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In this work a study is reported on the Raman and UV–vis absorption spectra of recently synthesized poly (3-hexylthiophene-2,5-diyl) (P3HT) samples whose degree of head-to-tail (H-T) regioregularity has been, on purpose, modified in the range 98%-64% by a controlled insertion of head-to-head (H-H) coupled bithiophene monomers. The materials under study show the strongest Raman scattering line near 1450 cm−1, when recorded in off-resonance conditions. Based on the Effective Conjugation Coordinate theory we learn that this scattering originates from the collective CC stretching mode along the polymer backbone (Я mode). A curve fitting analysis reveals that this line is the result of the convolution of three strong components at 1445 cm−1, 1450 cm−1 and near 1480 cm−1 with different relative intensities as function of the sample regioregularity. These lines are assigned to polymer chains which take up different conformations namely: i) co-planar sequences of thiophene units, labelled as hairy-A, which originate the crystalline domains of form-1, ii) conformationally slightly distorted sequences of thiophene units, labelled as hairy-B, and iii) highly distorted/disordered sequences of thiophene units which originate the amorphous phase. Also the UV–vis absorption spectra recorded on thin films of the same materials can be interpreted as the convolution of the absorptions originated from the polymers chains in the three different conformations as in i), ii), and iii). With multi-wavelength resonance Raman spectroscopy is thus possible to enhance selectively the scattering of each type of chain. From the Raman data recorded in off-resonance a straightforward method to obtain the relative amount of the above structures is proposed, showing that solid rr-P3HT at room temperature is composed approximately by 50% of hairy-A chains and 50% of hairy-B chains with a negligible contribution by the amorphous phase. The information derived from this study are of great help for the understanding of the conformational structure in the solid state of the technologically relevant parent molecule rr-3PHT.

Air pollution mostly originating from car exhaust and industrial emissions is seriously endangering human health. The study of toxic effects of particulate matter (PM) is a subject of very active research that covers a broad field from biology to chemistry and technology. The main issue of these works is the understanding of the oxidative properties of PM. In this paper, we present a quantitative analytical method based on the resonance Raman spectroscopy of cytocrome c that can be used to monitor the oxidative reactions that may take place between biological samples and PM. Copyright © 2016 John Wiley & Sons, Ltd.

Carbonaceous particles of environmental origin are practically insoluble, which constitutes an obstacle to many chemical physical characterization techniques. Micro-Raman spectroscopy overcomes the sample preparation step and can be applied on the as-received sample and even in situ, with nowadays commercially available portable Raman equipment. Multivariate statistical analysis of Raman data recorded on a variety of carbonaceous particles of different origin, through a molecular interpretation of the signal, shows that the use of Raman spectroscopy with several excitation sources can provide a useful tool for assisting the characterization of various forms of environmental carbon matter. Copyright © 2015 John Wiley & Sons, Ltd.

It is commonly accepted that the toxicity of carbonaceous particulate matter (PM) is due to the production of reactive oxygen species (ROS) which induce biological damage in the exposed cells. It is also known that PM produced during the combustion processes consists of a carbonaceous core "dressed" with other organic and/or inorganic materials. In spite of this knowledge, the role of these materials in the production of ROS has not yet been clear. This work aims at understanding whether "naked" carbonaceous particles are capable of forming ROS either in cell-free or in-cell systems. The problem has been treated based on the data collected from pure graphite samples of different sizes obtained by ball-milling pure graphite for various lengths of time. The experimental approach considered Raman, ESR (spin trapping), cell viability and fluorescence spectroscopy measurements. These techniques allowed us to carry out measurements both in cell and cell-free systems and the results consistently indicate that also pure naked carbonaceous particles can catalyze the electron transfer that produces superoxide ions. The process depends on the particle size and enlightens the role of the edges of the graphitic platelets. Evidence has been collected that even "naked" graphitic nanoparticles are capable of producing ROS and decreasing the cell viability thus representing a potential danger to human health. © 2017 The Royal Society of Chemistry.

