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The photochemical behavior of the protonated simplest nitrosamine [NH2NO-H](+) has been addressed by means of the CASPT2//CASSCF methodology in conjunction with the ANO-L basis sets. The relative stability of the different tautomers, namely, (1) NH2NOH(+), (2) NH3NO(+), and (3) NH2NHO(+), has been considered, and the corresponding tautomerization transition states have been characterized. With respect to the most chemically relevant species, it has been found that NH2NOH(+) corresponds to a bound structure, while NH3NO(+) corresponds to an adduct between NH3 and NO(+) at both CASSCF and CASPT2 levels of theory. Vertical transition calculations and linear interpolations on the homolytic dissociation of NH3NO(+) in combination with previous results on neutral nitrosamine [J. Chem. Phys. 2006, 125, 164311] and neutral N,N-dimethylnitrosamine [J. Org. Chem. 2007, 72, 4741] indicate that, in acidic diluted solutions, the protonation of nitrosamine takes place on the excited surface. The N-N dissociation channels have been studied both in ground and first excited singlet state. An S1/S0 conical intersection is found to be responsible for the photostability of NH2NOH(+). On the contrary, NH3NO(+) is photochemically unstable as its first excited state is purely dissociative. The latter species is characterized by a twofold reactivity: the formation of nitrosyl cation (NO(+)) in the ground state and the photorelease of physiologically relevant nitric oxide radical (NO) in its first excited state.

One of the fields where the idea of developing artificial electronic mammalian sense devices might be widely applied is in food analysis. In this field, one very complex attribute yet of great importance is that of freshness. For instance, freshness is one of the most significant parameters of fish quality in most markets. The state of fish freshness can be assessed by various indicators but most of them are costly, time-consuming and lack of aptness for in situ or on site monitoring. This makes that the development of simple and undemanding systems for the evaluation of fish freshness is still an unresolved goal. Based on this demand, we focused our attention on the use of unselective sensors for the potential development of low-cost and easy-to-use devices for the estimation of freshness. After a preliminary study with a number of different electrodes, simple Au and Ag wires were used for the analysis of the evolution of sea (Sparus aurata) bream fish stored throughout time. PCA and neuronal network analyses showed that it is possible to determine the post-mortem time elapsed in minced gilthead sea bream using simple potentiometric measurements, suggesting that this method could be used for the analysis and evaluation of fish freshness. In order to somehow validate the potentiometric protocol for freshness assessment, the method has been compared with the determination of fish freshness based on the analysis of the concentration of certain bio-molecules as a function of time after the death of the fish. Among different possibilities the K1 index that simultaneously measures the variation in the ATP metabolites inosine 5′-phosphate (IMP), inosine (Ino) and hypoxanthine (Hx) was used. A remarkable correlation has been found between the K1 index determined during 7 days and the potentials of the Au and Ag electrodes.

Molecular planarity of penta-p-phenylene (P5P) and several substituted derivatives with four side chains of various lengths, including deca(ethylene glycol) groups, is discussed by considering the changes in the intensity ratio between the Raman bands recorded at 1280 and 1220 cm(-1). The intensity ratio between both bands I(1280)/I(1220) shows a small increase with the size of the substituent, indicating a high rigidity for all these compounds, even those with long oligo(ethylene glycol) side chains. This result is important given that these phenylene derivatives are versatile building blocks for the construction of nanometric tripod-shaped adsorbates for biological applications since the side chains should prevent the nonspecific interaction with proteins.

A tripodal receptor functionalized with a stilbazolium dye derivative has been designed, synthesized and has been used for the colorimetric discrimination between certain ω-amino acids in mixed DMSO–water 90:10 v/v solutions.

We report on the development of an electronic tongue as potential tool for fish freshness determination. The studies were carried out following the evolution with time on fillet of cultured sea bream (Sparus Auratus). The electronic tongue consists of 16 potentiometric electrodes of the type metal, metal oxide and insoluble metal salts. Graphite was also used as electrode. Fish freshness indicators such as texture, pH, colour, microbial analysis, total volatile basic nitrogen (TVB-N) and biogenic amines were also determined versus time. The effectivity of the electronic tongue in the assessment of the evolution with time of fish fillets was evaluated. First the electronic tongue was used to classify samples according to time. Perceptron and adaptive resonance theory were used to discriminate between the data from different days. In a second step, the electronic tongue was used to predict the results obtained from chemical and biochemical analyses by building quantitative partial least square (PLS) models. A remarkable correlation was found between the electronic tongue formed by the 16 simple electrodes and parameters such as total biogenic amines, pH, TVB-N and microbial analysis with correlation coefficients larger than 0.98.

