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We employ photoluminescence (PL) spectroscopy on individual nanoscale aggregates of the conjugated polymer poly(3-hexylthiophene), P3HT, at room temperature (RT) and at low temperature (LT) (1.5 K), to unravel different levels of structural and electronic disorder within P3HT nanoparticles. The aggregates are prepared by self-assembly of the block copolymer P3HT-block-poly(ethylene glycol) (P3HT-b-PEG) into micelles, with the P3HT aggregates constituting the micelles' core. Irrespective of temperature, we find from the intensity ratio between the 0-1 and 0-0 peaks in the PL spectra that the P3HT aggregates are of H-type nature, as expected from pi-stacked conjugated thiophene backbones. Moreover, the distributions of the PL peak ratios demonstrate a large variation of disorder between micelles (inter-aggregate disorder) and within individual aggregates (intra-aggregate disorder). Upon cooling from RT to LT, the PL spectra red-shift by 550 cm(-1), and the energy of the (effective) carbon-bond stretch mode is reduced by 100 cm(-1). These spectral changes indicate that the P3HT backbone in the P3HT-b-PEG copolymer does not fully planarize before aggregation at RT and that upon cooling, partial planarization occurs. This intra-chain torsional disorder is ultimately responsible for the intra-and inter-aggregate disorder. These findings are supported by temperature-dependent absorption spectra on thin P3HT films. The interplay between intra-chain, intra-aggregate, and inter-aggregate disorder is key for the bulk photophysical properties of nanoparticles based on conjugated polymers, for example, in hierarchical (super-) structures. Ultimately, these properties determine the usefulness of such structures in hybrid organic-inorganic materials, for example, in (bio-)sensing and optoelectronics applications.

Petrological and geochemical studies of lamproites can provide useful insights into the nature of their lithospheric mantle sources, but their geochemical and mineralogical diversity has complicated our understanding of their primary/parental melt composition, volatile (CO2, H2O) inventory and magmatic evolution. To help address this issue, we present a detailed study of different generations (primary, pseudo-secondary, secondary) of crystal, and melt and fluid inclusions in olivine, Cr-spinel and perovskite from three olivine lamproites in the Ellendale Field of the West Kimberley Province (Australia) in order to understand the composition and evolution of their parental magmas. Melt inclusions in the different host minerals and from each of these localities are broadly similar to each other and consist of glass, alkali/alkali-earth (Mg-Ca-K-Na-Ba) carbonates, phosphates and chlorides, in addition to minerals typical of lamproite groundmass (fluorapatite, perovskite, phlogopite, diopside, wadeite, Mg-ilmenite, Fe-Mg-Ti-Cr spinel). The dominant volatile species in the melt and fluid inclusions is CO2 based on Raman data. Heating experiments of melt/fluid inclusions in olivine show significant phase transformations in which the carbonate may separate into an immiscible carbonate-rich sulphatebearing fraction or exsolve a CO2 fluid. Our results indicate that carbonates, along with alkali/alkali-earths, halogens and sulphur, became progressively concentrated in the West Kimberley lamproitic magmas during crystallisation, leading to the entrapment of a complex array of daughter minerals, some not previously reported from lamproites and, in some inclusions, immiscible carbonate melt. The widespread occurrence of daughter carbonates in melt/fluid inclusions in lamproite minerals is at odds with their apparent paucity in the lamproite groundmass. The presence of carbonate and the abundance of CO2-rich and H2O-poor melt and fluid inclusions are attributed to the preferential partitioning of CO2 into the vapour and retention of H2O in the magma during degassing, coupled with H2O loss by post-entrapment modification of the inclusions through H+ diffusion. (C) 2022 Published by Elsevier B.V. on behalf of International Association for Gondwana Research.

Structural chemistry 34(1), 203 - 213 (2023). doi:10.1007/s11224-022-02053-4, Here, we present new cryogenic infrared spectra of the (Imidazole)$_nH^+$ (n=1,2,3) ions. The data was obtained using helium tagging infrared predissociation spectroscopy. The new results were compared with the data obtained by Gerardi et al. (Chem. Phys. Lett. 501:172–178, 2011) using the same technique but with argon as a tag. Comparison of the two experiments, assisted by theoretical calculations, allowed us to evaluate the preferable attachment positions of argon to the (Imidazole)$_nH^+$ frame. Argon attaches to nitrogen-bonded hydrogen in the case of the (Imidazole)H+ ion, while in (Imidazole)$_2H^+$ and (Imidazole)$_3H^+$ the preferred docking sites for the argon are in the center of the complex. This conclusion is supported by analyzing the spectral features attributed to the N–H stretching vibrations. Symmetry adapted perturbation theory (SAPT) analysis of the non-covalent forces between argon and the (Imidazole)$_nH^+$ (n=1,2,3) frame revealed that this switch of docking preference with increasing complex size is caused by an interplay between induction and dispersion interactions., Published by Springer Science Business Media B.V., Dordrecht

Small linear alkanes, pentane and hexane, and their cyclic counterparts, cyclopentane and cyclohexane, have been examined via molecular dynamics simulations. We assess the thermodynamic, structural and dynamic behavior of said liquids, paying particular attention to dynamic properties such as diffusion coefficients, vibrational spectra, rotational correlation functions and relaxation times. The study gives an insight into the overall behavior of small alkanes, accentuating the nuances imposed by the difference in molecular shape. This is particularly relevant when considering the widespread use of these liquids as solvents.

The characterization and synthesis of 3-chloro-2-{(2E)-2-[1-(4-chlorophenyl)ethylidene]hydrazinyl}pyridine (CCPEHP) was investigated in our study. Mass and UV-visible spectra were recorded in chloroform solvent. The CCPEHP molecule containing pyridine and chlorophenyl rings and hydrazone group crystallized in the triclinic system and P-1 space group. FTRaman and FTIR spectra were performed in the solid state. The optimized geometry of CCPEHP was computed by DFT/B3LYP method with 6-311 G (d, p) and 6-31 G (d, p) levels. The computed vibrational analysis, electronic absorption spectrum, electronic properties, molecular electrostatic potential, natural bond orbitals analysis and other calculated structural parameters were determined by using the DFT/B3LYP/6-31 G (d, p) basis set. The correlation of fundamental modes of the compound and the complete vibrational assignments analysis were studied. The strong and weak contacts were identified by using Hirshfeld surface analysis. The molecular modeling results showed that CCPEHP structure strongly binds to COVID-19 main protease by relative binding affinity of-6.4 kcal/mol. (c) 2021 Elsevier B.V. All rights reserved.

