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This work studies the photochemical and thermal decompositions of azidoacetonitrile (N3 CH2 CN) from both the experimental and theoretical points of view. The data of the photochemical experiments are taken from the literature, while the thermal decomposition have been carried out by us. In addition, we have performed ab initio calculations of the multiconfigurational type [complete active space self-consistent field (CASSCF) and the multistate multireference perturbation theory (MS-CASPT2)]. It is found that the first step of both type of decompositions is N2 elimination and formation of closed shell singlet nitrene. Afterwards, the nitrene tends to rapidly rearrange into formimidoyl cyanide (HNCHCN). As both reactions progress, the imine isomerizes into formimidoyl isocyanide (HNCHNC). The photoisomerization of the imine takes places thorough a conical intersection, while the same reaction on the ground electronic state occurs via a conventional transition state. The last step of the global reaction is decomposition of the imines into HCN and CNH. In photochemical conditions, the conjunction of the imines and its dissociation products (HCN and CNH) yields adenine.

To date most studies of the impact of school-based sex education have focused either on specific, local interventions or experiences at a national level. In this paper, we use a new cross-country dataset to explore the extent to which laws on sex education affect teenage pregnancy rates in developed countries. We find some evidence that laws mandating sex education in schools are associated with higher rates of teenage fertility. Parental opt out laws may minimise adverse effects of sex education mandates for younger teens. The estimated effects of mandatory sex education are robust to some but not all of our specifications designed to tease out causality. Taken together, changes in national laws relating to sexual health are unable to explain the significant declines in teenage pregnancy rates, which have been observed in many developed countries in recent years.

[EN] BACKGROUND: The growing need to classify the origin of honey in a simple way is leading to the development of affordable analytical equipment that is in-line and manageable, enabling rapid on-site screening. The aim of this work was therefore to evaluate whether an electronic tongue (made of four metallic electrodes: Ir, Rh, Pt, Au), based on potential multistep pulse voltammetry with electrochemical polishing, is able to differentiate between honey samples from Spain, Honduras, and Mozambique. RESULTS: It was demonstrated, for the first time, that automatic pulse voltammetry, in combination with principal component analysis (PCA) statistical analysis, was able to differentiate honey samples from these three countries. A partial least squares (PLS) analysis predicted the level of certain physicochemical parameters, the best results being for conductivity and moisture with correlation coefficients of 0.948 and 0.879, whereas the weakest correlation was for the sugars. CONCLUSION: The tool proposed in this study could be applied to identify the country origin of the three types of multifloral honey considered here. It also offers promising perspectives for expanding knowledge of the provenance of honey. All of this could be achieved when a comprehensive database with the information generated by this electronic tongue has been created. © 2019 Society of Chemical Industry, This study forms part of the projects funded by the Ministerio de Economía y Competitividad, the Agencia Estatal de Investigación, and the Fondo Europeo de Desarrollo Regional (AGL2016-77702-R) and by the Programa ADSIDEO-cooperación 2016 of the Centro de Cooperación al Desarrollo de la Universitat Politècnica de València, Spain, for which the authors are grateful.

The fly-in/fly-Out (FIFO) or, drive-in/drive-out (DIDO) labour system is a long-distance commuting work arrangement to attract workers towards remote mineral or fossil fuel extraction areas, where they work in shifts and then return to their usual place of residence located in a different region. Along with more and cheaper transportation alternatives, the use of FIFO/DIDO systems have importantly increased in last decades around the world, which has translated to FIFO/DIDO systems operating even when already established cities are present in extractive regions. This paper uses the case of Chile, one of the most important mining countries in the world, to explore whether and in what extent these labor systems influence wage compensations. We find that FIFO/DIDO commuters obtain an average wage compensation of 2.4 per cent per commuted hour.

We present a generalization of the transition state search using chemical dynamics simulations (TSSCDS) methodology (discussed in a previous study) which allows the topographical characterization of intermolecular potential energy surfaces (IPES) for non-covalently bound complexes (vdW-TSSCDS). Starting from a single random input geometry, we show that vdW-TSSCDS is able to globally and automatically locate stationary points of an IPES, even in limiting cases such as extremely flat regions or nontrivial topologies (eg, bifurcation points). The basic idea is the expression of the connectivity matrix in block structure, where diagonal blocks correspond to the isolated fragments and off-diagonal blocks provide the intermolecular connectivity. To this end, we introduce a new definition of bound or not, in a non-covalent sense, utilizing an extra set of van der Waals distances, which encompasses all kinds of non-covalent distances. To discuss the use of the vdW-TSSCDS method, we present a series of 2-body van der Waals systems, namely, Ar-Benzene (3D), N2-Benzene (6D) and H2O-Benzene (9D). Finally, we further illustrate its capabilities by presenting some applications for n-body problems (n ' 2), (H2O)2-Benzene (12D) and (H2O)3-Benzene (21D), as well as to a reactive, fully-flexible, system (Benzene-NO2)+ (39D) in which the simultaneous breaking/formation of both covalent and non-covalent interactions takes place.

