Trimerization of Acetylene and Alkene:Rapid Access to Polyenes

Conjugated polyene motifs are ubiquitous in various natural products and functional molecules;however,their synthesis is very challenging because of the required lengthy and time-consuming processes.We herein report an efficient approach for the synthesis of(E,E)-trienes via cationic rhodium catalysis using acetylene and simple alkenes bearing diverse directing groups as the starting materials.The reaction featured high step economy,excellent functional group compatibility,and exclusive stereoselectivity.Various directing groups such as carbonyl,sulfone,phosphate,hydroxyl,and amino were compatible.Furthermore,the triene products allowed versatile elaborations,providing rapid and convenient access to several important bioactive molecules,including vitamin A,(+)-roxaticin,and other complex polyenes.Mechanistic experiments showed that the directing group on the alkene played a crucial role in the reaction.

Catalytic Trimerization of Ethylene with Highly Active Half-sandwich Titanium Complexes Bearing Pendant p-Fluorophenyl Groups

Two new complexes [η^5-C5H4CMe2-（p-fluorophenyl）]TiCL3 （1） and [η^5-C4h4C（cyclo-C5H10）-（p-fluorophenyl）]TiCl3 （2） were synthesized and characterized. Their activities and selectivities for trimerization of ethylene were investigated. The introduction of fluorine atom greatly weakened the arene coordination, but this disadvantageous factor can be eliminated by introduction of a bulky substituent, such as cyclo-C5H10, to the bridging carbon linked to the Cp ring. The combinative effect of the fluorine substitute and the bridging unit can make complex 2 as a highly active and selective catalyst for ethylene trimerization. Its productivity and selectivity for 1-hexene can reach 1024.0 kg·mol^-1·h^-1 and 99.3% respectively.

名校长工作室TRIMER研修模式助力乡村区域教育质量提升——以保定市贫困县(脱贫县)系列名校长工作室为例

如何以名校长工作室方式助推乡村教育质量提升,河北省保定市贫困县(脱贫县)系列名校长工作室项目组形成的TRIMER(三聚体)研修模式进行了很好的探索。TRIMER模式在研修功能定位上强调校长成长、学校提质与区域教育优化三位一体;在研修方式上,培训、改进、辐射等三线交织;在研修原则上,培训与改进、个人研修与团队研修、素养提升与辐射带动有机结合;在培养主体上,保定市本土优秀校长的示范、北京市双导师的引领与京保教育行政的保驾护航相得益彰;在运行力量上,行政力量、学术力量、校长自我发展力量密切配合。

Ce^(3+)掺杂对NaYF_(4)∶Yb^(3+),Tm^(3+)纳米粒子上转换发光性能的影响及其荧光温度特性应用

采用溶剂热法制备了一系列不同Ce^(3+)含量的Yb^(3+)/Tm^(3+)/Ce^(3+)共掺NaYF_(4)纳米粒子。样品在980 nm激光激发下,可以观察到强烈的上转换蓝色荧光。探究了不同Ce^(3+)含量对发光强度的影响,发现在Ce^(3+)含量从0%增加到0.5%的过程中,紫外到可见的上转换发光随着Ce^(3+)浓度的增加先增强后减弱,在0.2%时荧光达到最强,比不掺Ce^(3+)时荧光增强高达5倍左右,其中475 nm的蓝光更是增强了6倍。此外,对其机理进行了深入细致的探究,一方面,掺杂Ce^(3+)后,Tm^(3+)中的(^(3)F_(3),^(3)H_(4))与Ce^(3+)中的(^(2)F_(7/2),^(2)F_(5/2))发生交叉弛豫,有效地防止了电子跃迁回到基态,以致整体荧光明显增强;另一方面,当掺入Ce^(3+)后,形成的(Yb^(3+)-Yb^(3+)-Ce^(3+))Trimers把能量传递给^(1)G_(4)能级,发出475 nm的蓝光,导致蓝光很强。将其应用于荧光强度比测温,绝对灵敏度高达0.0350 K^(-1)。

Ultrafast Energy Transfer in Artificial Antenna Molecule Measured by Transient Fluorescence Spectroscopy

We have reported previously the ultrafast energy transfer process with a time constant of 0.8 ps from a monomeric to a dimeric subunit within a perylenetetracarboxylic diimide trimer, which was derived indirectly from a model fitting into the transient absorption experimental data. Here we present a direct ultrafast fluorescence quenching measurement by employing fs time-resolved transient fluorescence spectroscopy based on noncollinear optical parametric amplification technique. The rapid decay of the monomer＇s emission due to energy transfer was observed directly with a time constant of about 0.82 ps, in good agreement with the previous result.

