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N ‐Alkoxyheterocycles As Irreversible Photooxidants
Author(s) -
Wosinska Zofia M.,
Stump Faye L.,
Ranjan Rajeev,
Lorance Edward D.,
Finley GeNita N.,
Patel Priya P.,
Khawaja Muzamil A.,
Odom Katie L.,
Kramer Wolfgang H.,
Gould Ian R.
Publication year - 2014
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/php.12227
Subject(s) - chemistry , photochemistry , singlet state , fragmentation (computing) , excited state , singlet fission , triplet state , electron transfer , dissociation (chemistry) , molecule , atomic physics , physics , organic chemistry , operating system , computer science
Irreversible photooxidation based on N–O bond fragmentation is demonstrated for N ‐methoxyheterocycles in both the singlet and triplet excited state manifolds. The energetic requirements for bond fragmentation are studied in detail. Bond fragmentation in the excited singlet manifold is possible for ππ * singlet states with energies significantly larger than the N–O bond dissociation energy of ca 55 kcal mol −1 . For the nπ * triplet states, N–O bond fragmentation does not occur in the excited state for orbital overlap and energetic reasons. Irreversible photooxidation occurs in the singlet states by bond fragmentation followed by electron transfer. Irreversible photooxidation occurs in the triplet states via bimolecular electron transfer to the donor followed by bond fragmentation. Using these two sensitization schemes, donors can be irreversibly oxidized with oxidation potentials ranging from ca 1.6–2.2 V vs SCE . The corresponding N ‐ethylheterocycles are characterized as conventional reversible photooxidants in their triplet states. The utility of these sensitizers is demonstrated by irreversibly generating the guanosine radical cation in buffered aqueous solution.