bluuebunny/crossref_metadata_2025 huggingface dataset:
σπ Scheme in Atom‐bond Electronegativity Equalization Method
Authors: Yang Zhong‐Zhi , Cong Yao , Zhao Dong‐Xia , Wang Chang‐Cheng , Bao Xin‐He
Published: May 2015

Although, as we know, the traditional ab initio quantum chemical methods can deal with molecules of medium size, it is still a tremendous task to treat very big organic and biological systems. So even today it is still valuable to develop some meaningful relatively simple methods, such as EEM or ABEEM, to see how well and to what extent those kinds of methods can be employed with a huge savings of time to study very large systems. This kind of effort, including what has been done in this paper, may continue for quite a long period, especially considering dynamic problems in the near future. We will develop an atom‐bond electronegativity equalization method plus σπ (ABEEM σπ) scheme on the basis of DFT, in which the structure of double bond is explicitly treated in the electronegativity equalization method. In this scheme, the effective electronegativity of a region can be expressed as one valence‐state electronegativity (χ*) term, one valence‐state hardness (η*) term, and some other contributing terms coming from other regions' charges in the molecule. By dealing with more than 200 molecules, the parameters χ*, η*, C, and D in the expression of electronegativity are determined through a regression and least‐squares optimization procedure, and their meaning is also discussed. As testing examples, the ABEEM σπ scheme is used to calculate the charge distributions of C18N3O3H27, C15NO2H21, and thyrotropin‐releasing hormone (TRH), and the results show good agreement with those obtained by the ab initio method. However, this scheme is far more time saving and computational‐source saving compared to the conventional ab initio method. All of this indicates that the ABEEM σπ scheme is a reasonable and potential tool for predicting the properties of very large organic and biological systems such as poly‐peptides and proteins, etc.
Preparation and Application of Cholesteryl‐Macrocyclic Polyether Liquid Crystals and Surfactants
Authors: Lee Juei‐Ling , Shen Ya‐Chi , Shih Jeng‐Shong
Published: May 2015

Macrocyclic polyethers containing a cholesteryl moiety, e.g., cholesteryl benzo‐15‐crown‐5 (C27H45OOC‐B15C5) and cholesteryl cryptand22 (C27H45OOC‐Cryptand22), were synthesized. The cholesteryl crown ether C27H45OOC‐B15C5 showed liquid crystal characteristics which were observed by polarizing microscopy. In contrast, the cholesteryl cryptand C27H45OOC‐Cryptand22 showed no liquid crystal characteristics. The doping effect of inorganic salts on the liquid crystal formation of cholesteryl benzo‐15‐crown‐5 was also investigated, revealing that the addition of salts resulted in narrower liquid crystal temperature ranges. Both cholesteryl cryptand C27H45OOC‐Cryptand22 and cholesteryl crown ether C27H45OOC‐B15C5 also exhibited the distinctive characteristics of surfactants in solutions. Fluorescence probe of pyrene and surface tension measurement were applied as sensitive tools to study the formation of the micelles and determine the critical micellar concentration (CMC) of the cholesteryl cryptand and crown ether surfactants. The salt effect on the CMC of the cholesteryl cryptand surfactant was also investigated and is discussed. Furthermore, the cholesteryl benzo‐15‐crown‐5 was successfully employed as a quite good phase transfer catalyst for the oxidation of alcohols, e.g., benzhydrol, with NaMnO4 as an oxidant. Effects of temperature, solvent and concentration of the crown ether catalyst on the oxidation of benzhydrol were also investigated.
Immobilization of a Monolayer of Bovine Serum Albumin on Gold Nanoparticles for Stereo‐specified Recognition of Dansyl‐norvaline
Authors: Liu Fu‐Ken , Wei Guor‐Tzo , Cheng Fu‐Chou
Published: May 2015

The assembly strategy to prepare a monolayer of bovine serum albumin on the surface of silica gel supported gold nanoparticles is described. The stereo‐specific recognition ability of this material was evaluated by enantioresolution of Dansyl‐norvaline. For enantiomeric separation, the influences of buffer concentration and the concentration of organic modifier on the separation performance were investigated. A better separation in terms of enantioresolution and peak shape was found with the phosphate concentration at 30 mM. Moreover, the peak shape and resolution can be improved by the addition of methanol solution. Enantioresolution of Dansyl‐norvaline was obtained from this material at optimized conditions. It appears that the immobilization of a monolayer of bovine serum albumin on gold nanoparticles as the chiral selector of Dansyl‐derivative amino acid is promising.
The Torsional Stability Around a Single Bond Analyzed by Extended Hückel Orbital Forces
Authors: Federico Eisner S. , Jorge Ricardo Letelier D.
Published: May 2015

A simple pencil and paper method to calculate the forces acting on individual atoms in a molecule, due to the electrons in the different populated molecular orbitals, has been developed within the Extended Hückel formalism. The method is applied to study the torsional stability around a single bond of some simple molecules. The results show good agreement with the experimental evidence of stable conformers.
Preparation and Characterization of Trimethylsilylpyridylacetylene Bridged, Dicobalt Carbonyl Complexes Containing Bis(diphenylphosphino)methylene or Bis(diphenylphosphino)ethylene Ligand
Authors: Hong Fung‐E , Chang Yu‐Chang , Chen Cheng‐Wei , Huang Yi‐Luen
Published: May 2015

Reaction of an alkyne‐bridged dicobalt complex, [Co2(CO)6(μ‐Me3SiC=Cpy)] 4, with bis(diphenylphosphino)methylene (DPPM) or bis(diphenylphosphino)ethylene (DPPE) in THF at 55 °C yielded a DPPM or DPPE doubly bridged dicobalt compound, [{μ‐P,P‐PPh2CH2PPh2}Co2(CO)4(μ‐Me3SiC=Cpy)] 5 or [{μ‐P,P‐PPh2CH2CH2PPh2}Co2(CO)4(μ‐Me3SiC≡Cpy)] 6. Compound 5 and 6 were characterized by spectroscopic means as well as X‐ray crystal structure determination.
Cyclic Voltammetric and Ac Impedance Behavior of TiO2 Electrodes under UV Illumination
Authors: Cui Xiaoli , Jiang Zhiyu
Published: May 2015

