Chuanqing Kang

Ultrasound-promoted chiral fluorescent organogel

In this paper, we have described a chiral binaphthyl-based fluorescent organogel. Very interestingly, similar to sonocrystallisation of organics, ultrasound can promote the gelation while it cannot occur spontaneously at relatively high temperature or low concentration. The fluorescence enhancement of the gel obtained via ultrasound irradiation is observed. In solution there exist rapid dynamic equilibria between (S)-1 oligomers. The association interactions both between gelator molecules and between solvent and gelator molecules could together effect the helical growth of distorted (S)-1nanocrystals. The dihedral angle between the two naphthyl rings of the 1,1′-binaphthyl unit in (S)-1 will increase upon gelation. It has been assumed that ultrasound can play an important role in gelation with a high energy barrier. Sonication-induced gelation is a rapid crystallisation behavior yielding fiber-like aggregates in a metastable system.

In Situ Gel‐to‐Crystal Transition and Synthesis of Metal Nanoparticles Obtained by Fluorination of a Cyclic β‐Aminoalcohol Gelator

A new fluorinated version of a cyclic β-aminoalcohol gelator derived from 1,2,3,4-tetrahydroisoquinoline is presented. The gelator is able to gel various nonprotic solvents through OH⋅⋅⋅N hydrogen bonds and additional CH⋅⋅⋅F interactions due to the introduction of fluorine. A bimolecular lamellar structure is formed in the gel phase, which partly preserves the pattern of molecular organization in the single crystal. The racemate of the chiral gelator shows lower gelation ability than its enantiomer because of a higher tendency to form microcrystals, as shown by X-ray diffraction analysis. The influence of fluorination on the self-assembly of the gelator and the properties of the gel was investigated in comparison to the original fluorine-free gel system. The introduction of fluorine brings two new features. The first is good recognition of o-xylene by the gelator, which induces an in situ transition from gels of o-xylene and of an o-xylene/toluene mixture to identical single crystals with unique tubular architecture. The second is the enhanced stability of the toluene gel towards ions, including quaternary ammonium salts, which enables the preparation of a stable toluene gel in the presence of chloroaurate or chloroplatinate. The gel system can be used as a template for the synthesis of spherical gold nanoparticles with a diameter of 5 to 9 nm and wormlike platinum nanostructures with a diameter of 2 to 3 nm and a length of 5 to 12 nm. This is the first example of a synthesis of platinum nanoparticles in an organogel medium. Therefore, the appropriate introduction of a fluorine atom and corresponding nonbonding interactions into a known gelator to tune the properties and functions of a gel is a simple and effective tactic for design of a gel system with specific targets.

Stereoselective and hierarchical self-assembly from nanotubular homochiral helical coordination polymers to supramolecular gels

A new binaphthylbisbipyridine-based ligand underwent diastereoselective self-assembly with silver(I) ions to form nanotubular homochiral helical coordination polymers, which further hierarchically self-assemble into nanofibers, capable of immobilizing organic solvents.

Synthesis of 3,3′‐Di(2‐Pyridyl)‐1,1′‐Bi‐2‐Naphthol Derivatives

Abstract A new kind of (S)‐3,3′‐dipyridyl BINOLs (3a–d) with C 2‐symmetry were synthesized in 79–84% yields by Suzuki coupling of the diboronic acid dipinacol ester (S)‐1 containing a (S)‐binaphthyl group with bromopyridine derivatives (2a–d) followed by hydrolysis.

An organogel formed from a cyclic β-aminoalcohol

A new organogelator with unique structural feature of a cyclic β-aminoalcohol is presented as the first example of gelation by aminoalcohol through hydrogen-bonding between hydroxy and amine.

