Oxidação de compostos orgânicos com H2O2 catalisada por metaloporfirinas

Mestrado em Química Orgânica e Produtos NaturaisA procura de catalisadores robustos e eficientes, nomeadamente catalisadores suportados, capazes de promover a oxidação selectiva de compostos orgânicos de forma sustentável, tem sido um dos maiores desafios da química orgânica nas últimas décadas. O uso de metaloporfirinas como catalisadores em reacções de oxidação com vários oxidantes, de onde se deve destacar o peróxido de hidrogénio, e a sua aplicação na transformação de compostos orgânicos têm levado ao desenvolvimento de alguns métodos eficientes, ambientalmente benignos, com grande potencial em síntese química de pequena escala, bem como em futuras utilizações à escala industrial. Estes estudos têm levado a várias considerações sobre os processos de actuação destes catalisadores, que originam transformações semelhantes às verificadas in vivo, quando catalisadas pelo citocromo P450. O trabalho experimental apresentado nesta dissertação envolveu a síntese de catalisadores robustos baseados na meso-tetraquis(pentafluorofenil)porfirina. No capítulo 1 desta dissertação é feita uma breve revisão bibliográfica sobre a síntese de porfirinas e de metaloporfirinas, bem como de algumas aplicações destes complexos em catálise oxidativa. No capítulo 2 são apresentadas as rotas sintéticas que levaram à obtenção da meso-tetraquis(pentafluorofenil)porfirina e dos seus derivados, quer por intermédio de uma reacção de cicloadição 1,3-dipolar com um ileto de azometino, quer através da ligação covalente da porfirina a um suporte do tipo polietilenoglicol (PEG5000). Por fim, as formas livres obtidas foram complexadas com acetato de manganês(II). A fase seguinte do trabalho, descrita no capítulo 3, compreendeu a avaliação da actividade catalítica dos complexos preparados, em processos de oxidação, todos em fase homogénea, usando sempre o peróxido de hidrogénio como oxidante. Nestes ensaios foram estudados seis substratos, designadamente cis-cicloocteno, 1-naftol, o-cresol, m-cresol, timol e carvacrol. A eficiência dos catalisadores não suportados foi comparada com a do catalisador suportado, de modo a avaliar a possível influência do suporte (PEG5000) na eficiência e/ou na estabilidade do catalisador porfirínico. ABSTRACT: The demand for robust and efficient catalysts, especially supported ones, capable of promoting the selective oxidation of organic compounds in a sustainable way, has been one of the greatest challenges of organic chemistry in the recent decades. The use of metalloporphyrins as catalysts in oxidation reactions with several oxidants, particularly hydrogen peroxide, and its application in the transformation of organic compounds have led to the development of some efficient, environmentally benign methods, with great potential in small scale chemical synthesis, as well as in future uses on an industrial scale. These studies have led to several considerations on the mode of action of these catalysts, which promote transformations similar to those observed in vivo, when catalysed by cytochrome P450 enzymes. The experimental work presented in this dissertation involves the synthesis of robust catalysts based on meso-tetrakis(pentafluorophenyl)porphyrin. Chapter 1 of this dissertation is a brief review on the synthesis of porphyrins and metalloporphyrins and on some applications of these complexes in oxidative catalysis. In chapter 2 the synthetic routes that lead to meso-tetrakis(pentafluorophenyl)porphyrin and its derivatives, are presented, either through a 1,3-cycloaddition reaction with an azomethine ylide, either by covalent linkage of the porphyrin to poly(ethylene glycol) (PEG5000) support. Finally, the free forms obtained were metallated by complexation with manganese acetate(II). The next phase of the work, described in chapter 3, include the evaluation of the catalytic activity of the complexes prepared, in oxidation processes, all in homogeneous phase, always using hydrogen peroxide as oxidant. Six substrates were studied, namely cis-cyclooctene, 1-naphthol, o-cresol, m-cresol, thymol and carvacrol. The efficiency of unsupported catalysts was compared with that of the supported catalyst, in order to evaluate the possible influence of PEG5000 in the efficiency and/or stability of the porphyrin catalyst

Enhancing the interface behavior on polycarbonate/elastomeric blends: morphological, structural, and thermal characterization

