Helix formation of poly(phenylacetylene) derivatives bearing amino groups at the meta position induced by optically active carboxylic acids

Abstract

Two novel phenylacetylene derivatives bearing diethylaminomethyl groups at the meta position on phenyl groups [3‐(N,N‐diethylaminomethyl)phenyl]acetylene (1) and [3,5‐bis(N,N‐diethylaminomethyl)phenyl]acetylene (2) were synthesized and polymerized with [Rh(nbd)Cl]2 (nbd: norbornadiene). Both monomers gave highly cis–transoidal stereoregular polymers that exhibited an induced circular dichroism (ICD) in the UV–visible region, probably because of a prevailing one‐handed helical conformation upon complexation with optically active carboxylic acids such as mandelic acid and lactic acid. The sign of the Cotton effects reflected the absolute configuration of the chiral acids. Therefore, these polymers can be used as a novel probe for determining the configuration of chiral acids. The polymers were stable in the presence of chiral acids in solution. The poly‐1 complexed with chiral acids exhibited a split‐type ICD, whereas the poly‐2 complexed with chiral acids showed a different, non‐split‐type ICD. The ICD pattern of the poly‐1/chiral acids complexes dramatically changed with an increase in the concentration of the chiral acids, thus showing a non‐split‐type ICD similar to those of the poly‐2/chiral acid complexes. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3180–3189, 2001

Twisting macromolecular chains: Self-assembly of a chiral supermolecule from nonchiral polythiophene polyanions and random-coil synthetic peptides

“…In our case, the blue shifts in absorption, induced by different amounts of JR2K, are accompanied by an increase in the ICD, indicating that chirality introduction may not be derived from -stacked chiral aggregation of the polymer. Instead, the ICDs can be a result of main-chain chirality such as a predominantly one-handed helical structure induced due to the interaction between PTAA-Li and JR2K (13)(14)(15)(16)24). It is interesting that a similar induced chirality has been seen for a free amino acid functionalized PT derivative (24), suggesting that the acid-base complexation between the carboxyl group of the polymer side chains and the amino groups of the lysine side chains in the peptide is responsible for the induced chirality of the polymer backbone.…”

“…This phenomenon derives from the main-chain chirality when chains are aggregated to form a supramolecular, -stacked self-assembly due to intermolecular interactions in a poor solvent or at low temperature, whereas they show no activity in the UV-visible region in a good solvent or at high temperatures (5,(9)(10)(11)(12). Recent studies (13)(14)(15)(16), using optically inactive CPs that become chiral after addition of a chiral guest, show that chirality introduction can also be a result of a main-chain chirality, such as a predominantly one-handed helical structure induced by a acidbase complexation between the CP and the chiral guest.…”

Synthesis and property of helical poly(phenylacetylene)s bearing chiral ruthenium complexes and real space imaging of meso‐ and nanoscopic structures by atomic force microscopy

“…Recently, a number of artificial helical polymers bearing enantiomerically pure chiral or achiral bulky functional side groups have been successfully prepared by the precisely controlled polymerization of functional monomers with well‐defined catalysts 27–35. These synthetic helical polymers exhibit many interesting characteristics, including electronic and photophysical properties,21, 36 the formation of thermotropic liquid crystals,37, 38 chiral and chirality recognition ability,39–51 and helix–helix transition 48, 52–61. Therefore, understanding the relationship between the functions and the global structures and local conformations is crucial in this field 27–35.…”

Aromatic Donor–Acceptor Charge‐Transfer and Metal‐Ion‐Complexation‐Assisted Folding of a Synthetic Polymer

“…[3] Although several examples of synthetic polymers that adopt helical conformations in solutions are known, for example, poly(trityl methacrylate)s, [4] polyisocyanates, [5] cis-poly(acetylene)s, [6] polyisocyanides, [7] and poly(1,3-phenylene ethynylene)s, [8] most of these deal with relatively stiff chains that have very limited conformational degrees of freedom as a result of steric and/or bond-angle constraints. There are, however, only very few examples of relatively flexible systems that have been made to adopt a well-defined conformation in solution.…”