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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

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.

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.

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.

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.

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)

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.

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.

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.

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.

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.

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.

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.

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

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.

Computational chemistry has made tremendous impact on the development of a variety of new materials including catalysts, semiconductors, ceramics, polymers, functional materials, etc. Traditionally, first-principles calculations were employed to clarify the chemical reactions on electronic and atomic level, which is essential for the materials and catalysts design. However, this method cannot simulate the chemical reaction dynamics at reaction temperatures, which is crucial fault and defect for more precise and accurate design to establish next-generation nanotechnology. Recently, first-principles quantum chemical molecular dynamics (QCMD) approach is expected to solve the above problem, however it can simulate very small system because it requests huge computational costs. Hence, recently we have succeeded in developing a tight-binding quantum chemical molecular dynamics (TB-QCMD) program, “Colors”, based on our original tight-binding theory. This method realizes over 5000 times acceleration in calculation time, compared to the conventional first-principles molecular dynamics method. To realize high accuracy in spite of the above high calculation speed, all the parameters for “Colors” were determined on the basis of first-principles density functional calculations. Thus, this novel TB-QCMD program was used successfully and effectively to investigate chemical reaction dynamics of large simulation models at reaction temperatures. In this review, we put forward the application of this newly developed code for the design of novel materials and catalysts systems.

Quantum mechanical calculations are carried out to investigate the structural, harmonic frequency and relative stability trends for a number of XClO(2)and XBrO(2)oxides (X=H, CH3, HO, CH3O, Cl, Br, I) of significant interest in stratospheric halogen chemistry. The Cl-O and Br-O bond distances, harmonic frequencies and stabilities are compared to the chain type isomeric structures, XOOCl and XOOBr and demonstrate the hypervalent nature of the halogen atom, presenting a notable dependence on the degree of the ionic character of halogen-oxygen bond and the electronegativity of the X fragment. Match-Communications in Mathematical and in Computer Chemistry

Two different effective-core-potential methodologies, augmented with extra polarization functions are used at the MP2 level of theory to investigate the isomers of I-containing peroxides of the type XOOI, XIO2, IXO2, XOIO and IOXO (X = Cl, Br, I). The reliability of the results is checked against the all-electron calculations of Misra and Marshall [J. Phys. Chem. A, 102 (1998) 9056] for the IOOI family. Contrary to what has been well established for the chlorine and bromine analogs, the present study confirms the interesting observation that the I-containing peroxide isomers, XOOI, are not the most stable structures in each subfamily. (C) 2003 Elsevier Science B.V. All rights reserved. Journal of Molecular Structure-Theochem

Ab initio quantum mechanical methods are employed to study methyl bromoperoxide and its isomers which are interesting intermediates in the reaction between methoxy radicals and bromine monoxide. Structural parameters, harmonic frequencies and relative energetics are calculated for all isomeric and conformeric forms. The CH3OOBr isomer is found to be the lowest energy structure followed by CH3OBrO while CH3BrO2 lies much higher in energy. The role of these isomers in the mechanism of the reaction CH3O + BrO is examined. Several transition state structures for the most important reaction channels are also investigated. Physical Chemistry Chemical Physics

Detailed Fe vibrational spectra have been obtained for the heme model complex [Fe(TPP)(CO)-(1-Melm)] using a new, highly selective and quantitative technique, Nuclear Resonance Vibrational Spectroscopy (NRVS). This spectroscopy measures the complete vibrational density of states for iron atoms, from which normal modes can be calculated via refinement of the force constants. These data and mode assignments can reveal previously undetected vibrations and are useful for validating predictions based on optical spectroscopies and density functional theory, for example. Vibrational modes of the iron porphyrin-imidazole compound [Fe(TPP)(CO)(1-Melm)] have been determined by refining normal mode calculations to NRVS data obtained at an X-ray synchrotron source. Iron dynamics of this compound, which serves as a useful model for the active site in the six-coordinate heme protein, carbonmonoxy-myoglobin, are discussed in relation to recently determined dynamics of a five-coordinate deoxy-myoglobin model, [Fe(TPP)(2-MeHIm)]. For the first time in a six-coordinate heme system, the iron-imidazole stretch mode has been observed, at 226 cm(-1). The heme in-plane modes with large contributions from the nu(42), nu(49), nu(50), and nu(53) modes of the core porphyrin are identified. In general, the iron modes can be attributed to coupling with the porphyrin core, the CO ligand, the imidazole ring, and/or the phenyl rings. Other significant findings are the observation that the porphyrin ring peripheral substituents are strongly coupled to the iron doming mode and that the Fe-C-O tilting and bending modes are related by a negative interaction force constant.

