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The structural integrity, elasticity, and fluidity of lipid membranes are critical for cellular activities such as communication between cells, exocytosis, and endocytosis. Unsaturated lipids, the main components of biological membranes, are particularly susceptible to the oxidative attack of reactive oxygen species. The peroxidation of unsaturated lipids, in our case 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), induces the structural reorganization of the membrane. We have employed a multi-technique approach to analyze typical properties of lipid bilayers, i.e., roughness, thickness, elasticity, and fluidity. We compared the alteration of the membrane properties upon initiated lipid peroxidation and examined the ability of flavonols, namely quercetin (QUE), myricetin (MCE), and myricitrin (MCI) at different molar fractions, to inhibit this change. Using Mass Spectrometry (MS) and Fourier Transform Infrared Spectroscopy (FTIR), we identified various carbonyl products and examined the extent of the reaction. From Atomic Force Microscopy (AFM), Force Spectroscopy (FS), Small Angle X-Ray Scattering (SAXS), and Electron Paramagnetic Resonance (EPR) experiments, we concluded that the membranes with inserted flavonols exhibit resistance against the structural changes induced by the oxidative attack, which is a finding with multiple biological implications. Our approach reveals the interplay between the flavonol molecular structure and the crucial membrane properties under oxidative attack and provides insight into the pathophysiology of cellular oxidative injury.

In this study, a series of uridine (U) and 2′-deoxyuridine (dU) conjugates containing an isomeric ortho-, meta- or para-carborane cluster (C2B10H12) attached at C-5 through an ethynyl linker were synthesized. The effect of carborane cluster isomerism on the conjugate syn/anti conformation, molar extinction coefficient, lipophilicity, susceptibility to phosphorylation (by TK1, TK2 and dCK), cytotoxicity and antiviral activity was evaluated. A strong effect of the boron cluster modification on the syn/anti equilibrium of the modified nucleosides was observed. An increase in lipophilicity compared with unmodified U and dU, especially for conjugates bearing a para-carborane cluster, was detected. Furthermore a pronounced and differential influence of the boron cluster modification on the electronic properties of the nucleobase chromophore was observed. The obtained conjugates have low or medium toxicity toward several cell lines, are phosphorylated fairly well by TK1 and are poor or not substrates for dCK. Furthermore, the conjugates preferentially inhibit HCMV replication with an SI index as high as 22 for the ortho-carborane derivative of U and more than 180 for the para-carborane derivative of dU.

Detailed vibrational assignments for twelve flavonoids (seven flavones (flavone, 3- and 5-hydroxyflavone, chrysin, apigenin, fisetin and luteolin) and five flavonols (galangin, kaempferol, quercetin, morin and myricetin)) have been made based on own and reported experimental data and calculations at the B3LYP/6-31 + G(d,p) level of theory. All the molecules are treated in a uniform way by using the same set of redundancy-free set of internal coordinates. A generalized harmonic mode mixing is used to corroborate the vibrational characteristics of this important class of molecules. Each flavonoid molecule can be treated from the vibrational point of view as made of relatively weakly coupled chromone and phenyl part. It has been shown that the strongest band around 1600 cm− 1 need not be attributable to the C O stretching. The way the vibrations of any of the hydroxyl groups are mixed with ring vibrations and vibrations of other neighboring hydroxyl groups is rather involved. This imposes severe limitations on any attempt to describe normal modes of a flavonol in terms of hydroxyl or carbonyl group vibrations. The role of water molecules in the appearance of flavonoid IR spectra is emphasized. Knowing for the great affinity of phosphate groups in lipids towards water, the immediate consequence is a reasonable assumption that flavonoid lipid interactions is mediated by water.

(-)-trans-Δ9- tetrahydrocannabinol (THC) and (-)-cannabidiol (CBD) are natural cannabinoids found in cannabis plant which interact with cannabinoid receptors in human body. THC is primary psychoactive compound while CBD is non-psychotropic constituent, i.e. they have different receptor activity, function, and physiological effects. These dramatic differences in their behavior are derived from not so dramatic differences in their structures. Calculations of the structures and infrared and Raman spectra of all THC and CBD conformers were performed by means of density functional theory (DFT) at the B3LYP-D3BJ/6-31+G(d,p) level. Conformational flexibility due to the presence of alkyl (pentyl) side chain was thoroughly investigated and shown to be weakly dependent on the molecular frame . The result of the QSAR analysis by Keimowitz et al. J. Med. Chem. 43 (2000) 59–70 that for optimum affinity and potency the side chain must have conformational flexibility to fold over and thus come with its end methyl group close to the phenolic ring was examined with respect to the energies needed for such transformation. Assignments of the observed vibrational spectra reported in the literature were made by attempting to have a strong calculated band assigned to the strong observed band lying in the same narrow wavenumber interval. Evidences for intra- and intermolecular hydrogen bonding in CBD based on experimental and calculated data are given.

Superparamagnetic magnetite nanoparticles (MNPs) with excellent biocompatibility and negligible toxicity were prepared by solvothermal method and stabilized by widely used and biocompatible polymer poly(ethylene glycol) PEG-4000 Da. The unique properties of the synthesized MNPs enable them to host the unstable and water-insoluble quercetin as well as deliver and localize quercetin directly to the desired site. The chemical and physical properties were validated by X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE–SEM), atomic force microscopy (AFM), superconducting quantum interference device (SQUID) magnetometer, FTIR spectroscopy and dynamic light scattering (DLS). The kinetics of in vitro quercetin release from MNPs followed by UV/VIS spectroscopy was controlled by employing combined stationary and alternating magnetic fields. The obtained results have shown an increased response of quercetin from superparamagnetic MNPs under a lower stationary magnetic field and s higher frequency of alternating magnetic field. The achieved findings suggested that we designed promising targeted quercetin delivery with fine-tuning drug release from magnetic MNPs.