New data on vibrational properties of calcium oxalates and their controversial transformation mechanism are presented. We have focused on whewellite (CaC2O4·H2O) and weddellite [CaC2O4·(2 + x) H2O], the most common phases of calcium oxalate; these compounds occur in many organisms, in kidney stones and in particular kinds of films found on the surface of many works of art. Low temperature experiments carried out by Fourier transform infrared spectroscopy have highlighted both the high structural order in the crystalline state of whewellite and the disordered distribution of the zeolitic water molecules in weddellite. The synthesised nanocrystals of weddellite have been kept under different hygrometric conditions in order to study, by X-ray powder diffraction, the role of "external" water molecules on their stability. Moreover, in order to identify the different kinds of water molecules, a re-investigation, supported by quantum chemical calculations, of the observed vibrational spectra (IR and Raman) of whewellite has been conducted. © 2014 Published by Elsevier B.V.

Defect-free and highly homogeneous polyaniline (PANI)-Nylon 6 electrospun nanofibers are obtained through a solvent-induced segregation of N-phenyl-1,4-phenylenediamine (ADPA) on a fiber surface followed by an oxidative surface polymerization onto a wire-shaped template. Different oxidation salts are tested both as additives of the spinning solutions and in a polymerization bath. Comparison between mats obtained with a solvent induced segregation process and classical feed solution electrospinning is highlighted. As a result, self-standing emeraldine base PANI (EB) membranes are produced both in this pristine state and in a doped emeraldine salt state (ES). The doping process is carried out in different acid baths, namely hydrochloric acid, sulfuric acid and p-toluene sulphonic acid, the last being the most effective. Wire-shaped PANI membranes are characterized by scanning electron microscopy (SEM) and the polymerization/doping states of PANI are monitored step by step by UV-vis reflectance spectroscopy, infrared spectroscopy (FTIR) and contact angle measurements (CA).

We review the theory for overtones and combinations in resonant Raman spectroscopy introduced by Nafie, Stein and Peticolas in 1971 on the basis of time-ordered diagrams, and we apply it to β-carotene with the support of density functional theory calculations. Comparison with experimental results obtained by Tasumi's group in 1994 is provided. The theory here presented allows a prompt evaluation of resonant Raman intensities with presently available quantum chemistry tools. Copyright © 2014 John Wiley & Sons, Ltd.

This study aims to evaluate the relevance of portable Raman and portable mid-Fourier transform infrared (FTIR) reflectance instruments in monitoring the synthetic treatments applied on plaster substrates, a crucial issue in a conservation work. Some polymeric consolidants and protectives have a relatively short life owing to their degradation, and after some years the surface should be retreated. It follows that any information about the presence and composition of the products applied, their chemical transformations and their distribution on the surfaces is essential. For these purposes, conservation scientists should seek and test new in situ methods, and this is of utmost importance especially in the case of buildings, considering their large dimensions and consequent extensive mapping. The effectiveness of portable Raman and portable mid-FTIR reflectance instruments has been compared by analysing a set of laboratory specimens prepared and treated with variable amounts of products belonging to three classes of polymers; the spectroscopic investigation highlighted, for the first time, the limits and the advantages of portable Raman and portable mid-FTIR reflectance instruments in the detection of small amounts of products commonly employed for the conservation of plasters.

The chemical nature of the red pigment of Corallium rubrum (CR) has not yet been clearly identified. We have recorded the Raman spectra of CR, canthaxantin, and parrot feather, and we propose an interpretation with the help of quantum chemistry and of the effective conjugation coordinate theory, which accounts for the main Raman lines (ν1, ν2, ν3) as originating from the polyene backbone. In this study, two additional lines in the 1000 cm−1 range (ν4 and ν5) are considered as well as a series of overtones and combinations in the second order Raman spectrum (2000–3000 cm−1). Density Functional Theory calculations predict that, moving with successive methylation from a simple unsubstituted polyene chain with 9 C═C bonds (as psyttacofulvins) to a 9, 9′, 13, 13′ tetramethylated chain (as carotenoids), the geometric structures of the molecules and their Raman spectra show changes that can be rationalized if the effective conjugation coordinate theory is extended to account for mechanical confinement. This turns out to be a new concept that helps the interpretation of the Raman spectra of partially methylated conjugated oligoenes. Evidence is found that the main component of the pigment of CR does not posess a fully demethylated polyene chain (psyttacofulfine) nor a tetramethylated chain (carotenoid), thus indicating that the polyene chain is partially methylated. Because we consider resonance Raman spectra, the target of this study is the structure of the polyene backbone; no direct spectroscopic information can be obtained in this way on the chemical nature of the groups attached to both chain ends. Copyright © 2012 John Wiley & Sons, Ltd.