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.

Geometries for possible transition states and energy minima of the potential-energy surface for the reaction between BrO and ClO radicals and for conformers of ClOOBr peroxide have been identified and harmonic frequency calculations have been carried out at the second-order Moller-Plesset perturbation theory level using the 6-311++G(2d) and the 6-311++G(3df) basis sets. The energetics have been studied using the CCSD(T)/6-311++G(3df) methodology at the MP2 calculated geometries. The results assist in the qualitative understanding of the mechanism and the kinetics of the stratospherically important BrO + ClO reaction. Journal of Physical Chemistry A

The effect of initial vibrational energy and the mode of disposal of available energy into products for the disproportionation reaction between BrO radicals are studied using the quasiclassical trajectory (QCT) technique. The calculations are performed on an analytical potential enegy surface based on ab initio results reported for the three isomeric forms of (BrO)(2) system. The results indicate a mild dependence on reactant vibrational energy, which is discussed in terms of the mechanistic aspects of the reaction. The study of the distribution of total accessible energy among products indicates a different mode of energy disposal in each path and hence important differences on the mechanism by which each channel takes place. Canadian Journal of Chemistry-Revue Canadienne De Chimie

Ab initio quantum mechanical studies for BrOOBr peroxide and its isomers were carried out at the MP2 level of theory using the 6-311 + G(2d) basis set. Three minima were determined which are in good consistency with previous density functional theory calculations. On the basis of the ab initio results a simple analytical potential energy surface (PES) was constructed and quasiclassical trajectory calculations (QCT) for the self-reaction of BrO radical were performed. Reactive cross-sections, rate coefficients and branching ratios for the two reactive channels are calculated for a series of initial relative kinetic energies which compare favourably with the experimental trends. The quantum mechanical calculations and the analysis of the trajectory results support the experimental evidence that the reaction proceeds through an energetically enriched conformer of BrOOBr peroxide, Tn addition, the increasing collision lifetime with decreasing collision energy indicates a possible weak stabilization of a short-lived collision complex at lower temperatures which must be responsible for the increasing importance of the rate coefficient of the secondary channel as the temperature decreases, in consistency with the experimental evidence. (C) 1999 Elsevier Science B.V. All rights reserved. Chemical Physics

The dense phase of CO2-CS2 mixtures has been analysed by Raman spectroscopy as a function of the CO2 concentration (0.02-0.95 mole fractions) by varying the pressure (0.5 MPa up to 7.7 MPa) at constant temperature (313 K). The polarised and depolarised spectra of the induced (nu(2), nu(3)) modes of CS2 and of the nu(1)-2 nu(2) Fermi resonance dyad of both CO2 and CS2 have been measured. Upon dilution with CO2, the evolution of the spectroscopic observables of all these modes displays a \"plateau-like\" region in the CO2 mole fraction 0.3-0.7 never previously observed in CO2-organic liquids mixtures. The bandshape and intensity of the induced modes of CS2 are similar to those of pure CS2 up to equimolar concentration, after which variations occur. The preservation of the local ordering from pure CS2 to equimolar concentration together with the non-linear evolution of the spectroscopic observables allows inferring that two solvation regimes exist with a transition occurring in the plateau domain. In the first regime, corresponding to CS2 concentrated mixtures, the liquid phase is segregated with dominant CS2 clusters, whereas, in the second one, CO2 monomers and dimers and CO2-CS2 hetero-dimers coexist dynamically on a picosecond time-scale. It is demonstrated that the subtle interplay between attractive and repulsive interactions which provides a molecular interpretation of the non-ideality of the CO2-CS2 mixture allows rationalizing the volume expansion and the existence of the plateau-like region observed in the pressure-composition diagram previously ascribed to the proximity of an upper critical solution temperature at lower temperatures. (C) 2013 AIP Publishing LLC.