Synthesis of Derivatives of Chlorin P6 Trimethyl Ester

The Vilsmeier reaction of nickel(II) chlorin P₆ trimethyl ester with 3-dimethyl-aminoacrolein yielded nickel(II) chlorin P₆ 20-(2-formylvinyl) trimethyl ester and nickel(II) chlorin P₆ 3-(1-hydroxyethyl)-3-devinyl-20-(2-formylvinyl) trimethyl ester. Also, the outgrowths of nickel(II) chlorin P₆ 20-(2-formyl) trimethyl ester and nickel(II) chlorin P₆ 3-(2-formylvinyl)-3-devinyl-20-(2-formyl) trimethyl ester were obtained by Vilsmeier reaction with dimethylformamide. By treating the derivatives of nickel(II) 20-(2-formyl)-chlorin and nickel(II) 3-(2-formylvinyl)-20-(2-formyl)-chlorin with trifluoracetic acid, the removal of the central nickel(II) ion was accomplished. The derivatives of 20-(2-formyl)-chlorin and 3-(2-formylvinyl)-20-(2-formyl)-chlorin demonstrated considerable bathochromic shift of the major absorption band in the red region of the optical spectrum.     

黄花倒水莲皂甙Reinioside C在大鼠体内代谢产物的鉴定

为了探讨五环三萜皂甙ReiniosideC在大鼠体内代谢产物的结构,单剂量口服ReiniosideC,5h后放血处死,用制备型高效液相色谱方法对血液和各脏器进行提取分离,从大肠内容物和粪中,分离得到了7种代谢产物.用FAB-MS,¹H NMR和¹³C NMR方法鉴定了它们的结构.     

Mixed-ligand complex formation equilibria of CuII with biguanide in presence of glycine as the auxiliary ligand

Equilibrium study on the mixed ligand complex formation of Cu^II with biguanide(Bg) and glycine (HG), indicated the formation of the complexes: Cu(Bg)²⁺, Cu(Bg) ₂ ²⁺ , Cu(Bg-H)(Bg)+, Cu(Bg-H)₂, Cu(Bg)(OH)⁺, Cu(Bg-H)(OH); Cu(G)⁺, Cu(G)(OH), Cu(G)₂; Cu(G)(Bg)⁺, Cu(G)(Bg-H); (G)Cu(Bg)Cu(G)²⁺, (G)Cu(Bg-H)Cu(G)⁺, and (G)Cu(Bg-2H)Cu(G). From the deprotonation constants of coordinated biguanide (Bg) in the complexes Cu(Bg)(OH)⁺, Cu(Bg-H)(Bg)⁺ and Cu(G)(Bg)⁺, the Lewis basicities of the coordinated ligand species (Bg-H)^-, OH^- and glycinate (G^-) were found to be of the order: (Bg-H)^-≫ OH^- > G^-. Bridging (N¹-N⁴, N²-N⁵) tetradentate mode of coordination by biguanide species Bg, (Bg-H)^- and (Bg2H)^2- was indicated from the occurrence of biguanide-bridged dinuclear mixed ligand complexes (G)Cu(Bg)Cu(G)²⁺, (G)Cu(Bg-H)Cu(G)⁺, (G)Cu(Bg-2H)Cu(G) in the complexation equilibria.     

Potentiometric Study of Tetracycline and Oxytetracycline with some Metal Ions of Biological Interest

Abstract

The stepwise metal-ligand stability constants of tetracycline and oxytetraoycline chelates with Mg(II), Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Cu(II), Zn(II), Zr(II) and Sn(II) have been determined using the Bjerrum-Calvin titration technique as employed by Irving and Rossotti. Protonation constant of the ligand and stability constants of the respective metal complexes have been determined at constant temperature (25°C) and ionic strength (0.1 M KCl). The general order of overall stability constant values have been found to be: Zr(IV) > Fe(III) > Co(II) > Zn(II) > Mg(II) > Mn(II) > Ni(II) > Sn(II) > Tn(II) > Cr(II). The rign values of the atability constanta are attricutel to the Ligands, which are stronger as an acid and weaser as a oase.     