VUV photons from a synchrotron source were used to record the gas-phase absorption spectrum of isoquinoline over the range 3.5 to 10.7 eV. The rich spectrum exhibits both broad and sharp features, of varying intensities, that are analyzed into eight valence and eight Rydberg transitions. Previous data on the valence transitions of isoquinoline were essentially limited to solution spectra up to 5.4 eV. Our study increases their number considerably. The features in the 3.96 eV region are discussed in terms of vibronic coupling between the nπ∗ 1 1 A′′ and ππ∗ 2 1 A′ valence electronic states. The intensities of some spectral features are augmented by collective π-electron modes considered to be of plasmon-type. Assignments of the valence transitions were facilitated by our DFT calculations and by earlier Pariser-Parr-Pople MO calculations. The calculation results are compared and their relative value is discussed. The DFT calculations reproduce very well a number of experimentally determined properties of the ground state of isoquinoline, in particular its bond distances and angles, rotational constants, vibrational frequencies and dipole moment. No Rydberg series of isoquinoline have previously been observed. Three of the newly observed Rydberg series converge to the D 0 electronic ground state of the ion, while two converge to the D 1 and three to the D 3 excited electronic states of the cation. Astrophysical applications of the VUV absorption spectrum of isoquinoline, in particular the measured absorption cross-sections, are briefly discussed. A comparison between the absorption spectra of isoquinoline and quinoline highlights their similarities and differences, related to their respective molecular orbitals.

We present a computational screening of experimental structural repositories for fast Li-ion conductors, with the goal of finding new candidate materials for application as solid-state electrolytes in next-generation batteries. We start from similar to 1400 unique Li-containing materials, of which similar to 900 are insulators at the level of density-functional theory. For those, we calculate the diffusion coefficient in a highly automated fashion, using extensive molecular dynamics simulations on a potential energy surface (the recently published pinball model) fitted on first-principles forces. The similar to 130 most promising candidates are studied with full first-principles molecular dynamics, including an estimate of the activation barrier for the most diffusive structures. The results of the first-principles simulations of the candidate solid-state electrolytes found are discussed in detail.

Nonlinear optical (NLO) activity of the compound (2E)-2-(ethoxycarbonyl)-3-[(1-methoxy-l-oxo-3phenylpropan-2-yl)amino] prop-2-enoic add is investigated experimentally and theoretically using X-ray crystallography and quantum chemical calculations. The NLO activity is confirmed by both powder Second Harmonic Generation (SHG) experiment and first hyper polarizability calculation. The title compound displays 8 fold excess of SHG activity when compared with the standard compound KDP. The gas phase geometry optimization and vibrational frequencies calculations are performed using density functional theory (DFT) incorporated in B3LYP with 6-311G++ (d,p) basis set. The title compound crystallizes in non-centrosymmetric space group P21. Moreover, the crystal structure is primarily stabilized through intramolecular N-H center dot center dot center dot O and O-H center dot center dot center dot O hydrogen bonds and intermolecular C-H center dot center dot center dot O and C-H center dot center dot center dot pi interactions. These intermolecular interactions are analyzed and quantified using Hirshfeld surface analysis and PIXEL method. The detailed vibrational assignments are performed on the basis of the potential energy distributions (PED) of the vibrational modes. (C) 2015 Elsevier B.V. All rights reserved.

The controlled fabrication of nanometer-scale objects is without doubt one of the central issues in current science and technology. In this article, we exhibit a simple, one-step bench top synthesis of zinc oxide nano-tetrapods and nano-spheres which were tailored by the facial growth of nano-wires (diameter approximate to 24 nm; length approximate to 118 nm) and nano-cubes (approximate to 395 nm edge) to nano-sphere (diameter approximate to 585 nm) appeaded. The possibilities of inexpensive, simple solvo-chemical synthesis of nanostructures were considered. In this article, a successful attempt has been made that ZnO nano-structures dispersed on well aligned hydrogen bonded liquid crystals (HBLC) comprising azelaic acid (AC) with p-n-alkyloxy benzoic acid (nBAO) by varying the respective alkyloxy carbon number (n=5). The dispersion of nanomaterials with HBLC is an effective route to enhance the existing functionalities. A series of these composite materials were analyzed by polarizing optical microscope's electro-optical switching. An interesting feature of AC + nBAO is the inducement of tilted smectic G phase with increasing carbon chain length. Phase diagrams of the above hybrid ZnO nanomaterial influenced LC complex and pure LC were constructed and compared. The switching times, the contrast ratio and spontaneous polarization of the nanostructures-HBLC composite film were carried out by systematic investigation. The sample preparation parameters, such as the curing time and curing intensity were optimized. The critical applied voltage to achieve the switching bi-stability of our device is only 4.5 V, which is approximately twice its threshold voltage for Freedericksz transition. This performance puts the hybrid structure at the top level in the state of the art in application oriented research in optics of liquid crystalline composite materials. (C) 2015 Elsevier B.V. All rights reserved.

