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Raman spectra of liquid, and infrared spectra of gaseous as well as matrix isolated 1,1,2,2-tetrachloro-1,3-disilacyclopentane were recorded and analyzed with the aid of DFT calculations. Complete assignment of the experimental vibrational spectral bands is made. Experimental results and DFT calculations confirm that 1,1,2,2-tetrachloro-1,3-disilacyclopentane exists as single twist conformer in gaseous and liquid states as well as isolated in Ar and N 2 matrices. Fast dissociation of 1,1,2,2-tetrachloro-1,3-disilacyclopentane takes place in gas phase, while the molecule remains stabile in condensed phase. The spectral data and results of DFT calculations in anharmonic approximation confirm that dissociation of 1,1,2,2-tetrachloro-1,3-disilacyclopentane starts with the cleavage of C C bond of the five membered ring. Dichlorodimethylsilane and HCl were found to be the main products of the dissociation. The geometry and stability of the title molecule is discussed in the light of recent publications on the studies of similar substituted disilacyclapentanes. [ABSTRACT FROM AUTHOR]

Abstract: Infrared spectra of propanoic acid isolated in the neon and argon matrixes were obtained and studied with the aid of the DFT calculations. The geometric structures of the cyclic and open dimers of PA were elucidated. The calculations predict that among various types of the open dimers only one type with additional hydrogen bond between oxygen of hydroxyl group of a monomer and hydrogen of hydroxyl group of other monomer (OH dimer) is energetically favorable. Structure of this dimer differs from that of formic and acetic acids, where open dimers with the hydrogen bond between oxygen of hydroxyl group and hydrogen of terminal methylene group (CH dimer) are formed. This finding explains fact why formic and acetic acids in crystalline state form polymer chains while higher member of homological row of the monocarboxylic acids (starting from propanoic) acid crystallizes as cyclic dimers. Due to the low barrier between the open and cyclic dimers of propanoic acid the open dimer is experimentally observed only in the neon matrix formed by rapid freezing of the gaseous matrix mixture from 300K down to 2.8K. Similar structures were not observed in the conventional 15K argon matrix. [Copyright &y& Elsevier]

The present work provides results of amorphous hydrogenated carbon (a-C:H) films deposited by direct ion beam deposition method. Hexane (C6H14+Hdelivery) or acetylene (C2H2) precursors and their mixture with hydrogen (H2) were used. The films were characterized by Raman spectroscopy (RS), ellipsometry, and electrical resistance measurements. RS indicates increase in sp3/sp2 bonding ratio and disorder in graphite clusters, upon increasing of hydrogen content (from 0% to 50% for acetylene precursor) in the deposition gas mixture. The opposite trend is observed when the hydrogen concentration exceeded 50% (for acetylene) or additional hydrogen was added (for hexane). The data of electrical resistance measurements support the correlations defined by RS. [Copyright &y& Elsevier]

Self assembly layers were studied by a polarization modulation FT-spectroscopy mapping technique. The optical lay out is based on polarization modulation FT infrared reflection absorption spectroscopy (PM-FT-IRRAS). Here we report for the first time on a PM-FT-IRRAS mapping instrument. Octadecanephosphonic acid adsorbed on a patterned aluminum/gold surface was investigated. The nature of chemical bonding at particular surface areas was evaluated by principal component analysis. The most prominent features of the PM-FT-IRRA spectra are the P–O and P&z.dbnd6;O stretching vibrations. It is shown that octadecanephosphonic acid is adsorbed both on Al2O3 and on Au. Moreover, PM-FT-IRRAS maps reveal areas of non-equivalent structural features. Lateral dimensions of these areas are in the micrometer range. Such non-equivalencies may control the inhibition potential of SAMs on ignoble metals, hence become crucial to the quality of products as biosensors or microelectronic components. [Copyright &y& Elsevier]

The high resolution far infrared absorption spectrum of IBr was recorded with a Fourier transform spectrometer. The fundamental 1-0 vibration-rotation band and the 2-1 and 3-2 hot bands were recorded at a resolution of 0.001 25 cm . The infrared continuum was provided by synchrotron radiation emission from the Max-I storage ring. For high resolution - 1 spectroscopy at 250 cm synchrotron radiation is about 5 times brighter than a conventional infrared glower. This increase in flux at the detector resulted in a corresponding increase in the signal-to-noise ratio and a much improved infrared spectrum. - 1. [ABSTRACT FROM AUTHOR]