Flavonoids, polyphenols with anti-oxidative activity have high potential as novel therapeutics for neurodegenerative disease, but their applicability is rendered by their poor water solubility and chemical instability under physiological conditions. In this study, this is overcome by delivering flavonoids to model cell membranes (unsaturated DOPC) using prepared and characterized biodegradable mesoporous silica nanoparticles, MSNs. Quercetin, myricetin and myricitrin have been investigated in order to determine the relationship between flavonoid structure and protective activity towards oxidative stress, i.e., lipid peroxidation induced by the addition of hydrogen peroxide and/or Cu2+ ions. Among investigated flavonoids, quercetin showed the most enhanced and prolonged protective anti-oxidative activity. The nanomechanical (Young modulus) measurement of the MSNs treated DOPC membranes during lipid peroxidation confirmed attenuated membrane damage. By applying a combination of experimental techniques (atomic force microscopy&mdash, AFM, force spectroscopy, electrophoretic light scattering&mdash, ES and dynamic light scattering&mdash, DLS), this work generated detailed knowledge about the effects of flavonoid loaded MSNs on the elasticity of model membranes, especially under oxidative stress conditions. Results from this study will pave the way towards the development of innovative and improved markers for oxidative stress-associated neurological disorders. In addition, the obtained could be extended to designing effective delivery systems of other high potential bioactive molecules with an aim to improve human health in general.

In this study, a series of uridine (U) and 2'-deoxyuridine (dU) conjugates containing an isomeric ortho-, meta- or para-carborane cluster (C

Elevated amounts of copper are considered to be contributing factor in the progression of neurodegenerative diseases as they promote oxidative stress conditions. The aim of our study was to examine the effects of ethanolic extract of propolis (EEP) against copper-induced neuronal damage. In cultured P19 neuronal cells, EEP exacerbated copper-provoked neuronal cell death by increasing the generation of reactive oxygen species (ROS) and through the activation of caspase-3/7 activity. EEP augmented copper-induced up-regulation of p53 and Bax mRNA expressions. Neurotoxic effects of EEP were accompanied by a strong induction of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) expression and decrease in the expression of c-fos mRNA. SB203580, an inhibitor of p38 mitogen-activated protein kinase (MAPK) prevented detrimental effects of EEP, whereas SP600125, an inhibitor of c-Jun N-terminal kinase (JNK), exacerbated EEP-induced neuronal cell death. Quercetin, a polyphenolic nutraceutical, which is usually present in propolis, was also able to exacerbate copper-induced neuronal death. Our data indicates a pro-oxidative and apoptotic mode of EEP action in the presence of excess copper, wherein ROS/p53/p38 interactions play an important role in death cascades. Our study also pointed out that detailed pharmacological and toxicological studies must be carried out for propolis and other dietary supplements in order to fully recognize the potential adverse effects in specific conditions.

The conformational preference (trans-s-cis vs. trans-s-trans) of chalcone in two solvents (tetrachloroethene and acetonitrile) and in the solid phase was studied experimentally by IR and Raman spectroscopy and theoretically within the polarizable continuum model (PCM) (at the B3LYP/6-31 + G(d,p) level, in vacuo and in ten solvents ranging from er = 1.4 to er = 35.7). From the temperature dependent IR measurements of chalcone in tetrachloroethene (er = 2.268) the conformational enthalpy difference was obtained ΔH0 = +(1.01 ± 0.03) kcal mol−1. The calculated value of 1.39 kcal mol−1 for tetrachloroethene solvent (er = 2.268) is quite close. In acetonitrile the obtained enthalpy difference was negative, ΔH0 = −(1.4 ± 0.3) kcal mol−1 in contrast to the calculated positive value of 1.10 kcal mol−1. A thorough normal coordinate analysis was performed in terms of redundancy-free internal coordinates making full use of local symmetries. It is demonstrated that bands usually attributed either to carbonyl C O or ethylenic C C bond stretching are correctly described only as combinations of the two stretchings. This is important because explanations of the various experimental observations must accordingly be modified. For example, the solvent induced wavenumber shifts or intensity changes of the 1670 cm−1 band are not related exclusively to the properties of the carbonyl bond.

Three refractive index mixing rules, Arago–Biot, Lorentz–Lorenz, and Newton, are generalized to complex refractive index and used to define infrared (IR) spectra of the corresponding ideal liquid mixtures. Using the measured optical constants n and k for acetonitrile-water mixtures (Bertie and Lan, 1997) the excess absorbances, AE = Aobs − Aideal, are calculated. Relying upon the well-established properties of the acetonitrile–water mixtures, the interpretation of the excess absorbances is established that is essentially based on the understanding of a liquid as a set of oscillators. The set depends on the composition of the mixture and comprises oscillators as present in the pure components and oscillators perturbed by hydrogen bonding between unlike molecules. The main features of an excess spectrum can be established assuming chemical equilibria among various oscillators. The most informative parts of the spectrum of a yet unstudied binary system can well be observed and even qualitatively explained from the excess absorbance provided: first, a detailed vibrational study of the components has been done; and, second, it is well understood what actually is subtracted from Aobs. As examples, the binary mixtures of ethynylbenzene and tetrachloroethylene and 2-ethynylpyridine and tetrachloroethylene are considered.

