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Characterization and thermodynamic study of ultra-fine particle of Ni-B amorphous alloy

Ultra-fine particle of Ni-B amorphous alloy was prepared by chemical reduction of Ni2+ with NaBH4 and characterized with TEM and XRD. The heat capacity and thermal stability were measured with a high-precision automatic adiabatic calorimeter and DTA. The upper limit of applied temperature of the substance was found to be 684 K for use as catalyst. (C) 1999 Elsevier Science B.V. All rights reserved.

Determination of heavy metal ions by capillary electrophoresis with contactless conductivity detection after field-amplified sample injection

A method has been developed for determining of heavy metal ions by field-amplified sample injection capillary electrophoresis with contactless conductivity detection. The effects of the 2-N-morpholinoethanesulfonic acid/histidine (MES/His) concentration in the sample matrix, the injection time and organic additives on the enrichment factor were studied. The results showed that MES/His with a low concentration in the sample matrix, an increase of the injection time and the addition of acetonitrile improved the enrichment factor. Four heavy metal ions (Zn2+, Co2+, Cu2+ and Ni2+) were dissolved in deionized water, separated in a 10 mM MES/His running buffer at pH 4.9 and detected by contactless conductivity detection. The detection sensitivity was enhanced by about three orders of magnitude with respect to the non-stacking injection mode. The limits of detection were in the range from 5 nM (Zn2+) to 30 nM (Cu2+). The method has been used to determine heavy metal ions in tap water.

Cyclic voltammetry and spectroelectrochemical study of nickel and cobalt diphenyltetraazaannulene complexes

The absorption spectra. cyclic voltammetry and spectroelectrochemistry of [Ni(II)DPTAA] and [Co(II)DPTAA] (DPTAA = 6,13-diphenyldibenzo[b,i][1,4,8,11] tetraaza[14]annulene) complexes in DMF are reported in detail. The ligand oxidation is observed for [Ni(II)DPTAA] at +0.70 V vs. SCE whereas Ni2(+/+) occurs at - 1.60 V. For [Co(II)DPTAA], a ligand oxidation redox couple is seen at +0.56 V while the Co2+/+ and Co2+/3+ redox couples appear at -1.21 and +0.24 V, respectively. All observed redox couples are assigned to reversible one-electron processes on account of peak separations and scan-rate dependency. These processes were further investigated by spectroelectrochemistry for [Co(II)DPTAA]. For [Co(II)DPTAA], axial ligation of pyridine was found to shift the Co2+/3+ redox couple more negative. while the ligand oxidation was shifted to more positive potentials. From a spectrophotometric titration of [Co(II)DPTAA] with pyridine an equilibrium constant, K-f, was determined for the binding of pyridine to [Co(II)DPTAA]. This was found to be 10.2 dm(3) mol(-1), slightly lower than that of [Co(II)TAA], indicating the influence of the phenyl groups. From this value and shifts in the Co2+/3+ redox couple upon ligation, an equilibrium constant for the binding of pyridine to [Co(III)DPTAA], K'(f), was found to be 5.06 x 10(6) dm(3) mol(-1). (c) 2007 Elsevier B.V. All rights reserved.

Calcium currents in interstitial cells from the guinea-pig bladder.

