2,4,6-三甲基-1,3,5-苯三甲醛的合成与表征

以均三甲苯为初始原料,经氯甲基化、改进的Sommelet反应两步合成了目标产物2,4,6-三甲基-1,3,5-苯三甲醛。利用1H NMR、13C NMR等手段对各步所得产物的结构进行了表征,分析数据证实目标产物为2,4,6-三甲基-1,3,5-苯三甲醛。以均三甲苯计,两步反应的总收率为77.7%。     

Nondestructive room-temperature adsorption of 2,4,6-tri(2'-thienyl)-1,3,5-triazine on a Si-B interface: high-resolution STM imaging and molecular modeling

Organic nanostructures on semiconductors are currently investigated but the surfaces are known to interact strongly with molecules. To reduce the molecule-surface interaction, we used the Si(111)-B square root 3 x square root 3R30 degrees . Deposition of isolated 2,4,6-tri(2'-thienyl)-1,3,5-triazine, was achieved at room temperature without modification of their pi skeleton. This fascinating arrangement, observed by STM, has been validated by full density functional theory computations onto the entire system. The theoretical results give a clear explanation for the specific adsorption sites of molecules on the substrate.     

Theoretical modelling of encapsulation of the Altretamine drug into BN(9,9-5) and AlN(9,9-5) nano rings: a DFT study

The aim of this paper is a better comprehension of the encapsulation and interaction an anticancer drug Altretamine into BN nano ring [BNNR(9,9-5)] and AlN nano ring [AlNNR(9,9-5)]. The electronic and adsorption properties of the molecule Altretamine over the BNNR and AlNNR were theoretically studied in the solvent phase at the B3LYP/6-31G* level of theory for the first time. With the non-bonded interaction of Altretamine, the electronic properties of the BN and AlN nano-cages can be significantly changed. The electronic spectra of the Altretamine drug, complex BNNR/Altretamine and AlNNR/Altretamine in solvent water were calculated by Time Dependent Density Functional Theory (TD-DFT) for the investigation of adsorption effect. According to the natural bond orbital (NBO) results, the molecule Altretamine, BNNR and AlNNR play as both electron donor and acceptor at the complexes BNNR/Altretamine and AlNNR/Altretamine. On the other hand, the charge transfer is occurred between the bonding, antibonding or nonbonding orbitals in the molecule drug, BNNR and AlNNR. As a consequence, BNNR(9,9-5) and AlNNR(9,9-5) can be considered as a drug delivery system for the transportation of Altretamine as anticancer drug within the biological systems.     

密度泛函理论研究簇合物(HFGaN3)n (n=1-6)：尺寸效应

用密度泛函理论DFT方法,计算研究不对称簇合物(HFGaN3)n (n=1-6)的几何构型、稳定性、IR谱和热力学性质。结果表明,簇合物(HFGaN3)n (n=2-6)的优化构型拥有一个Ga和α−N原子交替的2n元环状结构。通过计算研究(HFGaN3)n (n=1-6)的平均结合能、二阶能量差分和能隙与团簇尺寸关系,发现后两者表现出明显的“奇－偶”振荡现象。对计算获得的IR谱进行归属,获得四个特征区。讨论了团簇尺寸和温度对(HFGaN3)n (n=1-6)热力学函数的影响。由焓变和吉布斯自由能可知,200-800 K温度范围内由单体形成稳定的多聚体(HFGaN3)n (n=2-6)在热力学上有利。     

密度泛函理论研究簇合物(HFGaN_3)_n(n=1-6):尺寸效应

用密度泛函理论DFT方法,计算研究不对称簇合物(HFGaN_3)_n(n=1-6)的几何构型、稳定性、IR谱和热力学性质.结果表明,簇合物(HFGaN_3)_n(n=2-6)的优化构型拥有一个Ga和α-N原子交替的2n元环状结构.通过计算研究(HFGaN_3)_n(n=1-6)的平均结合能、二阶能量差分和能隙与团簇尺寸关系,发现后两者表现出明显的"奇—偶"振荡现象.对计算获得的IR谱进行归属,获得四个特征区.讨论了团簇尺寸和温度对(HFGaN_3)_n(n=1-6)热力学函数的影响.由焓变和吉布斯自由能可知,200-800K温度范围内由单体形成稳定的多聚体(HFGaN_3)_n(n=2-6)在热力学上有利.     