Comparison of the properties of waterborne polyurethane-ureas containing different triblock glycols for water vapor permeable coatings

Four types of triblock glycols [(CL)_4.5-PEG-(CL)_4.5, (CL)_4.5-PTAd-(CL)_4.5, (CL)_4.5-PTMG-(CL)_4.5, and (CL)_4.5-PPG-(CL)_4.5, Mn=3,000] were synthesized by end-capping reactions of -caprolactone (CL) and poly(ethylene) glycol (PEG, Mn=2,000), poly(tetramethylene adipate) glycol (PTAd, Mn=2,000), poly(tetramethylene) glycol (PTMG, Mn=2,000), or polypropylene glycol (PPG, Mn=2,000)]. Waterborne polyurethanes (WBPUs) were prepared by polyaddition reaction using 4,4-dicyclohexylmethane diisocyanate (H₁₂MDI), 2,2-bis (hydromethyl) propionic acid (DMPA), ethylene diamine (EDA), triethyl amine (TEA), and the triblock glycol. Studies have been conducted on the effects of triblock glycol type on the colloidal properties of dispersion, the hardness and mechanical properties of WBPU films, the water vapor permeability (WVP), and water resistance (WR) of WBPU-coated nylon fabrics. The WVP (%WVP based on control nylon fabric) of WBPU-coated nylon fabrics based on (CL)_4.5-PEG-(CL)_4.5, (CL)_4.5-PTAd-(CL)_4.5, (CL)_4.5-PTMG-(CL)_4.5 and (CL)_4.5-PPG-(CL)_4.5 were 3,975(81), 3,115(62), 3,124(64), and 2,569(52) g/m² day (%), respectively. However, the WBPU based on (CL)_4.5-PEG-(CL)_4.5 was not applicable for coating material, because its dispersion and film had relatively high viscosity (3,000 cps at 50°C) and low mechanical properties, respectively. In this work, the triblock glycols (CL)_4.5-PTMG-(CL)_4.5 and (CL)_4.5-PTAd-(CL)_4.5 were found to be desirable glycols for water vapor permeable coating materials.     

Structural Chemistry of Magnesium Acetates

Magnesium acetate solvates, Mg(OAc)₂ · nL, and their hydrates were prepared by crystallization of Mg(OAc)₂ · 4H₂O or Mg(OAc)₂ from different solvents (L = MeOH, EtOH, HOAc). Anhydrous Mg(OAc)₂ was obtained by thermal dehydration of the tetrahydrate at 150 °C. X‐ray single crystal diffraction mostly with the use of synchrotron radiation allowed the structure determination of Mg(OAc)₂(H₂O)₃(EtOH) ( I ), Mg(OAc)₂(HOAc)₂(H₂O)₂ ( II ), Mg₃(OAc)₆(MeOH)₆ ( III ), Mg₃(OAc)₆(HOAc)₂(H₂O)₂ · 2HOAc ( IV ), Mg(OAc)₂(HOAc) · 1.8(HOAc) ( V ), Mg(OAc)₂ · H₂O ( VI ), [Mg₃(OAc)₆(EtOH)₂] · 2EtOH ( VII ), and Mg(OAc)₂ ( VIII ). Structural data were discussed in terms of the number of neutral O‐donor ligands per magnesium atom, coordination environment of magnesium atoms, structural functions of acetate groups, and hydrogen bonding systems.     

A DFT Study of the Models of the Bronsted Acid Sites of Zeolite Catalysts

A systematic study of the different cluster models of the Bronsted site has been carried out in order to predict how the local structure influences the geometric parameters of the SiO(H)Al site and the harmonic frequencies of the characteristics vibrational modes of the bridging surface hydroxyl group. The performance of the B3LYP variant of the density functional theory (DFT) method is examined and compared with both SCF HF and MP2 approximations. In order to find the best molecular model for the Bronsted site, two series of derivatives based on the prototype model cores SiO(H)Al and HAlO₄ were considered. In the HAlO₄ series, H₃SiO(H)Al(OH)₂OSiH₃ and H₃SiO(H)Al(OSiH₃)₃ were investigated. Among the models in the SiO(H)Al series were H₃SiO(H)AlH₃, H₃SiO(H)Al(OH)₃, H₂(OH)SiO(H)Al(OH)₃, (OH)₃SiO(H)Al(OH)₃, and (H₃SiO)₃SiO(H)Al(OSiH₃)₃. The research reveals that the acidic OH bond length and its stretching frequency are greatly influenced by the H bond formed between the acidic proton and its next-nearest neighbor oxygen on the aluminum atom. The geometry and the frequencies for the larger models predicted at the B3LYP/D95(d,p) level are in good agreement with the experiments, suggesting that the B3LYP/D95(d,p) theory is reliable for a study of the Bronsted site. This study also suggests that the OH terminated models are not suitable as models for the SiO(H)Al site due to the strong dipole moment of the OH group, which strongly affects the acidic H.     