Electrochemical behavior of an ITO/TiO2 electrode both under ultraviolet (UV) illumination and in the dark was investigated using the methods of cyclic voltammetry and ac impedance spectroscopy. A new oxidative peak is observed at 0.15 V when the TiO2 electrode was illuminated by UV light for a certain time. The peak current and the anodic photocurrent increased with the increase of UV light intensity. It is assumed that the new peak belonging to the oxidation of Ti3+, which was formed on the electrode surface during the UV illumination. It is also found that the apparent resistance was decreased but the capacitance was increased when the TiO2 electrode was illuminated by UV light according to the measurement results of ac impedance. Based on the results in this paper, it was directly proved that Ti3+ was actually formed when the electrode was irradiated by UV light.
Ion and Adsorbing Colloid Flotation of Auramine
Authors: Lu Chung‐Shin , Chen Chiing‐Chang
Published: May 2015

Auramine, a cationic dye, was removed from synthetic wastewater by ion flotation of auramine‐sodium lauryl sulfate complex. Over 98% of auramine was removed from the solution in 15 min. A stoichiometric amount of surfactant (1 mol of surfactant to 1 mol of dye) was found to be most effective for auramine removal. The rate of separation and ultimate removal of auramine increased with increasing the rate of air flow and decreased with increasing concentration of NaNO3. Auramine was also removed by adsorbing colloid flotation technique using ferric hydroxide as the coagulant. Sodium lauryl sulfate was used as the collector, and over 95% of auramine was removed in 10 min. The separation efficiency decreased with increasing ionic strength of the solution. The deleterious effect of neutral salt was compensated somewhat with the aid of aluminum ions as the activator. Both ion flotation and adsorbing colloid flotation are promising approaches for the removal of cationic dye from wastewater.
Spectroscopic and Chromatographic Identification of Hydrocarbon Group Types in Pakistani Crude Oils
Authors: Ishaq M. , Ahmed Imtiaz , Saeed Khalid , Ismail M. , Bahader Ali
Published: May 2015

Two crude oil samples collected from Paniro and Tangri (Sindh) southern Pakistan. The distillate fractions of both crude oil samples were analysed by U.V‐visible spectrophotometer and column chromatography for hydrocarbon group types. It was found from the physico‐chemical study of these crude oils that Tangri crude oil contains mostly paraffinic contents while Paniro crude oil samples are rich in aromatics. It was concluded from all the experiments that Tangri crude oil is paraffinic in nature; while Paniro crude oil is naphthenic in nature, further it was observed that Tangri crude oil processing would be environmentally friendly compared to Paniro crude oil, because Paniro crude contains a high amount of polyaromatics.
Characterization of Zinc Ion Transport Via Dialysis Process
Authors: Madaeni S. S. , Godini H. R.
Published: May 2015

Treatment of metal ions' wastes is getting more interest due to the tight regulations for environmental protection. Dialysis, a membrane based process with the concentration difference as the driving force, may be used for separation of metal ions from wastewater.

In this study membranes with different pore sizes including Accurel, Celgard, GVHP, PM30 and PTHK membranes were employed to characterise the transport of zinc ion in various (0.01, 0.1, 0.5, 1, 5 and 10 w/v percent) initial feed concentrations.

The results show that low initial feed concentration causes less passage of ions through the membrane due to low driving force, i.e. concentration gradient across the membrane. This result is expected. However the effect of membrane pore size is somehow unexpected. It was found that the large pore size membranes provide less penetration of the metal ions through the membrane. This reproducible result has been explained based on the transport mechanism. Two types of mechanisms, i.e. extensive and intensive mechanisms, have been suggested for metal ion transport through different pore size membranes.
CeCl3/Sm Promoted Pinacolic Coupling of Aromatic Aldehydes and Ketones
Authors: Li Xue , Zhang Songlin , Zhang Xinying , Wang Xiaoyang
Published: May 2015

The pinacolic coupling of aromatic aldehydes and ketone was performed with cerium trichloride and samarium in THF at room temperature to afford the corresponding 1,2‐diols in good yields.
Diastereoselective Epoxidation of Camphor N‐Enoylpyrazolidinones
Authors: Fan Chai Ling , Reddy Gondi Sudershan , Chen Kwunmin
Published: May 2015

Reaction of camphor N‐enoylpyrazolidinones (1a‐j) with various oxidants, in particular UHP/TFAA afford chiral epoxides with a wide range of stereoselectivities (up to > 90% de).
Nitriles in Heterocyclic Synthesis: Reactivity of 2‐(Benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one towards α,β‐Unsaturated Nitriles
Authors: Sayed S. M.
Published: May 2015

The reaction of 2‐(benzothiazol‐2‐ylmethyl)‐1,3‐thiazol‐4(5H)‐one 1 with α,β‐cinnamonitrile derivatives 2a‐n have been reported.
Two Cerebrosides and One Acylglycosyl Sterol from Monochoria Vaginalis
Authors: Row Lie‐Ching , Chen Chiu‐Ming , Ho Jiau‐Ching
Published: May 2015

Three new compounds have been isolated from the whole plant of Monochoria vaginalis and characterized as: (2S,3R,4E,8E,2′R)‐1‐O‐(β‐D‐glucopyranosyl)‐N‐(2′‐hydroxyicosanoyl)‐4,8‐sphingadienine, (2S,3R,4E,8E,2′R)‐1‐O‐(β‐D‐glucopyranosyl)‐N‐(2′‐hydroxyoctadecanoyl)‐4,8‐sphingadienine and 7‐oxostigmasteryl‐3‐O‐(6′‐hexadecanoyl)‐β‐D‐glucopyranoside. Their structures were established by spectral and chemical evidence.
The Efficient Synthesis of the Optically Active β‐Hydroxyl‐γ‐Butyrolactone Derivatives
Authors: Wang Jin Xin , Li Ying , Zhang Chao Xin
Published: May 2015

The optically active β‐hydroxyl‐γ‐butyrolactones were synthesized from nonchiral starting material by employing reductive cleavage reaction, sharpless asymmetric epoxidation and dihydroxylation, and Lewis acid‐catalysed cyclization as key steps. This strategy can be used to prepare many chiral β‐hydroxyl‐γ‐butyrolactone analogues.
Study on the Color Reaction of Silver with 2‐(2‐Quinolylazo)‐5‐Dimethylaminoaniline and its Application
Authors: Hu Qiu‐Fen , Yang Guang‐Yu , Huang Zhang‐Jie , Yin Jia‐Yuan
Published: May 2015