anti-4-phenoxyphenylaminoglyoxime (LH2) was synthesized starting from 4-aminodiphenylether and anti-chloroglyoxime in absolute ethanol. Then, mononuclear complexes [Ni(II) and Cu(II)] of LH2 were synthesized with the metal:ligand ratio of 1:2. The LH2 and its complexes [Ni(LH)(2) and Cu(LH)(2)] were characterized by elemental analysis, FT-IR, Raman, UV-vis, thermogravimetric analysis (TGA), H-1 NMR, C-13 NMR, heteronuclear multiple bond correlation (HMBC) spectroscopy and theoretical DFT studies. Also, redox properties of the ligand and its complexes were investigated by cyclic voltammetry in DMSO solution at room temperature. Conformational space was scanned with molecular mechanic simulations and then the possible stable conformers of LH2 ligand were determined by B3LYP/6-311++G (d,p) level calculations. The Ni(LH)(2) and Cu(LH)(2) metal complexes were modeled theoretically using B3LYP/LanL2DZ level. The theoretical vibrational frequencies were calculated by using optimization calculation levels. The NMR parameters of LH2 ligand, Cu(LH)(2) and Ni(LH)(2) metal complexes were calculated at mPW1PW91/6-311 + G (2d,p) level. Theoretically calculated values were compared with the related experimental values. The DFT calculation results have been used to predict and interpret the molecular structures of LH2 ligand and its complexes. The geometry around nickel in Ni(LH)(2) and around cupper in Cu(LH)(2) complex are almost square planar. In addition, we evaluated the efficacy of LH2 ligand and its Ni(LH)(2) and Cu(LH)(2) complexes in the breast adenocarcinoma cell line (MCF7). Our data showed that the metal compounds affect positively the cytotoxic activity of the ligand (LH2). The metal complexes, especially Ni(LH)(2) complex, exhibited noteworthy biological activity against the viability of MCF7 cells. (C) 2020 Elsevier B.V. All rights reserved., Research Fund of Selcuk University [09201024], This work was supported by the Research Fund of Selcuk University Project Number: 09201024. The authors thank Dr Umit Ceylan (Department of Medical Services and Techniques, Vocational High School of Health Services, Giresun University, 28100 Giresun, Turkey) for providing help for the preliminary theoretical vibrational frequencies calculations and assignments by Gauss View 5.0.

Experimental and computational study of molecular structure, vibrational and UV-spectral analysis of Hydrazine (1, 3-Dinitrophenyl) (HDP) derivatives. The crystal was grown by slow cooling method and the crystalline perfection of single crystals was evaluated by high resolution X-ray diffractometry (HRXRD) using a multicrystal X-ray diffractometer. Fluorescence, FT-IR and FT-Raman spectra of HDP crystal were recorded. The assignments of the vibrational spectra have been carried out with the help of normal co-ordinate analysis (NCA) followed by scaled quantum force field methodology (SQMFF). NMR studies have confirmed respectively the crystal structure and functional groups of the grown crystal. The energy and oscillator strength calculated by Time-Dependent Density Functional Theory (TD-DFT) result complements the experimental findings. The calculated MESP, UV, HOMO-LUMO energies show that charge transfer done within the molecule. And various thermodynamic parameters are studied. Fukui determines the local reactive site of electrophilic, nucleophilic, descriptor. (C) 2017 Elsevier B.V. All rights reserved.

While N-heterocyclic carbenes (NHC) are ubiquitous ligands in catalysis for organic or industrial syntheses, their potential to form transition metal complexes for medicinal applications has still to be exploited. Within this frame, we synthesized new homo- and heterobimetallic complexes based on the Au(I)-NHC scaffold. The compounds were synthesized via a microwave-assisted method developed in our laboratories using Au(I)-NHC complexes carrying a pentafluorophenol ester moiety and another Au(I) phosphane complex or a bipyridine ligand bearing a pendant amine function. Thus, we developed two different methods to prepare homo- and heterobimetallic complexes (Au(I)/Au(I) or Au(I)/Cu(II), Au(I)/Ru(II), respectively). All the compounds were fully characterized by several spectroscopic techniques including far infrared, and were tested for their antiproliferative effects in a series of human cancer cells. They showed moderate anticancer properties. Their toxic effects were also studied ex vivo using the precision-cut tissue slices (PCTS) technique and initial results concerning their reactivity with the seleno-enzyme thioredoxin reductase were obtained.

(4-Nitro-phenyl)-oxo-acetaldehyde oxime (ninapH) is a type of oxime, which has a oxime and α-carbonyl groups. This molecule has been synthesized from literature procedure. The structural properties and conformational behaviors were examined using the density functional theory (DFT) with the B3LYP method combined with the 6-311++G(d,p) basis set. As a result of the conformational studies, the most stable conformer was determined, and then this molecule was optimized with the same basis set. Comprehensive theoretical and experimental structural studies on the molecule have been carried out by FT-IR, NMR and UV–vis spectrometry. The calculated HOMO and LUMO energies show that charge transfer within the molecule. The first order hyperpolarizability and molecular electrostatic potential (MEP) were also performed. The thermodynamic properties (heat capacity, entropy, and enthalpy) of the ninapH have been calculated at different temperatures, 100–1000 K. In addition, the molecular docking studies have been performed with DNA and protein structures (downloaded from Protein Data Bank).

The unprecedented, direct chemical oxidation of L-proline to pyrroline-2-carboxylate was achieved in water (pH 9–10) by means of NH4VO3/NH3 or V2O5/MOH (K = Na, K), and the anion was fully characterized as ammonium or alkaline metal salts. Quantitative yield and higher atom economy performance were achieved with the latter system, the alkaline salts being more stable than the ammonium one. Different mixed valence V(IV)/V(V) compounds precipitated from the reaction mixtures depending on the nature of the employed base. A possible reaction mechanism is proposed according to DFT calculations. The analogous reaction of trans-4-hydroxy-L-proline with NH4VO3/NH3 afforded pyrrole-2-carboxylic acid in 81% yield, while sarcosine underwent prevalent decomposition under similar experimental conditions. Instead, no reaction was observed with primary (glycine, L-alanine, L-phenylalanine) and tertiary α-amino acids (N,N-dimethyl-L-phenylalanine, N,N-dimethylglycine).

We present a benchmark study of spectral simulation protocols for the amide I band of proteins. The amide I band is widely used in infrared spectroscopy of proteins due to the large signal intensity, high sensitivity to hydrogen bonding, and secondary structural motifs. This band has, thus, proven valuable in many studies of protein structure function relationships. We benchmark spectral simulation protocols using two common force fields in combination with several electrostatic mappings and coupling models. The results are validated against experimental linear absorption and two-dimensional infrared spectroscopy for three well-studied proteins. We find two-dimensional infrared spectroscopy to be much more sensitive to the simulation protocol than linear absorption and report on the best simulation protocols. The findings demonstrate that there is still room for ideas to improve the existing models for the amide I band of proteins.

New compounds [(CH3)(3)PH][SbBr4] and [(CH3)(3)PH][SbCl4] adopting a discrete (0D) and one-dimensional (1D) structure, respectively, were synthesized. Differential scanning calorimetry and thermogravimetric measurements showed that both salts undergo a single phase transition at 373 K/416 K (chlorine/bromine analog) followed by partial decomposition. Both crystals were structurally characterized at room temperature. H-1 NMR measurements were used to study the dynamics of the [(CH3)(3)PH](+) cation in the solid phase, which helped to understand the thermal instability of the crystals. In addition, DFT (Density Functional Theory) calculations gave insight into the relative stability of the possible phases of the studied crystals. The mechanism of crystal decomposition is discussed in this work.

