Table of Contents
Laser Chemistry
Volume 15, Issue 1, Pages 33-46
http://dx.doi.org/10.1155/1994/78595

Single Pulse Two-Photon Laser-Assisted Reduction of Benzophenone by Triethylamine to Form Excited Benzophenone Ketyl Radical

1Instituto de Química Física “Rocasolano”, CSIC, Serrano 119, Madrid 28006, Spain
2Instituto de Ciencia y Tecnología de Polímeros, CSIC, Juan de la Cierva 3, Madrid 28006, Spain

Received 20 July 1993

Copyright © 1994 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The pulsed laser photolysis at 308 nm of the benzophenone-triethylamine system in acetonitrile solution has been studied at room temperature. In the absence of triethylamine, phosphorescence emission of triplet benzophenone centred at 460 nm and with a lifetime of τ = 27 ± 1 μs is observed. Addition of triethylamine results in quenching of the benzophenone phosphorescence. Quenching rate constants KQ have been determined from emission intensifies and from experimental decay rate constants. The values KQ = (2.6 ± 0.3) × 109 M-1s-1 and KQ = (4.0 ± 0.5) × 109 M-1s-1, respectively, are obtained. On the addition of triethylamine, benzophenone phosphorescence diminishes and simultaneously a new emission with a fast decay rate and centred at 575 nm develops. This signal has been identified as emission from the excited benzophenone ketyl radical. A single pulse two-photon absorption mechanism responsible of the emission at 575 nm has been identified and a kinetic model based on this mechanism has been developed. The model gives a satisfactory quantitative account of both our experimental results and those reported in the literature (quantum yield of radical formation and behaviour of the system as photoinitiator).