Use of tertiary solvent mixtures to study solvent effects

Description

Photoinduced electron transfer (PET) plays an important role in many areas of chemistry. The physical properties of the solvent influence the rate constant of PET reactions in many ways. Dielectric constant ε and refractive index n influence the solvent dipole reorientations and contribute to the activation energy of the ET reactions [1]. Electron-transfer kinetics is also influenced by diffusion and therefore by the solvent viscosity η. Unfortunately, most measurements published use different solvents in a not consequent way [2]. Measurements in polar and nonpolar solvents are compared together with high and low viscous ones.
We present here the results of experiments made in a series of solvent mixtures comprising propyl acetate (PA), butyronitrile (BN), and diethyl phthalate (DEP), spanning a wide range of dielectric constants, keeping the n and η constant [3]. The major components PA and BN have been purified carefully over Al2O3. We used the PET reaction of singlet excited pyrene and indole whose solvent dependence is already described in the literature [2]. Quenching rate constants were obtained from Stern-Volmer plots based on both static and dynamic (TCSPC) measurements. The ΔG-dependence of ln kq is reported for the solvent mixtures and compared with results reported in pure organic solvents [2].

[1] M. Berghold, J. Bächle, S. Landgraf, G. Grampp, ChemPhysChem, 18,128 (2017).
[2] H. A. Montejano, J.J. Cosa, H.A. Garrera, C.M. Previtali, J. Photochem. Photobiol. A Chem. 86,115 (1995).
[3] A. Wankmüller, M. Berghold, S. Landgraf, J. Mol. Liquids, 333, 115880 (2021).¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬¬

Period	19 Sept 2022
Event title	28. Lecture Conference on Photochemistry
Event type	Conference
Location	Düsseldorf, Germany, North Rhine-WestphaliaShow on map
Degree of Recognition	International