Publications

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2004
Ferrer, M, Rodriguez L, Rossell O, Lima JC, Gomez-Sal P, Martin A.  2004.  Unexpected alkyne transfer between gold and rhenium atoms and its application to the synthesis of alkynyl rhenium(I) compounds. Organometallics. 23:5096-5099., Number 21 Abstract
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Noronha, M, Lima JC, Bastos M, Santos H, Macanita AL.  2004.  Unfolding of ubiquitin studied by picosecond time-resolved fluorescence of the tyrosine residue. Biophysical Journal. 87:2609-2620., Number 4 Abstract
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2003
de Melo, JS, Pina J, Pina F, Lodeiro C, Parola AJ, Lima JC, Albelda MT, Clares MP, Garcia-Espana E, Soriano C.  2003.  Energetics and dynamics of naphthalene polyaminic derivatives. Influence of structural design in the balance static vs dynamic excimer formation, 2003. Journal of Physical Chemistry A. 107:11307-11318. Abstract

Two new fluorescent macrocyclic structures bearing two naphthalene (Np) units at both ends of a cyclic polyaminic chain were investigated with potentiometric, fluorescence (steady-state and time-resolved) and laser flash photolysis techniques. The fluorescence emission studies show the presence of an excimer species whose formation depends on the protonation state of the polyamine chains implying the existence of a bending movement (occurring in both the ground and in the first singlet excited state), which allows the two naphthalene units to approach and interact. For comparison purposes, one bis-chromophoric compound containing a rigid chain (piperazine unit) was also investigated. Its emission spectra shows a unique band decaying single exponentially thus showing that no excimer is formed. With the two new ligands, excimer formation occurs in all situations even at very acidic pH values when the protonation of the polyamine bridges is extensive. Coexistence of ground-state dimers with dynamic excimers was established based on steady-state and time-resolved fluorescence data. The energetics of excimer formation and dissociation were determined in ethanol and water. Different methods of decay analysis (independent decay deconvolution, global analysis and excimer deconvolution with monomer) were used to extract the kinetic (rate constants for excimer formation, dissociation, and decay) and thermodynamic parameters. In ethanol and acidified ethanol:water mixtures, an additional short decay time was found to exist and assigned to a dimer, whose presence is assumed to be responsible by the decrease in activation energy for excimer formation in this solvent. The results are globally discussed in terms of the small architectural differences that can induce significant changes in the photophysical behavior of the three studied compounds.

Albelda, MT, Garcia-Espana E, Gil L, Lima JC, Lodeiro C, de Melo JS, Melo MJ, Parola AJ, Pina F, Soriano C.  2003.  Intramolecular excimer formation in a tripodal polyamine receptor containing three naphthalene fluorophores, 2003. Journal of Physical Chemistry B. 107:6573-6578. Abstract

comprehensive investigation on the energetics and dynamics of a new fluorescent sensor constituted by a tripodal polyamine receptor containing three naphthalene fluorophores, compound L, is reported. The influence of external factors such as the solvent, hydrogen ion concentration, and temperature in the photophysics of the sensor is discussed. The temperature dependence of monomer/excimer interconversion of L revealed an average percentage relative sensitivity of 4.5%/degreesC thus portending its use as a temperature sensor. The activation energy for excimer formation (E-1 = 12 kJ mol(-1)) and dissociation (E-1 = 57 kJ mol(-1)), entropy change (DeltaS = -128 J K-1 mol(-1)), and the binding energy of the excimer (DeltaH = 45 kJ mol(-1)) were obtained in water at acidic pH values and ethanol (E-1 = 15 kJ mol(-1), E-1 = 40 kJ mol(-1), DeltaS = -61 J K-1 mol(-1), and DeltaH = 25 kJ mol(-1)). The dependence of the kinetic and thermodynamic parameters on the dielectric constant of the medium and on the degree of protonation of the polyamine chain was interpreted in terms of the excimer destabilization provoked by the electrostatic repulsion between the positively charged chains.