9 pags. 6 figs., In this work, the adsorption of a type of cruciform system integrated by an anthracene central part and two side chains with a pyridine-vinyl structure (DPAC) was studied on plasmonic nanoparticles of silver and gold. The adsorption was investigated by surface-enhanced Raman scattering, which reveals very valuable information about both the interaction mechanism and the molecular orientation. The highest Raman enhancement was measured on Ag nanostars due to the combination of gaps and tips in these nanostructures. The changes observed in the surface-enhanced Raman scattering spectra indicate that the adsorption of DPAC on the metal is bifunctional in the case of Ag and Au nanoparticles. Considering that the Raman signals enhancement is several orders of magnitude higher in gaps in relation to regions out of these areas, it is estimated that the enhancement ability of DPAC in Ag nanostars is so high that it allows the detection of a concentration close to pM., This work was supported by MINECO under FIS2014‐52212‐R and CTQ2015‐65816‐R projects. P. Leyton acknowledges to the project FONDECYT 1140810 as wellas the FONDEQUIP EQM130170 project from CONICYT.E. Imbarack acknowledges the financial supports fromBeca Doctorado Nacional N°21140360 CONICYT.

This work evaluates the capacity of a potentiometric electronic tongue to differentiate between types of honey (orange blossom, rosemary, thyme, sunflower, winter savory and honeydew honey) according to their antioxidant level. The classical procedures used to evaluate the antioxidant potential of honey are inappropriate for in situ monitoring on reception of batches of raw honey in the packaging industry. They are also destructive, time-consuming and very tedious, requiring highly expert analysts and specialised equipment.; Results: The electronic tongue system made with Ag, Ni, Co, Cu and Au was able to not only differentiate between types of honey but also to predict their total antioxidant capacity. The discrimination ability of the system was proved by means of a fuzzy ARTMAP type ANN, with 100% classification success. A prediction multiple linear regression model showed that the best correlation coefficient was for antioxidant activity (0.9666), then for electrical conductivity (0.8959) and to a lesser extent for aw , moisture and colour.; Conclusion: The proposed measurement system could be a quick, easy option for the honey packaging sector to provide continuous in-line information about a characteristic as important as the antioxidant level. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

In this paper, we estimate the size of the wage premium necessary to compensate for remoteness incurred by workers compared to the city size productivity effects. We construct five urban hierarchy tiers for cities in Chile based on their level of remoteness from the urban system. We then contrast the effect generated by these variables on worker wages. We report a positive gradient of wages the higher the size of the urban tier and a loss in wages that can reach 35 percent for more remote cities.

A comprehensive interpretation of single and multichannel seismic reflection profiles integrated with biostratigraphical data and log information from nearby DSDP and ODP wells has been used to constrain the late Messinian to Quaternary basin evolution of the central part of the Alboran Sea Basin. We found that deformation is heterogeneously distributed in space and time and that three major shortening phases have affected the basin as a result of convergence between the Eurasian and African plates. During the Messinian salinity crisis, significant erosion and local subsidence resulted in the formation of small, isolated, basins with shallow marine and lacustrine sedimentation. The first shortening event occurred during the Early Pliocene (ca. 5.33-4.57 Ma) along the Alboran Ridge. This was followed by a major transgression that widened the basin and was accompanied by increased sediment accumulation rates. The second, and main, phase of shortening on the Alboran Ridge took place during the Late Pliocene (ca. 3.28-2.59 Ma) as a result of thrusting and folding which was accompanied by a change in the Eurasian/African plate convergence vector from NW-SE to WNW-ESE. This phase also caused uplift of the southern basins and right-lateral transtension along the WNW-ENE Yusuf fault zone. Deformation along the Yusuf and Alboran ridges continued during the early Pleistocene (ca. 1.81-1.19 Ma) and appears to continue at the present day together with the active NNE-SSW trending Al-Idrisi strike-slip fault. The Alboran Sea Basin is a region of complex interplay between sediment supply from the surrounding Betic and Rif mountains and tectonics in a zone of transpression between the converging African and European plates. The partitioning of the deformation since the Pliocene, and the resulting subsidence and uplift in the basin was partially controlled by the inherited pre-Messinian basin geometry. © 2013 The Authors. Basin Research © 2013 John Wiley and Sons Ltd, European Association of Geoscientists and Engineers and International Association of Sedimentologists.

[EN] Trapped: Mesoporous silica nanoparticles were loaded with a fluorescent guest and functionalized with octadecyltrimethoxysilane. The alkyl chains interact with paraffins, which build a hydrophobic layer around the particle (see picture). Upon melting of the paraffin, the guest molecule is released, as demonstrated in cells for the guest doxorubicin. The release temperature can be tuned by choosing an appropriate paraffin. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., Financial support from the Spanish Government (projects MAT2009-14564-C04-01 and SAF2010-15512) and the Generalitat Valenciana (projects PROMETEO/2009/016 and PROMETEO/2010/005) is gratefully acknowledged. L.M. thanks the Generalitat Valenciana for a VALi+d postdoctoral contract. We thank UPV electron microscopy and CIPF confocal microscopy services for technical support.

