Conjugated Biradical Intermediates: Spectroscopic,Kinetic, and Trapping Studies of 2,2-Dimethyl-1,3-perinaphthadiyl |
| |
Authors: | Erich Hasler Ernst Gassmann Jakob Wirz |
| |
Institution: | Institut für Physikalische Chemie der Universität Basel, Klingelbergstrasse 80, CH–4056 Basel |
| |
Abstract: | The biradical 2,2-dimethyl-1,3-perinaphthadiyl ( a ) was generated from two different precursors, the naphthocyclopropane 1 and the azo compound 2 , and from each by three different pathways (pyrolysis, direct photolysis, and triplet sensitization, Scheme 1). The combined evidence from flash photolysis, low-temperature spectroscopy, and product analyses provides a detailed mechanistic picture of the formation and decay of this reactive intermediate which is persistent at 77 K in the triplet ground state (3 a ) and rather long-lived (400 μs) at room temperature. When formed in its lowest singlet state (1 a ), the biradical is too short-lived to undergo intersystem crossing to 3 a or bimolecular reactions. Thus, 3 a is formed exclusively from the excited triplet state of the precursor compounds, 3 1 * or 3 3 *. The monomolecular decay of 3 a is retarded by the spin barrier; 3 a initiates the polymerization of acrylonitrile and is trapped by 3O2. |
| |
Keywords: | |
|
|