Publications

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2009
Gago, S, Neves P, Monteiro B, Pessego M, Lopes AD, Valente AA, Paz FAA, Pillinger M, Moreira J, Silva CM, Goncalves IS.  2009.  Synthesis and Catalytic Properties in Olefin Epoxidation of Octahedral Dichloridodioxidomolybdenum(VI) Complexes Bearing N,N-Dialkylamide Ligands: Crystal Structure of Mo2O4(mu(2)-O)Cl-2(dmf)(4). European Journal of Inorganic Chemistry. :4528-4537., Number 29-30 Abstract
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Frade, RFM, Rosatella AA, Marques CS, Branco LC, Kulkarni PS, Mateus NMM, Afonso CAM, Duarte CMM.  2009.  Toxicological evaluation on human colon carcinoma cell line (CaCo-2) of ionic liquids based on imidazolium, guanidinium, ammonium, phosphonium, pyridinium and pyrrolidinium cations. Green Chemistry. 11:1660-1665., Number 10 Abstract
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2008
Sousa, MM, Melo MJ, Parola AJ, de Melo JSS, Catarino F, Pina F, Cook FEM, Simmonds MSJ, Lopes JA.  2008.  Flavylium chromophores as species markers for dragon's blood resins from Dracaena and Daemonorops trees, 2008. Journal of Chromatography A. 1209:153-161. Abstract

A simple and rapid liquid chromatographic method with diode-array UV-vis spectrophotometric detection has been developed for the authentication of dragon's blood resins from Dracaena and Daemonorops trees. Using this method it was discovered that the flavylium chromophores, which contribute to the red colour of these resins, differ among the species and could be used as markers to differentiate among species. A study of parameters, such as time of extraction, proportion of MeOH and pH, was undertaken to optimise the extraction of the flavyliums. This method was then used to make extracts from samples of dragon's blood resin obtained from material of known provenance. From the samples analysed 7,6-dihydroxy-5-methoxyflavylium (dracorhodin), 7,4'-dihydroxy-5-methoxyflavylium (dracoflavylium) and 7,4'-dihydroxyflavylium were selected as species markers for Daemonorops spp., Dracaena draco and Dracaena cinnabari, respectively. The chromatograms from these samples were used to build an HPLC-DAD database. The ability to discriminate among species of dragon's blood using the single marker compounds was compared with a principal components analysis of the chromatograms in the HPLC-DAD database. The results from the HPLC-DAD method based on the presence of these flavylium markers was unequivocal. The HPLC-DAD method was subsequently applied to 37 samples of dragon blood resins from the historical samples in the Economic Botany Collection, Royal Botanic Gardens, Kew. The method identified anomalies in how samples in this collection had been labelled. It is clear that the method can be used to evaluate the provenance of samples used in different areas of cultural heritage. It also could be used to monitor the trade of endangered species of dragon's blood and the species being used in complex formulations of traditional Chinese medicine. (C) 2008 Elsevier B.V. All rights reserved.

Vidinha, P, Lourenco NMT, Pinheiro C, Bras AR, Carvalho T, Santos-Silva T, Mukhopadhyay A, Romao MJ, Parola J, Dionisio M, Cabral JMS, Afonso CAM, Barreiros S.  2008.  Ion jelly: a tailor-made conducting material for smart electrochemical devices, 2008. Chemical Communications. :5842-5844. Abstract

We present a new concept for the design of a polymeric conducting material that combines the chemical versatility of an organic salt ( ionic liquid) with the morphological versatility of a biopolymer ( gelatin); the resulting 'ion jelly' can be applied in electrochemical devices, such as batteries, fuel cells, electrochromic windows or photovoltaic cells.

Sousa, MM, Miguel C, Rodrigues I, Parola AJ, Pina F, de Melo JSS, Melo MJ.  2008.  A photochemical study on the blue dye indigo: from solution to ancient Andean textiles, 2008. Photochemical & Photobiological Sciences. 7:1353-1359. Abstract

The degradation of indigo and its water soluble derivative indigo carmine was investigated under light excitation in the presence and absence of molecular oxygen in solution (homogeneous) and gels (heterogeneous) media. Collagen and carboxymethylcellulose (CMC) aqueous gels were chosen to simulate a natural textile environment, wool and cotton, respectively. Isatin was found to be the major degradation product of indigo. In solution, the photodegradation quantum yields (Phi(R)) were in the order of 10(-4), with the exception of aqueous media (Phi(R) = 9 x 10(-6)), and dependent on the irradiation wavelength. In the case of indigo carmine the Phi(R) values were found to suffer a 2-fold increase upon going from water to gels. The results indicate the absence of degradation products involving singlet oxygen and suggest peroxides, or other oxygen based radicals, to have a key role in the degradation of indigo. Finally, the relevance of the simulation is discussed by comparing the main degradation products to those found in the blues of millenary Andean textiles.

