Photophysics and Photochemistry of Supramolecular Systems

Valeur, Bernard; Berberan‐Santos, Mário Nuno; Martin, Monique M.

doi:10.1002/9783527610273.ch7

Cited by 5 publications

(3 citation statements)

References 51 publications

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“…The maximum fluorescence intensity was also analyzed using a modified Stern‐Volmer equation to take into account the residual fluorescence of the complex (see ESI §6.7 for details ) [32,33] . It is clear from the graph in Figure 5, that the fluorescence intensity ratio deviates upward from linearity, which is the sign of the coexistence of two quenching mechanisms ( ESI, Figure S88 ).…”

Section: Resultsmentioning

confidence: 99%

Chloride Binding Modulated by Anion Receptors Bearing Tetrazine and Urea

et al. 2022

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Modulation and fine‐tuning of the strength of weak interactions to bind anions are described in a series of synthetic receptors. The general design of the receptors includes both a urea motif and a tetrazine motif. The synthetic sequence towards three receptors is detailed. Impacts of H‐bond strength and linker length between urea and tetrazine on chloride complexation are studied. Binding properties of the chloride anion are examined in both the ground and excited states using a panel of analytical methods (NMR spectroscopy, mass spectrometry, UV/Visible spectroscopies, and fluorescence). A ranking of the receptors by complexation strength has been determined, allowing a better understanding of the structure‐properties relationship on these compounds.

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Section: Resultsmentioning

confidence: 99%

Chloride Binding Modulated by Anion Receptors Bearing Tetrazine and Urea

et al. 2022

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“…For an excitation pulse of finite duration, P ( t ), the fluorescence anisotropy is given by , r ( t ) = P ⊗ ( r δ f ) P ⊗ f where r δ ( t ) is the anisotropy decay in response to a delta pulse, and f ( t ) is the fluorescence intensity decay in response to the same pulse, and ⊗ stands for the convolution between two functions, P ⊗ f = ∫ 0 t P false( u false) .25em f false( t − u false) .25em normald u …”

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confidence: 99%

Accurate Determination of the Limiting Anisotropy of Rhodamine 101. Implications for Its Use as a Fluorescence Polarization Standard

et al. 2008

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The S 1 -S 0 limiting anisotropy of a widely used fluorophore, rhodamine 101, is determined with unprecedented accuracy. From time-resolved and steady-state fluorescence measurements in several solvents, it is shown that the limiting anisotropy of rhodamine 101 is for all practical purposes equal to the theoretical one-photon fundamental anisotropy value of 2/5, both in rigid and in fluid media. This fact, along with the favorable chemical and photophysical properties of rhodamine 101, point to its use as a standard for fluorescence polarization measurements. It is also shown that if the excitation pulse can be considered a delta impulse with respect to the time scale of the anisotropy decay (but not necessarily to the time scale of the intensity decay), then no deconvolution procedure is needed for anisotropy decay analysis. IntroductionRhodamine 101 (also known as rhodamine 640), Chart 1, and derivatives retaining the same fluorophore are widely used as fluorescent probes. Rhodamine 101 was designed so that no rotation of the amino groups is possible, 1,2 in the hope of achieving unit fluorescence quantum yield, but this was not fulfilled. 3 Indeed, its fluorescence quantum yield, although high, is similar to that of rhodamine 6G [3][4][5] and is in fact distinctly lower than 1.0, 4-6 which is the value initially reported. 1,2,7 In room temperature acidified ethanol, where the dye is present in the cationic form, it has a fluorescence quantum yield of about 0.9 6 and a single exponential fluorescence decay with a lifetime of 4.3 ns. 6 The cation and the zwitterion share a common fluorophore, whereas the lactone form has quite different photophysical properties. 8 A precise determination of the S 1 -S 0 limiting anisotropy (i.e., the highest measured S 1 -S 0 anisotropy for a given molecule) of several xanthene dyes, including the rhodamines B, 6G and 101, and fluorescein, r 0 ) 0.373 ( 0.002, was reported by Johansson, 9 on the basis of both steady-state and time-resolved measurements. This begs the question as to why the limiting anisotropy is lower than the fundamental anisotropy, whose onephoton theoretical value is 0.4 for parallel absorption and emission transition moments.The fact that the limiting anisotropy seldom attains the theoretical value of 2 / 5 has been subject of considerable attention over the years; see, e.g., the classic work of Feofilov 10 for an early view, and Valeur's book 11 for a recent discussion. Possible reasons for the discrepancy fall in four categories: (i) instrumental effects (effect of wide angle collection and/or of polarizer misalignment, 12,13 etc.); (ii) matrix-dependent effects (depolarization by light scattering, depolarization by stress-induced optical activity in solid glasses, depolarization by residual rotational motion); (iii) intermolecular effects (depolarization by radiative and/or nonradiative energy migration); (iv) intramolecular effects (mixed polarization bands, significantly different geometries for the Franck-Condon and emissive states implying noncoinci...

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“…In the circular dichroism spectra, working in other concentration domain and measuring a ground state property, we evidenced the presence of a 1:1 complex but the association constants are different as compared to those obtained by fluorescence. Getting different values for the association constants, by the use of several experimental methods, is a widely discussed topic in literature (Valeur et al, 2007), various explanations being given, the different range of concentrations used being the most frequent (Radi & Eissa, 2011). Another explanation invoked especially for the cases in which association parameters measured using fluorescence, on one side, and absorption and circular dichroism spectroscopies, on the other, are compared consists in the different features of the involved guest state, the excited state for the first method and the ground state for the other two.…”

Section: Discussionmentioning

confidence: 99%