Vibrational spectroscopic and conformational studies of 1-(4-pyridyl)piperazine

Possible stable conformers of the 1-(4-pyridyl)piperazine (1-4pypp) molecule were experimentally and theoretically studied by FT-IR and Raman spectroscopy. FT-IR and Raman spectra were recorded in the region of 4000–200 cm⁻¹. Optimized geometric structures related to the minimum on the potential energy surface were investigated by the B3LYP hybrid density functional theory method using the 6-31G(d) basis set. Comparison of the experimental and theoretical results indicates that the density functional B3LYP method provides satisfactory results for the prediction of vibrational wavenumbers and structural parameters and equatorial-equatorial (e-e) isomer is supposed to be the most stable form of the 1–4pypp molecule.     

Vibrational spectroscopic studies on fibrinogen adsorption at polystyrene/protein solution interfaces: hydrophobic side chain and secondary structure changes

Structural changes of fibrinogen after adsorption to polystyrene (PS) were examined at the PS/protein solution interface in situ using sum frequency generation (SFG) vibrational spectroscopy and attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR). Different behaviors of hydrophobic side chains and secondary structures of adsorbed fibrinogen molecules have been observed. Our results indicate that upon adsorption, the hydrophobic PS surface induces fast structural changes of fibrinogen molecules by aligning some hydrophobic side chains in fibrinogen so that they face to the surface. Such structural changes of fibrinogen hydrophobic side chains are local changes and do not immediately induce significant changes of the protein secondary structures. Our research also shows that the interactions between adsorbed fibrinogen and the PS surface can induce significant changes of protein secondary structures or global conformations which occur on a much longer time scale.     

Vibrational spectroscopic studies of mesna and dimesna

Raman, and infrared spectra of mesna and dimesna have been collected in the present spectroscopic studies. Based on the group frequencies, relative intensities and Raman depolarization measurements, some vibrational assignments have been suggested. For both mesna and dimesna, at least two rotational conformers have been identified. Adsorption behavior was investigated from the recorded surface-enhanced Raman scattering (SERS) spectra. It was found that both mesna and dimesna adsorbed as thiolate on silver sol particles with the cleavage of the S-H bond in mesna and the S-S bond in dimesna. For the adsorbed thiolate, two conformers existed in the adsorption state.     

Vibrational spectroscopy studies of structural changes in lignin under microwave irradiation

Structural changes that occur in lignin surface-modified with nickel nanoparticles during microwave- assisted dry reforming (DR) are studied via vibrational spectroscopy. IR spectroscopy reveals that the nickel deposition has a considerable effect on the structural characteristics of lignin. It is found that nickel deposition from an acetate salt substantially reduces the intensity of absorption bands at 1700 cm^?1. This finding suggests that Ni(2+) interacts mostly with formate groups, which are subsequently oxidized to carboxylate groups. It is shown that with the deposition of metallic nickel particles from a colloidal nickel solution in toluene prepared via metal vapor synthesis, the nickel particles do not interact with the surface functional groups of the lignin. Deep conversion of an organic mass of lignin by DR to form synthesis gas reduces the intensity of the absorption bands of the identified functional groups and raises the intensity of the absorption bands of the aromatic rings. Raman spectroscopy shows that during lignin conversion, the aromatic rings condense partially to form amorphized graphite. In operando studies reveal that the DR of nickel-modified lignin heated to 200–400°C results in the isolation of vanillic oxygenates that are probably intermediate products of reforming.     

Vibrational spectroscopic identification of isoprene,pinenes and their mixture

Here we show a study of vibrational spectroscopic identification of a few typical organic compounds which are known as the main sources of organic aerosols(OAs) particle matter in air pollution. Raman and IR spectra of isoprene, terpenoids, pinenes and their mixture are meticulously examined, showing distinguishable intrinsic vibrational spectroscopic fingerprints for these chemicals, respectively. As a reference, first-principles calculations of Raman and infrared activities are also conducted. It is interestingly found that, the experimental spectra are peak-to-peak consistent with the DFT(Density Functional Theory)-calculated vibrational activities. Also found is that, in a certain case such as for bpinene, a dimer model, rather than an isolated single molecular model, reproduces the experimental results, indicating unneglected intermolecular interactions. Starting with this study, we are endeavoring to advocate a database of Raman/IR fingerprint spectra for OA haze identification.     