Vicente, M, Bastida R, Lodeiro C, Macias A, Parola AJ, Valencia L, Spey SE.  2003.  Metal complexes with a new N4O3 amine pendant-armed macrocyclic ligand: Synthesis, characterization, crystal structures, and fluorescence studies, 2003. Inorganic Chemistry. 42:6768-6779. Abstract

The synthesis of a new oxaaza macrocyclic ligand, L, derived from O-1,O-7-bis(2-formylphenyl)-1,4,7-trioxaheptane and tren containing an amine terminal pendant arm, and its metal complexation with alkaline earth (M = Ca2+, Sr2+, Ba2+), transition (M = Co2+, Ni2+, Cu2+, Zn2+, Cd2+), post-transition (M = Pb2+), and Y3+ and lanthanide (M = La3+, Er3+) metal ions are reported. Crystal structures of [H2L](ClO4)(2).3H(2)O, [PbL](ClO4)(2), and [ZnLCl](ClO4).H2O are also reported. In the [PbL] complex, the metal ion is located inside the macrocyclic cavity coordinated by all N4O3 donor atoms while, in the [ZnLCI] complex, the metal ion is encapsulated only by the nitrogen atoms present in the ligand. pi-pi interactions in the [H2L](ClO4)(2).3H(2)O and [PbL](ClO4)(2) structures are observed. Protonation and Zn2+, Cd2+, and Cu2+ complexation were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. The 10-fold fluorescence emission increase observed in the pH range 7-9 in the presence of Zn2+ leads to L as a good sensor for this biological metal in water solution.

Moncada, MC, Moura S, Melo MJ, Roque A, Lodeiro C, Pina F.  2003.  Complexation of aluminum(III) by anthocyanins and synthetic flavylium salts - A source for blue and purple color. Inorganica Chimica Acta. 356:51-61. Abstract
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Bracci, S, Melo MJ.  2003.  Correlating natural ageing and Xenon irradiation of Paraloid (R) B72 applied on stone. Polymer Degradation and Stability. 80:533-541., Number 3 Abstract
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Giestas, L, Yihwa C, Lima JC, Vautier-Giongo C, Lopes A, Macanita AL, Quina FH.  2003.  The dynamics of ultrafast excited state proton transfer in anionic micelles. Journal of Physical Chemistry a. 107:3263-3269., Number 18 Abstract
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Moreira, PF, Giestas L, Yihwa C, Vautier-Giongo C, Quina FH, Macanita AL, Lima JC.  2003.  Ground- and excited-state proton transfer in anthocyanins: From weak acids to superphotoacids. Journal of Physical Chemistry a. 107:4203-4210., Number 21 Abstract
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Roque, A, Lodeiro C, Pina F, Maestri M, Dumas S, Passaniti P, Balzani V.  2003.  Multistate/multifunctional systems. A thermodynamic, kinetic, and photochemical investigation of the 4 '-dimethylaminoflavylium compound. Journal of the American Chemical Society. 125:987-994., Number 4 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
Arranz, P, Albelda MT, Garcia-Espana E, Lima JC, Lodeiro C, de Melo JS, Parola AJ, Pina F.  2002.  Energy transfer between polyamine chains bearing naphthalene terminal units and K-3 Co(CN)(6) : an example of a molecular photoreactor, 2002. Journal of the Chemical Society-Dalton Transactions. :3024-3028. Abstract

Molecular photoreactors consisting of polyamine chains (receptors) bearing terminal naphthalene units (antennae) are described. The receptors are used to bind the substrate hexacyanocobaltate(III) and the antennae to transfer energy to the complex and thus promote a photoaquation reaction.

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.