Potential energy surfaces, minimum energy reaction paths, minima, transition states, reaction barriers, and conical intersections for the most important atmospheric reactions of methyl nitrate (CH(3)ONO(2)) and methylperoxy nitrite (C(3)HOONO) on the electronic ground state have been studied (i) with the second-order multiconfigurational perturbation theory (CASPT2) by computation of numerical energy gradients for stationary points and (ii) with the density functional theory (DFT). The proposed mechanism explains the conversion of unreactive alkyl peroxy radicals into alkoxy radicals: CH(3)O(2) + NO=CH(3)OONO=CH(3)O + NO(2) left arrow over right arrow CH(3)ONO(2). Additionally, several discrepancies found in the comparison of the results obtained from the two employed approaches are analyzed. CASPT2 predicts that all dissociation reactions into radicals occur without an extra exit energy barrier. In contrast, DFT finds transition states for the dissociations of cis- and trans-methylperoxy nitrite into CH(3)O + NO(2). Furthermore, multiconfigurational methods [CASPT2 and complete active space SCF (CAS-SCF)] predict the isomerization of CH3ONO2 to CH3OONO to occur in a two-step mechanism: (i) CH(3)ONO(2) --CH(3)O + NO(2); and (ii) CH(3)O + NO(2) --CH(3)OONO. The reason for this has to do with the coupling of the ground electronic state with the first excited state. Therefore, it is demonstrated that DFT methods based on single determinantal wave functions give an incorrect picture of the aforementioned reaction mechanisms.

In the composition of commercial RuO 2 -containing resistive pastes there is also a significant amount of other electro-active metal oxides. Thus, when the pastes are used in the manufacture of thick-film electrodes, the electrochemical response is a complex contribution of all the electro-active metal oxides included in the paste composition. This is an attractive complex system whose electrochemical response has been studied and explained using a model based on surface activity changes of the solids involved in the redox processes. The developed model is able to describe the redox potential of the electrode as a function of the pH and explain the presence of certain anionic interferences.

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 family of N-crowned 4-p-(aminophenyl)-2,6-diphenylpyridines DA (1-6) has been synthezised, characterized, and studied as potential hosts for the signaling of cationic and anionic guests. The ditopic probes contain two coordination sites, a monodentate 2,6-diphenylpyridine and an anilino group with macrocycles of different ring size, denticity, and type of secondary heteroatom (O and/or S). X-ray structure analysis of aza-oxa-thia-crowned 5 indicated a largely planar chromophore. Optical spectroscopic and electrochemical studies revealed that the anilino-type donor (D) and the 2,6-diphenylpyridine acceptor (A) are strongly pi-conjugated, entailing intense intramolecular charge-transfer absorption bands at 340 nm. Binding studies with protons and metal ions (M = Cu2+, Zn2+, Hg2+, Fe3+, Pb2+, Ni2+, Cd2+) showed shifts of the band to the visible (440 nm) when coordination at the pyridine group occurs, strengthening its acceptor character. In contrast, no band in the visible is formed if binding takes place at the anilino group. Three different responses were found for various pairs of DA and M: selective metal coordination to D or A as well as coordination at both sites. A selective response was found for 5 and Hg2+. Because of the multitude of coordination-induced effects, the DA-M ensembles were further employed for differential anion sensing. In this protocol, the addition of an anion X to a certain, weakly coordinated DA-M can (i) lead to the formation of a ternary ion pair complex (DA-M-X), (ii) change the preference for A or D coordination, (iii) induce dissociation of the complex, or (iv) can have no effect. Various patterns of absorption changes were obtained as a result of different responses (i)-(iv) of the DA-M's in the presence of various X's. Data analysis yielded recognition patterns for acetate, F- and CN-, demonstrating the potential of simple chromogenic host-guest pairs for differential anion signaling.

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.

