Synthesis,X-ray Structure,Spectroscopic Properties and DFT Studies of a Novel Schiff Base

A series of Schiff bases, salicylideneaniline derivatives 1–4, was synthesized under mild conditions and characterized by ¹H NMR, HRMS, UV-Vis and fluorescence spectra, and single-crystal X-ray diffraction. In solid and aprotic solvents 1–4 exist mainly as E conformers that possess an intramolecular six-membered-ring hydrogen bond. A weak intramolecular C–H···F hydrogen bond is also observed in fluoro-functionalized Schiff base 4, which generates another S(6) ring motif. The C–H···F hydrogen bond further stabilizes its structure and leads it to form a planar configuration. Compounds 1–3 exhibit solely a long-wavelength proton-transfer tautomer emission, while dipole-functionalized Schiff base 4 shows remarkable dual emission originated from the excited-state intramolecular charge transfer (ESICT) and excited-state intramolecular proton transfer (ESIPT) states. Furthermore, the geometric structures, frontier molecular orbitals (MOs) and the potential energy curves for 1–4 in the ground and the first singlet excited state were fully rationalized by density functional theory (DFT) and time-dependent DFT calculations.     

可溶性的含羧基苝酰亚胺类化合物的合成及其光谱性质研究

本文主要以酐(1)为起始物,通过在环母体结构的1、6、7、12位上引入苯氧基和对甲基苯氧基合成了另外两种酐化合物(2a和2b);所得到的酐化合物与6-氨基已酸进行反应,合成了3种可溶性的含有羧基的酰亚胺化合物(3a、3b和3c),使用红外、紫外、荧光1、H-NMR,元素分析对所合成的化合物进行了表征.经研究发现,环母体结构的1、6、7、12位上苯氧基和对甲基苯氧基的引入,能使得所合成的含羧基酰亚胺类化合物的最大吸收波长分别红移了44.1 nm和50.1 nm;Stokes位移变大,分别为34.1 nm和30.0 nm;而荧光量子产率有所降低但下降趋势不明显.     

Highly soluble perylene dyes: Synthesis, photophysical and electrochemical characterizations

Highly soluble perylene diimide derivatives with symmetrical and unsymmetrical secondary, tertiary alkyl side chains were synthesized and their photophysical properties, redox potentials and thermal stabilities were measured and compared with previously reported 1-pentylhexyl substituted swallow-tailed perylene diimide. Diasteroisomers of the novel, unsymmetrical swallow-tailed substituted perylene diimide compound could not be detected using low temperature NMR spectroscopy. The novel dyes were soluble in a range of organic solvents indicating potential for photo-electronic applications and photocatalytic reactions. Two dyes were not only soluble in organic solvents but also showed solubility in aqueous media as the hydrochloride salt, thus offering potential use in biological applications.     

含噻吩环1,2,4-噁二唑类衍生物的合成及光电性能

以硫代二甘酸和取代苯甲腈为原料,经酯化、环化、酸化等反应合成了2,5-双[3-苯基-1,2,4-噁二唑-5-基]-3,4-二丁氧基噻吩衍生物,通过1HNMR、FTIR和元素分析进行了结构表征,并考察了该系列化合物的紫外-可见吸收光谱、荧光发射光谱及电化学性质。该系列化合物紫外吸收出现在240～250nm和320～350nm两个波段;荧光发射峰位于395～401.5nm,且随苯环上取代基供电子性的增强而规律性红移;循环伏安测定结果表明,该系列化合物中ⅧA、ⅧB、ⅧC和ⅧF具有高于常用电子传输材料2-(4-联苯基)-5-对叔丁基苯基-1,3,4-噁二唑(PBD)的电子亲和势,因而该类化合物的研究,对设计小分子类电致发光材料有重要意义。     

Zn3V2O8的电子结构与光学性质的理论研究

采用平面波超软赝势密度泛函理论的方法研究了Zn3V2O8的能带结构、电子态密度和光学特性.能带结果显示Zn3V2O8呈间接带隙的绝缘体型能带,其禁带宽度为2.9 eV.详细的电子态密度结果显示其费米面上的态密度达到20 e/eV,费米能级附近的能级由Zn3p、V3p和O2p电子形成,Zn3d和O2s之间有强的杂化作用.介电性能结果显示在4.4 ～5.7 eV附近有强的吸收峰,在20.6 eV附近有一个次强吸收峰;吸收光谱显示在6.8 eV处有强吸收,在20.7 eV处有一个较弱的吸收峰.     

