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1.
Mult Scler ; 30(7): 899-924, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38357870

RESUMO

BACKGROUND: Epidemiological data reveal that 45% of persons with multiple sclerosis (PwMS) in France are more than 50 years. This population more than 50 is more susceptible to cancer, and this risk may be increased by frequent use of immunosuppressive drugs. Consequently, concerns have arisen about the potential increased risk of cancer in PwMS and how patients should be screened and managed in terms of cancer risk. OBJECTIVE: To develop evidence-based recommendations to manage the coexistence of cancer and multiple sclerosis (MS). METHODS: The French Group for Recommendations in MS collected articles from PubMed and university databases covering the period January 1975 through June 2022. The RAND/UCLA method was employed to achieve formal consensus. MS experts comprehensively reviewed the full-text articles and developed the initial recommendations. A group of multidisciplinary health care specialists then validated the final proposal. RESULTS: Five key questions were addressed, encompassing various topics such as cancer screening before or after initiating a disease-modifying therapy (DMT), appropriate management of MS in the context of cancer, recommended follow-up for cancer in patients receiving a DMT, and the potential reintroduction of a DMT after initial cancer treatment. A strong consensus was reached for all 31 recommendations. CONCLUSION: These recommendations propose a strategic approach to managing cancer risk in PwMS.


Assuntos
Esclerose Múltipla , Neoplasias , Humanos , Esclerose Múltipla/epidemiologia , Esclerose Múltipla/terapia , Neoplasias/epidemiologia , França/epidemiologia , Imunossupressores/uso terapêutico
2.
Front Psychiatry ; 14: 1168302, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37275973

RESUMO

Background: Anti-leucine-rich glioma-inactivated 1 (LGI1) encephalitis is a limbic encephalitis that rarely presents as an isolated psychiatric syndrome. Case presentation: A 70-year-old patient first presented with behavioral disorder including hyperactivity, euphoria, with disinhibition and accelerated speech associated with severe insomnia and cognitive disorder. A manic episode was diagnosed and he received various psychotropic medications with no improvement. Invesitgations were negative (MRI showed T2 aspecific hyperintensities with no hyperintensities in limbic regions and EEG was normal). He was transferred to a nursing home, with a diagnosis of neurodegenerative condition. Later, he was referred to our unit for further investigations. A cerebral 18F-FDG-PET revealed an association of frontal hypometabolism and temporal and striatum hypermetabolism and CSF analysis revealed slightly increased white blood cell counts. Plasmatic anti-LGI1 antibodies were detected. The patient was treated with intra-venous immunoglobulin (IvIg) but showed no improvement. Second-line treatment (a combination of rituximab and cyclophosmphamide) was then administered for a year, leading to an improvement of neuropsychiatric symptoms and normalization of metabolic impairment on 18F-FDG-PET. Conclusion: In this report, we describe a novel case of a patient withanti-LGI1 encephalitis with a predominant long-term psychiatric presentation. An atypical presentation (such as atypical psychiatric symptoms, neurocognitive disorder, and hyponatremia) should prompt further investigations such as CSF analysis, considering that MRI and EEG may be normal. FDG-PET might be of interest but few data are available in the literature. Early treatment of anti-LGI1 encephalitis is crucial for overall prognosis and may delay the development of dementia in some cases.

3.
Dalton Trans ; 52(21): 7302-7310, 2023 May 30.
Artigo em Inglês | MEDLINE | ID: mdl-37170882

RESUMO

Metallic lithium (Li) is considered as one of the highly interesting anode materials for advanced batteries due to its large theoretical capacity, small material density and the high cell voltages that can be obtained in batteries using Li anodes. However, Li dendrite growth and unstable solid electrolyte interphase (SEI) formation emerged during the plating-stripping process, leading to low coulombic efficiency, rapid battery degradation and serious safety issues. These disadvantages form the major challenges towards commercialization. In this work, an ultra-thin and uniform Y2O3 layer is coated on Li metal anodes by atomic layer deposition (ALD) for improving the stability of Li metal batteries. Elucidation by in vacuo X-ray photoelectron spectroscopy (XPS) revealed different growth of a Y2O3 layer on metallic Li compared to that on a silicon wafer, which is traditionally used for ALD processes. The Y-precursor, i.e., Y(EtCp)2(iPr-amd), firstly reacts with metallic Li and forms a "decomposition" layer, leading to nonlinear growth at the preliminary stage (up to around 20 ALD cycles). Only after the bare Li surface has been fully covered does standard ALD growth start. The ALD Y2O3 layer on metallic Li is able to effectively prevent the growth of Li dendrites, giving rise to an even plating-stripping process in symmetric Li metal cells with more stable performance and prolonged lifespan. Improved electrochemical performance through the Y2O3 protective layer has also been investigated in Y2O3-coated Li||LiMn2O4 asymmetrical full cells. This work indicates that ALD Y2O3 coating is an attractive method to stabilize Li metal anodes for battery devices.