A systematic study was performed to provide better understanding of the effect of elas tomeric materials on the behavior of polycarbonate blends (PC). Thus, blends of PC with different amounts of elastomers, such as copolyether ester elastomer (COPE), acrylonitrile–butadiene–styrene (ABS), maleic anhydride-grafted ABS (ABS-g-MA), and styrene–ethylene–butylene–styrene (SEBS g-MA) were prepared in a co-rotating twin-screw extruder. The materials were characterized by an electronic microscopy (SEM), an infrared spectroscopy (FTIR), and thermal (DSC) and thermo mechanical (DMA) techniques. The incorporation of elastomeric phases was observed by changes in the FTIR band’s intensity, whereas a new shoulder of the ester band of COPE at 1728 cm−1 indicates the occurrence of a transesterification reaction. Unmodified and modified ABS (5% and 10%) did not affect the glass transition temperature (Tg) of PC, while 1% SEBS-g-MA slightly increased this value. PC/10% COPE showed that a decrease in Tg of 25 ◦C has a result of better compatibilization between both phases, which is visible via SEM. SEM analysis identified three main toughening mechanisms, depending on the type of elastomer. Unlike any other study, this work deepens the knowledge, in a comparative way, to understand the elastomeric effect at the interface and consequently, on the mechanical behavior of PC systems.This work was founded by Portugal 2020, and Fundo Social Europeu (FSE) through Programa Operacional Regional do NORTE (NORTE-08-5369–FSE-000034), developed under the pro gram “IMPULSE—Polímeros e Compósitos: Drivers da inovação tecnológica e da competitividade industrial”. The authors also acknowledge the Portuguese Foundation of Science and Technology (TSSiPRO—TECHNOLOGIES FOR SUSTAINABLE AND SMART INNOVATIVE PRODUCTS— NORTE-01-0145-FEDER-000015) and UID/CTM/50025/2013 for the financial support

Synthesis and evaluation of heterocyclic pyrrolidene imines as optical chemosensors

Imine derivatives are an important class of compounds due their biological and optical properties making them suitable for several applications such as chemosensors, photochromic compounds, among others. In recent years the search for new colorimetric chemosensors for anions has been of great interest because of the role that ions play in chemical and biological processes. In this context and as part of an on-going research to develop efficient heterocyclic systems for photochromic and chemosensory applications, we report the synthesis, the photophysical characterization and the chemosensory ability of pyrrolidene heterocyclic imines functionalized with aryl or naphthyl moieties. Keywords: Imines,FCTFEDERQRE

Push-pull heterocyclic dyes based on pyrrole and thiophene: synthesis and evaluation of their optical, redox and photovoltaic properties

Three heterocyclic dyes were synthesized having in mind the changes in the photovoltaic, optical and redox properties by functionalization of 5-aryl-thieno[3,2-b]thiophene, 5-arylthiophene and bis-methylpyrrolylthiophene π-bridges with different donor, acceptor/anchoring groups. Knoevenagel condensation of the aldehyde precursors with 2-cyanoacetic acid was used to prepare the donor-acceptor functionalized heterocyclic molecules. These organic metal-free dyes are constituted by thieno[3,2-b]thiophene, arylthiophene, bis-methylpyrrolylthiophene, spacers and one or two cyanoacetic acid acceptor groups and different electron donor groups (alkoxyl, and pyrrole electron-rich heterocycle). The evaluation of the redox, optical and photovoltaic properties of these compounds indicate that 5-aryl-thieno[3,2-b]thiophene-based dye functionalized with an ethoxyl electron donor and a cyanoacetic acid electron acceptor group/anchoring moiety displays as sensitizer for DSSCs the best conversion efficiency (2.21%). It is mainly assigned to the higher molar extinction coefficient, long π-conjugation of the heterocyclic system, higher oxidation potential and strong electron donating capacity of the ethoxyl group compared to the pirrolyl moiety.Thanks are due to the Fundacao para a Ciencia e Tecnologia (FCT) for a PhD grant to S.S.M. Fernandes (SFRH/BD/87786/2012) and to FEDER-COMPETE for financial support at the research center CQUM (UID/QUI/0686/2016) and (UID/QUI/0686/2020). The NMR spectrometers are part of the National NMR Network (PTNMR) and are partially supported by Infrastructure Project No. 022161 (co-financed by FEDER through COMPETE 2020, POCI and PORL and FCT through PIDDAC). The group in Porto would like to acknowledge the European Commission through the Seventh Framework Programme, the Specific Programme "Ideas" of the European Research Council for research and technological development as part of an Advanced Grant under Grant No. 321315, which also partially funded this work. Some of this work was also performed under the project "SunStorage-Harvesting and storage of solar energy", with reference POCI-01-0145-FEDER-016387, funded by the European Regional Development Fund (ERDF), through COMPETE 2020-Operational Programme for Competitiveness and Internationalization (OPCI), and by national funds, through FCT. The group in Porto is also thankful to POCI-01-0145-FEDER-006939 (Laboratory for Process Engineering, Environment, Biotechnology and Energy-UID/EQU/00511/2013) funded by the European Regional Development Fund (ERDF), through COMPETE2020-Programa Operacional Competitividade e Internacionalizacao (POCI) and by national funds, LEPABE-2-ECO-INNOVATION, supported by the North Portugal Regional Operational Programme (NORTE 2020), under the Portugal 2020 Partnership Agreement, through the European Regional Development Fund (ERD). Institutional Review Board Statement: Not applicable

