TY - JOUR
T1 - Role of Hydrogen Bonding in Photoinduced Electron-Proton Transfer from Phenols to a Polypyridine Ru Complex with a Proton-Accepting Ligand
AU - Lymar, Sergei V.
AU - Ertem, Mehmed Z.
AU - Lewandowska-Andralojc, Anna
AU - Polyansky, Dmitry E.
N1 - Funding Information:
We are grateful to Koji Tanaka for providing the Ru compounds and to Jacob Schneider, Norman Sutin, Gab́ or Mereńyi, and David Grills for their assistance and helpful discussions. This work was carried out at Brookhaven National Laboratory and supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences, & Biosciences under Contract DE-SC0012704.
PY - 2017/9/7
Y1 - 2017/9/7
N2 - Electron-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.
AB - Electron-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.
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U2 - 10.1021/acs.jpclett.7b01614
DO - 10.1021/acs.jpclett.7b01614
M3 - Article
C2 - 28792768
AN - SCOPUS:85029024384
VL - 8
SP - 4043
EP - 4048
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
SN - 1948-7185
IS - 17
ER -