A High-Spin and Helical Organic Polymer:  Poly{[4-(dianisylaminium)phenyl]acetylene}

A high-spin polyradical, poly{[4-(dianisylaminium)phenyl]acetylene} 1+, was synthesized as a π-conjugated polymer with an excess of the one-handed helical structure bearing stable aminium cation radicals. [4-(Dianisylamino)phenyl]acetylene (3) was synthesized and polymerized using [Rh(norbornadiene)Cl]2 in (R)-1-phenylethylamine, (S)-1-phenylethylamine, or triethylamine to produce the corresponding poly{[4-(dianisylamino)phenyl]acetylene} 1 (1(R)-PEA, 1(S)-PEA, and 1TEA). The positive and negative Cotton effects were observed at 270−450 nm for the polymers 1(R)-PEA and 1(S)-PEA, indicating that an excess of the one-handed helical polyacetylene backbone was induced by the polymerization using chiral solvents despite the achiral monomer. The oxidation of 1 with NOPF6 gave the corresponding aminium polyradicals 1+, and the circular dichroism (CD) spectrum was observed even after the oxidation of the helical polyradical 1(R)-PEA+. The SQUID and NMR shift measurements indicated a high-spin state of the polyradical at room temperature and a contribution of the well-regulated helical structure to the through-space interaction between the aminium cation radicals.