Homo‐double helix formation of an optically active conjugated polymer bearing carboxy groups and amplification of the helicity upon complexation with achiral and chiral amines

Abstract

An optically active, m-terphenyl-based p-conjugated polymer bearing carboxy groups was synthesized by the copolymerization of the diethynyl monomer bearing a carboxy group with (S,S)-2,5-bis(2-methylbutoxy)-1,4-dibromobenzene using Sonogashira reaction. The copolymer showed a weak circular dichroism (CD) in the main-chain chromophore region due to a homo-double helix formation with an excess helical handedness biased by the chiral alkoxy substituents through self-association. However, upon complexation with achiral amines, such as piperidine, the CD intensity of the polymer significantly increased resulting in the formation of a greater excess one-handed homo-double helix via hydrogen-bonded inclusion complexation with the achiral amines between each strand, leading to the amplification of the helicity. A preferredhanded homo-double helix was also induced in the polymer in the presence of nonracemic amines. The effect of the achiral and chiral amines on the homo-double helix formation was investigated by comparing the CD spectra of the polymer to those of its model dimer. V C 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 990-999

Supramolecular Helical Systems: Helical Assemblies of Small Molecules, Foldamers, and Polymers with Chiral Amplification and Their Functions

“…On the other hand, the optically active dimer (S)-280, bearing the chiral alkoxy substituents on the central phenylene ring, displayed an ICD in CDCl 3 due to self-association of the dimer strands to form a preferred handed homodouble helix (Figure 86B). 459 Interestingly, an inclusion complex formation of (S)-280 with achiral amines, in particular with piperidine and diethylamine, resulted in a significant enhancement of the CD intensities of (S)-280, indicating amplification of the helical chirality that occurs during the formation of the double-helical inclusion complex with achiral amines sandwiched between the carboxylic acid strands (Figure 86B). Although the CD intensity of (S)-280 also remarkably changed in the presence of chiral amines, its homodouble helical inclusion complex formation with enantiomeric mixtures of the chiral amines resulted in a linear increase in the CD intensity with the increasing %ee of the amines, indicating no chiral amplification.…”

Chiral Template-Directed Regio-, Diastereo-, and Enantioselective Photodimerization of an Anthracene Derivative Assisted by Complementary Amidinium–Carboxylate Salt Bridge Formation

“…Interestingly, the photodimerization of 1 proceeded faster than that of 1 -Me to selectively yield the HH dimers ( anti -HH- 4 and syn -HH- 5 ) (HT/HH = 14/86), in particular, the syn -HH- 5 dimer in 71% yield after a 10 min irradiation (run 2, Table , Figures f and S3) probably due to the duplex formation (( 1 ) 2 ) in a syn -HH fashion through self-association of the carboxy groups of 1 in CDCl 3 (Figure S4). , …”

Chirality- and sequence-selective successive self-sorting via specific homo- and complementary-duplex formations

“…We anticipated that either a right- or left-handed homodouble helix would be induced in the carboxylic acid dimers when chiral linkers 52 , such as ( S , S )- or ( R , R )- trans -1,2-cyclohexane-based ( c Hex) bis -amide derivatives, were introduced between the monomer units ( 1 and 2 , Fig. 1b ).…”