Fluorescence emission properties

F. Fages, J.-P. Desvergne, H. Bouas-Laurent, J.-M. Lehn, J. P. Konopelski, P. Marsau, and Y. Barrans, Synthesis and fluorescence emission properties of a bis-anthracenyl macrotricyclic ditopic receptor. Crystal structure ofits dinuclear rubidium cryptate, J. Chem. Soc., Chem. Commun. 655(1990). 

Ultraviolet (UV) spectroscopy does not tend to be the method of choice for structure determination, but a list of UV absorptions was given in the review by Knowles <1996CHEC-II(7)489>. Fluorescence properties and triplet yields of [l,2,3]triazolo[4,5-r/ pyridazines in various solvents have been reported <2002JPH83>. These heterocyclic systems were found to be photochemically very stable. In a recent paper, Wierzchowski et al. studied the fluorescence emission properties of 8-azaxanthine ([l,2,3]triazolo[4,5-r/ pyrimidine-5,7-dione) and its A -alkyl derivatives at various pH s <2006JPH276>. For the 8-azaxanthines, an important characteristic of emission spectra in aqueous solutions was the unusually large Stokes shift. Since 8-azaxanthine is a substrate for purine nucleoside phosphorylase II from Escherichia coli, the reaction is now monitored fluorimetrically. The fluorescence properties of [l,2,3]triazolo[4,5-r/ -pyrimidine ribonucleosides were earlier described by Seela et al. <2005HCA751>. 

Garcia et al. [4] concluded from their important photophysical study that the fluorescence emission properties of these 10-alkylated phenothiazine derivatives are very sensitive to the solvent and the 2-substituent, but practically not to the nature of their 10-alkylamino chain. 

Acree Jr WE, Tucker SA and Fetzer JC (1991) Fluorescence emission properties of polycyclic aromatic compounds in review. In Polycyclic Aromatic Compounds, Vol 2, 75- 105. Lausanne, Switzerland Gordon and Breach. 

From these results, and from the reported extrapolated values of 276 °C (syndiotactic) and 126 °C (isotactic) for the glass transition temperatures of PNVC it has been concluded that rotational eclipsing in isotactic NVC sequences is very much more favourable than in corresponding syndiotactic sequences. This contusion is strongly supported by examination of space filling molecular models. Such considerations must be borne in mind when considering the optical and chiroptical properties of carbazole containing polymers and it has to be expected that copolymers of NVC will have fluorescence emission properties that can be related to both main chain tacticity and distribution of monomeric units. Free radically polymerized mixtures of NVC and acrylic derivatives of (—)-menthol have fluorescence spectra... 

In a similar way to pyrene derivatives, the excellent electronic absorption and fluorescence emission properties of perylene derivatives lead to scientists working in various areas of materials science to study their physical properties. Depending... 

Properties of the activation product. The two decylamine-activation products (luciferins) showed similar absorption characteristics (A.max 372 nm in water, and 375 nm in ethanol), which clearly differ from the absorption peak of the natural luciferin (320 nm) reported by Kuwabara and Wassink (1966). The fluorescence emission of the activation products varied significantly by solvents, showing a peak at 460 nm in neutral aqueous solution and a broad peak at 485-522 nm in ethanol. They emitted chemiluminescence (A.max 580 nm) in the presence of CTAB, H2O2 and Fe2+ (Fig. 9.13), in resemblance to the (NH4)2S04-activation product of panal (A.max 570 nm). 

The high-spin/low-spin interconverison in a Ni11 complex of the cyclam derivative (639) bearing a luminescent naphthalene substituent has been used as a fluorescent molecular thermometer.161 The Ni11 tends to quench fluorescence of the proximate naphthalene subunit, but the two spin states exert a different influence on the emission properties. Emission is temperature dependent, since the high spin —> low spin conversion is endothermic, i.e., a temperature increase favors formation of the low-spin form. 

This is the first Cys fluorescent sensor derived from FONs, in which the fluorescence enhancing property is in conjunction with a remarkable red-shifted fluorescence emission. Despite the potential sources of error when considering complicated clinical samples, the authors believe that this probe can be applied to study the effects of Cys in a biological system. 

Different substituents on the carboxy-functionalized fluorescein can be introduced to produce marked alterations in the absorbance and fluorescence emission wavelengths, as well as in other physical properties. The selective substitution of chlorine for aromatic hydrogen has been found to increase fluorescence efficiency and to narrow emission and absorbance maxima when compared with fluorescein 48, which is useful in multicolor imaging. 

Replacing the nitrile group by a benzothiazole produces an important subclass of fluorescent compounds represented by thioflavin T (25, Fig. 10). It is not clear if this compound undergoes deactivation via intramolecular rotation that would meet the criterion for a molecular rotor. The steady-state absorption and emission properties of thioflavin T has been attributed to micelle formation [53, 54], dimer and excimer formation [55, 56], and deactivation through intramolecular rotation [57]. 

Molecular rotors are useful as reporters of their microenvironment, because their fluorescence emission allows to probe TICT formation and solvent interaction. Measurements are possible through steady-state spectroscopy and time-resolved spectroscopy. Three primary effects were identified in Sect. 2, namely, the solvent-dependent reorientation rate, the solvent-dependent quantum yield (which directly links to the reorientation rate), and the solvatochromic shift. Most commonly, molecular rotors exhibit a change in quantum yield as a consequence of nonradia-tive relaxation. Therefore, the fluorophore s quantum yield needs to be determined as accurately as possible. In steady-state spectroscopy, emission intensity can be calibrated with quantum yield standards. Alternatively, relative changes in emission intensity can be used, because the ratio of two intensities is identical to the ratio of the corresponding quantum yields if the fluid optical properties remain constant. For molecular rotors with nonradiative relaxation, the calibrated measurement of the quantum yield allows to approximately compute the rotational relaxation rate kor from the measured quantum yield [Pg.284]

The chromophore of ECFP does not bear the deprotonable phenol that is crucial to the photophysics of most AvGFP variants, and displays a markedly different spectroscopy. It has been quickly recognized that, despite its prominent interest in biological applications, the properties of this variant are suboptimal. Indeed, while the brightness of the protein is relatively low (eM = 32,000 M 1 cm-1, fluorescence emission is both spectrally and kinetically heterogeneous. The fluorescence comprises two major decay times at 3.6 ns and 1.3 ns... 

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