International audience; Surface-enhanced Raman scattering (or spectroscopy), commonly known as SERS, has been employed to investigate the adsorption mechanism and orientation of 1,4-dimethoxy-2-nitro-3-methylanthracene-9,10-dione (DMNMAD) molecule onto silver. Silver nanoparticles (Ag NPs) were synthesized based on a solution combustion method using citric acid as a fuel. Scanning electron microscopy and transition electron microscopy studies confirm the crystalline nature and morphology of the synthesized silver nanoparticles. Theoretical normal Raman spectra (nRs) and SERS spectra of the DMNMADmolecule, simulated based on DFT/B3PW91 level of theory were validated experimentally. Experimental and theoretical vibrational modes correlate well, confirming the reliable assignments of the vibrational bands. Enhancement of C=O stretching and C-H in-plane vibrational modes in the SERS spectrum indicates the 'stand-on' orientation of the molecule on the silver nanoparticles after adsorption. The frontier molecular orbitals confirm the charge transfers between the molecule and silver nanoparticles following the process of adsorption. As anthraquinone derivatives have been recently used as potent anti-tumour drugs, the adsorption studies reported in the current investigation can pave way to the potential application of DMNMAD in drug delivery.

A study was carried-out to measure and calculate infrared (4000-400 cm(-1)) and Raman (3500-50 cm(-1)) spectra of cyclo(His-Phe) dipeptide, which has anticancer activity. Conformational preferences of cyclo(His-Phe) dipeptide are investigated using theoretical conformational analysis followed by DFT calculations. The calculations of cyclo(His-Phe) dipeptide, as a function of side chain torsion angles, enable us to determine its energetically preferred conformations. The DFT calculations predict that the boat conformation is energetically more stable than the planar conformation. The dimeric forms of cyclo(His-Phe) dipeptide are constructed by bringing together two identical cyclo(His-Phe) monomers in possible configurations and three energetically favorable dimeric structures are obtained. The vibrational normal modes and associated wavenumbers, IR and Raman intensities of the global conformers of monomeric and dimeric units of cyclo(His-Phe) are calculated by DFT method at either both B3LYP/6-31G(d,p) and B3LYP/6-31++G(d,p) levels of theory (for monomer) or only at B3LYP/6-31G(d,p) level of theory (for dimeric unit). The total energy distributions (TED) of the vibrational modes are calculated by using the scaled quantum mechanical force field (SQM FF) method. Complete vibrational assignments of the observed spectra were performed by the aid of computed vibrational data. The cis amide II band is observed at 1481 cm(-1) in the Raman spectrum of solid cyclo(His-Phe), which is in agreement with previously reported Raman results for solid cyclic dipeptides, where the DKP ring adopts a boat conformation. The combination of the experimental and calculated spectra provide an insight into the structural and vibrational spectroscopic properties of cyclo(His-Phe) dipeptide. The energies of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of cyclo(His-Phe) are calculated by DFT method at B3LYP/6-31G(d,p) level of theory. HOMO is localized on histidine amino acid whereas LUMO is localized mostly on phenylalanine ring. The computed HOMO-LUMO energy gap corresponds to 6.3596 eV (146.65 kcal/mol). (C) 2012 Elsevier B.V. All rights reserved.

We report the characterization and solution chemistry of a series of Fe(II) complexes based on the pentadentate ligands N4Py (1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)methanamine), MeN4Py (1,1-di(pyridin-2-yl)-N,N-bis(pyridin-2-ylmethyl)ethanamine), and the tetradentate ligand Bn-N3Py (N-benzyl-1,1-di(pyridin-2-yl)-N-(pyridin-2-ylmethyl)methanamine) ligands, i.e., [Fe(N4Py)(CH(3)CN)](ClO(4))(2) (1), [Fe(MeN4Py)(CH(3)CN)](ClO(4))(2) (2), and [Fe(Bn-N3Py)(CH(3)CN)(2)](ClO(4))(2) (3), respectively. Complexes 2 and 3 are characterized by X-ray crystallography, which indicates that they are low-spin Fe(II) complexes in the solid state. The solution properties of 1-3 are investigated using (1)H NMR, UV/vis absorption, and resonance Raman spectroscopies, cyclic voltammetry, and ESI-MS. These data confirm that in acetonitrile the complexes retain their solid-state structure, but in water immediate ligand exchange of the CH(3)CN ligand(s) for hydroxide or aqua ligands occurs with full dissociation of the polypyridyl ligand at low (3) and high (9) pH. pH jumping experiments confirm that over at least several minutes the ligand dissociation observed is fully reversible for complexes 1 and 2. In the pH range between 5 and 8, complexes 1 and 2 show an equilibrium between two different species. Furthermore, the aquated complexes show a spin equilibrium between low- and high-spin states with the equilibrium favoring the high-spin state for 1 but favoring the low-spin state for 2. Complex 3 forms only one species over the pH range 4-8, outside of which ligand dissociation occurs. The speciation analysis and the observation of an equilibrium between spin states in aqueous solution is proposed to be the origin of the effectiveness of complex 1 in cleaving DNA in water with (3)O(2) as terminal oxidant.