A new chromogenic reagent, 2‐(2‐quinolylazo)‐5‐dimethylaminoaniline (QADMAA) was synthesized. A highly sensitive, selective and rapid method for the determination of silver based on the rapid reaction of silver(I) with QADMAA was developed. In the presence of pH = 6.5 sodium citrate‐sodium hydroxide buffer solution and sodium dodecyl sulfonate (SDS) medium, QADMAA reacts with silver to form a violet complex of a molar ratio 1:2 (silver to QADMAA). The molar absorptivity of the complex is 1.26 × 105 L. mol−1.cm−1 at 570 nm. Beer's law is obeyed in the range of 0.01–0.6 μg/mL. The relative standard deviation for eleven replicate samples of 0.2 μg/mL silver is 1.76%. This method was applied to the determination of silver in water with good results.
Synthesis of Some New Heterocycles of Pharmaceutical Interest: Pyridinyl and Isoxazolyl Quinoxaline Derivatives
Authors: Moustafa Osama S.
Published: May 2015

3‐(p‐Acetyl‐anilinomethyl)quinoxalin‐2(1H)‐one (3) was prepared by the reaction of 3‐bromomethyl‐quinoxalin‐2(1H)‐one (1) with p‐aminoacetophenone (2) in pyridine. Reaction of p‐acetylcompound (3) with aromatic aldehydes yield the corresponding chalcones (4a‐c). Condensation of latter chalcones with malononitrile afforded cyanopyridines (5a‐c). Also, the reaction of chalcones (4a‐c) with hydroxylamine hydrochloride furnished isoxazoles (6a‐c). The reaction of bromo compound (1) with p‐aminobenzophenone yield (8) which was condenced with hydrazine hydrate to get the corresponding hydrazone derivatives (9). Some of the synthesized compounds have been screened for their antimicrobial activity against various strains of bacteria and fungi.
The Study on Synthesis of Some New 1,2,3‐Triazolylurea and Carbonyl Amide Derivatives
Authors: Dong Heng‐Shan , Liu Shi‐Qiang
Published: May 2015

The study on syntheses of some N‐substituted‐N′‐[5‐methyl‐1‐(4‐chlorophenyl)‐1,2,3‐triazol‐4‐yl]‐urea 6a‐e and N‐substituted‐[5‐methyl‐1‐(4‐chlorophenyl)‐1,2,3‐triazol‐4‐yl]carbonyl amide 6f‐l derivatives were reported in this paper. The yielded products 6a‐l were confirmed by elemental analyses, NMR, MS and IR spectra.
Factors Influence Complexing Selectivity of Lariat Crown Ethers Toward Alkali Metal Ions in Electrospray Ionization Mass Spectrometry
Authors: Cheng Sheng‐Fan , Hung Huan‐Yi , Liu Lilian Kao
Published: May 2015

The selectivity of eight lariat crown ethers in the sym‐dibenzo‐16‐crown‐5 series toward alkali metal ions was studied with electrospray ionization mass spectrometry under different conditions. With the exception of 2g, which is equally selective toward Na+ and Li+, all other lariat crown ethers show the best selectivity toward Li+ in methanol. Factors that influence the selectivity include the water content, counterions, nature of the side arms, and the externally added cations. Iodide gives the best Na+ selectivity with RI > RBr > RCl. Increased water content profoundly increases the Na+ selectivity when the side arm is hydrophilic and the steric hindrance is small. Externally added cations (Cs+ and/or Rb+) enhance the Na+ selectivity by exchanging the smaller Li+ from the cavity.
Probing the Effects of Reagent Gas Pressure and Ion Source Temperature for Dimethyl Ether Chemical Ionization of Tricyclic Antidepressants in an External Source Ion Trap Mass Spectrometer
Authors: Wu Hui‐Fen , Lin Pei‐Yi
Published: May 2015

This study examines the reagent gas pressure and ion source temperature dependence for dimethyl ether chemical ionization (DME CI) mass spectra recorded with an external source ion trap mass spectrometer (ITMS). Information for better controls of the reagent gas pressure in order to obtain fair CI spectra is provided. The origin of M+• ions observed in DME CIMS is discussed in detail. Furthermore, the ion source temperature effect on the DME CI is also investigated.
Synthesis, Reactivity, and Crystal Structure of the η2‐Thiocarbamoyl Palladium Complex [Pd(PPh3)2(η2‐SCNMe2)][PF6]
Authors: Yih Kuang‐Hway , Lee Gene‐Hsiang , Wang Yu
Published: May 2015

The η1‐thiocarbamoyl palladium complexes [Pd(PPh3)(η1‐SCNMe2)(η2‐S2R)] (R = P(OEt)2, 2; CNEt2, 3) and trans‐[Pd(PPh3)2(η1‐SCNMe2)(η1‐Spy)], 4, (pyS: pyridine‐2‐thionate) are prepared by reacting the η2‐thiocarbamoyl palladium complex [Pd(PPh3)2(η2‐SCNMe2)][PF6], 1 with (EtO)2PS2NH4, Et2NCS2Na, and pySK in methanol at room temperature, respectively. Treatment of 1 with dppm (dppm: bis(diphenylphosphino)methane) in dichloromethane at room temperature gives complex [Pd(PPh3)(η1‐SCNMe2)(η2‐dppm)] [PF6], 5. All of the complexes are identified by spectroscopic methods and complex 1 is determined by single‐crystal X‐ray diffraction.
Mixed Cationic‐nonionic Surfactants and pH Adjustment Route to Synthesize High‐quality MCM‐48
Authors: Zhai Shang‐Ru , Gong Yan‐Jun , Zhang Ye , Deng Feng , Luo Qing , Wu Dong , Sun Yu‐Han
Published: May 2015

Using the mixture of cetyltrimethylammonium bromide (CTAB) and p‐Octyl polyethylene glycol phenyl ether (OP‐10) as templates, siliceous MCM‐48 materials can be synthesized with low molar ratio of CTAB to silica (0.139:1) and low concentration of mixed surfactants (ca.5%) and within a wide range of OP‐10/CTAB ratio (0.08˜0.25). The materials were characterized by X‐ray powder diffraction, N2 adsorption/desorption isotherm, TEM, TG‐DSC and 29Si MAS NMR. Measurements indicated that the use of mixed surfactants allowed better condensation and higher ordering of the cubic mesostructure; at the same time, some properties of these materials were sensitive to the OP‐10/CTAB ratio. It was also found that the reduced pH of the gel which had been crystallized for a certain time gave a highly reproducible synthesis with a high silica yield (about 95%). Furthermore, the reaction mechanism of the synthesis is discussed in detail.
Thermodynamic‐Dependent Size‐Selection of ZnSe Nanoparticles in Amphiphilic Triblock Copolymer Systems
Authors: Yang Chung‐Sung , Ku Kuo‐Lung
Published: May 2015