Linear sp-carbon polyynes are ideal molecules for the direct investigation of the physical properties of one-dimensional conjugated systems. Traditionally, the main obstacle to the study of these systems has been their instability under normal laboratory conditions. Thanks to improved chemical syntheses, a broadened range of polyynes is now available for study, including the hydrocarbon series endcapped with adamantyl groups, Ad[n]. In this work, the quantitative Raman spectroscopic analysis is reported for each member of this homologous series. The Raman scattering intensities corresponding to the major features of the polyyne segment (i.e., the effective conjugation coordinate or Я lines) are then used to evaluate the nonlinear optical (NLO) behavior via determination of the vibrational contribution to the second hyperpolarizability (γvib). This study shows that γvib values as a function of length are of the same order of magnitude as those arising from the electronic contribution to the molecular second hyperpolarizability, γele, as reported for triisopropylsilyl polyynes, TIPS[n], using the differential optical Kerr effect technique. The nonlinear response for Ad[n] polyynes, supported by the analogous response for TIPS[n] polyynes, confirms that linear sp-carbon molecules have large second hyperpolarizabilities that show a power-law increase in γ-values versus length that is larger than other known π-conjugated systems, such as polyenes. Furthermore, the NLO response of polyynes versus length approaches the theoretical limit described by Kuzyk more closely than other conjugated organic oligomers. Copyright © 2012 John Wiley & Sons, Ltd.

This study is focused on the evaluation by μRaman mapping of the penetration depth achieved by ammonium oxalate treatment in different plaster specimens, a hot issue in the conservation field. The role of the carbonatic aggregate particles and the influence of the different variables of the treatment on the penetration depth and on the distribution of the newly-formed phase (whewellite) have been ascertained. Based on the results of μRaman mapping, analyses with Field Emission Scanning Electron Microscopy have been carried out in order to observe the whewellite crystals and the carbonatic aggregate particles involved in the reaction with ammonium oxalate.

Infrared (IR) and Raman spectroscopy have been used to examine the vibrational characteristics of a series of three macrocyclic tetraynes in comparison with an acyclic analog. By changing the length of the alkyl tether of the macrocycles, varying degrees of bending of the tetrayne moiety can be achieved, and the joint use of IR and Raman spectroscopies provides an avenue to probe the impact of bending on the sp-chain. The spectroscopic data show a general trend toward decreasing activation of Raman bands in the IR spectra, and vice versa, as bending of the polyyne chain is decreased. Density functional theory calculations provide a detailed rationalization of the experimental observations. Copyright © 2011 John Wiley & Sons, Ltd.

The potential of non-invasive in situ analytical techniques such as portable Raman, portable X-ray fluorescence, portable optical microscope and fibre optics reflectance spectroscopy has been shown studying painted layers of Renaissance terracotta polychrome sculptures belonging to the statuary of Santo Sepolcro Church in Milan. The results obtained allowed pointing out the contribution of these techniques to the compositional diagnostic, providing complete information, in some cases, better than micro-destructive techniques, on the kind of pigments used on the external painted layers. Moreover, a comparison with the results obtained before the last conservation work (2009) with micro-destructive techniques allowed ascertaining the removal of the external painted layers during the conservation operations.

A first-principles assisted study of the Raman spectrum associated with the photoactive chromophore in bacteriorhodopsin (bR) allowed the elucidation of the effective coupling existing between the π electrons of the retinylidene chromophore and the local environment of the Schiff base. The role of the counter-ion on the electronic and vibrational structure of the chromophore is investigated by means of density functional theory (DFT) calculations. Several molecular models of the retinylidene chromophore interacting with different counter-ions facing the Schiff base have been considered. The counter-ion induces a strong modulation of the position of both the UV–vis absorption maximum and the strong Raman active collective CC stretching mode, related to the effective conjugation coordinate (ECC). Experimental Raman and UV–vis absorption data are interpreted in the light of these theoretical findings. The data collected in this paper provide an interesting accumulation of points along the optical gap versus ECC wavenumber relationship. Copyright © 2011 John Wiley & Sons, Ltd.