Linear low density polyethylene (PE-LLD) and cast polypropylene (PPcast) films were irradiated in a 60Co γ-source. The total irradiation dose varied from 0 kGy (unirradiated samples) to 200 kGy. Oxygen transport was investigated by a manometric method and the structural changes were studied by differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). Free radicals decay as a function of time was monitored by electron spin resonance (ESR) spectroscopy. The results show that the γ-irradiation reduces oxygen permeability coefficient in both films. The reduction was associated with an increase in crystallinity. DSC thermograms revealed a decrease in PPcast melting point with increasing irradiation dose, indicating higher degradation compared to PE-LLD. The observed peak in FTIR spectra for both samples at 1716 cm−1 corresponds to the stretching of the carbonyl and carboxylic groups which arise from the reaction of oxygen with the free radicals produced in the polymer matrix as a result of irradiation.

The electronic charge redistribution and the infrared intensities of the two types of intramolecular hydrogen bonds, O–H···O and O– H···π, of o-hydroxy- and o-ethynylphenol, respectively, together with a set of related intermolecular hydrogen bond complexes are described in terms of atomic charges and charge fluxes derived from atomic polar tensors calculated at the B3LYP/cc-pVTZ level of theory. The polarizable continuum model shows that both the atomic charges and charge fluxes are strongly dependent on solvent. It is shown that their values for the OH bond in an intramolecular hydrogen bond are not much different from those for the “free” OH bond, but the changes are toward the values found for an intermolecular hydrogen bond. The intermolecular hydrogen bond is characterized not only by the decreased atomic charge but also by the enlarged charge flux term of the same sign producing thus an enormous increase in IR intensity. The overall behavior of the charges and fluxes of the hydrogen atom in OH and ≡CH bonds agree well with the observed spectroscopic characteristics of inter- and intramolecular hydrogen bonding. The main reason for the differences between the two types of the hydrogen bond lies in the molecular structure because favorable linear proton donor–acceptor arrangement is not possible to achieve within a small molecule. The calculated intensities (in vacuo and in polarizable continuum) are only in qualitative agreement with the measured data.

A simple IR spectroscopy based methodology in routine screening studies of polymorphism is proposed. Reflectance and transmittance temperature-dependent IR measurements (coupled with the 2D-IR data presentation and the baseline analysis) offer a positive identification of each polymorphic phase, therefore allowing simple and rapid monitoring of the measured system. Applicability and flexibility of the methodology was demonstrated on the measurement of the model polymorphic compound paracetamol under various conditions (including geometric constraints and elevated pressure). The thermal behavior of paracetamol strongly depends on slight variations in experimental conditions that can result in formation of various phases (three polymorphs and the amorphous form). The amorphous phase can crystallize during heating into either Form II or Form III within almost identical temperature range. Likewise, the crystal transformations II → I and III → II also can proceed within almost identical temperature range. Furthermore, the thermal behavior is even more diverse than that, and includes the crystallizations of Forms I, II and III from the melt, and the high temperature II → I transition. The variety of the temperatures of the transformations is a major obstacle for unambiguous identification of a particular phase by DSC and a major reason for the implementation of these IR methods.

Two series of thin films of polyether-based polyurethane–silica nanocomposites having hard segment content of 51% and 34% and different concentrations of SiO2 nanoparticles (0, 0.5, 1.0 and 3.0 vol.%) have been prepared. Infrared linear dichroic (LDIR) ratio, mechanical and differential scanning calorimetry (DSC) measurements were performed in order to determine the influence of hydrogen bonding on their mechanical and thermal properties. The degree of phase separation (DPS) and orientational functions in dependence on strain were calculated from the polarized IR spectra. The presence of silica nanoparticles gives rise to significant differences in the mechanical (stress–strain) properties of the nanocomposites with regard to the pure polymer. The nanocomposite thin films with lower hard segment content (HSC) displayed decreased stiffness and tensile and increased elongation at break in comparison to the nanocomposites with higher HSC. There was no distinctive influence of nanoparticles on the glass transition temperatures of soft segments. Nanosilica significantly affected the melting behavior of the hard phase only in samples with higher HSC.

Intra- and intermolecular hydrogen bonding of 1, 1' -bi-2-naphthol in a series of solvents and in solid phase has been investigated by means of mid-IR spectroscopy and DFT reaction field calculations. The polarizable continuum model has been used to estimate the relative stability of isomers differing in the positions of the hydroxyl groups. The height of the potential barriers between them was also calculated and the corresponding transition states characterized. In hydrogen bond nonaccepting solvents, the isomer preference does not change relative to the gas phase, although the less stable isomers are more probable in solvents of higher relative permittivity. In hydrogen bond forming solvents, the least stable isomer is most probably prevalent due to the additional stabilization through intermolecular hydrogen bonds with solvent molecules. A detailed vibrational analysis revealed the spectral regions specific to the OH vibrations with the observed solvent effects concerning the redistribution of vibrational intensities rather than wavenumber shifts.