OBJECTIVE: To determine whether there are inward currents in interstitial cells (IC) isolated from the guinea-pig detrusor and if so, to characterise them using the patch-clamp technique and pharmacological agents. MATERIALS AND METHODS: Using the whole-cell patch-clamp technique, inward currents were studied in IC enzymatically isolated from the detrusor of the guinea-pig bladder. Currents were evoked by stepping positively from a holding potential of - 80 mV. RESULTS: Outward K+ currents were blocked by Cs+ internal solution to reveal inward currents, which activated at voltages more positive than - 50 mV, peaked at 0 mV, reversed near + 50 mV and were half-maximally activated at - 27 mV. The inward currents showed voltage-dependent inactivation and were half-maximally inactivated at - 36 mV. Fitting the activation and inactivation data with a Boltzmann function revealed a window current between - 40 mV and + 20 mV. The decay of the current evoked at 0 mV could be fitted with a single exponential with a mean time-constant of 88 ms. Replacing external Ca2+ with Ba2+ significantly increased this to 344 ms. The current amplitude was augmented by Ba2+, and by Bay K 8644. Inward currents were significantly reduced by 1 microm nifedipine, across the voltage range, but the blockade was more effective on the current evoked at 0 mV than that evoked by a step to - 20 mV, perhaps indicating voltage-dependence of the action of nifedipine or another component of inward current. Increasing the concentration of the drug to 10 microm caused no further significant reduction either at 0 mV or at -20 mV. However, in the presence of 1 microm nifedipine the latter current was significantly reduced by 100 microm Ni2+. Both currents were significantly reduced in Ca2+-free solution. CONCLUSIONS: IC from the guinea-pig detrusor possess inward currents with typical characteristics of L-type Ca2+ current. They also have a component of inward Ca2+ current, which was resistant to nifedipine, but sensitive to Ni2+. Further work is needed to characterise the latter conductance. PMID: 16686735 [PubMed - indexed for MEDLINE]

Reactivity of ammonium chloride/mercuric chloride mixtures with monel containers. The new compounds (NH4)(2)(NH3)(x)[Ni(NH3)(2)Cl-4] and (NH4)(5)Cl-2[CuCl2][CuCl4]

Ammonium chloride/mercuric chloride mixtures (molar ratio 2: 1) react at 350degreesC with Monel (Cu68Ni32) to yield (NH4)NiCl3 and mercury and copper amalgam, respectively. With larger amounts of (NH4)Cl in the reaction mixture, dark green (NH4)(2)(NH3)(x)[Ni(NH3)(2)Cl-4] (x approximate to 0.77) (1) is also formed as a main product. Light blue crystals of the mixed-valent copper(I,II) chloride (NH4)(5)Cl-5[CuCl2][CuCl4] (2) were obtained as a minor byproduct from a 4:1 reaction mixture. The crystal structures were determined from single crystal X-ray data; (1): tetragonal, I4/mmm, a = 770.9(1), e = 794.2(2) pm, 190 reflections, R-1 = 0.0263; (2): tetragonal, I4/mcm, a = 874.8(1), c = 2329.2(3) pm, 451 reflections, R-1 = 0.0736. In (1) Ni2+ resides in trans-[Ni(NH3)(2)Cl-4](2-) octahedra, and in (2) copper(l) is linearly two-coordinated in ECUC121- and copper(II) resides in a flattened tetrahedron [CuCl4](2-) with a tetrahedricity of 89%. (C) 2001 Elsevier Science.

Adsorption of metal ions on nitrogen surface functional groups in activated carbons

<p>A commercially available coconut-shell-derived active carbon was oxidized with nitric acid, and both the original and oxidized active carbons were treated with ammonia at 1073 K to incorporate nitrogen functional groups into the carbon. An active carbon with very high nitrogen content (similar to9.4 wt % daf) was also prepared from a nitrogen-rich precursor, polyacrylonitrile (PAN). These nitrogen-rich carbons had points of zero charge (pH(pzc)) similar to H-type active carbons. X-ray absorption near-edge structure (XANES) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, and temperature-programmed desorption (TPD) were used to characterize the nitrogen functional groups in the carbons. The nitrogen functional groups present on the carbon surface were pyridinic, pyrrolic (or indolic), and pyridonic structures. The adsorption of transition metal cations Cd2+, Ni2+, and Cu2+ from aqueous solution on the suite of active carbons showed that adsorption was markedly higher for carbons with nitrogen functional groups present on the surface than for carbons with similar pH(pzc) values. In contrast, the adsorption characteristics of Ca2+ from aqueous solution were similar for all the carbons studied. Flow microcalorimetry (FMC) studies showed that the enthalpies of adsorption of Cd2+(aq) on the active carbons with high nitrogen contents were much higher than for nitric acid oxidized carbons studied previously, which also had enhanced adsorption characteristics for metal ion species. The enthalpies of adsorption of Cu2+ were similar to those obtained for Cd2+ for specific active carbons. The nitrogen functional groups in the carbons act as surface coordination sites for the adsorption of transition metal ions from aqueous solution. The adsorption characteristics of these carbons are compared with those of oxidized carbons.</p>

