A General and Efficient CuBr2‐Catalyzed N‐Arylation of Secondary Acyclic Amides

A general and efficient Cu(II)‐catalyzed cross‐coupling method is reported for the preparation of acyclic tertiary amides. Generally moderate to excellent yields and functional group tolerance were obtained with secondary acyclic amides and aryl halides as substrates in toluene.     

Effect of composite supports on the methanation activity of Co-Mo-based sulphur-resistant catalysts

The effects of composite supports of CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 on the methanation activity of supported Co-Mo-based sulphur-resistant catalysts were investigated.The catalysts were further characterized by nitrogen adsorption measurement,X-ray diffraction and X-ray photoelectron spectroscopy.The catalyst of 5%CoO-15%MoO3 supported on CeO2-Al2O3,MgO-Al2O3,TiO2-Al2O3 or ZrO2-Al2O3 composite oxides,respectively,showed different catalytic performances of syngas methanation in the presence of hydrogen sulphide as compared with that of the 5%CoO-15%MoO3/Al2O3 catalyst.The Co-Mo/CeO2-Al2O3 catalyst shows the highest methanation activity among the tested catalysts.The enhanced methanation activity may be attributed to the improvement of the dispersion of active metal species and the inhibition of the formation of S6+.     

Preparation and chiral separation of a novel immobilized cellulose-based chiral stationary phase in high-performance liquid chromatography

The chiral selector 6-azido-2, 3-di(p-chlorophenylcarbamoylated) cellulose was synthesized and further chemically immobilized onto 5-μm amino functionalized spherical porous silica gel. It was used as chiral stationary phase in high-performance liquid chromatography. Thirty racemates were successfully separated into enantiomers in either normal phase mode or reversed-phase mode. Good reproducibility and stability of the chiral stationary phase have been demonstrated.     

2-硫代嘧啶酮和2-硫代吡啶酮在B-吸收带中的动态结构

采用共振拉曼光谱学结合量子化学计算研究了2-硫代嘧啶酮(2TPM)和2-硫代吡啶酮(2TP)在B-带吸收时的动态结构. 在气相时, 2-巯基嘧啶(2MPM, 硫醇式)比2TPM(硫代酮式)更稳定, 能量差约为15.1 kJ·mol^-1, 而在水和乙腈溶液中, 2TPM比2MPM更稳定, 能量差分别为29.3和28.0 kJ·mol^-1. 气相及基电子态时,由B3LYP/6-311++G(d,p)计算水平获得的2TPM和2MPM之间发生质子转移异构化反应的过渡态能垒约为130 kJ·mol^-1. 2TPM三个吸收带分别被指认为π_H→π_L^*, π_H→π_L+1^*和π_H-1→π_L^*跃迁. 基于对2TPM在固体和溶液相傅里叶变换-拉曼(FT-Raman)和傅里叶变换-红外(FT-IR)光谱测量, 以及B3LYP/6-311++G(d,p)计算, 开展了2TPM在水和乙腈溶液中的B-带共振拉曼光谱的振动指认, 由此获得了2TPM的动态结构, 并与2TP的动态结构进行了比较. 2TPM和2TP动态结构的差异反映了ππ^*/πσ^*锥形交叉点结构的差异, 因此, 可被用于洞察光诱导的氢原子脱离-复合机制.     

Controllable selective exfoliation of high-quality graphene nanosheets and nanodots by ionic liquid assisted grinding

Bulk quantities of graphene nanosheets and nanodots have been selectively fabricated by mechanical grinding exfoliation of natural graphite in a small quantity of ionic liquids. The resulting graphene sheets and dots are solvent free with low levels of naturally absorbed oxygen, inherited from the starting graphite. The sheets are only two to five layers thick. The graphene nanodots have diameters in the range of 9-29 nm and heights in the range of 1-16 nm, which can be controlled by changing the processing time.     

Fe-catalysed oxidative C-H functionalization/C-S bond formation

Iron was used as the catalyst for the direct C-H functionalization/C-S bond formation under mild conditions. Various substrates could afford benzothiazoles in moderate to excellent yields. Preliminary mechanistic studies revealed that pyridine played a crucial role for the high yields and selectivities.     

2-氨基-4,5-二取代烃嘧啶类衍生物的新合成方法

研究了2-氨基-4,5-二烃基取代嘧啶类衍生物的一个新的简易合成方法,该方法以简单且廉价的4个芳香醛和3个脂肪醛为原料,经过四步反应得到12个2-氨基-4,5-二烃基取代嘧啶类化合物,总收率在40%～70%,经氢核磁共振(1H NMR)、碳核磁共振(13C NMR)和高效液质联用(LC-MS)对其目标产物进行表征.     

