Improved synthesis of 2,2'-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives catalyzed by urea under ultrasound

Synthesis of 2,2′-arylmethylene bis(3-hydroxy-5,5-dimethyl-2-cyclohexene-1-one) derivatives catalyzed by urea via the condensation of aromatic aldehydes and 5,5-dimethyl-1,3-cyclohexanedione was carried out in 80-98% yields at 50 °C in aqueous media under ultrasound. This method provides several advantages such as environment friendliness, high yields and simple work-up procedure.     

化学发光法直接测定水中1，3-二氯-5，5-二甲基海因的研究

研究了在碱性条件下(pH12.0—12.5)1,3-二氯-5,5-二甲基海因与鲁米诺-过氧化氢体系产生的化学发光性质,首次建立了一种测定其含量的新方法,并应用于游泳池水中1,3-二氯-5,5-二甲基海因的测定,结果满意。1,3-二氯-5,5-二甲基海因的浓度在8.0×10     

Hydrogen adsorption on Pt-decorated closed-end armchair (3,3), (4,4) and (5,5) single-walled carbon nanotubes

ABSTRACT

Structures of small lengths of capped (3,3), (4,4) and (5,5) single-walled carbon nanotubes (SWCNTs) and their structures decorated by Pt atom and Pt_n clusters (n = 2–4) were obtained using density functional theory calculations. Binding abilities of Pt atom and Pt_n clusters on the outer surface of SWCNTs at various adsorption sites were explored. Adsorptions of H₂ onto Pt atom of the Pt-decorated (3,3), (4,4) and (5,5) SWCNTs were studied and their adsorption energies are reported. The thermodynamic properties and equilibrium constants for H₂ adsorptions on the Pt₄-decorated (3,3), (4,4) and (5,5) SWCNTs were obtained. The adsorption of H₂ on the Pt atom of the Pt₄/(3,3) SWCNT was found to be the most preferred reaction of which enthalpy and free energy changes at room temperature are ?46.61 and ?23.99 kcal/mol, respectively.     

One-pot three-component synthesis of 3-hydroxy-5,5-dimethyl-2-[phenyl(phenylthio)methyl]cyclohex-2-enone derivatives under ultrasound

3-Hydroxy-5,5-dimethyl-2-[phenyl(phenylthio)methyl]cyclohex-2-enone is synthesized via one-pot three-component reactions of aromatic aldehyde, substituted thiophenol and 5,5-dimethyl-1,3-cyclohexanedione catalyzed by p-dodecylbenzene sulfonic acid (DBSA) under ultrasound. Under ultrasound irradiation the yields are much higher (sometimes substantially, by almost double) and the reaction time decreases substantially, the reaction conditions are milder. This method provides several advantages such as environment friendliness, high yields and simple work-up procedure and the protocol provides a novel alternative for the synthesis of thioether.     

一种新型的橙红光发射材料聚8-羟基喹啉镓的合成与光谱特性

合成了高分子金属配合物聚8-羟基喹啉镓(Gaqq3)n.利用红外吸收光谱、X射线衍射谱(XRD)研究了配合物的分子结构、物相结构;利用热重(TG)分析研究了配合物的热稳定性;利用紫外吸收光谱、荧光激发和发射光谱研究了该配合物的光物理性能.结果表明:(Gaqq3)n的热分解温度为443.6℃,具有较高的热稳定性.(Gaqq3)n的紫外吸收带位于250～500 nm,存在较强的带尾吸收,表明禁带中存在带隙缺陷态.(Gaqq3).的荧光激发带位于380～456nm,荧光发射峰位于568nm,为橙红光发射.光学带隙2.49 eV.与Gaq3相比,荧光强度有所减弱,这是由于次甲基相连的两个喹啉环的扭曲导致了(Gaqq3)n的刚性和共平面性不好;由于分子共轭体系的增大,使(Gaqq3)n分子的π电子更加离域化,导致了荧光发射峰发生了红移.(Gaqq3)n有望在有机电致发光器件和有机光伏器件中得到应用.     