T- and L-type Ca2+ currents in freshly dispersed smooth muscle cells from the human proximal urethra

<p>The purpose of the present study was to characterise Ca2+ currents in smooth muscle cells isolated from biopsy samples taken from the proximal urethra of patients undergoing surgery for bladder or prostate cancer. Cells were studied at 37 degreesC using the amphotericin B perforated-patch configuration of the patch-clamp technique. Currents were recorded using Cs+-rich pipette solutions to block K+ currents. Two components of current, with electrophysiological and pharmacological properties typical of T- and L-type Ca2+ currents, were present in these cells. When steady-state inactivation curves for the L current were fitted with a Boltzmann equation, this yielded a V-1/2 of -45 +/- 5 mV. In contrast, the T current inactivated with a V-1/2 of -80 +/- 3 mV. The L currents were reduced in a concentration-dependent manner by nifedipine (ED50 = 159 +/- 54 nm) and Ni2+ (ED50 = 65 +/- 16 muM) but were enhanced when external Ca2+ was substituted with Ba2+. The T current was little affected by TTX, reduction in external Na+, application of nifedipine at concentrations below 300 nm or substitution of external Ca2+ with Ba2+, but was reduced by Ni2+ with an ED50 of 6 +/- 1 mum. When cells were stepped from -100 to -30 mV in Ca2+-free conditions, small inward currents could be detected. These were enhanced 40-fold in divalent-cation-free solution and blocked in a concentration-dependent manner by Mg2+ with an ED50 of 32 +/- 16 mum. These data support the idea that human urethral myocytes possess currents with electrophysiological and pharmacological properties typical of T- and L-type Ca2+ currents.</p>

Valoriza����o de res��duos industriais na formula����o de produtos e pigmentos cer��micos: processamento e desenvolvimento de cor