ZnSe colloidal nanoparticles prepared by the air‐insensitive starting reagents, zinc chloride and selenium powder, have been size‐selected in the Pluronic amphiphilic triblock copolymer [(EO)x(PO)y(EO)x] systems. The size‐selection mechanism between the ZnSe nanoparticles and the triblock copolymers systems is a thermodynamic‐dependent effect. We observe that nanoparticles with special volume (Vs) are trapped first by the triblock copolymers due to the faster entropic depletion interaction arising from the addition of surfactant‐template (micelles) to colloidal nanoparticles. On the other hand, nanoparticles with sizes larger or smaller than Vs will not interact with the surfactant‐templates. They either precipitate quickly by gravity (larger than Vs) or still retain their thermal motion in the aqueous phase (smaller than Vs) when Vs nanoparticles are caught by the surfactant‐templates.
Spectrofluorimetric Determination of Trace Amounts of Copper
Authors: Liu Jian‐Ning , Zhang Bing , Wu Bo‐Wan , Yu Xin‐Qiao
Published: May 2015

A fluorescent reagent, 2,4‐dihydroxyacetophenone‐4‐hydroxybenzoylhydrazone (2,4‐DH‐AP‐4‐H‐BH) was studied on its fluorescent reaction with copper using the spectrofluorimetric method. In a water‐ethanol solution at pH 12.0, a chelating reaction occurs between copper and 2,4‐DH‐AP‐4‐H‐BH. The molar ratio of copper to the reagent is 1:2. This reaction causes characteristic changes of spectra of fluorescence with excitation and emission maxima at 342.4 and 419.2 nm, respectively. This method can quantitate the amount of copper in the reaction. It detects as little as 0.2 ppb of copper with a linear range between 0.2 to 120 ppb. It has been successfully applied to detect copper in mineral water, tea, and hair.
Synthesis of 3‐[4‐Acyl‐2‐(1‐methoxy‐1‐methylethyl)morpholin‐3‐yl]‐benzonitriles as Novel Potassium Channel Openers
Authors: Lin Mei‐Shan , Hsin Ling‐Wei , Cheng Chen‐Yu
Published: May 2015

Potassium channel openers (KCO's) have been demonstrated to possess potent relaxant‐activity on smooth muscle. Tissue‐selective KCO's may find use in the treatment of a variety of diseases, such as hypertension, asthma, and urinary incontinence. We have previously reported a series of 1,9‐dioxa‐4‐aza‐phenanthrene‐6‐carbonitriles, including compounds 2 & 3, as bladder‐selective KCO's. As a continuation of our efforts, we have designed 3‐[4‐acyl‐2‐(1‐methoxy‐1‐methylethyl)morpholin‐3‐yl]‐benzonitriles as ring‐opened analogs of compounds 2 & 3. In this report, we describe the efficient construction of the novel 2,3‐disubstituted morpholine structure, as represented by the synthesis of compounds 4‐7. Compounds 4‐7 showed potent and selective relaxant‐activity on rat bladder detrusor strip preparation. In this series, the most potent derivatives are Boc‐substituted analogs 4 & 6 (IC50 = 3.9 and 2.9 μM, respectively).
Octasilsesquioxane Chemistry II. Hydrosilylation Reaction of Octa(hydrido)silsesquioxane with Unsaturated Substrates and Product Properties
Authors: Liu Ling‐Kang , Dare Enock O.
Published: May 2015

The hydrosilylation reaction of octa(hydrido)silsesquioxane with ω‐halo‐1‐alkenes and other unsaturated substrates allows attachment of 8 long‐chain functionalized alkyls on the cubic Si8O12 skeleton. Pt/C and H2PtCl6 have been adopted as the catalysts, the yields being 74–98% for compounds 2–9. For terminal alkenes, the hydrosilylation follows the anti‐Markonikov's rule. The morphological state of 2–9 ranges from viscous liquid to crystalline materials. The pyrolysis results indicate that 7, a material of hard spherical core and soft flexible shell, may likely act as nanometer‐size ball bearings up to more than 400 °C. The X‐ray structure of 9 reveals that the molecule is required to possess a center of symmetry crystallographically. The linear arms on 9, except for two of them, are virtually all‐trans in conformation, not counting the ω‐C‐Cl bond.
Flavone Glycosides from Strobilanthes Formosanus
Authors: Kao Kuo‐Ching , Ho Yu‐Ling , Lin I‐Hsin , Ho Li‐Kang , Chang Yuan‐Shiun
Published: May 2015

Two new flavone glycosides, 3′‐hydroxy‐5,7‐dimethoxyflavone 4′‐O‐β‐D‐apiofuranoside (1), and 5,7‐dimethoxyflavone 4′‐O‐[β‐D‐apiofuranosyl(1→5)‐ β‐D‐glucopyranoside] (2) along with four known compounds, 4′‐hydroxy‐5,7‐dimethoxyflavone (3), 2,6‐dimethoxy‐1,4‐benzoquinone (4), lupeol (5) and betulin (6) were isolated from the stem and roots of Strobilanthes formosanus. Their structures were elucidated on the basis of their spectroscopic evidence.
Enthalpy Change of Allosteric Transition in Human Haemoglobin A
Authors: Amire Olasoji A. , Masoudy J. , Saboury A. A. , Moosavi‐Movahedi A. A. , Ogunmola G. B.
Published: May 2015

Oxygen equilibria of haemoglobin were analysed according to a binding isotherm proposed by Amire (Bull. Chem. Soc. Jpn. 1994, 67, 7)1 to obtain the intrinsic oxygen association constants to the molecule. Two sets of binding sites in haemoglobin were identified, which were ascribed to R2 and T forms of the molecule. The average intrinsic association constants determined as a function of temperature gave a heat of oxygenation of‐76 ± 4 kJ mol−;1 (tetramer). A microcalorimetrically determined heat of deoxygenation of oxyhaemoglobin by dithionite gave −267 ± 10 kJ mol−1 (tetramer). From these results, the heat of allostery of −234 ± 24 kJ mol−1 for haemoglobin tetramer was obtained, yielding allosteric energy per salt bridge of‐29 ± 3 kJ. This result suggests that salt‐bridge may, in fact, be thermochemically equivalent to hydrogen bonds.
One Alkenylphenol and Steroids from the Aquatic Plant Monochoria Vaginalis
Authors: Row Lie‐Ching , Chen Chiu‐Ming , Ho Jiau‐Ching
Published: May 2015

Two new compounds have been isolated from the whole plant of Monochoria vaginalis and characterized as: (10Z)‐1‐(2,6‐dihydroxyphenyl)octadec‐10‐en‐1‐one (1) (20R, 24R)‐campest‐5‐ene‐3β, 4β‐diol (2) together with nine known ones. The structures of these compounds were elucidated on the basis of spectral data and chemical evidence.
Ultrasonic and Volumetric Studies of Molecular Interactions in Acetonitrile + 1‐Alkanol (C6, C8, C10) Binary Liquid Mixtures at Different Temperatures
Authors: Ali Anwar , Nain Anil Kumar , Abida
Published: May 2015