Sousa, MM, Melo MJ, Parola AJ, Morris PJT, Rzepa HS, de Melo JSS.  2008.  A Study in Mauve: Unveiling Perkin's Dye in Historic Samples, 2008. Chemistry-a European Journal. 14:8507-8513. Abstract

The analysis of different historic mauve samples-mauve salts and dyed textiles-was undertaken to establish the exact nature of the iconic dye produced by W.H. Perkin in the nineteenth century. Fourteen samples from important museum collections were analyzed, and it was determined that. in contrast to the general wisdom that mauveine consists of C, and C, structures. Perkin's mauveine is a complex mixture of at least thirteen methyl derivatives (C, to C(28)) with a 7-amino5-phenyl-3-(phenylamino)phenazin-5- ium core. A fingerprint was established in which mauveines A or B were dominant, and in which mauveines B2 and C(25) were found to be important tracers to probe the original synthesis. Counterion analysis showed that all the mauve salts should be dated after 1862. Perkin's original recipe could be identified in three textile samples, and in these cases, mauveines A and C25 were found to he the major chromophores. These are now shown to be the samples containing the "original mauve".

Rodriguez, L, Lima JC, Parola JA, Pina F, Meitz R, Aucejo R, Garcia-Espana E, Llinares JM, Soriano C, Alarcon J.  2008.  Anion detection by fluorescent Zn(II) complexes of functionalized polyamine ligands. Inorganic Chemistry. 47:6173-6183., Number 14 Abstract
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Sousa, MM, Melo MJ, Parola JA, Seixas de Melo SJ, Catarino F, Pina F, Cook FEM, Simmonds MSJ, Lopes JA.  2008.  Flavylium chromophores as species markers for dragon's blood resins from Dracaena and Daemonorops trees. Journal of Chromatography A. 1209:153-161., Number 1-2 Abstract
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Monteiro, B, Gago S, Paz FAA, Bilsborrow R, Goncalves IS, Pillinger M.  2008.  Investigation of layered double hydroxides intercalated by oxomolybdenum catecholate complexes. Inorganic Chemistry. 47:8674-8686., Number 19 Abstract
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Gago, S, Costa T, de Melo SJ, Goncalves IS, Pillinger M.  2008.  Preparation and photophysical characterisation of Zn-Allayered double hydroxides intercalated by anionic pyrene derivatives. Journal of Materials Chemistry. 18:894-904., Number 8 Abstract
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Nunez, C, Oliveira E, Giestas L, Valencia L, Macias A, Lima JC, Bastida R, Lodeiro C.  2008.  Synthesis, spectroscopic, structural and complexation studies of a new tetra-naphthylmethylene pendant-armed macrocyclic ligand. Inorganica Chimica Acta. 361:2183-2194., Number 8 Abstract
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Claro, A, Melo MJ, Schafer S, de Melo SSJ, Pina F, van den Berg KJ, Burnstock A.  2008.  The use of microspectrofluorimetry for the characterization of lake pigments. Talanta. 74:922-929., Number 4 Abstract
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2007
Jimenez, A, Pinheiro C, Parola AJ, Maestri M, Pina F.  2007.  The chemistry of 6-hydroxyflavylium: zwitterionic base and p-quinoidal chalcones. A multiswitchable system operated by proton, electron and photon inputs, 2007. Photochemical & Photobiological Sciences. 6:372-380. Abstract

The complex network of chemical reactions of the compound 6-hydroxyflavylium perchlorate was studied by different techniques including UV-vis absorption spectrophotometry, stopped-flow, electrochemistry, and photochemistry. The network is characterized by the formation of a very reactive zwitterionic base as well as by p-quinoidal chalcones. The trans-chalcone is metastable in very acidic solutions and exhibits reversible redox reactions, allowing to introduce for the first time in the flavylium network an electrochemical input.

Parola, AJ, Pereira P, Pina F, Maestri M.  2007.  Effect of SDS micelles on the reactivity of 4 '-methoxyflavylium ion: A stopped-flow and photochemical study, 2007. Journal of Photochemistry and Photobiology a-Chemistry. 185:383-390. Abstract

The network of chemical reactions of the compound 4'-methoxyflavylium was studied in the presence of SDS micelles, using stopped-flow, UV-vis absorption and flash photolysis techniques. The results were compared with analogous experiments carried out in water. The large stabilization of the flavylium cation onto the micelles was proven to be due to an increase in the rate of the dehydration reaction, rather than a decrease of the hydration reaction; the cis-trans isomerisation of the chalcone was not affected by the micelles. It is shown that SDS micelles can be considered as an external stimulus capable of changing the system from one state to another. (c) 2006 Elsevier B.V. All rights reserved.