Vibrational spectroscopic studies on the natural product,columbianadin

NIR-FT Raman and FT-IR spectra of columbianadin, extracted from seeds and roots of Heracleum candolleaum, were recorded and analyzed. The vibrational frequencies of the compound have been computed using semi-empirical AM1 method and compared with experimental values. The C=O stretching frequencies of the carbonyl groups have been lowered due to conjugation. The CH stretching and bending vibrations of CH3 groups of the ester part indicate the presence of hyperconjugation effect. Characteristic ring vibrations have also been identified.     

Vibrational spectroscopic studies in the hydrolysis and condensation of chlorotrimethylsilane

Raman and infrared spectroscopy were used to study the hydrolysis and condensation of chlorotrimethylsilane (CTMC) in aqueous organic solvents. From the recorded spectra and their intensity variation with time, we were able to identify trimethylsilanol as the reaction intermediate or the hydrolysis product as well as hexamethyldisiloxane (HMDS) as the final condensation product. The measured Raman intensity of CTMS at different time revealed that hydrolysis of CTMS is first order in terms of the CTMS concentration. From the Raman spectra collected under different conditions, it was noted that condensation reaction rates is faster in neutral condition than in acidic condition.     

Vibrational and high pressure conformational studies of 1,1,2-trichloroethane

The infrared spectra of 1,1,2-trichloroethane were recorded from 4000 to 50 cm^?1 in the vapour and liquid states. Additional spectra above 200 cm^?1 of the low temperature crystal and of two crystalline solids, prepared by compressing the sample in a diamond anvil cell, were obtained. Also, infrared spectra of the liquid and of the compound dissolved in CS₂ were recorded at increased pressures. Raman spectral data of the liquid (including polarization measurements) and of the low temperature crystal were obtained.The fundamental frequencies for each of the two conformers, C₁ and C_s, were assigned and the results checked by normal coordinate analysis. The same diagonal and off-diagonal force constants were employed for the two conformers and the force fields were derived by means of a least squares refinement, including data for chloroethane, 1,1-dichloroethane and various deuterated species. A standard deviation of 3 % was obtained in the final fit.From the changes in relative intensities for infrared bands belonging to the C₁ and C_s conformers with increasing pressure, the volume differences (ΔV¯between the conformers were determined in CS₂ solution and in the pure liquid.     

Vibrational spectroscopic studies of vinyltriethoxysilane sol-gel and its coating

Infrared and Raman spectra of vinyltriethoxysilane (VTES), the VTES sol-gel, and the sol-gel coated aluminum have been collected. The assignments of the vibrational modes for the silane, the sol-gel, and the sol-gel films have been made based on the group frequencies and the spectral variation collected at different physical and chemical states of the sol-gel samples. Applying the sol-gels onto the metal grids allowed the drying and the high temperature treatment of the samples for the collection of infrared transmission spectra. From the variation of the sol-gel and the sol-gel coated aluminum IR spectra with temperature, it was noticed that the samples partially decomposed when the temperature was higher than 100 degrees C. Electrochemical experiments have demonstrated that the anticorrosion property of the coated aluminum has significantly increased. The water and the hexadecane contact angle measurements showed that the surface modified metal had a much higher hydrophobic property than the untreated metal.     

Vibrational spectroscopic studies and ab initio calculations of sulfanilamide

FT-Raman and FT-IR spectra of sulfanilamide were recorded and analyzed. The vibrational frequencies of the compound have been computed using the Hartree-Fock/6-21G(*) basis and compared with the experimental values. The assignments of the observed bands were made on the basis of available literature.     

Vibrational spectroscopic studies of the interaction of water with serine

The vibrational dynamics of water around serine was investigated by using Raman spectroscopy and inelastic incoherent neutron scattering. Experiments with serine in deuterium oxide were performed to assist the assignment. The study shows that for the serine, the exchange of protons-deuterons on the active -NH3+ and -OH groups were relatively easy, whereas there were hardly any exchanged on the -CH or -CH2- groups. The main features of the spectra for hydrated samples (versus the dry samples) were altered considerably; new sharp peaks in the measured spectra appeared, indicating that the hydrogen bonding between water and serine had disturbed the structure of the serine molecule.     

Vibrational spectroscopic and density functional theory studies of chloranil-imidazole interaction

The present work reports vibrational spectra and density functional theory calculations for chloranil, imidazole and their complexes. The experimentally observed infrared and Raman bands have been assigned with the help of calculated vibrational frequencies and potential energy distribution analysis. Some bands of chloranil and imidazole have been found to shift on the complex formation due to partial electronic charge transfer from imidazole to chloranil. The charge transfer between these molecules is also corroborated by the electronic absorption spectroscopy and calculations. The theoretical values of the interaction energy of various possible chloranil-imidazole interactions suggest that the two molecules interact preferably via N and H atoms of imidazole and CO group of chloranil with their molecular planes almost perpendicular to each other.     

