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A synthesis of donor-acceptor-substituted oligothiophenes by Stille coupling is described. The 5´-estanyl derivatives, readily prepared from 5-alkoxy- and 5-amino-2,2´-bithiophenes 7 were coupled with the appropriate aryl or heteroaryl bromides to give the title compounds., Fundação para a Ciência e Tecnologia. FEDER - POCTI/QUI/37816/2001.

A synthesis of 1-amino substituted 4-(2´-thienyl)-phthalazines is described from halo- derivatives of 4-(2´-thienyl)-1-(2H)-phthalazinone 3., Fundação para a Ciência e Tecnologia. FEDER - POCTI (ref. POCTI/QUI/37816/2001).

This work reports on cyclic voltammetry and spectroscopic UV-Vis investigations of some pyridazine derivatives 1-8 in dimethylformamide. In the electrochemical study, monochlorinated pyridazines 2-8 exhibit two reductions but in the case of dichlorinated derivative 1 an additional wave is seen for the reduction of the second carbon-chloride bond. The electronic absorption spectra display an intramolecular charge transfer band π-π* in the UV region of which depend substantially on the nature of both donor and acceptor moieties. These results indicate the π-electron delocalization in the conjugated system.

New molecular systems based on donor/acceptor groups connected by π-conjugated bridge, trans-[MoF(NNC7H6SO2)(Ph2PCH2CH2PPh2)2][BF4], have been synthesized. This complex with nonlinear optical (NLO) applications was immobilized by an adsorption process from liquid phase, in the interlayer of a pillared clay (PILC). The metal complex and the new materials were characterized by thermal analysis (DSC), chemical analysis, surface techniques (XPS), X-ray powder diffraction (XRD), nitrogen adsorption isotherms, spectroscopic methods (NMR, FT-IR and UV/Vis) and electrochemical measurements. The studies of the electrochemical and the spectroscopic properties of the complex show interactions between donor and acceptor groups across the conjugated bridge. The results obtained from the studies using different techniques of analysis confirm that the molybdenum complex was effectively immobilized in the host matrix and this process does not modify the morphology or structure of the PILC upon metal complex loading., Dr. Carmen Serra Rodrigues (C.A.C.T.I., Vigo University, Spain) is gratefully acknowledged for performing and analyzing the XPS measurements. We thank António Souza Azevedo for collecting the powder diffraction data. This work was supported by the Fundação para a Ciência e a Tecnologia (FCT, Portugal) through project POCTI/42931/QUI/2001., info:eu-repo/semantics/publishedVersion

Seven new donor/acceptor oligothiophenes 1-2 were synthesized by Stille coupling in moderate to good yields. Compounds 1-2 were completely characterized by the usual spectroscopic methods. In agreement with the electrochemical and the spectroscopic studies for this compounds the new derivatives prepared, can find application for manufacturing new materials with strong non-linear optical (NLO) properties., Fundação para a Ciência e a Tecnologia (FCT)

It is shown that the adsorption and morphological properties of layer-by-layer films of poly(o-methoxyaniline) (POMA) alternated with poly(vinyl sulfonic acid) (PVS) are affected dramatically by different treatments of the POMA solutions employed to prepare the films. Whereas the dimension of the globular structures seen by atomic force microscopy increases nonmonotonically during film growth in parent POMA solution, owing to a competition of adsorption/desorption processes, it changes monotonically for the fractionated POMA. The roughness of the latter films depends on the concentration of the solution and saturates at a given size of the scan window. This allowed us to apply scaling laws that indicated a self-affine mechanism for adsorption of the treated POMA.

Atomic force microscopy (AFM) was employed to monitor the buildup of layer-by-layer films of poly(o-methoxyaniline) (POMA) and poly(ethenesulfonic acid) (PVS) onto several substrates. Using the contact mode of an AFM, we produced a furrow on the film, which was made possible because the film material was less stiff than the substrate and the silicon tip. Film thickness could then be measured using the tapping mode. The thickness and adsorbed amount of POMA/PVS increased linearly after several bilayers had been deposited, while the roughness increased with the number of bilayers until reaching a saturation value. This behavior was attributed to the ability of these polymers to aggregate, which was confirmed by an analysis of grain sizes.

