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2005
Gago, S, Rodriguez-Borges JE, Teixeira C, Santos AM, Zhao J, Pillinger M, Nunes CD, Petrovski Z, Santos TM, Kuhn FE, Romao CC, Goncalves IS.  2005.  Synthesis, characterization and catalytic studies of bis(chloro)dioxomolybdenum(VI)-chiral diimine complexes. Journal of Molecular Catalysis a-Chemical. 236:1-6., Number 1-2 Abstract
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2004
Clares, MP, Aguilar J, Aucejo R, Lodeiro C, Albelda MT, Pina F, Lima JC, Parola AJ, Pina J, de Melo JS, Soriano C, Garcia-Espana E.  2004.  Synthesis and H+, Cu2+, and Zn2+ coordination behavior of a bis(fluorophoric) bibrachial lariat aza-crown, 2004. Inorganic Chemistry. 43:6114-6122. Abstract

The synthesis, protonation behavior, and Cu2+ and Zn2+ coordination chemistry of the novel bibrachial aza lariat ether (naphthalen-1-ylmethyl)[2-(20-{2-[(naphthalen-1-ylmethyl)amino]ethyl}-3,6,9,17,20,23,29,30-octaazatricyclo-[23.3.1.1*11,15*]triaconta-1(29),11(30),12,14,25,27-hexaen-6-yl)ethyl]amine (L) are discussed. The macrocycle, which has two aminoethyl naphthyl moieties symmetrically appended to a 2:2 azapyridinophane structure, displays, in the pH range 2-11, six protonation steps that correspond to the protonation of the secondary amino groups. Steady-state fluorescence measurements show emissions due to the monomer and to the excimer formed between the two naphthalene fragments of the macrocycle. The time-resolved fluorescence data, obtained by the time-correlated single photon counting technique, show that a significant percentage of excimer is preformed as ground-state dimers. The ligand L forms with the metal ions Cu2+ and Zn2+ mono- and dinuclear complexes in aqueous solution. The influence of metal coordination in the fluorescence emission of L is analyzed. The acid-base, coordination capabilities, and emissive behavior of L are compared with those presented by its synthetic precursor L1, which has a tripodal tris(2-aminoethyl)amine structure functionalized at one of its terminal amino groups with a naphthyl moiety.

Gago, S, Zhang YM, Santos AM, Kohler K, Kuhn FE, Fernandes JA, Pillinger M, Valente AA, Santos TM, Ribeiro-Claro PJA, Goncalves IS.  2004.  Synthesis and characterization of a manganese(II) acetonitrile complex supported on functionalized MCM-41. Microporous and Mesoporous Materials. 76:131-136., Number 1-3 Abstract
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Gago, S, Pillinger M, Santos TM, Rocha J, Goncalves IS.  2004.  Synthesis and properties of Zn-Al layered double hydroxides containing ferrocenecarboxylate anions. European Journal of Inorganic Chemistry. :1389-1395., Number 7 Abstract
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2003
Rodriguez, L, Alves S, Lima JC, Parola AJ, Pina F, Soriano C, Albelda T, Garcia-Espana E.  2003.  Supramolecular interactions of hexacyanocobaltate(III) with polyamine receptors containing a terminal anthracene sensor, 2003. Journal of Photochemistry and Photobiology a-Chemistry. 159:253-258. Abstract

The fluorescence emission properties of a series of chemosensors containing a polyamine receptor bearing an anthracene signaling unit were studied. The fluorescence emission intensity is dependent on the protonation degree of the receptor, the fully protonated form exhibiting the highest emission intensity. By removing protons from the nitrogens a quenching effect can be observed, due to an electron-transfer from the amine to the excited fluorophore. The rate constant of the quenching process is exponentially dependent on the distance of the nitrogen from which the electron is transferred (beta = 0.6Angstrom(-1)). The ability of the chemosensors for signaling anions was tested through the model anion hexacyanocobaltate(III). The temperature dependence of the association constants shows that at least for this compound, the change in solvation entropy is probably the controlling parameter to account for the binding. (C) 2003 Elsevier Science B.V. All rights reserved.

Laia, CAT, Costa SMB, Phillips D, Parker AW.  2003.  Spectroscopy of photoinduced charge-transfer reactions between tetrasulfonated aluminium phthalocyanine and methyl viologen. Photochemical & Photobiological Sciences. 2:555-562., Number 5 Abstract
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Mateus, NMM, Branco LC, Lourenco NMT, Afonso CAM.  2003.  Synthesis and properties of tetra-alkyl-dimethylguanidinium salts as a potential new generation of ionic liquids. Green Chemistry. 5:347-352., Number 3 Abstract
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2002
Albelda, MT, Diaz P, Garcia-Espana E, Lima JC, Lodeiro C, de Melo JS, Parola AJ, Pina F, Soriano C.  2002.  Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination, 2002. Chemical Physics Letters. 353:63-68. Abstract