[EN] In recent years there have been numerous innovative educational initiatives that have proposed the use of synchronous communication tools to support university teaching. These proposals have proven their worth in specific application contexts such as: virtual tutoring, internationalization and mobility in masters and doctorates. However, their sometimes limited scope often makes it difficult to generalize results to other contexts and, thus, to pass from pilots to consolidated solutions. Within the framework of 2015 being declared as the International Year of Evaluation, this paper presents the results of a survey aimed to obtain the opinion of students regarding the use of synchronous communication tools for university teaching. The survey involved 436 students enrolled in subjects of various grade levels in degrees sucha as engineering, teaching, criminology and sports science, both in public and private universities. The results show a characterization of the interest, expectations and preferences of students with respect to the incorporation of computer communication tools as a mechanism to improve the learning process., [ES] En los últimos años han sido numerosas las iniciativas de innovación educativa que han propuesto el uso de las herramientas de comunicación síncrona como recurso tecnológico de soporte a la docencia universitaria. Dichas propuestas han demostrado sus beneficios en contextos de aplicación concretos como por ejemplo: la tutorización virtual o la internacionalización y movilidad en másteres y doctorados. Sin embargo, su alcance limitado dificulta a menudo la extrapolación de resultados a otros ámbitos docentes y, por tanto, la transformación de actividades que se pueden catalogar como piloto en soluciones de implantación consolidada. Con el trasfondo de la declaración del año 2015 como Año Internacional de la Evaluación, en este trabajo presentamos los resultados de un estudio dirigido a conocer la opinión del alumnado sobre el uso de herramientas de comunicación por Internet en la docencia universitaria. El estudio ha involucrado a 436 estudiantes matriculados en asignaturas de cursos diversos en titulaciones de ingeniería, magisterio, criminología y ciencias del deporte, en universidades públicas y privadas. Los resultados muestran una caracterización del interés, las expectativas y las preferencias de los alumnos con respecto a la incorporación de las herramientas informáticas de comunicación síncronas como mecanismo de apoyo y mejora del proceso de aprendizaje.

This paper is based on hyper spectral image analysis during organic violet cocoa bean fermentation. The hyper spectral vision has yielded valuable information on evolution during traditional fermentation. It has detected a significant parameter known as the anthocyanin reflectance index 2 (ARI2) of hyper spectral image of two bean regions (cotyledon and pulp) and has been correlated with the pH, temperature and moisture, the state of cocoa bean fermentation is determined.

Meta learning techniques such as cross-validation and ensemble learning are crucial for applying machine learning to real-world use cases. These techniques first generate samples from input data, and then train and evaluate machine learning models on these samples. For meta learning on large datasets, the efficient generation of samples becomes problematic, especially when the data is stored distributed in a block-partitioned representation, and processed on a shared-nothing cluster. We present a novel, parallel algorithm for efficient sample generation from large, block-partitioned datasets in a shared-nothing architecture. This algorithm executes in a single pass over the data, and minimizes inter-machine communication. The algorithm supports a wide variety of sample generation techniques through an embedded user-defined sampling function. We illustrate how to implement distributed sample generation for popular meta learning techniques such as hold-out tests, k-fold cross-validation, and bagging, using our algorithm and present an experimental evaluation on datasets with billions of datapoints.

This paper analyse the network of social demonstrations of the recent “Chilean Student Winter” occurred between 2009 and 2012 by studying the co participation patterns of social organizations using social network analysis. We describe main social actors and study the topological characteristics of the networks formed through social organizations, demonstrations and motives. Also, we study the change in the density of the network of demonstrations due to the rise of the “Chilean Student Winter” at 2011. We found that in spite that the “Chilean Student Winter” was mainly a student revolution, organizations of workers are the protagonist of this period according to the network analysis. Additionally, there are a significant change in the global cohesion or density of the demonstration’s network at 2011-12 in relation to 2009-2010.

This paper suggests that long distance commuters in Chile obtain a wage compensation of 8.7% on average when they commute among functional areas using data for 2009, while previous work identifies an average compensation of 19% using counties. Also, we estimated a higher compensation per hour. This estimated wage gradient is 6.1% per commuted hour and it is robust in several econometric specifications, a significantly higher number than the 0.06% previously reported in Jamett and Paredes (2013). Long distance commuters receive different wage compensation along the education distribution. Workers with a high education earn a higher wage compensation. This research suggests that the labor market alone does not seem to present evidence, which foreshadows a reduction in LDC flows. Moreover, this paper displays how the labor market offers workers higher incentives in order to maintain the flow of long distance commuting.

