Electrochromic modulation of excited-state intramolecular proton transfer: the new principle in design of fluorescence sensors (original) (raw)
Related papers
The Journal of Physical Chemistry A, 2003
Picosecond time-resolved fluorescence spectroscopy has been applied to the studies of excited-state intramolecular proton transfer (ESIPT) dynamics in two 4′-(dialkylamino)-3-hydroxyflavone derivatives (unsubstituted and substituted at the 6-position) in ethyl acetate and dichloromethane. In all the studied cases, the fluorescence decay kinetics of both short-wavelength normal (N*) and long-wavelength tautomer (T*) bands can be characterized by the same two lifetime components, which are constant over the all wavelength range of the emission. In the meantime, the preexponential factor of the short-lifetime component changes its sign, being positive for the N* and negative for the T* emission band. Moreover, the two preexponential factors of the T* emission decay are the same in magnitude but opposite in sign. These features are characteristic of a fast reversible two-state ESIPT reaction. Reconstruction of time-resolved spectra allows observing the evolution of these spectra with the appearance, rapid growth, and stabilization (in less than 200 ps) of the relative intensities of the two emission bands. A detailed kinetic model was applied for the analysis of these data, which involved the determination of radiative and nonradiative decay rate constants of both N* and T* forms and of forward and reverse rate constants for transitions between them. We show that ESIPT reaction in the studied conditions occurs on the scale of tens of picoseconds and thus is uncoupled with dielectric relaxations in the solvent occurring at subpicosecond times. Moreover, the radiative and nonradiative deactivation processes were found to be much slower than the ESIPT reaction, suggesting that the relative intensities of the two emission bands are mainly governed by the ESIPT equilibrium. Therefore, both electrochromic and solvatochromic effects on the relative intensities of the two emission bands in 4′-(dialkylamino)-3-hydroxyflavones result from the shifts in the ESIPT equilibrium.
Russian Journal of Physical Chemistry A, 2009
The influence of excitation conditions, temperature, and fluorescence quencher on the properties of 3 hydoxyflavone excited states is considered. Two band fluorescence spectra of 3 hydroxyflavone formed in excitation by electromagnetic radiation in the region of the S 1 and S 2 absorption bands over the tempera ture range 20-80°C were recorded and analyzed. The TEMPO spin quencher was used as an excited state quencher. An analysis of the fluorescence parameters showed that solution heating from room temperature to 60°C increased the rate of proton transfer by 1.24 times at standard excitation into the main absorption band. The rate increased still more rapidly (by 6.9 times) in excitation into the second absorption band. The pres ence of the quencher caused a decrease in the yields of both fluorescence bands according to the diffusion mechanism and a noticeable growth in the rate of proton transfer. The latter increased by 1.16 times at room temperature and by 1.25 times at 80°C. The corresponding changes were more substantial, especially at ele vated temperatures, if the second singlet band was excited. They then amounted to 1.24 and 3.5 times over the same temperature range.
Excited state proton transfer fluorescence of 3-hydroxyflavone in model membranes
Spectrochimica Acta Part A-molecular and Biomolecular Spectroscopy, 1997
3-Hydroxyflavone (3HF), the basic structural moiety of an important group of naturally occurring, biologically active flavonoids, has attracted extensive attention for its intramolecular excited-state proton-transfer (ESPT) and dual fluorescence characteristics. We report here, for the first time, its fluorescence (emission, excitation, polarization anisotropy and lifetime) behaviour in model membranes consisting of small, unilamellar liposomes of synthetic phosphatidylcholine (dimyristoyl phosphatidylcholine (DMPC) and dipalmitoyl phosphatidylcholine (DPPC)). The emission spectrum is conspicuously dominated by the ESPT tautomer fluorescence band. This result, along with other relevant data, indicates that the molecules are embedded in the lipid bilayer matrix facing environments where external H-bonding perturbation effects are minimized. The anisotropy (Y) versus temperature (r) profiles dramatically reveal the thermotropic gel-liquid crystalline phase transition properties of the phospholipids. signifying a novel application of the intrinsic (tautomer) fluorescence of 3HF. 0 1997 Elsevier Science B.V.
Chemical Physics Letters, 2012
Excitation wavelength dependence of photo-induced intramolecular excited state proton transfer reaction of 4'-N,N-diethylamino-3-hydroxyflavone in various liquids has been investigated by steady-state and time-resolved fluorescence measurements. It was found that the relative fluorescence intensity of the tautomer excited state to that of the normal excited state significantly decreases in ionic liquids with changing the excitation wavelength from 380nm to 470nm. The initial proton transfer rate excited at 470 nm was different from that obtained at 400 nm excitation. The excitation wavelength dependence was discussed in relation with the inhomogeneous distribution of the solute in the ionic liquids.
Red-edge excitation effect in intramolecular proton transfer in flavonols
Proceedings of SPIE - The International Society for Optical Engineering, 2002
To investigate of 4'-diethylamino (FET) and 4'-(15-azacrown- 5) (FCR) derivatives of 3-hydroxyflavone in binary solvents and erythrocyte ghosts, we used the red-edge excitation spectroscopy. The results obtained prove the existence of spectral heterogeneity of flavonols in the studied systems. The effect manifests itself in the dependence of the efficiency of excited-state intramolecular proton transfer on the excitation frequency.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 1996
The excited-state proton transfer and dual emission behaviour of 3-hydroxyfiavone (3HF) have been investigated in reverse micelles of sodium bis(2-ethylhexyl) sulphosuccinate (AOT)/n-heptane at different values of water to surfactant molar ratio (Wo). The green tautomet emission (~i .... ~ 524 nm) and blue-violet normal emission (2 ...... 400 nm) originate from two different ground state populations of 3HF molecules, which are located respectively in the apolar phase and at the interphase of the reverse micelles, proximal to the AOT head groups. With increasing Wo the relative yield of the green emission band is enhanced with a concomitant decrease in that of the blue-violet emission. This is interpreted in terms of the population of 3HF molecules which are initially located in the interfacial region proximal to the polar head groups being "pushed" out into the apolar phase, where external hydrogen bonding perturbations are minimized.
Sensors and Actuators B: Chemical, 2010
A 3-hydroxyflavone derivative (L) was synthesized and its red-emitting ternary complex, composed of Zr-EDTA and L, was developed as a highly selective and sensitive fluorescent sensor for ratiometric detection of F − in aqueous solution with a physiological pH region. Fluorescent intensity at 610 nm of Zr-EDTA-L increased with addition of F − , concomitantly the emission at 470 nm decreased together with an obvious color change by naked eyes. However, other competitive anions such as Cl − , Br − , I − , NO 3 − , HSO 4 − , AcO − and H 2 PO 4 − did not induce any distinct changes in fluorescence spectra. The results can be reasonably interpreted by the inhibition of excited-state intramolecular proton transfer (ESIPT), which arises from the ligand exchange of L coordinated to Zr-EDTA and fluoride anions.