Intramolecular electron (eT) and energy transfer (ET) have shown to occur in a covalently linked donor-acceptor (CLDA) system consisting of a naphthalene donor covalently linked through a polyamine chain connector to an anthracene acceptor; the connector has been chosen in order to switch ON or OFF the energy flux as a function of its protonation state as well as by co-ordination to Zn2+. The largest energy transfer efficiency (eta = 0.61) occurs for the fully protonated form (pH < 2), while at pH > 9 (eT) from the lone pairs of the nitrogens to the excited fluorophore takes place, leading to complete quenching of the emission. On the other hand at neutral and basic pH values. coordination of Zn2+ prevents the eT quenching allowing the ET process to occur. (C) 2002 Elsevier Science B.V. All rights reserved.

Branco, LC, Crespo JG, Afonso CAM.  2002.  Studies on the selective transport of organic compounds by using ionic liquids as novel supported liquid membranes. Chemistry-a European Journal. 8:3865-3871., Number 17 Abstract
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2001
Laia, CAT, Costa SMB.  2001.  Solvatochromism and thermochromism of the electronic spectra of an indocarbocyanine dye. Journal of Molecular Structure. 565:83-86. Abstract
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1999
Ciampolini, M, Formica M, Fusi V, Saint-Mauricec A, Micheloni M, Nardi N, Pontellini R, Pina F, Romani P, Sabatini AM, Valtancoli B.  1999.  Selective lithium complexation by photoactive aza-cages bearing the anthracene function. European Journal of Inorganic Chemistry. :2261-2268., Number 12 Abstract
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1998
Parola, AJ, Pina F, Manfrin MF, Moggi L.  1998.  Supramolecular interactions between Co(CN)(5)(SO3)(4-) and polyammonium macrocyclic receptors, 1998. Journal of the Chemical Society-Dalton Transactions. :1005-1009. Abstract

The acid-base properties as well as the photochemical reactivity of the co-ordination compound K-4[Co(CN)(5)(SO3)] in the presence of three polyammonium macrocyclic receptors were studied in aqueous solution. The pK(a) of the free complex (3.9) (sulfite deprotonation) changed to pK(a) <0.5 upon complexation with the receptors. The quantum yield for sulfite photoaquation of the free complex in the basic form (Phi = 0.85 +/- 0.09) decreased to 0.05 +/- 0.01, 0.12 +/- 0.03 and 0.45 +/- 0.09 in the presence of[24]aneN(8)H(8)(8+), [30]aneN(10)H(10)(10+) and [32]aneN(8)H(8)(8+), respectively. For the acidic form of the free complex (Phi = 0.40 +/- 0.05) the quantum yield was not affected by supercomplexation with [32]aneN(8)H(8)(8+). For the adducts formed from the other two macrocyclic receptors it was not possible to evaluate the quantum yields of the acidic forms, because protonation was not complete even at very high proton concentrations. The results were interpreted in terms of second-sphere interactions involving hydrogen bonding between the complex and the macrocycles. In the case of [32]aneN(8)H(8)(8+) the experimental results are compatible with a structure in which the cyanides are involved in hydrogen bonding but the sulfite ligand is not. In the two other supercomplexes the sulfite ligand seems to be involved in hydrogen bonding.

Goncalves, IS, Kuhn FE, Lopes AD, Parola AJ, Pina F, Sotomayor J, Romao CC.  1998.  Synthesis and characterization of binuclear transition metal rhenium(VII) complexes with bridging cyanide ligands, 1998. Journal of Organometallic Chemistry. 560:117-124. Abstract

Reacting transition metal complexes in low oxidation states, containing one or two cyanide ligands, with methyltrioxorhenium(VII) leads to bridged mixed metal compounds in good yields. The Re(VII) core is then surrounded by five or six ligands, respectively. The strength of these CN bridges and thus the stability of the newly generated bimetallic compound strongly depends on the donor strength of the ligands surrounding of the Cr/Mo/W or Fe moiety. The stability of the mixed metal molecules is reflected in the temperature dependent behavior of their O-17-NMR spectra, in their IR (Re=O) stretching frequencies and force constants, as well as several other spectroscopic data. UV-vis absorption spectra show the appearance of charge transfer bands. In the case of the mixed Mo/Re complexes the Mo-95-NMR spectroscopy is also a helpful tool to examine the donor capability of the Mo moiety. The described compounds also show photosensitivity. (C) 1998 Elsevier Science S.A. All rights reserved.