A new definition for the electrochemical cell constant in conductivity measurements is presented in this paper. Electrochemical Impedance Spectroscopy and DC pulses measurements have been carried out in non-Faradaic conditions in order to evaluate the effects of the cell geometry. The results obtained demonstrate that conductivity measurements are affected not only by the electrodes surface and separation but also by the cross section of the electrochemical cell. In order to obtain a linear behavior of the resistance versus the distance between electrodes, the cross section of the cell should be equal to the electrodes surface. Differences between the cell cross section and the electrodes surface produce a heterogeneous distribution of the electric field that causes the non-linear behavior for low values of the electrodes separation. This study shows that the reproducibility in electronic tongue and humid electronic nose measurements can be improved by designing an electrochemical cell structure that warrants a homogeneous distribution of the electrical field, which results in a reduction of the detection threshold in these types of system., Financial support from the Spanish Government (projects MAT2012-38429-C04-04 and IPT-2012-0069-310000) is gratefully acknowledged. The pre-doctoral scholarship granted to Roman Bataller Prats within the program "Formacion de Personal Investigador (FPI) 2012" from Universitat Politecnica de Valencia is gratefully acknowledged.

Voltammetric techniques (open circuit potential, linear polarisation resistance and cyclic voltammetry) have been applied to study the corrosion of carbon steel in water. The study has been performed in aqueous solutions for pH ranging between 7 and 12 in the presence of chlorides, sulphates, carbonates, nitrites and nitrates. Principal component analysis (PCA) was performed with the cyclic voltammetric data. Values of corrosion potential and corrosion current obtained with traditional methods are compared to the conclusions arisen by the PCA. These results show the ability of PCA for the evaluation and diagnosis of corrosion processes and not only that, it leads to the possibility of using steel working electrodes as ion sensors., The financial support from the Spanish Government (project MAT2009-14564-C04) Generalitat Valenciana (Valencian Regional Government; project PROMET EO/2009/016) and to 'Programa de Apoyo a la Investigacion y Desarrollo' de la Universidad Politecnica de Valencia (PAID-05-12) is gratefully acknowledged.

Generating synthetic data sets is integral to benchmarking, debugging, and simulating future scenarios. As data sets become larger, real data characteristics thereby become necessary for the success of new algorithms. Recently introduced software systems allow for synthetic data generation that is truly parallel. These systems use fast pseudorandom number generators and can handle complex schemas and uniqueness constraints on single attributes. Uniqueness is essential for forming keys, which identify single entries in a database instance. The uniqueness property is usually guaranteed by sampling from a uniform distribution and adjusting the sample size to the output size of the table such that there are no collisions. However, when it comes to real composite keys, where only the combination of the key attribute has the uniqueness property, a different strategy needs to be employed. In this paper, we present a novel approach on how to generate composite keys within a parallel data generation framework. We compute a joint probability distribution that incorporates the distributions of the key attributes and use the unique sequence positions of entries to address distinct values in the key domain.

We report here a general model for the description of the redox potential behaviour of certain electrodes in complex mixtures based on the study of redox process. The model has been developed theoretically and has also been experimentally verified. The model allows to state broad-spectrum equations which describe the behaviour of the potential of second and third order Faradic electrodes. Experimental verification of the model was carried out using common redox electrodes. The model was used to predict the redox behaviours in the following cases; (i) study of the potential variation of a Silver electrode as function of the pH, (ii) the redox potential of an Ag/AgCl electrode as function of the chloride concentration at different pH values, (iii) the potential of a Ag/AgBr electrode in the presence of certain amounts of chloride and (iv) the quantitative solid–solid transformation between AgBr and AgCl phases. There was found a remarkably good agreement between the experimental and theoretical values.

