An Oxalate-Bridged Copper(II) Complex Combining Monodentate Benzoate, 2,2'-bipyridine and Aqua Ligands:Synthesis, Crystal Structure and Investigation of Magnetic Properties

A dinuclear copper(II) complex of formula [{Cu(bipy)(bzt)(OH2)}2(μ-ox)] (1) (where bipy = 2,2'-bipyridine, bzt = benzoate and ox = oxalate) was synthesised and characterised by diffractometric (powder and single-crystal XRD) and thermogravimetric (TG/DTG) analyses, spectroscopic techniques (IR, Raman, electron paramagnetic resonance spectroscopy (EPR) and electronic spectroscopy), magnetic measurements and density functional theory (DFT) calculations. The analysis of the crystal structure revealed that the oxalate ligand is in bis(bidentate) coordination mode between two copper(II) centres. The other four positions of the coordination environment of the copper(II) ion are occupied by one water molecule, a bidentate bipy and a monodentate bzt ligand. An inversion centre located on the ox ligand generates the other half of the dinuclear complex. Intermolecular hydrogen bonds and π-π interactions are responsible for the organisation of the molecules in the solid state. Molar magnetic susceptibility and field dependence magnetisation studies evidenced a weak intramolecular-ferromagnetic interaction (J = +2.9 cm-1) between the metal ions. The sign and magnitude of the calculated J value by density functional theory (DFT) are in agreement with the experimental data

Structure and magnetic properties of two new lanthanide complexes with the 1-((E)-2-pyridinylmethylidene)semicarbazone ligand

Two novel semicarbazone-lanthanide(III) complexes were prepared and structurally characterized as [Ln (Hscpy)2 (NO3)2]NO3·MeOH (Ln = Gd and Tb; Hscpy = 1-((E)-2-pyridinylmethylidene)semicarbazone). The 4f metal ions experience deca-coordination geometry. Each molecular formula contains two neutral Hscpy molecules in the keto form coordinated through two nitrogen atoms and one oxygen atom, while two nitrate ligands are both coordinated in a chelate mode. The 1 + charge of the cation-complex is balanced by a nitrate anion. Extensive intermolecular hydrogen bonds are formed through the methanol solvate molecule, which acts both as a donor and an acceptor molecule. The chemical composition of the compounds was confirmed by high resolution mass spectra (ESI-MS); peaks at m/z = 122.07 and 148.05, assigned to the fragments C6H8N3+ and C7H6N3O+, respectively, are in agreement with the coordination of Hscpy. Alternating current magnetic susceptibility analysis was performed in the 10–10000 Hz range, and the terbium-complex showed slow relaxation of the magnetization when immersed in a static magnetic field of 1 kOe and 1.5 kOe, with an activation barrier to the relaxation (21.9(4) cm−1) among the highest found for ten-coordinated Tb(III) complexes. This behavior of slow relaxation of the magnetization is relevant as a memory effect regarding the development of Single Molecule Magnets (SMM)

Supramolecular assembly of new heteropolymetalic molecules based on tetraiminodiphenolate macrocycle and hexacyanometallate anions: magnetostructural and spectroscopic properties

Herein we report on the synthesis, single crystal X-ray structure, spectroscopic and magnetic properties of [{Cu2(tidf)(H2O)}2(μ-CN)2Fe(CN)4]·6H2O (1), [Cu2(tidf)(H2O)2][Ni(CN)4] (2) and [Cu2(tidf)(H2O)2][Fe(CN)5NO]·H2O (3) (tidf = a Robson type macrocyclic ligand obtained on condensation of 2,6-diformyl-4-methylphenol and 1,3-diaminopropane). Complex (1) is pentanuclear; two paramagnetic dicopper(II) units are linked by a hexacyanoferrate(II) ion through two cyano-bridges. All compounds exhibit extensive, three-dimensional, supramolecular structures supported by classic hydrogen bonding between the coordinated aqua ligands, water molecules and cyano groups. Magnetism as a function of the temperature of complexes 1-3 is consistent with a strong antiferromagnetism with exchange parameters 2J estimated -783(29), -913(2), -905(1), respectively.CNPqFINEP (CT-Infra 03/2001)BBSR

