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The book on how to make all the colour paints for illuminating books: unravelling a Portuguese Hebrew illuminators’ manual
Publication . Melo, Maria J.; Castro, Rita; Nabais, Paula; Vitorino, Tatiana; LAQV@REQUIMTE; DCR - Departamento de Conservação e Restauro; SpringerOpen
The book on how to make all the colour paints for illuminating books invites readers to step inside the workshop of a fifteenth century illuminator in Portugal. This illuminator was the carrier of a tradition on how to make colours with ‘which you can illuminate or paint or capitalize or write’ that dates back, at least, to the thirteenth century. This unique knowledge and know-how was carefully preserved in Portuguese language, in Hebrew characters, in a collection of texts now known as Ms. Parma 1959 (Parma, Italy, Biblioteca Palatina, MS 1959, folios 1r–20r). Its ultimate purpose was possibly to assist on the production of Hebrew Bibles, where the precision of the text would have been illuminated by the colours described in this ‘book of all colour paints’. This medieval treatise describes the main steps and ingredients for producing painting materials, such as mosaic gold, red lead, verdigris, brazilwood lake pigments, lac dye red, vermilion, parchment glue, among others. It also instructs on the binding media that should be used to produce the colour paints. In this paper, we will discuss the technical aspects relevant for the success of the making of the painting materials and of the experimentation of this remarkable text, copied in the fifteenth century.
Cu(II) complexes derived from N-carboxymethyl and N-carboxyethyl amino acids as catalysts for asymmetric oxidative coupling of 2-naphthol
Publication . Adão, P.; Teixeira, Carlos M.; Carvalho, M. Fernanda N. N.; Kuznetsov, Maxim L.; Gomes, Clara S.B.; Pessoa, João Costa; LAQV@REQUIMTE; DQ - Departamento de Química; Elsevier BV
The synthesis, characterization and catalytic performance of chiral Cu(II) complexes derived from N-carboxymethylated and N-carboxyethylated amino acids is reported. The ligand precursors are prepared by single step N-alkylation of the sodium salts of the appropriate chiral amino acid with either sodium chloroacetate or sodium 3-chloropropionate in water. The Cu(II) complexes are obtained upon reaction of Cu(CH3COO)2 with the aqueous or alcoholic suspension of the suitable ligand under vigorous stirring or ultrasound irradiation at room temperature. The Cu(II) compounds are characterised by EPR, UV–vis, circular dichroism and ESI-MS. The molecular structures of two of the prepared complexes are also obtained by single-crystal X-ray diffraction analysis. The catalytic activity of the complexes in the asymmetric oxidative coupling of 2-naphthol is described. All compounds exhibit moderate activity, selectivity and enantioselectivity in ethanol/water mixtures, under aerobic conditions and using potassium iodide as additive. The yields of 1,1′-bi-2-naphthol (BINOL) reached 50% under the optimal conditions, while enantiomeric excesses reached ca. 48%. The effect of variables such as ligand substituents, solvent, temperature and additives on the catalytic activity is also described. In the absence of a base, the complexes only show catalytic activity in the presence of alkali metal iodide such as KI. Details of the oxidative coupling mechanism are studied using spectroscopic and electrochemical methodologies.
Microspectrofluorimetry and chemometrics for the identification of medieval lake pigments
Publication . Nabais, Paula; Melo, Maria J.; Lopes, João A.; Vitorino, Tatiana; Neves, Artur; Castro, Rita; LAQV@REQUIMTE; DCR - Departamento de Conservação e Restauro; SpringerOpen
Microspectrofluorimetry offers high sensitivity, selectivity, fast data acquisition, good spatial resolution (down to 2 μm), and the possibility of in-depth profiling. It has proved to be a powerful analytical tool in identifying dyes and lake pigments in works of art. To maximize the extraction of the information present in fluorescence emission and excitation spectra, we propose a chemometric approach to discriminate dark reds to pink colours based on brazilwood, cochineal, kermes and lac dye. These range of hues was obtained using a diverse range of medieval recipes for brazilwood, kermes and lac colourants and Winsor and Newton archive for cochineal lake pigments; the lake pigments were analyzed as colour paints (arabic-gum and glair were the medieval binders selected). Unsupervised (HCA & PCA) and supervised (SIMCA) modelling were tested, allowing to explore similarities between colourants and classify the spectral data into the different lake pigments classes. It was possible to separate the four different chromophores based on their excitation spectra or bringing together the emission and excitation spectra. The first method could also differentiate between the cochineal lake pigments, in particular between crimson lakes with different aluminates and an extender (gypsum) and between carmines with different complexing ions (aluminum and calcium).
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Fundação para a Ciência e a Tecnologia
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3599-PPCDT
Número da atribuição
RECI/QEQ-MED/0330/2012