Synthesis, conformation and biological evaluation of the enantiomers of 3-fluoro-gamma-aminobutyric acid ((R)- and (S)-3F-GABA): an analogue of the neurotransmitter GABA

Gamma-aminobutyric acid or GABA (1) is one of the major inhibitory amino acid neurotransmitters of the central nervous system. This article describes the first synthesis of both the (R)- and (S)- enantiomers of 3-fluoro-GABA (2, 3F-GABA). DFT calculations were carried out in a continuum solvent model (PCM-B3LYP) to estimate the preferred conformations of 3F-GABA in aqueous solution. NMR coupling constants were calculated for each conformer and were then used to simulate the NMR spectra to evaluate the solution conformation of 3F-GABA. A preliminary evaluation of the 3F-GABA enantiomers shows that they act similarly as agonists of cloned GABA(A) receptors; however, they behave quite differently in a whole animal (Xenopus laevis tadpole model).     

Singlet oxygen quenching activity of furan fatty acids: Kinetic and thermodynamics study

We have undertaken a detailed study of the reactivity of furan fatty acids (F-acids) with singlet oxygen (¹O₂) produced by thermal decomposition of endoperoxide and photosensitizer reaction of rose bengal in ethanol. Accordingly, we measured the second order rate constant (k_Q) for the reaction of F-acids with ¹O₂. As a result, the reactivity of F-acids against ¹O₂ exhibited a decrease in the order tetra-alkyl F-acid (F₃) > tri-alkyl F-acid (F₂) > di-alkyl F-acid (NMF). In addition, we also employed the density functional theory (DFT) and quantum chemical calculations to predict the chemical reactivity, stability, and thermodynamic properties of F-acids with respect to the quenching ¹O₂. In consequence, it is clear that log k_Q values of F-acids correlate with the energy level of the highest occupied molecular orbital (E_HOMO), and HOMO of F-acids may react with the lowest unoccupied molecular orbitals (LUMO) of ¹O₂. Moreover, the reaction of F-acids with ¹O₂ proceeds spontaneously in ethanol based on the calculation by thermodynamics method. These results suggest that the F-acids may contribute to the protection of oxidative damage in animals by quenching ¹O₂.     

Stable Electrochromic Polyschiff Bases Containing Triarylamine Units: Synthesis,Electrochemical, and Acidochromic Properties

Four polySchiff bases containing different triphenylamine moieties were synthesized based on the polycondensation reaction of 4-methyl-4′,4″-diformyltriphenylamine with various aromatic diamines which contain triphenylamine groups. Especially, 4-methyl-4′,4″-diformyltriphenylamine was obtained by the reduction of compound with nitril groups with diisiobutylaluminum hydride. The structures of 4-methyl-4′,4″-diformyltriphenylamine and polySchiff bases were confirmed by Fourier transform infrared and the nuclear magnetic resonance techniques. The polySchiff bases displayed good thermal stability, with 5% weight loss above 450°C under nitrogen atmosphere. All the polymer films exhibited good electrochemical and electrochromic stability under repeatedly switching electrode voltages. Take the polySchiff base-d, for example, the color changed from the pale yellow neutral state to green and crimson oxidized state at applied potentials ranging from 0.0 to 1.6?V. The polySchiff bases showed obvious acidochromic properties. The polySchiff bases exhibited a typical photovoltaic response and good stability. Consequently, the polySchiff bases would be promising electrochromic and acidochromic materials.     

