Abstract  Biodegradability was conducted according to OECD guideline n°301B. Sample biodegradability was equal to 55.9% after 28 days and 66.3% after 36 days.

Abstract  The gel relaxation times of two different poly[styrene-b-(ethylene-altpropylene)-b-styrene] (SEPS) ABA triblock copolymers in squalane at various concentrations has been measured by Theology. These relaxation times were compared with the results of previous time-resolved small-angle neutron scattering (TR-SANS) experiments, which measured chain exchange kinetics in SEP diblock and SEPS triblock micelles in squalane. The gels relaxed up to four orders of magnitude faster than expected based on the chain exchange measurements of equivalent diblock polymers. By accounting for two factors a bias toward shorter end-block lengths in the gel relaxation, and a reduction in the energy barrier to chain pullout caused by the triblock architecture a model is constructed that reconciles the surprisingly short gel relaxation times with the chain exchange times measured via TR-SANS.

Abstract  This study presents first results on angle-resolved, inelastic collision dynamics of thermal and hyperthermal molecular beams of NO at gas-liquid interfaces. Specifically, a collimated incident beam of supersonically cooled NO (2Π1/2, J = 0.5) is directed toward a series of low vapor pressure liquid surfaces ([bmim][Tf2N], squalane, and PFPE) at θinc = 45(1)°, with the scattered molecules detected with quantum state resolution over a series of final angles (θs = -60°, -30°, 0°, 30°, 45°, and 60°) via spatially filtered laser induced fluorescence. At low collision energies [Einc = 2.7(9) kcal/mol], the angle-resolved quantum state distributions reveal (i) cos(θs) probabilities for the scattered NO and (ii) electronic/rotational temperatures independent of final angle (θs), in support of a simple physical picture of angle independent sticking coefficients and all incident NO thermally accommodating on the surface. However, the observed electronic/rotational temperatures for NO scattering reveal cooling below the surface temperature (Telec < Trot < TS) for all three liquids, indicating a significant dependence of the sticking coefficient on NO internal quantum state. Angle-resolved scattering at high collision energies [Einc = 20(2) kcal/mol] has also been explored, for which the NO scattering populations reveal angle-dependent dynamical branching between thermal desorption and impulsive scattering (IS) pathways that depend strongly on θs. Characterization of the data in terms of the final angle, rotational state, spin-orbit electronic state, collision energy, and liquid permit new correlations to be revealed and investigated in detail. For example, the IS rotational distributions reveal an enhanced propensity for higher J/spin-orbit excited states scattered into near specular angles and thus hotter rotational/electronic distributions measured in the forward scattering direction. Even more surprisingly, the average NO scattering angle (⟨θs⟩) exhibits a remarkably strong correlation with final angular momentum, N, which implies a linear scaling between net forward scattering propensity and torque delivered to the NO projectile by the gas-liquid interface.

Abstract  The dependence of the adjusted retention volume, VD, in gas liquid chromatograph on carrier gas flow rate, u, was stu8ied for several solutes using 5% squalane statioyary phase and 40-60 mesh fluoropak 8 as support. In all cases VD increases in a stypwise fashion as u increases. In each step the rate of increase of Vplis intitially high, but gradually decreases until VD levels off. V R is further shown to be directly proportional to n, he number of adsorbant sites in the stationary phase recognised by a single analyte molecule during its paysage through the column and, based on this relationship between VD and n, a new model of gas chromatography applying the kinetics 6f gaseous adsorption at surfaces, and whose predictions are consistent with the experimental data above, is presented.

Abstract  The antibody and cell mediated immune responses induced by BHV-1 were analysed in cattle after vaccination and challenge exposure to the virulent strain LA of BHV-1. Animals were vaccinated intramuscularly (IM) with inactivated virus vaccines against BHV-1 containing either a water in mineral oil adjuvant (W/O), a water in mineral oil adjuvant plus Avridine (W/O O + Avridine) or sulfolipo-cyclodextrin in squalane in-water emulsion (SL-CD/S/W). No significant differences were registered in the antibody response induced by the three evaluated vaccines. However, the BHV-1 specific cell-mediated immunite response was stronger and appeared earlier when SL-CD/S/W was included in the formulation. The efficacy of the vaccines was also evaluated after intranasal challenge of the calves with a virulent BHV-1 LA strain. Animals vaccinated with SL-CD/S/W had reduced virus excretion and clinical symptoms compared with the mock-vaccinated animals. Comparison of levels of BHV-1 specific IgG2 and IgG1 with virus shedding revealed that, regardless of the adjuvant administered, animals showing BHV-1 specific IgG2/IgG1 ratios higher than 1 were those with a significant lower number of individuals shedding virus. Additionally, animals vaccinated with SL-CD/S/W presented no post-vaccinal reactions. These factors, combined with the higher efficacy and the ease of manipulation of the biodegradable oil, makes the vaccine formulated with this new adjuvant an important contribution for the veterinary vaccines industry. (C) 2000 Elsevier Science Ltd. All rights reserved.