An analytical model based on the Equilibrium Charges and Charge Fluxes (ECCF) theory is presented for the determination of the molecular charge distribution and its mobility on the basis of the Atomic Polar Tensors obtained by first-principles calculations. The case of OH bonds in molecules containing the >C OH and COOH functional groups are analyzed in details and explicit equations are reported for the straightforward calculation of equilibrium atomic charges and charge fluxes. The values obtained describe correctly the intramolecular properties and show a good transferability among similar molecules. The model can be applied not only to the interpretation of the peculiar chemical/physical properties of functional groups in their specific intramolecular environment, but it can be also used as a theoretical method to investigate the effect of the molecular charge distribution and its mobility on IR absorption intensities, i.e. the correlation between ECCF and experimentally measurable quantities.

Infrared vibrational spectroscopy has been used to reveal the conformations of the Ziegler−Natta catalysts internal electron donor 9,9-bis(methoxymethyl)-fluorene and its selectively deuterated derivative (9,9-bis(1,1-dideutero-methoxymethyl)-fluorene), in the solid state, complexed with TiCl4 and MgCl2 and in the catalyst precursor. The experimental spectra have been interpreted by means of spectroscopic correlations and theoretical results from quantum chemical calculations on selected molecular models. From experimental and theoretical data two chelating geometries of the donors with both oxygen directly interacting with Ti or Mg atoms turn out to be favorable. They can be identified by the four dihedral angles along the CH3−(O−CH2−R−CH2−O)−CH3 residue that take on conformations of approximately trans (T), gauche+ (G), or gauche− (G′), namely, TGGT and TGG′T. We propose the TGGT conformations for the crystal phase of the donor, the TGG′T when it is complexed with TiCl4, and both TGGT and TGG′T when com...

Molecules composed of sp-hybridized carbon chains (polyynes) are the simplest of the known conjugated organic oligomers. In comparison to their counterparts such as polyacetylene and polydiacetylene, however, the formation of polyynes has traditionally posed a difficult synthetic challenge. In particular, there is no reliable method to form end-capped polyethynylene, and monodisperse polyynes have therefore been assembled. As a result, structure–property relationships for shorter polyynes have been relatively well established in recent years, while extension of these trends toward longer polyynes has remained a difficult task. Using the Fritsch–Buttenberg–Wiechell (FBW) rearrangement, the formation of diynes through decaynes has become possible and has provided a unique chance to explore the physical characteristics of conjugated polyyne chains. This paper highlights recent advances in the synthesis of extended polyynes, as well as interesting aspects of their NMR, Raman, and UV/vis spectroscopic analyses. These synthetic achievements offer the opportunity to predict some of the properties of the carbon allotrope carbyne. In particular, a set of X-ray crystallographic analyses of t-Bu end-capped polyynes (tBu[n]) shows a definitive experimental trend in reduced bond-length alternation (BLA).

A theoretical model based on Huckel theory is presented and applied to the infinite linear carbon chain. The effect of Peierls distortion, π-electron confinement and electron–phonon coupling are interpreted on the basis of measurable parameters such as bond length alternation, electronic gap and Raman wavenumbers. A diagram is presented where the correlation among these quantities is shown on the basis of the model adopted. The effect of π-electron confinement on experimental data can be directly evaluated, and insights on the physical properties of these materials can be derived. Copyright © 2009 John Wiley & Sons, Ltd.