Synthesis of functionalised cyclopentanes by intramolecular radical-mediated cyclisations of terminal allenic ketones

Electrolysis of a series of terminal allenic ketones e.g. (7), (10), (17) and (21) is shown to result in intramolecular reductive cyclisation, through the $\text{exo}$-mode, producing five-membered rings, $\text{viz}$ (8), (9), (20) and (22) respectively, incorporating a bridgehead hydroxyl group. The unsaturated alcohols (8), (20) and (22), are also obtained when the allenic ketones (7), (17) and (21) are treated with sodium naphthalenide. By contrast treatment of (10) in the sodium naphthalenide gives a low yield ($\text{ca}$ 7%) of the isomeric indenol (11) by cyclisation through the $\text{endo}$-mode.Reductive cyclisations of the terminal acetylenic ketones (14) and (30) produce the corresponding unsaturated alcohols (26) and (31) respectively. Treatment of the alcohols (26) and (31) with catalytic selenium dioxide then provides the enediols (27) and (32) respectively, which make up the B/C ring systems of the novel marine natural products capnellenediol (1) and isoamijiol (2).     

Synthesis of carbosilane block copolymers by means of a living anionic polymerization of 1,1-diethylsilacyclobutane

Block polymerization of 1,1-diethylsilacyclobutane with styrene derivatives and methacrylate derivatives was investigated. Sequential addition of styrene to a living poly(1,1-diethylsilabutane), which was prepared from phenyllithium and 1,1-diethylsilacyclobutane in THF–hexane at −48°C, gave poly(1,1-diethylsilabutane)-b-polystyrene. Similarly, addition of 4-(tert-butyldimethylsiloxy)styrene to the living poly(1,1-diethylsilabutane) provided poly(1,1-diethylsilabutane)-b-poly(4-(tert-butyldimethylsiloxy)styrene). Poly(1,1-diethylsilabutane)-b-poly(methyl methacrylate) was obtained by treatment of living poly(1,1-diethylsilabutane) with 1,1-diphenylethylene followed by an addition of methyl methacrylate. Poly(1,1-diethylsilabutane)-b-poly(2-(tert-butyldimethylsiloxy)ethyl methacrylate) was also synthesized by adding 2-(tert-butyldimethylsiloxy)ethyl methacrylate to the living poly(1,1-diethylsilabutane) which was end-capped with 1,1-diphenylethylene in the presence of lithium chloride. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2699–2706, 1998     

Electron diffraction study of molecular structure of mebicar

The structure of the mebicar molecule has been studied by gas-phase electron-diffractometry using quantum chemical calculations. An eclipsed conformation along the C-C bond (torsion angle ?(H-C-C-H) = 10°) and flattened semi-chair conformations of cyclic fragments have been found. The bond lengths (r _g ) and angles (∠α) show the following average values: r(C-C) 1.576(3) Å, r(C-N) 1.460(3) Å, r(C(O)-N) 1.390(4) Å, r(C=O) 1.211(5) Å, r(C-H) 1.090(5) Å, ∠CCN 103.0(5)°, ∠CNC(O) 112.2(1)°, ∠CNC 122.4(1)°. The dihedral angle between the cyclic fragments is 116.6°.     