Abstract    Squalene (SQ), a precursor of sterols and terpenoids is a functional lipid of high importance in the food and pharmaceutical sectors. SQ oxidation studies are rather limited compared with those for other olefins. The aim of the present study was to monitor the formation of SQ oxidation products under different conditions (temperature, air supply), to characterise the most abundant of them by spectroscopic techniques and then examine their pro-oxidant activity in a model lipid substrate. Squalane (SQA), the saturated analogue of SQ, was used as a reference compound. FT-MIR analysis indicated the presence of alcohols, epoxides, aldehydes, and ketones. GC-MS was used to characterise SQ primary oxidation and scission products. The presence of epoxides was further confirmed by means of 1H NMR and 13C NMR spectroscopy. It could be argued that SQ stability is due to its stereochemistry and specifically to the presence of methyl groups next to the double bonds. The pro-oxidant activity of SQ oxidation products was evident at 62 and 40°C and suppressed only in the presence of primary antioxidants, not of SQ. The present work adds to the characterisation of SQ oxidised products. To our knowledge their pro-oxidant activity has never been examined before. Practical applications: Characterisation of squalene oxidation products and assessment of their activity as pro-oxidants present both scientific interest regarding the kinetics and product identity as well as a practical impact in case this bioactive lipid is provided for consumption as a functional product. In the past, cholesterol oxidation products and more recently phytosterol ones attracted the interest of researchers, who studied the stability of the respective parent compounds for food safety reasons. Monitoring of the formation of SQ oxidation products under different conditions (temperature, air supply) and chemical characterisation of the most abundant of them by spectroscopic techniques. Examination of their pro-oxidant activity in a model lipid substrate. Squalene may exert a weak antioxidant activity due to competitive oxidation phenomena with the lipid substrate while its oxidation products have a pro-oxidant activity on purified olive oil model substrate that was suppressed only in the presence of primary antioxidants. [PUBLICATION ABSTRACT]

Abstract  The work in part 6 of this series (J. Phys. Chem. A 2009, 113, 4930), addressing the task of separating the effects of Heisenberg spin exchange (HSE) and dipole-dipole interactions (DD) on electron paramagnetic resonance (EPR) spectra of nitroxide spin probes in solution, is extended experimentally and theoretically. Comprehensive measurements of perdeuterated 2,2,6,6-tetramethyl-4-oxopiperidine-1-oxyl (pDT) in squalane, a viscous alkane, paying special attention to lower temperatures and lower concentrations, were carried out in an attempt to focus on DD, the lesser understood of the two interactions. Theoretically, the analysis has been extended to include the recent comprehensive treatment by Salikhov (Appl. Magn. Reson. 2010, 38, 237). In dilute solutions, both interactions (1) introduce a dispersion component, (2) broaden the lines, and (3) shift the lines. DD introduces a dispersion component proportional to the concentration and of opposite sign to that of HSE. Equations relating the EPR spectral parameters to the rate constants due to HSE and DD have been derived. By employing nonlinear least-squares fitting of theoretical spectra to a simple analytical function and the proposed equations, the contributions of the two interactions to items 1-3 may be quantified and compared with the same parameters obtained by fitting experimental spectra. This comparison supports the theory in its broad predictions; however, at low temperatures, the DD contribution to the experimental dispersion amplitude does not increase linearly with concentration. We are unable to deduce whether this discrepancy is due to inadequate analysis of the experimental data or an incomplete theory. A new key aspect of the more comprehensive theory is that there is enough information in the experimental spectra to find items 1-3 due to both interactions; however, in principle, appeal must be made to a model of molecular diffusion to separate the two. The permanent diffusion model is used to illustrate the separation in this work. In practice, because the effects of DD are dominated by HSE, negligible error is incurred by using the model-independent extreme DD limit of the spectral density functions, which means that DD and HSE may be separated without appealing to a particular model.

