Novel U-Shaped D-A-D π-conjugated Systems with Mechanochromic Properties: An Experimental and Theoretical Vibrational Spectroscopic Investigation

Π-conjugated compounds have been widely studied in the last few decades due to their huge field of application in organic electronics. Specifically, stimuli-responsive Π-conjugated materials which are sensitive to external stimulus (i.e., temperature, pressure, etc) have several uses like sensors, probes and security inks, for example.1 In this work, we study two U-shape Donor-Acceptor-Donor (D-A-D) systems that are found to exhibit interesting thermal- and pressure-dependent properties. 2 They consist on two different conformers of phenothiazine-dibenzo[a,j]phenazine-phenothiazine which differs from the position of the phenothiazine respect to the dibenzophenzaine central core. Compound 1R is the equatorial-equatorial conformer and 1Y is the axial-axial conformer (Figure 1). The dibenzophenzaine group acts as an electron-acceptor whereas the phenothiazine unit acts as an electron-donor. It has been reported that this U-shape D-A-D compound shows a multi-active color changing in 3 steps and their luminescence changes with temperature, pressure and acid exposition.2 In this work, we aim to elucidate how the external stimuli (i.e. temperature, pressure, acid ambient) affects the molecular structure at both intra- and intermolecular level. To this end, we use UV-Vis absorption, Raman (Figure 1) and Infrared spectroscopy experiments in combination with DFT calculations.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Bioevents correlation of planktic foraminifers and radiolarians from the Cenomanian to Turonian, southeastern Mexico

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Impact of the dicyanomethylene substitution position on the cyclophane macrocycle formation in carbazole-based biradicals

π-Conjugated biradical compounds, featuring unique unsaturated valences and radical centers in the ground state, are fundamentally important for understanding the nature of chemical bonds and have potential applications in material science. [1] Recently, it has been demonstrated that several -conjugated mono- and biradicals systems form long strain -bonds between two unpaired electrons resulting in macrocyclic or staircase oligomers or polymers by self-assembly processes. [2] Therefore, these materials are potential building blocks for dynamic covalent chemistry (DCC) since the aggregates can be formed or broken upon soft external stimuli. For instance, 2,7-dicyanomethylene-9-(2-ethylhexyl)carbazole biradical (p-Cz-alkyl in Figure 1) reversibly converts upon soft stimuli (temperature, pressure, light) to a cyclophane tetramer as a result from the formation (or bond cleavage) of long C-C single bonds.[3] Here, we present an experimental and theoretical study in order to investigate how the N-substitution and the change from para- to meta-dicyanomethylene substitution on carbazole-based biradicals affects their biradical character and thus, their tendency to act as useful motifs for DCC (see Figure 1).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Improved prediction of the optical properties in pi-conjugated polymers: the case of benzochalcogenodiazole-based copolymers with different heteroatom substitution

Donor−acceptor (D−A) approach to conjugated polymer design has become a widely used method for preparing conjugated polymers with narrow band gaps.1 One outstanding D−A polymer is poly(cyclopentadithiophene)benzothiadiazole, PCPDTBT (P1 in Figure 1), for which power conversion efficiencies in solar cells of 4.5-5.5% are reported.2 In this work, we use resonance Raman (RR) and density functional theory (DFT) calculations to investigate the tuning of the electronic and structural properties of cyclopentadithiophene-benzochalcogenodiazole D−A polymers, wherein a single atom in the benzochalcogenodiazole unit is varied from sulfur to selenium to tellurium (Fig. 1).3 Sophisticated DFT calculations have been carried out using long-range corrected functionals, considering both tuned and default range-separation parameters, aiming at predicting their optical and charge transport properties. In addition, the nature of the electronic excitation is described by analyzing the enhancement pattern in the RR spectra using Raman excitation wavelengths coincident with the various transitions in the copolymers.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Investigating Piezochromic Properties of πconjugated Materials: a combined Raman and DFT Study

