Synthesis and Magnetic Property of Poly[bis(4-methoxyphenyl)aminiumacetylene]s

Poly[bis(4-methoxyphenyl)aminiumacetylene]s 1 + were designed and synthesized as a π-conjugated polymer bearing multiple aminium radicals. Bis(4-methoxyphenyl)aminoacetylene and 1-methyl-2-bis(4-methoxyphenyl)aminoacetylene were synthesized and polymerized with a metathesis catalyst to yield poly[bis(4-methoxyphenyl)aminoacetylene] 1a and poly[1-methyl-2-bis(4-methoxyphenyl)aminoacetylene] 1b , respectively. The oxidation of 1 with SbCl 5 gave the corresponding aminium polyradicals 1 + . The introduction of a methyl group onto the polyacetylene backbone in 1b + significantly enhanced the chemical stability or life-time of the poly(aminium radical). The high-spin ground state with an average S (spin quantum number) = 4/2 for 1b + was proven by magnetic susceptibility, magnetization, and ESR measurements.