Melo, MJ, Sousa M, Parola AJ, de Melo JSS, Catarino F, Marcalo J, Pina F.  2007.  Identification of 7,4 '-dihydroxy-5-methoxyflavylium in "Dragon's blood": To be or not to be an anthocyanin, 2007. Chemistry-a European Journal. 13:1417-1422. Abstract

The compound 7,4'-dihydroxy-5-methoxyflavylium (dracoflavylium) was identified as the major red colorant in samples of the resin "dragon's blood", extracted from the tree Dracaena draco. The complex network of reversible chemical reactions that dracoflavylium undergoes in aqueous solution is fully described; for the first time, all the equilibrium constants that enable a complete characterisation of the system have been obtained (K'(a)=1.6 x 10(-4), K-a1 = 1.0 x 10(-4), K-a2 = 3.2 x 10(-8), K-Ct1 = 1.0 x 10(-7), K-Ct2 = 1.3 x 10(-10)). It is concluded that the red colour is due to a stable quinoid base, A, which is the major species at pH 4-7. It is further shown that this compound does not fit the commonly accepted definitions of anthocyanidin nor 3-deoxyanthocyanidin. Similarly to synthetic flavylium salts, the natural compound 7,4'-dihydroxy-5-methoxyflavylium gives rise to several species (multistate system) reversibly interconverted by external stimuli, such as pH.

Pina, F, Parola AJ, Melo MJ, Laia CAT, Afonso CAM.  2007.  Photochromism of 7-(N, N-diethylamino) 4 '-hydroxyflavylium in a water-ionic liquid biphasic system, 2007. Chemical Communications. :1608-1610. Abstract

Photochromism of trans-4-(N,N-diethylamino)-2,4'-dihydroxychalcone, with formation of the photoproduct 7-(N,N-diethylamino)-4'-hydroxyflavylium, is promoted in the ionic liquid phase of a water/[bmim][PF6] biphasic system.

de Melo, JS, Takato S, Sousa M, Melo MJ, Parola AJ.  2007.  Revisiting Perkin's dye(s): the spectroscopy and photophysics of two new mauveine compounds (B2 and C), 2007. Chemical Communications. :2624-2626. Abstract

Two new components have been identified in an early sample prepared according to the original recipe of Perkin, and perhaps even by Perkin himself around 1860 - a new isomer of Perkin's mauveine B (designated as mauveine B2) together with a new mauveine compound (mauveine C) - and these compounds were synthesized again using starting materials chosen to reproduce Perkin's original synthesis and isolated by HPLC-DAD, identified by H-1 NMR, MS and their spectroscopic (UV/Vis and emission) and photophysical behaviour investigated.

Parola, AJ, Lima JC, Pina F, Pina J, de Melo JS, Soriano C, Garcia-Espana E, Aucejo R, Alarcon J.  2007.  Synthesis and photophysical properties of dansyl-based polyamine ligands and their Zn(II) complexes, 2007. Inorganica Chimica Acta. 360:1200-1208. Abstract

The synthesis, potentiometric studies and photophysical properties of two new polyamine ligands (L1 and L2) possessing the dansyl chromophore were studied in aqueous 0.15 M NaCl. The compounds show the absorption and emissions bands characteristic of the dansylamide fluorophore and both present intramolecular excited state proton transfer at intermediate pH ranges. One of the ligands (L2) strongly coordinates Zn(II) leading to fluorescence quenching. A model compound (L3) of the dansyl moiety was also investigated. (c) 2006 Elsevier B.V. All rights reserved.

Sousa, M, Melo MJ, Casimiro T, Aguiar-Ricardo A.  2007.  The art of CO2 for art conservation: a green approach to antique textile cleaning. Green Chemistry. 9:943-947., Number 9 Abstract
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de Melo, SJ, Costa T, Francisco A, Macanita AL, Gago S, Goncalves IS.  2007.  Dynamics of short as compared with long poly(acrylic acid) chains hydrophobically modified with pyrene, as followed by fluorescence techniques. Physical Chemistry Chemical Physics. 9:1370-1385., Number 11 Abstract
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Frade, RFM, Matias A, Branco LC, Afonso CAM, Duarte CMM.  2007.  Effect of ionic liquids on human colon carcinoma HT-29 and CaCo-2 cell lines. Green Chemistry. 9:873-877., Number 8 Abstract
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Afonso, CAM, Branco LC, Candeias NR, Gois PMP, Lourenco NMT, Mateus NMM, Rosa JN.  2007.  Efficient catalyst reuse by simple dissolution in non-conventional media. Chemical Communications. :2669-2679., Number 26 Abstract
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Melo, MJ, Sousa M, Parola JA, Seixas de Melo SJ, Catarino F, Marcalo J, Pina F.  2007.  Identification of 7,4 '-dihydroxy-5-methoxyflavylium in "Dragon's blood": To be or not to be an anthocyanin. Chemistry-a European Journal. 13:1417-1422., Number 5 Abstract
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Moura, L, Melo MJ, Casanova C, Claro A.  2007.  A study on Portuguese manuscript illumination: The Charter of Vila Flor (Flower town), 1512. Journal of Cultural Heritage. 8:299-306., Number 3 Abstract
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Noronha, M, Lima JC, Paci E, Santos H, Macanita AL.  2007.  Tracking local conformational changes of ribonuclease A using picosecond time-resolved fluorescence of the six tyrosine residues. Biophysical Journal. 92:4401-4414., Number 12 Abstract
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