4.
Mult Scler ; 29(1): 11-36, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36317497

RESUMO

OBJECTIVE: The objective of this study was to develop evidence-based recommendations on pregnancy management for persons with multiple sclerosis (MS). BACKGROUND: MS typically affects young women in their childbearing years. Increasing evidence is available to inform questions raised by MS patients and health professionals about pregnancy issues. METHODS: The French Group for Recommendations in Multiple Sclerosis (France4MS) reviewed PubMed and university databases (January 1975 through June 2021). The RAND/UCLA appropriateness method was developed to synthesise the scientific literature and expert opinions on healthcare topics; it was used to reach a formal agreement. Fifty-six MS experts worked on the full-text review and initial wording of recommendations. A group of 62 multidisciplinary healthcare specialists validated the final proposal of summarised evidence. RESULTS: A strong agreement was reached for all 104 proposed recommendations. They cover diverse topics, such as pregnancy planning, follow-up during pregnancy and postpartum, delivery routes, locoregional analgesia or anaesthesia, prevention of postpartum relapses, breastfeeding, vaccinations, reproductive assistance, management of relapses and disease-modifying treatments. CONCLUSION: The 2022 recommendations of the French MS society should be helpful to harmonise counselling and treatment practice for pregnancy in persons with MS, allowing for better and individualised choices.


Assuntos
Esclerose Múltipla , Complicações na Gravidez , Gravidez , Humanos , Feminino , Esclerose Múltipla/terapia , Período Pós-Parto , Vacinação , Complicações na Gravidez/terapia , Recidiva
5.
Mult Scler ; 29(1): 37-51, 2023 01.
Artigo em Inglês | MEDLINE | ID: mdl-36345839

RESUMO

BACKGROUND: In 2020, the French Multiple Sclerosis (MS) Society (SFSEP) decided to develop a national evidence-based consensus on pregnancy in MS. As neuromyelitis optica spectrum disorders (NMOSD) shares a series of commonalities with MS, but also some significant differences, specific recommendations had to be developed. OBJECTIVES: To establish recommendations on pregnancy in women with NMOSD. METHODS: The French Group for Recommendations in Multiple Sclerosis (France4MS) reviewed PubMed and universities databases (January 1975 through June 2021). The RAND/UCLA appropriateness method, which was developed to synthesise the scientific literature and expert opinions on health care topics, was used to reach a formal agreement. Fifty-six MS experts worked on the full-text review and initial wording of recommendations. A sub-group of nine NMOSD experts was dedicated to analysing available data on NMOSD. A group of 62 multidisciplinary healthcare specialists validated the final proposal of summarised evidence. RESULTS: A strong agreement was reached for all 66 proposed recommendations. They cover diverse topics, such as pregnancy planning, follow-up during pregnancy and postpartum, delivery routes, loco-regional analgesia or anaesthesia, prevention of postpartum relapses, breastfeeding, vaccinations, reproductive assistance, management of relapses, and disease-modifying treatments. CONCLUSION: Physicians and patients should be aware of the new and specific evidence-based recommendations of the French MS Society for pregnancy in women with NMOSD. They should help harmonise counselling and treatment practise, allowing for better individualised choices.