1997
Pina, F, Benedito L, Melo JM, Parola AJ, Lima JC, Macanita AL.  1997.  Structural transformations of the synthetic salt 4',7-dihydroxyflavylium chloride in acid and basic aqueous solutions .1. Ground state, 1997. Anales De Quimica. 93:111-118. Abstract

A complete study of the structural pH dependent transformations of the synthetic flavylium salt 4',7-dihydroxyflavylium chloride (DHF), occurring in aqueous solutions, including the basic region, is described. The kinetic study of the transformations occurring in acidic media (quinoidal base (A) reversible arrow flavylium cation (AH(+)) reversible arrow hemiacetal (B) reversible arrow cis-chalone (C-cis) reversible arrow trans-chalcone (C-trans)) allowed to conclude that the cis-trans isomerization is faster than the tautomerization and the hydration processes, which is unique in the anthocyanins family. Results obtained with the parent compound 4'7-dimethoxyglavylium chloride (DMF) with relevance to this study are also presented. In equilibrated basic solution the existence of acid-base equilibria involving the trans-Chalcone (C-trans) and its conjugated bases, (C-trans(-) and C-trans(2)), was detected. Freshly prepared solutions at pH >7 show also the presence of a transient species identified as the ionized quinoidal base (A(-)), which is almost completely converted into C-trans(2-) with a pH dependent rate constant.

1996
Melo, MJ, Bernardo MA, Melo EC, Pina F.  1996.  Shape of acid-base fluorescence emission titration curves in the presence of buffer and quenching effects. Journal of the Chemical Society-Faraday Transactions. 92:957-968., Number 6 Abstract
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1995
Bernardo, MA, Parola AJ, Pina F, Garciaespana E, Marcelino V, Luis SV, Miravet JF.  1995.  STEADY-STATE FLUORESCENCE EMISSION STUDIES ON POLYAZACYCLOPHANE MACROCYCLIC RECEPTORS AND ON THEIR ADDUCTS WITH HEXACYANOCOBALTATE(III), 1995. Journal of the Chemical Society-Dalton Transactions. :993-997. Abstract

The steady-state fluorescence emission spectra of the azacyclophanes 2,5,8,11-tetraaza[12] paracyclophane (L(1)), 2,6,9,13-tetraaza[14]paracyclophane (L(2)), 14,15,17,18-tetramethyl-2,5,8,11-tetraaza-[12]paracyclophane (L(3)) and 16,17,19,20-tetramethyl-2,6,9,13-tetraaza[14]paracyclophane (L(4)) as a function of pH have been measured. The fully protonated species of each cyclophane gives the highest fluorescence-emission quantum yield. The shapes of the titration curves have been explained by the existence of an electron-transfer quenching effect from a non-protonated amine to the benzene chromophore. This effect is greater for macrocycles in which the first deprotonated amine group is closer to the benzene. The association constants for the interaction of the four fully protonated macrocycles with K-3[Co(CN)(6)] have been measured either by potentiometry or from fluorescence-emission measurements, and increase in the order L(3) approximate to L(4) < L(1) approximate to L(2). The photoaquation quantum yields of K-3[Co(CN)(6)] have been measured in the presence of the macrocycles L(1) and L(2). and indicate that three of the CN nitrogens of the complex are involved in adduct formation with the fully protonated macrocycles, as supported by molecular modelling.

Pina, F, Parola AJ, Ferreira E, Maestri M, Armaroli N, Ballardini R, Balzani V.  1995.  SUPRAMOLECULAR PHOTOCHEMISTRY AND PHOTOPHYSICS - BIACETYL IMPRISONED IN A HEMICARCERAND, 1995. Journal of Physical Chemistry. 99:12701-12703. Abstract

When biacetyl is imprisoned into Cram's hemicarcerand 1, its absorption, fluorescence, and phosphorescence maxima are red shifted compared to the values obtained for solutions of free biacetyl in any solvent. Furthermore, the lifetime of the T-1 excited state of imprisoned biacetyl is unaffected by solvent nature and presence of dioxygen. These results show that inclusion into the hemicarcerand (i) shields biacetyl from interaction with the solvent molecules and (ii) prevents deactivation of its long-lived T-1 excited state by energy transfer to dioxygen. The perturbation provided by the cavity on the spectroscopic properties of biacetyl is much smaller than that provided by even the most ''innocent'' solvent. The consequent picture is that of a biacetyl molecule which is contained in a not-too-tight cavity where no specific host-guest interaction takes place. The peculiar spectroscopic and excited-state behavior of biacetyl imprisoned in hemicarcerand 1 supports Cram's view that the inner phase of carcerands and hemicarcerands is to be considered as a new phase of matter.

1994
Parola, AJ, Pina F, Maestri M, Armaroli N, Balzani V.  1994.  SUPRAMOLECULAR PHOTOCHEMISTRY AND PHOTOPHYSICS - 9-CYANOANTHRACENE IMPRISONED IN A HEMICARCERAND, 1994. New Journal of Chemistry. 18:659-661. Abstract

The absorption and excited state properties of 9-cyanoanthracene are strongly modified upon inclusion into an octaimine hemicarcerand; the walls of the host do not transfer excitation to the guest and quench its fluorescent excited state.