PREPARATION OF NEW REDOX-ACTIVE QUATERNIZED POLY(QUINOLINIUM) AND POLY(ISOQUINOLINIUM) SALTS SHOWING VIOLOGEN-LIKE REDOX BEHAVIOR

Quaternization of poly(quinoline-4,7-diyl) (P(4,7-Q)) and poly(isoquinoline-1,4-diyl) (P(1,4-iQ)) with alkylating reagents (CH3I, (CH3O)2SO2, and (CH3)3CBr) affords the corresponding quaternary poly(quinolinium) and poly(isoquinolinium) salts. The degree of quaternization was in the range 60-95%. The polymers are electrically conducting, with a conductivity of 10(-6)-10(-7) S cm-1. Quaternized P(4,7-Q) is chemically and electrochemically redox active, and its cyclic voltammogram shows stable reversible redox peaks at ca. -0.5 and -0.75 V vs SCE, respectively. The color of the polymer changes from pale yellow to dark blue on reduction. On the other hand, quaternized P(1,4-iQ) does not give a stable redox cycle, presumably due to the instability of the cation radical formed by the reduction. Weitz-type two-step redox processes similar to those of 1,1'-disubstituted 4,4'-bipyridinium salts account for the redox reaction of quaternized P(4,7-Q).