Direct Experimental Evidence for Alkoxyl Radicals Reacting as Hydrogen Atom Donors toward Pyridines.

Nanosecond transient absorption spectroscopy was used to generate ethoxyl radicals and demonstrate that they react with 2,6-lutidine and 4-phenylpyridine to give the corresponding -hydropyridinyl radicals-products of a novel hydrogen atom transfer from the alkoxyl radical to the nitrogen atom of the substituted pyridines. Nanosecond kinetics show that both reactions are rapid ( ∼ 10 M s) in acetonitrile at room temperature. Rate constants measured for reaction of the ethoxyl vs.

Emissive Organic Exciplexes in Water.

Unlike numerous known examples of exciplexes (products of charge formation reactions), we reported recently that cationic exciplexes (products of charge shift reactions) can be formed with N-methylisoquinolinium as an excited acceptor and alkyl benzene donors. We have now synthesized five intramolecular analogues (isoquinolinium linked by a trimethylene tether to alkyl benzenes) that proved to be well suited to demonstrating that emissive exciplexes can be formed in water from purely organic components. Three conformers (anti, gauche, and folded) leading to electron transfer were identified using a combination of absorption spectroscopy, fluorometry, and time-correlated single photon counting.