Morphological, mechanical, and Fourier transform infrared dichroic investigations were performed on neat polyurethane (PU) polymer matrix and PU+CaCO3 nanocomposite thin films to determine how the nanofiller influenced the mechanical properties. The measurements were performed on strips that were cut from the prepared films in parallel and perpendicular directions with respect to the direction of film preparation. Optical microscopy of PU and the PU+CaCO3 nanocomposite revealed the strain-induced transition from a continuous spherulitic morphology to a fiberlike structure. The stress–strain behavior of the neat PU and PU+CaCO3 nanocomposite films showed significant differences at large strain regimes. The experimental results suggest that the mechanical properties were strongly related to the orientational behavior of the separated phases. The orientation of the hard and soft segments was analyzed by the orientation function calculated from the IR absorbances. A correlation between the orientations of segments, tensile properties, and hardness of the investigated polymer films was established. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The interactions between hydrophobic or semihydrophobic gold and silver nanoparticles (NPs) and a dimyristoylphosphatidylcholine (DMPC) bilayer as a model cell membrane in two ionic solutions result in the structural reorganization within the bilayer manifested as locally increased nanomechanical compaction in the vicinity of NP clusters as well as changed overall thermotropic properties. The effects of NP surface charge and hydrophobicity were examined using AFM imaging, force spectroscopy and IR spectroscopy. The NP clustering occurred during hydration process of dry films containing both the DMPC molecules and the NPs by the mechanism in which the number of bilayer deformations was reduced by NP clustering. The force spectroscopy showed increased bilayer density around (semi)hydrophobic NP clusters and thus locally increased lateral compaction of the bilayer. The strengthening effect was observed for both the silver and the gold NPs in a high ionic strength solution such as seawater, while it was absent under physiological conditions. The local lipid rearrangement induces the long-range lipid reorganization resulting in the bilayer phase transition shifting toward lower or higher temperatures depending on the solution ionic strength (at the most by -1.0 °C in phosphate buffered saline and at the most by +0.5 °C in seawater).

Satureja hortensis L. unifloral honey was characterized by pollen analysis, electrical conductivity, pH and extensively by chromatographic and spectroscopic techniques. UV / VIS spectro-scopy measurements revealed total phenol content of 682.1 mg GAE / kg by Folin-Ciocalteu assay, antiox-idant capacity by DPPH assay of 1.7 mmol TEAC / kg and by FRAP assay of 4.3 mmol Fe2+ / kg as well as CIE L*a*b*Cab*h°ab chromaticity coordinates. GC-MS after headspace solid-phase microextraction (HS-SPME) revealed hotrienol (22.8 %) along with other linalool derivatives, benzaldehyde (6.1 %), phenylacetaldehyde (4.9 %) and few norisoprenoids (safranal (7.6 %) as the major). Ultrasonic solvent ex-traction (USE) followed by GC-MS allowed identification of methyl syringate (54.7 %) as predominant compound along with other benzene derivatives. HPLC-DAD analysis determined tyrosine (382.0 mg kg−1), phenylalanine (140.4 mg kg−1) and methyl syringate (39.32 mg kg−1). Methyl syringate and hotrienol can be considered non-specific chemical markers of S. hortensis honey. FTIR-ATR spectral characteristics of S. hortensis honey in fingerprinting region were not significantly different from other honey types, but the integrated intensity of the region was smaller than in other unifloral honeys.

We study several molecules that could help in the solution of the missing sulfur problem in dense clouds and circumstellar regions, as well as in the clarification of the sulfur chemistry in comets. These sulfur molecules are: the trimer (CH2S)3 and the tetramer (CH2S)4 of thioformaldehyde, pentathian S5CH2, hexathiepan S6CH2, thiirane C2H4S, trisulfane HSSSH, and thioacetone (CH3)2CS. Infrared spectra of these species are calculated using density functional theory methods. The majority of calculated bands belong to the mid-infrared, with some of them occurring in the near and far-infrared region. We suggest that some of unidentified spectral features measured by Infrared Space Observatory in several active galactic nuclei and starburst galaxies could be caused by 1,3,5-trithiane ((CH2S)3), 1,3,5,7-tetrathiocane ((CH2S)4), and thiirane (C2H4S). The objects whose unidentified infrared features we compare with calculated bands are: NGC 253, M82, NGC 1068, Circinus, Arp 220, 30 Doradus, Orion KL, and Sgr B2., accepted for publication in MNRAS

Six hundred thirty-two honey samples from Croatia were analyzed by reference methods (physicochemical and melissopalynological analyses), from which 506 were assigned to one of nine unifloral honey types (black locust, sweet chestnut, lime, sage, heath, mandarin, false indigo, immortelle and winter savory). Vibrational spectra of honey samples recorded using Fourier transform infrared (FTIR) spectroscopy and attenuated total reflection (ATR) technique were subjected to comprehensive chemometric assessment involving optimization of data preprocessing and multivariate statistical analyses, namely principal component analysis, partial least squares regression, partial least squares discriminant analysis and receiver operating characteristic (ROC) analysis. A specially designed hybrid multidimensional model (partial least squares-linear discriminnat analysis) was used to assess a relationship between honey IR spectra and relative frequencies of pollen grains (pollen spectrum) present in selected honey samples. The study demonstrated that a targeted spectral profiling, i.e., preprocessing of a fingerprint spectral region (1, 800–700 cm−1) by particular Savitzky–Golay filtering parameters and ROC modelling approach, enables accurate classification (100 % correct classification) of unifloral honeys by their botanical origin with low misclassification risk (MR = 0.099) and negligible small number of misclassified samples (1–2 per class—honey type). The results have also revealed good predictive strength of FTIR-ATR spectroscopy for melissopalynologycal data.

