Signaling Recognition Events with Fluorescent Sensors and Switches.

Fluorescence quenching rate constants, kq, ranging from 106 to 2 × 1010 M−1 sec−1, of more than 60 typical electron donor-acceptor systems have been measured in de-oxygenated acetonitrile and are shown to be correlated with the free enthalpy change, ΔG23, involved in the actual electron transfer process

in the encounter complex and varying between + 5 and −60 kcal/mole. The correlation which is based on the mechanism of adiabatic outer-sphere electron transfer requires ΔG≠23, the activation free enthalpy of this process to be a monotonous function of ΔG23 and allows the calculation of rate constants of electron transfer quenching from spectroscopic and electrochemical data.

A detailed study of some systems where the calculated quenching constants differ from the experimental ones by several orders of magnitude revealed that the quenching mechanism operative in these cases was hydrogen-atom rather than electron transfer.

The conditions under which these different mechanisms apply and their consequences are discussed.

Kinetics of Fluorescence Quenching by Electron and H‐Atom Transfer

This review focuses on classifying different types of long wavelength absorbing BODIPY dyes based on the wide range of structural modification methods that have been adopted, and on tabulating their spectral and photophysical properties. The structure–property relationships are analyzed in depth with reference to molecular modeling calculations, so that the effectiveness of the different structural modification strategies for shifting the main BODIPY spectral bands to longer wavelengths can be readily compared, along with their effects on the fluorescence quantum yield (ΦF) values. This should facilitate the future rational design of red/NIR region BODIPY dyes for a wide range of different applications.

Structural modification strategies for the rational design of red/NIR region BODIPYs

CHAPTER 3 – Photosensitized Oxidation and Singlet Oxygen: Consequences in Biological Systems

Luminescent lanthanide sensors for pH, pO2 and selected anions

FLUORESCENCEt Some years ago, while investigating fluorescence quenching of aromatic hydrocarbons (A) by typical electron donors (D), like anilines, we observed1 a broad structureless emission band about 5000 cm1 to the red of the fluorescence of the aromatic hydrocarbon of normal structure. This anomalous fluorescence, as shown in Figure 1, increases in intensity with increasing donor concentration at the expense of the fluorescence intensity of the hydrocarbon, thereby following the same Stern—Volmer-type relation as does the well known excimer fluorescence, e.g. in the case of pyrene2. Extrapolation to infinite donor concentration gives the dashed spectrum (cf. Figure 1) which

/pdf/electron-transfer-and-complex-formation-in-the-excited-state-4r2z0f6mjo.pdf

A. Weller

Papers

Electron-transfer and complex formation in the excited state