Second-order Nonlinear Optical Properties of a Series of Azulene Derivatives

The first hyperpolarizabilities of a series of novel azulenic-barbituric acid chromophores have been studied by using 12 excitation wavelengths, ranging from 900 to 1907 nm. The dispersion relation of the first hyperpolarizabilities of chromophores holds the same tendency as the experimental results. In addition, the static first hyperpolarizability β0 of molecules was calculated by means of the Sum-Over-States (SOS) expression and the two-level formula respectively. The results show that these molecules possess large static first hyperpolarizabilities and the, β0 value increases as the donor or acceptor strength enhances; the distorted degree of molecules has also an important influence on the β0 value.     

Theoretical Studies on the First Hyperpolarizabilities of One-dimensional Donor-bridge-acceptor Chromophores and New Applications of BLA in Determining Molecular First Hyperpolarizabilities

We present a quantum-chemical analysis of the relationship between the bond length alteration （BLA） and the static first hyperpolarizability of a series of one-dimensional （1D） chromophores with donor-bridge-acceptor （D-B-A） structures. The calculated results show that the parameter BLA can be considered as an indicator to evaluate the molecular first hyper- polarizability. Along the direction of molecular ground-state dipole moments, the evolutions of BLA can be classified into three categories： the first is a non-monotonic line, which represents most chromophores; the second is monotonic increasing; and the third, contrarily, is monotonic decreasing. On the whole, the first hyperpolarizabilities of these studied chromophores are the monotonic functions of BLA along the direction of dipole moments. Therefore, the first hyperpolarizability of these 1D chromophores can be preliminarily evaluated in terms of the development of BLA without a rigorous computation. In other words, one can roughly estimate the relative magnitude of the first hyperpolarizability according to the optimized geometry.     

Correlations between photoelectron and phosphorescence spectra of polycyclic hydrocarbons

Comparison of the first IP's obtained from the photoelectron spectra of polycyclic hydrocarbons with the phosphorescence bands and the p-, α- and β-bands in the absorption spectra shows that only the first IP's, the first p-bands and the first phosphorescence bands are related to each other. The first triplet level T can be calculated from the difference IP₁ ? E_t = T, where E_t is the energy of the first phosphorescence band. The first triplet level T approaches 4.9 eV which is the vertical IP of graphite. Any deviation from this value is strictly related to the number of aromatic sextets in polycyclic systems. This applies to kata- and peri-condensed hydrocarbons. The asymmetric annellation effects reported in earlier work are again supported by the phosphorescence spectra. Contrary to the observations with the α-, β- and p-bands, there is considerable interaction with the third branch in linear benzologues of triphenylene (starphenes) when the t-bands are formed, and the T level shifts towards higher energies (lower eV values).     

Redox and photoisomerization switching of the second-order optical nonlinearity of a tetrathiafulvalene derivative of spiropyran across five states: a DFT study

Second-order nonlinear optical properties of a tetrathiafulvalene (TTF) derivative of spiropyran have been studied based on density functional theory (DFT) combined with the finite field (FF) calculations. Our DFT-FF calculations confirm a switching behavior of the static first hyperpolarizability caused by the redox and photochromic reaction. The photochromic reaction generates spiropyran-merocyanine conversion by reversible cleavage of the C-O bond, which is relative to the close- and open-ring forms 1-c and 1-o. The open-ring form 1-o displays the large static first hyperpolarizability relative to its close-ring form 1-c according to our DFT-FF calculations with three functionals. The electronic structure analysis and spin unrestricted calculations show that the redox processes significantly affect the geometrical structure of the TTF unit, and thus enhance the static first hyperpolarizabilities. The one-electron-oxidized species having good planar structure of the TTF unit are ~30 and ~200 times as large as that of the neutral compounds 1-c and 1-o, respectively. But the difference in the static first hyperpolarizability between one- and two-electron-oxidized states of spiropyran species is not substantial according to our DFT-FF calculations, and the spiropyran-merocyanine conversion of two-electron-oxidized species does not largely affect their static first hyperpolarizability. On the basis of the large change in the static first hyperpolarizability, our DFT-FF calculations support a five-state switching of the static first hyperpolarizability based on the redox and photoisomerization.     

Study of a Model for the Interaction Between Heavy Metals and Sediments of the Pisuerga River

Abstract

We have applied a competitive model, first proposed by Mouvet and Bourg, to explain the interaction between the heavy metals zinc, cadmium, lead, nickel and cobalt and bottom sediments from the Pisuerga River. Two sampling sites were chosen, the first located on an urban sewer and the second downstream from the polluting zone. The calculated constants for the first sediment were always lower than those found for the second one. The validity of the model is demonstrated by the existence of a correlation between the calculated constants and the first hydrolysis constants of the metals examined. All metal determinations were made by means of voltammetric techniques.     