Molecular torus group

Generally speaking, the highest symmetry of M?bius cyclacene molecule possesses the C₂ symmetry based on the theory of point group according to the previous works. However, based on the topology principle, the fundamental group of M?buis strip is an infinite continuous cyclic group and its border is made up of twice of the generator. Of course, the M?bius strip-like molecule is associated with a finite discrete cyclic symmetry group. For the cyclacene isomers constructed by several (n) benzene rings, these isomers include: the common cylinder Hückel cyclacene (HC-[n]) molecules, the M?bius cyclacene (MC-[n]) molecules by twisting the linear precursor one time (180°), and the multi-twisted M?bius strip-like cyclacene (M ^m C?[n]) molecules by twisting the linear precursor m times (m × 180°). The relevant results suggest that in addition to the point symmetry, there is a new kind of symmetry called the torus screw rotation (denoted as TSR). In this article, we take the M ^m C?[n] molecules as examples to discuss their TSR group and point group symmetry, and the relative symmetry adaptive atom sets as well as their atomic orbital (AO) sets. Here, the Cartesian coordinates is not quite fit for the investigation of these AOs, so it is replaced by either the torus orthogonal curvilinear coordinates (for M ^m C?[n] molecule) or the cylinder orthogonal curvilinear coordinates (for HC-[n] molecule). According to the features of cyclic group, the character table of the irreducible representation of the TSR group could be constructed easily. Some other relevant point-group symmetries maybe also belong to the molecule, so its symmetry maybe called as the torus group symmetry. For multi-twisted M?bius strip-like molecule, there are some correlations in topology characteristics.     

Luminescence properties of Mn(2+)-doped Li2ZnGeO4 as an efficient green phosphor for field-emission displays with high color purity

Green emitting Li(2)ZnGeO(4):Mn(2+) phosphors were synthesized through a high temperature solid-state reaction process. X-Ray diffraction, field emission scanning electron microscopy, photoluminescence (PL) and cathodoluminescence (CL) spectra were utilized to characterize the synthesized samples. Under UV and electron-beam excitation, the pure Li(2)ZnGeO(4) sample shows a blue emission due to defects, while the Li(2)ZnGeO(4):Mn(2+) sample exhibits a green emission corresponding to the characteristic transition of Mn(2+) ((4)T(1)→(6)A(1)). In particular, the CL intensity (brightness) of Li(2)ZnGeO(4):Mn(2+) is higher than that of commercial green phosphor ZnO:Zn. In addition, the CL properties of Li(2)ZnGeO(4):Mn(2+) phosphor, the dependence of CL intensity on accelerating voltage and filament current, the decay behavior of CL intensity under electron bombardment, and the stability of CIE chromaticity coordinates, have been investigated in detail. The results indicate that the as-prepared Li(2)ZnGeO(4):Mn(2+) phosphor has a good CL intensity and CIE coordinate stability with green emission under low-voltage electron beam excitation. Therefore, Li(2)ZnGeO(4):Mn(2+) is a promising green phosphor for application in full-color field-emission displays.     

Shedding light on unusual photophysical properties of bis-cyclometalated iridium(iii) complexes containing 2,5-diaryl-1,3,4-oxadiazole-based and acetylacetonate ligands

A DFT/TDDFT investigation was conducted on a series of cyclometalated iridium(iii) complexes with 2,5-diaryl-1,3,4-oxadiazole (oxd(n)) derivatives to shed light on the effects of the stereoisomeric and steric factors on the photophysical properties. On the basis of the results reported herein, we attempt to explain the experimental observations according to which complexes N,N-trans [Ir(oxd(0))(2)(acac)] (1a) and N,N-trans [Ir(oxd(1))(2)(acac)] (2a) [with oxd(0) = 2,5-diphenyl-1,3,4-oxadiazole, oxd(1) = 2,5-bis(4-fluorophenyl)-1,3,4-oxadiazole and acac = acetylacetonate] show high quantum phosphorescence efficiencies (Φ(PL)) of 35 and 44%, while an extremely low Φ(PL) (<1%) was observed for a number of oxd(n) based complexes including N,N-cis [Ir(oxd(3))(2)(acac)] (4b) [with oxd(3) = 2-(4-fluorophenyl)-5-(2,4,6-triisopropylphenyl)-1,3,4-oxadiazole]. While new insights were gained on structural and electronic properties, the unusual photophysical properties recently reported for 4b were found to be not inherent to spin-orbit coupling (SOC) effects, but determined by both the S(1)-T(1) splitting energy (ΔE(S1-T1)) and the transition dipole moment (μ(S1)) upon the S(0)→ S(1) transition. Drastically large ΔE(S1-T1) and small μ(S1) for 4b (0.70 eV and 0.23 D, respectively) comparative to those for 2a (0.38 eV and 2.76 D, respectively) and 1a (0.58 eV and 2.44 D, respectively) were found to be tightly linked to the twisting degree of the oxd(n) ligand and to the trans-cis structural isomerism. On the basis of these parameters, the unusual physical properties of 4b were interpreted with respect to 1a and 2a, and the higher Φ(PL) of 2a with respect to that for 1a was explained.