Assuntos
Esclerose Múltipla , Neuromielite Óptica , Gravidez , Humanos , Feminino , Neuromielite Óptica/diagnóstico , Neuromielite Óptica/terapia , Esclerose Múltipla/diagnóstico , Esclerose Múltipla/terapia , Vacinação , Período Pós-Parto , Recidiva
6.
J Neuroinflammation ; 19(1): 62, 2022 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-35236386

RESUMO

BACKGROUND: Neuromyelitis optica spectrum disorder (NMOSD) attacks require an urgent probabilistic anti-inflammatory therapeutic strategy. As inadequately treated attacks result in disability, there is a need to identify the optimal attack-treatment regimen. Our study aimed to identify predictors of outcome after a first attack in patients with an NMOSD presentation and propose the best treatment strategy. METHODS: We performed a retrospective cohort study on the French national NMOSD registry (NOMADMUS), a nested cohort of the French multiple sclerosis observatory (OFSEP) recruiting patients with NMOSD presentations in France. We studied the first attack for any independent locations of clinical core characteristic of NMOSD, in treatment-naïve patients. The primary outcome was the evolution of the Expanded Disability Status Scale (EDSS) score at 6 months, stratified in two ways to account for recovery (return to baseline EDSS score) and treatment response (classified as "good" if the EDSS score decreased by ≥ 1 point after a nadir EDSS score ≤ 3, or by ≥ 2 points after a nadir EDSS score > 3). We used ordinal logistic regression to infer statistical associations with the outcome. RESULTS: We included 211 attacks among 183 patients (104 with anti-AQP4 antibodies, 60 with anti-MOG antibodies, and 19 double seronegative). Attack treatment regimens comprised corticosteroids (n = 196), plasma exchanges (PE; n = 72) and intravenous immunoglobulins (n = 6). Complete recovery was reached in 40 attacks (19%) at 6 months. The treatment response was "good" in 134 attacks (63.5%). There was no improvement in EDSS score in 50 attacks (23.7%). MOG-antibody seropositivity and short delays to PE were significantly and independently associated with better recovery and treatment response. CONCLUSIONS: We identified two prognostic factors: serostatus (with better outcomes among MOG-Ab-positive patients) and the delay to PE. We, therefore, argue for a more aggressive anti-inflammatory management of the first attacks suggesting an NMOSD presentation, with the early combination of PE with corticosteroids.


Assuntos
Esclerose Múltipla , Neuromielite Óptica , Aquaporina 4 , Autoanticorpos , Estudos de Coortes , Humanos , Neuromielite Óptica/tratamento farmacológico , Estudos Retrospectivos
7.
Soft Matter ; 17(48): 10873-10890, 2021 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-34807216

RESUMO

Zwitterionic polymers are very promising candidates for antifouling materials that exhibit high chemical stability as compared to polyethylene glycol-based systems. A number of simulation and experimental studies have emerged over recent years for the investigation of sulfobetaine-based zwitterionic polymers. Investigating the structural and thermodynamic properties of such polymers requires access to broad time and length regimes, thus necessitating the development of multiscale simulation strategies. The present article advocates a mesoscopic dissipative particle dynamics (DPD) model capable of addressing a wide range of time and length scales. The mesoscopic force field was developed hand-in-hand with atomistic simulations based on the OPLS force field through a bottom-up parameterization procedure that matches the atomistically calculated strand-length, strand-angle and pair distribution functions. The DPD model is validated against atomistic simulations conducted in this work, and against relevant atomistic simulation studies, theoretical predictions and experimental correlations from the literature. Properties examined include the conformations of SPE polymers in dilute bulk aqueous solution, the density profile and thickness of brush arrays as functions of the grafting density and chain length. In addition, we compute the potential of mean force of an approaching hydrophilic or hydrophobic foulant via umbrella sampling as a function of its position relative to the poly-zwitterion-covered surface. The aforementioned observables lead to important insights regarding the conformational tendencies of grafted polyzwitterions and their antifouling properties.

9.
Epilepsia Open ; 6(3): 513-527, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-35138694

RESUMO

OBJECTIVE: Epilepsy is highly prevalent in onchocerciasis-endemic African regions. Various types of epilepsy have been described in such regions based essentially on clinical characteristics. METHODS: We conducted a clinical, neurophysiological and neuropsychological study of epilepsy in the onchocerciasis-endemic region of Ntui, Sanaga-Mbam area, Cameroon. RESULTS: One hundred and eighty-seven persons with presumed epilepsy were recruited in an epilepsy clinic in Ntui. Epilepsy was clinically confirmed in 144 (79%) subjects, 69 (46.0%) of them met the onchocerciasis-associated epilepsy (OAE) criteria, and 51 of 106 tested (48.1%) presented Ov16 antibodies. Electroencephalograms (EEG) were recorded in 91 participants, of which 36 (33%) were considered abnormal and 27 of 36 (75%) revealed bifrontotemporal spike and slow waves. Concerning the neuropsychological evaluation, 29% showed severe global cognitive impairment, 28% severe episodic memory impairment, and 66% severe frontal cognitive impairment. Half of the persons with epilepsy (PWE) suffered from a mental disorder. SIGNIFICANCE: In PWE in the Sanaga-Mbam area in Cameroon, we observed EEG patterns similar to those described among persons with OAE, including nodding syndrome in other onchocerciasis-endemic areas. Most PWE presented with severe cognitive impairment. We hypothesize that onchocerciasis may induce neurocognitive disorders and epilepsy via a mechanism that involves mainly the frontal and temporal regions of the brain.