We report the preparation of a MCM-41 mesoporous material that contains the dye [Ru(bipy) 3 ]Cl 2 (bipy= bipyridine) inside the mesopores and functionalised with suitable binding groups at the entrance of the pores. Solids S1―S3 were obtained by the reaction of the mesoporous material with N-methyl-N'-propyltrimethoxysilylimidazolium chloride, N-phenyl-N'-[3-(trimethoxysilyl)propyl]thiourea, or N-phenyl-N'-[3-(trimethoxysilyl)propy1]urea, respectively. A study of the dye delivery of these systems in buffered water (pH 7.0, 2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid (HEPES), 10 ―3 mol dm ―3 ) in the presence of a family of carboxylate ions was carried out. In the interaction of the anions with the surface of the solids, the response depends on the characteristics of the binding groups (i.e., imidazolium, urea and thiourea) at the pore outlets and their specific interaction with the corresponding anion. The interaction of long-chain carboxylate ions with the binding sites at the surface of the solids resulted in a remarkable inhibition of the delivery of the dye. This inhibition was observed clearly for the dodecanoate anion, whereas the octanoate, decanoate, cholate, deoxycholate, glycodeoxycholate and taurocholate anions induced a certain pore blockage that varied according to the solid studied. The interaction of smaller anions, such as acetate, butanoate, hexanoate and octanoate, with the solids had no effect on the dye release process. The possible use of the gating system for the chromo-fluorogenic detection of anionic surfactants through selective dye delivery inhibition was also explored. Molecular dynamic simulations that use force-field methods have been made to theoretically study the capping carboxylate mechanism. The calculations are in agreement with the experimental results, thus allowing a representation of the dye delivery inhibition in the presence of long-chain carboxylate ions.

Chemical warfare (CW) agents are toxic chemicals that have been used in several terrorist attacks in recent years. Among CW species, nerve agents are probably the most dangerous; their high toxicity and facile synthesis underscores the need to detect these lethal compounds with quick, reliable procedures. Analytical methods based on enzymatic assays and physical measurements have generally been used to detect these hazards. However, these protocols usually have limitations such as low selectivity, poor portability, and a certain level of complexity. In recent years, several chromogenic and fluorogenic sensors, and reagents for the detection of nerve agents have been described. For instance, approaches that involve perborate-mediated oxidation of organophosphorus agents, fluorescent probes based on polyethylene terephthalate (PET), assays that use oximate-containing derivatives, molecularly imprinted polymers, nanoparticles, carbon nanotubes, porous silicon, displacement-like procedures, and cyclization reactions in push–pull chromophores have been reported. Most of these protocols rely on changes in fluorescence properties, whereas few examples deal with color modulations. Colorimetric detection is particularly appealing because it uses low-cost, widely available instrumentation and allows assays to be detected with the naked eye. However, the development of selective, sensitive chromogenic probes for the detection of deadly chemical species is still rare. Given our interest in the design of novel hybrid organic– inorganic materials as probes, we focused on the preparation of a new optical test for the detection of nerve agent mimics based on nerve agent control of mass transport to the surface of functionalized silica nanoparticles. The chromogenic approach (Scheme 1) involves the use of silica nanoparticles that are functionalized with two different subunits— thiol groups (SH) and aliphatic alcohols (OH). The role of the