Development of iridium porphyrin arrays by axial coordination trough N-bidentate ligand: Synthesis and evaluation of the optical, electrochemical and thermal properties

Several organic compounds have been used in optoelectronics devices; porphyrins, due to their interesting optical and electronic properties, have shown an attractive potential to be used on molecular electronics. Among other advantages, porphyrins easily coordinate with several metal ions, which allows the assembly with peripheral or axial ligands introducing new properties to the supramolecular porphyrin. In this work, a new metalloporphyrin system with 5,10,15,20-(tetra-p-tolyl)porphyrin (ttp) and iridium(III) where 4,4’-bipyridine (bpy) coordinate in the axial positions was successfully synthetized, through the formation of “shish kebab” structures. This new compound was characterized through ultraviolet-visible, proton nuclear magnetic resonance, Fourier-transform infrared and Raman spectroscopies, thermogravimetry, differential scanning calorimeter and cyclic voltammetry. The introduction of the bpy on the metalloporphyrin moiety exhibited important influence on the optical, thermal and electrochemical properties.The authors acknowledge the Portuguese Foundation of Science and Technology (TSSiPRO – TECHNOLOGIES FOR SUSTAINABLE AND SMART INNOVATIVE PRODUCTS – NORTE-01-0145-FEDER-000015) and UID/CTM/50025/2013 for the financial support.info:eu-repo/semantics/publishedVersio

Synthesis and characterization of novel thieno[3,2-b]thiophene based metal-free organic dyes with different heteroaromatic donor moieties as sensitizers for dye-sensitized solar cells

Four novel heterocycle dyes 3a-d were synthesized in order to study the variations produced in the optical, electronic and photovoltaic properties by substitution of different electron-rich heterocyclic groups to the thieno[3,2-b]thiophene system. The final push-pull conjugated dyes 3a-d were synthesized by Suzuki-Miyaura coupling reaction followed by Knoevenagel condensation of the corresponding aldehyde precursors with cyanoacrylic acid 2a-d. These new push-pull systems are based on a thieno[3,2-b]thiophene spacer, a cyanoacetic acid anchoring group and several electron-rich heterocycles (thiophene, pyrrole and furan) as donor groups. The multidisciplinary study concerning the optical, redox and photovoltaic characterization of the dyes reveals that compound 3b bearing a hexyl-bithiophene donor group/heterocyclic spacer exhibits the best overall conversion efficiency (2.49%) as sensitizer in nanocrystalline TiO2 dye sensitized solar cells. Co-adsorption studies between N719 and 3b revealed that upon addition of N719 co-adsorbent, the optimized cell efficiencies were improved by 16–77%. The best efficiency was 4.40%, corresponding to 54% of the photovoltaic performance of the N719-based DSSC fabricated and measured under similar conditions.FCTFEDERQRENEuropean Research Council (Contract no: 321315

