This project has studied hydrogen atom transfer to four novel, base-appended radical cations:   10-(2-pyridyl)-10H-phenothiazinium, N,N-di-(4-bromophenyl)-N-(4-bromo-2'-pyridyl)aminium, 3-(2-pyridyl)-10-methylphenothiazium, and 3-(4-phenyl-2-quinolyl)-10-methylphenothiazinium.   Our recent studies have focused on these molecules abstracting a hydrogen atom from phenol and substituted phenols.  Transition states for hydrogen atom transfer have been located using the B972/6-31+g(d,p) model chemistry.  We have performed forward and reverse IRC calculations to verify the located transition states connect the proper products and reactants.  We have found the forward barrier for hydrogen-atom transfer to be 5-15 kcal/mol, in good agreement with experiments that have been performed in parallel.  Our calculated pseudo-first order rate constants of 100 � 1x107 s-1 for hydrogen-atom transfer are also in qualitative agreement with experiment.  The low barrier heights and large rate constants for these systems are partially explained by the formation of pre- and post-reaction hydrogen-bonded complexes between the reactants.

Computational study of concerted proton-electron transfer in base-appended radical cations

244th National Meeting (2012)

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