A new hybrid system for surfactant removal from water has been developed using mesoporous material (MCM-41) functionalised with suitable binding groups. Solid S1, S2 and S3 were prepared by reaction of the mesoporous material with N-methyl-N′-(propyltrimethoxysilyl)imidazolium chloride, (3-aminopropyl)trimethoxysilane or 4-[(triethoxysilylpropylthio)methyl]pyridine, respectively. The functionalised materials were characterised following standard solid-state techniques. The final prepared solids consist of a siliceous MCM-41-type mesoporous support with the surface decorated by imidazolium, amine and pyridine binding groups suitable for anion coordination. Equilibrium adsorption studies of linear alkylbenzenesulfonate (LAS) using S1, S2 and S3 in water have been carried out. The obtained adsorption data were correlated with a Langmuir isotherm model that gives an acceptable description of the experimental data. The maximum surfactant uptake/binding site (mol mol–1) and the surfactant adsorption capacity (mmol g–1) for materials S1, S2 and S3 were calculated. S1 shows a positive-charged functionalised surface that is independent of the pH of the solution, whereas S2 and S3 are functionalised with neutral groups that need to be protonated in order to display electrostatic binding interactions with the anionic surfactants. Therefore, whereas the adsorption capacity of S1 is pH-independent, S2 and S3 display larger LAS adsorption at acidic pH. The adsorption ability at a certain pH follows the order S1 >> S3 > S2. A remarkable maximum surfactant adsorption of 1.5 mmol per gram of material was observed for S1 at neutral pH. S2 and S3 behave as poorer adsorbents and show maximum surfactant adsorption of 0.197 and 0.335 mmol per gram of material, respectively, at pH 2.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Electronic tongues were developed some ten years ago. These systems consist of an array of nonspecific sensors and a signal processing unit. The sensor signals are processed by pattern recognition methods which makes possible the extraction of specific properties from the sample. Depending on the calibration, attributes such as quality or taste can be determined. These systems also detect changes in the sample that they are not calibrated for which makes possible the detection of anomalous occurrences. Such sensor systems are suitable for process control and surveillance. Important factors are the sensitivity and stability, specifically the sensor's ability to respond to small changes and to provide true and reproducible readings over time. Problems with sensor stability are commonly referred to as drift. The major topic of this thesis is the improvement of long term stability for electronic tongues used in liquid process applications. Drift counteractions, such as renewal of the electrode surface by polishing, was compared with mathematical correction methods. Since drift is induced by the environment of the sensor, mathematical correctional actions must include reference samples and the induced drift must be identical between measurements. These conditions restrict and complicate the use of mathematical drift counteractions. It was found that mechanical polishing renewed the electrode surfaces, and that the induced drift was unique for each sample. The sample induced drift pattern can be treated as information from the sample, but only if the sensors are renewable in a repeatable way. Applications where polishing the electrode surfaces are necessary to obtain repeatable analyses are described, such as the detection of urea and measurements in corrosive environments such as wine. Electrochemical oxidation of urea in water is difficult to use for analytical purposes because of residues left on the electrode surface. An important result from this thesis is that mechanical cleaning of the electrodes between samples gives sensor signals that are both repeatable and proportional to the concentrations of urea and glucose. An experimental design was employed for optimal effect of the calibration of urea in the presence of glucose as a disturbance in the sample. The goal was to minimize the correlation between the two analytes. This made possible the prediction of both analyte concentrations. Wine is a complex sample to analyze with many sources of disturbances for electrochemical measurements. The carefully planned experiments and calibrations reported in this thesis minimized covariance and background effects. A method for prediction of bisulfite, histamine and ascorbic acid concentrations in wine was developed. The method was tested with spiked samples of white-, red-, rose-wines and even apple juice. The reproducibility of the measurements was excellent. Since polishing renewed the electrodes between measurements, a validation performed one month after the calibration was also predicted with good results. This demonstrated that the renewal of the electrodes eliminated special requirements for maintenance and storage of the sensor. Drinking water surveillance has been performed with an electronic tongue. The potential of using a voltammetric electronic tongue for multicomponent analysis of compounds in drinking water has been evaluated. By using such a non-selective sensor it was possible to detect anomalies without the need of a specific sensor for each type of event. The device can be calibrated for the most likely events, and it can also be used for sensing and alarm when exceptional events occur. The detection of surface active species like detergents is normally done by titration. An in-line sensor that could control the washing process by detecting the concentrations of detergents during the different steps in a wash cycle could enhance the performance of washing machines. An electronic tongue was used to predict concentrations of detergents in samples from different stages in the washing procedure. The tongue was compared with a much simpler conductivity meter, and due to the covariation of supporting electrolyte, both sensors were able to predict concentrations of ionic surfactants. The electronic tongue showed promising results in predicting also non ionic surfactants where the conductivity meter failed. The detection mechanism was probably due to shielding the electrode surface from electro active species in the samples.

Bifunctionalised hybrid silica nanoparticles have been synthesised and characterised, and their optical emission properties in the presence of certain anions in acetonitrile solutions have been studied. The alkoxysilane derivatives N-butyl-N′-[3-(trimethoxysilyl)propyl]thiourea (1), N-phenyl-N′-[3-(trimethoxysilyl)propyl]thiourea (2) and 3-[(anthracen-10-yl)methylthio]propyltriethoxysilane (3) were prepared and used to functionalise uncoated LUDOX silica nanoparticles with a mean diameter of 18 ± 2 nm. The functionalisation of the nanoparticle surfaces was carried out by two different approaches. The first approach relies on the consecutive grafting of the two subunits. In this protocol, the nanoparticles were first functionalised with anthracene derivative 3 (solid NA), and then treated with the corresponding binding sites 1 or 2 to result in the NA-Pt3 and NA-Bt3 solids. The second approach deals with the simultaneous grafting of 1 or 2 and the signalling subunit 3 in different ratios. This method was used for the preparation of the NA1Pt1, NA1Bt1, NA1Pt3 and NA1Bt3 nanoparticles. The bifunctionalised silica nanoparticles were characterised by using standard techniques. Acetonitrile suspensions of NA nanoparticles (5 mg in 20 mL) showed anthracene bands centred at ca. 350, 370 and 390 nm. Upon excitation at 365 nm, a typical emission band with fine structure in the 390–450 nm range was observed. Similar absorption and emission spectra were found for the bifunctionalised nanoparticles. The work is completed with a prospective study of the fluorescence of the prepared nanoparticles in the presence of organic (acetate, benzoate) and inorganic (F–, Cl–, Br–, CN–, HSO4– and H2PO4–) anions. The apparent binding constants (adsorption constants) for the interaction of NA-Pt3 with anions in acetonitrile were determined by performing a Langmuir-type analysis of fluorescence titration data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)