Matrix isolation method allows investigating individual molecules and clusters. Basing on the registered spectra, one can obtain the information on cluster structures in n-hexanol and the changing of these structures during phase transitions. Using quantum chemical methods, the energy of hydrogen bonds for clusters of different sizes and their spatial parameters were calculated. A comparison of experimentally registered and theoretically calculated IR spectra of n-hexanol was made. [ABSTRACT FROM AUTHOR]

Abstract: The process of hydrogen-bonded cluster formation in methyl alcohol was investigated by FTIR spectroscopy using a matrix-isolation technique. Temperature dependence of the registered spectra of methanol trapped in an Ar matrix in the frequency region of O–H stretch fundamental was analyzed. The transformation of the FTIR bands of free O–H groups (3600–3800cm−1) into diffuse bands (3000–3600cm−1), which were assigned to the vibrations of the H-bonded hydroxyl groups in various clusters, was monitored in its initial stage at matrix heating from 10K to 50K. For the interpretation of the obtained experimental data the results of quantum-chemical simulation were used. The ab initio calculation was carried out at the DFT level of theory using the Gaussian 03 program with B3LYP potential and 6-31G(d) basis functions set. The similarity of the registered spectra of methanol trapped in the Ar matrix at 10–20K to the gas-phase spectra of methanol and their gradual transformation with matrix heating to the ones similar to the spectra of liquid methanol (at 40–50K) allows making the conclusion that such experiments may be considered as the proof of structural transformations in methyl alcohol during the phase transition from gas to liquid. [Copyright &y& Elsevier]

Abstract: Conformational diversity of the 1-heptene secondary ozonides (SOZ) in solid neat films as well as isolated in Ar or CO2 matrices was studied by the means of FT-IR absorption spectroscopy. The ozonization reaction was performed at 77K in the neat films of the reactants. The spectra of the ozonide were analyzed by combining the experimental data with the results of theoretical calculations performed at B3LYP 6-311++G (3df, 3pd) level. It was found that the samples of 1-heptene secondary ozonide exist as a mixture of three dominating conformers. The most stable conformer is the one with O–O half-chair configuration of the five membered ring, the aliphatic radical attached to the ring in equatorial position and the aliphatic chain being in gauche (∠OCCC≈−60°) position. The other two stable conformers are equatorial with aliphatic chain in anti (∠OCCC≈180°) and gauche (∠OCCC≈60°) positions. It was found from Van’t Hoff plots that ΔH of the equatorial anti conformer is equal to 0.24±0.03kJ/mol. The experimental value of ΔH is in reasonable accordance to the calculated one – 0.5kJ/mol. [Copyright &y& Elsevier]

• 1-methyl-germacyclohexane stable conformers that can be observed experimentally are 1C 4 axial (global minimum) and 1C 4 equatorial structures. • The conformational rearrangement path for the 1-methyl-1-germacyclohexane is: chair → half-chair → skew-boat → boat → skew-boat. • The heteroatom as well as substituent type influence the conformational stability of the six-member saturated cyclic molecules. The conformational analysis of newly synthesized compound, 1-methyl-1-germacyclohexane, is performed by means of a combined vibrational spectroscopy and theoretical methods. The liquid 1-methyl-1-germacyclohexane at room temperature is investigated using conventional ATR-FTIR, FT-IR (gas phase) and Raman methods. FT-IR spectra of the isolated in low-temperature neon and nitrogen matrices are registered. The further detailed vibrational conformational analysis is performed utilizing density functional theory and perturbation theory based methods. All possible 12 canonical ring conformations considering axial/equatorial CH 3 group position are analyzed by utilizing DFT/B3LYP, DFT/M06-2X and MP2 at aug-cc-pVTZ theory level. The most stable conformer with the global energy minimum structure in the chair axial conformation is investigated in detail. Analysis of the potential energy surface reveals transition states (TS) and energy barriers. The conformational path is found to be as follows: chair (1C 4)→ envelope/half-chair (TS)→ skew-boat (1S 3 - C 1 symmetry)→ boat (TS)→ skew-boat (1S 5 - C 2 symmetry). The energy barrier for 1C 4 (chair) to 1S 3 (skew-boat) conversion is 4.8 kcal/mol while for the reverse process equals to 0.5 kcal/mol. A similar conformational analysis is performed for different configurations of germacyclohexane, silacyclohexane and cyclohexane with mono- and disubstituents: CH 2 Cl, CH 3 , Cl and F. Such approach enables investigation of influence of the heteroatoms and substituents of various size and type on the structural parameters and conformational diversity. [ABSTRACT FROM AUTHOR]