Although beeswax adulteration represents one of the main beeswax quality issues, there are still no internationally standardised analytical methods for routine quality control. The objective of this study was to establish an analytical procedure suitable for routine detection of beeswax adulteration using FTIR-ATR spectroscopy. For the purpose of this study, reference IR spectra of virgin beeswax, paraffin, and their mixtures containing different proportions of paraffin (5 - 95%), were obtained. Mixtures were used for the establishment of calibration curves. To determine the prediction strength of IR spectral data for the share of paraffin in mixtures, the Partial Least Squares Regression method was used. The same procedure was conducted on beeswax-beef tallow mixtures. The model was validated using comb foundation samples of an unknown chemical background which had been collected from the international market (n = 56). Selected physico-chemical parameters were determined for comparison purposes. Results revealed a strong predictive power (R2 = 0.999) of IR spectra for the paraffin and beef tallow share in beeswax. The results also revealed that the majority of the analysed samples (89%) were adulterated with paraffin; only 6 out of 56 (11%) samples were identified as virgin beeswax, 28% of the samples exhibited a higher level of paraffin adulteration (>46% of paraffin), while the majority of the analysed samples (50%) were found to be adulterated with 5 - 20% of paraffin. These results indicate an urgent need for routine beeswax authenticity control. In this study, we demonstrated that the analytical approach defining the standard curves for particular adulteration levels in beeswax, based on chemometric modelling of specific IR spectral region indicative for adulteration, enables reliable determination of the adulterant proportions in beeswax.

Infrared (IR) spectroscopy was used to quantify the ion mixture effect of seawater (SW), particularly the contribution of Mg(2+) and Ca(2+) as dominant divalent cations, on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-posphocholine (DMPC) bilayers. The changed character of the main transition at 24 °C from sharp to gradual in films and the 1 °C shift of the main transition temperature in dispersions reflect the interactions of lipid headgroups with the ions in SW. Force spectroscopy was used to quantify the nanomechanical hardness of a DMPC supported lipid bilayer (SLB). Considering the electrostatic and ion binding equilibrium contributions while systematically probing the SLB in various salt solutions, we showed that ionic strength had a decisive influence on its nanomechanics. The mechanical hardness of DMPC SLBs in the liquid crystalline phase linearly increases with the increasing fraction of all ion-bound lipids in a series of monovalent salt solutions. It also linearly increases in the gel phase but almost three times faster (the corresponding slopes are 4.9 nN/100 mM and 13.32 nN/100 mM, respectively). We also showed that in the presence of divalent ions (Ca(2+) and Mg(2+)) the bilayer mechanical hardness was unproportionally increased, and that was accompanied with the decrease of Na(+) ion and increase of Cl(-) ion bound lipids. The underlying process is a cooperative and competitive ion binding in both the gel and the liquid crystalline phase. Bilayer hardness thus turned out to be very sensitive to ionic strength as well as to ionic composition of the surrounding medium. In particular, the indicated correlation helped us to emphasize the colligative properties of SW as a naturally occurring complex ion mixture.

Diacetylenic dehydrobenzo[12]annulene and dehydrobenzo[18]annulene derivatives with electron-donor and -acceptor groups were synthesized (including push-pull Eglinton-Galbraith dimer derivative 1c) via an oxidative coupling reaction, and spectroscopically and structurally characterised. The solid-solid phase transition in 1b has been revealed at 45 °C by DSC measurements. Its room-temperature crystal structure has been solved by X-ray diffraction measurements. The 1H- and 13C-NMR chemical shifts, UV/Vis and infrared absorption spectra and Raman scattering spectra have been analyzed by using ground-state DFT calculations. The strongest absorptions in the UV/Vis spectra of 1 and 2 most probably are not due to the HOMO&reg ; ; ; ; ; ; LUMO excitations but due to the (HOMO-1) &reg ; ; ; ; ; ; LUMO and HOMO&reg ; ; ; ; ; ; (LUMO+1) excitations. The substitution effects on the electronic charge distribution of the all-carbon annulenic cores can be particularly well observed in the distribution of IR intensities in the region of acetylenic stretching vibrations. IR intensities are thus useful in studying the extent of resonance interactions also in acetylenic macrocycles.

Low-frequency Raman scattering was used to study amorphous solid films of adamantane, a globular non-polar hydrocarbon molecule. As evidenced by its spectral characteristics this type of disorder is different from the orientational disorder found in the room temperature plastic phase by the absence of the translational order as well. This gives rise to the boson peak related to acoustic phonons which gradually disappears upon heating with simultaneous emerging of the phonon line at 50 cm−1 which characterizes the low-temperature ordered phase of adamantane. Adamantane dynamics resembles that of C60 fullerene although not in the same temperature range. All this makes adamantane an attractive system that could serve as a practical reference in molecular simulation studies of the glassy phase of model fluids.

The geometries and vibrational frequencies of an iron(II) spin-crossover complex Fe(phen)2(NCS)2 in the low- and high-spin state have been calculated using DFT (BP86 functional with 6-31G* and LANL2DZ basis sets). A redundancy-free set of internal coordinates has been defined and used to obtain a valence force field. The use of the symmetry coordinates of a perfect octahedron as internal coordinates for the FeN6 framework of the complex has enabled the description of the stretching-bending couplings. A comparison of the force constants of free ligands with the corresponding constants of the two spin states has served as (provided / established) a basis for the discussion of the changes in electronic charge distribution in the complex. By use of the generalized harmonic mode scrambling it is shown that in the low-lying normal vibrations of the complex, the ligands participate as almost rigid units. Energies of tThese modes are in energy close to the oscillators describing the interaction of the complex with the surrounding molecules in the solid phase.

By means of Raman scattering experiment performed on single crystals of solid nitromethane in various polarization geometries at normal pressure and low temperatures, the Davydov splitting of the vibrational levels in the solid phase of hydrogenated CH3NO2 and perdeuterated CD3NO2 nitromethane is reported for the first time. A re-examination of the lattice vibrations in their various symmetry species is also given. These experimental data are discussed on the basis of calculations using harmonic models of stretching, bending, and torsional motions of an isolated molecule and using density functional theory and second-order Moller–Plesset perturbation theory. Then, following Sorescu et al. [J. Phys. Chem. B 104, 8406 (2000).], the intermolecular interactions (Buckingham 6-exp form plus charge–charge Coulombic interactions) were added to the intramolecular potential. The frequencies of the q≈0 phonons or vibrons of different symmetry species were calculated paying a special attention to the symmetric and an...