SENTIMENTOS VIVENCIADOS POR ACOMPANHANTES DE PACIENTES CRÍTICOS INTERNADOS EM UNIDADES DE TRATAMENTO INTENSIVO

Introduction: The Intensive Care Unit is a hospital sector that differs from the others, as it is a place for advanced care and constant monitoring, which generally contributes to the development of family fragility, especially when the patient is in a state of hemodynamically unstable. Objective: Reflect on the emotions of family members and transcend a broad reflection, covering the feelings of family members regarding the patient's hospitalization in the Intensive Care Unit. Methodology: This is a study of the narrative literature review type, with characteristics of a theoretical-reflective type, with a qualitative approach and an exploratory bias. The search took place in the databases, BDENF, LILACS and the SciELO portal, with the inclusion criteria, articles published in full with free access and that addressed the subject of the study, dissertations, theses, book chapters, in Portuguese and English. And exclusion criteria, studies incompatible with the research theme. Furthermore, there was a search for health descriptors combined with the Boolean operator “AND”. Results: In this scenario, they showed that the main feelings shown by the companions of critically ill patients in the ICU are: anguish, fear, impotence, sadness, guilt and despair. Conclusion: Therefore, qualified professionals are important to promote a better connection with companions, and thus improve the assistance offered, which also applies to companions, taking care of the emotional factor and solving any possible doubts that may arise.Introducción: La Unidad de Cuidados Intensivos es un sector hospitalario que se diferencia de los demás, porque es un lugar de cuidados avanzados y monitoreo constante, lo que suele corroborar el desarrollo de la fragilidad familiar, especialmente cuando el paciente se encuentra en un estado hemodinámicamente inestable. Objetivo: Reflexionar sobre las emociones de los familiares y trascender una amplia reflexión, abarcando los sentimientos de los familiares respecto a la hospitalización del paciente en la Unidad de Cuidados Intensivos. Metodología: Se trata de un estudio del tipo de revisión narrativa de la literatura, con características del tipo teórico-reflexivo, de abordaje cualitativo y sesgo exploratorio. La búsqueda se realizó en las bases de datos, BDENF, LILACS y en el portal SciELO, con los criterios de inclusión, artículos publicados en la integración de libre acceso y que abordaron el tema del estudio, disertaciones, tesis, capítulos de libros, en portugués e inglés. Y criterios de exclusión, estudios incompatibles con el tema de investigación. Además, se investigaron los descriptores de salud combinados con el operador booleano "AND". Resultados: En este escenario, mostraron que los principales sentimientos mostrados por los acompañantes de pacientes críticamente enfermos en la UCI son: angustia, miedo, impotencia, tristeza, culpa y desesperación. Conclusión: Por lo tanto, los profesionales son importantes y cualificados para promover una mejor conexión con los acompañantes, y así mejorar la asistencia ofrecida, lo que también se aplica a los acompañantes, cuidando el factor emocional y conteniendo cualquier duda que pueda surgir.Introdução: A Unidade de Terapia Intensiva, é um setor hospitalar que se difere dos demais, por se tratar de um local destinado a cuidados avançados e constante monitorização, que geralmente corrobora para o desenvolvimento de fragilidade familiar, principalmente quando o paciente se encontra em estado hemodinamicamente instável. Objetivo: Refletir sobre as emoções dos familiares e transcender uma reflexão ampla, abrangendo os sentimentos dos familiares em relação a internação do paciente em Unidade de Terapia Intensiva. Metodologia: Trata-se de um estudo do tipo revisão narrativa da literatura, com características do tipo teórico-reflexivo, de abordagem qualitativa e viés exploratória. A busca ocorreu nas bases, BDENF, LILACS e no portal SciELO, com os critérios de inclusão, artigos publicados na integra de acesso gratuito e que abordassem a temática do estudo, dissertações, teses, capítulos de livros, nos idiomas português e inglês. E critérios de exclusão, estudos incompatíveis com a temática da pesquisa. Ademais, ocorreu a pesquisa dos descritores em saúde combinados com o operador booleano “AND”. Resultados: Nesse cenário, evidenciaram que os principais sentimentos mostrados pelos acompanhantes de pacientes críticos na UTI são: angustia, medo, impotência, tristeza, culpa e desespero. Conclusão: Portanto, são importantes profissionais habilitados para promoverem uma melhor conexão com os acompanhantes, e assim melhorar a assistência ofertada, que também se aplica aos acompanhantes, cuidando do fator emocional e sanando todas as eventuais dúvidas que possam a vir surgir