Assuntos
Epilepsia , Síndrome do Cabeceio , Oncocercose , Camarões/epidemiologia , Eletroencefalografia , Epilepsia/epidemiologia , Humanos , Oncocercose/complicações , Oncocercose/epidemiologia
11.
J Viral Hepat ; 26(11): 1330-1333, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31319008

RESUMO

Since mid-2016, Europe has been facing a major hepatitis A epidemic, with more than 25 000 cases reported to the European CDC, in 2018. We describe herein a rare case of invasive HAV meningoencephalitis as a prodrome of the classic hepatitis, which largely explains a delay in diagnosis.


Assuntos
Hepatite A/diagnóstico , Meningoencefalite/diagnóstico , Adulto , Biomarcadores , Diagnóstico Tardio , Diagnóstico Diferencial , Feminino , Hepatite A/epidemiologia , Humanos , Testes de Função Hepática , Imageamento por Ressonância Magnética , Masculino , Meningoencefalite/epidemiologia , Neuroimagem/métodos , Avaliação de Sintomas
13.
PLoS One ; 12(5): e0178111, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28542571

RESUMO

Identifying yield and grain plumpness QTL that are independent of developmental variation or phenology is of paramount importance for developing widely adapted and stable varieties through the application of marker assisted selection. The current study was designed to dissect the genetic basis of yield performance and grain plumpness in southern Australia using three doubled haploid (DH) populations developed from crosses between adapted parents that are similar in maturity and overall plant development. Three interconnected genetic populations, Commander x Fleet (CF), Commander x WI4304 (CW), and Fleet x WI4304 (FW) developed from crossing of Australian elite barley genotypes, were used to map QTL controlling yield and grain plumpness. QTL for grain plumpness and yield were analysed using genetic linkage maps made of genotyping-by-sequencing markers and major phenology genes, and field trials at three drought prone environments for two growing seasons. Seventeen QTL were detected for grain plumpness. Eighteen yield QTL explaining from 1.2% to 25.0% of the phenotypic variation were found across populations and environments. Significant QTL x environment interaction was observed for all grain plumpness and yield QTL, except QPlum.FW-4H.1 and QYld.FW-2H.1. Unlike previous yield QTL studies in barley, none of the major developmental genes, including Ppd-H1, Vrn-H1, Vrn-H2 and Vrn-H3, that drive barley adaption significantly affected grain plumpness and yield here. Twenty-two QTL controlled yield or grain plumpness independently of known maturity QTL or genes. Adjustment for maturity effects through co-variance analysis had no major effect on these yield QTL indicating that they control yield per se.


Assuntos
Grão Comestível/crescimento & desenvolvimento , Grão Comestível/genética , Hordeum/crescimento & desenvolvimento , Hordeum/genética , Chuva , Austrália , Mapeamento Cromossômico , Secas , Ligação Genética , Fenótipo , Proteínas de Plantas/genética , Polimorfismo de Nucleotídeo Único , Locos de Características Quantitativas
14.
Food Chem ; 141(4): 4349-57, 2013 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-23993625

RESUMO

Anthocyanins are the main grape pigments. Due to their aromatic cyclic arrangements, they are able to absorb the radiation in the low energy range of the visible spectrum. In the fruit of Vitis vinifera L., the five main anthocyanidins (cyanidin, peonidin, delphinidin, petunidin and malvidin) are present as 3-O-glucosides, as well as their acetyl, p-coumaroyl and caffeoyl ester forms. Despite the huge number of experimental studies dedicated to the anthocyanin profile analysis of grapes and wines, the complete theoretical elucidation of the optical properties of grape anthocyanins is missing. The present work carried out this task through quantum chemistry calculations based on time-dependent density functional theory (TD-DFT), compared to experimental spectra. The differences in visible absorption spectra between the most common grape anthocyanins were rationalized according to B-ring substitution, glucosylation and esterification. A particular attention was given to the intra-molecular copigmentation effect, demonstrating the existence of an intra-molecular charge transfer excited state for the p-coumaroyl and caffeoyl ester forms.


