on the basis of our theoretical calculations. B3LYP method has shown better fit to experimental ones than BLYP in calculation vibrational frequencies. To investigate nonlinear optical behaviour, the electric dipole moment μ, the polarizability α and the hyperpolarizability β were computed using DFT//B3LYP/6-311G(d,p) method.     

Physicochemical properties of ether-functionalized ionic liquids [CnOC2mim][Gly] (n = 1–5)

Journal of Thermal Analysis and Calorimetry - A novel ionic liquid 1-ethoxyethyl-3-methylimidazolium glycine ([C2OC2mim][Gly]) was prepared and characterized by 1H NMR spectroscopy, 13C NMR...     

Friedel–Crafts acylation using bismuth triflate in [BMI][PF6]

Bismuth trifluoromethanesulfonate was found to be a good catalyst for the Friedel–Crafts acylation. Bismuth triflate immobilized in an ionic liquid was the most efficient catalytic system. Bismuth triflate in [BMI][PF₆] catalyzes this reaction under microwave irradiation allowing the rapid synthesis of aryl ketones in excellent yields. The catalyst system was easily recovered and reused several times.     

Synthesis–structure correlations of manganese–cobalt mixed metal oxide nanoparticles

Mixed metal oxides in the nanoscale are of great interest for many aspects of energy related research topics as water splitting, fuel cells and battery technology. The development of scalable, cost-efficient and robust synthetic routes toward well-defined solid state structures is a major objective in this field.While monometallic oxides have been studied in much detail, reliable synthetic recipes targeting specific crystal structures of mixed metal oxide nanoparticles are largely missing. Yet, in order to meet the requirements for a broad range of technical implementation it is necessary to tailor the properties of mixed metal oxides to the particular purpose. Here, we present a study on the impact of the nature of the gas environment on the resulting crystal structure during a post-synthesis thermal heat treatment of manganese–cobalt oxide nanoparticles. We monitor the evolution of the crystal phase structure as the gas atmosphere is altered from pure nitrogen to synthetic air and pure oxygen. The particle size and homogeneity of the resulting nanoparticles increase with oxygen content, while the crystal structure gradually changes from rocksalt-like to pure spinel. We find the composition of the particles to be independent of the gas atmosphere. The manganese–cobalt oxide nanoparticles exhibited promising electrocatalytic activity regarding oxygen evolution in alkaline electrolyte. These findings offer new synthesis pathways for the direct preparation of versatile utilizable mixed metal oxides.     

Synthesis, bioactivity and DFT structure–activity relationship study of novel 1,2,3-thiadiazole derivatives

A series of novel 1,2,3-thiadiazole derivatives were designed and synthesized. Their structures were characterized by ¹H NMR, MS and HRMS. The bioactivity tests indicated that compound 9b exhibits a favorable KARI inhibition rate, and some of these novel compounds also showed moderate herbicidal activity against Brassica campestris.     

Stability of mechanical properties of molecular layer–deposited alucone

We report on the effect of aging on the mechanical properties of molecular layer–deposited (MLD) thin films. We studied the mechanical failure of the films during uniaxial tensile testing and observed a sixfold difference in the crack-onset strain (COS) and related flexibility within the first two days after the samples were exposed to ambient air. The MLD films made using trimethylaluminum and ethylene glycol are notorious for exhibiting structural changes after the fabrication; we show that these changes are detrimental for mechanical robustness of the films. This information aids to plan the handling or the protection of these films to achieve better performance with these materials. The interfacial shear strains and COSs of the shortly air-exposed 300-nm-thick films were observed to be roughly 0.3% and 1.8%, respectively. These values are the highest reported so far for hybrid organic–inorganic MLD thin films and would extrapolate to about 14% COS for 5-nm-thick film, indicating potential applications as interfacial adhesion layer for films on polymer substrates and as a protective coating in battery applications.     

Representation of molecular structure using quantum topology with inductive logic programming in structure–activity relationships

The requirement of aligning each individual molecule in a data set severely limits the type of molecules which can be analysed with traditional structure activity relationship (SAR) methods. A method which solves this problem by using relations between objects is inductive logic programming (ILP). Another advantage of this methodology is its ability to include background knowledge as 1st-order logic. However, previous molecular ILP representations have not been effective in describing the electronic structure of molecules. We present a more unified and comprehensive representation based on Richard Bader's quantum topological atoms in molecules (AIM) theory where critical points in the electron density are connected through a network. AIM theory provides a wealth of chemical information about individual atoms and their bond connections enabling a more flexible and chemically relevant representation. To obtain even more relevant rules with higher coverage, we apply manual postprocessing and interpretation of ILP rules. We have tested the usefulness of the new representation in SAR modelling on classifying compounds of low/high mutagenicity and on a set of factor Xa inhibitors of high and low affinity.     

