title: Synthesis, helicity, and chromism of optically active poly(phenylacetylene)s carrying different amino acid moieties and pendant terminal groups.
abstract: Functional phenylacetylene derivatives containing l-alanine and l-leucine moieties with chiral menthyl and achiral n-octyl terminal groups {HC[triple bond]C-C6H4-p-CONHCH(R)CO2R': R = CH3, R'= (-)-(1R,2S,5R)-menthyl [1(-)]; R = CH2CH(CH2)3, R' = (-)-(1R,2S,5R)-menthyl [2(-)]; R'= CH2CH(CH2)3, R' = (+)-(1S,2R,5S)-menthyl [2(+)]; R'= CH2CH(CH2)3, R' = (CH2)7CH3 (2o)} are synthesized. Polymerizations of the acetylene monomers are effected by organorhodium catalysts, giving corresponding polymers P1(-), P2(-), P2(+), and P2o of high molecular weights (Mw up to 1.2 x 10(6)) in high yields (up to 89%). The polymers are thermally stable (Td >or= 300 degrees C) and soluble in common organic solvents. The polymer structures are characterized by IR, NMR, UV, and CD spectroscopies. Intense CD signals are observed in the visible spectral region, indicating that the polymer chains are taking a helical conformation with an excess of preferred handedness. The backbone conjugation and chain helicity of the polymers can be tuned by changing their molecular structures [(a)chiral pendant groups] and by applying external stimuli (solvent and pH). Addition of trifluoroacetic acid to the polymer solutions decreases their molar ellipticities and enhances their backbone conjugations, inducing a halochromism with a continuous and reversible color change (yellow <==> red).
authors.affiliation: Department of Chemistry, The Hong Kong University of Science & Technology, Clear Water Bay, Kowloon, Hong Kong, China.
authors.forename: Lo Ming
authors.initials: LM
authors.lastname: Lai
authors.forename: Jacky W Y
authors.initials: JW
authors.lastname: Lam
authors.forename: Anjun
authors.initials: A
authors.lastname: Qin
authors.forename: Yongqiang
authors.initials: Y
authors.lastname: Dong
authors.forename: Ben Zhong
authors.initials: BZ
authors.lastname: Tang
mesh_terms: D000114:Acetylene / Q000737:chemistry*; D000596:Amino Acids / Q000737:chemistry*; D015394:Molecular Structure; D012995:Solubility; D013057:Spectrum Analysis / Q000379:methods; D013237:Stereoisomerism
chemical_list: D000596:Amino Acids; D000114:Acetylene