Polybinaphthyls incorporating chiral ( R) or ( S)-2,2′-binaphthyland oxadiazole moieties by Stille reaction

Abstract

Chiral polymers P- 1 and P- 2 were prepared by the polymerization of ( R)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl (( R)- M- 1) and ( S)-3,3′-diiodo-2,2′-bisbutoxy-1,1′-binaphthyl (( S)- M- 1) with 2,5-bis[(4-tributylstannyl)phenyl]-1,3,4-oxadiazole ( M- 2) via Pd(PPh 3) 4 catalyzed Stille coupling reaction. 1,3,4-Oxadiazole unit not only has high electron affinity, high thermal and oxidative stability, but also serves as a good chromophore. Polymers have strong blue fluorescence due to the efficient energy migration from the extended π-electronic structure of the polymers to the chiral binaphthyl core and can be expected to have potential application in the materials of fluorescent sensors. Circular dichroism (CD) spectra of polymers P- 1 and P- 2 are almost identical except that they gave opposite signals at each wavelength. The long wavelengths CD effect of P- 1 and P- 2 can be regarded as the more extended conjugated structure in the repeating unit and a high rigidity of the polymer backbone.