jz7b01614_si_001.pdf (1.14 MB)
Role of Hydrogen Bonding in Photoinduced Electron–Proton Transfer from Phenols to a Polypyridine Ru Complex with a Proton-Accepting Ligand
journal contribution
posted on 2017-08-09, 00:00 authored by Sergei V. Lymar, Mehmed Z. Ertem, Anna Lewandowska-Andralojc, Dmitry E. PolyanskyElectron–proton
transfer (EPT) from phenols to a triplet
metal-to-ligand charge transfer (MLCT)-excited Ru polypyridine complex
containing an uncoordinated nitrogen site, 1(T), can
be described by a kinetic model that accounts for the H-bonding of 1(T) to phenol, 1(T) to solvent, and phenol to
solvent. The latter plays a major role in the kinetic solvent effect
and commonly precludes simultaneous determination of the EPT rate
constant and 1(T)-phenol H-bonding constant. A number
of these quantities previously reported for similar systems are shown
to be in error due to inconsistent data analysis. Control experiments
replacing either 1(T) by its structural isomer with a
sterically screened nitrogen site or phenol by its H-bonding surrogate,
trifluoroethanol, and the observation of negative activation enthalpies
for the overall reactions between 1(T) and phenols lend
support to the proposed model and provide evidence for the formation
of a precursor H-bonded complex between the reactants, which is a
prerequisite for EPT.