Insight into Medicinal Chemistry Behind Traditional Chinese Medicines: p-Hydroxybenzyl Alcohol-Derived Dimers and Trimers from Gastrodia elata

From an aqueous extract of“tian ma”(the steamed and dried rhizomes of Gastrodia elata),ten new compounds gastrodiben-zins A−D(1−4)and gastrotribenzins A−F(5−10),along with known analogues(11−20),having structure features coupling between two and three p-hydroxybenzyl-derived units via carbon-and/or ether-bonds,were isolated and characterized by spectroscopic data analysis.Meanwhile,the new compounds 5a,6a,8a,22,and 23,as well as the known derivatives 13a,14a,15,17−21,24,25,and p-hydroxybenzyl aldehyde were isolated and identified from a refluxed aqueous solution of p-hydroxybenzyl alcohol.Methylation of 5a and 6a in methanol and ethylation of 6a,8a,13a,and 14a in ethanol produced 5 and 6 and 7,8,13,and 14,respectively.using ultra-performance liquid chromatography high-resolution electrospray ioniza-tion mass spectrometry(UPLC-HRESIMS)analysis of the refluxed solutions of p-hydroxybenzyl alcohol and the refluxed extracts of the fresh G.elata rhizome and“tian ma”extracts indicated consistent production and variation of the dimeric and trimeric derivatives of p-hydroxybenzyl alcohol upon extracting solvents and refluxing time.In various assays,the dimeric and trimeric derivatives showed more potent activities than p-hydroxybenzyl alcohol itself and gastrodin,which are the main known active constituents of“tian ma”.These results revealed for the first time that the more effective dimers and trimers can be produced through condensation of the co-occurring p-hydroxybenzyl alcohol during processing and decocting of the G.elata rhizomes,demonstrating insights into medicinal chemistry behind application protocols of traditional Chinese medicines.

One New A-type Proanthocyanidin Trimer from Lindera aggregata(Sims) Kosterm.

One new A - type proanthocyanidin trimer, lindetannin trimer, was isolated from the stems of Lindera aggregata (Sims) Kosterm.. Its structure was elucidated by spectral and chemical methods.

Synthesis, Crystal Structure and Gas Adsorption of a Trimeric Nickel-based Coordination Polymer

A trimeric porous coordination framework [Ni_3(TPTC)(IN)_2(μ_2-H_2O)_2(CH_3OH)_2)]n· x(solvents)(1, TPTC = terphenyl-3,3?,5,5??-tetracarboxylic acid, IN = isonicotinic acid) was synthesized and characterized by elemental analysis, infrared spectroscopy, thermogravimetric analysis, single-crystal and powder X-ray diffraction. It crystallizes in monoclinic space group C2/c with a = 33739(12), b = 14.820(5), c = 13.568(5) ?, β = 97.388(6)o, V = 6728(4) ?3, Z = 4, Mr = 965.35, Dc = 0.953 g·cm^(-3), F(000) = 1955.5, μ = 0.881 mm^(–1), GOOF = 1.072, the final R = 0.0859 and w R = 0.2424 for 5284 observed reflections with I > 2σ(I). The structure of 1 is constructed from the linkage of trinuclear {Ni_3} second building units through TPTC and IN spacers, forming a 4,8-connected network of Schl?fli symbol {32.42.52}{34.46.58.68.72}. The CO2 uptake values for 1 are 97.9 m^2·g^(-1) at 273 K and 66.2 m^2·g^(-1) at 298 K, while its N_2 adsorption values are 8.5 m^2·g^(-1) at 273 K and 4.9 m^2·g^(-1) at 298 K, respectively. These results show that 1 has high CO_2/N_2 adsorption selectivity at ambient conditions.

Synthesis,liquid crystalline and luminescent properties of trimeric phenylenevinylene with end-groups of(R)-(+)-2-methylbutyric acid ester

The trimeric phenylenevinylene with the symmetrical chiral end-groups （ChTPV） was synthesized. The liquid crystalline and luminescent properties of the ChTPV have been studied by differential scanning calorimetry （DSC）, polarized optical microscopy （POM）, absorption and photoluminescence spectra. The results indicated that the ChTPV exhibits mesophase over a wide temperature range and a typical optical texture of smectic phase. In contrast with the spectra of the solution, that of the film showed blue-shift in maximal absorption and red-shift in maximal emission due to H-type aggregation with parallel alignment of the TPV transition dipole moment.

Toughening Modification of Unsaturated Polyester Resin Using HDI Trimer

HDI trimer was firstly used to improve the mechanical properties of hydroxyl-terminated unsaturated polyester （UP）. Mechanical properties measurements performed on the cured materials demonstrate a distinct improvement in intensity and toughness in the presence of HDI trimer and shows the change trends of increase and then decrease. The morphological analysis of the fracture surfaces shows that the micro-phase separated structures appear in modified UPR systems and changed from dendritric, dimple and to cystiform structures with the increase of HDI trimer content. The presence of the cystiform structures made the modified UPR systems present the best properties.