Co:CdS半导体纳米晶的合成、晶体结构及光学性质

利用水相合成技术,以巯基乙酸(MAA)为稳定剂,合成了Co:CdS半导体纳米晶.XRD结果表明,得到的掺杂纳米晶为闪锌矿结构,平均粒径约为3.9 nm;FT-IR结果表明,MAA成功包覆在Co:GdS纳米晶的表面;UV-vis吸收谱表明,Co离子成功掺入CdS品格中;PL结果表明,掺杂离子浓度过大会导致CdS发光淬灭;...     

New fluorene-based alternating copolymers with pendent N,N-diethylaniline group: Highly sensitive and selective detection for Hg with “Turn-on” fluorescence response

Two fluorene-based alternating copolymers P1 and P2 with the N,N-diethylaniline pendent group in different contents on the polymer backbone were synthesized through Suzuki Coupling Reaction, and were fully characterized by ¹H NMR, elemental analysis, and gel-permeation chromatography (GPC). Photophysical studies show that changes of the contents of the N,N-diethylaniline groups have little effect on the ground state electronic structure, but take a significant effect on the excited state. The intensities of green emission band in these polymers changes with the different content of diethylaniline groups, and are supposed to be originated from an intramolecular charge transfer process. Both of the P1 and P2 show remarkable fluorescence emission “turn-on” responses exclusively to Hg²⁺. Moreover, fluorescent titration experiments indicate that the two copolymers have high sensitivity for Hg²⁺. The coordination between metal ions and N atoms could greatly weaken the electron-donating ability of N atoms, consequently inhibit the intramolecular charge transfer process, leading to fluorescence emission enhancement. As far as we know, this is the first report for detection of Hg²⁺ with “turn-on” output signals based on polyfluorenes.     

Highly thermally stable single-component warm-white-emitting ZANP glass: Synthesis,luminescence, energy transfer,and color tunability

Luminescent glass demonstrates potential for applications as color converters in white-light-emitting diodes (W-LEDs). In this study, solution combustion synthesis combined with low-temperature melt quenching was employed as a novel route for preparing new white-light fluorescent glasses (rare-earth-doped ZnO–Al₂O₃–Na₂O–P₂O₅, ZANP). The developed solution combustion synthesis can considerably decrease the reaction temperature and time, with several advantages such as energy and time savings. X-ray diffraction and photoluminescence spectroscopy, as well as decay curves, CRI, and CCT, as well as the Commission Internationale de I′Eclairage (CIE) 1931 chromaticity coordinates, were assessed to examine the microstructure and photoluminescence properties of Tm³⁺/Dy³⁺ co-doped and Tm³⁺/Dy³⁺/Eu³⁺ tri-doped ZANP glasses for use in W-LEDs. Experimental results revealed that ZANP glass co-doped with Tm³⁺ and Dy³⁺ exhibits blue- and yellow-light emissions based on the energy transfer of dipole-dipole interaction between Tm³⁺ and Dy³⁺, which can realize the adjustment of color in a wide range. The emitting color coordinate (0.343, 0.344) of ZANP: 1.0Tm³⁺, 0.75Dy³⁺ approach ideal white light. Also, by the introduction of additional Eu³⁺ doping, ZANP:1.0Tm³⁺, 0.75Dy³⁺, 0.1%Eu³⁺ glass emit warm-white light (CCT = 3198?K) under an excitation of 361?nm. Moreover, the tri-doped ZANP glasses exhibit good thermal stability, where the luminous intensity at 498?K remains exceeding 50% of that at room temperature, and the color coordinate offset is only 2.87?×?10^?2 relative to room temperature.     