Sulfur adsorption on Fe(1 1 0): a DFT study

The adsorption of atomic S on the Fe(1 1 0) surface is examined using density functional theory (DFT). Three different adsorption sites are considered, including the atop, hollow and bridge sites and the S is adsorbed at a quarter monolayer coverage in a p(2 × 2) arrangement. The hollow site is found to be the most stable, followed by the bridge and atop sites. At all three sites, S adsorption results in relatively minor surface reconstruction, with the most significant being that for the hollow site, with lateral displacements of 0.09 Å. Comparisons between S-adsorbed and pure Fe surfaces revealed reductions in the magnetic moments of surface-layer Fe atoms in the vicinity of the S. At the hollow site, the presence of S causes an increase in the surface Fe d-orbital density of states between 4 and 5 eV. However, S adsorption has no significant effect on the structure and magnetic properties of the lower substrate layers.     

DFT study of isocyanate chemisorption on Cu(100): Correlation between substrate–adsorbate charge transfer and intermolecular interactions

The adsorption of isocyanate (? NCO) species on Cu(100) was studied using the density functional theory (DFT) and the periodic slab model. The calculations indicate that at low and intermediate coverages NCO adsorbs preferentially on bridge and hollow sites. Work function and dipole moment changes show a significant negative charge transfer from Cu to NCO. The resulting charged NCO species interact repulsively among themselves being these dipole–dipole interactions particularly intensive when they are adsorbed in adjacent sites. Consequently, isocyanates tend to be separated from each other generating the vacant sites required for the dissociation to N and CO. This condition for NCO dissociation has been suggested in the past from experimental observations. A comparison was also performed with the NCO adsorption on Pd(100). In particular, the calculated minimal energy barrier for NCO dissociation was found to be higher on Cu(100) than on Pd(100) in accord with the well known higher NCO stability on Cu(100).     

Synthesis,spectroscopic properties and DFT study of (E)-1-[(3-(trifluoromethyl)phenylimino)methyl]naphthalen-2-olate

The Schiff base (E)-1-[(3-(trifluoromethyl)phenylimino)methyl]naphthalen-2-olate was synthesized from the reaction of 2-hydroxy-1-naphthaldehyde with 3-trifluoromethylaniline. The title compound has been characterized by FT-IR, UV-vis and X-ray single-crystal techniques. The present X-ray investigation shows that the compound exists in the zwitterionic form. Molecular geometry of the compound in the ground state have been calculated using the density functional method (DFT) with 6-31G(d,p) basis set and compared with the experimental data. The calculated results show that the optimized geometry can well reproduce the crystal structural parameters. By using TD-DFT method electronic absorption spectra of the compound have been predicted and a good agreement with the TD-DFT method and experimental one is determined. In addition DFT calculations of the compound, molecular electrostatic potential (MEP), frontier molecular orbital analysis (HOMO-LUMO) and non-linear optical (NLO) properties were performed at B3LYP/6-31G(d,p).     

Effect of S adsorption on magnetic Co(0001) surface: a DFT study

Extended density functional theory calculations with the spin interpolation formula of Vosko, Wilk, and Nusair (VWN) are employed to study the effect of atomic S adsorption on Co(0001) surface. Besides the site preference for atom S in fcc-hollow site and adsorption geometry structures are in good agreement with experiments and previous calculations, some differences are also reported for the geometry of S in hcp-hollow site. Moreover, vibrational frequency, magnetic moments and electronic structure analysis are presented in more detail.     