In situ iodoalkane-reduction of graphene oxide in a polymer matrix: an easy and effective approach for the fabrication of conductive composites

In situ chemical reduction (ISCR) of graphene oxide (GO) dispersed in a polymer matrix has been regarded as an effective path to fabricate electrically conductive graphene/polymer composites due to the combination of perfect dispersion of GO in a polymer matrix and high electrical conductivity of graphene. However, there are only very limited number of reducing agents that can be applied to the ISCR process for the fabrication of graphene/polymer composites. Herein, we report a highly efficient reducing agent, 1,2-diiodoethane, which can be used in the preparation of graphene (IGO)/polyimide (PI) composites via the ISCR process. The results showed that the electrical conductivity of IGO/PI composites with 2.5 wt% of IGO was 2.22 S m−1, nearly seven orders of magnitudes higher than that of GO/PI without the addition of 1,2-diiodoethane. Moreover, the tensile strength and modulus of IGO/PI composites were increased by about 43% and 52% as compared with that of the pure PI, respectively. Furthermore, 1,2-diiodoethane and its decomposition products would not remain in the composites. The ISCR-based methodology can be extended to many other polymer composites and thus paves the way for easy and effective fabrication of conductive polymer composites.

An Optically Active Polymer for Broad-Spectrum Enantiomeric Recognition of Chiral Acids

Recognition of enantiomers of chiral acids by anion-π or lone pair-π interactions has not yet been investigated but is a significant and attractive challenge. This study reports an optically active polymer-based supramolecular system with capabilities of discriminating enantiomers of various chiral acids. The polymer featuring alternate π-acidic naphthalenediimides (NDIs) and methyl l-phenylalaninates in the backbone exhibits an unprecedented slow self-assembly process that is susceptible to perturbation by various chiral acids. Thus, the combination of anion-π or lone pair-π interactions and sensitivity of the polymeric self-assembly process to external chiral species endows the system with recognition capabilities. This is the first time that anion-π or lone pair-π interactions have been applied in the recognition of enantiomers of various chiral acids with a single system. The results shed light on new strategies for material design by integrating π-acidic aromatic systems and chiral building blocks to afford relevant advanced functions.

Ni-Catalyzed cross coupling of aryl grignard reagents with aryl halides in a nonpolar solvent and an efficient synthesis of biaryls under neat conditions

This study details Ni-catalyzed cross coupling of aryl Grignard reagents with aryl halides in toluene, a nonpolar solvent with a high boiling point. The reaction was applied for the synthesis of various biaryls in good yields without the introduction of a large steric ligand. The Kumada-Tamao-Corriu(KTC) reaction in toluene was then successfully modified to proceed under neat conditions for the efficient syntheses of symmetrical biaryls, particularly in large-scale preparations. Unactivated aryl chlorides show higher reactivity than aryl bromides, particularly under neat conditions. Mechanistic investigations suggest a radical procedure for the catalytic cycle, and the origin of the radical intermediates being aryl halides.

Dehydrogenation and dehalogenation of amines in MALDI‐TOF MS investigated by isotopic labeling

Secondary and tertiary amines have been reported to form [M-H](+) that correspond to dehydrogenation in matrix-assisted laser desorption ionization time of flight mass spectrometry (MALDI-TOF MS). In this investigation, we studied the dehydrogenation of amines in MALDI-TOF MS by isotopic labeling. Aliphatic amines were labeled with deuterium on the methylene of an N-benzyl group, which resulted in the formation of [M-D](+) and [M-H](+) ions by dedeuteration and dehydrogenation, respectively. This method revealed the proton that was removed. The spectra of most tertiary amines with an N-benzyl group showed high-intensity [M-D](+) and [M-H](+) ion peaks, whereas those of secondary amines showed low-intensity ion peaks. Ratios between the peak intensities of [M-D](+) and [M-H](+) greater than 1 suggested chemoselective dehydrogenation at the N-benzyl groups. The presence of an electron donor group on the N-benzyl groups enhanced the selectivity. The dehalogenation of amines with an N-(4-halobenzyl) group was also observed alongside dehydrogenation. The amino ions from dehalogenation can undergo second dehydrogenation. These results provide the first direct evidence about the position at which dehydrogenation of an amine occurs and the first example of dehalogenation of haloaromatic compounds in MALDI-TOF MS. These results should be helpful in the structural identification and elucidation of synthetic and natural molecules.

Efficient Synthesis of Aryl Hydroxylactams by Reducing Imides With Activated Zinc Dust

Abstract A series of aryl hydroxylactams (2a, 2b, 2d–2g, 2i–2k, 2m, and 2n) was synthesized by partially reducing aryl cyclic imides in moderate to excellent yields with activated zinc dust alone in acetic acid. This method was regiospecific and can be employed as an alternative for reported methods to partially reduce aryl cyclic imides.