Different configurations of (H 5 O 2)+ − Ar, (H 5 O 2)+ − Ne and (H 5 O 2)+ − He complexes were calculated using DFT methods and series of Dunning and Pople basis sets. The possibility of the existence of an equilibrium configuration with C 2 symmetry for complexes analyzed was in focus of the studies carried out. DFT methods that do not take into account dispersion interactions, as a rule, define (H 5 O 2)+ − X (X = Ar, Ne, He) configurations with C 2 symmetry as transitional states. At the same time, such DFT methods as B1B95, B98, and WB97X make it possible to determine geometric parameters of these complexes with C 2 symmetry in equilibrium configurations. Taking into account dispersion interactions in the framework of D3 Grimme approach and using density functionals, including dispersion interactions (such as M06-2X, wB97XD, etc.), leads to the situation, when configurations of the complexes such as (H 5 O 2)+ − X (X = Ar, Ne, He) with C 2 symmetry calculated using most of the basis sets turn out to be equilibrium. However, calculations within the framework of MP2, MP4, and CCSD (T) methods determine configurations of complexes with C 2 symmetry as transition states, while the experimental data on the IR spectra of (H 5 O 2)+ − Ar complex probably point out to the existence of an equilibrium configuration of this complex with C 2 symmetry. In addition to structural analysis for equilibrium configurations found, IR spectra were calculated in harmonic and in some cases also in anharmonic approximations. Calculated IR spectra were compared to protonated water dimer IR spectra calculated at the same level of theory in equilibrium configuration and in the transition state. • The structures of the PWD + X (X = Ar,·Ne, He) complexes with C 2 symmetry were predicted. • Simulated IR spectra of the PWD + X complexes with C 2 and C 1 symmetries were compared. • All IR bands in 850–1100 cm−1 spectral region of the PWD + Ar complex were assigned. [ABSTRACT FROM AUTHOR]

Abstract Effects of the dispersion interactions on the parameters of the water dimer equilibrium configuration and IR spectra are analyzed in the paper. Dimer equilibrium geometry was calculated using a series of the density functionals, both with (B3LYP-D3, B2PLYPD, B2PLYP-D3, mPW2PLYPD, wB97XD) and without (B3LYP, B2PLYP, mPW2PLYP, wB97X) accounting of the dispersion interactions and using density functional M-06-2X that include the dispersion interaction effects. For the determined equilibrium configurations of the water dimer, IR spectra in harmonic and anharmonic (VPT2) approximations were calculated at the corresponding levels of theory. Additional analysis of the donor hydroxyl group vibrations was performed using the 3D potential energy surfaces, calculated at B3LYP/cc-pVTZ, B3LYP-D3/cc-pVTZ, B2PLYP/cc-pVTZ, B2PLYPD/cc-pVTZ, M06-2X/cc-pVTZ, wB97XD/cc-pVTZ levels of theory. Moreover, double anharmonic couplings of the analyzed modes with other vibrational modes were accounted using the "hybrid" method. Comparison of the calculated results with the experimental and theoretical data from the literature was performed. Highlights • Anharmonic calculations of WD configurations and IR spectra were performed at different levels of theory. • Effects of the dispersion interactions on the parameters of WD equilibrium configuration and IR spectra were analyzed. • Analysis of the donor hydroxyl group vibrations was also performed using the 3D PES, calculated in different approximations. • Double anharmonic interactions of donor OH group vibrations with other vibrational modes were taken into account. [ABSTRACT FROM AUTHOR]