The synthesis, photophysical properties, protonation, and metal-ion coordination features of a family of nine aniline-based symmetrical squaraine derivatives are reported. The squaraine scaffold displays very attractive photophysical properties for a signalling unit. These dyes show absorption and weakly Stokes-shifted, mirror-image-shaped emission bands in the visible spectral range and there are no hints of multiple emission bands. The mono-exponential fluorescence decay kinetics observed for all the derivatives indicate that only one excited state is involved in the emission. These data stress the interpretation that squaraines can be regarded as polymethine-type dyes. From a coordination chemistry point of view, the squaraines possess four potential binding sites; that is, two nitrogen atoms from the anilino groups and two oxygen atoms from the central C(4)O(2) four-membered ring. These coordination sites are part of a cross-conjugated pi-system and coordination events with protons or certain metal ions affect the electronic properties of the delocalised pi-system dramatically, resulting in a rich modulation of the colour of the squaraines. The absorption band at around 640 nm is blue-shifted when coordination at the anilino nitrogen atoms occurs, whereas coordination to the C(2)O(4) oxygen atoms results in the development of red-shifted bands. Addition of more than one equivalent of protons or metal cations could additionally entail mixed N,O- or N,N-coordinated complexes, manifested in the development of a broad band at 480 nm or complete bleaching in the visible range, respectively. Analysis of the spectrophotometric titration data with HYPERQUAD yielded the macroscopic and microscopic stability constants of the complexes. Theoretical modelling of the various protonated species by molecular mechanics methods and consideration of some of the title dyes within the framework of molecular chemosensing and molecular-scale "logic gates" complement this contribution.

Dual-function hybrid material U1 was designed for simultaneous chromofluorogenic detection and removal of Hg(2+) in an aqueous environment. Mesoporous material UVM-7 (MCM41 type) with homogeneously distributed pores of about 2-3 nm in size, a large specific surface area exceeding 1000 m(2) g(-1), and nanoscale particles was used as an inorganic support. The mesoporous solid is decorated with thiol groups that were treated with squaraine dye III to give a 2,4-bis(4-dialkylaminophenyl)-3-hydroxy-4-alkylsulfanylcyclobut-2-enone (APC) derivative that is covalently anchored to the inorganic silica matrix. The solid was characterised by various techniques including X-ray diffraction, transmission electron microscopy, Raman spectroscopy, and nitrogen adsorption. This hybrid solid is the chemodosimeter for Hg(2+) detection. Hg(2+) reacts with the APC fragment in U1 with release of the squaraine dye into the solution, which turns deep blue and fluoresces strongly. Naked-eye Hg(2+) detection is thus accomplished in an easy-to-use procedure. In contrast, U1 remains silent in the presence of other thiophilic transition metal ions, alkali and alkaline earth metal ions, or anions ubiquitously present in water such as chloride, carbonate, sulfate, and phosphate. Material U1 acts not only as chemodosimeter that signals the presence of Hg(2+) down to parts-per-billion concentrations, but at the same time is also an excellent adsorbent for the removal of mercury cations from aqueous solutions. The amount of adsorbed mercury ranges from 0.7 to 1.7 mmol g(-1), depending on the degree of functionalisation. In addition, hybrid material U1 can be regenerated for both sensing and removal purposes. As far as we know, U1 is the first example of a promising new class of polyfunctional hybrid supports that can be used as both remediation and alarm systems by selective signalling and removal of target species of environmental importance. Model compounds based on silica gel (G1), fumed silica (F1), and micrometre-sized MCM-41 scaffolds (M1) were also prepared and studied for comparative purposes.

A family of azo dyes containing amide (1), urea (2), thiourea (3), carbamate (4) or amino (5) hydrogen-bond donating groups were synthesized and their response toward anions was studied. Acetonitrile solutions of 1–5 show bright yellow colours, due to charge-transfer bands in the 375–400 nm region, slightly modulated by the electron donor strength of the group attached to the 4′ end of the 4-nitroazobenzene scaffold. Anions of different shape and size (i.e., spherical F–,Cl–, Br– and I–, planar and tetrahedral oxoanions such as NO3–, H2PO4– and HSO4–, carboxylates such as acetate and benzoate and the linear anions cyanide and thiocyanate) were employed in the recognition studies. Two different effects were distinguished: (i) bathochromic shifts of

A way of classifying companies' postures concerning sustainable development is presented, which forms the basis for an evaluation of 36 companies from the Brazilian chemical industry. It was found that most of these companies have a more mature posture to this issue. The findings of the analysis reinforced the hypothesis that a company's strategic planning process is a determinant factor in defining its business postures towards sustainable development. By grouping the companies in the sample, it was also possible to reinforce the hypothesis that those companies with a more proactive posture give greater importance to sustainable development in the short-and long-term and have better results than those companies with a more reactive posture.

