Spectroscopy and photophysics of 4- and 7-hydroxycoumarins and their thione analogs

Melo, J. Sérgio Seixas de; Fernandes, Patrick

doi:10.1016/s0022-2860(01)00458-6

Cited by 149 publications

(130 citation statements)

References 16 publications

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“…Absorption spectra were recorded on a Perkin-Elmer Lambda 6 spectrophotometer and fluorescence emission on a Jobin Yvon-Spex Fluorolog 3.22 spectrofluorimeter. The fluorescence decays were obtained at pH ¼ 1.41 (in 0:15 mol dm À3 NaCl), with excitation at 280 nm and the emission collected at 330 and 450 nm using the equipment described elsewhere [8]. All measurements were made in the presence of oxygen to reproduce the conditions where steady-state fluorescence data were obtained.…”

Section: à3mentioning

confidence: 99%

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

Albelda

Díaz

Garcı́a-España

et al. 2002

Chemical Physics Letters

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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 Zn 2þ . The largest energy transfer efficiency ðg ¼ 0:61Þ occurs for the fully protonated form ðpH < 2Þ, 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 Zn 2þ prevents the eT quenching allowing the ET process to occur. Ó

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Section: à3mentioning

confidence: 99%

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

Albelda

Díaz

Garcı́a-España

et al. 2002

Chemical Physics Letters

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“…The low optical density of the samples used prevents self-absorption or inner-filter effects. Fluorescence decays were measured using a home-built time-correlated single-photon-counting (TCSPC) apparatus as described elsewhere, [34] except that a Horiba-JI-IBH NanoLED, (l exc = 339 nm or 281 nm) was used as the excitation source. The fluorescence decays were analyzed using the "modulating functions" method of Striker et al [35] Temperature control was achieved using a homebuilt system based on cooled nitrogen and electric heating, which is automatically controlled by the difference between the input temperature value and the real temperature of the sample determined with a PT100 thermometer.…”

Section: Methodsmentioning

confidence: 99%

Temperature Dependence of Ultra‐Exothermic Charge Recombinations

et al. 2006

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We measured the temperature dependence (from +32 to −50 °C) of charge‐recombination rates between contact radical ion pairs in isopropyl ether. In the systems selected for this study, aromatic hydrocarbon cations are the electron acceptors and the fumaronitrile anion is the electron donor. Nearly quantitative electron transfers occur at all temperatures. The charge recombinations have excess exothermicities of −60 kcal mol−1 and exhibit a very weak temperature dependence. Our observations emphasize the absence of solvent effects and the relevance of nuclear tunneling in charge recombinations.

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“…Alternate measurements (1000 counts per cycle), controlled by Decay ® software (Biodinâmica-Portugal), of the pulse profile at 337, 356 or 373 nm and the sample emission were performed until 1 to 2 × 10 4 counts at the maximum were reached. [23] The fluorescence decays were analysed using the modulating functions method of Striker with automatic correction for the photomultiplier "wavelength shift" [24]. All experiments were carried out at room temperature.…”

Section: Spectroscopic Measurementsmentioning

confidence: 99%

Interactions between surfactants and {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}

Burrows

Lobo

Pina

et al. 2005

Colloids and Surfaces A: Physicochemical and Engineering Aspect

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The interaction between the water-soluble anionic conjugated copolymer poly{1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl} (PBS-PFP) and various surfactants has been studied in aqueous solution by UV-vis absorption spectra, fluorescence and electrical conductivity. It is suggested from the linear dependence of absorbance, fluorescence and electrical conductivity on concentration that in the absence of surfactant, moderately stable dispersions are formed. These are affected in different ways on adding cationic, anionic or neutral surfactants. With the cationic cetyltrimethylammonium bromide, quenching of fluorescence intensity and lifetime, and formation of a new emission occurs at concentrations well below the critical micelle concentration (cmc). Electrical conductivity measurements indicate a discontinuity at surfactant/polymer ratio corresponding to electroneutrality, due to complexation. With the anionic sodium dodecyl sulfate, fluorescence quenching is also observed, but is attributed to formation of some mixed polymer/surfactant aggregate. The most striking changes are observed with the non-ionic pentaethyleneglycol monododecyl ether (C 12 E 5 ), where a blue shift in fluorescence emission, dramatic increases in lifetime and quantum yield, and changes in electrical around the cmc are interpreted in terms of incorporation of single polymer chains in elongated cylindrical micelles. This is supported by 1 H NMR spectroscopic measurements.

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Spectroscopy and photophysics of 4- and 7-hydroxycoumarins and their thione analogs

Cited by 149 publications

References 16 publications

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

Switching from intramolecular energy transfer to intramolecular electron transfer by the action of pH and Zn2+ co-ordination

Temperature Dependence of Ultra‐Exothermic Charge Recombinations

Interactions between surfactants and {1,4-phenylene-[9,9-bis(4-phenoxy-butylsulfonate)]fluorene-2,7-diyl}

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