Assuntos
Antocianinas/química , Extratos Vegetais/química , Vitis/química , Cor , Frutas/química , Estrutura Molecular , Espectrofotometria
15.
J Phys Chem Lett ; 3(17): 2374-8, 2012 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-26292117

RESUMO

Quantum-chemical techniques are applied to assess the electronic structure at donor/acceptor heterojunctions of interest for organic solar cells. We show that electrostatic effects at the interface of model 1D stacks profoundly modify the energy landscape explored by charge carriers in the photoconversion process and that these can be tuned by chemical design. When fullerene C60 molecules are used as acceptors and unsubstituted oligothiophenes or pentacene are used as donors, the uncompensated quadrupolar electric field at the interface provides the driving force for splitting of the charge-transfer states into free charges. This quadrupolar field can be either enhanced by switching from a C60 to a perylene-tetracarboxylic-dianhydride (PTCDA) acceptor or suppressed by grafting electron-withdrawing groups on the donor.

16.
J Phys Chem B ; 114(19): 6500-12, 2010 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-20420407

RESUMO

A density functional theory (DFT) study of the one- and two-photon absorption and circular dichroism spectra of (l)-tryptophan in water is presented. The effects on the simulated spectra of conformational averaging, of solvent as described by the polarizable continuum model (PCM), and of the choice of exchange-correlation (XC) functional are analyzed. Conformational Maxwell-Boltzmann (MB) averaging is carried out at room temperature in the gas phase using the ten lowest-energy conformers in the gas phase, whereas in the solvent, the nine lowest zwitterionic conformers are determined in combination with a PCM continuum model and employed in the calculations. One- and two-photon absorption and circular dichroism spectra are calculated using time-dependent DFT with both the B3LYP and CAM-B3LYP XC functionals, including the 15 lowest excited electronic states in each case. The spectra are shown to be strongly influenced by all parameters of our computational models. Changing the XC functional yields large changes not only in the excitation energies but also in the transition dipole moments and the rotational strengths of each excited state. The inclusion of the effect of water solvation also yields different response properties for each excited state, as well as different ground-state equilibrium geometries for the gas and solvated phases. MB weights change significantly from the gas to the solvated phase, making the effect of conformational averaging strongly phase dependent. The study of all these effects highlights the importance of an accurate and reliable treatment of both ground and excited states when aiming at predicting experimental one- or two-photon spectra. However, the comparison between the MB weighted spectra and experiment for the linear spectroscopies turns out to be rather satisfactory, showing that our approach can yield at least information on the major features of the spectra.


Assuntos
Dicroísmo Circular , Fótons , Triptofano/química , Absorção , Gases/química , Teoria Quântica , Solventes/química
17.
Phys Chem Chem Phys ; 11(22): 4465-70, 2009 Jun 14.
Artigo em Inglês | MEDLINE | ID: mdl-19475164

RESUMO

A simple diagnostic test based on orbital overlap [M. J. G. Peach et al., J. Chem. Phys., 2008, 128, 044118] may be used to help judge the reliability of excitation energies in time-dependent density functional theory (TDDFT) when using generalized gradient approximation (GGA) and hybrid functionals. Orbital plots are used to illustrate the test for a model tripeptide and for 4-(N,N-dimethylamino)benzonitrile, which are representative of systems containing low- and high-overlap charge-transfer excitations. The scheme is then applied to a series of triazene chromophores in solvent, highlighting the relationship between overlap and oscillator strength and its implications for theoretical absorption spectra. No low-overlap excitations are observed with a hybrid functional; a single one is identified using a GGA. To assess the diagnostic test and to judge functional performance, gas phase triazene TDDFT excitations are compared with correlated ab initio values. The diagnostic test correctly identifies two low-overlap problematic GGA excitations. However, it does not identify another problematic excitation where the electron is excited to a spatially extended orbital, which necessarily has reasonable overlap with the occupied orbital; an improved diagnostic quantity is required for such cases. The best agreement between TDDFT and correlated ab initio excitations is obtained using a Coulomb-attenuated functional; the errors are significantly smaller than from the GGA and hybrid functionals. The study provides further support for the high quality excitations from Coulomb-attenuated functionals, negating the need for diagnostic tests.