Spectrophotometric Methods for the Determination of Acediasulfone in Mixture with Cinchocaine

Abstract

Derivative spectrophotometry techniques (ratio‐spectra first derivative and zero‐crossing first derivative) were described for simultaneous determination of acediasulfone and cinchocaine. Acediasulfone was also determined via the formation of a colored product as a result of its reaction with p‐dimethylaminobenzaldehyde. In the ratio‐spectra first derivative method, the measurements were taken at 310 and 233.9 nm for acediasulfone and cinchocaine, respectively. By the zero‐crossing first derivative method, lines of regression were taken at 318 and 233 nm for acediasulfone and cinchocaine, respectively. In the colorimetric method, absorbance measurements were obtained at 452 nm. Acediasulfone showed linearity over concentration ranges 2–14 µg/ml, 2–16 µg/ml, and 12–60 µg/ml for ratio‐spectra first derivative, zero‐crossing first derivative, and colorimetric methods, whereas cinchocaine showed linearity over concentration ranges 1–10 µg/ml and 2.28–16 µg/ml for ratio‐spectra first derivative and zero‐crossing first derivative techniques. The proposed methods proved to be specific and accurate for the analysis of the cited drugs in laboratory‐prepared mixtures and dosage form. The obtained results agree statistically with those obtained by reference methods.     

水环境对GC和AT碱基对质子转移的影响

采用B3LYP/DZP++的方法研究了第一水化层作用和连续化处理的水溶剂作用对鸟嘌呤-胞嘧啶(GC)碱基对和腺嘌呤-胸腺嘧啶(AT)碱基对质子转移反应的影响. GC和AT碱基对在连续化水溶剂作用下,均发生单质子转移(SPT1)和分步的双质子转移(DPT),而在第一水化层5 个水分子的作用下(GC·5H₂O,AT·5H₂O)或同时考虑第一水化层作用和连续化水溶剂作用(GC·5H₂O+PCM,AT·5H₂O+PCM)时,GC和AT碱基对的质子转移均只得到单质子转移反应(SPT1). 单质子转移过程中的活化能变化情况表明：第一水化层对GC和AT碱基对结构和质子转移影响较大,水环境对碱基对的作用主要发生在第一水化层.     

Chelating alkoxy-N-heterocyclic carbene complexes of silver and copper

Incorporation of an alkoxide functional group into an N-heterocyclic carbene (NHC) ligand allows the synthesis of the first anionic NHC chelating ligands, which react to give the first neutral, molecular silver(I) alkoxide carbene complex, and a copper(I) derivative containing the first nonmacrocyclic, square planar Cu(I) centres.     

Effect of zeta potential on retention and drainage of secondary fibres

The experiments have been carried out in the laboratory to investigate the interactions among negatively charged fibres, fines and positively charged polymer particles on two different papermaking slurries of old corrugated containers (OCC) pulp and mixed office waste (MOW) paper pulp. The effects of different wet-end chemicals such as polyacrylamide, polyamide amine and polyethylene amine on fibre surface chemistry have been followed by electrokinetic measurements (zeta potential) of papermaking stock to control the retention and drainage and see how well they perform in the wet-end of the paper machine. The flocculation behaviour has been investigated by different procedures: dewatering test and measuring the first pass retention. Treatment of pulps with chemical additives resulted in substantial improvement of drainage with increase in first pass retention. For OCC pulp, the best results were obtained with 0.5% polyacrylamide improving the drainage by 82% with corresponding first pass retention of 87.5% against 81.8% for the control pulp. However, for MOW pulp, the best results were obtained with 0.3% polyethylene amine improving the drainage by 63% with corresponding first pass retention of 86.0% against 74.2% for the control pulp. The studies on zeta potential of secondary fibres revealed the dependence of first pass retention and drainage on zeta potential of pulps. As the zeta potential approaches zero, the conditions approach optimum for first pass retention and drainage. This way, zeta potential control can lead to environmental protection and competitiveness by using secondary fibres more extensively.     

Copper catalysis of 8-acetoxyquinoline hydrolysis

The hydrolysis of 8-acetoxyquinoline in dilute acid solution has been found to be subject to copper^II catalysis. The catalysed reaction is first order in 8-acetoxyquinoline (as the free base), first order in copper ion, and first order in hydroxide ion. It is proposed that a copper chelate is a reaction intermediate in the hydrolysis.     

Kinetic studies of complexation reactions of water-soluble hydrazones with nickel(II) and palladium(II) ions

The kinetics of complexation reactions of five water-soluble heterocyclic hydrazones with nickel(II) and palladium(II) ions have been investigated by stopped-flow spectrophotometry. Rates of complexations with nickel(II) and palladium(II) in the absence of chloride ion were found to be proportional to the first order of the ligand and metal ion concentrations and to the inverse first order of the hydrogen ion concentration except for the complexation of alpha-(2-benzimidazolyl)-alpha-(5-nitro-2-pyridyl)hydrazono-3-toluenesulfonic acid with palladium(II). Rates of complexation with palladium(II) in the presence of chloride ion were best described by a two-term expression, both terms being first order in the palladium ion and ligand concentrations and inverse first order in the hydrogen ion concentration. The first term has zero dependence of the chloride ion concentration, whereas the second is first order with respect to the chloride ion concentration. The rate constant for each complexation reaction was determined. The complexation of the hydrazones with nickel(II) was estimated to go according to an Eigen mechanism and that with palladium (II) according to the associative mechanism.     