The densities, ρ, and ultrasonic speeds, u, have been measured in the binary liquid mixtures of acetonitrile (ACN) with 1‐hexanol, 1‐octanol and 1‐decanol, and in the pure components, as a function of composition at 25, 30, 35, 40 and 45 °C. The deviations in isentropic compressibility, Δκs, excess molar volume, VE, deviations in ultrasonic speed, Δu, apparent molar compressibility, Kϕ2, apparent molar volume, Vϕ2, partial molar compressibility,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \bar K}^\circ _{\phi,2} $\end{document}, and partial molar volume,\documentclass{article}\pagestyle{empty}\begin{document}$ {\rm \bar V}^\circ _2 $\end{document}, of 1‐alkanols in ACN have been calculated from the experimental data of densities and ultrasonic speeds. The variations of these parameters with composition of the mixtures indicate that the structure‐breaking effect dominates over that of the hydrogen‐bonding effect between unlike molecules, suggesting that ACN‐alkanol interaction is weaker than ACN‐ACN and alkanol‐alkanol interactions, and that the interaction (ACN‐alkanol) follows the order: 1‐hexanol > 1‐octanol > 1‐decanol. The excess molar volume data have been analysed by using Flory and Prigogine‐Flory‐Patterson theories. Further, the ultrasonic speeds in these mixtures were theoretically calculated with the help of several theories and empirical relations using the pure component data. The validity and relative merits of these theories and relations have been discussed.
Kinetic Spectrophotometric Determination of Ranitidine
Authors: Walash Mohammed Ibrahim , Sharaf‐El‐Din Mohie Khalid , Metwally Mohammed El‐Sayed , Shabana Mostafa Reda
Published: May 2015

Two spectrophotometric methods were developed for the determination of ranitidine. The first method was a kinetic spectrophotometric method based on the catalytic effect of ranitidine on the reaction between sodium azide and iodine in an aqueous solution. The calibration graph was linear from 4–24 μg/mL. The drug was determined by measuring the decrease in the absorbance of iodine at 348 nm using a fixed time method. The decrease in the absorbance after 1 minute from the initiation of the reaction was related to the concentration of drug. The detection limit of the procedure was 0.76 μg/mL. The proposed procedure was successfully utilized in the determination of the drug in pharmaceutical preparations with mean recovery in the range of 99.83 ‒ 101.16%.

The second method is a colorimetric method, which depends on the measurement of absorbances of tris (o‐phenanthroline) iron(II) [method 2A] and tris (bipyridyl) iron(II) [method 2B] complexes at 512 nm. The complexes obeyed Beer's law over the concentration range of 2–16 μg/mL and 4–40 μg/mL for methods 2A and 2B, respectively. The developed method has been successfully applied for the determination of ranitidine in bulk drugs and pharmaceutical formulations. The common excipients and additives did not interfere in its determination.
Fast Multi‐residue Screening for 84 Pesticides in Tea by Gas Chromatography with Dual‐tower Auto‐sampler, Dual‐column and Dual Detectors
Authors: Li Hong‐Ping , Li Gwo‐Chen , Jen Jen‐Fon
Published: May 2015

A fast multi‐residue screening method for determining pesticides in tea is described. Pesticides are extracted from tea with acetone and methylene chloride, then enriched and cleaned up with solid phase extraction (SPE) prior to gas chromatographic determination. The fast screening is achieved by a gas chromatograph system equipped with dual‐column, dual‐tower auto‐sampler and both electron capture detector (ECD) and flame photometric detector (FPD). Optimal conditions are investigated for the prospective pesticides including column selection, detection mode, the retention behaviors, quantitative calibration, as well as the recoveries and repeatability of pesticides from tea samples. Under the optimal conditions, with the FPD‐P detector accompanied CP‐SIL 13CB column, 48 pesticides can be separated well and detected within 38 min; and with a DB‐5 column, 35 ECD‐detectable pesticides can be separated and detected within 46 min. The recoveries of 84 pesticides in tea samples are 65–120% with 0.34–16% RSD for spiking 0.02–3.0 mg/kg standard species. Because of the thermal instability of most pesticides, direct cold extraction of pesticides from a tea sample is recommended. The proposed method provided a very fast and efficient procedure to screen 84 pesticides from a complicated tea sample matrix.
Facile Synthesis of (±)‐Parahigginone Methyl Ether and (±)‐Curcuphenol
Authors: Du Zhen‐Ting , Li An‐Pai , Peng Kun , Wu Tong‐Xing , Pan Xin‐Fu
Published: May 2015

Using Grinard coupling as a key step, a facile synthetic approach to (±)‐parahigginone methyl ether 1 and (±)‐curcuphenol 2 has been achieved by five steps with 42.3% and 58.6% overall yield, respectively.
New Approach to N‐substituted‐1,2,3,6‐tetrahydro‐pyridine‐4‐carbaldehyde, a Precursor for Synthesizing Aricept®, Isoguvacine, and Deethylibophyllidine
Authors: Tsai Min‐Ruei , Sun Pei‐Pei , Chang Meng‐Yang , Changa Nein‐Chen
Published: May 2015

A new route towards the synthesis of N‐substituted‐4‐formylpiperidine using N‐benzyl or tryptaminyl‐sulfonylacetamide and α,β‐unsaturated ester as starting materials is described. Formal synthesis of Aricept®, deethylibophyllidine, and isoguvacine, which have potential biological activities, were synthesized via this strategy.
Kinetics and Mechanism of Oxidation of Chromium(III)‐guanosine 5‐Monophosphate Complex by Periodate
Authors: Ewais Hassan A. , Ahmed Samah A. , Abdel‐Khalek Ahmed A.
Published: May 2015

The kinetics of oxidation of the chromium(III)‐guanosine 5‐monophosphate complex, [CrIII(L)(H2O)4]3+(L = guanosine 5‐monophosphate) by periodate in aqueous solution to CrVI have been studied spectrophotometrically over the 25–45 °C range. The reaction is first order with respect to both [IO4−] and [CrIII], and increases with pH over the 2.38–3.68 range. Thermodynamic activation parameters have been calculated. It is proposed that electron transfer proceeds through an inner‐sphere mechanism via coordination of IO4− to chromium(III).
4‐Bromo‐3‐methyl‐1‐phenylpyrazole in Heterocyclic Synthesis: Unexpected Polysubstituted Pyrazole Derivatives
Authors: El‐Rady Eman A. , El Latif Fawi M. Abd
Published: May 2015