This work was carried out with the financial support of Engineering and Physical Sciences Research Council (EPSRC), U.K. A series of 5-alkyl/aryl-1,3 lambda(4)delta(2),2,4,5-dithiadiazarsoles RAs(S2N2) (R = Me, Et, Pr-i, Bu-t, Ph, Mes) were prepared by a ligand exchange between [(Bu2Sn)-Bu-n(S2N2)](2) and the corresponding organodihalogenoarsines RAsX2 (X = Cl, I). All products were characterized by NMR, IR, and Raman spectroscopies and mass spectrometry. The crystal structures of the aryldithiadiazarsoles (R = Ph, Mes) were determined. Postprint

A series of air-stable, robust and highly active palladium based precatalysts of amido-functionalized N-heterocyclic carbenes for the Suzuki-Miyaura C-C cross-coupling reaction has been designed. In particular, the [1-R-3-{N-(benzylacetamido)imidazol-2-ylidene](2)PdCl(2) [R = i-Pr (1c) and CH(2)Ph (2c)] complexes efficiently carried out the Suzuki-Miyaura coupling of the aryl bromide and iodide substrates with phenyl boronic acid in good to excellent yields in air at 90 degrees C in 12 h. Quite interestingly, of these palladium precatalysts, the i-propyl derivative (1c) exhibited superior activity as compared to the benzyl derivative (2c). The density functional theory (DFT) studies carried out on the 1c and 2c complexes revealed the strong sigma-donating nature of the NHC ligand as reflected in their high d/b ratio [i.e. forward sigma-donation (d) to backward pi-donation (b)] of these complexes and, thus, point towards greater stability of the Pd-NHC interaction in these complexes. (C) 2009

Highly convenient copper-free and amine-free Sonogashira coupling of aryl bromides and iodides with terminal acetylenes under amenable conditions in air and in a mixed aqueous medium are reported using several new, user friendly and robust palladium precatalysts (1-5) of N/O-functionalized N-heterocyclic carbenes (NHCs). In particular, the precatalysts, 1 and 2, were synthesized from the imidazolium chloride salts by the treatment with PdCl(2) in pyridine in presence of K(2)CO(3) as a base while the precatalysts, 3-5, were synthesized from the respective silver complexes by the treatment with (COD) PdCl(2). The DFT studies carried out on the 1-5 complexes suggest the presence of strong NHC-Pd sigma-interactions arising out of deeply buried NHC-Pd sigma-bonding molecular orbitals (MOs) that account for the inert nature of the metal-carbene bonds and also provide insights into the exceptional stability of these precatalysts. (C) 2009

A new series of robust, user-friendly, and highly active PEPPSI-themed (pyridine-enhanced precatalyst preparation, stabilization and initiation) (NHC)PdX(2)(pyridine)-type (X = Cl, Br) precatalysts of C4-C5 saturated imidazole- (1-4) and triazole-based (5 and 6) N-heterocyclic carbenes for the Hiyama and Sonogashira couplings under amenable conditions are reported. Specifically 1-6 efficiently catalyze the fluoride-flee Hiyama coupling of aryl halides with PhSi(OMe)(3) and CH(2)=CHSi(OMe)(3) in air in the presence of NaOH as a base in a mixed aqueous medium (dioxane/H(2)O, 2:1. v/v). Along the same lines, these 1-6 precatalysts also promote the Cu-free and amine-free Sonogashira coupling of aryl bromides and iodides with phenylacetylene in air and in a mixed aqueous medium (DMF/H(2)O, 3/1 v/v). The complexes 1-6 were synthesized by the direct reaction of the respective imidazolinium and triazolium halide salts with PdCl(2), in pyridine in the presence of K(2)CO(3) as a base. DFT studies on the catalytically relevant palladium(0) (NHC)Pd(pyridine) precursors 1a-6a reveal significant donation from the N-heterocyclic carbene lone pair onto the unfilled sigma* orbital of the trans Pd-pyridine bond. This weakens the Pd-bound "throw-away" pyridine ligand, and its dissociation marks the initiation of the catalytic cycle. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

The nu(CN) vibrational spectra of cyanide groups bridging two metal atoms present a confused picture. Factors relevant to the interpretation of the available data are reviewed. Some mechanisms for frequency change, relative to the corresponding terminal species, are made more quantitative than previously described, and others are highlighted for the first time. The kinematic effect is much less important than previously assumed. It seems that an effect responsible for the major part of the frequency increase upon bridging commonly observed is the cation electric field, together with concomitant relaxation (the IVSE model). However, a contribution may well come from the change in the sigma bonding in the CN unit.

Surfactant outgrowth during dissolution as myelin figures, which happens on contact with water, is of prime importance in emulsification and detergency. Micro-Raman investigation of different lyotropic phases formed during dissolution of aerosol-OT (his 2-ethylhexyl sulfosuccinate) in water during myelin formation reveals the flexible arrangement of the surfactant bilayers in myelin. The conformation around CC-CS bond and the hydrocarbon chains of aerosol-OT in the different liquid crystalline phases were identified from the fingerprints of CC-CS stretching, C-C stretching, C-H bending, and stretching frequencies. Existence of mixture of trans and gauche conformations around CC-CS bond and that of the hydrocarbon chains in myelin supports the fluid nature of bilayers by which it is made. Similar conformations of hydrocarbon chains in lamellar phase and in myelin support the concept of myelins being rolled up lamella. The observations are in line with the disorderness of the hydrocarbon chains in the bilayers of phospholipids that has been reported earlier. From the C-C stretching frequencies at the root of myelins, the kinked structure of the hydrocarbon chain is identified, and loose packing of molecules which would facilitate water transport across membranes is evident.

Raman spectroscopy has emerged as a powerful and important characterisation tool for probing molecular semiconducting materials. The useful optoelectronic properties of these materials arise from the delocalised ?-electron density in the conjugated core of the molecule, which also results in large Raman scattering cross-sections and a strong coupling between its electronic states and vibrational modes. For this reason, Raman spectroscopy offers a unique insight into the properties of molecular semiconductors, including: chemical structure, molecular conformation, molecular orientation, and fundamental photo- and electro-chemical processes - all of which are critically important to the performance of a wide range of optical and electronic organic semiconductor devices. Experimentally, Raman spectroscopy is non-intrusive, non-destructive, and requires no special sample preparation, and so is suitable for a wide range of in situ measurements, which are particularly relevant to issues of thermal, and photochemical stability. Here we review the development of the family of Raman spectroscopic techniques, which have been applied to the study of conjugated molecular semiconductors. We consider the suitability of each technique for particular circumstances, and the unique insights which it can offer, with a particular focus on the significance of these measurements for the continuing development of stable, high performance organic electronic devices.

The adsorption of 5-fluorouracil (5FU) and 5-bromouracil (5BrU) by sepiolite and loughlinite (natural Na-sepiolite) has been investigated using FT-IR spectrometry. The spectroscopic results indicate that 5-halogenouracils adsorbed on sepiolite and loughlinite are coordinated to surface hydroxyls and/or to Lewis acidic centers by hydrogen bonding interaction through the oxygen lone pairs. Some intensity and frequency changes in the OH stretching and deformation bands of surface hydroxyls (Si-OH) of the 5-fluorouracil and 5-bromouracil treated sepiolite and loughlinite were observed. Adsorption capacity of the sepiolite is found to be higher than loughlinite for 5-halogenuracils. Moreover adsorption capacity of clays were found to decrease in the order 5-fluorouracil >5-bromouracil.