Surface-enhanced Raman spectra (SERS) of pyrimidine recorded on a silver electrode have been analyzed on the basis of a resonant Raman (RR) process involving photoexcited charge transfer (CT) states of the metal-adsorbate surface complex. The main feature of the SERS of benzene and azine derivatives is the enhancement of the totally symmetric ring stretching mode 8a due to Franck-Condon contributions related to the CT transition. Although this behavior is observed in the SERS of pyrimidine, its spectrum is also characterized by the strong enhancement of the nontotally symmetric mode 8b. This peculiar feature can be explained only by the redistribution of the Franck-Condon factors between the 8ab pair of vibrations originated by the descent in symmetry occurring when pyrimidine is bonded to silver nanoclusters. This conclusion is a new evidence of the main role of the RR-CT enhancement mechanism in the SERS of aromatic molecules and shows once again the usefulness of the methodology developed by our group in order to analyze these complex spectra.

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)

The potential energy surfaces for the dissociation of nitramide (NH(2)NO(2) --> NH(2) + NO(2)) and nitromethane (CH(3)NO(2) --> CH(3) + NO(2)) and the nitro-nitrite rearrangement of these nitrocompounds (RNO(2) --> RONO) as well as the dissociations of the nitrite isomers (RONO --> RO + NO) have been studied with the second-order multiconfigurational perturbation theory (CASPT2) by computation of numerical energy gradients for stationary points. It is found that multiconfigurational methods [CASPT2 and complete active space SCF (CAS-SCF)] predict that the isomerization of nitramide to NH(2)ONO occurs in a two-step mechanism: (i) NH(2)NO(2) --> NH(2) + NO(2) and (ii) NH(2) + NO(2) --> NH(2)ONO, the second step involving surmounting an activation barrier. Contrastingly, Hartree-Fock based approaches give isomerization as a one-step reaction. Additionally, both mono- and multiconfigurational methods predict that nitro-nitrite rearrangement of CH(3)NO(2) is a one-step process. The difference in the reaction mechanisms of these two isoelectronic molecules arises from the presence of an S(1)/S(0) conical intersection in nitramide which is absent in nitromethane.

The behaviour of the naphthoquinone derivatives 4-(4-dimethylamino-phenyl)-[1,2]naphthoquinone (L1) and 4-[4-(1,4,7,10,13-pentaoxa-16-aza-cyclooctadec-16-il)-phenyl]-[1,2]naphthoquinone (L2) as chromogenic chemosensors of metal cations and anions in acetonitrile has been studied. L1 and L2 are highly coloured receptors with a broad band centred at 534 (log e = 3.80) and 532 nm (log e = 3.86), respectively, and attributed to an intra-ligand charge transfer band involving the amine and the carbonyl groups. L1 shows a hypsochromic shift of the absorption band in the visible zone in presence of Cu2+, Fe3+ and Hg2+. Additionally, L2 suffers bleaching induced by the metal cations Pb2+ and Ba2+. In both cases, the data suggested metal cation coordination through the nitrogen atom of the aniline group. 1H NMR studies in the presence of certain metals are also in agreement with this interpretation. log K for the formation of the corresponding [M(L)]2+ complexes have been determined from nonlinear least-squares treatment of the titration profiles. Studies in the presence of anions were also carried out. In acetonitrile a chromogenic sensing of the anions HSO 4 - was observed using the metal complex Ba–L2.

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 dissociation reaction of nitrosomethane into methyl and nitric oxide and the tautomerization reactions to formaldehyde oxime, nitrone, and methoxy nitrene have been studied with the second-order multiconfigurational perturbation theory (CASPT2) by the computation of numerical energy gradients. The prevailing reactions in both the ground and the excited states are dissociations. The structures of the ground and excited states are compared with the corresponding complete active space SCF (CAS-SCF) geometries. It is found that changes in the individual bond lengths are rather large (0.01-0.02 A), while the character and energetics of the CASPT2 optimizations remain similar to the CAS-SCF values.

The complete active space self-consistent field (CAS-SCF) method combined with the multistate second-order perturbation theory (MS-CASPT2) are used to study the low-lying, singlet and triplet, potential energy surfaces of nitramide. Vertical transition calculations have allowed us to reinterpret the gas-phase UV spectrum of nitramide as the overlapping of two intense bands calculated at 6.46 and 6.52 eV, respectively. The states of relevance in its photochemistry after excitation at different wavelengths have been determined to be up to S4. From that point on, the most probable dissociation mechanism is determined by considering relative energies among the different stationary points and the major role played by conical intersections connecting S3/S2, S2/S1, and S1/S0 electronic states. The most likely dissociation products are NH2(1(2)B1), NO2(1(2)A1), NO2(1(2)A2), NO2(1(2)B2), NO2(1(2)A1)*, NH2NO(1(1)A''), NO(X(2)pi), and O(1D). With regards to the influence of triplet states in the photodecomposition of nitramide, our calculations indicate that T1/S0 crossing is probable only after radiationless deactivation.

