Publications

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2000
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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Pina, F, Bernardo MA, Garcia-Espana E.  2000.  Fluorescent chemosensors containing polyamine receptors. European Journal of Inorganic Chemistry. :2143-2157., Number 10 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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Laia, CAT, Brown W, Almgren M, Costa SMB.  2000.  Light scattering study of water-in-oil AOT microemulsions with poly(oxy)ethylene. Langmuir. 16:465-470., Number 2 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
Pina, F, Parola AJ.  1999.  Photochemistry of supramolecular species involving anionic coordination compounds and polyammonium macrocyclic receptors, 1999. Coordination Chemistry Reviews. 185-6:149-165. Abstract

Polyammonium macrocyclic receptors can bind anionic coordination compounds, namely those containing cyanide ligands. The;driving force to maintain the adduct is essentially the coulombic attraction, but the possibility of formation of hydrogen bonds is also important to define the geometry of the structure. The second coordination sphere that results from the binding of the polyammonium macrocycle can change several physicochemical properties of the metal coordination-compound, such as spectroscopic, redox and photophysical properties as well as the photochemical reactivity. These. changes permit:to infer, in some favourable cases, details of the supramolecular structure in solution. (C) 1999 Elsevier Science S.A. All rights reserved.

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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Bazzicalupi, C, Bencini A, Bianchi A, Giorgi C, Fusi V, Valtancoli B, Bernardo MA, Pina F.  1999.  Effect of protonation and Zn(II) coordination on the fluorescence emission of a phenanthroline-containing macrocycle. An unusual case of "nonemissive'' Zn(II) complex. Inorganic Chemistry. 38:3806-3813., Number 17 Abstract
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Bencini, A, Bernardo MA, Bianchi A, Fusi V, Giorgi C, Pina F, Valtancoli B.  1999.  Macrocyclic polyamines containing phenanthroline moieties - Fluorescent chemosensors for H+ and Zn2+ ions. European Journal of Inorganic Chemistry. :1911-1918., Number 11 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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Laia, CAT, Costa SMB.  1999.  Probing the interface polarity of AOT reversed micelles using centro-symmetrical squaraine molecules. Physical Chemistry Chemical Physics. 1:4409-4416., Number 18 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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Bernardo, MA, Pina F, Escuder B, Garcia-Espana E, Godino-Salido ML, Latorre J, Luis SV, Ramirez JA, Soriano C.  1999.  Thermodynamic and fluorescence emission studies on chemosensors containing anthracene fluorophores. Crystal structure of { (CuLCl)-Cl-1 Cl}(2)center dot 2H(2)O L-1 = N-(3-aminopropyl)-N '-3-(anthracen-9-ylmethyl)aminopropylethane-1,2-diamine. Journal of the Chemical Society-Dalton Transactions. :915-921., Number 6 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
Bencini, A, Bernardo MA, Bianchi A, Ciampolini M, Fusi V, Nardi N, Parola AJ, Pina F, Valtancoli B.  1998.  Modulation of the ligational properties of a new cylindrical macrotricycle by coupling of photochemical- and pH-switching properties, 1998. Journal of the Chemical Society-Perkin Transactions 2. :413-418. Abstract

The new cylindrical molecule L containing two tetraazamacrocyclic rings linked by two azobenzene pillars displays photoelastic properties, Light absorption at 366 nm gives rise to trans --> cis isomerization of the azobenzene moieties producing two isomers containing one or two cis-azobenzenes, respectively, The three trans-trans (E-E), trans-cis (E-Z) and cis-cis (Z-Z) isomers have been identified and characterized by H-1 NMR spectroscopy, allowing the dependence of their formation percentages with irradiation time to be determined, The sequence of photochemical reactions E-E --> E-Z --> Z-Z allows almost complete conversion of the E-E into the Z-Z isomer at 366 nm and 298 K, Both thermal (k = 1.75 x 10(-5) s(-1) at 313 K) and photo-induced (at 436 and 313 nm) back-isomerization reactions have been studied, The protonation constants of the three isomers in equimolar solutions of water-DMSO indicate a decreasing basicity in the order E-E > E-Z > Z-Z, in agreement with increasing electrostatic repulsion between the positive charges caused by a reduction in the separation between the protonation sites occurring upon Z --> E isomerization.

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.