A new model for 2,2,2-trifluoroethanol is proposed. It is a 7-atom model with the methylene group treatedas an united atom. The model was optimized to reproduce the physicochemical properties of the pure liquid.The properties of the new model were compared with the available experimental data over a range oftemperatures. Furthermore, mixtures with the SPC water model were simulated to assess the ability to reproduceavailable thermodynamic and kinetic data as well as dielectric properties. The model provides a good agreementwith experimental data for the neat liquid and for mixtures with water.

We present high-resolution X-ray powder diffraction (XRPD) data collected at the BM16 beamline at ESRF on a set of dehydrated Ti-silicalite-1 (TS-1) samples having Ti content (molar ratio) x =[Ti]/([Ti]+[Si]) in the range 0–0.022. The cell volume values resulting from Rietveld refinements of the powder diffraction data exhibit very good linear correlation ( r =0.99994) with Ti content: V ( x )=2093.0 x + V (0) [ V (0)=5335.8 A 3 ]. This work represents a continuation of the important characterization work of the EniRicerche group [ J. Catal. 137, 497 (1992)] performed on TS-1 previously treated with ammonium acetate, calcined, and measured in atmosphere (i.e., under partially hydrous conditions). Our results indicate that when XRPD measurements are performed under carefully controlled vacuum conditions a highly linear correlation between V and x is obtained without any need for sample pretreatment. Finally, the very high quality of our experimental data allows us to comment on the presence of some preferential framework T sites for Ti substitution. Such sites were recently proposed by two different groups on the basis of the results of molecular dynamics modeling.

Hydantoin (C(3)H(4)N(2)O(2), 2,4-imidazolidinedione) was isolated in argon matrix at 10 K and its infrared spectrum and unimolecular photochemistry were investigated. The molecular structure of the compound was studied both at the DFT(B3LYP) and MP2 levels of approximation with valence triple- and quadruple-ζ basis sets (6-311++G(d,p); cc-pVQZ). It was concluded that the minima in the potential energy surfaces of the molecule correspond to C(1) symmetry structures. However, the energy barrier separating the two-equivalent-by-symmetry minima stays below their zero-point energy, which makes the C(s) symmetry structure, which separates the two minima, the experimentally relevant one. The electronic structure of the molecule was studied in detail by performing the Natural Bond Orbital analysis of its electronic configuration within the DFT(B3LYP)/cc-pVQZ space. The infrared spectrum of the matrix isolated compound was fully assigned also with help of the theoretically predicted spectrum. Upon irradiation at λ = 230 nm, matrix-isolated hydantoin was found to photofragment into isocyanic acid, CO, and methylenimine.

International audience; Trimethylaluminum (TMA) complexes of methyl-, n-propyl-, cyclopropyl-, allyl-, and propargylamine were synthesized and their experimental properties and theoretical characteristics were compared with the respective amine-borane analogues. The amine ligand of an amine-TMA Lewis acid-base complex can be easily changed by another amine through a 2:1 amine-TMA intermediate in pentane at room temperature. The exchange of the same ligands in the case of amine-boranes requires remarkably more time in line with the calculated relative energy of the respective transition state. The (1)H and (13)C NMR experiments examining the addition of one or more equivalent of amine to the respective Lewis acid-base complex conclude in the fast exchange of the amine ligand in the NMR time scale only in the cases of amine-TMA complexes, which could also be caused by similar 2:1 complexes. However, in gas phase, only 1:1 amine-TMA complexes are present as evidenced by ultraviolet photoelectron spectroscopy (UPS). The observed UP spectra, which are the first recorded photoelectron spectra of primary amine-TMA compounds, indicate that the stabilization effect of the lone electron pair of nitrogen atom in amines during the borane complexation is stronger than that of the TMA complexation. In line with this observation, the destabilization of the σ(Al-C) orbitals is lower than that of σ(B-H) orbitals during the formation of amine-TMA and amine-borane complexes, respectively. As showed by theoretical calculations, the CH(4) elimination of the studied amine-TMA complexes is exothermic, indicating the possibility of using these compounds in metal organic chemical vapor deposition techniques (MOCVD). On the other hand, our experimental conditions avoid this methane elimination and constitutes the first procedure employing distillation to isolate primary amine-TMA complexes.

The synthesis and thermal decomposition of the energetic material, bis(nitratomethyl)-1,3-bishomocubane (DNMBHC) were undertaken. The optimized structure of DNMBHC was obtained by ab initio methods and was utilized to calculate the heat of formation, heat of combustion and detonation properties. The slow thermal decomposition of DNMBHC was investigated by thermogravimetric analysis (TGA) at heating rates of 10 degrees C/min, while fast pyrolysis was investigated utilizing sub-milligram quantities at heating rates of 100 degrees C/s. The gaseous products from fast pyrolysis were detected by rapidscan FTIR spectroscopy to postulate probable decomposition pathways. The primary decomposition pathway was found to involve O-NO2 bond scissions to form NO2, subsequently leading to several secondary reactions. A secondary pathway involving detachment of the nitrate ester group from the ring to form MeONO2 was also predicted. The products involving the bishomocubane ring were found to be relegated to the condensed phase. (C) 2013 Elsevier B.V. All rights reserved.

This study demonstrates for the first time, the spectroscopic characterization of Canakkale Meteorite that fell at Canakkale, Republic of Turkey (40 degrees 8'44 '' N; 26 degrees 24'23 '' E). The olivine group [(Mg, Fe)(2)SiO4], enstatite [Mg2Si2O6] (one of the orthopyroxene minerals) and plagioclase were identified by the micro-Raman and FTIR spectroscopies and EDX-SEM analyses. This meteorite has not yet been classified in the World's Database of Meteorites. The aim of this study is to investigate this meteorite by vibrational spectroscopic techniques and open the possibility to classify it and list in the World's Database of Meteorites. (C) 2012 Elsevier B.V. All rights reserved.