Adaptable photochromic switches with self-aggregating heterocyclic azo dyes

It is well-known that the thermal isomerization kinetics of photochromic azo dyes can be modulated by subtle changes in their chemical architecture. However, the availability of an orthogonal input to control the thermal relaxation of azo dyes is essential to enable access to multifunctional and adaptive photochromic switches based on these particular organic chromophores. In this work, we have designed and synthesized a new family of green-light-activated heterocyclic azo derivatives that modify their switching capabilities as a function of concentration. In this line, we have investigated their self-assembly and the nature of the supramolecular aggregates formed by means of dynamic light scattering, polarized optical microscopy, and X-ray diffraction. Indeed, imparting control over the self-assembly of these organic dyes allows to fine-tune their thermal relaxation time and produce adaptable photochromic switches. Specifically, swapping the azo dye concentration between values located above and below the corresponding critical aggregation concentration modifies significantly the relaxation time up to 250 times, i.e., from the millisecond to the microsecond timescale. Moreover, the optical density of the system can be switched back and forth hundreds of times, for both diluted and concentrated solutions, without any sign of fatigue.Financial support for this research was obtained from the Ministerio de Economia y Competitividad (Spain, PGC2018-095477-B-I00, CTQ2016-78454-C2-1-R, and CTQ2017-84998-P MINECO/FEDER). Thanks are also due to Fundacao para a Ciencia e Tecnologia (Portugal) for financial support to the Portuguese NMR network (PTNMR, Bruker Avance III 400-Univ. Minho), FCT, and FEDER (European Fund for Regional Development)-COMPETEQREN-EU for financial support to the research centre CQ/UM [ref UID/QUI/00686/2013 and UID/QUI/0686/2016], and a PhD grant to M.C.R.C. (SFRH/BD/78037/2011)

COMMUNICATION IN THE TRANSITION OF NURSING CARE IN AN EMERGENCY DEPARTMENT IN PORTUGAL

Objective: to identify nurses’ opinions about the transition of care at shift change in the emergency department and understand their knowledge about patient safety. Method: quantitative, descriptive, cross-sectional study, conducted in January 2019, in an emergency department of a hospital in the metropolitan area of Lisbon, Portugal. Non-probability convenience sample with 50 nurses. Data analysis used descriptive and inferential statistics, with the Mann-Whitney test. Results: information transmitted is updated (80%); there is noise that interferes with the transmission of care (84%); patient assessment in the transition of care is beneficial (84%). 50% know the international goals for patient safety; 84% agree that the ISBAR methodology contributes to patient safety. Conclusion: it is evident the formation of professionals and the use of standardized instruments as fundamental strategies for patient safety in the transition of care.Objetivo: conhecer a opinião dos enfermeiros sobre a transição de cuidados na mudança de turno no serviço de emergência e perceber os seus conhecimentos acerca da temática da segurança do paciente. Método: estudo quantitativo, descritivo, transversal, realizado em janeiro de 2019, num serviço de emergência, de um hospital na área metropolitana de Lisboa, Portugal. Amostra não probabilística de conveniência com 50 enfermeiros. A análise dos dados recorreu à estatística descritiva e inferencial, com o teste de Mann-Whitney. Resultados: a informação transmitida é atualizada (80%); existe ruído que interfere na transmissão de cuidados (84%); a avaliação do paciente na transição de cuidados é benéfica (84%). 50% conhece as metas internacionais para a segurança do paciente; 84% concorda que a metodologia ISBAR contribui para a segurança do paciente. Conclusão: evidencia-se a formação dos profissionais e a utilização de instrumento padronizado como estratégias fundamentais para a segurança do paciente na transição de cuidados.Objetivo: conocer la opinión de los enfermeros sobre la transición de la atención en el cambio de turno en elservicio de emergencia y percibir sus conocimientos sobre el tema de la seguridad del paciente. Método: estudiocuantitativo, descriptivo, transversal, realizado en enero de 2019, en un servicio de urgencias, de un hospital del áreametropolitana de Lisboa, Portugal. Muestra no probabilística de conveniencia con 50 enfermeras. En el análisis de losdatos se utilizaron estadísticas descriptivas e inferenciales, con la prueba de Mann-Whitney. Resultados: la informacióntransmitida está actualizada (80%); hay ruido que interfiere en la transmisión de la atención (84%); la evaluación delpaciente en la transición de la atención es benéfica (84%). El 50% conoce los objetivos internacionales de seguridaddel paciente; el 84% está de acuerdo en que la metodología ISBAR contribuye a la seguridad del paciente. Conclusión:se evidencia la formación de los profesionales y el uso del instrumento estandarizado como estrategias fundamentalespara la seguridad del paciente en la transición de la attención