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Pulse and continous wave Electron Paramagnetic Resonance spectroscopy applied to poly(o-metoxyaniline)

O trabalho envolve o estudo de amostras de poli(o-metoxianilina) (POMA) , dopadas com ácido trifluoracético (TFA) através das técnicas de espectroscopia de Ressonância Paramagnética Eletrônica (RPE) de onda contínua e pulsada. O sinal de RPE observado é atribuído a elétrons desemparelhados na cadeia polimérica, denominados pólarons. Uma vez que estes pólarons possuem carga elétrica e spin eletrônico, os estudos de RPE podem fornecer informações a respeito de sua mobilidade e sobre as propriedades de transporte no material em escala microscópica. O efeito da presença de oxigênio molecular, O2, (S=1), sobre a forma da linha CW é estudado em função do grau de dopagem e do envelhecimento das amostras. O alargamento observado da linha de RPE deve-se a processos de colisão entre o pólaron móvel e os spins localizados do O2. Durante uma colisão, os dois spins interagem entre si através de interações de troca magnética, produzindo spin-flips simultâneos. Uma vez que os spins fixos estão fortemente acoplados com a rede, o processo de relaxação spin-rede do pólaron torna-se muito eficiente, produzindo o alargamento da linha. Como resultado deste processo de colisões, a dependência da largura de linha em função da temperatura mostra um máximo em torno de 190 K. Modelos teóricos serão apresentados, a partir dos quais serão estimados os valores para a mobilidade do pólaron, raio de ação da interação pólaron-oxigênio e constantes de acoplamento. Amostras sintetizadas na presença de oxigênio possuem tempos de relaxação muito curtos em toda a faixa de temperatura estudada (2-280 K), impossibilitando a observação da RPE pulsada. Amostras envelhecidas mostram um comportamento diferente, característico da substituição do oxigênio por água, que leva ao cancelamento do efeito de alargamento. Nestas amostras, assim como em amostras sintetizadas em atmosfera inerte, estudos adicionais de RPE pulsada permitem, através de técnicas associadas ao eco de spins eletrônicos, ESE, a obtenção dos tempos de relaxação spin-spin e spin-rede, assim como o estudo das interações hiperfinas entre pólaron e núcleos vizinhos, 1H, 13C e 14N, que não são resolvidas no espectro CW. A quantificação e qualificação de núcleos interagentes, os quais possuem desdobramentos hiperfinos fracos, podem ser realizadas através das técnicas uni e bidimensionais, como ESEEM, 2DESEEM e HYSCORE.Continuous wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) techniques are used to study structural and dynarnical properties of poly(o-metoxyaniline) (POMA) doped in trifluoroacetic (TFA) solution. The observed EPR spectrum is attributed to chain unpaired electron spins named polarons. Since polarons carry both charge and spin, EPR studies can provide information about charge transport properties of the material on a microscopic scale. The width of the EPR signal reflects the interaction of the polarons with their environments. In the present study, special attention is given to the EPR linewidth, which is usually broadened by the presence of molecular oxygen, O2, (S=1). The oxygen induced linewidth is explained by the mutual spin flips occurring during the collision of a mobile polaron with fixed paramagnetic O2. The temperature dependence of the linewidth shows a maximum around 190K associated with these collision processes. Such effects are studied as a function of doping concentration, sample aging and vacuum conditions. From a theoretical model proposed in the field, some parameters, associated with the polaron mobility and exchange interaction between polaron and oxygen, are estimated. All synthesized samples have very short spin relaxation times in all the studied temperature range (2-280K), making impossible their observation by the pulsed EPR techniques. Aged samples show a different behavior; their long relaxation times seem to indicate that the substitution of O2 by H2O has promoted the canceling of the broadening effect. Studies are under progress to establish a sample preparation procedure in which the resulting samples are free of molecular oxygen. Aged samples have been used to perform preliminary studies conducted by the pulsed EPR techniques. Spin-echo spectroscopy and relaxation time measurements were interpreted on the basis of the interaction of the polaron with neighboring nuclei, such as 1H, 13C e 14N, which are not resolved in the CW spectra. To better understand the nature of the CW and pulsed EPR spectroscopy, one special chapter will introduce the several techniques, which are commonly employed in our research

