Photophysics of a series of efficient fluorescent pH probes for dual-emission-wavelength measurements in aqueous solutions.
This paper evaluates the 5-aryl-2-pyridyloxazole backbone to engineer donor-acceptor fluorescent pH probes after one- or two-photon absorption. Parent fluorophores, as well as derivatives that can be used to label biomolecules, can be easily obtained in good yields. These molecules exhibit a large one-photon absorption in the near-UV range, and a strong fluorescence emission that covers the whole visible domain. The 5-aryl-2-pyridyloxazole derivatives also possess significant cross sections for two-photon absorption. Upon pyridine protonation, large shifts were observed in the absorption spectra after one- and two-photon excitation, as well as in the emission spectra. This feature was used to measure the pK(a) of the investigated compounds that range between 2 and 8. In most of the investigated derivatives, the pK(a) increased upon light excitation and protonation exchanges took place during the lifetime of the excited state, as shown by phase-modulation fluorometry analysis. Several 5-aryl-2-pyridyloxazole derivatives are suggested as efficient probes to reliably measure the pH of aqueous solutions by means of ratiometric methods that are dependent on fluorescence emission.
Charier
Sandrine
S
Département de Chimie (C.N.R.S. U.M.R. 8640), Ecole Normale Supérieure, 24, rue Lhomond, 75231 Paris Cedex 05, France.
Ruel
Odile
O
Baudin
Jean-Bernard
JB
Alcor
Damien
D
Allemand
Jean-François
JF
Meglio
Adrien
A
Jullien
Ludovic
L
Valeur
Bernard
B
D005456:Fluorescent Dyes / Q000138:chemical synthesis* / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D010080:Oxazoles / Q000737:chemistry*; D012996:Solutions; D013056:Spectrophotometry, Ultraviolet
D005456:Fluorescent Dyes; D010080:Oxazoles; D012996:Solutions