Lima, JC, Vautier-Giongo C, Lopes A, Melo E, Quina FH, Macanita AL.  2002.  Color stabilization of anthocyanins: Effect of SDS micelles on the acid-base and hydration kinetics of malvidin 3-glucoside (Oenin). Journal of Physical Chemistry a. 106:5851-5859., Number 24 Abstract
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de Melo, JS, Albelda MT, Diaz P, Garcia-Espana E, Lodeiro C, Alves S, Lima JC, Pina F, Soriano C.  2002.  Ground and excited state properties of polyamine chains bearing two terminal naphthalene units. Journal of the Chemical Society-Perkin Transactions 2. :991-998., Number 5 Abstract
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Pina, F, Lima JC, Lodeiro C, de Melo JS, Diaz P, Albelda MT, Garcia-Espana E.  2002.  Long range electron transfer quenching in polyamine chains bearing a terminal naphthalene unit. Journal of Physical Chemistry a. 106:8207-8212., Number 35 Abstract
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Vautier-Giongo, C, Yihwa C, Moreira PF, Lima JC, Freitas AA, Alves M, Quina FH, Macanita AL.  2002.  Manipulation of the reactivity of a synthetic anthocyanin analogue in aqueous micellar media. Langmuir. 18:10109-10115., Number 26 Abstract
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Melo, MJ, Moura S, Maestri M, Pina F.  2002.  Micelle effects on multi state/multifunctional systems based on photochromic flavylium compounds. The case of luteolinidin. Journal of Molecular Structure. 612:245-253., Number 2-3 Abstract
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Roque, A, Lodeiro C, Pina F, Maestri M, Ballardini R, Balzani V.  2002.  Photochromic properties of 3-methyl-substituted flavylium salts. European Journal of Organic Chemistry. :2699-2709., Number 16 Abstract
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Macanita, AL, Moreira PF, Lima JC, Quina FH, Yihwa C, Vautier-Giongo C.  2002.  Proton transfer in anthocyanins and related flavylium salts. Determination of ground-state rate constants with nanosecond laser flash photolysis. Journal of Physical Chemistry a. 106:1248-1255., Number 7 Abstract
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2001
Lodeiro, C, Pina F, Parola AJ, Bencini A, Bianchi A, Bazzicalupi C, Ciattini S, Giorgi C, Masotti A, Valtancoli B, de Melo JS.  2001.  Exploring the photocatalytic properties and the long-lifetime chemosensor ability of Cl-2 Ru(Bpy)(2)L (L=2,5,8,11,14-pentaaza 15 )-2,2 '-bipyridilophane), 2001. Inorganic Chemistry. 40:6813-6819. Abstract

In this work a new water-soluble long-lifetime chemosensor, containing a polyamine unit connected to a complexed Ru(II) metal center, is described. Its crystal structure has been characterized by X-ray analysis. The polyamine macrocyclic unit is capable of anchoring cationic or anionic substrates, according to its protonation state. Examples of electron transfer involving the ruthenium complex core and the bound substrate are presented. The photocatalytic ability of such a system is illustrated by the oxidation of iodide to iodine promoted by light absorption at 436 nm.

Lodeiro, C, Parola AJ, Pina F, Bazzicalupi C, Bencini A, Bianchi A, Giorgi C, Masotti A, Valtancoli B.  2001.  Protonation and Zn(II) coordination by dipyridine-containing macrocycles with different molecular architecture. A case of pH-controlled metal jumping outside-inside the macrocyclic cavity, 2001. Inorganic Chemistry. 40:2968-2975. Abstract

The synthesis of the macrocyclic ligand 4,4 '-(2,5,8, 11,14-pentaaza[15])-2,2 ' -bipyridylophane (L3), which contains a pentaamine chain linking the 4,4 ' -positions of a 2,2 ' -dipyridine moiety, is reported. Protonation and Zn(II) complexation by L3 and by macrocycle L2, containing the same pentaamine chain connecting the 6,6 ' -positions of 2,2 ' -dipyridine, were studied by means of potentiometric, UV-vis, and fluorescent emission measurements. While in L2 all the nitrogen donor atoms are convergent inside the macrocyclic cavity, in L3 the heteroaromatic nitrogen atoms are located outside. Both ligands form mono- and dinuclear Zn(II) complexes in aqueous solution. In the mononuclear Zn(II) complexes with L2, the metal is coordinated inside the macrocyclic cavity, bound to the heteroaromatic nitrogen donors and three amine groups of the aliphatic chain. As shown by the crystal structure of the [ZnL2](2+) complex, the two benzylic nitrogens are not coordinated and facile protonation of the complex takes place at slightly acidic pH values. Considering the mononuclear [ZnL3](2+) complex, the metal is encapsulated inside the cavity, not coordinated by the dipyridine unit. Protonation of the complex occurs on the aliphatic polyamine chain and gives rise to translocation of the metal outside the cavity, bound to the, heteroaromatic nitrogens.

Dias, FB, Lima JC, Pierola IF, Horta A, Macanita AL.  2001.  Internal dynamics of poly(methylphenylsiloxane) chains as revealed by picosecond time resolved fluorescence. Journal of Physical Chemistry a. 105:10286-10295., Number 45 Abstract
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