74209-12-4Relevant academic research and scientific papers
Synthesis, characterization, photophysics and photochemistry of pyrylogen electron transfer sensitizers
Clennan, Edward L.,Liao, Chen
, p. 344 - 357 (2014)
A series of new dicationic sensitizers that are hybrids of pyrylium salts and viologens has been synthesized. The electrochemical and photophysical properties of these "pyrylogen" sensitizers are reported in sufficient detail to allow rationale design of new photoinduced electron transfer reactions. The range of their reduction potentials (+0.37-+0.05 V vs SCE) coupled with their range of singlet (48-63 kcal mol-1) and triplet (48-57 kcal mol-1) energies demonstrate that they are potent oxidizing agents in both their singlet and triplet excited states, thermodynamically capable of oxidizing substrates with oxidation potentials as high as 3.1 eV. The pyrylogens are synthesized in three steps from readily available starting materials in modest overall 11.4-22.3% yields. These sensitizers have the added advantages that: (1) their radical cations do not react on the CV timescale with oxygen bypassing the need to run reactions under nitrogen or argon and (2) have long wavelength absorptions between 413 and 523 nm well out of the range where competitive absorbance by most substrates would cause a problem. These new sensitizers do react with water requiring special precautions to operate in a dry reaction environment. Hybrids of pyrylium salts and viologens photochemically generate radical-cation/radical-cation pairs with substantial intra-ion repulsion that increases the rate constant of separation, kSEP, and competitively inhibits energy wasting return electron transfer. These first representatives of dicationic charge-shift sensitizers generate radical cations that do not react with oxygen on the CV timescale and absorb between 413 and 523 nm well outside the range where competitive absorbance by most substrates would cause a problem.
Pyrylogens: Synthesis, structural, electrochemical, and photophysical characterization of a new class of electron transfer sensitizers
Clennan, Edward L.,Liao, Chen,Ayokosok, Erambo
, p. 7552 - 7553 (2008/12/22)
The synthesis and photophysical properties of a new series of dicationic electron transfer sensitizers have been reported. These new materials, pyrylogens, are hybrids of pyrylium cations and Viologen dications. Electron transfer reactions of neutral orga