Effect of different types of pseudopotentials on study of electronic dispersion for graphene and a (5,5) SWCNT

We study the electronic dispersion for a graphene sheet and also a (5,5) single wall carbon nanotube (SWCNT) by using the PWscf code from the ‘Quantum Espresso’ package. Two different types of pseudopotentials, ‘norm conserving’ and ‘ultra soft’, have been employed and the results are more or less similar up to the Fermi level. By energy relaxation, it was found that, if the inter-layer distance of graphite expands up to 4.5 times its in-layer (hexagonal) lattice constant, then each layer can be considered as an individual graphene sheet and, in a bundle of (5,5) SWCNTs, the optimum separation between the tubes’ centers is about 19 a.u. and, if it expands to 22 a.u., then a single wall tube consideration can be made. The calculated band structure and density of states (DOS) for the (5,5) SWCNT show that in the vicinity of the Fermi level there is no energy gap (so that it is metallic) and there is a general agreement between them and zone-folding studies or other ab initio methods in the literature. The effects of curvature on the band shifts and DOS have been considered, and they magnify the departure from Mintmire and White’s universal prediction. PACS  71.20.Tx; 71.15.Mb; 73.61.Wp     

Nanomechanical properties and phase transitions in a double-walled (5,5)@(10,10) carbon nanotube: ab initio calculations

The structure and elastic properties of (5,5) and (10,10) nanotubes, as well as barriers for relative rotation of the walls and their relative sliding along the axis in a double-walled (5,5)@(10,10) carbon nanotube, are calculated using the density functional method. The results of these calculations are the basis for estimating the following physical quantities: ultimate shear strengths and diffusion coefficients for relative sliding along the axis and rotation of the walls, as well as frequencies of relative rotational and translational oscillations of the walls. The commensurability-incommensurability phase transition is analyzed. The length of the incommensurability defect is estimated on the basis of ab initio calculations. It is proposed that a double-walled carbon nanotube be used as a plain bearing. The possibility of experimental verification of the results is discussed.     

An ENDOR study of radical spin adducts derived from novel 2-substituted-5,5-dimethyl-pyrroline-N-oxide spin traps

ENDOR spectra of a series of carbon- and oxygen-centered radical adducts of 2-substituted DMPO-type nitrones are reported. They include the novel cyclic nitrones, 2-phenyl-5,5-dimethyl-pyrroline-N-oxide (2-Ph-5,5-M₂PO), 2,5,5-trimethyl-l-pyrroline-N-oxide (2,5,5-M₃PO), and 2-phenyl-3,3,5,5,-tetramethyl-l-pyrroline-N-oxide (2-Ph-3,3,5,5-M₄PO). Electron paramagnetic resonance (EPR) was used to ascertain the nitrogen hyperfine splittings (hfs’s) while¹H ENDOR was employed to determine the long-range (γ) hydrogen hfs’s. The magnitude of the nitrogen hfs combined with the numbers and sizes of the long-range γ-H hfs’s of spin adducts of these new spin traps are shown to help disclose the identities of various added radicals (or radical addends). It should be noted that the three new spin traps presented here are keto-nitrones not aldo-nitrones. Thus, there is alkyl (e.g. CH₃) or aryl (e.g. C₆H₅) substitution at the 2-position of the pyrroline-N-oxide ring. This feature is part of our search for modified spin traps that yield spin adducts with greater stability.     

Mechanical Properties of Single-Walled （5,5） Carbon Nanotubes with Vacancy Defects

First-principles simulation is used to investigate the structural and mechanical properties of vacancy defective single-walled （5,5） carbon nanotubes. The relations of the defect concentration, distribution and characteristic of defects to Young＇s modulus of nanotubes are quantitatively studied. It is found that each dangling-bond structure （per supercell） decreases Young＇s modulus of nanotube by 6.1% for symmetrical distribution cases. However the concentrative vacancy structure with saturated atoms has less influence on carbon nanotubes. It is suggested that the mechanical properties of carbon nanotubes depend strongly upon the structure and relative position of vacancies in a certain defect concentration.     

