A general strategy to tune the achiral main chain polymers into helical nanoassemblies was proposed based on the co-gelation approach. As an example, two achiral main chain polymers, PCz8 and PSi8, were selected, and their co-assembly with an amphiphilic L- or D-glutamide gelator was investigated. Although the polymers could not form gels individually, they could form co-gels with the gelator and the resultant gels exhibited macroscopic supramolecular chirality, which could be confirmed by CD spectra and SEM observations. Moreover, the supramolecular chirality can be memorized even after the gelator molecules were removed. Remarkably, either the gelator-containing or gelator-free chiral polymer assemblies showed circularly polarized luminescence (CPL), which is usually inherent to intrinsic chiral polymers. It was suggested that during the co-gelation, the chirality of the gelator was transferred to and memorized by the achiral polymers. The approach seems to be general and we provided the first example to tune the achiral polymers into helical assemblies through the co-gelation.

A strategy for tuning achiral main-chain polymers into helical assemblies and chiral memory systems

Asymmetric kinetic resolution polymerization

The invention discloses a measuring method and a device for simultaneously measuring the membrane permeability of each gas in mixed gas. According to the measuring method and device, the combination of a gas chromatograph and a gas permeation tank for measuring the membrane permeability is realized, and the permeabilities of multiple components of a thin film and a flake material when the mixed gas permeates through the thin film and the flake material can be simultaneously and rapidly measured accurately one time; furthermore, in a connecting method disclosed by the invention, an air blowing system does not need to be arranged, the measuring method can be used for measuring the thin film with the diameter of 8mm or even smaller without that the gas passes through a quantitative feeding device, and a gas chromatography flame ionization detector has the enough sensitivity for measuring penetration gas after permeating for 5 minutes. By utilizing the measuring method and device, the interaction effect of each component to the permeation rate can be researched when the mixed gas permeates, and the diffusion coefficients of the solubility coefficients of the thin film and the flake material can be conveniently measured.

Measuring method and device for simultaneously measuring membrane permeability of each gas mixed gas

A coupling reaction between salicylaldehyde and phenylacetylene was catalyzed by well-defined rhodium complexes, Rh(cod)(l-amino acid) (cod is 1,5-cyclooctadiene; l-amino acid is l-proline, l-phenylalanine and l-valine), to give a flavonoid in 40–88% yield, providing a method for flavonoid synthesis. The coupling reactions catalyzed by Rh(cod)(l-amino acid)s gave higher yields than those by [Rh(cod)Cl]2 without l-amino acid ligands. The reaction mechanism may be that l-amino acid ligands of the rhodium complexes can provide an empty track for phenylacetylene to form a ring structure that fractures to produce the aim flavonoid and RhIX species. Then, the active RhIX specie is oxidized to regenerate RhIIIX3 by Cu(OAC)2.

Rhodium complexes catalyze oxidative coupling between salicylaldehyde and phenylacetylene via C–H bond activation

Rhodium is one of the most used metals in catalysis both in laboratory reactions and industrial processes. Despite the extensive exploration on “classical” ligands carried out during the past decades in the field of rhodium-catalyzed reactions, such as phosphines, and other common types of ligands including N-heterocyclic carbenes, ferrocenes, cyclopentadienyl anion and pentamethylcyclopentadienyl derivatives, etc., there is still lively research activity on this topic, with considerable efforts being made toward the synthesis of new preformed rhodium catalysts that can be both efficient and selective. Although the “golden age” of homogeneous catalysis might seem over, there is still plenty of room for improvement, especially from the point of view of a more sustainable chemistry. In this review, temporally restricted to the analysis of literature during the past five years (2015–2020), the latest findings and trends in the synthesis and applications of Rh(I) complexes to catalysis will be presented. From the analysis of the most recent literature, it seems clear that rhodium-catalyzed processes still represent a stimulating challenge for the metalloorganic chemist that is far from being over.

https://www.mdpi.com/1420-3049/26/9/2553/pdf

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

The Rh(nbd)(l-proline) (nbd = 2,5-norbornadiene) catalyst was synthesised with l-proline as ligand. The achiral monomer phenylacetylene, having two hydroxyl groups and a dodecyl group (DoDHPA), was polymerised for the first time using an isolated chiral Rh(nbd)(l-proline) as catalyst to afford polymers of Mr of 28.5 × 104 and 36.2 × 104. The resulting polymers exhibited the Cotton effect at wavelengths assignable to the main chain, indicating that the polymers adopted one-handed helical conformation. These findings suggest that the rhodium complex with chiral amine may be the true active species for helix-sense-selective polymerisation (HSSP) of DoDHPA.

