Synthesis And Anion Recognition Ability Of Novel Helical Poly (Phenylacetylene) Derivatives

In this work, three novel substituted poly(phenylacetylene) derivatives containing different amino acids and amide/urea group with the function of anion recognition were synthesized,and optical activities and anion recognition abilities of the polymers were also investigated.Boc-L-alanine, Boc-L-valine, aniline, 4-phenylsemicarbazide and 4-acetylene benzoic acid were used as raw materials, and three novel phenylacetylene derivatives (monomer 1,2,3) with different amino acids and amide/urea were obtained via amidation reaction,deprotection of Boc group and amidation reaction, respectively. The phenylacetylene monomers were polymerized in DMF using a rhodium catalyst to yield three kinds novel poly(phenylacetylene) derivatives (Poly 1, 2, 3). The structure of monomers and polymers were characterized by IR,1H NMR and GPC. The results showed that the main chain of all the polymers possessed cis-transoid configuration.The optical activities of polymers and monomers were tested by the specific rotation and circular dichroism (CD), and the influence of solvents and temperature on optical activities and helical conformation were studied .The results revealed that the synthetic polymers took predominantly one-handed helical structures. It is found that the intensity of Cotton effect of three polymers increased with the decreasing of temperature. Also, the stereoregularity and thermodynamic stability increased at lower temperature and high temperature destroyed helical conformations slightly. Meanwhile, Cotton effect of Poly 1 was weakened with the increase of methanol content. The results indicated that the hydrogen bonds in the polymers played an important role in the formation of helical structure which affected by the addition of methanol.The anion recognition abilities of the three novel poly(phenylacetylene) derivatives were evaluated using a series of tetra-n-butylammonium salts in DMF or DMAc,respectively.Upon the addition of the corresponding anions, solutions of the sensors caused drastic colorimetric response, which provided a rough discrimination of the anions, along with obvious changes in the circular dichroism (CD), UV-vis spectrophotometric titrations and fluorescence spectrometer. Poly 1 exhibited good selectivity to F- and OH' by naked eyes, while Poly 3 has sensing ability to the anion with strong basicity F- by naked eyes. The 1H NMR titration revealed that binding site-anion interaction was based on the hydrogen-bonding complex formation between the amide or urea group and the anions.