3,3‘,5,5’—四甲基联苯胺——β—环糊精包合物的紫外—可见光谱和电？…

本文采用紫外－可见光谱和电化学的方法研究了３,３’,５,５’－四甲基联苯胺（ＴＭＢ）和β－环糊精形成超分子包合物后的氧化还原性质,研究结果表明在形成包合物后ＴＭＢ的氧化还原特性更好,尤其是在有酶参与时更易被氧化。在包合物内的氧化产物组分更单纯,修饰在电极表面也表现出更好的氧化还原活性。     

Theoretical characterization of axial deformation effects on hydrogen storage of Ti decorated armchair (5,5) SWCNT

Theoretical calculations have been performed in the framework of density functional theory to characterize the effect of axial deformation on hydrogen storage of Ti decorated armchair (5,5) SWCNT. The theoretical characterization has been carried out in terms of H₂ adsorption energies that are lying in the desirable energy window (?0.2 to ?0.6?eV) recommended by DOE, as well as a variety of physicochemical properties. A remarkable and significant change in H₂ adsorption energy is observed under the effect of only (1%) axial strain. Axial relaxation leads to H₂ adsorption energies within the recommended energy range for hydrogen storage, in contrast to axial compression. Simultaneous weakening of π and σ interactions, due to the effect of axial relaxation and loss of spatial orbital overlap, is in favor of hydrogen adsorption in the recommended energy range, and dominates the effect of charge transfer from Ti 3d to C 2p of the SWCNT. The calculated pairwise and non pairwise additive components confirm that the role of the SWCNT is not restricted to supporting the metal. Polarizability and hperpolarizabilty calculations as well as spectral analysis characterize the relaxed structure (Z?=?1.02), for which H₂ adsorption energy (?0.34?eV) is in the recommended energy range for hydrogen storage, to be energetically more preferable than the compressed structure (Z?=?0.99). The results offer a way to control and characterize the hydrogenation process of metal functionalized SWCNTs by strain loading.     

Spectrophotometric Determination of Cobalt (II) Using 5,5-Dimethyl-1,2,3- Cyclohexanetrione 1,2-Dioxime 3- Thiosemicarbazone

The reagent 5,5-dimethyl-1,2,3-cyclohexanetrione 1,2-dioxime 3-thiosemicarbazone (DCDT) has been used for the spectrophotometrie determination of cobalt (II). Various factors affecting the sensitivity of this determination have been studied. These factors include wavelength, standing time and pH. The range of applicability of Beer's law on this determination has been concluded and its sensitivity has been calculated and compared with other reagents used for     

胞嘧啶与3,3',5,5'-四溴间甲酚磺酞反应体系研究

采用UV-Vis法对胞嘧啶(Cy)与3,3',5,5'-四溴间甲酚磺酞(XJFL)反应体系进行了研究.研究了在酸性条件下温度、时间、离子强度等对反应体系的影响;测得反应的线性范围为0～32μg·mL-1,最大结合数n=16,摩尔吸光系数ε=1.32×103 L·cm-1·mol-1等;并对反应机理进行了研究.同时测定了无机物,生物物质,表面活性剂对反应体系的干扰情况.     