The syntheses of four novel psoralen derivatives, 6a-d, of the benzofurocoumarin (=benzofuro[1]benzopyranone) type containing an ester group are described. These compounds might be of interest in PUVA (psoralen long-wave ultraviolet radiation) therapy. The overall efficiency of the synthetic procedure is greatly limited by the low yields for the penultimate step, i.e. formylation of the dibenzofuranols 3a,c or protected dibenzofuranol 4d to the carboxaldehydes 5 (Scheme 4). However, the final stage to form the pyranone ring from 5a-d proceeds smoothly (Scheme 5)., Fundação para a Ciência e Tecnologia - PRAXIS XXI/BD/19707/99. Fundação de Amparo à Pesquisa do Estado de Minas Gerais (Brasil). Conselho Nacional do Desenvolvimento Científico e Tecnológico (Brasil).

Studies of constant current corona, negatively charged Teflon FEP samples, show a surface potential build up depending on the humidity content. In dry air atmospheres it is possible to charge a sample to very high charge densities. In humid atmospheres the surface potential saturates at lower potentials. Charge centroid position measurements show that in samples charged under humid conditions the centroid position is deeper than in the case of dry conditions. On the other hand, surface charge decays much faster in humid atmospheres than in dry air. These results are explained in terms of a protonic model for charge transport, in Teflon FEP under humid conditions, in which the negative surface charges induce a drift of ions from the bulk to the surface charge layer.

It was shown previously that negative corona treatment of Teflon FEP decreases the thermal stability of the electrets. Thermally stimulated discharge measurements of treated samples presented, besides the usual peak of 210 degrees C, a new broad current peak in the temperature range of 100 to 160 degrees C. Further investigations were carried out on N/sub 2/, CO/sub 2/, O/sub 2/, and dry air in order to study the effect of the corona atmosphere on the corona treatment. In N/sub 2/ no effect was observed, while for CO/sub 2/ and O/sub 2/ a well-defined current peak appears with a maximum at 120 degrees C. In dry air no significant differences were observed when compared with the results for normal air. >

The corona triode making it possible to charge polymeric foils with a constant current has proved to be a powerful method for studying charge storage and transport. For ferroelectric polymers it allows one to determine the coercive field and the remanent polarization. A special version of such a triode was developed for poling samples in a controlled atmosphere. The results show that for beta -PVDF (polyvinylidenefluoride) samples the surface potential build-up is dependent on the air humidity. For a dry air atmosphere, the polarization clearly shows the ferroelectric behavior of the PVDF sample. A tentative explanation for the saturation of the potential build-up dependence on the humidity takes into account the increase in conductivity due to the water in the bulk of the polymer. >

International audience; The aim of the present work is to show a simple method that combines conventional laser interferometry and standard thin film deposition techniques to fabricate modulated magnetic nanostructures with lateral periodicity, and to tailor the magnetic properties by varying geometrical parameters. Well defined Ni80Fe20 magnetic thin films with sinusoidal grating profiles were obtained with a periodicity of 1.2 μm and different grating depths. Magnetic studies via ferromagnetic resonance and magneto optical Kerr effect demonstrate the tunability of the induced in-plane magnetic anisotropy with depth profile.

This chapter deals with the Langmuir–Blodgett and self-assembled polymeric films. The growing interest in organic materials requires research that can be broadly divided into four main categories—namely, (1) material design, (2) synthesis, (3) processing and characterization, and (4) testing for applications. Having the designed material synthesized, in most cases an important step prior to testing a proposed application is the processing of the materials into a desired form, preferably in the form of ultrathin films that often possess a large surface area. For organic materials, in particular, the most commonly used techniques are simple drop casting, spin casting, dip coating, Langmuir–Blodgett technique, and self-assembly. A common feature in all these techniques is that the material of interest is first dissolved in a suitable solvent, being subsequently either physisorbed or chemisorbed onto a surface. The Langmuir–Blodgett and the self-assembly methods are looked upon as viable means of producing ultrathin films with controllable film thickness and molecular packing. While the former technique involves the formation of a monolayer film at the air-water interface and subsequent transfer as a multilayer film onto a solid substrate, the latter technique is essentially based on the ionic interaction between alternate layers.

Gama-Keto esters (2) derivatives of thiophene were obtained from hemi-succinic esters and transformed to the corresponding amides (4). Lawesson´s treatment of 2 and 4 gave the corresponding bithiophenes (5) with alkoxy or amino substituents., Thanks are due to FCT through IBQF (UM), ICCTI/French Embassy (Technical and Scientific Cooperation Programme) and to Dra. A.M.F. Oliveira-Campos for the interesting discussions.