Π-conjugated materials have been studied for decades due to their great interest in organic electronics. Among them, piezochromic materials, which exhibit color changes resulting from external pressure or mechanical grinding, become very attractive from a scientific viewpoint owing to their potential applications as pressure-sensing and opticalrecording systems1. The main target of the present work is to develop a joint experimental and theoretical approach able to deliver crucial information for the understanding of the structural effects causing piezochromic changes. To this end, we will focus our attention on two families of -conjugated materials with potential application as sensors. The first one is a family of 9,10-Bis((E)-n(pyrid-2-yl)vinyl) anthracene, BPnVA (n=2 orto-,3 metha- and 4 para-) compounds, see Figure 1. Interestingly, these three compounds with varying position of the nitrogen on the external pyridyl group exhibit different molecular packing modes. Grinding and the application of external pressure on the powder also led to a strong change in their photoluminescence color.2 The second familiy is based on the N,N’-Bis-Boc-3,3’-di(pyren-1yl)-2,2’-biindole compound (compound 1c in Figure 1) which also shows photoluminescence under pressure application. However, the molecular packing induced by this phenomenon is still under study 3. In both cases, it will be also very interesting to determine how temperature affects the vibrational structure of these systems.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Modelling the optical properties of Benzochalcogenodiazole-based Copolymers using Tuned Range-Separated Hybrid Functionals

Since the discovery of organic semiconductors, these systems have been deeply investigated and many strategies to module their optical and electronic properties have been established. In this sense, Donor-acceptor (D−A) approach to conjugated polymer design has become a widely used method for preparing conjugated polymers with narrow band gaps. This approach involves synthesizing a polymer with a delocalized π-electron system that comprises alternating electron-rich (donor) and electron-deficient (acceptor) repeat units. The combination of high-lying HOMO levels (residing on the donor units) and low-lying LUMO levels (residing on the acceptor units) results in an overall narrow band gap for the polymer. In this sense, poly(cyclopentadithiophene)benzothiadiazole is a D−A polymer for which power conversion efficiencies in solar cells of 5 6 % are reported. In this work, we use density functional theory (DFT) calculations to investigate the tuning of the electronic and structural properties of cyclopentadithiophene ben zochalcogenodiazole D−A polymers, wherein a single atom in the benzochalcogenodiazole unit is varied from sulfur to selenium to tellurium. Resonance Raman (RR) spectroscopy is also used to describe the nature of the electronic excitations. Improved prediction of the optical properties h as been obtained by using long range corrected functionals functionals, considering both tuned and default range separation parameters, aiming at predicting their optical and charge transport properties.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

LA CUEVA "CV-3" DE COGOLLOS-VEGA (GRANADA). II. NUEVOS MATERIALES

A typological analysis was carried out on ceramic materials from cave CV-3 in Cogollos Vega. These materials were discovered after the publication of the first study made on a larger, more varied selection of material from the same site. Our analysis confirms that these new materials are typical of the first stage of the Cultura de las Cuevas, to which this recent record adds a new site of undoubted importance on one of the mountainous borders of the Granada Basin.Se realiza el análisis tipológico de materiales cerámicos procedentes de la Cueva "CV-3" de Cogollos Vega, conocidos con posterioridad a la publicación del primer estudio llevado a cabo sobre un más amplio y variado conjunto material del yacimiento. Dicho análisis viene a corroborar su adscripción a un contexto típico de la primera etapa de desarrollo de la Cultura de las Cuevas que cuenta, tras este registro, con un nuevo enclave de indudable importancia en uno de los rebordes montañosos de la Vega de Granada

LA CUEVA DE LOS MOLINOS (ALHAMA, GRANADA)