Apomorphine (aporphine-10,11-diol, CA Registry Number 58004) is a non-narcotic derivative of morphine discovered in 1869 by Mattheisen1 and it is a well-known potent short-acting dopamine agonist at D1 and D2 dopamine receptors, typically used in the treatment of patients with advanced Parkinson's disease (PD). To identify the unknown vibrational spectrum of this compound, apomorphine bare salt and its commercial drug formulation (Apofin) were examined by means of Raman spectroscopy. In the Raman spectrum of apomorphine (both bare salt and commercial drug), two strong characteristic signals were found, which were assigned with the help of first-principles calculations: the band at 1589 cm−1 (assigned to the stretching mode of the B aromatic ring coupled with CH in-plane bending) and the band at 1302 cm−1 (assigned to O-H in-plane bending and CH2 twisting and wagging vibrations). Copyright © 2009 John Wiley & Sons, Ltd.

A solid-state memory based on a hindered phenol substituted bithiophene is reported, showing conductance switching behaviour between three discrete states among which it is possible to cycle repeatedly on the basis of three characteristic threshold voltages. The experimental measurements show that the addressing of the three states is independent of the programming time, that the retention time for each state is longer than 15 h and that the devices endure current–voltage cycles well in excess of 50. Considerations based on density functional theory calculations are made to provide hints on the mechanism behind this memory effect.

Parenterally administered cladribine (2-chloro-2'-deoxyadenosine) has demonstrated promising efficacy and safety in clinical trials in patients with multiple sclerosis (MS). An oral formulation of this small molecule would be an attractive option for patients. Here, we describe the chemical characterisation of the inclusion complex between cladribine and the drug carrier molecule 2-hydroxypropyl-beta-cyclodextrin (2-HP-beta-CD). Several techniques were used to analyse the complex both in solution and in the solid state. These analyses provided evidence that the inclusion complex cannot be simply reduced to the sum of the two species, as it shows behaviour different from that of the physical mixture of the two components. Furthermore, solution nuclear magnetic resonance spectroscopy demonstrated the existence of an inclusion complex between cladribine and 2-HP-beta-CD. Importantly, analysis of a tablet formulation demonstrated that the chemical characteristics of the inclusion complex are not affected by the manufacturing process, and that the complex is stable during storage. This tablet formulation is currently under investigation for the treatment of patients with MS.

A series of phenyl end-capped oligothiophenes has been synthesized and a study of the absorption and emission properties has been carried out; the photoluminescence quantum yield has been measured both in solution and in solid state. The characterization, supported by DFT calculations, highlights a strong relationship between the optical features and the differences in the chemical structure. The results show that some molecules are of interest in the field of organic light emitting diodes (OLEDs).

The modeling of the vibrational structure of materials is of great help for the use of vibrational spectroscopy for structural characterization. This is especially true in presence of conjugated π electrons where the delocalized nature of π orbitals produces long-range interactions responsible for a marked dependence of the vibrational states on the confinement. This effect is due to the finite size of the molecules as well as to chemical and/or structural defects or to the presence of nanocrystals. To model the vibrational states we adopt a semiempirical model developed in the framework of a tight binding theory for π electrons (Huckel theory). This treatment has been already successfully applied in the past to the study of the vibrational dynamics of polyynes, graphene and carbon nanotubes and it is here extended to the case of sp linear carbon chains (polyynes). It is shown that the effect of the confinement on the vibrational features is influenced by the presence of a Kohn anomaly in the limit of a cumulenic structure. This behaviour is shared by all conjugated carbon materials irrespective of the hybridization of C atoms (sp 2 or sp).

Functionalized perfluoropolyethers are investigated by infrared spectroscopy with the aim to give a quantitative estimate of the carboxylic acid groups species; since hydrogen bonded moieties have been observed, also the relative distribution of the associated species has been determined. The study is based both on measured and on theoretically predicted infrared intensities, as obtained by density functional theory (DFT) calculations on model systems.

Amorphous fluorinated optical polymers, characterized by high transparency in the visible and near infrared spectra, high glass transition temperature and very good resistance to chemical environment, have been developed by co-polymerisation of tetrafluoroethylene (TFE) and 2,2,4-trifluoro-5-trifluoromethoxy-1,3-dioxole (TTD). In this work we study at molecular level the effect of the introduction of the bulky TTD unit in a perfluoroalkyl chain. In particular the effect on the molecular structure and chain flexibility is investigated and spectroscopic markers correlated to chemical and structural defects are identified. The study includes a thorough experimental spectroscopic analysis (infrared and Raman spectra) of several different copolymer samples and a modelling based on Density Functional Theory calculations and semiempirical calculations on suitable model molecules.