N‐methyl,N‐(propyl‐3‐trimethoxysilyl) aniline was synthesized and used as an intermediate for anchoring dyes on inorganic siliceous supports through electrophilic aromatic substitution reactions.

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)

A set of sensors for water quality measurement has been developed. It consists of a multisensor designed to measure the following parameters: pH, temperature, dissolved oxygen, conductivity, redox potential and turbidity. The system has been built-up in thick-film technology, using when possible commercially available serigraphic pastes. The multisensor can be implemented in in situ portable or stationary instrumentation for water quality monitoring. The technology used in the multisensor implementation provides fundamental properties of miniaturization, reasonable precision and low cost. The complete system also includes electronic acquisition, signal conditioning and computing capabilities.

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

A new “electronic tongue” has been developed and used for the qualitative analysis of natural waters. Both wires and conducting surfaces in thick-film technology were used as potentiometric electrodes and the emf of each electrode in contact with a certain aqueous solution was used as input signal for a PCA analysis. An array containing the electrodes; RuO2 (with resistivities of 10 � /sq and 1 M� /sq), C, Ag, Ni, Cu, Au, Pt, Al, Sn, Pb and C (graphite) were used in a first approach. To test this “electronic tongue” design, a family of different natural waters were studied. These include seven mineral waters, tap water and osmotised water. Additionally, a qualitative analysis of the different waters was performed using fuzzy ARTMAP neural networks. The final system was successfully employed for the differentiation of the above mentioned waters with a success rate higher than 93%. © 2004 Elsevier B.V. All rights reserved.

A strategy for the rational design of a new optical sensor material for the selective recognition of long-chain carboxylates in water is presented. The approach relies on the combination of structure-property relationships to single out the optimal molecular sensor unit and the tuning of the sensing characteristics of an inorganic support material. A spacer-substituted 7-urea-phenoxazin-3-one was employed as the signaling moiety and a mesoporous trimethylsilylated UVM-7 (MCM-41 type) material served as the solid support. The sensor material shows the advantageous features of both modules that is absorption and emission in the visible spectral range, a fluorescence red-shift and enhancement upon analyte coordination, and the amplification of noncovalent (binding) and hydrogen-bonding (recognition) interactions in the detection event. Besides these basic results that are related to the design and performance of the sensor material, the paper discusses general aspects of amido-substituted phenoxazinone photophysics and addresses some general features of molecular anion recognition chemistry in aqueous vs nonaqueous media, utilizing steady-state and time-resolved optical as well as NMR spectroscopies. Detailed studies on potentially competing biochemical species and a first access to the schematic model of the response of the sensor material as obtained by a combination of fluorescence lifetime distribution analysis and Langmuir-type fitting of the gross binding constants complement the key issues of the paper.

The new cyclic aza-oxa-cycloalkane 7,13-bis(n-octyl)-1,4,10-trioxa-7,13 diazacyclopentadecane (L1) has been synthesised, characterized and its interaction with anionic surfactants studied. Protonation constants of L1 and stability constants of L1 with lauryl sulfate, sulfate and phosphate were determined by potentiometric titration in 1,4-dioxane:water (70:30, v/v, 0.1 mol dm−3 KNO3, 25 °C). L1 forms stable complexes with lauryl sulfate in a wide pH range. Different PVC-membrane anionic surfactant-selective electrodes were prepared using L1 as ionophore and o-nitrophenyl octyl ether (NPOE), bis(2-ethylhexyl) sebacate (BEHS) or dibutyl phthalate (DBP) as plasticizers. The PVC-based membrane electrode containing L1 as carrier and NPOE as plasticizer (electrode E1) showed a Nernstian response with a slope of 57.7 ± 0.2 mV per decade over a range of lauryl sulfate concentration from 3.3 × 10−6 to 6.7 × 10−3 M with a detection limit of 2.2 × 10−6 M. For the sake of comparison, a PVC-based membrane electrode containing L1, NPOE and tetra-n-octylammonium bromide as cationic additive (electrode E2) was also prepared and studied. Selectivity coefficients for different anions with respect to lauryl sulfate were calculated. Electrode E1 showed remarkably better selectivity coefficients than electrode E2, probably due to favourable interaction of lauryl sulfate with L1. Electrode E1 was used for the determination of anionic surfactants in several mixtures, and the results obtained were compared to those found using a commercially available electrode.

