Synthesis of Phenyl Ethynylene Coupled Biradicals and Polyradicals Based on Galvinoxyl

Abstract

A conjugated polyradical with galvinoxyl groups, poly{1-[(3-5-di-tert-butyl-4-hydroxyphenyl)(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)methyl]phenyl-3,5-diethynyl}-co-3,5-[1-(dodecyl)benzoate], poly(G), and two conjugated oligoradicals, 1,4-bis{[(3-5-di-tert-butyl-4-hydroxyphenyl)(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dienylidene) methyl]phenyl)4-ethynyl}-2,5-di(dodecyloxy)benzene (G-3 p -G), and 1,3-bis{[(3-5-di-tert-butyl-4-hydroxyphenyl)(3,5-di-tert-butyl-4-oxocyclohexa-2,5-dienylidene)methyl]phenyl)4-ethynyl}benzene (G- pmp -G) were synthesized by a Heck-Sonogashira route. The molecules were investigated in dilute solution by UV-Vis and ESR spectroscopy. In the solid state for G-3 p -G and poly(G), both the ESR spectra and the SQUID magnetometry suggest the set up of magnetic interactions between the radicals. On solid state powders SQUID characterization of poly(G) shows a continuous decrease of χT at low temperature, which is characteristic of antiferromagnetic interactions; while for G-3 p -G a competition between weak ferromagnetic and antiferromagnetic interactions is observed.

Key words

phenyl-ethylene - cross-coupling - Heck Reaction - radicals

References

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22

Wautelet, P.; Turek, P.; Le Moigne, J.; André J. J.; Bieber, A. J. Org. Chem. 2002, submitted.

26

The magnetic properties of G- pmp -G have not been studied, due to the rapid decomposition of the radicals even in the solid state.

29

The phenylene-ethynylene unit with similar connectivity has been shown to be an efficient coupler at a distance of 20 Å between imino-nitroxide radical derivatives. [3] It is assumed here, that the through bond spin exchange should set up as well at the same distance range (ca. 17-20 Å).

32

A summary of the route to G- pmp -G.