Quaternary Selenides EuLnCuSe3: Synthesis,Structures, Properties and In Silico Studies

In this work, we report on the synthesis, in-depth crystal structure studies as well as optical and magnetic properties of newly synthesized heterometallic quaternary selenides of the Eu⁺²Ln⁺³Cu⁺¹Se₃ composition. Crystal structures of the obtained compounds were refined by the derivative difference minimization (DDM) method from the powder X-ray diffraction data. The structures are found to belong to orthorhombic space groups Pnma (structure type Ba₂MnS₃ for EuLaCuSe₃ and structure type Eu₂CuS₃ for EuLnCuSe₃, where Ln = Sm, Gd, Tb, Dy, Ho and Y) and Cmcm (structure type KZrCuS₃ for EuLnCuSe₃, where Ln = Tm, Yb and Lu). Space groups Pnma and Cmcm were delimited based on the tolerance factor t’, and vibrational spectroscopy additionally confirmed the formation of three structural types. With a decrease in the ionic radius of Ln³⁺ in the reported structures, the distortion of the (LnCuSe₃) layers decreases, and a gradual formation of the more symmetric structure occurs in the sequence Ba₂MnS₃ → Eu₂CuS₃ → KZrCuS₃. According to magnetic studies, compounds EuLnCuSe₃ (Ln = Tb, Dy, Ho and Tm) each exhibit ferrimagnetic properties with transition temperatures ranging from 4.7 to 6.3 K. A negative magnetization effect is observed for compound EuHoCuSe₃ at temperatures below 4.8 K. The magnetic properties of the discussed selenides and isostructural sulfides were compared. The direct optical band gaps for EuLnCuSe₃, subtracted from the corresponding diffuse reflectance spectra, were found to be 1.87–2.09 eV. Deviation between experimental and calculated band gaps is ascribed to lower d states of Eu²⁺ in the crystal field of EuLnCuSe₃, while anomalous narrowing of the band gap of EuYbCuSe₃ is explained by the low-lying charge-transfer state. Ab initio calculations of the crystal structures, elastic properties and phonon spectra of the reported compounds were performed.     

苦味酸含能离子盐的结构、生成热及爆炸性能理论研究

运用密度泛函理论DFT-B3LYP方法对5种苦味酸系列含能离子盐:苦味酸铵、苦味酸氨基脲、苦味酸碳酰肼、苦味酸氨基胍和苦味酸1,5-二氨基四唑进行了几何结构优化及红外振动分析,计算出生成热,并在此基础上,运用Kamlet-Jacobs方程估算出该类离子盐的爆速和爆压.     

DFT Predictions of Crystal Structure,Electronic Structure,Compressibility, and Elastic Properties of Hf–Al–C Carbides

To understand the potential for use of the Hf–Al–C ternary compounds, (HfC)_nAl₃C₂ (Hf₂Al₃C₄ and Hf₃Al₃C₅) and (HfC)_nAl₄C₃ (Hf₂Al₄C₅ and Hf₃Al₄C₆) were investigated using density functional theory, including crystal structure, electronic structure, compressibility, and elastic properties. The theoretical density of (HfC)_nAl₃C₂ (4.10–4.16 g/cm³) is higher than that of (HfC)_nAl₄C₃ (3.92–3.98 g/cm³), due to the smaller number of lighter Al–C layers. With increasing numbers of Hf–C layers, the Hf–C and Al–C bond lengths remain almost unchanged. In none of the compounds is there a gap around the Fermi energy (E_f), which implies they are metal‐like conductors. With increasing pressure, there is greater shrinkage along the c axis than the a axis. The bond stiffness increases with increasing pressure. In general, (HfC)_nAl₃C₂ has higher elastic stiffness than (HfC)_nAl₄C₃, with the moduli increasing with the number of Hf–C layers. The Hf–Al–C compounds as well as the brittle Zr–Al–C compounds all have low shear moduli/bulk moduli ratio (G/B) from 0.71 to 0.78, suggesting that the G/B ratio is not always a suitable measure of ductility.     