Abstract Polymer composite materials are used increasingly in material and engineering science. They provide outstanding mechanical and optical properties. The linkage between the polymer materials is crucial for achieving the desired properties. Understanding the linkage and structure of the polymer-polymer interface layer is a key for utilization polymer composite materials as well as for their fabrication. When analyzing the thin polymer-polymer interface it is important to achieve clear identification of molecular linker structures. One reliable analytical technique allowing this is surface enhanced Raman scattering (SERS) spectroscopy. This study aims at the in-situ evaluation of SERS spectra recorded from the Polycarbonate (PC) –Octadecylamine (ODA) interface to identify the formation of urethane bonds. The detailed analysis of SERS spectra taken before and after the chemical linkage reaction reveals the formation of urethane structures, indicating a chemical bond between PC and ODA. The spectral pattern of urethane groups was identified and evaluated by a reference Raman spectrum. Graphical abstract Image 1 Highlights • Nondestructive in-situ characterization of polymer interphase by SERS. • Silver nanoparticles located at the polymer interface. • Evaluation of molecular interphase structure between Polycarbonate-Octadecylamine. • Formation of an initial urethane linkage. [ABSTRACT FROM AUTHOR]

Raman spectra of liquid water and ice were measured at different temperatures. The intensity of the band assigned to bending vibrations of water molecules was observed to decrease at the liquid-to-solid transition, while the Raman line near 2200 cm −1 showed an anomalously high intensity in the solid phase. A tetrahedral model was used for computer analysis of the observed spectral changes. Quantum-chemical calculations of the structure, normal vibrations and Raman spectra in the harmonic approximation, as well as frequencies and intensities of some vibrations using 1D and 2D potential energy surfaces, were carried out using B3LYP with the cc-pVTZ basis set. The influence of the number of hydrogen bonds on the frequency and Raman activity of the bending vibrations was analyzed. The possibility of hydrogen bond weakening upon excitation of the combined bending-rocking vibration due to the large amplitude of this vibration is considered. [ABSTRACT FROM AUTHOR]

We present a novel approach for detection of cancerous kidney tissue areas by measuring surface enhanced Raman scattering (SERS) spectra of extracellular fluid taken from kidney tissue. The method is based on spectral analysis of the cancerous and normal tissue areas in order to find the specific spectral markers. The samples were prepared by sliding the kidney tissue over a substrate-calcium fluoride optical window. For producing the SERS signal, the dried extracellular fluid film was covered by silver nanoparticle colloidal solution. In order to suppress fluorescence background, the measurements of the dried samples were performed in the NIR spectral region with the Raman excitation wavelength of 1,064 nm. The most significant spectral differences-spectral markers-were found in the wavenumber region between 400 and 1,800 cm−1, where spectral bands related to various vibrations of carbohydrates, amino acids, and nucleic acids are located. Spectral markers in the SERS spectra are different from those in IR absorption spectra. The SERS spectroscopic method has a potential to be used directly during the surgery. [ABSTRACT FROM AUTHOR]

Intermolecular hydrogen bonding, which is formed between water molecules in the condensed state, causes a variety of unique properties of liquid water. In this paper the results of experimental FT IR studies of water trapped in an Ar matrix as well as condensed water at temperatures from 133 to 293 K are presented. It is shown that the temperature evolution of the FTIR-spectra of water trapped in low-temperature matrices can be considered as an experimental model of the structure transformation of water during the phase transition from gas phase to condensed confined water. The comparison of the vibrational spectra of water in matrix isolation with the corresponding spectra of condensed water gives information about the peculiarities of H-bonded structures of water. [ABSTRACT FROM AUTHOR]