The low-wavenumber (10–200 cm−1) polarized Raman spectra of 4,4′-dibromobenzophenone single crystal at different temperatures (10–295 K) and far-infrared spectra (20–200 cm−1) of powdered samples at room temperature were recorded. The assignment of the lattice vibrations based on the lattice dynamics calculation at k = 0, which takes into account the seven lowest intramolecular modes, is presented. The unusual temperature behavior of some bands was explained by dephasing relaxation processes. Copyright © 2002 John Wiley & Sons, Ltd.

The UV/Vis titration measurements, vibrational and NMR spectroscopy of isomeric dehydrodibenzopyrido[15]annulenes (DBPA) 1 and 2 clearly show that under proper conditions these macrocycles can achieve fast, quantitative and unselective binding of metal ions. The macrocycle 1 is an example of a hindered amine 2,6-bis(R)pyridine and its isomer 2 of a non-hindered amine 3,5-bis(R)pyridine. The protonation stoichiometry for both 1 and 2 was assumed to be DBPA:H+ = 1:1 and the formation constants log K = 4.77 ± 0.02 for 1, and log K = 6.78 ± 0.08 for 2 were obtained that well agree with those obtained under similar conditions for a macrocycle containing bipyridine units. The protonation of 2 gave the estimated stoichiometry of 2:H+ = 1:1 while the stoichiometric protonation of macrocycle 1 could not be achieved and the lower stability of the ion pair containing 1H+ is most likely due to the inaccessibility of the nitrogen atom of 1 to the counterions and solvent molecules. The structures and electronic absorption spectra of 1 and 2, as well as the structures and spectra of 1H+ and 2H+, i.e. the species formed by protonation of the pyridine nitrogen, were calculated with the time-dependent DFT method with a B3LYP functional and a 6-31+G(d) basis set. The solvent effects were incorporated by means of the polarizable continuum model (PCM). The agreement of the calculated absorption data for the parent and protonated species with the observed spectra is rather satisfactory. Vibrational IR and Raman spectra of 1, 2, 1H+ and 2H+ in vacuo were calculated at the B3LYP/cc-pVTZ level of theory. Macrocycles 1 and 2, and their products protonated by trifluoromethanesulfonic acid (1HOTf and 2HOTf) were also characterized by temperature-dependent FTIR technique known as two dimensional IR correlation analysis. Quite large difference in degradation temperature between macrocycle 1 and 2 and their protonated complexes was measured, indicating that inclusion of proton leads to significant thermal stabilization of dehydroannulene ring.

Weak hydrogen bonds formed by 2- and 3-ethynylpyridine and ethynylbenzene with trimethylphosphate and phenol were characterized by IR spectroscopy and DFT calculations (B3LYP/6-311++G(d, p)). The structure and stability of ethynylpyridines and ethynylbenzene in the gas phase and in the complexes with trimethylphosphate and phenol are discussed in terms of geometry and electronic charge redistribution. Anharmonic effects are taken into account when calculating vibrational wavenumbers of these systems what lead to partial improvement of agreement with experiment. The changes in the electronic charge distribution are behind the frequency shifts of the CC stretching in opposite direction depending on the role the ethyne molecule has in a hydrogen bonded complex (Δν̃=+9 cm(-1) in trimethylphosphate complexes, Δν̃=-3 cm(-1) in phenol complexes). The association constants were determined by keeping the concentrations of proton donors approximately constant and low enough to avoid self-association and the proton acceptors were present in excess. The values obtained for the association constants and enthalpy changes in C2Cl4 (for trimethylphosphate complexes K≈0.5-1.0 mol(-1)dm(3) and -ΔrH≈6-8 kJ mol(-1), for phenol complexes K≈20-40 mol(-1) dm3-ΔrH≈17-22 kJ mol(-1)) are in good agreement with literature data.

The characterization of intramolecular H-bonds in terms of atomic charges and charge fluxes (at the B3LYP/cc-pVTZ level of theory) has been extended to the case of the so called resonance-assisted (RA) H-bonds. A quadratic correlation between the charge fluxes ϕH and the molecular IR absorption coefficients E that includes the entire family of the studied systems (31 of them) containing both intra- and intermolecular hydrogen bonds (O–H⋯O/N) confirmed the critical importance of the charge fluxes on the IR intensity enhancements. Since they reflect changing of the atomic charge distribution during the normal modes of vibrations, the dynamic nature of hydrogen bonding properties has been re-emphasized. The changes of the charge flux of the hydroxyl hydrogen in an RA intramolecular H-bond are between those for “free” OH bonds and the values calculated for intermolecular H-bonds. The transition “free” → intramolecular → intermolecular is gradual and therefore the hydrogen charge flux can be considered as practically sufficient to give quantitative measure to the intuitively obvious statement that “intramolecular H-bonding is somehow in between no H-bonding situation and intermolecular H-bonding” and thus provide a quantitative and yet simple parameterization of H-bond strength. In strictly planar molecules, the difference of the sums of charges of atoms participating in the 6-membered H-bond ring ΔΣ can serve as a measure of the charge delocalization after the H-bond is formed. The electronic charge is withdrawn from the group of six atoms when the H-bond is formed in nitrophenol (ΔΣ = −0.07), while the opposite is true (ΔΣ = +0.03) for 2-hydroxy benzylidene amine. The corresponding values of the geometrical resonance parameter Δ are 0.39 and 0.37, respectively, similar to those found for 2-hydroxy acetophenone and 2-hydroxy benzaldehyde. The extent of the π-electron delocalization as measured by the resonance parameter Δ does not follow the strength of H-bond as measured by the charge flux ϕH.

