Publications

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2001
Pina, F, Melo MJ, Alves S, Ballardini R, Maestri M, Passaniti P.  2001.  Micelle effect on ground and excited state proton transfer reactions involving the 4-methyl-7-hydroxyflavylium cation. New Journal of Chemistry. 25:747-752., Number 5 Abstract
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Bernardo, MA, Alves S, Pina F, de Melo JS, Albelda MT, Garcia-Espana E, Llinares JM, Soriano C, Luis SV.  2001.  Polyamine linear chains bearing two identical terminal aromatic units. Evidence for a photo induced bending movement. Supramolecular Chemistry. 13:435-445., Number 3 Abstract
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Albelda, MT, Bernardo MA, Diaz P, Garcia-Espana E, de Melo JS, Pina F, Soriano C, Santiago VLE.  2001.  Polyamines containing naphthyl groups as pH-regulated molecular machines driven by light. Chemical Communications. :1520-1521., Number 16 Abstract
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2000
Bencini, A, Bianchi A, Lodeiro C, Masotti A, Parola AJ, Pina F, de Melo JS, Valtancoli B.  2000.  A novel fluorescent chemosensor exhibiting exciplex emission. An example of an elementary molecular machine driven by pH and by light, 2000. Chemical Communications. :1639-1640. Abstract

Coordination/detachment of a pendent functionality in the Zn(ii) complex with a macrocyclic ligand L gives rise to on/off switching of exciplex emission, defining an elementary molecular machine whose movements are driven by both pH and light.

Dias, FB, Lima JC, Macanita AL, Clarson SJ, Horta A, Pierola IF.  2000.  Anomalous fluorescence of linear poly(methylphenylsiloxane) in dilute solution at temperatures below-50 degrees C. Macromolecules. 33:4772-4779., Number 13 Abstract
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Pina, F, Melo MJ, Maestri M, Passaniti P, Balzani V.  2000.  Artificial chemical systems capable of mimicking some elementary properties of neurons. Journal of the American Chemical Society. 122:4496-4498., Number 18 Abstract
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Dias, FB, Lima JC, Macanita AL, Horta A, Pierola IF.  2000.  Dynamics of cyclic methylphenyltrisiloxane in the picosecond to nanosecond time range. Journal of Physical Chemistry a. 104:17-24., Number 1 Abstract
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Maestri, M, Pina F, Roque A, Passaniti P.  2000.  Light and pH switching between the various forms of the 4 '-methylflavylium cation. Journal of Photochemistry and Photobiology a-Chemistry. 137:21-28., Number 1 Abstract
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Melo, MJ, Moncada MC, Pina F.  2000.  On the red colour of raspberry (Rubus idaeus). Tetrahedron Letters. 41:1987-1991., Number 12 Abstract
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Bazzicalupi, C, Bencini A, Bianchi A, Giorgi C, Fusi V, Masotti A, Valtancoli B, Roque A, Pina F.  2000.  pH modulation of the luminescence emission of a new europium cryptate complex. Chemical Communications. :561-562., Number 7 Abstract
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Melo, MJ, Moura S, Roque A, Maestri M, Pina F.  2000.  Photochemistry of luteolinidin - "Write-lock-read-unlock-erase'' with a natural compound. Journal of Photochemistry and Photobiology a-Chemistry. 135:33-39., Number 1 Abstract
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Elisei, F, Lima JC, Ortica F, Aloisi GG, Costa M, Leitao E, Abreu I, Dias A, Bonifacio V, Medeiros J, Macanita AL, Becker RS.  2000.  Photophysical properties of hydroxy-substituted flavothiones. Journal of Physical Chemistry a. 104:6095-6102., Number 25 Abstract
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1999
Kuhn, FE, Goncalves IS, Lopes AD, Lopes JP, Romao CC, Wachter W, Mink J, Hajba L, Parola AJ, Pina F, Sotomayor J.  1999.  Tetracarboxylatodirhenium complexes linked by axial cyano bridges to metalpentacarbonyl ligands - Synthesis and characterization, 1999. European Journal of Inorganic Chemistry. :295-301. Abstract

Reaction of Re-2{mu-O2CC(CH3)(3)}(4)Cl-2 with [(CO)(5)M-CN]Na (M = Cr, Mo, W) leads to tetranuclear complexes of formula Re-2{mu-O2CC(CH3)(3)}(4)[-NC-M(CO)(5)](2) (M = Cr, Mo, W). These complexes were characterized by H-1-, C-13-, and Mo-95-NMR, IR and Raman spectroscopy, elemental analysis and examined by cyclic voltammetry. The applied methods show the donor capabilities of the [(CO)(5)M-CN](-) ligands which shift electron density towards the Re centers weakening the Re-Re quadruple bond. The Re-Re bond lengths and the v(Re-Re) force constants are estimated based on the FT-IR and Raman examinations. Photochemical examinations and TG/MS experiments have also been conducted. The latter methods shows that the product complexes decompose around 100 degrees C, by first loosing their carbonyl substituents; as do the Cr, Mo, W precursor compounds. The dirhenium tetrapivalate unit decomposes only at higher temperatures in a distinct second step.

