Development of synthetic double helical polymers and oligomers

Abstract

There is growing interest in the design and synthesis of artificial helical polymers and oligomers, in connection with biological importance as well as development of novel chiral materials. Since the discovery of the helical structure of isotactic polypropylene, a significant advancement has been achieved for synthetic polymers and oligomers with a single helical conformation for about half a century. In contrast, the chemistry of double helical counterparts is still premature. This short review highlights the recent advances in the synthesis, structures, and functions of double helical polymers and oligomers, featuring an important role of supramolecular chemistry in the design and synthesis of double helices. Although the artificial double helices reported to date are still limited in number, recent advancement of supramolecular chemistry provides plenty of structural motifs for new designs. Therefore, artificial double helices hold great promise as a new class of compounds. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5195–5207, 2009

Racemic and conglomerate 1-(4-haloaryl)ethylammonium tetrachlorocobaltate salts: formation of helical structures

“…However, a number of such spontaneous chiral resolution are reported in the literature recently. In this context, the conglomerate formation of the constituent R-and S-cpea amines in rac-cpea as [(R-cpeaH))] 3 The helices in compound 1 are constituted through synthon A (ESI Fig. In some cases, achiral ligands undergo chiral resolution upon complexation forming a conglomerate of enantiomers similar to the current synthesis of 2R and 2S from rac-cpea.…”

“…1. To examine the generality of the formation of helical structures, we subjected enantiopure R-1-(phenyl)ethylamine (R-pea) to the self-assembly process with CoCl 2 , and obtained the analogous A 3 CoCl 4 Cl salt [R-peaH] 3 [CoCl 4 ]Cl (3R). 2.…”

Chiral amplification in double-stranded helical polymers through chiral and achiral amidinium–carboxylate salt bridges

“…In our design, the formation of the intertwined duplex is driven by the formation of an amidiniumcarboxylate salt bridge, and the helicity of the duplexes can be readily controlled by the introduction of chiral substituents on the nitrogen atoms of the amidine residues. 9,15,18,19 We also reported on mterphenyl-based conjugated polymers, which contain optically active amidine groups (poly-A 1 ) and achiral carboxylic groups (poly-C), that folded into an intertwined double-stranded helical structure through the chiral amidinium-carboxylate salt bridges. 29 In this study, we synthesized a series of m-terphenyl-based random copolymers containing chiral and achiral amidines (poly-A x ) and…”

“…In our design, the formation of the intertwined duplex is driven by the formation of an amidiniumcarboxylate salt bridge, and the helicity of the duplexes can be readily controlled by the introduction of chiral substituents on the nitrogen atoms of the amidine residues. 9,15,18,19 We also reported on mterphenyl-based conjugated polymers, which contain optically active amidine groups (poly-A 1 ) and achiral carboxylic groups (poly-C), that folded into an intertwined double-stranded helical structure through the chiral amidinium-carboxylate salt bridges. 29 In this study, we synthesized a series of m-terphenyl-based random copolymers containing chiral and achiral amidines (poly-A x ) and their complementary homopolymers containing achiral carboxylic acids (poly-C), and investigated the effect of the chiral/achiral amidine contents on the amplification of the helical chirality 30,31 during the complementary double-helix formation ('the sergeants and soldiers effect') 3,4,32,33 (Figure 1) using absorption and circular dichroism (CD) spectroscopies.…”

“…[1][2][3] Although a large number of singlestranded helical polymers and oligomers have been reported, [2][3][4][5][6][7][8][9][10][11][12] examples of double-stranded helical polymers and oligomers remain relatively scarce. 2,3,8,9,[13][14][15][16][17][18][19][20][21][22] We have recently reported on the rational design and synthesis of a series of complementary double-stranded helical oligomers [23][24][25][26][27][28] with an optical activity that consists of a crescent-shaped m-terphenyl-based backbone containing amidine and carboxylic acid groups. In our design, the formation of the intertwined duplex is driven by the formation of an amidiniumcarboxylate salt bridge, and the helicity of the duplexes can be readily controlled by the introduction of chiral substituents on the nitrogen atoms of the amidine residues.…”