The heteroleptic osmium(II) complex [Os(L1)(Me-phtpy)][PF6]2 (L1 = 1-[4′-p-tolyl-(2,2′:6′,2″-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane, Me-phtpy = 4′-p-tolyl-2,2′:6′,2″-terpyridine) has been prepared, characterized and its potential use for chemical sensing purposes studied. The complex contains a polyazacycloalkane as “binding site” and a Os(tpy)22+ core that acts as a “signalling subunit”. The emission intensity of the osmium complex was quenched in acetonitrile/water (1:1 v/v) by Cu2+ and Ni2+. Potentiometric titrations of [Os(L1)(Me-phtpy)]2+ in the presence of Cu2+ were carried out in order to determine thermodynamic binding constants in acetonitrile/water (70:30 v/v, 0.1 mol·dm–3 tetrabutylammonium perchlorate). With Cu2+ the receptor [Os(L1)(Me-phtpy)]2+ forms the complex {Cu[Os(L1)(Me-phtpy)]}4+ at neutral pH. Moreover it undergoes two stepwise protonation processes at acid pH related to the partial protonation of the cyclam core and forms two hydroxo complexes at basic pH. The Ni2+ complexes of the osmium receptor [Os(L1)(Me-phtpy)]2+ are able to act as an anion fluorogenic chemosensor in acetonitrile/water mixtures. A displacement of the quenching effect to more acidic pH in the Ni2+–[Os(L1)(Me-phtpy)]2+ system was observed for anions in the order ATP > AMP > chloride. A prospective study of the use of the [Os(L1)(Me-phtpy)]2+ complex as a fluorogenic sensor for oxygen was also carried out by incorporation of the complex in sol-gel silica films made with TEOS and MTEOS. Significant quenching of the osmium fluorescence by oxygen was observed. The oxygen response of the films showed good stability and repeatability. The study suggested that theOs(tpy)22+ core might act as suitable signalling scaffolding in chemical sensing systems of cations, anions and gases.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)

A versatile procedure for anchoring dyes into the pores of multidimensional zeolites by including organic dye precursors in the synthesis gel has been developed. To prove the concept, an aniline-functionalised zeolite Beta was obtained by reaction of triethylorthosilicate (TEOS), tetraethylammonium hydroxide, and N-methyl,N-(propyl-3-trimethoxysilyl)aniline (MPTMSA) in the presence of HF. Further extraction of the structure-directing agents resulted in a highly crystalline, white, functionalised zeolite Beta containing anchored aniline groups. Similar organic functionalised molecular sieves (OFMS) have been explored as novel catalysts, but, as far as we know, OFMS have never been used as precursors for dye-immobilisation or to design new solid-based host systems for selective molecular sensing processes as is reported here. In a second step the solids containing dyes were prepared by reaction of the hybrid material with the appropriate reactives to obtain tricyanovinylbenzene, triphenylpyrylium, azoic, and squaraine derivatives. All these reactions are straightforward and involve electrophilic aromatic substitution or diazotisation reactions at the electron-rich aniline ring. The final dye-functionalised solid materials were isolated by simple filtration and washing procedures and have been characterised by a number of techniques. In all cases the Beta structure of the solid remains unaltered. Among the large number of areas where dye-containing zeolites might be of importance, we were interested in testing their unconventional use as heterosupramolecular hosts in chromogenic protocols. To check their potential use as chemosensors, microporous solids with anchored triphenylpyrilium and squaraine dyes were selected and used as sensors for the chromogenic discrimination of amines. It was found that the response of both solids to amines was basically governed by the three-dimensional (3D) solid architecture that tuned the intrinsic unselective reactivity of the pyrylium dye. By using new solid-state supramolecular chemistry protocols we believe that these, and similar future dye-zeolite hosts, might be promising new sensor materials allowing the visible discrimination of selected target guests by size and/or polarity within families or closely related molecules.

The synthesis and characterisation of a family of multi-channel receptors containing crown-cation binding sites anchored to a 1-aminophenyl-1,2,2-tricyanoethylene group is reported. The ligands L1–L6 bear a 1-aminophenyl-1,2,2-tricyanoethylene scaffolding which is simultaneously a redox-active group (showing reduction processes at moderately modest potentials) and an acceptor moiety in the 1-aminophenyl-1,2,2-tricyanoethylene chromophore. Additionally, dyes L1–L6 also show fluorescence emission. The colour variation of L1–L6 in acetonitrile in the presence of the metal cations Ag+, Cd2+, Cu2+, Fe3+, Hg2+, Pb2+ and Zn2+ has been studied. Selective hypsochromic shifts were found for the systems L4-Pb2+, L5-Hg2+ and L6-Hg2+. For Hg2+ with L5 and L6 and Pb2+ with L4, emission fluorescence enhancements most likely associated with metal coordination to the anilinium nitrogen were observed. The electrochemical behaviour of receptors L1–L6 was studied in acetonitrile with platinum as working electrode and [Bu4N][BF4] as supporting electrolyte. This family of receptors shows a one-electron reversible reduction process at around –0.70 V vs. SCE, attributed to the reduction of the tricyanovinyl group. Additionally, all the receptors also show the oxidation of the anilinium moiety at about 1.2–1.4 V vs. SCE. Significant anodic shifts of both reduction and oxidation waves were found in the presence of certain metal cations. The relationship of these multiple-channel signalling receptors with guest chemosensing and reconfigurable molecular-based logic gates is discussed. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