Assuntos
Nitrilas/química , Peptídeos/química , Teoria Quântica , Triazenos/química , Gases/química , Modelos Moleculares , Estrutura Molecular , Solventes/química , Fatores de Tempo
18.
J Chem Phys ; 130(13): 134715, 2009 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-19355772

RESUMO

Electrostatic interaction schemes have been applied to predict the evolution of the polarizability in Si(n) clusters of increasing size (n=3-19). Both on-site polarization and charge transfer effects have been included in the interaction scheme, of which the values have been compared to B3LYP/6-311G(*) and other first principles results. To reproduce the pattern of the variation of the B3LYP average polarizability per Si atom as a function of the cluster size, the atomic polarizability employed in the interaction scheme should amount to roughly 80% of the bulk atomic polarizability. However, this results in a systematic underestimation of the polarizability per Si atom by about 25%, whereas increasing the atomic polarizability value leads to excessive variations of the polarizability per Si with the cluster size. An improved agreement is obtained when incorporating a charge transfer contribution, at least for sufficiently large clusters, substantiating the fact that in large clusters electrostatic effects are dominant over quantum effects. This charge transfer atomic polarizability term has been modeled by a simple function, which evolves linearly with the difference of Cartesian coordinates between the atom and the center of mass and that has been verified using B3LYP/6-311G(*) calculations. In the case of the prediction of the polarizability anisotropy, a similar atomic polarizability corresponding to 80% of the bulk atomic polarizability has been shown suitable to reproduce the B3LYP results, whereas inclusion of charge transfer effects can slightly improve the agreement, provided the amount of charge transfer increases with the size of the cluster.

19.
Phys Chem Chem Phys ; 10(41): 6223-32, 2008 Nov 07.
Artigo em Inglês | MEDLINE | ID: mdl-18936845

RESUMO

Time-dependent Hartree-Fock and Møller-Plesset second-order calculations have been used to unravel the relationships between structure and first hyperpolarizability in spiropyran/merocyanine couples and therefore to design efficient second-order nonlinear optical switching compounds. Large first hyperpolarizabilities for the merocyanine form as well as large contrasts of first hyperpolarizability have been obtained when, on the same species, (i) substituents at R(1) and R(2) positions on the phenolate ring of the merocyanine form are strong acceptor and donor substituents, respectively, (ii) the ethylenic bridge is substituted by donor groups, (iii) the other aromatic part of the system is benzimidazolo rather than indolino or benzothiazolo, and (iv) strong donor substituents are placed on the benzimidazolo moiety.


Assuntos
Benzopiranos/química , Indóis/química , Nitrocompostos/química , Dinâmica não Linear , Pirimidinonas/química , Benzimidazóis/química , Etilenos/química , Cinética , Modelos Químicos , Modelos Moleculares , Conformação Molecular , Estrutura Molecular , Teoria Quântica , Relação Estrutura-Atividade
20.
J Phys Chem A ; 111(39): 9914-23, 2007 Oct 04.
Artigo em Inglês | MEDLINE | ID: mdl-17824597

RESUMO

The keto-enol (K-E) tautomerization equilibrium, more precisely, the keto-amine/enol-imine equilibrium, has been investigated for a series of substituted salicylideneanilines in view of designing compounds with a contrast of second-order nonlinear optical properties. Substituting the salicylidene ring by an acceptor group or the other ring by a donor prevents the K form from being stable, whereas in the other cases, the K form can easily be converted to the E form due to the small activation barrier, figuring out in most cases that the K form is metastable. For a representative set of donor/acceptor substituents, the E and K forms present a sufficiently large contrast of beta to allow its detection by using electric-field-induced second harmonic generation or hyper-Rayleigh scattering. The largest beta values are mainly associated with species bearing a donor in the para position of the salicylidene ring and an acceptor on the other ring whereas the largest beta values are generally found for the E form.


Assuntos
Compostos de Anilina/química , Bases de Schiff/química , Físico-Química/métodos , Modelos Químicos , Modelos Estatísticos , Conformação Molecular , Estrutura Molecular , Óptica e Fotônica , Software , Temperatura , Termodinâmica
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