Alternating, all‐<i>trans</i> polyenynes: Model compounds for poly(diacetylene)s with defined conjugation length

Abstract

Abstract The syntheses of polyenynes as model compounds for poly(diacetylene)s (PDAs) are described. Variation of properties (UV–VIS, Raman, NMR and bond geometries) as a function of the chain length was investigated. After extrapolation to infinite chain length these data were compared to those for PDAs. From UV–VIS spectra a value of λ = 551 nm (2.25 eV) was calculated corresponding to the electronic transition of a single polyenyne chain. This energy is located at the low energy end of a yellow PDA solution spectrum. From Raman scattering v (CC) = 2108–2128 cm −1 and v (CC) = 1505–1532 cm −1 were calculated after extrapolation. Similarly sp‐C 13 C NMR data yielded a shift of δ = 100 ppm. These data are almost identical to data known for yellow PDA solutions. Bond geometries are almost identical to those of poly(diacetylene)s and theoretical data.