Several key issues concerning surface-enhanced Raman scattering (SERS) are discussed, especially the surface orientation of the adsorbate, the enhancement mechanism relevant in a particular experiment, and the dependence of SERS frequencies and intensities on the electrode potential. It is shown that ab initio calculations of energies, geometries, and vibrational frequencies are essential in order to understand the complex behavior displayed by SERS spectra, particularly calculations dealing with radical anions of adsorbates. The main conclusion is the confirmation of the presence of resonant charge transfer processes in SERS of aromatic molecules. Such resonant mechanism involves the transient formation of the radical anion of adsorbates such as pyrazine, pyridine, and derivatives. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem 104: 681- 694, 2005

The new ligands 13-anthrylmethyl-7-ferrocenylmethyl-1,4,10-trioxa-7,13-diaza-cyclopentadecane (L1) and 1-anthrylmethyl-4,8,11-ferrocenylmethyl-1,4,8,11-tetraaza-cyclotetradecane (L2) have been synthesised, characterised, and their potential activity as chemosensors towards the metal cations Ni2+, Cu2+, Zn2+, Cd2+, Hg2+ and Pb2+ studied in 1,4-dioxane/water (70:30, v/v). Both ligands L1 and L2 are difunctionalised receptors containing redox-active (ferrocene) and fluorescent (anthracene) signalling subunits. The crystal structures of [H2L1][PF6]2 and [CuL2][PF6]2 were determined by single-crystal X-ray procedures. Potentiometric experiments in dioxane/water (70:30, v/v; 0.1 M KNO3; 25.0 ± 0.1 °C) for L1 and L2 allowed the determination of protonation constants and complex stability constants with the Cu2+ and Pb2+ metal ions. They form stable complexes with both ligands and show stability constants with values close to those reported for similar complexes. The electrochemical and fluorescence behaviour of L1 and L2 was studied as a function of the pH and in the presence of the Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ metal cations. The fluorescence and electrochemical response of L1 and L2 is pH-dependent. Ligand L1 was able to electrochemically and selectively sense Pb2+ whereas L2 sensed Cu2+, Zn2+, and Cd2+ using electrochemical techniques. The maximum electrochemical shift (ca. 57 mV) was found for L2 in the presence of Cu2+ at pH = 8. Fluorescence studies showed that the emission intensities of L1 and L2 were selectively enhanced in the presence of Cu2+. Additionally, the [Cu(L2)]2+complex acted as anion-sensing receptor in acetonitrile. The oxidation potential of the ferrocenyl group of the [Cu(L2)]2+complex was cathodically shifted upon addition of anions. The largest electrochemical shift was observed in the presence of fluoride (210 mV). The fluorescence emission of the anthracene groups in [Cu(L2)]2+ was enhanced in the presence of fluoride, nitrate, and dihydrogenophosphate.

[EN] Gated community: Peptides anchored to the surface of silica mesoporous supports by a valid procedure act as gatekeepers. In this way, "zero release" supports that selectively deliver the cargo in the presence of a suitable peptidase are obtained (see picture, red spheres: cargo, colored chains: peptides). © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim., We thank the Spanish Government (projects MAT2009-14564-C04, CB07/01/2012, and BIO2007 60066), the Generalitat Valencia (project PROMETEO/2009/016, PROMETEO/2010/005), and the CIBER-BBN for their support.

The coordination behaviour of the ditopic receptor of 1-[p-(2,2′:6′,2′′-terpyrid-4′-yl)tolyl]-1,4,8,11-tetraazacyclotetradecane (L1) towards Co2+ in acetonitrile/water (70:30, v/v) has been investigated. At acidic pH values, the L1−H+−Co2+ system shows an oxidation wave at 150 mV vs. SCE, characteristic of Co2+ in a bis(terpyridine) environment. Upon addition of OH−, a reduction in the intensity of the wave at 150 mV is observed and a new oxidation wave appears at 1.30 V. This new wave is close to that found for [Co(cyclam)]2+ under similar working conditions. The electrochemical data thus suggest that there is a pH-controlled translocation of the Co2+ ion from the bis(terpyridine) to the cyclam environment. A similar inference can be made from the results of UV/Vis studies. A thermodynamic characterization of the L1−H+−Co2+ system has also been carried out. Stability constants have been determined in acetonitrile/water (70:30, v/v, containing 0.1 mol dm−3nBu4NClO4 at 25 °C) using potentiometric techniques. The following species were found: [Co(L1)2H4]6+, [Co(L1)2H3]5+, [Co(L1)H]3+, [Co(L1)]2+, and [Co(L1)(OH)]+. The 2:1 ligand-to-metal species [Co(L1)2H4]6+ and [Co(L1)2H3]5+ are assigned to complexes where Co2+ is coordinated by two terpyridine units. The [Co(L1)H]3+, [Co(L1)]2+, and [Co(L1)(OH)]+ species are assigned to complexes where the Co2+ cation is in the cyclam binding domain. The pH-induced Co2+ jumping between coordination sites is discussed in terms of the different basicities of cyclam and terpyridine. Co2+ jumping between coordination sites has also been studied by the sequential acidification of basic mixtures of L1 and Co2+. Under these conditions, the translocation was observed at a different pH value than when an acid-to-basic path was followed. The effect of anions such as phosphate and chloride on the translocation process has also been studied. In the presence of phosphate, translocation occurs at pH = 11 rather than at pH ≈ 8. The phosphate−L1 and phosphate−L1−Co2+ systems have been characterized by potentiometry and a remarkably good agreement has been found between the electrochemical and potentiometric data.