The modulation of the longitudinal optical (LO) phonon branch of a linear, infinite carbon chain (carbyne) by the degree of bond length alternation (BLA) is discussed in relation to the wavenumber dispersion of the strongest Raman line of oligoynes. Furthermore, the potential energy surface describing the Peierls distortion of the infinite 1D crystal has been determined theoretically through DFT calculations with periodic boundary conditions. A two-minima potential surface has been obtained as a function of BLA parameter, under the constraint that the diatomic unit cell keeps its translational period fixed to the optimized value. In this way, it has been possible to obtain the generalized harmonic force constant associated with the LO phonon at the Γ point. The results obtained can be related to the observed behavior of the LO Raman line upon the temperature-driven phase transition towards a cumulenic structure. Copyright © 2007 John Wiley & Sons, Ltd.

In this work, the vibrational force fields of hydrogen-capped oligoynes of increasing chain lengths are investigated by means of density functional theory calculations. It is shown that the interaction force constants between CC stretching coordinates decrease slowly with the distance between the two bonds considered. The consequence for the frequency dispersion of longitudinal optical (LO) phonons of an infinite polyyne chain is discussed and related to the observed behavior of the spectra of finite-size molecules. Effects of the exchange-correlation functional and of the basis set on the vibrational force constants are also investigated and the need for a scaling procedure is pointed out. Accordingly, new force fields which allow predictions in very good quantitative agreement with the available experimental data for oligoynes have been obtained, providing a sound assignment of alpha and beta lines.

Polyamide 6 (PA6) nanotibers were prepared from formic acid solutions by using electrospinning technique. The fibers were smooth, defects free and with diameters smaller than 200 nm. Small amounts of a perfluorinated acridine were added as dopant to the feed solution to modify the wettability of the fibers. The effect of doping on the contact angle values is well apparent. The contact angle values go from 50 degrees of pure PA6 to 120 degrees when 6% of acridine is added. A comparison between fibers and films of pure and doped polyamide 6 was carried out in order to determine the effect of morphology on wettability. Thermal annealing near the T, of the polymer promoted the segregation of the molecules to the surface, reaching contact angles of 131 degrees with smaller amounts (4%) of acridine. The surface segregation was also promoted by time aging. (c) 2007 Elsevier B.V. All rights reserved.

The electrospinning technique is used to obtain functionalized polymeric fibers. Blends of polyethyleneoxide (PEO) and poly-3-dodecylthiophene (P3DDT) have been spun from chloroform solution. The fibers diameter is approximately 1 μm and both polymer components occur in the fibers as separated phases. By washing the fibers with acetonitrile the PEO matrix is completely removed. This process is fast and it leaves long and homogeneous fibers of P3DDT. The morphology and structure of the fibers have been studied with microscopy (SEM and fluorescence confocal microscopy), whereas infrared spectroscopy has been used to check the removal of PEO matrix, to understand the conformation of the polythiophene chains and their orientation in the fibers. Measurements with confocal and SEM microscopes show the homogeneity of the washed fibers; from polarized infrared spectroscopy, the polythiophene chains are mostly aligned along the fiber axis. The electrospinning process followed by a suitable washing step makes possible to orient fibers with a high molecular order.

A novel SERS (surface-enhanced Raman scattering) sensor has been recently developed; its peculiar geometry is able to increase considerably both the SERS active surface and the number of internal reflections at the interface between silica and silver, thus allowing an increase of the signal intensity. The aim of this work is to demonstrate that this sensor could be efficiently used to detect some molecules such as illegally used veterinary medicine (crystal violet and malachite green) below the ppb detection limit. The advantages of this sensor with respect to other detection techniques are not only the higher sensitivity, but also the fast response and the possibility of coupling with a portable Raman spectrometer for “on-field” measurements. The ability of the sensor to work under real environmental conditions in the presence of many cationic and anionic species has been tested both in solutions containing sodium and chlorine ions and in water coming from the aqueduct of Milan and from the (normally polluted) river Serio.