A valoriza����o de diferentes res��duos industriais provenientes dosector de tratamento/revestimento de superf��cies met��licas pode ser obtida utilizando-os como mat��rias-primas na formula����o de pigmentos cer��micos, sintetizados pelo m��todo cer��mico convencional. Neste trabalho avaliou-se a viabilidade de incorporar lamas geradas pelos processos de (i) anodiza����o, ricas em alum��nio, (ii) de niquelagem e cromagem de torneiras, usadas como fonte de n��quel e cr��mio, e (iii) da decapagem qu��mica de a��os de uma trefilaria, ricas em ferro, utilizadas por si s��, ou em conjunto com mat��rias-primas comerciais, para a obten����o depigmentos cer��micos que coram, de forma est��vel, diversas matrizes cer��micas e v��treas. Esta solu����o assegura ainda a inertiza����o de potenciaisesp��cies perigosas presentes nos res��duos, resultando produtos in��cuospara a sa��de p��blica. Procedeu-se �� caracteriza����o de cada res��duo, em termos de composi����o qu��mica e mineral��gica, comportamento t��rmico, grau de toxicidade, distribui����o granulom��trica, teor de humidade, etc. Verificou-se a const��ncia das caracter��sticas das lamas, recorrendo �� an��lise de lotes recolhidos em momentos distintos. Os res��duos s��o essencialmente constitu��dos por hidr��xidos met��licos e foram utilizados ap��s secagem e desagrega����o. No entanto, a lama de anodiza����o de alum��nio sofreu um tratamento t��rmico suplementar a 1400��C. O m��todo de s��ntese dos pigmentos englobou as seguintes etapas: (i) doseamento; (ii) homogeneiza����o; (iii) calcina����o; (iv) lavagem e moagem.Procedeu-se �� caracteriza����o dos pigmentos, avaliando a cor por espectroscopia de reflect��ncia difusae pelo m��todo CIELAB e determinando as caracter��sticas f��sico-qu��micas relevantes. Posteriormente, testou-se o seu desempenho em produtos cer��micos distintos (corpos e vidrados), aferindo o desempenho crom��tico e a estabilidade. Numa primeira fase, desenvolveram-se e caracterizaram-se tipos distintos de pigmentos: (i) com base na estrutura do corundo (ii) verde Vict��ria deuvarovite (iii) violeta de cassiterite com cr��mio (iv) pigmento carmim de malaia��te; (v)pretos e castanhos com base na estrutura da espinela. Aprofundaram-se depois os estudos do pigmento carmim de malaia��tee do pigmento preto com base na estrutura da espinela. O pigmento carmim de malaia��te, CaSnSiO5:Cr2O3, �� formulado coma lama gerada no processo de niquelagem e cromagem. Avaliou-se a influ��ncia do teor de lama na temperatura de s��ntese e na qualidade crom��tica, em compara����o com um pigmento formulado com reagentes puros. O pigmento preto com estrutura de espinela de n��quel, cr��mio e ferro, foii formulado exclusivamente a partir das lamas geradas nos processos de cromagem/niquelagem e de decapagem qu��mica do a��o. Avaliaram-se as caracter��sticas crom��ticas e o grau de inertiza����o dos elementos t��xicospresentes, em fun����o da estequiometria e do tratamento t��rmico. Estudou-se ainda um novo sistema com base na estrutura da hibonite(CaAl12O19), que permite a obten����o de pigmentos azuis e que utiliza a lama de cromagem e niquelagem. As esp��cies crom��foras (Ni2+ ou Co2+) assumem coordena����o tetra��drica quando substituem os i��es Al3+ que ocupam as posi����es M5 da rede da hibonite. A forma����o simult��nea de anortite permite reduzir a temperatura de s��ntese.Para al��m do car��cter inovador deste pigmento de dissolu����o s��lida, a qualidade crom��tica e a sua estabilidade s��o interessantes. Al��m disso, os teores de cobalto ou n��quel s��o reduzidosrelativamente aos utilizados em formula����es comerciais de pigmentos azuis, o que se traduz em importantes vantagens econ��micas e ambientais.

Estudo de receptores sint��ticos no reconhecimento molecular de substratos ani��nicos e i��es met��licos