The Cu2+ complex of the ligand L1 (L1 = [Ru(tpycyclam)(mtpy)]2+, tpycyclam = 1-[4′-p-tolyl-(2,2′:6′,2′′-terpyridyl)]-1,4,8,11-tetraazacyclotetradecane and mtpy = 4′-methyl-2,2′:6′,2′′-terpyridine) is able to display a selective sensing response against anions such as ATP. The L1−Cu2+ system contains a Ru(tpy)22+ fluorescent core and a cyclam−Cu2+ subunit. The fluorescent response of the Ru(tpy)22+ core in an aqueous environment (acetonitrile/water, 70:30) is governed by the quenching produced by the Cu2+ cation. In the presence of anions the L1−Cu2+ system shows a rich emission fluorescent response. Electrochemical studies on the Cu(cyclam)2+ complex in propylene carbonate in the presence of certain anions allowed us to conclude that the interaction with the anions sulfate, phosphate, ATP, ADP and GMP is mainly electrostatic whereas chloride and bromide form axial covalent bonds with the copper atom in the Cu(cyclam)2+ complex. The addition of anions that coordinate at the axial positions of the square-planar Cu2+−cyclam subunit (such as Cl−, Br− and OH−) produced an enhancement of the emission intensity. This enhancement is attributed to the occupation of the apical positions of copper in the Cu2+−L1 complex that might reduce the probability of an interaction between the Cu2+ ions and the Ru(tpy)22+ groups reducing the quenching process and, consequently, resulting in an enhancement of the fluorescence. A prediction of the fluorescent behaviour with the anions sulfate, phosphate, ATP, ADP and GMP that give electrostatic interactions with the positively charged cyclam−Cu2+ and/or Ru(tpy)22+ centres is rather difficult. Potentiometric studies on the L1−Cu2+−H+−ATP system suggested that the [Cu(L1)(ATP)] complex is responsible for the quenching observed at basic pH in the presence of ATP. It is noticeable that the quenching of the intensity of the fluorescence due to ATP in the pH range 9 to 10 is selective and no other anion studied is able to quench the emission of the Ru(tpy)22+ core in this pH range.

N2 extrusion from hydrazoic acid, methyl azide, and ethyl azide to yield the corresponding nitrene has been studied with high-level ab initio calculations. Geometry optimizations of stationary points and surfaces crossing seams were carried out with the complete active space self-consistent field (CASSCF) method, and their energies were reevaluated with the second-order multireference perturbation (CASPT2) theory and corrected by the zero-point energy (ZPE). The analytic harmonic frequencies calculated at the CASSCF level have been used in the ZPE corrections. The decomposition reaction is a competitive mechanism between a spin-allowed and a spin-forbidden channel, giving the nitrene either in the singlet or triplet states. The energy barrier height for XN—N2 bond fission is approximately the same in both channels for each azide, respectively. The spin-orbit (H SO ) interactions were determined at the minimum energy point on the seam of crossing between the singlet and triplet surfaces, the value ranges from 43.9 cm −1 in hydrazoic acid to 43.3 cm −1 in ethyl azide. c

An electronic tongue (ET) based on pulse voltammetry has been used to predict the presence of nerve agent mimics in aqueous environments. The electronic tongue array consists of eight working electrodes (Au, Pt, Ir, Rh, Cu, Co, Ni and Ag) encapsulated on a stainless steel cylinder. Studies including principal component analysis (PCA), artificial neural networks (fuzzy ARTMAP) and partial least square techniques (PLS) have been applied for data management and prediction models. For instance the electronic tongue is able to discriminate the presence of the nerve agent simulants diethyl chlorophosphate (DCP) and diethyl cyanophosphate (DCNP) from the presence of other organophosphorous derivatives in water. Finally, PLS data analysis using a system of 3 compounds and 3 concentration levels shows a good accuracy in concentration prediction for DCP and DCNP in aqueous environments.