Photophysical Properties and Photosubstitution and Photoredox Reactions of Aromatic Nitro Compounds

Abstract

Orientation rules for photochemical nucleophilic substitutions are deduced from intramolecular photoreactions of some bichromophoric chain molecules, p-O2NC6H4O(CH2)(n)NHC6H5 The lower homologues undergo photochemical nucleophilic substitutions which can be classified as a Smiles-type photorearrangement. The photochemistry of this type of bifunctional chain species depends upon the methylene chain length. When the chain length is sufficiently long, the photorearrangement is totally forbidden. Photoredox reactions are the only accessible reaction processes for the higher homologues. The photoredox reaction consisting of cage and escape pathways is modulated by an external magnetic field. The magnetic field effects on the end product distribution are due to changes in the intersystem crossing rate induced by hyperfine interaction within biradical intermediates.