Asymmetric polymerisation of substituted phenylacetylene using chiral Rh(2,5-norbornadiene)(L-proline) catalyst

Two novel chiral well-defined rhodium complexes, Rh(cod)(L-Phe) (cod = 1,5-cyclooctadiene, Phe = phenylalanine) and Rh(cod)(L-Val) (Val = valine) were synthesized, isolated by recrystallization, and characterized. The helix-sense-selective polymerization (HSSP) of an achiral 3,4,5-trisubstituted phenylacetylene, p-dodecyloxy-m,m-dihydroxyphenylacetylene (DoDHPA) was examined by using the two Rh complexes as catalysts. These catalysts provided high molecular weight polymers (Mw 28 × 104−45 × 104) in about 40%–85% yields. The resulting polymers exhibited a bisignated CD signal at about 300 nm and a broad signal around 470 nm, indicating that they have preferential one-handed helical structure. The present catalysts achieved larger molar ellipticity up to [θ]310 = 13.0 × 104 deg cm2/dmol than those with binary chiral catalytic systems, [Rh(cod)Cl]2/(L-phenylalaninol), [Rh(cod)Cl]2/(L-valinol), and [Rh(nbd)Cl]2/(R)-PEA. All these results manifest that the present, well-defined Rh complexes serve as excellent catalysts for the HSSP of DoDHPA. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 2346–2351

Novel isolated, L‐amino acid‐ligated rhodium catalysts that induce highly helix‐sense‐selective polymerization of an achiral 3,4,5‐trisubstituted phenylacetylene

The invention discloses a preparation method of a rhodium catalyst by using 2,5-norbornadiene (nbd) and 2-aminonicotinic acid as ligands. The preparation method comprises the following steps: taking 26 mg of 2-aminonicotinic acid and 40 mg of potassium hydroxide into a reagent bottle, adding 1.0-2.0 mL of deionized water, and stirring for dissolving; taking 45 mg-55mg of Rh Cl3.3H2O in an inclined two-port flask, injecting 3.0 mL of alcohol and 1.0 mL of a mixed solvent in the presence of a nitrogen gas, and stirring until dissolving completely; adding 0.10 mL-0.20 mL of 2,5-norbornadiene (nbd), stirring for 30 minutes, then heating to 60 DEG C, refluxing, and stirring until liquor is yellow; when 3 hours later, placing under the room temperature and stirring. The novel rhodium complex catalyst obtained by the preparation method disclosed by the invention can be used for further improving the polymerization conversion rate and stereoselectivity while catalyzing substituted acetylene to polymerize.

Preparation method of rhodium catalyst by using 2,5-norbornadiene (nbd) and 2-aminonicotinic acid as ligands

Three chiral phenylacetylenes having an l -amino alcohol residue and two hydroxymethyl groups and an achiral phenylacetylene having two hydroxyl groups and a dodecyl group were copolymerized by using an achiral catalyst ((nbd)Rh + [η 6 -(C 6 H 5 )B − (C 6 H 5 ) 3 ]) (nbd = norbornadiene) to produce copolymers with M w of 0.5 × 10 4 –15.2 × 10 4 . The copolymers exhibited the Cotton effect at wavelengths assignable to the main chain, indicating that the copolymers adopted one-handed helical conformations. Self-supporting membranes of the resulting copolymers were prepared by the solution casting method. We measured the gas permeabilities (CO 2 /N 2 , CO 2 /CH 4 ) of the copolymer membranes. The separation selectivity factor of CO 2 /N 2 was 17.9, and the CO 2 permeability coefficient of CO 2 /N 2 was 77 Barrers.

Copolymerizations of chiral phenylacetylenes having an L-amino alcohol residue and an achiral phenylacetylene having a dodecyl group, used as gas separation membranes

The utility model discloses a gas permeability testing device on a gas permeameter. An experiment gas channel of a testing cavity of the gas permeameter is formed in an upper cavity plate and is communicated with an upper cavity; the two sides of a test sample area between the upper cavity plate and a lower cavity plate are respectively provided with a sealing rubber gasket; a three-way pipeline is arranged at the bottom end of a one-way carrier gas channel communicated with a lower cavity; and the tail end of one pipeline of the three-way pipeline is provided with a gas chromatograph connecting pipe sleeve. The gas permeability testing device has the beneficial effect of qualitatively and quantitatively testing the permeation capacity of all components of mixed gas in a separating membrane at the same time by virtue of a connecting channel between the testing device and a gas chromatograph inlet, thus solving the technical problem that an existing permeameter for testing a macromolecular gas separating membrane can only test parameters of single gas in the separation membrane.

Peng Jijun

Papers

Asymmetric polymerisation of substituted phenylacetylene using chiral Rh(2,5-norbornadiene)(L-proline) catalyst

Novel isolated, L‐amino acid‐ligated rhodium catalysts that induce highly helix‐sense‐selective polymerization of an achiral 3,4,5‐trisubstituted phenylacetylene

Preparation method of rhodium catalyst by using 2,5-norbornadiene (nbd) and 2-aminonicotinic acid as ligands

Copolymerizations of chiral phenylacetylenes having an L-amino alcohol residue and an achiral phenylacetylene having a dodecyl group, used as gas separation membranes

Gas permeability testing device on gas permeameter