DFT study of the conductance of molecular wire:The effect of coupling geometry and intermolecular interaction on the transport properties

The density functional theory (DFT) combining with the non-equilibrium Green functions (NEGF) method is applied to the study of the electronic transport properties for a Di-thiol-benzene (DTB) molecule coupled to two Au(111) surfaces. The dependence of the transport properties on the bias, the coupling geometry of the molecule-electrode interface, and the intermolecular interaction are examined in detail. The results show that the existence of the hydrogen atom at the end of the DTB molecule would significantly decrease the transmission coefficients, and then the differential conductance (dI/dV). By changing the position of the DTB molecule located between two electrodes a maximum value of calculated current is observed. It is also found that the intermolecular interaction will strongly influence the transport properties of the system studied.     

A comparative study of the structure and properties of β-galactosidases

A comparative study of β-galactosidase amino acid sequences of E. coli and another four out of 11 microorganisms selected at the first stage was performed. It was shown that the functional amino acid residues in the catalytic domain and the ligand environment of the magnesium cation for all five sequences are identical. The mechanism of the catalytic action of E. coli and K. lactis β-galactosidases was investigated by the method of nucleophilic competition. It was shown that the mechanism of the effects of nucleophilic agents is kinetically identical both enzymes: the presence of methanol or butanediols affects the stage of degalactosylation; the presence of magnesium cations promotes the activity of both β-galactosidases; and the mechanisms of the thermal inactivation of E. coli and K. lactis β-galactosidases are different.     

Crystal structure and thermal properties of [Pt(NH3)5Cl][ReCl6]Cl·H2O

The crystal structure of double complex salt [Pt(NH₃)₅Cl][ReCl₆]Cl·H₂O is determined. Crystallographic characteristics are: a = 23.9502(4) Å, b = 7.5963(1) Å, c = 8.9016(2) Å, V = 1619.49(5) ų, space group Pnma, Z = 4, d _x = 3.150 g/cm³. The packing of structural fragments is studied. It is shown that on heating the salt in a helium atmosphere up to 840 °C a mixture of two solid solutions of fcc Pt_0.90Re_0.10 and hcp Pt_0.25Re_0.75 forms.     

Magnetic properties of electrochemically prepared crystalline films of Prussian blue-based molecular magnets K j CrII k [CrIII(CN)6] l · mH2O

Crystalline films (thickness ～1 μm) of Prussian blue-based molecular magnets, synthesized using electrochemical method at two different reduction potentials ?0.5 and ?0.9 V, result into K_0.1Cr^II _1.45[Cr^III(CN)₆]?·?mH₂O (film 1) and K_0.8Cr^II _1.1[Cr^III(CN)₆]?·?mH₂O (film 2), respectively. The structural and magnetic properties of such films are investigated using atomic force microscopy (AFM), X-ray diffraction (XRD), infrared (IR) spectroscopy, and dc magnetization measurements. The film morphology, examined using AFM, shows uniformly distributed triangular crystallites over the substrate surface. The presence of Cr^III–C≡N–Cr^II sequence, in the range of 1,900 to 2,300 cm^?1 in IR spectra, confirms formation of Prussian blue analogues. The XRD results reveal information about the crystalline nature of the films and the relative intensities of the Bragg peaks change with the K⁺ ions. The exchange interaction between Cr ions through C≡N ligand confirms that the electron transfer from C≡N molecule to Cr ions is ferrimagnetic in nature. The high Curie temperatures (T _C) are found to be ～195 and ～215 K for film 1 and film 2, respectively. The higher value of T _C is attributed to the inclusion of more K⁺ ions for film 2, resulting decreases in the Cr^III(C≡N)₆ vacancies and increases in the number of nearest neighbors of Cr^II ions. The branching in the zero field-cooled and field-cooled magnetization data below Curie temperature is explained in terms of kinetic behavior of magnetic domains with different cooling conditions and the presence of water molecule vacancies in the lattice.     

DFT study of adenine–cytosine mismatch in quaternary systems involving DNA bases

Structural Chemistry - In the present work, the adenine–cytosine mismatch is theoretically investigated in quaternary systems involving DNA bases. The calculations, in gas phase, are...     

Synthesis and mesomorphic properties of calix[4]resorcinarene–triphenylene oligomers

By controlling the mol ratios of reactants, novel calix[4]resorcinarene–triphenylene monomer, dimer and tetramer were designed and synthesised in yields of 50–60% via Click chemistry. Their structures were characterised by NMR and MS. Their liquid crystalline behaviours were studied by differential scanning calorimetry, polarising optical microscopy and X-ray diffraction analysis. The more triphenylene units on calix[4]resorcinarene resulted in the wider temperature scopes of mesophase and higher phase transition temperatures. The monomer 6 and dimer 7 showed the mixed columnar mesophase with hexagonal columnar structure and disordered lamellar columnar structure, and compound 8 possessed only disordered lamellar columnar mesophase. These research results suggest that calix[4]resorcinarene was a good platform to construct columnar liquid crystal and the mesomorphic properties were greatly influenced by the substituted numbers of mesogen units on calix skeleton.