Abstract  Experimental and numerical studies have been performed to establish how liquid and vapor distributions of flammable liquids within an insulation matrix and that of residual oxygen may affect the propensity for spontaneous ignition to occur when the insulation is exposed to elevated external temperatures.

The experiments were performed at temperatures up to 500 K when squalane, which is involatile, and tetralin, which is volatile, were doped into 5-cm cubes of a microporous material. The center temperature, oxygen concentration, and liquid mass loss were measured continuously The distinctions between evaporative loss without exothermic oxidation of a volatile fluid and the exothermic oxidation leading to ignition of an involatile fluid were clearly established. There were two principal features. First, oxygen is never excluded completely from the pores of the insulation material even when the block is exposed to an external temperature equal to the normal boiling point of the fluid. In fact, a "plateau temperature," which is below the bailing point, is established at the center of the block, and this is maintained until virtually all evaporation has ceased. Second, only very small proportions of oxygen are consumed during the induction time leading to thermal ignition. Complete consumption occurs within the porous structure only at an advanced stage of combustion.

Numerical simulations were made including the chemical reaction, liquid evaporation, both fuel vapor and oxygen diffusion, and thermal transport through the block. A novel approach to the kinetic representation is used. The subtle interactions between heat and mass transport are explored, and the model is used to predict which of a series of liquid alkanes may be susceptible to ignition if they were to leak into hot lagging materials.

Abstract  Squalene is a natural triterpenoid present virtually in all taxonomic groups. Its use for improving human health is rooted in ancient human history as several Pacific nations consumed the oil from livers of deep-sea sharks with high squalene content to improve their health and extend the life. In addition to the use as nutritional supplement, this molecule finds today many applications in pharmacology and cosmetics, or as a valuable industrial lubricant. Broad application potential of squalene is related to its physico-chemical characteristics, antioxidant activity and to its ability to interact with cell membranes. The industrial use of squalene is limited by short natural resources. Even today squalene is acquired mainly from shark liver oil; however, this source is no more tenable from the environmental viewpoint. Plant sources (e.g. olives, amaranth seeds) and particularly microbial production are thus gaining importance as promising alternatives for extended industrial use of squalene.

Abstract  Quenching of the recombination fluorescence by an external electric field was investigated in hexane, tetradecane, and squalane solutions of p-terphenyl and 2.5-diphenyloxazole irradiated with X-rays. The kinetics of the recombination fluorescence I(E, t) was measured in a nanosecond time scale and the quenching-efficiency curves Q(E, t) = 1 - I(E, t)/I(0, t) were plotted. The dependence Q(E, t) was shown to have the specific character Q(E, t) = f(pt), where p = AE(2)D/r(c)(2). Here A is a constant dependent on the initial-distance distribution function of the charges, E is the electric field strength, D is a mutual diffusion coefficient of the recombining ions, and r(c), is the Onsager radius. The quadratic dependence of the parameter p on the electric field strength was shown to be a consequence of the diffusion-controlled reaction of ion recombination.

Abstract  Plasma-polymerized acetylene films are excellent primers for bending natural rubber (NR) to steel substrates. The purpose of this research was to determine the mechanisms responsible for adhesion at the NR/primer interface. Interactions between natural rubber and plasma-polymerized acetylene films were simulated using model systems containing squalene (C30H50) or squalane (C30H62), carbon black, sulfur, stearic acid, N, N-dicyclohexyl-benzothiazole-sulfenamide (DCBS), cobalt naphthenate, and diaryl-p-phenylene-diamine. Analysis of plasma-polymerized acetylene films before and after reaction with model rubber systems was accomplished using Fourier transform infrared spectroscopy (FTIR). The importance of the unsaturation in the reaction was demonstrated by comparing the behavior of the two model systems. In the squalane-based system, squalane itself was stable throughout the reaction, with only a slight reaction with the antioxidant and sulfur. No significant reactions occurred between the squalane-based model system and plasma-polymerized acetylene films with the exception of slight adsorption of antioxidant and zinc and/or cobalt stearate onto the films.

Reactions between plasma polymerized primers and the squalene-based model system were complex. Squalene itself went through double-bond migration. ZnO and cobalt naphthenate reacted with stearic acid to form zinc and cobalt stearates which then reacted with DCBS and sulfur to form zinc and cobalt accelerator perthiomercaptide complexes. These complexes reacted with squalene and with the primer film to form accelerator terminated, perthiomercapride pendant groups and, eventually, short polysulfide crosslinks. Since there was little reaction of squalane-based model rubber compounds with plasma polymerized primers but extensive reaction of squalene-based models, it was concluded that an intermediate formed in that reaction was responsible for crosslinking between squalene and the primer in the model system and for adhesion at the NR/primer interface in an actual bond.