Al tratar de cuestiones relacionadas con la evolución del Neolítico en la Alta Andalucía, hemos venido haciendo en publicaciones anteriores continuas alusiones y referencias a la Cueva de los Molinos de Alhama. Dichas alusiones son las que justifican principalmente nuestro interés en la presentación de un conjunto de materiales arqueológicos, parte de los cuales conocíamos desde hace años, procedentes todos ellos de prospecciones superficiales y carentes, consecuentemente, de cualquier indicación estratigráfica.El material que aquí se recoge es sólo una pequeña muestra del que tenemos constancia que fue localizado en las varias visitas y prospecciones realizadas, habiendo sido imposible dar con el paradero de otra parte importante dada la gran dispersión del mismo, derivada a su vez de la larga historia en la documentación del yacimiento a la que ahora haremos referencia. Procede en concreto de pequeños fondos conservados por don Miguel Guirao Pérez y don Cayetano Aníbal González, quienes nos los cedieron amablemente para su estudio, así como de otros existentes en el Departamento de Prehistoria de la Universidad de Granada producto de una prospección hecha por algunos miembros del mismo y de una donación de don Manuel García Sánchez. Una pequeña parte pertenece a una colección particular del pueblo de Alhama a la que tuvimos acceso. Otros materiales cerámicos, líticos y óseos que aquí no se recogen se encuentran en el Museo Arqueológico Provincial de Granada en el que fueron depositados por don Miguel Botella López, habiéndose ya dado aconocer algunos de ellos

Reproducibility and validity of a food frequency questionnaire among pregnant women in a Mediterranean area

Background: Studies exploring the role of diet during pregnancy are still scarce, in part due to the complexity of measuring diet and to the lack of valid instruments. The aim of this study was to examine the reproducibility and validity (against biochemical biomarkers) of a semi-quantitative food frequency questionnaire (FFQ) in pregnant women. Methods: Participants were 740 pregnant women from a population-based birth cohort study in Valencia (INMA Study). We compared nutrient and food intakes from FFQs estimated for two periods of pregnancy (reproducibility), and compared energy-adjusted intake of several carotenoids, folate, vitamin B12, vitamin C and α-tocopherol of the FFQ in the first trimester with their concentration in blood specimens (validity). Results: Significant correlations for reproducibility were found for major food groups and nutrients but not for lycopene (r=0.06); the average correlation coefficients for daily intake were 0.51 for food groups and 0.61 for nutrients. For validity, statistically significant correlations were observed for vitamin C (0.18), α-carotene (0.32), β-carotene (0.22), lutein-zeaxantin (0.29) and β-cryptoxantin(0.26); non-significant correlations were observed for retinol, lycopene, α-tocopherol, vitamin B12 and folate (r≤0.12). When dietary supplement use was considered, correlations were substantially improved for folate (0.53) and to a lesser extent for vitamin B12 (0.12) and vitamin C (0.20). Conclusion: This study supports that the FFQ has a good reproducibility for nutrient and food intake, and can provide a valid estimate of several important nutrients during pregnanc

Rheological Behaviour of an Insoluble Lemon Fibre as Affected by Stirring, Temperature, Time and Storage