O trabalho descrito insere-se no ��mbito da Qu��mica Supramolecular e consistiu no desenvolvimento de receptores artificiais, na forma protonada ou complexada, para o reconhecimento molecular de substratos ani��nicos derivados de ��cidos carbox��licos incluindo os herbicidas PMG2-, ATCP- e 2,4-D-. Foram investigadas duas s��ries de ani��es, uma alif��tica (ox2-, mal2-, suc2-, glu2-, adip2-, cit3- e cta3-) e outra arom��tica (bzc-, naphc-, anthc-, pyrc-, ph2-, iph2-, tph2-, btc3-, dihyac2-, 4,4-dibzc2-, 3-nitrobzc- e 4-nitrobzc-). Foram sintetizados sete novos ligandos macroc��clicos sim��tricos constitu��dos por an��is arom��ticos piridina ou fenantrolina ligados por cadeias de poliaminas saturadas. O comportamento ��cido-base destes macrociclos foi investigado em solu����o aquosa e as constantes de protona����o correspondentes determinadas por m��todos potenciom��tricos e de RMN de 1H. As propriedades de complexa����o destes ligandos com os i��es met��licos Ni2+, Cu2+, Zn2+, Cd2+ e Pb2+ foram tamb��m estudadas por m��todos potenciom��tricos nas mesmas condi����es experimentais, tendo revelado que os macrociclos de dimens��o m��dia s��o capazes de acomodar um ou dois i��es met��licos. O complexo dinuclear de Cu(II) derivado do macrociclo com dois grupos piridina foi utilizado como receptor de ani��es carboxilato originando complexos tern��rios. Todos os complexos foram caracterizados em solu����o por espectroscopias de UV/vis/IVpr��x e de RMN. As esp��cies paramagn��ticas foram tamb��m caracterizadas por espectroscopia de RPE. A forma����o de esp��cies tern��rias foi ainda investigada por espectrometria de massa ESI-MS e ESI-MS/MS. As estruturas cristalinas de alguns dos complexos foram determinadas por difrac����o de raios-X. As formas protonadas dos macrociclos foram utilizadas como receptores de uma grande variedade de ani��es carboxilato. O reconhecimento molecular entre os receptores e os substratos ani��nicos foi investigado em solu����o por m��todos potenciom��tricos e de espectroscopia de RMN com determina����o das constantes de associa����o. Os agregados supramoleculares foram caracterizados no estado s��lido por difrac����o de raios-X. Finalmente as associa����es supramoleculares foram estudadas em solu����o por m��todos de din��mica molecular com determina����o dos termos entr��picos e ent��lpicos das energias livres de liga����o. Em resumo, nesta tese apresentam-se os resultados de estudos realizados com duas fam��lias de macrociclos: desde a s��ntese dos compostos, passando por estudos em solu����o e finalizando com simula����o molecular. Este estudo sistem��tico atrav��s da conjuga����o de metodologias complementares permitiu caracterizar ao n��vel macrosc��pico e microsc��pico as associa����es moleculares.

