536976-48-4Relevant articles and documents
The effect of phenyl substituents on the activity of some zirconocene photoinitiators
Polo, Eleonora,Barbieri, Andrea,Traverso, Orazio
, p. 324 - 330 (2007/10/03)
In this paper we report the synthesis of several unbridged zirconocenes, 1a-c, 2 and 5, each bearing a phenyl substituent in the 2-position of the cyclopentadienyl ring. We also report their photochemical behaviour and we compare the results with those obtained with the corresponding unsubstituted metallocenes 3a-c and 4. Study of their electronic spectra and EPR/spin trapping experiments showed photogeneration of ligand- and zirconium-centred radicals, thus making these complexes suitable as photoinitiators for radical polymerisation processes. The substitution of the hydrogen atom in the 2-position with a phenyl group had positive effects both on the absorption coefficients, improving the light absorption efficiency, and on the reaction yields of tert-butyl acrylate polymerisation. These results can be explained in terms of the combined effects of greater persistence of the radical in solution and/or increased efficiency of the radical in initiating the polymerisation process. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.