Highly efficient palladium precatalysts {[RN{-(CH(2))(n)-pz(2)(3,5-Me)}(2)]PdCl(2)}(m) [m = n = 1; R = 2,6-Me(2)C(6)H(3) (1), 2,4,6-Me(3)C(6)H(2) (2), CH(2)Ph (3) and m = n = 2; R = CH(2)Ph (4)] of a series of homoscorpionate bispyrazolyl ligands for the Suzuki-Miyaura cross-coupling of the more challenging aryl chloride substrates are reported. In particular, the palladium 1-4 precatalysts carried out the Suzuki-Miyaura cross-coupling of a wide variety of aryl chloride substrates bearing electron withdrawing, electron donating and heteroaryl substituents. Remarkably enough, the molecular structure determination of the 1-4 precatalysts by X-ray diffraction studies revealed the presence of anagostic [C-H center dot center dot center dot Pd] type interactions in the mononuclear 1-3 complexes of methylene bridged bispyrazolyl ligands whereas the ethylene bridged analog 4 yielded an interesting dimeric 20-membered macrometallacyclic complex devoid of any such interaction.

Based on first-principle molecular dynamic simulations, we calculate the far-infrared spectra of small water clusters (H2O)(n) (n=2,4,6) at frequencies below 1000 cm(-1) and at 80 K and at atmospheric temperature (T > 200 K). We find that cluster size and temperature affect the spectra significantly. The effect of the cluster size is similar to the one reported for confined water. Temperature changes not only the shape of the spectra but also the total strength of the absorption, a consequence of the complete anharmonic nature of the classical dynamics at high temperature. In particular, we find that in the frequency region up to 320 cm(-1), the absorption strength per molecule of the water dimer at 220 K is significantly larger than that of bulk liquid water, while tetramer and hexamer show bulklike strengths. However, the absorption strength of the dimer throughout the far-infrared region is too small to explain the measured vapor absorption continuum, which must therefore be dominated by other mechanisms. (c) 2008 American Institute of Physics.

The phonon and crystal field excitations in several rare earth titanate pyrochlores are investigated. Magnetic measurements on single crystals of Gd2Ti2O7, Tb2Ti2O7, Dy2Ti2O7 and Ho2Ti2O7 are used for characterization, while Raman spectroscopy and terahertz time domain spectroscopy are employed to probe the excitations of the materials. The lattice excitations are found to be analogous across the compounds over the whole temperature range investigated (295-4 K). The resulting full phononic characterization of the R2Ti2O7 pyrochlore structure is then used to identify crystal field excitations observed in the materials. Several crystal field excitations have been observed in Tb2Ti2O7 in Raman spectroscopy for the first time, among which all of the previously reported excitations. The presence of additional crystal field excitations, however, suggests the presence of two inequivalent Tb3+ sites in the low temperature structure. Furthermore, the crystal field level at approximately 13 cm-1 is found to be both Raman and dipole active, indicating broken inversion symmetry in the system and thus undermining its current symmetry interpretation. In addition, evidence is found for a significant crystal field-phonon coupling in Tb2Ti2O7. These findings call for a careful reassessment of the low temperature structure of Tb2Ti2O7, which may serve to improve its theoretical understanding., 13 pages, 7 figures

The electronic transitions of phenylacetylene complexes with water and trifluoroethanol are shifted to the blue, while the corresponding transitions for methanol and ethanol complexes are shifted to the red relative to the phenylacetylene monomer. Fluorescence dip infrared (FDIR) spectra in the O-H stretching region indicate that, in all the cases, phenylacetylene is acting as a hydrogen bond acceptor to the alcohols. The FDIR spectrum in the acetylenic C-H stretching region shows Fermi resonance bands for the bare phenylacetylene, which act as a sensitive tool to probe the intermolecular structures. The FDIR spectra reveal that water and trifluoroethanol interact with the pi electron density of the acetylene C-C triple bond, while methanol and ethanol interact with the pi electron density of the benzene ring. It can be inferred that the hydrogen bonding acceptor site on phenylacetylene switches from the acetylene pi to the benzene pi with lowering in the partial charge on the hydrogen atom of the OH group. The most significant finding is that the intermolecular structures of water and methanol complexes are notably distinct, which, to the best of our knowledge, this is first such observation in the case of complexes of substituted benzenes.

Terahertz absorption spectra of three isomeric structures of dicyanobenzene in chloroform solution and solid phase at 298 K are reported. These spectra exhibit enhanced absorption in low THz range compared to most organic systems because of strong coupling to phonon modes. Molecular vibrational spectral calculations show strong correlation with the experiment especially for solution spectra. All intramolecular modes were assigned and intermolecular modes identified. Out-of-plane intramolecular modes at low frequency exhibit similar to 75 cm(-1) blue shifts as the secondary CN group moves from the para to ortho position on the benzene ring, whereas almost no frequency shift occurs for low-frequency in-plane modes.

The "Fonds Européen de Développement Économique des Régions" (FEDER) ; Fonds de la Recherche Scientifique (Communauté française de Belgique) - F.R.S.-FNRS ; The COST action P9 “Radiation Damage in Biomolecular Systems”; International audience; Core shell excitation spectra of aniline at the carbon and nitrogen 1s edges have been obtained by inner-shell electron energy-loss spectroscopy recorded under scattering conditions where electric dipolar conditions dominate, with higher resolution than in the previous studies. They are interpreted with the aid of ab initio configuration interaction calculations. The spectrum at the C 1s edge is dominated by an intense π* band. The calculated chemical shift due to the different chemical environment at the carbon 1s edge calculated is in agreement with the experimental observations within a few tenths of an eV. The transition energies of the most intense bands in the C 1s excitation spectrum are discussed at different levels of calculations. In the nitrogen 1s excitation spectrum the most intense bands are due to Rydberg-valence transitions involving the σ* -type molecular orbitals, in agreement with the experiment. This assignment is different from that of extended Hückel molecular orbital calculations. The geometries of the core excited states have been calculated and compared to their equivalent core molecules and benzene.