Study of multiferroic materials

The present PhD work aims the research and development of materials that exhibit multiferroic properties, in particular having a significant interaction between ferromagnetism and ferroelectricity; either directly within an intrinsic single phase or by combining extrinsic materials, achieving the coupling of properties through mechanic phenomena of the respective magnetostriction and piezoelectricity. These hybrid properties will allow the cross modification of magnetic and electric polarization states by the application of cross external magnetic and/or electric fields, giving way to a vast area for scientific investigation and potential technological applications in a new generation of electronic devices, such as computer memories, signal processing, transducers, sensors, etc. Initial experimental work consisted in chemical synthesis of nano powders oxides by urea pyrolysis method: A series of ceramic bulk composites with potential multiferroic properties comprised: of LuMnO3 with La0.7Sr0.3MnO3 and BaTiO3 with La0.7Ba0.3MnO3; and a series based on the intrinsic multiferroic LuMn1-zO3 phase modified with of Manganese vacancies. The acquisition of a new magnetron RF sputtering deposition system, in the Physics Department of Aveiro University, contributed to the proposal of an analogous experimental study in multiferroic thin films and multilayer samples. Besides the operational debut of this equipment several technical upgrades were completed like: the design and construction of the heater electrical contacts; specific shutters and supports for the magnetrons and for the substrate holder and; the addition of mass flow controllers, which allowed the introduction of N2 or O2 active atmosphere in the chamber; and the addition of a second RF generator, enabling co-deposition of different targets. Base study of the deposition conditions and resulting thin films characteristics in different substrates was made from an extensive list of targets. Particular attention was given to thin film deposition of magnetic phases La1-xSrxMnO3, La1-xBaxMnO3 and Ni2+x-yMn1-xGa1+y alloy, from the respective targets: La0.7Sr0.3MnO3, La0.7Ba0.3MnO3; and NiGa with NiMn. Main structural characterization of samples was performed by conventional and high resolution X-Ray Diffraction (XRD); chemical composition was determined by Electron Dispersion Spectroscopy (EDS); magnetization measurements recur to a Vibrating Sample Magnetometer (VSM) prototype; and surface probing (SPM) using Magnetic-Force (MFM) and Piezo-Response (PFM) Microscopy. Results clearly show that the composite bulk samples (LuM+LSM and BTO+LBM) feat the intended quality objectives in terms of phase composition and purity, having spurious contents below 0.5 %. SEM images confirm compact grain packaging and size distribution around the 50 nm scale. Electric conductivity, magnetization intensity and magneto impedance spreading response are coherent with the relative amount of magnetic phase in the sample. The existence of coupling between the functional phases is confirmed by the Magnetoelectric effect measurements of the sample ���78%LuM+22%LSM��� reaching 300% of electric response for 1 T at 100 kHz; while in the ���78%BTO+22%LBM��� sample the structural transitions of the magnetic phase at ~350 K result in a inversion of ME coefficient the behavior. A functional Magneto-Resistance measurement system was assembled from the concept stage until the, development and operational status; it enabled to test samples from 77 to 350 K, under an applied magnetic field up to 1 Tesla with 360�� horizontal rotation; this system was also designed to measure Hall effect and has the potential to be further upgraded. Under collaboration protocols established with national and international institutions, complementary courses and sample characterization studies were performed using Magneto-Resistance (MR), Magneto-Impedance (MZ) and Magneto-Electric (ME) measurements; Raman and X-ray Photoelectron Spectroscopy (XPS); SQUID and VSM magnetization; Scanning Electron Microscopy (SEM) and Rutherford Back Scattering (RBS); Scan Probe Microscopy (SPM) with Band Excitation Probe Spectroscopy (BEPS); Neutron Powder Diffraction (NPD) and Perturbed Angular Correlations (PAC). Additional collaboration in research projects outside the scope of multiferroic materials provided further experience in sample preparation and characterization techniques, namely VSM and XPS measurements were performed in cubane molecular complex compounds and enable to identify the oxidation state of the integrating cluster of Ru ions; also, XRD and EDS/SEM analysis of the acquired targets and substrates implied the devolution of some items not in conformity with the specifications. Direct cooperation with parallel research projects regarding multiferroic materials, enable the assess to supplementary samples, namely a preliminary series of nanopowder Y1-x-yCax��yMn1O3 and of Eu0.8Y0.2MnO3, a series of micropowder composites of LuMnO3 with La0.625Sr0.375MnO3 and of BaTiO3 with hexagonal ferrites; mono and polycrystalline samples of Pr1-xCaxMnO3, La1-xSrxMnO3 and La1-xCaxMnO3.

