Synthesis and chiroptical properties of a helical poly(phenylacetylene) bearing optically active pyrene pendants

Abstract

A novel poly(phenylacetylene) derivative bearing optically active pyrene moieties as the pendant groups (poly-(R)-1) was prepared by the polymerization of the corresponding monomer (R)-1 in the presence of a rhodium catalyst, and its chiroptical property was investigated. Poly-(R)-1 exhibited an induced circular dichroism (ICD) in the polymer backbone region due to the predominantly one-handed helical conformation. The ICD pattern dramatically changed and was accompanied by inversion of the Cotton effect sign in response to a change in the temperature and solvent, indicating that poly-(R)-1 underwent a helix-helix transition in response to the external stimuli.

Influence of Helical Structure on Chiral Recognition of Poly(phenylacetylene)s Bearing Phenylcarbamate Residues of L‐Phenylglycinol and Amide Linage as Pendants

“…PPA-1 , PPA-2 , PPA-3 , PPA-4 were synthesized in DMF using the monomers solution in DMF with the concentration of 0.3 M. Figure shows the 1 H NMR spectra of PPA-1 , PPA-2 , PPA-3 , PPA-4 in DMSO‐ d 6 at 80°C. The characteristic signals due to the main chain proton appeared at 5.55–5.70 ppm, suggesting the formation of cis‐transoidal configuration of the polymer main chains . As shown in Figure , the N‐H proton signals assigned to the phenylcarbamate residues with electron‐withdrawing substituents (chloro group) in PPA-1 , PPA-2 shifted downfield compared to those assigned to the phenylcarbamate residues with electron‐donating substituents (methyl group) in PPA-3 , PPA-4 .…”

“…The characteristic signals due to the main chain proton appeared at 5.55-5.70 ppm, suggesting the formation of cis-transoidal configuration of the polymer main chains. 25,26 As shown in Figure 2, the N-H proton signals assigned to the phenylcarbamate residues with electronwithdrawing substituents (chloro group) in PPA-1,-2 shifted downfield compared to those assigned to the phenylcarbamate residues with electron-donating substituents (methyl group) in PPA-3,-4. Intramolecular hydrogen bonds between the adjacent pendant groups of these polymers could induce regular arrangements of the pendants along the polymer backbones and stabilize the helical conformation of the polymers.…”

Two Chirality Transfer Channels Assist Handedness Inversion and Amplification of Circularly Polarized Luminescence in Chiral Helical Polyacetylene Thin Films

“…To acquire more understanding of the polymer containing pendant pyrene units, herein, the fluorescence change in M1 before and after polymerization was investigated. As illustrated in Figure S5, M1 exhibits two emission bands at 380 and 395 nm, originating from the isolated pyrene units, while PM1 has an extra emission band at 480 nm, due to the excimer fluorescence. , The polymerization of M1 is beneficial for the formation of excimer fluorescent emission between the adjacent pyrene pendants along the polyacetylene backbone . The fluorescence performance of the as-prepared copolymers was further investigated.…”

“…52,55 The polymerization of M1 is beneficial for the formation of excimer fluorescent emission between the adjacent pyrene pendants along the polyacetylene backbone. 56 The fluorescence performance of the as-prepared copolymers was further investigated. Surprisingly, P37 emits almost no fluorescence emission in the CHCl 3 solution but shows strong fluorescence in the THF solution (Figure 1c,d).…”

Solvent-dependent fluorescence and circular dichroism properties of poly(quinoxaline-2,3-diyl)s bearing pyrene pendants

“…Pyrene has been widely used as a probe to determine conformations and conformational changes of biomolecules, 11,12 molecular switches, [13][14][15] and macromolecules, [16][17][18] because an excimer emission of pyrene reflects the presence of another pyrene unit in spatial proximity. In general, when two pyrene rings are located within a few angstroms of each other, they exhibit a broad, unstructured band at longer wavelengths of around 500 nm (green color) as an excimer emission.…”