Vibrational spectroscopic and thermal studies of some 3-phenylpropylamine complexes

Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)₂Ni(CN)₄ (M = Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60 cm⁻¹. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)₄|_∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes.     

Vibrational spectroscopic and thermal studies of some 3-phenylpropylamine complexes

Four new Hofmann–3-phenylpropylamine (3PPA) type complexes with chemical formulae M(3PPA)₂Ni(CN)₄ (M = Ni, Co, Cd, and Pd) have been prepared and their vibrational spectra are reported in the region of 4000–60 cm⁻¹. The vibrational bands arising from 3PPA ligand molecule, the polymeric sheet and metal–ligand bands of the compounds are assigned. The thermal behaviour of these complexes is also provided using the DTA and TGA along with the magnetic susceptibility data. The results indicate that the monodentate 3PPA ligand molecule bonds to the metal atom of |M–Ni(CN)₄|_∞ polymeric layers and hence the compounds are similar in structure to Hofmann-type complexes.     

Vibrational spectroscopic studies of 4-tert-butylpyridine tetracyanonickelate dioxane clathrates

Two new dioxane clathrates of the form M(4-tert-bupy)₂ Ni(CN)₄·dioxane (M = Ni or Co) have been prepared in powder form. Their spectral data were compared with those of the corresponding host complexes and found to be consistent with the host structure found in Hofmann type clathrates.Presented at the Sixth International Seminar on Inclusion Compounds, Istanbul, Turkey, 27–31 August, 1995.     

Vibrational spectroscopic,conductivity, and calorimetric studies on tripotassium hydrogen diselenate

Infrared spectra of K₃H(SeO₄)₂ obtained at 300 and 77 K, conform to the pattern expected for a very strong O-H O hydrogen bond. Differential scanning calorimetry (DSC) and electrical conductivity measurements indicate the presence of a phase transition at 388 K to a state having high protonic conductivity.A. W. A. is a recipient of a La Trobe University Postgraduate Research Scholarship.     

Vibrational spectroscopic studies and ab initio calculations of 2-cyanophenylisocyanid dichloride

FT-Raman and FT-IR spectra of 2-cyanophenylisocyanid dichloride were recorded and analyzed. The vibrational frequencies of the title compound have been computed using the Hartree-Fock/6-31G* basis and compared with the experimental values. The prepared compound was identified by NMR and mass spectra.     

Vibrational spectroscopic studies of uranyl complexes in aqueous and non-aqueous solutions

Vibrational spectra have been obtained for aqueous solution of uranyl-perchlorates, -fluorides, -chlorides, -acetates and -sulphates over a range of solution composition with added anions. We have prepared [Buⁿ₄N][UO₂Cl₄], [Me₄N][UO₂Cl₄], [Prⁿ₄N][[UO₂(NO₃)₃], [Buⁿ₄N][UO₂(NO₃)₃], with the expectation that the large cation would give a better approximation to vibrational frequencies of the free anion and would allow measurements in non-coordinating solvents. As the perchlorate is not coordinated to [UO₂]²⁺ in aqueous solution the expected structure is a solvated cation [UO₂(OH₂)₅]²⁺ with characteristic infrared 962.5, 253 and 160 cm⁻¹ and Raman 874 and 198 cm⁻¹ bands. The formation of weak, solvated [UO₂X]⁺ complexes (X=F, Cl) has been established with frequencies at 908, 827, 254, 380 cm⁻¹ and 956, 871, 254 and 222 cm⁻¹ for [UO₂F]⁺ and [UO₂Cl]⁺, respectively. Bidentate NO₃ coordination has been established for solid and dissolved (in CH₂Cl₂) [R₄N][UO₂(NO₃)₃] (R=Prⁿ, Buⁿ). Aqueous solutions of UO₂(NO₃)₂ and Cs[UO₂(NO₃)₃] show no clear evidence that bidentate or monodentate nitrate is present. Both unidentate and bidentate linkage of acetate-uranyl were established for acetate complexes in aqueous solutions. For the uranyl sulphate system, monodentate sulphate coordination is the major mode at low SO₄:U ratios, and even at a ratio of 3:1 there is very little free sulphate.