Unexpected 4,4′‐dipyrazolomethylidene (7), 4‐amino‐3a‐bromo‐3‐methyl‐1‐phenylpyrazolo[3,4‐b]pyridin‐6‐thione (9), 4,4′‐dipyrazolyl (18), ethyl 4‐(3‐methyl‐1‐phenylpyrazole‐4‐yl)fuoro[2,3‐c]pyrazole‐4‐carboxylate (25), as well as the expected fuoro[2,3‐c]pyrazole derivatives (15), (20) and (28) were isolated from a one‐pot reaction of 4‐bromo‐3‐methyl‐1‐phenylpyrazole (1) with some readily available reagents.
(Pyridine)(tetrahydroborato)zinc Complex Mediated Acetylation of Amines with Ethyl Acetate
Authors: Zeynizadeh Behzad , Zahmatkesh Karam
Published: May 2015

(Pyridine)(tetrahydroborato)zinc complex, (Py)Zn(BH4)2, can efficiently perform acetylation of a variety of aliphatic and aromatic amines with ethyl acetate under refluxing THF.
Flavonol Glycosides and Cytotoxic Triterpenoids from Alphitonia Philippinensis
Authors: Jou Sheng‐Jye , Chen Chung‐Hsiung , Guh Jih‐Hwa , Lee Chun‐Nan , Lee Shoei‐Sheng
Published: May 2015

Three new flavonol glycosides, namely, isorhamnetin 3‐O‐(6″‐O‐(Z)‐p‐coumaroyl)‐β‐D‐glucopyranoside (1), quercetin 3‐O‐α‐L‐rhamnopyranosyl(1 → 2)‐α‐L‐arabinopyranosyl(1 → 2)‐α‐L‐rhamnopyranoside (2), and quercetin 3‐O‐α‐L‐arabinopyranosyl(1 → 2)‐α‐L‐rhamnopyranoside (3), were isolated from the stems of Alphitonia philippinensis. Their structures were established by spectral analysis. In addition, NMR data were assigned for ceanothenic acid (11). Some of the isolated triterpenoids and flavonoid glycosides showed cytotoxicity against human PC‐3 cells and hepatoma HA22T cells, and inhibition of replication on herpes simplex virus type‐1.
Solvent Influence upon Complex Formation between Dibenzo 24‐Crown‐8 and Mg2+, Ca2+, Sr2+ and Ba2+ Cations in Acetonitrile‐Dimethylformamide Binary Mixtures Using the Conductometric Method
Authors: Rounaghi Gholam Hossein , Shahri Effat Esmaily , Abdolrasoul Soleimani
Published: May 2015

The complexation reactions between Mg2+, Ca2+, Sr2+ and Ba2+ cations with macrocyclic ligand, dibenzo‐24‐crown‐8 (DB24C8) were studied in acetonitrile‐dimethylformamide (AN‐DMF) binary mixtures at different temperatures using the conductometry method. In all cases, DB24C8 forms 1:1 complexes with these cations. The values of stability constants of complexes which were obtained from conductometric data, show that the stability of complexes is affected by the nature and composition of the solvent. In many cases, the stability constants of complexes in these solvent systems increase with increasing the concentration of acetonitrile which has a lower donor number than dimethylformamide. However, in the case of complex formation between Mg2+ and Sr2+ cations with DB24C8, an anomalous behaviour was observed for the stability constants (LogKf) with increasing the mole fraction of acetonitrile in AN‐DMF binary mixtures at all temperatures. A non‐linear behaviour was observed for variation of LogKf of the metal ion complexes vs the composition of the mixed solvents. This behaviour may be related to heteroselective solvation of cations and also solvent‐solvent interactions in these binary systems. The obtained results show that the order of selectivity of DB24C8 ligand for the metal cations in different concentrations of acetonitrile in AN‐DMF binary systems is: Ba2+ > Sr2+ > Ca2+ > Mg2+, but a reversal in selectivity is observed in a certain composition of the mixed solvents. The values of thermodynamic parameters (ΔH°c and ΔS°c) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the van't Hoff plots. The results show that in most cases, the complexation reactions are enthalpy destabilized but entropy stabilized, and the values of these thermodynamic parameters are influenced by the nature and composition of the mixed solvents.
Novel Synthesis and Antibacterial Activity of Some Pyridazine Derivatives
Authors: Mohamed M. I. , Zaky H. T. , Kandile N. G.
Published: May 2015

Various pyridazin‐3(2H)‐ones, 3‐chloropyridazines and pyridazin‐3(2H)‐thiones were synthesized and treated with the sulpha drug (knowing by sulphamethoxazole). All the new compounds were evaluated for their antibacterial activity. They showed significant antibacterial activity against Staphylococcus aureus and Bacillus subtilis (Gram + ve) and E. coli, Pseudomonas aeruginosa and Yersinia enterocolitica (Gram ‐ ve) bacteria by agar plate diffusion method.

All proposed structures were confirmed by IR, 1H NMR, Mass spectra and Elemental analysis.
Novel Syntheses of 2,3‐Dihydro‐5H‐1,4‐Benzoxathiepins Using Polymer‐Supported Bis(trifluoroacetoxyiodo)Benzene
Authors: Huang Hsin‐Yu , Wang Huey‐Min , Hou Rei‐Sheu , Chen Ling‐Ching
Published: May 2015

Pummerer‐type reaction was carried out with α‐acyl sulfides and polymer‐supported bis(trifluoroacetoxyiodo)benzene (PSBTI) instead of α‐acyl sulfoxides to prepare 2,3‐dihydro‐5H‐1,4‐benzoxathiepins.
Compared to Synthetic Polymers, Proteins Are Awesome
Authors: Chen Franklin M. C.
Published: May 2015

This paper is written for undergraduate chemistry students who are introduced to the elegant biosynthesis and folding of proteins as compared to synthetic polymers. The uniqueness of proteins among other synthetic and biopolymers is discussed. Proteins are characterized by unique 3‐dimensional structures that are dictated by their 1‐dimensional amino acid sequences. The driving force of the 3‐d conformation lies in the tendency of hydrophobic residues to stay away from an aqueous environment. As a result of such hydrophobic forces, proteins are very compact. Conformational folding is much faster than the time needed for an exhaustive search of the global minimum energy. Additionally, conformational changes induced by environmental factors such as pH, temperature, or ligands are cooperative. Such cooperative folding is given by an example of hemoglobin binding to oxygen molecules. Polymer synthesis designed to mimic protein structures has given useful polymers with many practical applications.
Water‐Exchange Rate and Rotational Dynamics of [Gd(TTDA‐PY)(H2O)]− and [Gd((S)‐4‐Bz‐TTDA)(H2O)]2− in Aqueous Solution: A Variable Temperature 17O NMR Study
Authors: Ou Ming‐Hung , Liu Gin‐Chung , Wang Yun‐Ming
Published: May 2015