We report the synthesis and characterisation of multisubstituted diphenylacetamides, diphenylsulfonamides and diphenylamines (and some observations on cyclisation of the last).

We report the complete characterisation of all the precursors of 6-bromo-5,8-dimethylisoquinoline via Miller and Moock´s synthesis, and the synthesis of 6-bromo-4,7-dimethyl-2-(5´-Bromo-4´,7´-dimethyl)-2´,3´-dihydro-1´-H-inden-1´-yl)-1-H-indene., We thank FCT, ICCTI and CRUP (Portugal) and the British Coucil for financial support.

Although simple diphenylamines are conveniently oxidised with Palladium (II) acetate to give carbazoles, for more complex examples, carbazoles are minor products amongst many., CRUP (Portugal). British Council - Treaty of Windsor Programme. Junta Nacional de Investigação Científica e Tecnológica.

Morphology of poly(allylamine hydrochloride) and poly[1-[4-(3-carboxy-4-hydroxyphenylazo) benzenesulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) layer-by-layer (LBL) films is shown to influence the orientation of PAZO chromophores with respect to solid support surface, which in turn is related with observed red-shifts changes of the chromophore absorbance peak position relative to that of solution spectrum, as the bilayers are being deposited. For the first bilayers, an increase of red shift values is observed, while roughness and grain radius are kept practically constant; after the 5th bilayer, the red-shift values decrease, while grain sizes increase and the number of grains decreases. This behavior is consistent with adsorption of coiled PAZO molecules, treated as pseudo-particles, with the chromophores head-to-head oriented-J aggregates. These aggregates adsorb perpendicularly to the substrate surface for the first layers and, as roughness and grain radius increase, the adsorption of the J aggregates takes place parallel to the solid support surface, which gives rise to a decrease in the red shift value. Moreover, the adsorption of these pseudo-particles follows a fractal growth characterized by a scaling exponent of α = 0.80 ± 0.02 and a temporal growth exponent of β = 0.17 ± 0.02. These values suggest a layer growth according with Villain model, which accounts for the interactions between deposited particles and the surface. This is in accordance with the electrostatic forces driving LbL film formation and accounts for the observed morphology behavior for the different number of layers.

In this paper, we demonstrate that the intrinsic electric field created by a poly(o-methoxyaniline) (POMA) cushion layer hinders the changes in molecular conformation of poly(p-phenylenevinylene) (PPV) in layer-by-layer with dodecylbenzene sulfonic acid (DBS). This was modeled with density functional theory (DFT) calculations where an energy barrier hampered molecular movements of PPV segments when they were subjected to an electric field comparable to that caused by a charged POMA layer. With restricted changes in molecular conformation, the PPV film exhibited Franck-Condon transitions and the photoexcitation spectra resembled the absorption spectra, in contrast to PPV/DBS films deposited directly on glass, with no POMA cushion. Other effects from the POMA cushion were the reduced number of structural defects, confirmed with Raman spectroscopy, and an enhanced PPV emission at high temperatures (300 K) in comparison with the films on bare glass. The positive effects from the POMA cushion may be exploited for enhanced opto-electronic devices, especially as the intrinsic electric field may assist in separating photoexcited electron-hole pairs in photovoltaic devices.

8,10-Dimethoxyellipticine has been synthesised from readily available benzene derivatives via palladium acetate or photochemical cyclisation of intermediate diphenylamine derivatives. The route has advantages over indole based syntheses., We thank the British Council for awards under the Treaty of Windsor Programme and JNICT (IBQF - UM) Portugal for financial support., info:eu-repo/semantics/publishedVersion

Analysis of AC electrical conductivity of deoxyribonucleic acid (DNA) thin films, irradiated with ultraviolet (UV) light, revealed that electrical conduction arises from DNA chain electron hopping between base-pairs and phosphate groups. The hopping distance calculated from correlated barrier hopping model equals the distance between DNA base-pairs, which is consistent with the loss of conductivity with irradiation time arising from a decrease in phosphates groups. In the high frequency regime, at a given frequency, real part of conductivity strongly depends on irradiation time particularly for low dose levels suggesting the use of DNA based films for UV radiation sensors.