Abstract  When beta-ionone-in-water emulsions are mixed with squalane-in-water emulsions, the slightly water-soluble, mobile beta-ionone undergoes mass transfer to the drops of highly water-insoluble, immobile oil squalane. We have investigated this compositional ripening process for emulsions stabilised either by particles or by surfactant molecules. For particle-stabilised emulsions, the swelling of the squalane-containing drops triggers droplet coalescence which causes the final swollen droplet radius to be proportional to the swelling ratio to the power of 1. Surfactant-stabilised emulsions swell without coalescence which causes the final droplet radius to be proportional to the swelling ratio to the power 1/3. Addition of excess, non-adsorbed particles to the particle-stabilised emulsions suppresses the swelling-triggered coalescence and causes a switchover from particle to surfactant behaviour.

Abstract  The possibility of stabilising oil-water mixtures using wax particles alone is reported. As judged from contact angle measurements, wax particles are hydrophobic and act as effective emulsifiers of water-in-squalane emulsions. Specific differences exist depending on the chemical composition of the particles. The effect of temperature on emulsion stability has been explored in detail. If particles are pre-adsorbed to water drop interfaces by emulsification at room temperature, subsequent increase of temperature leads to a progressive increase in sedimentation and coalescence as particles melt and desorb from interfaces. The temperature range over which this occurs is similar to that of the melting range of the particles alone. If however the particles are melted prior to emulsification, surface-active long chain ester or acid molecules adsorb to freshly created interfaces giving rise to excellent stability to coalescence at high temperatures. Rapid cooling of these latter emulsions enhances their long-term stability as solidification of the molten wax leads to a thickening of the continuous oil phase.

Abstract  Foaming properties of monoglycerol fatty acid esters that have different alkyl chain lengths were studied in different nonpolar oils, namely liquid paraffin (LP 70), squalane, and squalene. The effect of the hydrocarbon chain length of the surfactant, the concentration, the nature of the oil, and the temperature on the nonaqueous foam stability was mainly studied. Five weight percent of glycerol alpha-monododecanoate (monolaurin) formed highly stable foams in squalane at 25 degrees C, and the foams were stable for more than 14 h. Foam stability of the monolaurin/LP 70 and the monolaurin/squalene systems are almost similar, and the foams were stable for more than 12 h. Foam stability was decreased as the hydrocarbon chain length of the monoglyceride decreased. In the glycerol alpha-monodecanoate (monocaprin)-oil systems, the foams were stable only for 3-4 h, depending on the nature of the oil. However, the foams formed in the glycerol alpha-monooctanoate (monocaprylin)-oil systems coarsened very quickly, leading to the progressive destruction of foam films, and all of the foams collapsed within a few minutes. Foam stability decreased when the oil was changed from squalane to squalene, in both monocaprin and monolaurin systems. It was observed that, in the dilute regions, these monoglycerides form fine solid dispersions in the aforementioned oils at 25 degrees C. At higher temperatures, the solid melts to isotropic single-liquid or two-liquid phases and the foams formed collapsed within 5 min. Judging from the wide-angle X-ray scattering (WAXS) and the foaming test, it is concluded that the stable foams are mainly caused by the dispersion of the surfactant solids (beta-crystal) and foam stability is largely influenced by the shape and size of the dispersed solid particles.

Abstract  The general method of multicomponent mixtures analysis is presented. This method is based on absorption spectra in UV (aromatic hydrocarbons) or IR (aliphatic hydrocarbons) of pure analysed components and calibrating mixtures of well defined fraction components. The basis of the presented method is the correlation equation between spectra of tested mixtures and spectra of their pure components, measured in more than 200 points. The method was tested in UV and IR regions. Using 57 UV spectra of two-. three- or four-component hexane solutions of pyrene, anthracene, phenanthrene, naphthalene as well asortho-, meta- and para-xylenes, were tested. Similarly, using 38 IR spectra of two, three- or four-component solutions ofn-hexane, cyclohexane, cycloocta- 1,5-diene and squalane in CCl4, were examined. The content of deter-mined components varied from 3 to over 96% whereas the absolute determination error varied from 0 to 5.1% what corresponds to relative errors up to about 17% in both cases of IR and UV spectra. The preparation of testing samples was recognized as the main source of errors. The presented method is rapid because it omits the time-consuming stage of preparation of calibrated solutions. The analysis time is shorter than 5 min if spectra of pure components were measured earlier and computerised spectrophotometers were applied.