17O NMR longitudinal and transverse relaxation rates and chemical shifts were measured at variable temperatures at 9.4 T magnetic fields for aqueous solutions of two Gd(III) TTDA‐like complexes (TTDA = 3,6,10‐tri(carboxymethyl)‐3,6,10‐triazadodecanedioic acid), [Gd(TTDA‐PY)(H2O)] (TTDA‐PY = 3,10‐di‐(carboxymethyl)‐6‐pyridylmethyl‐3,6,10‐triazadodecanedioic acid) and [Gd((S)‐4‐Bz‐TTDA)(H2O)]2− ((S)‐4‐Bz‐TTDA = ((S)‐4‐benzyl‐3,6,10‐tri(carboxymethyl)‐3,6,10‐triazadodecanedioic acid). The results were analyzed in terms of the water‐exchange kinetics and the rotational motion of the complex. The water‐exchange kinetic (kex298) parameters for [Gd(TTDA‐PY)(H2O)] ((30.3 1.8) 106 s−1) and [Gd((S)‐4‐Bz‐TTDA)(H2O)]2− ((115 2.5) 106 s−1) are lower than that of [Gd(TTDA)(H2O)]2− (kex298 = (330 4.0) 106 s−1) and are significantly higher than that of [Gd(DTPA)(H2O)]2− (kex298 = (4.1 0.3) 106 s−1)(DTPA = diethylenetriamine‐N,N,N′,N″,N″‐pentaacetic acid). The higher kex298 values for [Gd((S)‐4‐Bz‐TTDA)(H2O)]2− and [Gd(TTDA)(H2O)]2− suggest that the longer backbone of the multidentate ligand may be pulled tightly into the first coordination sphere, resulting in high steric constraints at the water binding site. The rotational correlation time (τR) for [Gd(TTDA‐PY)(H2O)] (129 ps) and [Gd((S)‐4‐Bz‐TTDA)(H2O)]2− (141 ps) are significantly higher than those of [Gd(DTPA)(H2O)]2− (103 ps)and [Gd(TTDA)(H2O)]2− (75 ps), and this is owing to that R is related to the magnitude of their molecular weight.
Experimental and Theoretical Studies of Protein Folding‐Unfolding
Authors: Shiu Y. J. , Su Catherlene , Yeh Y. L. , Liang K. K. , Hayashi M. , Mo Yan , Yan Yijing , Lin S. H.
Published: May 2015

Recently, a mean field theory of protein folding‐unfolding based on the generalization of the Ising model has been developed. In this work, we apply this theory to obtain averaged coupling energy between two neighbor units in protein and denaturation free energy of protein units. The free energy change of protein folding is found to be 6.0, 5.1, 11.4 kcal mol−1 from absorption, fluorescence, and circular dichroism, respectively; the respective coupling energies of cyt c induced with acid are estimated to be around 10% of the average free energy of protein. The denaturation free energies per molar are determined to be −3400 kcal mol−1 M−1 from absorption, −1260 kcal mol−1 M−1 from fluorescence, and −3180 kcal mol−1 M−1 from circular dichroism.

Fused silica (a hydrophilic surface) is found to play a role to unfold protein and provide a denaturation free energy of−4.05 kcal mole−1. For the case in which protein is denatured by acid on a fused silica surface, the average coupling energy is found to be 85% smaller than the one estimated in bulk solution; the denaturation free energy per molar is found to be 3260 kcal mol−1 M−1.

Another purpose of this paper is to generalize our original kinetic model of protein folding‐unfolding by explicitly taking into account the correlation between protein units. We show that at equilibrium, this new model also yields the same equilibrium as that obtained from our model of thermodynamics of protein folding‐unfolding.
Electronic Communications Mediated by Metal Clusters
Authors: Yip John H. K. , Wu Jianguo , Wong Kwok‐Yin , Ho Kam Piu , Pun Christine So‐Ngan , Vittal Jagadese J.
Published: May 2015

Two model systems [CuI3(dppm)3(μ3‐η1‐C≡CFc)2]•PF6 (1•PF6) and [PtI2(dppm)2(C=CFc)2] (2) were devised to probe the ability of metal clusters in mediating electronic communications. The complexes were characterized by using single‐crystal X‐ray diffraction, UV‐vis spectroscopy, and voltammetry (dppm = bis(diphenylphosphino)methane; Fc = ferrocenyl). The complex is composed a of trimetallic CuI3 core bridged by three dppm and capped with one and two ferrocenylacetylides, respectively. Cyclic and differential pulse voltammograms of 1•PF6 show two reversible Fc oxidations separated by 110 ± 14 mV, giving a comproportionation constant Kc of 77 ± 30. The stability of the mixed‐valence complex 12+ arises mainly from the reduction of electrostatic repulsion and statistical distribution. On the other hand, the Pt‐Pt σ‐bond enhances electronic interactions between the terminal Fc‐groups in compound 2. The CV of the complex shows two reversible Fc‐centered oxidations which are separated by 267 ± 14 mV and the Kc is 3.3 × 104 ± 1.5 × 104. Addition of a d10 AuCl/Br fragment to the Pt‐Pt bond gives rise to complexes [Pt2 (μ‐AuX)(dppm)2(C≡CFc)2] [X = Cl (3) and Br (4)]. The two Fc‐oxidations are not resolved in the CV of the complexes, indicating that the electronic communication is shut down.
Absorbance Behavior of Polyaniline‐Poly(Styrenesulfonic Acid) Complexes and Tungsten Oxide
Authors: Lin Der‐Shyu
Published: May 2015

This research focuses on the UV‐Vis. absorbance spectra of the hybrid organic/inorganic complementary electro‐chromic device (ECD), comprising polyaniline‐poly(styrenesulfonic acid)[PANI‐PSSA] complexes and tungsten oxide (WO3) thin film coupled in combination with a polymer electrolyte poly(2‐acrylamido‐2‐methyl‐propane‐sulphonic acid)[PAMPSA]. PANI‐PSSA microstructure surface images have been studied by AFM. By applying a potential of ˜3.0 V across the two external ITO contacts, we are able to modulate the light absorption also in the UV‐Vis region (200–900 nm) wavelength region. For example, the absorption changes from 1.20 to 0.6 at 720 nm.
Synthesis of Novel Polyfunctionally Substituted Thieno[2,3‐c]pyridazines
Authors: Gaber Abd El‐Aal M. , El‐Gaby Mohamed S. A. , El‐Dean Adel M. Kamal , Eyada Hassan A. , Al‐Kamali Ahmed S. N.
Published: May 2015