Infrared and Raman spectra of crystalline, melted and solvated ortho-terphenyl and its perdeuterated isotopomer, D_14-ortho-terphenyl, have been recorded. Optimized geometries and vibrational frequencies were calculated by the semiempirical RHF/AM1 method and by means of DFT method using B3LYP functional and 6-31G(d) basis set. In both cases the lowest energy conformation is of C_2 symmetry. With the scaled AM1 and B3LYP/6-31G(d) force fields the average error in reproducing the experimental molecular vibrational frequencies is 13 and 5 cm^-1, respectively. The AM1 potential energy surface for phenyl torsions was mapped on a 15 deg grid. The barrier to concerted internal rotation is estimated to lye between 3 and 6 kJmol^-1. The calculations of the lattice dynamics at k=0 in the low-temperature fully ordered crystal phase of parent and deuterated ortho-terphenyl were performed with inclusion of six low-lying intramolecular vibrations. The conformational change of the ortho-terphenyl molecule induced by crystal packing forces was taken into account by redefining the unperturbed molecular vibrational states. Although an accurate assignment of lattice vibrations was not possible, the calculated spectra give quite reasonable picture of the low-frequency dynamics in crystalline ortho-terphenyl. The relevance of the obtained results to the glass forming property of ortho-terphenyl is discussed.

Resonance Raman intensities of perdeuterated cis-stilbene were measured using excitation at 266 nm. For the six analysed bands at 1612, 1564, 1537, 1372, 1325 and 958 cm−1, no large changes in intensity distribution relative to the parent compound were found in accordance with the scrambling coefficients showing that the corresponding modes ν7, ν8, ν9, ν10, ν11 and ν15 of d12-cis-stilbene have all of the Raman activity. The S1 equilibrium geometry and vibrational force field for cis-stilbene were calculated at the CIS/6–31G(d) level and the vibrational assignment for the parent compound and some of its symmetrically substituted isotopomers is considered. The obtained excited-state geometry distortions are large, preventing the use of a simple displacement equation for relative Raman intensities. Therefore, in their determination the gradients of the S1 state, potential energy surfaces calculated at the ground-state geometry were also used. Even in its simplest form this approach reproduces the experiment fairly reasonably. Copyright © 2001 John Wiley & Sons, Ltd.

Raman (3100–10 cm −1 ) and IR (3100–200 cm −1 ) spectra of solid and dissolved 1,1′-biadamantane were recorded. The molecular structure and vibrational normal modes were calculated using the semi-empirical AM1 Hamiltonian. The distortions from the tetrahedral geometry induced by linking two adamantane units are discussed. The potential barrier of 19.3 kJ mol −1 for internal rotation of two adamantyl cages around the central bond was determined by calculations of heat of formation for fully relaxed structures at different dihedral angles. The final scaled vibrational force field was obtained by transferring the scale factors from parent adamantane. The normal mode displacements are described in terms of adamantane normal mode displacements using the generalised harmonic mode scrambling approach. The central bond stretching, torsion around the central bond and CCC deformations involving the central bond are genuine 1,1′-biadamantane vibrations. The semi-rigid molecular model is qualitatively applied on lattice dynamics of 1,1′-biadamantane in order to assign two Raman bands observed below 100 cm −1 .

A cage-like polar molecules of 2-adamantanone (C10H14O) at room temperature form plastic crystal phase. We present the experimental results that show the existence of different low-temperature structures of 2-adamantanone: glassy crystal state, ordered crystal state and amorphous state in the form of molecular films. The glassy crystal state is obtained by rapid undercooling of a plastic phase. The freezing primary involves the rotational degrees of freedom of molecules but the translational order of the plastic phase is preserved. The phase transition to the ordered crystal state is observed after a very slow annealing process between the room temperature and 10K. Amorphous 2-adamantanone films were prepared by vacuum evaporation and deposition onto cold metal substrate at temperature 10K. The different low-temperature structures of 2-adamantanone have been studied by Raman spectroscopy. The low-frequency Raman spectra are analysed by means of reduced Raman intensity . The reduced intensity of light scattering in disordered materials is given by: where is Bose factor, describes the coupling between light and vibration modes, is the density of states. The analysis of reduced Raman intensity shows that the structures of different low-temperature 2-adamantanone states are reflected in the characteristic low-frequency spectra.

The vibrational analysis of 2-adamantanone and the group of all possible mono- and two gem-dideuterated 2-adamantanone isotopomers (2-adamantanone-3-d1, 2-adamantanone-endo-4-d1, 2-adamantanone-exo-4-d1, 2-adamantanone-5-d1, 2-adamantanone-6-d1, 2-adamantanone-4,4-d2 and 2-adamantanone-6,6-d2) is presented. The assignments for fundamentals are based on the characteristic group frequencies, i.e. comparison with adamantane, Raman depolarization ratios, isotopic frequency shifts and are supported by the normal coordinate calculations. The force field was obtained from the semiempirical AM1 calculations and the assumed transferability of the scaling factors for adamantane. The average error between the observed and calculated frequencies is 11 cm−1. The effects of the carbonyl group and deuterium substitutions on the adamantane-like normal modes were investigated in terms of the harmonic mode scrambling analysis.

A scheme is proposed for decomposing a normal mode of a derivative molecule in terms of the normal modes of parent molecules. In the case of light and heavy isotopically labelled molecules it reduces to the harmonic mode scrambling in the usual sense. The scheme is quite general and provides a quantitative description of the normal mode displacements of one group of atoms in terms of those of another group. It is suitable for the normal mode analysis of a molecule calculated by semi-empirical or ab initio programs which perform vibrational analysis in Cartesian coordinates only.