Not available

Este trabalho relaciona-se à aplicação das técnicas de Ressonância Paramagnética Eletrônica (RPE) de onda contínua e pulsada em sistemas de interesse biológico e ambiental, bem como técnicas computacionais de análise espectral. No estudo realizado em uma amostra padrão de ácido húmico, revimos técnicas de onda contínua e analisamos os limites de validade dessas técnicas, comparando os resultados com técnicas pulsadas e simulações. Ainda nesse estudo, determinamos a presença de metais como Fe(lII) e Cu(II), e, para este último, a presença de ligantes \' 14 ANTPOT.N\' e \'16 ANTPOT. 0\'. Utilizando um birradical sintético, verificamos os limites teóricos de aplicação das técnicas de Coerência de Duplo Quantum (CDQ ou C2Q), demonstrando que mesmo em presença de interação de troca forte, particularmente, pode-se determinar distàncias através da interação elétron-elétron. Os resultados são corroborados por experimentos de RPE de onda contínua, através da determinação do parâmetro de desdobramento de campo zero, D, assim como simulações moleculares. No estudo de uma proteína da família das septinas, cuja estrutura cristalográfica não se encontra disponível até o momento, demonstramos mudanças conformacionais induzidas por exposição à temperatura de \'37 GRAUS\'C e pela presença de uréia. Essas mudanças relacionam-se à formação de fibras e agregados, cujo papel no desenvolvimento de doenças neurodegenerativas tem sido apontado e estudado.A teoria e aspectos numéricos do Método da Diagonalização Filtrada (FDM), desenvolvido recentemente para análise espectral de alta resolução de sinais temporais, são revistas. Algumas aplicações do método são discutidas e detalhadas, entre elas uma recente aplicação do FDM que consiste no cálculo computacional dos campos de ressonância associados à ressonância eletrônica de varredura de campo em freqüência constanteThis work is concerned with the application of the continuous and pulsed wave Electron Paramagnetic Resonance (EPR) in systems of biological and environmental interest, as well as with the development of computational techniques for spectral analysis. In the study of a standard humic acid sample, we reviewed the continuous wave techniques to establish their validity limits, comparing their results with those of the pulsed ones. With this sample, we also determined the presence of metais, Fe(III) and Cu(II), and the existence of 14N e 160, as ligands to the Cu. By means of a synthetic biradical, we verified the theoretical application limits of the Double Quantum Coherence (DQC) techniques, demonstrating that even in the presence of unresolved hyperfine interactions and strong exchange coupling, distances can be determined from the electron-electron interaction. Results are in agreement with the determination of the zero-field splitting parameter, D, by continuous wave EPR measurements and molecular simulations. In the study of a protein of the family of septins, whose crystallographic structure is not available at present, we observed conformational changes induced by temperature exposition at 37°C and by the presence of urea. These changes relate with the formation of fibers and agzregates, whose role in development of cancer and neurodegenerative diseases has been pointed out and studied. The theory and numerical aspects of the recently developed Filter Diagonalization Method (FDM) for high-resolution spectral analysis of transiel signals are reviewed. Some applications of the FDM to 1D time signals are discussed and detailed, one of them consisting of the application of the FDM in the computation of the eigenfields associated to the field-swept fixed-frequency resonanc