Abstract  Recently reported results indicate that the formation of surfactant-free, oil-in-water emulsions can be significantly enhanced by the almost complete removal of dissolved gases and that the reintroduction of dissolved gases does not immediately destabilize the already-formed emulsions. These initial experiments have been repeated and extended to include a wider range of organic liquids and the application of light scattering to determine droplet size and distribution. The earlier observations have been confirmed. In addition, a systematic trend was found between the solubility of the oil in water and the stability (lifetime) of the degassed oil droplets in water. The lower the solubility, the more stable the emulsion, and for oils that are sparingly soluble in water such as squalane, the small droplets remain stable for several weeks, with buoyancy separation being the main cause of instability of the large droplets with time. The addition of electrolytes, up to molar concentrations, substantially reduces the enhancement of the dispersions on degassing but appears to have little effect on the stability of the already-formed emulsions. The reduction of pH to about 2 significantly reduces both the enhancement of the dispersions on degassing and the stability of the already-formed emulsions. In contrast, the increase of pH to about 11 hardly affects the enhancement of the dispersions on degassing or the stability of the already-formed emulsions. We have confirmed the importance of dissolved gas and its association with the electrostatic effects, but we still cannot provide a complete explanation for the effect of degassing on the hydrophobic dispersions.

Abstract  In an attempt to elucidate the molecular basis for concentration (isotherm) effects on retention in gas-liquid chromatography, configurational-bias Monte Carlo simulations in the Gibbs ensemble were carried out to investigate changes in analyte partitioning caused by overloading a model chromatographic system with either an alkane or an alcohol. Squalane was used as the stationary-phase material, and the analytes included n-pentane, n-hexane, n-heptane, 1 -butanol, and 1-pentanol. Three systems were studied that differed in the mobile-phase composition: (i) a helium vapor, (ii) a n-hexane vapor, and (iii) a 1-pentanol-saturated helium vapor. While the amount of helium that partitions into the stationary phase is very small, both n-hexane and 1-pentanol partition strongly into and thereby swell the stationary phase. Although the swelling of the stationary phase leads to a reduction in the partition coefficients for the alkane solutes for both the n-hexane- and 1-pentanol-swollen stationary phases, the effects on the alcohol solutes differ markedly. Whereas saturation by n-hexane causes a decrease of the alcohol partition contants (to an extent similar to that for the alkane solutes), the saturation by 1-pentanol causes a dramatic increase of the alcohol partition coefficients; e.g., the Kovats index of 1-butanol increases by more than 150 Kovats units. The formation of hydrogen-bonded alcohol aggregates in the liquid phase is the microscopic origin for the dramatic effect of 1-pentanol saturation on the retention of alcohols.

Abstract  We demonstrate the first capture and analysis of secondary organic aerosol (SOA) on a droplet suspended in an aerosol optical tweezers (AOT). We examine three initial chemical systems of aqueous NaCl, aqueous glycerol, and squalane at ∼75% relative humidity. For each system we added α-pinene SOA-generated directly in the AOT chamber-to the trapped droplet. The resulting morphology was always observed to be a core of the original droplet phase surrounded by a shell of the added SOA. We also observed a stable emulsion of SOA particles when added to an aqueous NaCl core phase, in addition to the shell of SOA. The persistence of the emulsified SOA particles suspended in the aqueous core suggests that this metastable state may persist for a significant fraction of the aerosol lifecycle for mixed SOA/aqueous particle systems. We conclude that the α-pinene SOA shell creates no major diffusion limitations for water, glycerol, and squalane core phases under humid conditions. These experimental results support the current prompt-partitioning framework used to describe organic aerosol in most atmospheric chemical transport models and highlight the prominence of core-shell morphologies for SOA on a range of core chemical phases.

Abstract  Colloidal GaP nanowires (NWs) were synthesized on a large scale by a surfactant-free, self-seeded solution-liquid-solid (SLS) method using triethylgallium and tris(trimethylsilyl)phosphine as precursors and a noncoordinating squalane solvent. Ga nanoscale droplets were generated in situ by thermal decomposition of the Ga precursor and subsequently promoted the NW growth. The GaP NWs were not intentionally doped and showed a positive open-circuit photovoltage based on photoelectrochemical measurements. Purified GaP NWs were used for visible-light-driven water splitting. Upon photodeposition of Pt nanoparticles on the wire surfaces, significantly enhanced hydrogen production was observed. The results indicate that colloidal surfactant-free GaP NWs combined with potent surface electrocatalysts could serve as promising photocathodes for artificial photosynthesis.