The properties of the propellane bond in 2, 4- methano-2, 4-didehydroadamantane (1) and 2, 4- (dimethylmethano)-2, 4-didehydroadamantane (2) have been determined on the basis of the spectroscopic and chemical evidence. A monitoring of reaction of propellane 2 with dimethyl disulfide by Raman spectroscopy has indicated the cleavage of the central bond between inverted carbon atoms. Raman and infrared spectra of 1 and 2 as well as bf their dihydro congeners 2, 4-methanoadamantane (3) and 2, 4-(dimethylmethano)adamantane (4) have been recorded. To describe the vibrational and molecular orbital properties of these compounds (harmonic frequencies, heats of formations, bond orders, and charge distributions), AM1 semiempirical calculations were performed. The calculated properties are found to be in fair agreement with the observed ones. By combining the results of spectroscopic investigations and molecular orbital calculations, the central bond between inverted carbon atoms is associated with the highest occupied molecular orbitals in propellanes 1 and 2. Assuming the transferability of the adamantane scaling factors for force constants within the studied group of molecules, an ""a priori"" assignment of the observed bands has been obtained.

Raman and infrared spectra of adamantane-d0 and several of its isotopomers (adamantane-1-d1, adamantane-2-d1, and adamantane-2,2-d2) have been recorded and assigned using the valence empirical force field and isotopic frequency shifts. Few inactive fundamentals of adamantane-d0 were located by means of their activity in either the low-symmetry isotopomers or the low-temperature phase. The vibrational spectrum of adamantane-d16 had to be reinterpreted. The force field obtained from the semiempirical AM1 parametrization was scaled using the vibrational assignments for adamantane-d0, -d16 and -1-d1. The two force fields were compared. Both reproduced the observed frequencies with practically the same average error of 16 cm−1. However, the number of parameters in the scaled semiempirical force field is only nine compared with 27 of the empirical force field.

The vibrational analysis of cis -stilbene in the ground electronic state based on the infrared and Raman spectra of a series of its isotopomers and scaled semiempirical AM1 calculations is reported. The C α C α stretching, all the four C α H deformations and the C α C α torsion are described. A comparison with trans -stilbene shows a much lesser degree of couplings between olefinic and phenyl vibrations in cis -stilbene.

The synthesis, separation, and characterization of mixed-ligand iron(II) complexes containing 1, 10- phenanthroline (phen), 1, 10-phenanthroline-5, 6- dione (pdon), and NCS− are reported. The mixed- ligand complexes [Fe(phen)(pdon)2]2+ and [Fe(phen)2(pdon)]2+ were prepared from iron(II) sulfate hepta hydrate and both ligands. The mixture of both complexes formed regardless the ratio of the ligands or the reaction time ; therefore, the complexes were separated successfully on the reversed phase (RP) Develosil RP-Aqueous [C30] 5 µm, 150 × 4.6 mm column by two different methods. The first method was the ion paired RP chromatography performed under gradient elution with acetonitrile–water containing 0.001 mol L−1 KPF6 aqueous as mobile phases. The second method was the RP chromatography performed under gradient elution with methanol and water as mobile phases. The gradient elution with water–methanol as eluents was preferred for the semi preparative separations allowing one to use the complexes without further purification upon separation, different than the first method and its variations so far. Three complexes (5, 6, and 7) were characterized by electrospray ionization mass spectrometry, NMR, UV-Vis, and IR.

The vibrational spectrum of the ground-state acenaphthylene molecule is interpreted by using infrared linear dichroism spectroscopy to determine polarization of the vibrational transitions, NIR-FT-Raman spectroscopy to record the Raman spectrum at liquid-air temperature and a scaled semiempirical AM1 force field to calculate the vibrational frequencies.

The performances of three semiempirical parameterization sets (MNDO, AM1 and PM3) in describing the vibrational properties (harmonic frequencies, isotopic frequency shifts and Coriolis constants) of benzene were tested. A set of the best (in the least-squares sense) scaling factors for the force constants, which improves agreement to within 20 cm −1 , was designed with the idea of it being used for the more complex cases of mono-substituted benzenes and polycyclic aromatic hydrocarbons.

The vibrational spectra of the protonated Schiff base of n-butylretinal (nSBR+) in dichloromethane are studied. The trifluoroacetic acid (TFA) is used for the protonation of the Schiff base of nbutylretinal (nSBR). Combining the two-dimensional correlation analysis of the experimental infrared spectra with anharmonic frequency calculations it is shown that two types of ionic aggregates between nSBR+ and the TFA counterion are formed. The study suggests that the interaction between nSBR+ and the TFA counterion may be responsible for the observed lost of photoselectivity in the trans-cis isomerization of the nSBR+ in solution. (doi: 10.5562/cca1826)

Thin films of polyester-based polyurethane-silica nanocomposites with 34% hard segments and different concentrations of nano SiO2 filler (0, 0.5, 1.0 and 3 vol.%) have been prepared. The hydrogen bonding and orientational behaviour of hard and soft segments were analysed using infrared linear dichroic measurements. The number of hydrogen bonded NH and C=O groups and orientation function were calculated from polarized FTIR spectra. The presence of nanosilica slightly increased the number of hydrogen bonded carbonyls. The soft segments in nanocomposite films display increased orientation in comparison to the neat polymer film. The addition of 3% nanosilica significantly reduced elongation at break. The results were compared with hydrogen bonding and orientational behaviour of thin film of polyether-based silica nanocomposites.