Refers to: M. Manuela M. Raposo, Ana M.F.P. Ferreira, Mariana Amaro, M. Belsley, João C.V.P. Moura The synthesis and characterization of heterocyclic azo dyes derived from 5-N,N-dialkylamino-2,2′-bithiophene couplers Dyes and Pigments, Volume 83, Issue 1, October 2009, Pages 59-65. doi: 10.1016/j.dyepig.2009.03.012, The correct title of the article is “Synthesis and characterization of the thermal and the solvatochromic properties of heterocyclic azo dyes derived from 5-N,N-dialkylamino-2,2′-bithiophene couplers”. The correct author's name of the third author of the published article is Mariana Amaro, as shown above. The author is residing at Departamento de Física, Universidade do Minho, Campus de Gualtar, 4710-057 Braga, Portugal.

Corona polarization in air is an usual method for depositing and injecting charges in polymers for production of electrets. The charges remain either on the surface or near it We have studied the effect of the polarization atmosphere, the polarization current and the time of polarization on the stability of the electrical charge of the electrets. For these studies we have used the technique of Thermally Stimulated Currents (TSC) that gives depolarization currents due to the jumping of the charges from traps, when the sample is heated up at a constant rate.

The Layer-by-Layer (LbL) technique has recently been developed as a promising method for production of thin films functional molecular heterostructures since the interactions occurring, essentially ionic and hydrogen bonding patterns, are found to be identical to those observed in biological systems. Such films have been shown to be also potentially good mimics of biological membranes. Also, it is possible that a study of biological relevant molecules assembled in LbL films will provide a closer analogue to their role in cellular systems. Thin films of adenine (A) and the polyelectrolyte poly(vinylsulfonic acid sodium salt) (PVS), were prepared by cast and Layer-by-layer (LbL) techniques. In this article, the experimental results on the UV irradiation of adenine cast films are described and the effect of 140 nm irradiation, with an estimated dose of about 8.5 × 10−4 W/m2, is evaluated at the molecular level.

Adsorption processes in layer-by-layer films are discussed using poly(o-methoxyaniline) (POMA) as a case study and also comparing with results for other polymers from the literature. This follows a brief overview of the materials and characterization techniques employed for self-assembled films, including their possible applications. The original paradigm of the self-assembly method is associated with spontaneous adsorption of oppositely charged polymer layers. While this rationale has been successful in explaining adsorption mechanisms for some polyelectrolytes, for polyanilines other interactions must be included. For POMA, in particular, at least three types of interactions are identified, namely van der Waals forces, ionic interactions and H-bonding. Furthermore, H-bonding is responsible for a number of effects even for charged POMA where electrostatic attraction was expected to predominate. Such effects include POMA dedoping upon contact with a glass substrate at early stages of adsorption, and the non-linear increase in the adsorbed amount with the number of POMA/poly(ethenesulfonic acid) (PVS) bilayers deposited in a multilayer structure. Adsorption of a POMA layer on a glass substrate or on an already formed POMA/PVS film occurs in two steps: a fast, first-order kinetics process with a characteristic time of a few seconds and a slower process represented by a Johnson-Mehl-Avrami function with a characteristic time of hundreds of seconds. These correspond basically to nucleation and growth mechanisms which is corroborated by atomic force microscopy measurements. The amount of material adsorbed in any given layer depends on experimental parameters, especially polymer concentration and pH, owing to the different extents of H-bonding that may allow POMA to adsorb on itself or on PVS molecules.

The final examples in our ellipticine/pyrrolocarbazole synthesis programme are 7,10-dimethoxyellipticine 1a and the corresponding pyrrolocarbazoles 2a and 3a which have been synthesised from 4,6-dimethoxyindole.

The understanding of radiation damage within cells, and thence mutagenesis, depends upon a detailed knowledge of the spectroscopy and dissociation dynamics of water. Results of a new study of the electronic state spectroscopy of water, using synchrotron radiation are reported. In order to gain some insight into how the spectroscopy and dissociation dynamics of water is influenced by its environment we also report photo-absorption spectra of water within thin films of poly(o-methoxyaniline) which have been suggested as a good mimic for biological membranes in the cellular environment. Comparison of these spectra with those of gaseous water and condensed amorphous water ice suggest that water in such films is similar to gaseous water and does not show the blue shift suggested in some cellular models. The lowest energy of OH production from dissociation of water in the cellular environment may therefore be around 6.7 eV (185 nm).