The structure and harmonic and anharmonic IR spectra of the protonated water dimer (PWD) were calculated in C 1, C 2, and C s symmetry at the MP4/acc-pVTZ level of theory. We found that structure and IR spectra are practically identical in C 2 and C 1 symmetry, demonstrating that an equilibrium C 1 configuration of the PWD is not realized. Anharmonic coupling of the shared proton stretching vibration with all other modes in the PWD in C 2 and C s symmetry was the focus of this investigation. For this purpose, 28 two-dimensional potential energy surfaces (2D PES) were built at the MP4/acc-pVTZ level of theory and the corresponding vibrational Schrödinger equations were solved using the DVR method. Differences in the coupling of the investigated mode with other modes in the C 2 and C s configurations, along with some factors that determine the red- or blue-shift of the stretching vibration frequency, were analyzed. We obtained a rather reasonable value of the stretching frequency of the bridging proton (1058.4 cm-1) unperturbed by Fermi resonance. The Fermi resonance between the fundamental vibration ν7 and the combined vibration ν2 + ν6 of the same symmetry was analyzed through anharmonic second-order perturbation theory calculations, as well as by 3D PES constructed using Q 2, Q 6, and Q 7 as normal coordinates. A significant (up to 50%) transfer of intensity from the fundamental vibration to the combined one was found. We have estimated the frequency of the bridging proton stretching vibration in the C s configuration of the PWD based on calculations of the intrinsic anharmonicity and anharmonic double modes interactions at the MP4/acc-pVTZ level of theory (1261 cm-1). [ABSTRACT FROM AUTHOR]

• 1-chloromethyl-1-fluorosilacyclopentane is a newly synthesized molecule. • Theoretical calculations reveal: twisted trans as the most stable conformer and twisted gauche– and twisted gauche+ structures as local energy minimas. • Experimental and theoretical studies confirm the presence of at least three conformers. • The energy barrier for the 2T3 to 3T2 ring inversion via envelope is 4.01 kcal/mol. 1-chloromethyl-1-fluorosilacyclopentane (1-ClM-1-FSiCP) was synthesized for the first time and investigated by means of vibrational spectroscopy and theoretical calculations. FT-IR and Raman spectroscopic methods were implemented to collect vibrational spectra of 1-ClM-1-FSiCP. The conformational analysis was performed utilizing FT-IR matrix isolation technique and theoretical methods such as density functional theory and ab initio calculations. The spectra of the 1-ClM-1-FSiCP isolated in the argon and nitrogen matrices, were collected before and after the annealing process. During the conformational analysis the envelope (E) and twisted (T) ring shapes with the position of the fluorine atom and chloromethyl group in terms of axial/equatorial and cis/trans/gauche-/gauche+ positions were investigated utilizing MP2/aug-cc-pVTZ and DFT/B3LYP/aug-cc-pVTZ level of theory. Results indicate three stable conformers: twisted trans (global energy minimum), twisted gauche– and twisted gauche+. The potential energy surface scans were performed to trace the energy changes and the presence of transition state structures during ring conversion and rotation of the CH 2 Cl group. [ABSTRACT FROM AUTHOR]

A new mechanism for combinatorial broadening of donor-OH stretching-vibration absorption bands in molecular clusters with H-bonds is proposed. It enables the experimentally observed increase of the O-H stretching-vibration bandwidth with increasing number of molecules in H-bonded clusters to be explained. Knowledge of the half-width of the OH stretching-vibration absorption band in the dimer and the number of H-bonds in the analyzed cluster is suffi cient in the zeroth-order approximation to estimate the O-H stretching-absorption bands in clusters containing several molecules. Good agreement between the calculated and published experimental half-widths of the OH stretching-vibration absorption bands in MeOH and PrOH clusters was obtained using this approach. [ABSTRACT FROM AUTHOR]