The calculation of the vibrational Raman spectrum of enzyme-bound beta-lactamase inhibitors may be of help to understand the mechanisms responsible for bacterial drug resistance. Here, we present a study of the solvation structure and the vibrational properties of clavulanate, an important beta-lactamase inhibitor, in aqueous solution as obtained from full quantum and hybrid empirical/quantum molecular dynamics simulations at ambient conditions. The analysis of the vibrational density of states indicates that hybrid empirical/quantum mechanical simulations are able to properly describe the vibrational levels of clavulanate in solution. In addition, we propose a computationally efficient protocol to calculate the vibrational Raman effect for large solute molecules in water, which is able to faithfully reproduce the experimentally recorded clavulanate Raman spectrum and discloses the possibility to employ hybrid simulations to assign the experimental Raman spectra of inhibitors bound to beta-lactamases.

Trends in the properties of normal valent and multivalent halogen-oxygen bonding are examined for the isomers of the halogen polyoxide families of the types (YXO2) and (YXO3), Y= Cl, Br, I, H, CH(3), X=Cl, Br, I. A qualitative model is formulated on the relationship between the X-O bond distance variations, the ionic character of the bonding, and the degree of halogen valence. The relative stability and enthalpy of formation of each species are also suggested to correlate with the ionic nature of the X-O bonding and the electrostatic character of the Y, YO fragments. In the model presented, halogen hypervalence is interpreted to be the result of partial p -> d promotion of lone-pair valence electrons followed by the formation of two, four, or six additional pd hybrid bonds around the halogen atom. Bioinorg Chem Appl

In this work, the mechanism of the 'gelation' process and the thermal-induced structural modifications of thin film of vanadium pentoxide xerogels deposited on indium tin oxide (ITO)-coated glasses have been studied. Vanadium pentoxide xerogel has been prepared by using the sol-gel proton exchange resin route without any resin pretreatment. To monitor the effect of the 'resin efficiency' on the gelation process, the solution coming out from the resin has been collected in a sequence of different containers (vials), separately investigated by Raman spectroscopy. After the spin coating deposition, the thin films of vanadium pentoxide get have been subjected to different annealing treatments. The highest thermal treatment (600 degrees C) induces a complete transformation of the gel phase into an anhydrous polycrystalline phase of a sodium-containing vanadate, different from the usual V2O5 crystal. It is due to the diffusion of foreign ions (mainly sodium) coming from the substrate into the vanadium oxide layer.

First-principles density functional studies of the dynamical properties of the conjugated polymers polyaniline and poly(p-pyridyl vinyline) are presented in this work. We have employed linear response within density functional perturbation theory, as implemented in the CASTEP code, to investigate the Born effective charges, polarizabilities, and vibrational properties. With regard to the last, we have calculated the vibrational frequencies and made assignments of the modes for the two polymers. Most of the phonon modes have been classified and we have shown that the higher frequency modes are associated with C - H and C = N stretching modes. We also present the results of calculations of the polarizability and permittivity of the materials which are in reasonable agreement with the typical values of conjugated polymers. Dynamical Born effective charges have been calculated and compared with the Mulliken population atomic charges. It is found that notable differences exist between the Born effective charges for the nitrogen atoms in the conducting polymers, and we conclude that effective charges are more appropriate for use in the study of the dynamics of the systems. Differences are found in the ir absorption spectra obtained for the two polymers, which can be attributed to the structural differences of the two materials. It is found that the presence of the nitrogen atom plays an important role in determining their lattice dynamics.

Vanadium oxide (1 wt %) supported on gamma-Al(2)O(3) was used to investigate the interface between the catalytically active species and the support oxide. Raman, UV-vis-NIR DRS, ESR, XANES, and EXAFS were used to characterize the sample in great detail. All techniques showed that an isolated VO(4) species was present at the catalyst surface, which implies that no V-O-V moiety is present. Surprisingly, a Raman band was present at 900 cm(-1), which is commonly assigned to a V-O-V vibration. This observation contradicts the current literature assignment. To further elucidate on potential other Raman assignments, the exact molecular structure of the VO(4) entity (1 V=O bond of 1.58 A and 3 V-O bonds of 1.72 A) together with its position relative to the support O anions and Al cation of the Al(2)O(3) support has been investigated with EXAFS. In combination with a structural model of the alumina surface, the arrangement of the support atoms in the proximity of the VO(4) entity could be clarified, leading to a new molecular structure of the interface between VO(4) and Al(2)O(3). It was found that VO(4) is anchored to the support oxide surface, with only one V-O support bond instead of three, which is commonly accepted in the literature. The structural model suggested in this paper leaves three possible assignments for the 900 cm(-1) band: a V-O-Al vibration, a V-O-H vibration, and a V-(O-O) vibration. The pros and cons of these different options will be discussed.

In this paper the temperature evolution of the main Raman peak at about 630 cm−1 has been studied in order to detect the ferroelectric to paraelectric phase transition in strontium barium niobate (SrxBa1−xNb2O6) crystals with different stoichiometries (x = 0.33, 0.5 and 0.61). Both its peak wavenumber and width have been shown to be strongly dependent on temperature and display clear anomalies around the Curie temperature. The obtained results manifest the usefulness of simple unpolarized Raman spectra to probe the changes in Tc as a result of modifications in the crystal composition.

Vanadium oxide (1 wt %) supported on gamma-Al2O3 was used to investigate the interface between the catalytically active species and the support oxide. Raman, UV-vis-NIR DRS, ESR, XANES, and EXAFS were used to characterize the sample in great detail. All techniques showed that an isolated VO4 species was present at the catalyst surface, which implies that no V-O-V moiety is present. Surprisingly, a Raman band was present at 900 cm(-1), which is commonly assigned to a V-O-V vibration. This observation contradicts the current literature assignment. To further elucidate on potential other Raman assignments, the exact molecular structure of the VO4 entity (1 V=O bond of 1.58 angstrom and 3 V-O bonds of 1.72 angstrom) together with its position relative to the support 0 anions and Al cation of the Al2O3 support has been investigated with EXAFS. In combination with a structural model of the alumina surface, the arrangement of the support atoms in the proximity of the VO4 entity could be clarified, leading to a new molecular structure of the interface between VO4 and Al2O3. It was found that VO4 is anchored to the support oxide surface, with only one V-O support bond instead of three, which is commonly accepted in the literature. The structural model suggested in this paper leaves three possible assignments for the 900 cm(-1) band: a V-O-Al vibration, a V-O-H vibration, and a V-(O-O) vibration. The pros and cons of these different options will be discussed.