Minimization of side reactions during Lys Tag derivatization of C-terminal lysine peptides

Several issues need to be considered concerning chemical labeling strategies in proteomics. Some of these are labeling specificity, possible side reactions, completeness of reaction, recovery rate, conserving integrity of sample, hydrolysis of peptide bonds at high pH, and signal suppression in mass spectrometry (MS). We tested the effects of different reaction conditions for 2-methoxy-4,5-dihydro-1H-imidazole (Lys Tag) derivatization of the ?-amine group of lysine (K) residues. By using nanoflow LC–electrospray ionization-MS (LC–ESI-MS) and MS/MS in combination with MSight 2-D image analysis, we found that standard Lys Tag derivatization processes and conditions induce side reactions such as (i) Lys Tag labeling of the N-terminus, (ii) methylation of internal aspartic acid (D), glutamic acid (E) and C- and N-peptide termini and (iii) deamidation of asparagine (N) and glutamine (Q). We found temperature and pH to be the main variables to control side reactions. Lowering the reaction temperature from 55 °C to room temperature reduced deamidation from 22.8 ± 1.4% (SEM) to 7.7 ± 5.5% (SEM) and almost totally blocked methylation (7.0 ± 1.2% (SEM) to 0.4 ± 0.4% (SEM) of the internal acidic amino acids (D and E) at high pH. We conclude that lowering the reaction temperature minimizes undesired side reactions during Lys Tag derivatization in solution.     

The reductive dimerization of some 1,3-dienes and of 1,3,5-cycloheptatriene in the presence of trimethylchlorosilane: a DFT investigation

Treatment of 1,3-dienes and 1,3,5-cycloheptatriene by chlorotrimethylsilane in the presence of wire of lithium led mainly to reductive dimerization with formation of bis(allylsilane) derivatives. Bis-silyl compounds obtained: from 1,3-butadiene, 1,8-bis(trimethylsilyl)-2,6-octadiene (70%); from isoprene, (Z,Z)-2,7-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (44%) and 2,6-dimethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (19%); from butadiene-isoprene mixture (1:1), 3-methyl-1,8-bis(trimethylsilyl)-2,6-octadiene (55%); from 2,3-dimethylbutadiene, (E,E)-2,3,6,7-tetramethyl-1,8-bis(trimethylsilyl)-2,6-octadiene (36%), from 1,3-cyclohexadiene, 4,4′-bis(trimethylsilyl)-bicyclohexyl-2,2′-diene (48%); from 1,3,5-cycloheptatriene, 1,1′-bi[(S^∗,S^∗)-6-(trimethylsilyl)cyclohepta-2,4-dien-1-yl] (53%). The structure of the various intermediates (radical anion, dianion, silylated radical, silylated anion) has been established by calculations at the B3LYP/6-311++G(d,p) level of theory with zero-point energy correction. These results are in accordance with a pathway including the formation of a radical anion, its silylation furnishing to a γ-silylated allylic radical followed by a dimerization reaction in the head to head manner.     

Synthesis of coordination compounds of dibutyltin(IV) with Schiff bases having nitrogen donor atoms

The new dibutyltin(IV) complexes of Schiff bases is designed & synthesis from the interaction between various substituted amines and aromatic aldehyde with general formula Bu₂Sn(L^1-7)₂Cl₂. Where L¹: (E)-4-chloro-N-(thiophen-2-ylmethylene) aniline; L²: (E)-2-chloro-N-(3,4,5-trimethoxybenzylidene) aniline; L³: (E)-N-((1H-indol-3-yl) methylene)-4-chloro-2-nitroaniline; L⁴: (E)-4-nitro-N-(3,4,5-trimethoxybenzylidene) aniline; L⁵: (E)-N-(3,4,5-trimethoxybenzylidene) aniline; L⁶: (E)-4-nitro-N-(thiophen-3-ylmethylene) aniline; L⁷: (E)-4-chloro-2-nitro-N-(pyridin-3-ylmethylene) aniline. Analytical and spectroscopic methods, such as molar conductance measurement, UV–Vis, IR, NMR, and DFT studies, have been used to describe newly synthesised compounds. The DFT studies have also provided confirmation regarding the complexes' geometry. The results of the Tauc equation indicate that the fundamental band gap of the compound [Bu₂Sn(L⁵)₂Cl₂] is 2.670 eV, which is in agreement with the findings of DFT studies, which indicate that the band gap is 2.657 eV. The bactericidal effects of Schiff bases and their dibutyltin(IV) complexes were tested. The antibacterial activity of organotin(IV) complexes is enhanced in comparison to that of the free ligands.     