The doublet potential energy surfaces involved in the decomposition of the nitromethane radical anion (CH(3)NO(2) (-)) have been studied by using the multistate extension of the multiconfigurational second-order perturbation method (MS-CASPT2) in conjunction with large atomic natural orbital-type basis sets. A very low energy barrier is found for the decomposition reaction: CH(3)NO(2) (-)--[CH(3)NO(2)](-)--CH(3)+NO(2) (-). No evidence has been obtained on the existence of an isomerization channel leading to the initial formation of the methylnitrite anion (CH(3)ONO(-)) which, in a subsequent reaction, would yield nitric oxide (NO). In contrast, it is suggested that NO is formed through the bimolecular reaction: CH(3)+NO(2) (-)--[CH(3)O-N-O](-)--CH(3)O(-)+NO. In particular, the CASSCF/MS-CASPT2 results indicate that the methylnitrite radical anion CH(3)ONO(-) does not represent a minimum energy structure, as concluded by using density functional theory (DFT) methodologies. The inverse symmetry breaking effect present in DFT is demonstrated to be responsible for such erroneous prediction.

The aniline–neon van der Waals complex has been investigated from a theoretical point of view. The intermolecular distance, structure and rotational constants in the ground electronic state have been obtained by ab initio calculations using second-order Moller–Plesset (MP2) theory. The potential energy surface has also been determined. It has been found that two conformers exist: the anti, where the neon atom and the NH bonds are located on opposite sides of the ring, is slightly more stable than the syn conformer. All the ab initio results agree with those obtained by the analysis of the rotational and laser induced fluorescence spectra of this complex. We have also modeled the interaction of the van der Waals bending mode with others internal motions of the aniline molecule such as the inversion mode of the amino group and the breathing mode of the ring. The theoretical results predict that there is a significant coupling between the van der Waals bending and the inversion mode in agreement with the experimental behavior found in both the ground and the first excited electronic states of this complex. 2004 Elsevier B.V. All rights reserved.

The polyazacycloalkanes, 1,4,8,11-tetra(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L1), 1,4,7,10,13-penta(n-octyl)-1,4,7,10,13-pentaazacyclopentadecane (L2) and 1,4,7,10,13,16-hexa(n-octyl)-1,4,7,10,13,16-hexaazacyclooctadecane (L3) have been synthesised, characterised and the ability of these polyamines as anion receptors has been studied using them as ionophores in PVC membrane anion-selective electrodes. The PVC membranes containing L1, L2 and L3 gave a linear response in the presence of perchlorate. The EMF response characteristics of these membrane-based perchlorate-selective electrodes and the selectivity coefficients using DOS, DBP or NPOE as plasticisers have been determined. The perchlorate-selective electrodes gave anion-selectivity patterns that basically follow the Hofmeister Series, expect the ISE containing L1 and DOS as plasticiser.

This thematic set of papers is derived from a workshop, dedicated to the Messinian sequence, which was convened during the 77th EAGE Conference and Exhibition in Madrid in 2015. The main goal of the workshop was to introduce a geological exploration topic to the EAGE meeting. With this objective, and in collaboration with Hector Gonzalez of REPSOL and Jean-Loup Rubino of TOTAL, we co-ordinated a dedicated meeting to bring together people studying the Mediterranean region, particularly those dealing with the Messinian sequence, from both academic and exploration viewpoints.