Corroles : synthesis, functionalization and application as chemosensors

O trabalho de investiga����o apresentado nesta disserta����o foi desenvolvido tendo como objectivo a s��ntese e funcionaliza����o de meso-triarilcorr��is para utiliza����o como quimiossensores. Este trabalho encontra-se apresentado ao longo de cinco cap��tulos. No primeiro cap��tulo s��o apresentadas as caracter��sticas gerais, as metodologias de s��ntese e de funcionaliza����o de macrociclos de tipo corr��lico, e descrevemse algumas aplica����es em que t��m sido utilizados. S��o ainda abordadas algumas das propriedades e caracter��sticas dos quimiossensores e os mecanismos de dete����o de diversos anal��tos. No segundo cap��tulo, ap��s uma pequena introdu����o ��s rea����es de Wittig e de Diels-Alder, escolhidas para a funcionaliza����o do macrociclo corr��lico, descreve-se o estudo efectuado para a obten����o do complexo de g��lio(III) do 3- vinil-5,10,15-tris(pentafluorofenil)corrol e o seu comportamento como dieno, em rea����es de Diels-Alder na presen��a dos dien��filos 1,4-benzoquinona e 1,4- naftoquinona. Desses estudos resultaram dois aductos cuja habilidade sensorial, bem como a dos seus precursores, foi estudada, em solu����o, na presen��a de ani��es esf��ricos (F-, Br-, Cl-), lineares (CN-) e volumosos (CH3COO-, H2PO4 -). Dos macrociclos estudados verificou-se que o corrol base-livre 5,10,15-tris(pentafluorofenil)corrol apresenta uma elevada sensibilidade para o ani��o fluoreto (F-), e que a coordena����o do n��cleo corr��lico com g��lio(III) diminui a afinidade para este ani��o. Em geral, todos os compostos mostraram afinidade para o ani��o cianeto (CN-) mesmo quando em suportes polim��ricos. O gel de poliacrilamida revelou-se muito promissor na determina����o de CN- em amostras de ��gua. No terceiro cap��tulo �� avaliada a reatividade do complexo de g��lio(III) do 3- vinil-5,10,15-tris(pentafluorofenil)corrol ainda como dieno mas agora na presen��a de um dien��filo linear, o acetilenodicarboxilato de dimetilo. Desse estudo resultaram dois novos derivados corr��licos. A habilidade sensorial dos mesmos perante os ani��es fluoreto, cianeto, acetato, e fosfato foi avaliada por espectroscopia de absor����o e emiss��o tendo um dos aductos mostrado ser colorim��trico para o ani��o cianeto. No quarto cap��tulo descreve-se a s��ntese e caracteriza����o de dois conjugados do tipo corrol-cumarina, resultantes de rea����es de Hetero-Diels-Alder entre o 3-vinil-5,10,15-tris(pentafluorofenil)corrolatog��lio(III)(piridina) e orto-quinonasmet��deos gerados in situ a partir de reac����es de Knoevenagel entre cumarinas e paraformalde��do. Realizaram-se estudos de afinidade sensorial para ani��es e cati��es com estes macrociclos, bem como com conjugados porfirinacumarina an��logos. A inser����o de uma unidade cumarina conferiu uma excepcional solubilidade tendo os novos derivados apresentado solubilidade em etanol. No quinto e ��ltimo cap��tulo desta disserta����o �� avaliada a capacidade sensorial do 5,10,15-tris(pentafluorofenil)corrol e da sua esp��cie monoani��nica, para os cati��es met��licos Na+, Ca2+, Cu2+, Cd2+, Pb2+, Hg2+, Ag+, Al3+, Zn2+, Ni2+, Cr3+, Ga3+, Fe3+ em tolueno e acetonitrilo. Os macrociclos corr��licos mostraram ser selectivos e colorim��tricos para o cati��o Hg2+. Neste trabalho descreve-se ainda a s��ntese do derivado -iminocorrol, que ap��s funcionaliza����o com o 3-isocianatopropiltrimetoxisilano originou um derivado do tipo alcoxisilano, que foi, posteriormente, ancorado a nanopart��culas comerciais de s��lica. As novas nanopart��culas ancoradas com o alcoxisilano corrol foram estudadas na presen��a de Cu2+, Hg2+ e Ag+. Na presen��a do cati��o Ag+ assistiu-se a uma mudan��a de cor, de verde para amarelo.

Calixarenos met��licos catalisadores de reac����es org��nicas industriais sustent��veis

Trabalho Final de Mestrado para obten����o do grau de Mestre em Engenharia Qu��mica e Biol��gica

Modulation of muscle contraction by a FMRFamide-related peptide

A FMRFamide-like neuropeptide with the sequence "DRNFLRF-NH2" was recently isolated from pericardial organs of crayfish (Mercier et aI., Peptides, 14, 137-143, 1993). This neuropeptide, referred to as "DF2'" has already been shown to elicit cardioexcitation and to enhance synaptic transmission at neuromuscular junctions. Possible effects ofDF2 on muscle were investigated using superficial extensor muscles of the abdomen of the crayfish, Procambarus clar/ai. These muscles are of the tonic type and generate slow contractions that affect posture. DF2, at concentrations of 10-8 M or higher, increased muscle tonus and induced spontaneous, rhythmic contractions. These effects were antagonized by 5 rnM Mn2+ but not by lO-7M tetrodotoxin (TTX). Thus, they represent direct actions on muscle cells (rather than effects on motor neurons) and are likely to involve calcium influx. In contrast, deep abdominal extensor muscles, responsible for rapid swimming movements, and superficial flexor muscles do not generate contractions in response to the peptide. 2 Spontaneous contractions were also induced in the superficial extensor muscles by decreasing the temperature to II-13��C. Such contractions were also TTX-insensitive and they were antagonized by adding calcium channel blockers (Mn2+, Cd2+ or Ni2+) or by removing calcium from the bathing solution. This suggests that the spontaneous contractions depend on an influx of calcium from the extracellular solution. N-type and L-type voltage dependent calcium channel blockers did not reduce the effect of the peptide or the spontaneous contractions suggesting that calcium influx is not through N- or L-type calcium channels.

