Aarhus green: a tetrafluoro-substituted derivative of fluorescein

Abstract

Dedicated to Professor Michael Orfanopoulos on the occasion of his 67th birthday ‡ These authors contributed equally to this work.DOI: http://dx.doi.org/10.3998/ark.5550190.p009.011 AbstractThe synthesis and characterization of a 2',4',5',7'-tetrafluorinated derivative of fluorescein, called Aarhus Green, is reported. As with related 2',7'-difluorinated compounds, tetrafluorination of the xanthene-derived moiety makes the more fluorescent anion accessible over a larger pH range. However, in contrast to a published report, we find that fluorination in the 4' and 5' positions does not appreciably decrease the fluorescence quantum yield, φ f . Rather, Aarhus Green has a reasonably large φ f (0.79 ± 0.04). Moreover, Aarhus Green does not efficiently sensitize the production of singlet oxygen and it is photostable. Thus, tetrafluorination of the xanthene moiety in fluorescein derivatives can be a useful tool in the development of fluorescent probes.

Tuning the pKa of a pH Responsive Fluorophore and the Consequences for Calibration of Optical Sensors Based on a Single Fluorophore but Multiple Receptors

“…Sensing of chemical events using the optical response of dye molecules has been alluring since Sørensen defined colorimetric determination of pH. , Our ability to manipulate light and detect photons has made fluorescence the main workhorse of optical sensing, where the emission of a single molecule can communicate the concentration of an analyte in the local nanoenvironment. − Some responsive fluorescent probes operate using an inherent ratiometric change in their absorption or emission spectra. − These are hard to create and modulate, and it is limited to the inherent properties of the dye class. For instance, pH sensitive fluorescein derivatives have been made in excess, but they are all limited by fast photobleaching. , An alternative approach is to make a modular system, where the fluorescence of a dye is modulated by the state of a receptor. ,, This receptor must be a quencher of the fluorophore either when it is bound to the analyte or when it is free. ,, In this manner, an on/off responsive fluorescent probe can be made (Figure ). Most examples use photoinduced electron transfer PeT quenching receptors, although several other design principles have been demonstrated .…”

“…For instance, pH sensitive fluorescein derivatives have been made in excess, but they are all limited by fast photobleaching. 27,28 An alternative approach is to make a modular system, where the fluorescence of a dye is modulated by the state of a receptor. 9,29,30 This receptor must be a quencher of the fluorophore either when it is bound to the analyte or when it is free.…”

Biocompatible Microporous Organically Modified Silicate Material with Rapid Internal Diffusion of Protons

“…The benchmark for matrix materials for optical sensors has been set in sensors, where fluorescein was used as the active dye component; ,,− despite the inherently poor photostability of fluorescein. ,, The critical parameters when characterizing matrix materials for optical sensors are the response time of the sensor, the leakage of the dye, the stability of the signal, and finally the response to pH. − While leakage of the highly water-soluble fluorescein has not been completely removed, other more lipophilic dyes have been successfully encapsulated in sol–gels. , Here, we report on a new ORMOSIL matrix material. By covalent attachment of a polymerizable red-emitting pH-responsive dye bearing a silane group we document the properties of this new composite material.…”