Transport mechanisms in tris(8-hydroxyquinoline)aluminium (Alq3) electronic layers: a study by photodipolar absorption

This paper describes the role of traps in the electronic conductivity of tris(8-hydroxyquinoline)aluminium (Alq3) in a conventional sandwich structure with indium tin oxide and aluminium electrodes. New results obtained by photodipolar absorption techniques and impedance spectroscopy are presented. The former method acts as a probe to highlight the role of traps. It is shown that optical pumping of electrons to trap levels gives a clear increase in dielectric absorption due to the reorientation of dipoles associated with trapped charges. The trap depth is estimated to be around E _t?=?0.19?eV, a value in good agreement with theoretical calculations and thermoluminescence measurements. The latter method permits a representation of the sample in terms of a circuit composed of a parallel capacitor (C _p) and resistor (R _p) both in series with a resistor R _s?≈?50?Ω located on the anode side. A logarithmic plot of R _p as a function of the dc bias voltage gives a linear law that is recognized, for the first time, to be a consequence of a trapped charge limited (TCL) current. The linearity can be improved by the introduction of a field-dependent mobility.     

Cobalt-59 NMR and X-ray diffraction studies of hydrated and dehydrated (+/-)-tris(ethylenediamine) cobalt(III) chloride

Cobalt-59 NMR experiments have been carried out on single-crystal and polycrystalline (powder) samples of (+/-)-tris(ethylenediamine)cobalt(III) chloride trihydrate, (+/-)-[Co(en)(3)]Cl(3) x 3H(2)O, and of its dehydrate. In addition, the X-ray crystal structure of the dehydrated sample has been determined. X-ray diffraction measurements confirm a long-held assumption that dehydration has only minor effects on the structure of the [Co(en)(3)](3+) cation. Nevertheless, these small differences have a detectable effect on the 59Co nuclear magnetic resonance properties of these compounds; in particular, the nuclear quadrupole coupling constant, C(Q). Straightforward identification of the c-axis for large single crystals of (+/-)-[Co(en)(3)]Cl(3).3H(2)O and of its dehydrate allowed us to obtain single-crystal 59 Co NMR data by orienting the crystals in an MAS rotor. Data collected on single crystals and polycrystalline samples indicate that C(Q)=-3.05+/-0.05 and -2.80+/-0.05 MHz for the hydrated and dehydrated samples, respectively; the signs have been assigned on the basis of a point charge model. The chemical shift tensor principal components were also determined: for the hydrated sample, delta(perpendicular)=7281+/-2 ppm, delta(parallel)=7004+/-4 ppm and delta(iso)=7189 ppm; for the dehydrated sample, delta(perpendicular)=7288+/-2 ppm, delta(parallel)=7008+/-4 ppm and delta(iso)=7195 ppm. The electric field gradient and chemical shift tensors are axially symmetric, as required by crystal symmetry.     

Silicon carbide nanotubes (SiCNTs) serving for catalytic decomposition of toxic diazomethane (DAZM) gas: a DFT study

In the present study, the adsorption and decomposition of diazomethane (DAZM) on the surface of (6,0) zigzag silicon carbide nanotube (SiCNT) are investigated using density functional theory calculations. The geometry structures of the three stable configurations, adsorption energies and electronic properties of DAZM adsorption on the surface of SiCNT are investigated. It was found that the DAZM molecule is decomposed over the surface of (6,0) SiCNT with activation energy (E_act) of 0.523 eV. The curvature effect on the adsorption energies of the DAZM molecule is also considered by studying (5,0) and (7,0) SiCNTs. The results display that DAZM adsorption over smaller diameter of SiCNT is thermodynamically more favourable than larger one.     

The effect of substituted moiety on the optoelectronic and photophysical properties of tris (phenylbenzimidazolinato) Ir (III) carbene complexes and the OLED performance: a theoretical study

Density functional theory (DFT) and time-dependent density functional theory (TDDFT) are used to analyse theoretically the optoelectronic, photophysical properties and organic light-emitting diode performance of a series of fac–mer blue-emitting Iridium (III) carbene complexes. Swain–Lupton constant is used to discuss the substituents effect. 5d-orbital splitting and d–d* transitions are calculated to assess the efficiency of the studied complexes. The reorganisation energies (λ), transfer integrals, mobilities, radiative decay rate (k_r), and triplet exciton generation fraction (χ_T) are also calculated. Due to the higher χ_T of these complexes, the formation of triplet exciton will be more and it will cause a faster intersystem crossing. Two host materials are proposed and host–guest match (Dexter–Förster energy) is also discussed. We hope that this unified work will surely help to design new blue-emitting phosphorescent materials in future.     

