Precise synthesis of monosubstituted polyacetylenes using Rh complex catalysts. Control of solid structure and pi-conjugation length

Stereospecific polymerization of monosubstituted acetylenes was successfull y performed using a Ph complex, [Rh(norbornadiene)Cl](2), as a catalyst, an d the resulting polyacetylenes were characterized in detail by H-1 NMR, ESR , laser Raman, diffuse reflective UV, and wide-angle X-ray diffraction. The Rh complex was found to yield selectively the cis-transoid isomer even at room temperature in high yields when alcohol or triethylamine was used as t he solvent. Additionally, the resulting cis-polyacetylenes were found to fo rm a pseudohexagonal, columnar self-assembly or superstructure. Further com pression of the cis-polymers induced cis-trans isomerization even at room t emperature under vacuum, breaking rotationally the cis-C=C bonds and, thus, giving pi-radicals as the origin of magnetic properties.