The final publication is available at link.springer.comIn this work, the effect the preparation method (two different stirring systems at two temperatures and times), fibre concentration (between 2% and 3%), temperature (between 10 °C and 50 °C) and storage time (between 24 h and 50 days at 5 °C) had on the flow properties of a suspension of dietary lemon fibre prepared with a 45° Brix sucrose solution were evaluated. This information will be helpful in order to discover the best possibilities of using fibre to increase the viscosity of certain kinds of products, depending on the processing, storage and consumption conditions. The obtained results indicate that all the aspects which contribute to increase component solubilisation and the interaction of the insoluble fraction with the aqueous phase when preparing the suspension, such as a decrease in particle size, a rise in temperature or a longer homogenization time, entail a higher apparent viscosity. Moreover, favoring the solubilisation in the preparation process leads to a more stable rheological behaviour of the suspension during storage. As expected, the apparent viscosity of suspensions was dependent on the shear rate, concentration and temperature. A thixotropic behaviour of fibre suspension was only observed at a very low shear rate (5 s -1). © 2010 Springer Science + Business Media, LLC.Córdoba Sequeira, A.; Camacho Vidal, MM.; Martínez Navarrete, N. (2012). Rheological Behaviour of an Insoluble Lemon Fibre as Affected by Stirring, Temperature, Time and Storage. Food and Bioprocess Technology. 5(3):1083-1092. doi:10.1007/s11947-010-0478-2S1083109253Akdogan, H., & McHugh, T.-H. (2000). Flow characterization of peach products during extrusion. Food Engineering and Physical Properties, 65(3), 471–475.Alonso, M.-L., Larrodé, O., & Zapico, J. (1995). Rheological behaviour of infant foods. Journal of Texture Studies, 26, 193–202.Duran, L., & Costell, E. (1982). Rheology of apricot puree: Characterization of flow. Journal of Texture Studies, 13, 43–58.Flint O (1996) Microscopía de los alimentos. Manual de métodos prácticos utilizando la miscroscopía óptica. Ed. Acribia S-A, Zaragoza, 28, 108–111Grigelmo-Miguel, N., Gorinstein, S., & Martín-Belloso, O. (1999a). Characterisation of peach dietary fiber concentrate as food ingredient. Food Chemistry, 65, 175–181.Grigelmo-Miguel, N., Ibarz-Ribas, A., & Martín-Belloso, O. (1999b). Rheology of peach dietary fibre suspensions. Journal of Food Engineering, 39, 91–99.Guerrero S-N & Alzamora S-M. (1998). Effect of pH, temperature and glucose addition on flow behaviour of fruit purées: II. Peach, papaya and mango purées. Journal of Food Engineering, 37, 77–101.Guillon, F., & Champ, M. (2000). Structural and physical properties of dietary fibres, and consequences of processing on human physiology. Food Research International, 33, 233–245.Hahn, S.-J., Ree, T., & Eyring, G.-H. (1959). Flow mechanism of thixotropic substances. Industrial and Engineering Chemistry Research, 51, 856–857.Jongaroontaprangsee, S., Tritrong, W., & Chokanaporn, W. (2007). Effects of drying temperature and particle size on hydration properties of dietary fiber powder from lime and cabbage by-products. International Journal of Food Properties, 10, 887–897.Lario, Y., Sendra, E., Garcıa-Perez, J., Fuentes, C., Sayas-Barbera, E., Fernández-López, J., et al. (2004). Preparation of high dietary fiber powder from lemon juice by-products. Innovation of Food Science Emerging Technologies, 5, 113–117.Mahmoud M-I & Fugitt M (1996) Rheological properties of a calorically dense nutritional supplement as a function of nitrogen source and dietary fiber. In: IFT Annual Meeting. Book of Abstracts. 80A-26, 183Mizrahi, S. (1979). A review of the physicochemical approach to the analysis of the structural viscosity of fluid fruit products. Journal of Texture Studies, 10, 67–82.Paredes, M.-D.-C., Rao, M.-A., & Bourne, M.-C. (1998). Rheological characterization of salad dressings: 1. Steady shear, thixotropy and effect of temperature. Journal of Texture Studies, 19, 247–258.Raghavendra, S.-N., Ramachandra Swamy, S.-R., Rastogi, N.-K., Raghavarao, K.-S.-M.-S., Kumar, S., & Tharanathan, R.-N. (2006). Grinding characteristics and hydration properties of coconut residue: A source of dietary fiber. Journal of Food Engineering, 72, 281–286.Sakata, T., & Saito, M. (2007). Insoluble dietary fiber of wheat bran increased viscosity of pig whole cecal contents in vitro. Journal of Nutrition Science and Vitaminology, 53(4), 380–381.Saldaña, S., Martínez-Navarrete, N., & Chiralt, A. (2000). Caracterización Reológica de Alimentos de alta viscosidad. In P. Fito, A. Chiralt, A. Andrés, & N. Martínez-Navarrete (Eds.), Series de Ciencia e Ingeniería de Alimentos. Investigación del postgrado del IAD-DTA. Vol I (p. 383). Valencia: Editorial de la Universidad Politécnica de Valencia.Sangnark, A., & Noomhorm, A. (2003). Effect of particle sizes on functional properties of dietary fibre prepared from sugarcane bagasse. Food Chemistry, 80(2), 221–229