An electrocyclic strategy to poly(triarylmethyl radical) polymers: Potential organic ferromagnets
Recent interest in organic ferromagnetism has been stimulated by the idea that large poly(triarylmethyl radical) polymers in which the radical centers are connected by [open quotes]meta[close quotes]-aryl groups may possess ferromagnetic properties. However, synthesis of these polyradicals has been limited by stepwise methods that are unsuitable for the preparation of large polymers. This limitation represents a primary challenge confronting the field. The authors have developed the first polymeric strategy to poly (m-triarylmethyl radical) precursors that involves an electrocyclic formation of the [open quotes]meta[close quotes]-substituted triarylmethyl chloride repeating unit from a polypropynol precursor. Poly[(E)-6-[beta]-chloroethenyl-1,3-phenylene-1-phenylpropynol-1,3-ylene] was prepared by palladium-catalyzed coupling of a bifunctional acetylene-aryl iodide monomer. The stable polymer reacted with thionyl chloride to form an unstable polychloroallene intermediate that underwent an electrocyclic conversion to the polyradical precursor, poly(1-chloro-2,7-naphthalenechlorobenzylidene). The reduced polyradicals exhibited properties of radical-radical coupling, and preparation of a second generation polymer that would overcome this problem has been initiated. The polymeric strategy was based on model studies that showed that (E)-3-(2-[beta]-chloroethenylphenyl)-1,1-diphenylpropynol, when converted to the corresponding chloroallene with thionyl chloride, underwent an electrocyclic conversion to [beta]-(1-chlornaphthyl)diphenylmethyl chloride. The strategy expanded upon the use of triarylpropynes as precursors to triarylmethyl chlorides, and extension of both approaches to higher analogs was demonstrated with dimeric systems. The electrocyclic processes were found to occur only for the trans-vinyl chlorides; the cis-isomers were found to undergo an alternative concerted cyclization to benzofluorene products.
- Research Organization:
- Duke Univ., Durham, NC (United States)
- OSTI ID:
- 7015593
- Resource Relation:
- Other Information: Thesis (Ph.D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
36 MATERIALS SCIENCE
ALKYNES
POLYMERIZATION
ARYL RADICALS
FERROMAGNETISM
METHYL RADICALS
ALKYL RADICALS
CHEMICAL REACTIONS
HYDROCARBONS
MAGNETISM
ORGANIC COMPOUNDS
RADICALS
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