Synthesis and Crystal Structure of a New μ-Oxamide Trimeric Hetero-tetranuclear Complex

A novel oxamide-bridged trimeric tetranuclear complex 1 incorporating a macro- cyclic oxamide of formula {[(CuL)3Mn](ClO4)2}3 (macrocyclic oxamide L = 2,3-dioxo-5,6,14,15- dibenzo-1,4,8,12-tetraazacyclopentadeca-7,12-diene) was prepared and structurally characterized. The compound [(CuL)3Mn](ClO4)2 crystallizes in the trigonal system, space group P 3 with a = 22.434(17), b = 22.434(17), c = 18.82(2) ?, α = β = 90, γ = 120o, V = 8203(13) ?3, Z = 6, Dc = 1.751g/cm3, μ(MoKα) = 1.557, F(000) = 4392, the final R = 0.083 and wR = 0.1727 for 9604 obser- ved reflections with I > 2σ(I). The single-crystal X-ray analysis shows that 1 is a trimeric complex. There are three similar constitutes, dissimilar conformations and asymmetrically independent ‘building-block’ [(CuL)3Mn] in one crystal cell of the title complex 1.

Investigation of Light-harvest Material:Synthesis and Characterization of Nanometer Porphyrin Trimer

ω -Bromopropylporphyrin ether synthesized from the raction of 1,3-dibromopropane as the bridge-linked reagent and 5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (H_2MHTPP) as the matrix reacts with 5,15-di(4- hydroxyphenyl)-10,20-diphenyl porphyrin( trans -H_2DHDPP) to give the title nanometer porphyrin trimer. The characterization was carried out by means of elemental analyses,UV-Vis,IR, 1H NMR and XRD.

Antioxidant Nature Adds Further Therapeutic Value: An Updated Review on Natural Xanthones and Their Glycosides

Plants have so much to offer as far as the discovery of new bioactive molecules is concerned.Among the several classes of phytochemicals,xanthones offer greater structural diversity and pharmacological value.They are variable but definitely antioxidant in nature.Thus they are attractive targets for natural product and medicinal chemists.Xanthones and their glycosides possess broad spectrum interesting biological activities,such as cytotoxic,anti-inflammatory,antioxidant,anti-bacterial,neuroprotective,anti-HIV,enzyme inhibition,and hypoglycemic.The radical scavenging ability of these molecules accounts for most of their added therapeutic values.This paper intended to serve as a guide for future endeavors in quest for these molecules.Structure-Activity Relationship(SAR)and mechanism of action is given for better understanding of their role as pharmacological agents.The most recent advances in the isolation of bioactive xanthones and their glycosides were presented here.This paper will assist in directed approaches towards the discovery of analogues of xanthones.

Modified Bean Seed Protein Phaseolin Did Not Accumulate Stably in Transgenic Tobacco Seeds after Methionine Enhancement Mutations

The major seed storage protein phaseolin of common bean (Phaseolus vulgaris L.) is deficient in methionine, an essential amino acid for human and animal health. To improve the nutritional quality of common bean, we designed methionine enhancement of phaseolin based on the three-dimensional structure of protein, de novo design principles and genetic information. Amino acid substitution and loop insertion were targeted to the interior and exterior, respectively, of the protein’s β-barrels. First, we introduced the methionine enhancement mutations into phaseolin cDNA, expressed cDNA in Escherichia coli and purified monomeric non-glycosylated proteins. Biophysical analysis of E. coli-expressed proteins demonstrated a similar structural stability of wild-type and mutant phaseolin monomers. Here, we attempted to test the structural stability of the methionine-enhanced phaseolin by introducing phaseolin cDNA to tobacco via Agrobacterium tumefaciens-mediated transformation of leaf disks, regenerating transgenic tobacco plants, and examining the accumulation of phaseolin protein in mature transgenic tobacco seeds. We used seven constructs containing different extents of methionine enhancement, ranging from the original 3 to maximum 33 methionines per 397 amino acid residues. ELISA analyses indicated that the methionine-enhanced phaseolins did not accumulate as stably in mature transgenic tobacco seeds as the wild-type phaseolin. It seems likely that the methionine-enhanced phaseolin proteins were under the stringent scrutiny of the protein quality control mechanism in the endoplasmic reticulum (ER), Golgi complex and/or vacuolar protein bodies. The protein degradation is probably to occur in the vacuolar protein bodies due to the instability of the trimer assembly caused by the methionine enhancement mutations targeting either amino-acids substitutions or/and loop insertions to the interior β-sheets and tum/loop regions, respectively, of N- and C-barrel structures.

