Enantiomer separation on novel cellulose derivatives bearing regioselective phenylcarbamate groups.

Four novel regioselectively carbamoylated cellulose derivatives with two types of substituents, one being a 3-chloro-4-methylphenylcarbamate group and the other being a phenylcarbamate, a 3,5-dichlorophenylcarbamate or a 4-methylphenylcarbamate group, at the 2-, 3-positions and 6-position were synthesized and utilized as chiral stationary phases in high-performance liquid chromatography. The obtained derivatives exhibited characteristic chiral recognition abilities which were significantly affected by the nature and arrangement of the groups at the 2-, 3-positions and 6-position. Compared with cellulose tris(3-chloro-4-methylphenylcarbamate) and Chiralcel OD columns, several racemates were better resolved on these new phases. With all six racemates resolved on cellulose 2,3-bis(4-methylphenylcarbamate)-6-(3-chloro-4-methylphenylcarbamate), it appears to be a potential useful chiral stationary phase in the future. Also, the influence of mobile phase on chiral recognition was investigated. Better resolutions were generally obtained with decreased amount of 2-propanol with a mixture of hexane/2-propanol as the mobile phase. Moreover, when ethanol was used instead of 2-propanol as the mobile phase modifier, poorer enantioseparations were often achieved.

Rhodium-catalyzed reductive carbonylation of aryl iodides to arylaldehydes with syngas.

The reductive carbonylation of aryl iodides to aryl aldehydes possesses broad application prospects. We present an efficient and facile Rh-based catalytic system composed of the commercially available Rh salt RhCl3·3H2O, PPh3 as phosphine ligand, and Et3N as the base, for the synthesis of arylaldehydes via the reductive carbonylation of aryl iodides with CO and H2 under relatively mild conditions with a broad substrate range affording the products in good to excellent yields. Systematic investigations were carried out to study the experimental parameters. We explored the optimal ratio of Rh salt and PPh3 ligand, substrate scope, carbonyl source and hydrogen source, and the reaction mechanism. Particularly, a scaled-up experiment indicated that the catalytic method could find valuable applications in industrial productions. The low gas pressure, cheap ligand and low metal dosage could significantly improve the practicability in both chemical researches and industrial applications.

Preparation of cyclic imides from alkene-tethered amides: application of homogeneous Cu(ii) catalytic systems.

A Cu-based homogeneous catalytic system was proposed for the preparation of imides from alkene-tethered amides. Here, O2 acted as a terminal oxidant and a cheap and easily available oxygen source. The cleavage of C[double bond, length as m-dash]C bonds and the formation of C-N bonds were catalyzed by Cu(ii) salts with proper nitrogen-containing ligands under 100 °C. The synthesis approach has potential applications in pharmaceutical syntheses. Moreover, scaled-up experiments confirmed the practical applicability.

Small organic molecules with tailored structures: initiators in the transition-metal-free C-H arylation of unactivated arenes.

Simple, small organic molecules containing nitrogen and oxygen atoms in their structures have been disclosed to catalyze transition-metal-free C-H arylation of unactivated arenes with aryl iodides in the presence of t BuOK. In this article, an optimized catalytically active molecule, (2-(methylamino)phenyl)methanol, was designed. A broad range of aryl iodides could be converted into the corresponding arylated products at 100 °C over 24 h with good to excellent yields. Mechanistic experiments verified that radicals participated in this catalytic transformation and that the cleavage of the aromatic C-H bond was not the rate determining step. A K+ capture experiment by 18-crown-6 emphasized the significance of the cation species of the strong base. Fourier transform infrared spectroscopy proved that the catalytic system was activated by the hydrogen bonds between small organic molecules and t BuOK. Also, a clear mechanism was proposed. This transition-metal-free method affords a promising system for efficient and inexpensive synthesis of biaryls via a user-friendly approach, as confirmed by scale-up experiments.

Defect Engineering for Modulating the Trap States in 2D Photoconductors.

Defect-induced trap states are essential in determining the performance of semiconductor photodetectors. The de-trap time of carriers from a deep trap can be prolonged by several orders of magnitude as compared to shallow traps, resulting in additional decay/response time of the device. Here, it is demonstrated that the trap states in 2D ReS2 can be efficiently modulated by defect engineering through molecule decoration. The deep traps that greatly prolong the response time can be mostly filled by protoporphyrin molecules. At the same time, carrier recombination and shallow traps in-turn play dominant roles in determining the decay time of the device, which can be several orders of magnitude faster than the as-prepared device. Moreover, the specific detectivity of the device is enhanced (as high as ≈1.89 × 1013 Jones) due to the significant reduction of the dark current through charge transfer between ReS2 and molecules. Defect engineering of trap states therefore provides a solution to achieve photodetectors with both high responsivity and fast response.

Synthesis, characterization and luminescent properties of lanthanide complexes with a novel multipodal ligand.

Solid complexes of lanthanide nitrates with an novel multipodal ligand, 1,2,4,5-tetramethyl-3,6-bis{N,N-bis[((2'-furfurylaminoformyl)phenoxyl)ethyl]-aminomethyl}-benzene (L) have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Sm(III), Eu(III), Tb(III) and Dy(III) nitrate complexes in solid state were investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of central metal ions. The lowest triplet state energy level of the ligand indicates that the triplet state energy level (T1) of the ligand matches better the resonance level of Tb(III) than other lanthanide ions.

Synthesis, characterization and luminescent properties of lanthanide complexes with an unsymmetrical tripodal ligand.

Solid complexes of lanthanide nitrates with an novel unsymmetrical tripodal ligand, butyl-N,N-bis[((2'-benzylaminofomyl)phenoxyl)ethyl]-amine (L) have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Sm(III), Eu(III), Tb(III) and Dy(III) nitrate complexes in solid state were also investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of central metal ions.

N'-[(E)-2-Hydroxy-benzyl-idene]-5-methyl-isoxazole-4-carbohydrazide monohydrate.

In the structure of the title compound, C(12)H(11)N(3)O(3)·H(2)O, the dihedral angle formed by the benzene and isoxazole rings is 2.03 (8)°. The mol-ecular conformation is stabilized by an intra-molecular O-H⋯N hydrogen bond. In the crystal structure, mol-ecules are linked into a three-dimesional network by inter-molecular N-H⋯O, O-H⋯N and O-H⋯O hydrogen bonds, and by π-π stacking inter-actions involving adjacent benzene and isoxazole rings [centroid-centroid separation = 3.663 (2) Å].

Synthesis and luminescent properties of lanthanide complexes with a novel multipodal ligand.

Solid complexes of lanthanide nitrates, picrates and perchlorates with a novel multipodal ligand, 1,2,4,5-tetramethyl-3,6-bis{N,N-bis[((2'-benzylaminoformyl)phenoxyl)ethyl]-aminomethyl}-benzene (L) have been synthesized and characterized by elemental analysis, infrared spectra and molar conductivity measurements. At the same time, the luminescent properties of the Eu and Tb complexes in solid state were investigated. Under the excitation of UV light, these complexes exhibited characteristic emission of central metal ions. The lowest triplet state energy level T(1) of this ligand matches better to the lowest resonance energy level of Tb(III) than to Eu(III) ion. The influence of the counter anion on the luminescent intensity was also discussed.