Uric acid concentration in human bodily fluids is an important marker for disorders such as gout, pre-eclamsia or cardiovascular disease. However, currently used methods for its detection either lack sensitivity or require sophisticated, bulky and expensive equipment. In this work, we show that by using surface-enhanced Raman scattering spectroscopy (SERS) on dried Ag colloidal drops and with 1064 nm excitation, concentrations of uric acid in aqueous solutions down to 10−6 M can be detected. Such sensitivity is sufficient for medical applications as concentration of uric acid in various bodily fluids are in the range of 10−3-10−4 M. Drying of the colloidal drops is known to result in the formation of 'coffee-ring' structures that allow obtaining high enhancements but poor reproducibility. Here, the formation of the structures was avoided by choosing aluminum oxide as a base substrate and by controlling environment conditions. Despite the fact that variations of signal enhancement from sample to sample prevent quantitative analysis from being performed, the results of this work imply that strict control of sample preparation conditions could lead to obtaining reproducible SERS enhancements. Results of density functional theory calculations of uric acid tautomer - five-atom silver cluster complexes performed for the first time show that the differences between Raman and SERS spectra of uric acid can be mainly explained by tautomerization of the molecule and its bonding to the silver surface. Assignment of spectral bands is important for correct SERS signal interpretation and detection of uric acid in biological fluids in the future studies. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The structure and IR absorption spectrum of the formic acid dimer (FAD) were calculated using the B3LYP DFT functional and cc-pVTZ basis set. Matrices of force and anharmonic constants were calculated in order to find the fundamental frequencies more accurately. The 1D and 2D potential energy surfaces (PES) were built using symmetry coordinates and stretching coordinates of С Н and O H bonds. For O H stretching coordinates, the 2D PES were built with and without optimization of the remaining geometric parameters. It was shown that in the second case besides the global minimum, an additional local minimum on the unrelaxed PES is formed with the energy more than 4000 cm −1 higher than the energy of the ground state. A numerical solution of Schrödinger equations gives the values of O H and C H stretching vibrations. Comparison of the obtained theoretical results with the experimental data presented in the literature allowed us to make new assignments for IR and Raman spectral bands related to hydroxyl groups stretching vibrations in FAD. [ABSTRACT FROM AUTHOR]

Abstract: Long-wave Raman spectra of some normal alcohols (from n-pentanol to n-decanol) in the liquid phase were registered. The regularities in the dependencies of Raman bands frequencies on the number of carbon atoms in the hydrocarbon chain were deduced. The calculations of Raman spectra of the studied molecules, their equilibrium structures and possible conformers were carried out in the approximation B3LYP/cc-pVDZ. These results in combination with the analysis of literature data allowed to explain the observed regularities in Raman band positions in the spectral range of 200–600сm−1 and their shifts upon increasing length of the chains. It was found that the plane configurations dominate in the liquid phase for molecules with short- and moderate-chain lengths. The elongation of the chain leads to the decrease of the fraction of plane conformers and in n-decanol the plane structure is completely absent. [Copyright &y& Elsevier]

Highlights: [•] Two conformers of PyO⋅TCA complex in acetonitrile with short hydrogen bond were found. [•] For conformers IR spectra were calculated in harmonic and anharmonic approximations. [•] 1–3D PES for the motion of the hydrogen atom in both conformers were build. [•] Frequencies of OH vibrations were found by numerical solution of Schrödinger equation. [•] We analyzed increasing of anharmonicity while solving PyO⋅TCA complex in acetonitrile. [ABSTRACT FROM AUTHOR]

Low-temperature infrared absorption spectra are obtained for ethanol isolated in an argon matrix at temperatures of 20-45 K range for ratios of the numbers of the molecules being studied to the numbers of matrix atoms of 1:1000 and 1:2000. A preliminary interpretation of the spectra is obtained on the basis of the temperature variations in the spectra and published data. The structure of the ethanol conformers, rotational constants, and internal rotation barriers of the methyl and hydroxyl groups are calculated in the B3LYP/cc-pVQZ approximation. The harmonic and anharmonic IR spectra of the gauche- and trans-conformers are calculated in the same approximation. The force fields of the two conformers and the distributions of the potential energy of the normal vibrations are calculated and compared for a general set of dependent coordinates. Anharmonicity effects are taken into account by introducing spectroscopic masses for the hydrogen atoms when calculating the normal vibrations in the harmonic approximation. [ABSTRACT FROM AUTHOR]

Abstract: Distribution of chemical components in the mixed oxalatic, phosphatic and uratic urinary stones was analysed by means of infrared microspectroscopy. The specular reflection from the surface of the cross-sectioned stones was used for the infrared spectroscopic imaging. It was found that the reflection spectra consist from specular and diffuse reflection components and the former one exhibit Reststrahlen bands which resemble first derivative of the spectral bands in the absorption spectrum. In order to use the measured spectra for the chemical imaging they were corrected for asymmetry by subtracting the diffuse reflection component and applying Kramers–Kronig transform to the specular reflection component. The Kramers–Kronig transformed spectrum was then combined with the diffuse reflection component. Spectra corrected in this manner were used to create false-colour images of the stones. It was found that the images obtained after applying the correction procedure to the spectra differ substantially from the ones obtained from the raw spectra. They are in good agreement with the stones’ images obtained from the FT-Raman spectra. [Copyright &y& Elsevier]