新型蓝色荧光材料5,5',6,6'-四苯基-2,2'-联吡嗪的制备和发光性质

以乙二胺和二苯乙二酮为原料合成了5,6-二苯基-2,3-二氢吡嗪(Dpdhpz),Dpdhpz在Ir Cl3·3H2O或三氟化硼乙醚等路易斯酸作用下发生自身氧化偶联得到了5,5',6,6'-四苯基-2,2'-联吡嗪(Dbppz)。在四氢呋喃(THF)溶液中,Dbppz的光致发光(PL)为深蓝色,最大发射峰位于400 nm,CIE坐标为(0.16,0.03)。Dbppz在THF溶液中最大量子效率为89%,在聚苯乙烯薄膜(Dbppz质量分数5%)中的量子效率为78%。将Dbppz制备成器件结构为ITO/HAT-CN(5 nm)/NPB(40 nm)/Dbppz(20 nm)/Tm Py PB(40 nm)/Li F(1 nm)/Al(100 nm)的非掺杂电致发光器件。实验发现,该非掺杂器件并没有产生预期的蓝色发光,而是意外地得到了一个白光器件。我们推测产生白光发射的原因与发光层和空穴传输层之间相互作用有关。由于空穴传输层NPB的芳胺结构具有电子给体性质,而Dbppz的吡嗪结构具有电子受体结构,发光层与空穴传输层的界面发生了电子给体和电子受体的相互作用,形成了激基复合物。在电致发光(EL)光谱中,除了Dbppz发光材料在415 nm的发射外,在550 nm还出现强的激基复合物的发射。激基复合物的产生使得EL发射出现了长波长光谱,同时减弱了发光层的"本征"发光。蓝色"本征"发光与激基复合物的黄色发光构成了一个CIE坐标值为(0.27,0.33)(亮度100 cd/m2)的白光器件。器件最大外量子效率、最大功率效率和最大电流效率分别为44%、0.74 lm/W和1.04 cd/A。     

高压下1,1’-二羟基-5,5’-联四唑二羟胺盐的振动光谱及同位素效应

用密度泛函理论方法研究1,1’-二羟基-5,5’-联四唑二羟胺盐(HATO)晶体在高压(<40 GPa)下性质。在GGA-PW91计算水平并结合超软势基组对HATO晶体结构进优化,其优化结构能再现实验结果。分子间O…H间距随压力的增加而显著减小;但O—H和N—H键长呈现非单调变化。基于不同压力下的优化晶体结构,利用非周期性计算并经校正因子0.967 9校正,求得相应压力下的红外和拉曼谱。预测最强拉曼峰对应于C—C伸缩和NH₂对称变形,位于1 580 cm-1,与实验结果一致。虽然阴离子不含氢原子,但阳离子的氘代仍对阴离子的振动光谱产生影响。高压导致分子间氢键增强,导致参与氢键的O—H和O—D振动的拉曼波数减小。氘代后,ND₂的拉曼位移的最明显变化是ν₂伸缩振动波数在高压下急剧增加,导致ND₂ ν₂/ν₃在高压下发生偶合。计算出的ν₁至ν₃振动的同位素效应比ν(NH₂)/ν(ND₂)均为1.36～1.38,与由折合质量所求得的值相一致。氘代和压力的变化可引起不同振动模式的偶合。     

Island formation and manipulation of prochiral azobenzene derivatives on Au(111)

Based on previous work with very similar azobenzene derivatives, this study of para-TBA (2,2',5,5'-tetra-tert-butylazobenzene) molecules aims to identify single intact molecules and investigate their adsorption behavior on a Au(111) surface. The molecules are found to be mobile on the surface at the deposition temperature, leading to highly ordered and enantiomerically pure molecular islands. Voltage pulses between the surface and the tip of a scanning tunneling microscope are used to change the chirality of the adsorbate molecules. On the Cu(111) surface instead, single molecules are found on the terraces, which points to a stronger molecule-substrate interaction.     