Fluorescence and Thermostability of Nanometer Porphyrin Trimer

A nanometer porphyrin trimer was firstly synthesized with 1 ,3-dibromopropane as a bridge-linked agent and the fluorescence property and thermostability were studied. The results show that the fluorescence property and thermostability of the trimer are different from those of monoporphyrin. The effects of the molecule structure on the optical property and the thermostability were also studied in detail.

Tunable Fano resonances and plasmonic hybridization of gold triangle–rod dimer nanostructure

A gold dimer structure consisting of a notched triangle nanoslice and a rectangle nanorod is proposed to produce distinct Fano resonance. Owing to the coupling between the dipole plasmon mode of the nanorod and the dipole or quadrupole plasmon mode of the nanoslice, the extinction spectrum with a deep Fano dip is formed and can be well fitted by the Fano interference model for different geometry parameters. In addition, Fano resonance of the gold dimer nanostructure also intensely depends on the polarization direction of incident light. Moreover, Fano resonance of the triangle–rod trimer is also analyzed by adding another nanorod into the former dimer and exhibits the splitting of plasmonic resonant peak in high order coupling modes. The plasmonic hybridizations in these nanostructures have been analyzed for revealing the physical origin of the Fano resonance.

Microstructured hydroxyl environments and Raman spectroscopy in selected basic transition-metal halides

Raman vibrational spectra of the selected basic （hydroxyl OH and deuteroxyl OD） transition-metal halides, geomet- rically frustrated material series α-, β-, γ-Cu2（OH）3Cl, α-Cu2（OH）3Br, β-Ni2（OH）3Cl, β-Co2（OH）3Cl, β-Co2（OH）3Br, γ-Cu2（OD）3Cl, and β-Co2（OD）3Cl are measured at room temperature and analysed to investigate the relationship be- tween the microstructured OH environments and their respective Raman spectra. Among these selected samples, the last two are used to determine the OH stretching vibration region （3600 cm-1-3300 cm-1） and OH bending vibra- tion region （1000 cm-1-600 cm-1） of OH systems in the spectra. Through the comparative analysis of the distances d（metal-O）, d（O-halogen）, and d（OH）, the strong metal-O interaction and trimeric hydrogen bond （Car, C8 or C1 symmetry） are found in every material, but both determine simultaneously an ultimate d（OH）, and therefore an OH stretching vibration frequency. According to the approximately linear relationship between the OH stretching vibration frequency and d（OH）, some unavailable d（OH） are guessed and some doubtful d（OH） are suggested to be corrected. In addition, it is demonstrated in brief that the OH bending vibration frequency is also of importance to check the more detailed crystal microstructure relating to the OH group.

Surfactant scouring wastewater modified bentonites—promising material for unmanageable wastewater treatment

Trimeric quaternary ammonium surfactants are newly developed surfactants, their widespread synthesis and utilization results in a great amount of scouring wasterwater of high COD, which is unmanageable. The present investigation aims to fred a new type of organo-bentonites modified by the scouring wastewater and to treat the scouring wastewater at the same time. Results of adsorption experiments of phenol and formaldehyde by the modified bentonite show that, at the optimal ratio 24% （W/V） of modified bentonite to scouring wastewater, the removal rate of phenol and formaldehyde by FTAT scouring wastewater modified bentonite is 3.53 times and 2.48 times higher than that of Na-bentonite, and the COD of treated scouring wastewater reduces to below 200 mg/L, meeting the second level of Standards for Discharge of Water Pollutants from the Ammonia Industry of China.

Raman and mid-infrared spectroscopic study of geometrically frustrated hydroxyl cobalt halides at room temperature

Mid-infrared absorption and Raman spectra of the geometrically frustrated material series, hydroxyl cobalt halides β-CO2（OH）3Cl and β-CO2（OH）3Br, are first, to the best of our knowledge, measured at room temperature, to study the corresponding relationship between their vibrational spectral properties and crystal microstructures. Through the comparative analysis of the four spectra we have categorically assigned the OH-related vibration modes of hydroxyl groups in the trimeric hydrogen bond environment （Co3 =OH）3 … Cl/Br, and tentatively suggested vibration modes of O-Co-O, Co O and Cl/Br-Co-Cl/Br units. These results can also become the basis for analysing their low-temperature spectral properties, which can help to understand the underlying physics of their exotic geometric frustration phenomena around phase transition temperatures.

Exciton transfer dynamics in a trimer system

We study exciton transfer dynamics in a trimer system by investigating excitation transfer probability （ETP）. We calculate ETP in the zero-temperature limit and theoretically predict the environment-assisted quantum critical effect, in which ETP exhibits a sudden change at the critical point of quantum phase transition for the trimer. In particular, we find that the steady-state ETP can be observed in the presence of the environment interaction.