The silver nanoparticle colloid was used to obtain surface enhanced Raman spectra of Listeria monocytogenes, Salmonela enterica, and Esherichia coli bacteria. The SERS spectra were captured using for excitation the near-infrared (1064 nm) laser radiation with reduced intensity, which ensured the prevention of the fluorescence background as well as photo- and thermal decomposition of the samples. It was found that the optimal size of silver nanoparticles for the enhancement of the Raman signal in the near-infrared spectral region is ca. 50 nm. The spectral data obtained in this study indicate that relative intensities of SERS spectral bands of bacteria can be used for spectral differentiation of bacteria. In case of Listeria, Salmonela, and Esherichia cells, the intensity ratio of spectral bands of adenine and cysteine can be used as a spectral marker for differentiation of the bacteria. [ABSTRACT FROM AUTHOR]

• 1‑chloro-1-chloromethylsilacyclohexane is a newly synthesized molecule. • Theoretical calculations reveal axial trans as the most stable conformer. • Experimental and theoretical studies confirm the presence of at least four conformers. • The conformational path is: chair→ envelope/half-chair like→ skew-boat → boat → skew-boat. 1‑chloro-1-chloromethylsilacyclohexane (1-Cl-1-ClMSiCH) is a newly synthesized molecular compound whose conformational analysis was performed by means of vibrational spectroscopy and theoretical calculations. Conventional ATR-FTIR and Raman spectroscopic methods were used to obtain vibrational spectra of the liquid sample. Additionally, FTIR spectra of the compound isolated in low-temperature neon and nitrogen matrices were registered to make a complete assignment of the experimental vibrational spectral bands. All theoretically possible 38 canonical ring conformations considering axial/equatorial and cis/trans/gauche-/gauche + positions of the Cl and CH 2 Cl group were analyzed by utilizing MP2 and B3LYP at aug-cc-pVTZ theory level. The most stable local energy minima were investigated in detail, with the global energy minimum structure being in the chair axial trans conformation. Detailed analysis of the potential energy surface revealed the transition states (TS) and the energy barriers. The conformational path was found to be the chair→ envelope/half-chair (TS)→ skew-boat C 1 → boat (TS)→ skew-boat C 2. The energy barrier for 1C 4 to 1S 3 conversion was found to be 4.94 kcal/mol while for the reverse process–it was calculated to be 0.26 kcal/mol. The vibrational analysis and the experimental spectra suggest that the four lowest energy (chair ring) conformers coexist at room temperature. The energy barrier for gauche to trans conversion is 1.15 kcal/mol for axial and 1.04 kcal/mol for equatorial conformers, and it is possible to observe these processes in low-temperature matrices. [ABSTRACT FROM AUTHOR]

Since 1-chloromethyl-1-fluorosilacyclohexane is a newly synthesized molecular compound its structural parameters and conformational stability is unknown. Raman and infrared vibrational spectroscopy methods were employed for analysis of this molecule. IR spectra were recorded for both gas phase and liquid sample, whereas the Raman experiments were performed in the liquid state. Additionally, low temperature matrix isolation infrared spectra were recorded after isolating the molecule in argon and nitrogen matrices. For the assignment of the experimental spectral bands, theoretical DFT/B3LYP/aug-cc-pVDZ and MP2/aug-cc-pVDZ calculations were performed. From the calculations it was found that 1-chloromethyl-1-fluorosilacyclohexane may exist in twelve different conformational forms out of which the chair axial trans conformer is the most stable form. However, there are three more chair type conformers – equatorial trans , equatorial gauche and axial gauche that are stable enough to be observed in the experimental spectra. • 1-Chloromethyl-1-fluorosilacyclohexane is a newly synthesized molecule. • Theoretical calculations reveal axial trans as the most stable conformer. • Experimental studies confirm the presence of at least three conformers. • Conversion between conformers is observed in nitrogen matrix upon annealing. [ABSTRACT FROM AUTHOR]