[Rh(L-alaninate)(1,5-Cyclooctadiene)] Catalyzed Helix-Sense-Selective Polymerizations of Achiral Phenylacetylenes

Abstract

The [Rh(L-alaninate)(cod)] (cod = 1,5-Cyclooctadiene) complex was synthesized and characterized. Asymmetric polymerizations of achiral phenylacetylene with two hydroxyl groups and a dodecyl group (DoDHPA) were performed by using the rhodium complex as the catalyst to provide polymers with a higher molecular weight (>105) than the polymers obtained using the [Rh(cod)Cl]2 initiator systems. The resulting polymers showed circular dichroism (CD) signals at approximately 310 and 470 nm, indicating that they have a preferential one-handed helical structure. The helix sense in the polymer main chain was controlled by the sign of the catalyst chirality. These findings suggest that the rhodium complex with a chiral amine is the true active species for the helix-sense-selective polymerization of DoDHPA. The [Rh(L-alaninate)(cod)] complex also exhibits high catalytic activity in the polymerization of phenylacetylene (PA) to give a high yield and molecular weight. All these results demonstrate that this Rh complex is an excellent catalyst for the polymerization of phenylacetylene monomers.

Rh(I) Complexes in Catalysis: A Five-Year Trend

“…The substrate is achiral, but the resulting polymer has a favoured one-handed structure, induced by the amino acid chirality. Moreover, it has a higher molecular mass with respect to polymers obtained with [Rh(COD)Cl] 2 as the initiator [81]. Comparable results were previously reported by the same research group with Rh(NBD)(l-proline) (NBD = 2,5-norbornadiene) on the same reaction [82], as [Rh(NBD)Cl] 2 is another common initiator for this kind of process.…”

Helix-Sense-Selective Polymerization of 3,5-bis(hydroxymethyl)phenylacetylene Rigidly Bearing Galvinoxyl Residues and Their Chiroptical Properties

“…We have already succeeded in the HSSP of various 4-substituted 3,5-bis(hydroxymethyl)phenylacetylenes [6,9,10,11,13,14,15,16]. Then, we explore the HSSP of new achiral monomers rigidly bearing a hydrogalvinoxyl moiety.…”

“…Polymers with helical conformation possess chirality; i.e., the polymers predominantly folding into either a left- or right-handed helical conformation exhibit optical activity despite the absence of asymmetric carbons. Synthesis of helical polymers with a controlled helicity has attracted considerable attention as one of the fundamental factors for their wide variety of potential applications in materials science, such as chiral sensors, chiral catalysts, optical resolution, microelectronic devices, organic magnetic materials, and so on [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17].…”

The Chirality Induction and Modulation of Polymers by Circularly Polarized Light

“…The asymmetric structure of polymers plays an important role in the maintenance of life processes, metabolism and evolution, and chiral polymers have been widely used in asymmetric synthesis, chiral recognition, and enantiomeric separation [13][14][15][16][17][18][19][20][21][22][23]. Moreover, chiral polymers also hold potential 2 of 19 for application in chiral catalysts, liquid crystals, nonlinear optical materials, and the biomedical industry [24][25][26][27][28][29][30][31][32][33]. In recent years, scientists have reported several methods to synthesize chiral materials, such as the use of chiral solvents or templates, polymerization with chiral monomers, substituted achiral polymers with a chiral center, supramolecular self-assembly and circularly polarized light (CPL) irradiation.…”