Issue 7, 2009

Photolysis of an asymmetrically substituted diazene in solution and in the crystalline state

Abstract

In this work we study the product distribution in the steady state photolysis of a diazene, (1-biphenyl-4-yl-1-methyl-ethyl)-tert-butyl diazene, and a ketone, 2,4-bis(biphenyl-4-yl)-2,4-dimethyl-pentan-3-one, in the solid state and in solution. The two compounds yield 1-biphenyl-4-yl-1-methyl-ethyl (BME˙) radicals upon photolysis. The ketone yields two units of this radical, whereas the diazene yields one BME˙ and one tert-butyl radical. Product analysis of the two compounds in solution makes it possible to differentiate their origin from their corresponding geminate cages, and from the different encounter pairs in the case of the asymmetrically substituted diazene photolysis. In this way we obtain a complete reaction scenery for the diazene, a compound with interesting features as a radical photoinitiator and as a cage effect probe in fluid media. The reaction in cages containing two BME˙ radicals shows a decrease by a factor of 4 in the ratio of combination to disproportionation products upon going from the solid to the liquid phase. On the contrary, the reaction in cages containing a BME˙ and a tert-butyl radical shows a 30-fold increase in combination to disproportionation ratio in liquid compared to the crystal. We analyze the reasons for these differences considering the differences in the reactivity of the radicals and in cage rigidity.

Graphical abstract: Photolysis of an asymmetrically substituted diazene in solution and in the crystalline state

Supplementary files

Article information

Article type
Paper
Submitted
03 Feb 2009
Accepted
16 Mar 2009
First published
30 Mar 2009

Photochem. Photobiol. Sci., 2009,8, 961-969

Photolysis of an asymmetrically substituted diazene in solution and in the crystalline state

P. A. Hoijemberg, S. D. Karlen, C. N. Sanramé, P. F. Aramendía and M. A. García-Garibay, Photochem. Photobiol. Sci., 2009, 8, 961 DOI: 10.1039/B902272D

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