A general model concerning the role of the electrode potential on the charge-transfer enhancement mechanism of SERS is proposed, justifying the existence of a parameter ‚ which reduces the effectiveness of the electrode potential in order to shift the excited charge-transfer level. This explains the observed deviation of ‚ from the unity, and allows for relating the intensity/electrode-potential (SERS -CT) profiles of similar adsorbates with the respective electron affinities. The SERS of pyridine, pyrazine and methylpyrazines have been recorded on silver, being found that the electrode potential in the maximum of the SERS-CT profiles shifts toward more negative values as the number of methylsubstituents attached to the pyrazine ring increases. This result has been explained on the basis of the relative stability of the radical anions given that a correlation between those shifts and the calculated ab initio vertical transition energies between the neutral molecules and their respective radical anions can be established. This confirms the participation of a resonant charge-transfer mechanism in the SERS as well as the usefulness of this technique to gain insight into the electronic properties of the doublet states of the here studied molecules.

Macrolactone 1 has shown different fluorescent responsedepending on the ionic or covalent character of mercury compounds. This ligand also presents a very selective response to Hg(ClO4)2 versus Cd(ClO4)2.

The surface-enhanced Raman scattering (SERS) spectra of 4-methylpyridine (4-MP) have been recorded at different electrode potential versus saturated Ag/AgCl/KCl reference electrode. By comparing the relative intensity of the SERS with the Raman spectrum of the aqueous solution it is possible to determine that 12, 6a, δ(CH) and especially 8a modes are strongly enhanced. In this work, it is demonstrated that these vibrations are closely related to Franck–Condon factors of a resonant photoinduced charge transfer (CT) mechanism similar to a resonance Raman (RR) process. The theoretically calculated ΔQ displacements represent the differences between geometries of the potential energy minima of the states involved in the resonant process, allowing to calculate the relative intensities in RR from the Peticolas’ equation. These calculated intensities are in a perfect agreement with the experimental behavior.

The surface-enhanced Raman scattering spectra of 2,6-dimethylpyridine have been recorded on silver at different electrode potentials. The main feature of these spectra is the strong enhancement of the band corresponding to the 8a mode when the electrode potential becomes more negative. This enhancement has been discussed on the basis of a resonant charge transfer (CT) mechanism by using a methodology based on the analysis of the ab initio optimized equilibrium structures of the electronic states involved in the CT resonant process namely: the ground electronic states of the neutral molecule and its radical anion.

The new open-chain polyazaalkanes ligands L 1 , L 2 , L 3 and L 4 functionalised with one or two pyrene groups were synthesised and characterised and their potential use as selective cation and anion sensing chemosensors studied. Solution studies by potentiometric methods were carried out in the presence of the metal cations Cu 2+ and Zn 2+ in acetonitrile–water (70:30 v/v, 0.1 mol dm −3 tetrabutylammonium perchlorate, 25 °C) The results are compared with those reported for the analogous non-functionalised ligand triethylentetraamine ( tta ). The fluorescence behaviour of the ligands L 1 –L 4 has been studied as a function of the pH in the presence of the metal cations Ni 2+ , Cu 2+ , Zn 2+ , Cd 2+ , Hg 2+ and Pb 2+ in acetonitrile–water 70:30 v/v mixtures. The Zn 2+ and Cd 2+ cations enhance the fluorescence emission of the L 1 –L 4 chemosensors at basic pH, whereas Cu 2+ induce quenching of the fluorescence emission at acid pH. The fluorescence behaviour of L 1 –L 4 receptors was also studied as a function of the pH in acetonitrile–water 70:30 v/v in the presence of anions.

The ligand 1,4,8-tri(n-octyl)-1,4,8,11-tetraazacyclotetradecane (L1) containing pendant octyl groups has been synthesised. L1 is a tetraazamacrocycle derived from the well-known cyclam unit, and the Ni2+ and Co2+ complexes, [Ni(L1)]2+ and [Co(L1)]2+, have been isolated and characterised. The ability of the nickel(II) and cobalt(II) complexes to act as anion receptors has been studied by using them as ionophores in membrane-based ion-selective electrodes (ISEs). The PVC membrane containing the complex [Ni(L1)]2+ and 2-nitrophenyloctylether as plasticizer shows a Nernstian response against iodide in a concentration range from 1×10−1 to 4×10−5 M I− with a detection limit of 1.6×10−5 M I− and a slope of 58.6 mV/pI− at pH 7 (25 °C). In comparison, the electrode containing [Co(L1)]2+ as ionophore gave a sub-Nernstian slope and a low lifetime. A comparison between the iodide-selective electrode containing [Ni(L1)]2+ and other reported iodide-selective electrodes is also reported.