4‐Cyano‐5,6‐dimethylpyridazin‐3‐(2H)‐thione 3b was used as a key intermediate for the synthesis of novel polysubstituted thieno[2,3‐c]pyridazines.
Enantioselective Synthesis of Several Natural Virologins
Authors: Su Ying , Ren Xin‐Feng , She Xue‐Gong , Pan Xin‐Fu
Published: May 2015

An enantioselective synthesis of Virologins 1‐(S and R), 2‐trans‐(S and R) and 3‐cis‐(S and R) were achieved by Mitsunobu reaction to construct a chiral center and Ando reagent to form cis‐olefin.
A Novel Preparation of 4‐Phenylquinoline Derivatives in Ionic Liquids
Authors: Zhang Xinying , Fan Xuesen , Wang Jianji , Li Yanzhen
Published: May 2015

A novel preparation of 4‐phenylquinoline derivatives through acid‐catalyzed Friedländer reaction in ionic liquid ([bmim][BF4]) is described. The preparative procedure presented in this paper is operationally simple and environmentally benign. The reaction media and the catalyst used can be recovered and reused for at least four times without loss in the catalytic activity.
Synthesis of New Furo[2,3‐d]pyrimidines and Pyrimido[4′,5′:4,5]furo[2,3‐d]pyrimidines
Authors: Moneam Maisa I. Abdel , Geies Ahmed A. , El‐Naggar Galal M. , Mousa Soliman M.
Published: May 2015

Sodium salt of 4‐hydroxy‐6‐methyl‐2‐phenylpyrimidine‐5‐carbonitrile (3) was subjected to alkylation with different a‐halo compounds, where the corresponding O‐alkylated products 4a‐g were obtained. Ring closure of the O‐alkylated product 4a‐c performed using sodium ethoxide in refluxing ethanol afforded furo[2,3‐d]pyrimidines 5a‐c The latter compounds on reaction with a variety of reagents gave other new furopyrimidines as well as a number of furodipyrimidines.
First Asymmetric Total Synthesis of Mansonone P and R
Authors: Peng Xuanjia , She Xuegong , Wang Zikun , Quan Weiguo , Pan Xinfu
Published: May 2015

An asymmetric total synthesis of Mansonone P and R was achieved. The synthesis highlights an OH substituent at position 2 by Sharpless dihydroxylation of silyl enol ether.
Photohydrodimerization of 6‐Methoxyflavone to 6,6″‐Dimethoxy‐2,2″‐Biflavanones
Authors: Chen Arh‐Hwang , Kuo Wei‐Bao , Chen Chia‐Wen
Published: May 2015

6‐Methoxyflavone (7) easily afforded two hydrodimers of rac‐6,6Prime;‐dimethoxy‐2,2″‐biflavanone (8a) and meso‐6,6″‐dimethoxy‐2,2″‐biflavanone (8b) and one reductive product of 6‐methoxyflavanone (9) by using photolysis with the electron‐donating amines including triethylamine, 2‐(N,N‐dimethylamino)ethanol or N,N‐dimethylaniline in solvents of acetonitrile, benzene or methylene dichloride. They were found to give higher yields of rac‐6,6″‐dimethoxy‐2,2″‐biflavanone (8a) and meso‐6,6″‐dimethoxy‐2,2″‐biflavanone (8b) (38.7% and 4.5%, 35.3% and 6.2%, respectively) in the reaction conditions of 1/10 molar ratio of 6‐methoxy‐flavone (7) to triethylamine in a solvent of acetonitrile with irradiation of twenty‐four hours by using 306 nm and 352 nm lamps.
Correlation of Fluorescence Anisotropy Decay with Molecular Size and Shape of Covalently and Noncovalently Bound Large Porphyrin Arrays
Authors: Aratani Naoki , Yoon Zin Seok , Kim Dongho , Osuka Atsuhiro
Published: May 2015

In this account, we summarize the correlation of fluorescence anisotropy decay times with molecular size and shape of porphyrin aggregates.
Luminescent Transition Metal Polypyridine Biotin Complexes
Authors: Lo Kenneth Kam‐Wing , Hui Wai‐Ki , Chung Chi‐Keung , Tsang Keith Hing‐Kit , Lee Terence Kwok‐Ming , Ng Dominic Chun‐Ming
Published: May 2015

In view of the fact that many transition metal complexes display intense and long‐lived metal‐to‐ligand charge‐transfer emission with a large Stokes' shift, we have incorporated biotin into a series of luminescent rhenium(I), iridium(III) and ruthenium(II) polypyridine complexes to form new probes for the protein avidin. All these luminescent transition metal polypyridine biotin complexes displayed enhanced emission intensities and extended lifetimes upon binding to avidin. These changes are closely related to the hydrophobic biotin‐binding pockets of avidin and the increased rigidity of the local environment of the probes after they bind to the protein. We have exploited the characteristics of these luminescent transition metal biotin complexes in the development of various assays.
Acetylene Elimination in Photodissociation of Neutral Azulene and Its Cation: An Ab Initio and RRKM Study
Authors: Dyakov Yu. A. , Mebel A. M. , Lin S. H. , Lee Y. T. , Ni C.‐K.
Published: May 2015

The ab initio/Rice‐Ramsperger‐Kassel‐Marcus (RRKM) approach in conjunction with ab initio calculations of potential energy surfaces has been applied to investigate the photodissociation mechanism of azulene and its cation at 6.4 eV (wavelength 193 nm) upon absorption of one UV photon followed by internal conversion into the ground electronic state. Reaction pathways leading to several dissociation products have been mapped out at the Gaussian‐3 level and then the RRKM and microcanonical variational transition state theories have been applied to compute rate constants for individual reaction steps. Relative product yields (branching ratios) for dissociation products have been calculated to solve the system of master equations. It is established that the major dissociation channel of neutral azulene is H atom elimination. Pentalene and phenylacetylene as heavy fragments of acetylene elimination reaction could be observed with low yields. Azulene cation dissociates preferably through the pentalene channel. C10H7+, phenylacetylene, and benzocyclobutadiene cations can also be produced with comparable concentrations. Different kinetics of the acetylene elimination reaction have been revealed in the cases of neutral and charged azulene.