Abstract  Cosmetics are used in practically all walks of life as a means of improving skin and beautifying complexion. In recent years, more and more attention has been paid to the cosmetic safety. In response to the cosmetic safety issue, the accurate measurement of the heavy metals in cosmetics is, therefore, particularly important. NMIs from different countries should establish their chemical metrology traceability system in this area, which includes both measurement methods research and certain CRMs development. It should be noted that because the matrix of many cosmetics is complex and the contents of the heavy metals are relatively low, it still is a challenging task to measure the analytes with high accuracy and precision.

CCQM-K106 followed up CCQM pilot study 'CCQM-P128: Pb, As measurements in cosmetic (cream)'coordinated by the National Institute of Metrology, China (NIM) in 2009. The cream was selected as the testing material, which is widely used as a daily skin care worldwide. This is the first CCQM key comparison regarding the measurement of toxic metal elements with the cosmetic matrix, which includes pure water, liquid paraffin, silicone oil, synthetic squalane, hyaluronic acid, glycerin, propylene glycol, allantoin, preservative and so on. The aim of the CCQM-K106 is to demonstrate the capability of participating NMIs and designated institutes in measuring the contents of poisonous elements, including lead, arsenic and mercury in a cosmetic sample (cream), and support CMC claims relating to inorganic elements in cosmetic materials and similar chemical industry products.

The cream matrix sample was prepared under the guidance of professional technicians. The formula of the cream was carefully chosen to match with a real cosmetic. The homogeneity and stability level of Pb, As and Hg in the cream sample were fit for the objective of the comparison. Each participant received two numbered bottles containing about 5g samples in each bottle. The instruction relating to CCQM-K106 was sent to each participant by e-mail, which consisted of technical protocol, results report form and inorganic core capabilities tables. The results were reported as mass faction (mg/kg). Calculation of the uncertainty expressed as a combined standard uncertainty and an expanded uncertainty at 95% confidence. In order to allow a sufficient evaluation of the comparison, the report was required to include a detailed description of the applied method of measurement, information about sample digestion and preparation, information about the reference material used for calibration.

The methods of measurement were free to be selected by the participants. For the sample treatment, most of the participants used microwave digestion method. For instrumental determination, a variety of techniques such as ICPMS, AAS, INAA were adopted by the participants. Most participants choose ID-ICP-MS method to measure Pb and Hg, which showed the better performance in terms of consistency and reliability of the measurement results.

The reference mass fraction values and associated uncertainties were calculated by different statistic ways. As the result, the median and uncertainty of median were proposed as the key comparison reference value (KCRV) and its associated key comparison reference uncertainty after removal of suspected extreme values.

In general, the performances of the majority of the CCQM-K106 participants are excellent, illustrating their measurement capability for Pb, As and Hg in a complex greasy matrix.

The results can be used further by any participant to support its CMC claim at least for a borate buffer. That claim will concern the pH method employed by the participant during this comparison and will cover the used temperature(s) or the full temperature range between 15 degrees C and 37 degrees C for the participant which measured pH values at the three temperatures.

Abstract  MARY spectroscopy is finding increasing use in the studies of transient organic radical ions and their reactions. Extending this technique to organometallic species will broaden the class of potential target compounds and can help answer important mechanistic questions in organometallic and spin chemistry. We probed this approach using a tailored Zn(hfac)(2)(PPO)(2) complex. The synthesized complex has quantum yield and fluorescence lifetime (n-decane solution) phi similar to 0.8 and tau similar to 1.3 ns, respectively. For this type of complex it is the first observation of MARY spectra different from those of free ligand, thus implying participation of the complex in the development of the observed signal. (C) 2011 Elsevier B. V. All rights reserved.

Abstract  A photophysical analysis of 10(-4) M solutions of 7-azaindole in hydrocarbon solvents including 2-methylbutane, 3-methylpentane, ethylcyclohexane, decalin, and squalane revealed that the viability of the two-proton phototautomerism in its dimer is clearly medium-dependent. However, in all media studied, a small tunneling contribution in the photoinduced double proton transfer continues to exist at low temperatures.