Widely tunable broadband terahertz radiation generation using a configurationally locked polyene 2-[3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene] malononitrile crystal via difference frequency generation

Widely tunable terahertz (THz) waves were successfully generated from 0.5 to 10 THz via difference frequency generation (DFG) in a configurationally locked polyene 2-[3-(4-hydroxystyryl)-5,5-dimethylcyclohex-2-enylidene] malononitrile (OH1) crystal. Potassium titanium oxide phosphate optical parametric oscillator pumped by nanosecond Q-switched Nd:YAG laser was used to generate two waves, which were then used to irradiate OH1 crystal. The maximum energy of the generated THz wave was about 461 pJ/pulse. We investigated the dependency of generated THz energy to the excitation pump power density and OH1 crystal thickness. In addition, we compared the THz energy generated by OH1 crystal to 4-N,N-dimethylamino-4′-N′-methyl-4-stilbazolium tosylate (DAST) crystal using DFG, and we achieved 560 times higher energy using OH1 crystal than DAST crystal at around 1.1 THz.     

Size effect of quantum conductance in single-walled carbon nanotube quantum dots

The quantum conductance of two kinds of carbon nanotube quantum dots (CNQD) composed of (5,5) and (10,0) tubes, namely (10,0)/(5,5)/(10,0) and (5,5)/(10,0)/(5,5) with different quantum sizes, are calculated. It is shown that for (10,0)/(5,5)/(10,0) CNQD, one on-resonant peak at the Fermi energy exists only for special QD sizes, and the width of the conductance gap increases from 1.0 eV to 3.2 eV with the increase of size. The positions of peaks around the Fermi energy are obtained by the electronic structure of individual finite (5,5) tubes. We also find that the (5,5)/(10,0)/(5,5) CNQDs behave as a quantum dot, and its localized QD states are different from that of the former CNQD because of the existence of the interface states between (5,5)/(10,0) junctions. For (5,5)/(10,0)/(5,5) CNQD, there is no conductance gap with QDs size smaller than 7 layers, and the conductance peak around the interface quasilocalized state -0.26 eV disappears with QD sizes larger than 23 layers. In addition, for the (5,5)/(10,0)/(5,5) CNQD, the connection method can change the degree of electronic localization of intermediate (10,0) tube.Received: 8 August 2003, Published online: 23 December 2003PACS: 61.48. + c Fullerenes and fullerene-related materials - 71.20.Tx Fullerenes and related materials; intercalation compounds - 72.80.Rj Fullerenes and related materials - 68.55.Ln Defects and impurities: doping, implantation, distribution, concentration, etc.     

高压对氮化硼纳米管的几何结构、电子结构和光学性质的影响

运用密度泛函理论平面波赝势方法(PWP)和广义梯度近似(GGA),计算研究了纳米管BN(5,5)在不同压力条件下的几何结构、电子结构和光学性质. 在高压条件下管口形状发生了较大的变化. 与闪锌矿结构BN比较分析发现两种结构间存在一些性质上的差异：首先,在外压力作用下,BN(5,5)纳米管的带隙随压力增大而减小,变化率为-0.01795eV/GPa,而闪锌矿结构BN随压力增大而增大;其次光吸收谱在压力条件下,没有和闪锌矿结构BN一样发生“蓝移”,相反在红外方向有所拓展;但纳米管BN(5,5)电子的转移方向和 关键词： 氮化硼纳米管 密度泛函理论(DFT) 电子结构     

Star-shaped discotic compounds with tetrazole and oxadiazole fragments

ABSTRACT

Two series of star-shaped discotic compounds (A and B) were studied to establish the relationship between their molecular structure and mesogenity. Series A included 19 three-arm compounds with known mesomorphism. Series B consisted of 132 new compounds with unknown mesomorphism: pyromellitic and cyanuric acid derivatives, 5,5′-azo-bis-isophthalic and 4,4′-azodiphthalic acids and triphenylene derivatives. The columnar mesomorphism prediction data for both series were obtained using the original program СМР ChemCard. The prediction data for series A are in good agreement with the experimental results and the reliability of the prediction was estimated to be 89.5%. The same method was applied for series B. The prediction results were approved by the synthesis of individual representatives of series B. A good correlation of the prediction with the experimental data was revealed.