Sulphur overlayers on Ir(100) and its effect on the adsorption of CO: a DFT study

Ordered sulphur overlayers adsorbed on Ir(100) surface are studied with differentcoverage ranging from 0.11 to 1.0 ML. Calculations indicate that atomic S adsorbsfavourably in hollow sites, forming strong covalent bonds with the substrate surface andthe adsorption energy is nearly unchanged at lower coverages(θ _S ≤ 0.50 ML). In good agreement withexperimental observations, the p(2 × 2)-S and c(2 × 2)-Sare predicted to be the most stable overlayers. The obtained surface electronic structuremodifications induced by sulphur adsorption are coverage-dependent and the results are inaccordance with the rectangular band and the Hammer-Nørskov models. Moreover, the effectof sulphur on the adsorption of CO is discussed in the p(2 × 2)?(S + CO)overlayer on Ir(100).     

取代基对2-(2-羟基苯基)苯并噻唑分子内氢键及质子转移的影响:密度泛函理论研究

运用密度泛函(DFT)和含时密度泛函(TD DFT)理论方法研究了在2-(2-羟基苯基)苯并噻唑(HBT)苯环羟基的邻位或对位分别引入羟基和醛基后的衍生物分子内质子转移过程,考察了取代基的电子效应及取代位置对分子内氢键和质子转移反应的影响,模拟计算了各分子的IR振动光谱和电子光谱.研究发现,HBT及其衍生物分子可以形成分子内氢键,且激发态时氢键增强.基态时以醇式构型稳定存在,激发态时酮式结构为优势构象.分子的最大吸收峰和发射峰主要源于电子从前线分子轨道HOMO到LUMO之间的跃迁.基态分子内质子转移需要越过较高的能垒因而难以发生,而激发态时只需越过较低能垒就很容易发生激发态分子内质子转移.取代基的电子效应和取代位置对HBT分子氢键强度、互变异构体的相对稳定性、电子光谱及质子转移反应的能垒均有一定影响.     

Ionic and radical adsorption on the Au(hkl) surfaces: A DFT study

Adsorption of several ionic and non-ionic species (OH^?, O, O^?, O^2?, H, H⁺ and H^?) on the low-index Miller Au(hkl) surfaces has been investigated by means of density functional theory based methods. The stability order for adsorptions on the three surfaces decreases with the increasing of the coordination number of the outermost gold atoms in each surface, i.e., Au(110) > Au(100) > Au(111), which is in agreement with the experimental evidences. The detailed COOPs analysis of the various adsorption sites for all adsorbates in the surface with the most stable adsorption(s), Au(110), evidenced that adsorption in the gold surfaces may be a function of particle size and charge and substantiates the variability in the order of preferences sites for the adsorption of the different species found in these low-index Miller Au(hkl) surfaces. This variability increases with the increasing of the stability of the adsorptions on the gold surfaces, i.e., the Au(110) presents more variability in the order of preferences sites for the adsorption of different species.     

DFT and Monte Carlo study of the W(001) surface reconstruction

The driving force for the W(001) surface reconstruction and electronic structures of pristine and H-covered W(001) surfaces are studied by means of relativistic DFT calculations. The spin-orbit coupling leads to the splitting of the bands. Adsorbed physical monolayer of hydrogen due to forming adsorption bonds stabilizes the (1 × 1) structure of the H/W(001) surface. The performed calculations have not revealed any substantial nesting of Fermi surface, so do not support the Peierls-like charge-density-wave mechanism of the surface reconstruction. The total energy of the (√2 × √2)R45° W(001) surface structure is found to be lower, by 0.14 eV per atom, than for the (1 × 1 W(001). The dependence of the relative intensity of the characteristic LEED reflection on temperature, obtained with the help of Monte Carlo simulations using the interaction energies estimated from DFT calculations, is in good agreement with available experimental data, thus supporting the concept of the order-disorder type of the transition between the low-temperature ((√2 × √2)R45° and room-temperature (1 × 1) surface structures of W(001).