Not available

Este trabalho relaciona-se à aplicação das técnicas de Ressonância Paramagnética Eletrônica (RPE) de onda contínua e pulsada em sistemas de interesse biológico e ambiental, bem como técnicas computacionais de análise espectral. No estudo realizado em uma amostra padrão de ácido húmico, revimos técnicas de onda contínua e analisamos os limites de validade dessas técnicas, comparando os resultados com técnicas pulsadas e simulações. Ainda nesse estudo, determinamos a presença de metais como Fe(lII) e Cu(II), e, para este último, a presença de ligantes \' 14 ANTPOT.N\' e \'16 ANTPOT. 0\'. Utilizando um birradical sintético, verificamos os limites teóricos de aplicação das técnicas de Coerência de Duplo Quantum (CDQ ou C2Q), demonstrando que mesmo em presença de interação de troca forte, particularmente, pode-se determinar distàncias através da interação elétron-elétron. Os resultados são corroborados por experimentos de RPE de onda contínua, através da determinação do parâmetro de desdobramento de campo zero, D, assim como simulações moleculares. No estudo de uma proteína da família das septinas, cuja estrutura cristalográfica não se encontra disponível até o momento, demonstramos mudanças conformacionais induzidas por exposição à temperatura de \'37 GRAUS\'C e pela presença de uréia. Essas mudanças relacionam-se à formação de fibras e agregados, cujo papel no desenvolvimento de doenças neurodegenerativas tem sido apontado e estudado.A teoria e aspectos numéricos do Método da Diagonalização Filtrada (FDM), desenvolvido recentemente para análise espectral de alta resolução de sinais temporais, são revistas. Algumas aplicações do método são discutidas e detalhadas, entre elas uma recente aplicação do FDM que consiste no cálculo computacional dos campos de ressonância associados à ressonância eletrônica de varredura de campo em freqüência constanteThis work is concerned with the application of the continuous and pulsed wave Electron Paramagnetic Resonance (EPR) in systems of biological and environmental interest, as well as with the development of computational techniques for spectral analysis. In the study of a standard humic acid sample, we reviewed the continuous wave techniques to establish their validity limits, comparing their results with those of the pulsed ones. With this sample, we also determined the presence of metais, Fe(III) and Cu(II), and the existence of 14N e 160, as ligands to the Cu. By means of a synthetic biradical, we verified the theoretical application limits of the Double Quantum Coherence (DQC) techniques, demonstrating that even in the presence of unresolved hyperfine interactions and strong exchange coupling, distances can be determined from the electron-electron interaction. Results are in agreement with the determination of the zero-field splitting parameter, D, by continuous wave EPR measurements and molecular simulations. In the study of a protein of the family of septins, whose crystallographic structure is not available at present, we observed conformational changes induced by temperature exposition at 37°C and by the presence of urea. These changes relate with the formation of fibers and agzregates, whose role in development of cancer and neurodegenerative diseases has been pointed out and studied. The theory and numerical aspects of the recently developed Filter Diagonalization Method (FDM) for high-resolution spectral analysis of transiel signals are reviewed. Some applications of the FDM to 1D time signals are discussed and detailed, one of them consisting of the application of the FDM in the computation of the eigenfields associated to the field-swept fixed-frequency resonanc

Pulse and continous wave Electron Paramagnetic Resonance spectroscopy applied to poly(o-metoxyaniline)