Pina, F, Melo MJ, Bernardo MA, Luis SV, Garcia-Espana E.  1999.  Chemosensors displaying pH controlled multistage fluorescence emission. Journal of Photochemistry and Photobiology a-Chemistry. 126:65-69., Number 1-3 Abstract
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Roque, A, Pina F, Alves S, Ballardini R, Maestri M, Balzani V.  1999.  Micelle effect on the 'write-lock-read-unlock-erase' cycle of 4 '-hydroxyflavylium ion. Journal of Materials Chemistry. 9:2265-2269., Number 9 Abstract
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Pina, F, Melo MJ, Maestri M, Passaniti P, Camaioni N, Balzani V.  1999.  Photo- and pH-Induced transformations of flavylium cation: "Write-lock-read-unlock-erase" cycles. European Journal of Organic Chemistry. :3199-3207., Number 11 Abstract
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Pina, F, Maestri M, Balzani V.  1999.  Photochromic flavylium compounds as multistate/multifunction molecular-level systems. Chemical Communications. :107-114., Number 2 Abstract
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Melo, MJ, Bracci S, Camaiti M, Chiantore O, Piacenti F.  1999.  Photodegradation of acrylic resins used in the conservation of stone. Polymer Degradation and Stability. 66:23-30., Number 1 Abstract
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Osuka, A, Kume T, Haggquist GW, Javorfi T, Lima JC, Melo E, Naqvi KR.  1999.  Photophysical characteristics of two model antenna systems: a fucoxanthin-pyropheoporbide dyad and its peridinin analogue. Chemical Physics Letters. 313:499-504., Number 3-4 Abstract
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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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Albelda, MT, Bernardo MA, Garcia-Espana E, Godino-Salido ML, Luis SV, Melo MJ, Pina F, Soriano C.  1999.  Thermodynamics and fluorescence emission studies on potential molecular chemosensors for ATP recognition in aqueous solution. Journal of the Chemical Society-Perkin Transactions 2. :2545-2549., Number 11 Abstract
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1998
Pina, F, Melo MJ, Parola AJ, Maestri M, Balzani V.  1998.  pH-controlled photochromism of hydroxyflavylium ions, 1998. Chemistry-a European Journal. 4:2001-2007. Abstract

The structural transformations and photochromic properties of the 7-hydroxyflavylium ion have been investigated by means of the pH jump technique and continuous and pulsed light excitation. The primary photoproduct of UV irradiation of the colorless trans-chalcone form, which is the predominant species at pH 4, is its colorless cis isomer, which rapidly disappears on a time scale of seconds through two competitive processes: i) back-reaction to yield the trans-chalcone form, and ii) formation of the colored flavylium ion and its conjugated quinoidal base. Over minutes or hours (depending on pH), the system reverts quantitatively to its original state. The rate constants and equilibrium constants of the various processes have been obtained and compared with those previously reported for the 4'-hydroxyflavylium and 4',7-dihydroxyflavylium ions. This comparison demonstrates the substituent effect on the rate and equilibrium constants; the effect on the rate constant of the cis-->trans thermal isomerization reaction is particularly strong. For the 7-hydroxyflavylium and 4',7-dihydroxyflavylium ions the pH of the solution plays the role of a tap for the color intensity generated by light excitation. This also means that this system can be viewed as a light-switchable pH indicator.

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.

Houbiers, C, Lima JC, Macanita AL, Santos H.  1998.  Color stabilization of malvidin 3-glucoside: Self-aggregation of the flavylium cation and copigmentation with the Z-chalcone form. Journal of Physical Chemistry B. 102:3578-3585., Number 18 Abstract
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Laia, CAT, Lopez-Cornejo P, Costa SMB, d'Oliveira J, Martinho JMG.  1998.  Dynamic light scattering study of AOT microemulsions with nonaqueous polar additives in an oil continuous phase. Langmuir. 14:3531-3537., Number 13 Abstract
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