Enhancing the longevity and functionality of Ti-Ag dry electrodes for remote biomedical applications: a comprehensive study

This study aims to evaluate the lifespan of Ti-Ag dry electrodes prepared using flexible polytetrafluoroethylene (PTFE) substrates. Following previous studies, the electrodes were designed to be integrated into wearables for remote electromyography (EMG) monitoring and electrical stimulation (FES) therapy. Four types of Ti-Ag electrodes were prepared by DC magnetron sputtering, using a pure-Ti target doped with a growing number of Ag pellets. After extensive characterization of their chemical composition and (micro)structural evolution, the Ti-Ag electrodes were immersed in an artificial sweat solution (standard ISO-3160-2) at 37 °C with constant stirring. Results revealed that all the Ti-Ag electrodes maintained their integrity and functionality for 24 h. Although there was a notable increase in electrical resistivity beyond this timeframe, the acquisition and transmission of (bio)signals remained viable for electrodes with Ag/Ti ratios below 0.23. However, electrodes with higher Ag content (Ag/Ti = 0.31) became insulators after 7 days of immersion due to excessive Ag release into the sweat solution. This study concludes that higher Ag/Ti atomic ratios result in heightened corrosion processes on the electrode’s surface, consequently diminishing their lifespan despite the advantages of incorporating Ag into their composition. This research highlights the critical importance of evaluating electrode longevity, especially in remote biomedical applications like smart wearables, where electrode performance over time is crucial for reliable and sustained monitoring and stimulation.This research was funded by the European Regional Development Fund (ERDF) through the Operational Programme for Competitiveness and Internationalization (COMPETE 2020) under Portugal 2020, in the framework of the NanoStim (POCI-01-0247-FEDER-045908) and NanoID (NORTE-01-0247-FEDER-046985) Projects

High Piezoelectric Output Voltage from Blue Fluorescent N,N-Dimethyl-4-nitroaniline Nano Crystals in Poly-L-Lactic Acid Electrospun Fibers

N,N-dimethyl-4-nitroaniline is a piezoelectric organic superplastic and superelastic charge transfer molecular crystal that crystallizes in an acentric structure. Organic mechanical flexible crystals are of great importance as they stand between soft matter and inorganic crystals. Highly aligned poly-l-lactic acid polymer microfibers with embedded N,N-dimethyl-4-nitroaniline nanocrystals are fabricated using the electrospinning technique, and their piezoelectric and optical properties are explored as hybrid systems. The composite fibers display an extraordinarily high piezoelectric output response, where for a small stress of 5.0 × 103 Nm−2, an effective piezoelectric voltage coefficient of geff = 4.1 VmN−1 is obtained, which is one of the highest among piezoelectric polymers and organic lead perovskites. Mechanically, they exhibit an average increase of 67% in the Young modulus compared to polymer microfibers alone, reaching 55 MPa, while the tensile strength reaches 2.8 MPa. Furthermore, the fibers show solid-state blue fluorescence, important for emission applications, with a long lifetime decay (147 ns) lifetime decay. The present results show that nanocrystals from small organic molecules with luminescent, elastic and piezoelectric properties form a mechanically strong hybrid functional 2-dimensional array, promising for applications in energy harvesting through the piezoelectric effect and as solid-state blue emitters.This research was funded by Fundação para a Ciência e Tecnologia through FEDER (European Fund for Regional Development)-COMPETE-QREN-EU (ref. UID/FIS/04650/2013 and UID/FIS/04650/2019) and E-Field - "Electric-Field Engineered Lattice Distortions (E-FiELD) for optoelectronic devices", ref. PTDC/NAN-MAT/0098/2020