Tetrathiafulvalene and 2,2'-Bipyridine: Bridging both Worlds in the Pursuit of Novel Molecular Materials

The preparation and characterization of two families of building blocks for molecule-based magnetic and conducting materials are described in three projects. In the first project the synthesis and characterization of three bis-imine ligands LI - L3 is reported. Coordination of LI to a series of metal salts afforded the five novel coordination complexes Sn(L4)C4 (I), [Mn(L4)(u-CI)(CI)(EtOH)h (II), [CU(L4)(u-sal) h(CI04)2 (sal = salicylaldehyde anion) (III), [Fe(Ls)2]CI (IV) and [Fe(LI)h(u-O) (V). All complexes have been structurally and magnetically characterized. X-ray diffraction studies revealed that, upon coordination to Lewis acidic metal salts, the imine bonds of LI are susceptible to nucleophilic attack. As a consequence, the coordination complexes (I) - (IV) contain either the cyclised ligand L4 or hydrolysed ligand Ls. In contrast, the dimeric Fe3+ complex (V) comprises two intact ligand LI molecules. In. this complex, the ligand chelates two Fe(III) centres in a bis-bidentate manner through the lone pairs of a phenoxy oxygen and an imine nitrogen atom. Magnetic studies of complexes (II-V) indicate that the dominant interactions between neighbouring metal centres in all of the complexes are antiferromagnetic. In the second project the synthesis and characterization two families of TTF donors, namely the cyano aryl compounds (VI) - (XI) and the his-aryl TTF derivatives (XII) - (XIV) are reported. The crystal structures of compounds (VI), (VII), (IX) and (XII) exhibit regular stacks comprising of neutral donors. The UV -Vis spectra of compounds (VI) - (XIV) present an leT band, indicative of the transfer of electron density from the TTF donors to the aryl acceptor molecules. Chemical oxidation of donors (VI), (VII), (IX) and (XII) with iodine afforded a series of CT salts that where possible have been characterized by single crystal X -ray diffraction. Structural studies showed that the radical cations in these salts are organized in stacks comprising of dimers of oxidized TTF donors. All four salts behave as semiconductors, displaying room temperature conductivities ranging from 1.852 x 10-7 to 9.620 X 10-3 Scm-I. A second series of CT salts were successfully prepared via the technique of electrocrystallization. Following this methodology, single crystals of two CT salts were obtained. The single crystal X-ray structures of both salts are isostructural, displaying stacks formed by trimers of oxidized donors. Variable temperature conductivity measurements carried out on this series of CT salts reveal they also are semiconductors with conductivities ranging from 2.94 x 10-7 to 1.960 X 10-3 S em-I at room temperature. In the third project the synthesis and characterization of a series of MII(hfac)2 coordination complexes of donor ligand (XII) where M2+ = Co2+, Cu2+, Ni2+ and Zn2+ are reported. These complexes crystallize in a head-to-tail arrangement of TTF donor and bipyridine moieties, placing the metal centres and hfac ligands are located outside the stacks. Magnetic studies of the complexes (XV) - (XVIII) indicate that the bulky hfac ligands prevent neighbouring metal centres from assembling in close proximity, and thus they are magnetically isolated.