O trabalho envolve o estudo de amostras de poli(o-metoxianilina) (POMA) , dopadas com ácido trifluoracético (TFA) através das técnicas de espectroscopia de Ressonância Paramagnética Eletrônica (RPE) de onda contínua e pulsada. O sinal de RPE observado é atribuído a elétrons desemparelhados na cadeia polimérica, denominados pólarons. Uma vez que estes pólarons possuem carga elétrica e spin eletrônico, os estudos de RPE podem fornecer informações a respeito de sua mobilidade e sobre as propriedades de transporte no material em escala microscópica. O efeito da presença de oxigênio molecular, O2, (S=1), sobre a forma da linha CW é estudado em função do grau de dopagem e do envelhecimento das amostras. O alargamento observado da linha de RPE deve-se a processos de colisão entre o pólaron móvel e os spins localizados do O2. Durante uma colisão, os dois spins interagem entre si através de interações de troca magnética, produzindo spin-flips simultâneos. Uma vez que os spins fixos estão fortemente acoplados com a rede, o processo de relaxação spin-rede do pólaron torna-se muito eficiente, produzindo o alargamento da linha. Como resultado deste processo de colisões, a dependência da largura de linha em função da temperatura mostra um máximo em torno de 190 K. Modelos teóricos serão apresentados, a partir dos quais serão estimados os valores para a mobilidade do pólaron, raio de ação da interação pólaron-oxigênio e constantes de acoplamento. Amostras sintetizadas na presença de oxigênio possuem tempos de relaxação muito curtos em toda a faixa de temperatura estudada (2-280 K), impossibilitando a observação da RPE pulsada. Amostras envelhecidas mostram um comportamento diferente, característico da substituição do oxigênio por água, que leva ao cancelamento do efeito de alargamento. Nestas amostras, assim como em amostras sintetizadas em atmosfera inerte, estudos adicionais de RPE pulsada permitem, através de técnicas associadas ao eco de spins eletrônicos, ESE, a obtenção dos tempos de relaxação spin-spin e spin-rede, assim como o estudo das interações hiperfinas entre pólaron e núcleos vizinhos, 1H, 13C e 14N, que não são resolvidas no espectro CW. A quantificação e qualificação de núcleos interagentes, os quais possuem desdobramentos hiperfinos fracos, podem ser realizadas através das técnicas uni e bidimensionais, como ESEEM, 2DESEEM e HYSCORE.Continuous wave (CW) and pulsed Electron Paramagnetic Resonance (EPR) techniques are used to study structural and dynarnical properties of poly(o-metoxyaniline) (POMA) doped in trifluoroacetic (TFA) solution. The observed EPR spectrum is attributed to chain unpaired electron spins named polarons. Since polarons carry both charge and spin, EPR studies can provide information about charge transport properties of the material on a microscopic scale. The width of the EPR signal reflects the interaction of the polarons with their environments. In the present study, special attention is given to the EPR linewidth, which is usually broadened by the presence of molecular oxygen, O2, (S=1). The oxygen induced linewidth is explained by the mutual spin flips occurring during the collision of a mobile polaron with fixed paramagnetic O2. The temperature dependence of the linewidth shows a maximum around 190K associated with these collision processes. Such effects are studied as a function of doping concentration, sample aging and vacuum conditions. From a theoretical model proposed in the field, some parameters, associated with the polaron mobility and exchange interaction between polaron and oxygen, are estimated. All synthesized samples have very short spin relaxation times in all the studied temperature range (2-280K), making impossible their observation by the pulsed EPR techniques. Aged samples show a different behavior; their long relaxation times seem to indicate that the substitution of O2 by H2O has promoted the canceling of the broadening effect. Studies are under progress to establish a sample preparation procedure in which the resulting samples are free of molecular oxygen. Aged samples have been used to perform preliminary studies conducted by the pulsed EPR techniques. Spin-echo spectroscopy and relaxation time measurements were interpreted on the basis of the interaction of the polaron with neighboring nuclei, such as 1H, 13C e 14N, which are not resolved in the CW spectra. To better understand the nature of the CW and pulsed EPR spectroscopy, one special chapter will introduce the several techniques, which are commonly employed in our research