Polymerization of isomeric N-(4-substituted benzylidene)-4-ethynylanilines and 4-substituted N-(4-ethynylbenzylidene)anilines by transition metal catalysts: preparation and characterization of new substituted polyacetylenes with aromatic Schiff base type

N-(4-substituted benzylidene)-4-ethynylanilines R–C6H4–CHN–C6H4–CCH, where R=Me, t-Bu, F, Br, CN, NO2, Me2N and –CC–SiMe3 and isomeric 4-substituted N-(4-ethynylbenzylidene)anilines R–C6H4–NCH–C6H4–CCH, where R=Me, t-Bu, F, Br, I, CN, NO2 and –CC–SiMe3 were polymerized using (i) [Rh(cod)OCH3]2 [(cod)=η4-cyclooctadiene] in THF, (ii) Mo(CHCPhMe2) (N–C6H3–iPr2-2,6)[O–CMe(CF3)2]2 in aromatics, (iii) PdCl2 in DMF. All catalysts tested exhibited high tolerability towards –CH=N– group (confirmed also by the in situ 1H NMR study) providing polyacetylenes with aromatic Schiff base type pendant groups. Positive correlation between acidity of ethynyl group and monomer polymerizability was found for Rh catalyst. Depending on catalyst, molecular weight of polymers decreases in the series: Rh (Mw=45 000–300 000)>Mo (Mw=13 000–40 000)>Pd (Mw about 5000). The main chain cis double bond content and the microstructure uniformity of polymer were found to decrease in the same order. In THF, all polymers prepared exhibited fluorescence (λmax=500–550 nm) considerably red-shifted in comparison with their parent monomers.