ELECTRON-TRANSFER-INDUCED DEAZATIZATION OF CYCLIC AZO DERIVATIVES OF QUADRICYCLANE AND NORBORNADIENE

The photosensitized oxidation of two cyclic azoalkane derivatives (Azo -Q, Azo-N) of quadricyclane (Q) and norbomadiene (N) has been investig ated using steady-state and laser flash photolysis techniques as well as chemically induced dynamic nuclear polarization (CIDNP). irradiatio n of acetonitrile solutions of 9,10-dicyanoanthracene (DCA), 2,6,9,10- tetracyanoanthracene (TCA), or chloranil (Chl) in the presence of Azo- Q results in rapid and efficient deazatization to afford N. Similar ir radiation of DCA, TCA, and Chl in the presence of Azo-N yields N and Q . CIDNP experiments reveal that polarized N is formed as a cage produc t in the Chl sensitized photolysis of Azo-Q while polarized N and Q ar e both formed as cage products from Azo-N. The results are consistent with competitive fragmentation of Azo-N-.+ to N-.+ and Q(.+), and sele ctive deazatization of Azo-Q(.+) to N-.+. irradiation of 1-cyanonaphth alene in the presence of Azo-Q or Azo-N affords Q and/or N in chemical yields similar to those obtained from direct and naphthalene sensitiz ed irradiations, indicative of singlet energy transfer quenching. Bimo lecular rate constants for quenching by Azo-N and Azo-Q were determine d by steady-state fluorescence methods for singlet sensitizers, or by laser flash photolysis (LFP) for (3)Chl.