Synthesis of indenes by the transition metal-mediated carboannulation of alkynes

The synthesis of highly substituted indenes has been achieved by three different transition metal-mediated methods. The first method involves the palladium-catalyzed carboannulation of internal alkynes. The second method utilizes a two-step approach, which involves first the palladium/copper-catalyzed cross-coupling of terminal alkynes with appropriately functionalized aryl halides, followed by copper-catalyzed intramolecular cyclization. The third method involves intermolecular palladium-catalyzed arylation of the arylalkynes formed in the first step of the second method.     

1,4-Addition of a Terminal Phosphinidene Complex to [5]Metacyclophane

Three novel aspects emerge for the reaction of [5]metacyclophane ( 1 ) with the (intermediate) phenylphosphinidene complex 2 to give the 7-phosphanorbornadiene 3 . It is the first 1,4-addition of a phosphinidene complex to an unsaturated system, the first addition of a phosphinidene complex to a benzene ring, and the first [4+1] cycloaddition to an aromatic compound.     

Ti-MWW催化氯丙烯环氧化反应动力学行为

以Ti-MWW分子筛为催化剂,以H2O2为氧化剂,系统研究了氯丙烯环氧化反应的动力学行为.结果表明,该反应速率与Ti-MWW分子筛的用量成正比,是1级反应.当H2O2浓度小于0.67 mol/L时,环氧化反应为1级反应;大于2 mol/L时,为0级反应.随着氯丙烯浓度的增加,环氧化反应级数从1级向0级转变;且只有当其浓...     

Kinetics of the Decarboxylation of Gallic Acid in Pyrogallol,Resorcinol and Catechol

Kinetic data are reported for the decarboxylation of gallic acid in pyrogallol, resorcinol and catechol. This is the first study of its kind in these solvents. The reaction is first order and non-stoichiometric.     

Naming elements after scientists: an account of a controversy

Over the last two hundred years, there have been many occasions where the name of a newly-discovered element has provoked controversy and dissent but in modern times, the naming of elements after scientists has proved to be particularly contentious. Here we recount the threads of this story, predominantly through discourses in the popular scientific journals, the first major discussion on naming an element after a scientist (Moseley); the first definitive naming after a scientist (Curie); and the first naming after a living scientist (Seaborg).     

The packing structure of side chains of liquid-crystalline side-chain polymers before and during heat treatment

Six varieties of liquid-crystalline side-chain polymers, poly (cholesteryl ω-(methacryloyloxy)alkanoates) (p-ChMO-n, n = 1,2,3,4,5,7, the carbon number of the alkyl chain), were studied by differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS). On and after the first cooling run from the isotropic state, these polymethacrylates gave the same smectic phase. However, on the first heating run for virgin samples, unique phenomena were observed, similar to those frequently observed on the first heating run for thermotropic liquidcrystalline polymers. The thermal properties of the first heating run for these six polymers showed different tendencies between pChMO-n (n-1-3) and pChMO-n (4-7). Although the DSC curve of pChMO-n (n = 4, 5 and 7) exhibited the melting and clearing points on the first heating run, the DSC curve of pChMO-n (n = 1,2 and 3) exhibited an exothermal peak between the glass transition and the clearing point on the first heating run. This difference, probably due to the difference in the spacer length of these polymers, was investigated quantitatively by small-angle X-ray scattering by which the micro-change of the packing structure of the side chains of the polymers was traced.     

Analysis of Adsorption Data of Graphitized Thermal Carbon Black with a DFT-Lattice Gas Theory

In this paper we analyzed the adsorption of gases and vapors on graphitised thermal carbon black by using a modified DFT-lattice theory, in which we assume that the behavior of the first layer in the adsorption film is different from those of second and higher layers. The effects of various parameters on the topology of the adsorption isotherm were first investigated, and the model was then applied in the analysis of adsorption data of numerous substances on carbon black. We have found that the first layer in the adsorption film behaves differently from the second and higher layers in such a way that the adsorbate-adsorbate interaction energy in the first layer is less than that of second and higher layers, and the same is observed for the partition function. Furthermore, the adsorbate-adsorbate and adsorbate-adsorbent interaction energies obtained from the fitting are consistently lower than the corresponding values obtained from the viscosity data and calculated from the Lorentz-Berthelot rule, respectively.     

Synthesis of functionalized benzannulated compounds

Functionalized indane and naphthalene derivatives have been prepared according to two routes involving a nickel-catalyzed electrochemical arylation of activated olefins as the key step. The first method is a cascade process including the intramolecular nucleophilic addition of the first formed enolate intermediate. In the second method the cascade reaction is prevented by in situ protonation of the enolate, and the cyclization is further conducted chemically. This is an overall more efficient method than the first one, based on the electrochemical process.