The FT-Raman spectra of a series of mechanically prepared MgCl 2 –TiCl 4 samples with increasing content of TiCl 4 have been recorded. Raman scattering lines in the range 600–100 cm −1 reveal the formation of TiCl 4 molecules complexed on the lateral cuts of activated MgCl 2 crystals. This pattern of lines suggests that atleast three types of complexes are formed during the grinding process and their relative concentration depend on the starting concentration of TiCl 4 . Two types of these complexes have been shown to be unstable and easily removed when the samples are washed with n -hexane. In the former two cases TiCl 4 molecules are seemingly physisorbed and/or weakly complexed on MgCl 2 . The remaining complex is stable and it is found in every sample also after washing. This stable complex shows Raman lines which can be interpreted as originated from the complexed TiCl 4 molecules with the Ti atoms in an octahedral coordination. On the other hands also monomeric TiCl 4 species complexed along the (1 1 0) lateral cut or dimeric TiCl 4 species complexed along the (1 0 0) lateral cuts of the MgCl 2 crystal can take up a geometry with the Ti in an octahedral coordination. Both these structures have been considered in this work. Calculated Raman spectra, molecular energy considerations and Raman lines intensity ratios strongly support the fact that the stable complexes are the monomeric TiCl 4 species complexed along the (1 1 0) MgCl 2 lateral cuts. A spectroscopic quantitative determination of the complexed TiCl 4 for this class of material is proposed.

Photochromic diarylethene molecules are characterized by electronic properties significantly different in the two isomers. In this work, we are particularly concerned with the vibrational contribution to second order hyperpolarizabilities. We show that a systematic increase of the non-linear optical properties is observed every time the closure reaction is induced by a suitable irradiation. The large change of molecular non-linear optical coefficients can be exploited e.g., for the realization of an optical switch. Moreover, we show that also the intrinsic response of the “closed” (i.e., more conjugated) form is, in some case, quite large. The structural reasons of this phenomenon are discussed.

We have analyzed a set of 51 PAHs whose structures have been hypothesized from mass spectrometry data collected on samples extracted from carbon particles of combustion origin. We have obtained relationships between infrared absorption signals in the fingerprint region (mid-IR) and the chemical structures of PAHs, thus proving the potential of IR spectroscopy for the characterization of the molecular structure of aromatic combustion products. The results obtained here for the spectroscopic characterization of PAHs can be also of interest in Materials Science and Astrophysics.

FT-Raman spectra ( λ exc =1064 nm) of two crystalline forms (I and II) of Nolomirole are presented and discussed. Spectral markers characteristic and selective for the two polymorphs are identified. The analysis of Raman spectra obtained from samples made as mechanical mixtures of the two pure polymorphs suggests criteria for developing a spectroscopic method for the determination of the two phases in Nolomirole samples of unknown polymorph composition. On this basis a revision of some published results and conclusions concerning phase transformations occurring in thermally and/or mechanically treated Nolomirole powders is proposed.

Calcium oxalate is found in nature in three different crystalline states determined by the number of H2O in the unit formula (whewellite CaC2O4·H2O, COM; weddellite CaC2O4·(2 + x)H2O, COD and caoxite CaC2O4·3H2O, COT). The properties of these materials are relevant in the field of biomedicine, cultural heritage and mineralogy. In two previous papers, we have used X-ray diffraction and vibrational spectroscopy (infrared and Raman) to derive information on crystal and molecular structures of COM and COD. In this paper, we complete the synthesis and analysis on the third form, COT, and present a comparative study of the data collected from the three crystalline states. The experiments clearly highlight the role played by the H2O molecules linked within the structure by different kinds of hydrogen bonds. The vibrational assignment of the infrared and Raman bands are critically proposed. The fact relevant for the work in biomedicine, cultural heritage and crystallography is that a simple examination of the spectra allows quickly to determine the chemical nature of the material in an unknown sample even in a minute quantity or in awkward experimental conditions.