N,N-二(4-甲基苯基)-4-[2-(4-甲基苯基)乙烯基]苯胺的合成及光电导性能研究

以苯胺和对甲基溴苄为原料,经过Ullmann、甲酰化和Wittig3步反应,最终合成了N,N 二(4 甲基苯基) 4 [2 (4 甲基苯基)乙烯基]苯胺(Ⅲ),并且通过IR、1HNMR和MS进行了结构鉴定。以目标化合物为电荷传输材料,以酞菁氧钛为电荷产生材料复配制备的光电导样片性能参数为:充电电压1000V时,表面电位可达到935V,残余电位为60V,暗衰率为11 1V/s,光敏度为1 0(lx·s)-1,该数据表明目标化合物具有优良的电荷传输性能。     

ATO的DFT研究、热力学性质及绝热至爆时间

用DFT法在B3LYP/6-311G**水平上对作为结构单元的4-氨基-1,2,4-三唑-5-酮(ATO)进行了理论研究,评述了它的布居分析及稳定性.运用Micro-DSCⅢ微热量仪对ATO的比热容进行了测定,拟合得到其比热容与温度的关系式为Cp＝1.482 915-6.209 699×10-3T+1.699 017×10-5T2 (J·g-1·K-1) 和298.15 K时标准摩尔热容114.18 J·mol-1·K-1.根据热容与热力学函数关系, 计算得到了ATO以298.15 K为基准在283～353K 温区的焓、熵和吉布斯自由能.根据热容关系式及其热分解参数估算其绝热至爆时间为408.05 s.     

New Unsymmetrically Benzene-Fused Bis (Tetrathiafulvalene): Synthesis,Characterization, Electrochemical Properties and Electrical Conductivity of Their Materials

The synthesis of new unsymmetrically benzene-fused bis (tetrathiafulvalene) has been carried out by a cross-coupling reaction of the respective 4,5-dialkyl-1,3-dithiole- 2-selenone 6–9 with 2-(4-(p-nitrophenyl)-1,3-dithiole-2-ylidene)-1,3,5,7-tetrathia-s-indacene- 6-one 5 prepared by olefination of 4-(p-nitrophenyl)-1,3-dithiole-2-selenone 3 and 1,3,5,7-tetrathia-s-indacene-2,6-dione 4. The conversion of the nitro moiety 10a–d to amino 11a–d then dibenzylamine 12a–d groups respectively used reduction and alkylation methods. The electron donor ability of these new compounds has been measured by cyclic voltammetry (CV) technique. Charge transfer complexes with tetracyanoquino-dimethane (TCNQ) were prepared by chemical redox reactions. The complexes have been proven to give conducting materials.     

Thermosetting Polyetherimides: The Influence of Reactive Endgroup Type and Oligomer Molecular Weight on Synthesis,Network Formation,Adhesion Strength and Thermal Properties

The influence of the reactive endgroup on the synthesis, cure behavior and network properties of thermosetting polyetherimides was investigated. Reactive phenylethynyl, ethynyl and maleimide terminated etherimide oligomers were prepared and characterized. Optimal reaction conditions were established to produce fully endcapped oligomers with imidized structures and controlled molecular weight. The phenylethynyl and ethynyl endcapped systems were synthesized by ester-acid methods. The maleimide endcapped system utilized an amic-acid route. Phenylethynyl endcapped oligomers had good processibility and were thermally cured at high temperatures (350–380°C). The networks exhibited good thermal and hydrolytic stability and good adhesion strength, and are candidates for “primary'' bonding adhesives. In contrast, more reactive ethynyl and maleimide endcapped systems were prepared as “secondary'' bonding materials, which could be cured at temperatures lower than that of the T _g of the primary structure. Lap shear test results obtained from NMP-cast/methanol-extracted scrim-cloth-supported precursors confirmed that good adhesion to titanium at both room temperature and at 177°C was achieved when cured at 250°C-280°C. High glass transition temperatures and good thermal stability were achieved as determined by thermal analysis (DSC, TGA and DMA). Solvent extraction measurements confirmed that very high gel fractions were obtained, which is consistent with good chemical resistance.

The influence of molecular weight between crosslinks (Mc) on thermal and mechanical behavior was also investigated for 2,3,5,7 and 10k initial M _n values. Lower molecular weight oligomers exhibited lower T _g and cure temperatures, but higher cured network crosslink densities afforded higher T _g and higher gel fractions, but with reduced toughness.