The Raman spectra of H 2 and D 2 adsorbed on metal–organic framework-5 at various pressures (H 2 : 12.8 and 30.3 bar; D 2 : 2.2–24.5 bar) and temperatures (H 2 : 298 K; D 2 : 40–300 K) have been recorded. The shifts observed in the vibrational modes of the gases indicate that physisorption is responsible for the attractive interactions between the gas and the framework; these interactions are larger with respect to those detected for carbon materials.

The search for materials aimed at energy storage has prompted the synthesis of new materials which were obtained by pyrolysis of aromatic precursors under controlled conditions for the production of carbon based structurally disordered networks aimed at hydrogen or lithium storage. Obviously these materials consist of fully insoluble mixtures of different molecular species which escape the traditional physico-chemical techniques for structure determination. With the purpose of overcoming this difficulty we have developed and report here a systematic vibrational spectroscopic work which lays the basic concepts to be considered in the structural understanding of the molecules studied and can be extended to similar classes of complex carbonaceous materials. The (partial) structure of these systems and some of the reaction pathways at the molecular level can be inferred from the spectroscopic signals presented and discussed to be taken as key features for structural analysis.

Modern astronomical spectroscopy makes use of multi-aperture slits placed in the focal plane of telescopes before light enters the spectrograph. Multiple object spectroscopy (MOS) allows several spectra to be obtained simultaneously with a multiplexing gain from the order of dozens of objects in 4m class telescopes to few hundreds in larger 8 m telescopes. Many of these devices make use of metal plates which are punched, milled or laser cut and can be used only for observation of a given astronomical target. A typical observing night requires from 4 to 20 MOS masks, which have to be prepared during an off-line procedure, usually days before. Here we report an innovative technique to carry out multi object spectroscopy based on changes of properties of photochromic materials. Photochromic MOS masks consist of polymer thin films which can be made opaque or transparent in a restricted wavelength range using alternatively UV and visible light. Slit patterns can thus be easily written by means of a red diode laser on a UV preflashed plate. Writing time for a 10 × 10 arcmin plate is a few minutes and the whole procedure can be performed promptly after the acquisition of the field image and without mechanical debris as in milling or laser cutting. A computer controlled writing device suited for the AFOSC camera of the Asiago 1.8m telescope was built. The same focal plane mask can be UV erased and used more than 450 times. High contrasts have been reached by means of an appropriate passband filter in the light beam of the spectrograph. Our first successful observation run took place in January 2003. Spectra of selected stars in the crowded M67 cluster field and emission lines from the gaseous planetary nebula M97 were obtained. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Since photochromic molecules occur as two stable forms, they can be used to make optical memories. The readout process must preserve the information stored and can be carried on by using mid-IR light and exploiting the differences in the IR spectrum between the two forms. Three diarylethenes with different electroactive lateral substituents have been studied theoretically (B3LYP 6-31G**) to understand the effect of the substituent on the difference in absorbtion intensities of the vibrational spectrum. Calculations show that the presence of a donor group in the molecule enhances the absorbtion intensity of some normal modes of the molecule in the closed form. The molecule with a donor side group has been synthesized, a film was deposited on a substrate, a simple setup with a multibolometer camera has been built and patterns written on the film were read.

The study of the temperature-dependent Raman spectra of n-alkanes from the solid through melting and in the melt phase reveals that short intermolecular correlation can occur in the melt forming at Tm and just above Tm a sizable concentration of extended trans C−C bonds sequences. The mean length of these trans sequences is not less than approximately 5 units. The implications of these observations regarding the mechanism of crystallization of n-alkanes are discussed.

Diarylethenes bearing electro-donating and electro-withdrawing substituents in the 5,5‘-positions of the thiophene unit were studied theoretically (DFT, B3LYP) to understand the effect of the substituents on the infrared spectrum in the two stable forms. The photochromic molecule with the electro-donating substituent showed the largest difference in the infrared (IR) spectrum due to the push−pull−push structure. It was chosen to build a memory film with a readout process in the mid-IR. Information written on the photochromic film was read using a setup based on an infrared camera (multibolometer) and a filtered broadband Globar source. The results showed that the readout process worked without matching any specific absorption band. A good contrast was obtained also with a single camera frame (45 ms).