Constituents of Flowers of Murraya Paniculata

Three new coumarins, yuehgesin-A (1), -B (2) and -C (3) and 22 compounds—murracarpin (4), mupanidin (5), isomeranzin (6), murralongin (7), scopoletin (10), 7-methoxy-8-(l′-ethoxy-2′-hydroxy-3′-methyl-3′-butenyl)coumarin (11), umbelliferone (12), paniculatin (13), braylin (14), auraptenol (15), meranzin hydrate (16), minumicrolin (17), scopolin (18), caffeine (19), 3,3′,4′,5,5′,6,7-heptamethoxyflavone (20), 4-hy-droxybenzaldebyde (21), p-hydroxybenzoic acid (22), cis- and trans-ferulic acid (23), cis- and transmethyl ferulate (24) and trans-ethylferulate (25)—were isolated and characterized from fresh flowers of Murraya paniculata collected in Taiwan. Their structures were elucidated by spectral methods. The chemotaxonomy of Murraya paniculata is, discussed.     

The formation of self-assembled monolayers of thiophthalocyanine complexes of titanium, vanadium and manganese and their use in l-cysteine electrocatalysis

Self-assembled monolayers (SAMs) based on octapentylthiophthalocyanine complexes of oxovanadium (IV) (OVOPThPc), titanium(IV) (OTiOPThPc), and manganese (III) acetate (AcMnOPThPc), and of tetraphenylthiophthalocyanine complexes of hydroxo manganese(III) (OHMnTPPc) and oxotitanium(IV) (OTiTPPc) are described. The oxidation of l-cysteine was observed at potentials which ranged from 0.52 V to 0.67 V. The detection limits for l-cysteine analysis were of the order of 10^− 7 to 10^− 6 M.     

Ab initio and DFT theory studies of interaction of thymine with formaldehyde

In this article, the interaction of formaldehyde (FA) with thymine is theoretically investigated by computational chemistry methods. The optimization geometries and vibrational frequencies of FA, thymine and three complexes between thymine and FA have been calculated by using the density functional theory and ab initio methods at the B3LYP/6-311G(d, p) and MP2/6-311G(d, p) levels. The NBO and AIM methods are used to analyse interaction as well. Conformers (A), (B) and (C) are cyclic structures with C–H***O and N–H***O hydrogen bonds on a common plane. The corrected complex interaction energies of cyclic structures (A), (B) and (C) at MP2/6-311G(d, p) levels are −38.41, −26.94 and −26.01 kJ/mol, respectively. The order of stability is (A) > (B) > (C).     

Synthesis of plant arabinogalactans

Plant arabinogalactans consisting of a β-(1→6)-linked D-galactopyranosyl oligosaccharide back-bone with α-(1→2)-L-arabinofuranosyl branches are synthesized based on the 1,2-anhydro galactopyranose technique, orthogonal (methoxydimethyl)methyl (MIP) and (2-naphthyl)methyl (NAP) protection strategy, and selective acylation or glycosylation method. The third method is the most simple and effective and it is also used for the synthesis of arabinogalactans composed of a β-(1→6)-linked D-galactopyranosyl oligosaccharide backbone with α-(1→3)-L-arabinofuranosyl branches.     

Thermal Properties of N-ethyl-N-phenyl-Dithiocarbamates and Their Influence on the Kinetics of Cure

The thermal properties (in the temperature range of 100–250°C) of N-ethyl-N-phenyldithiocarbamatecomplexes of Zn(II), Co(III), Ni(II), Cu(II) and Pb(II) and their influence on the kinetics of cure have been studied by differential scanning calorimetry (in nitrogen). It was found that Zn(II), Co(III) and Pb(II) dithiocarbamates melted without further effects, while the melting of Ni(II) and Cu(II) dithiocarbamates is accompanied with decomposition. From the kinetic point of view, the dithiocarbamates decrease the values of the reaction order and the values of rate constants follow this order (with respect to the metal ion): Zn(II)<Cu(II)<Pb(II)<Ni(II)<Co(III).This revised version was published online in November 2005 with corrections to the Cover Date.     

Electrochemiluminescence Studies of Phosphorescent Dopant and Host Molecules of Polymer Light-emitting Diodes

Electrochemiluminescence (ECL) from tris(2‐phenylpyridine)irdium [Ir(ppy)₃] was investigated following cross reaction of its anion with oxidized poly(N‐vinyl‐carbazole) (PVK) and its cation with reduced 2‐(4‐biphenylyl)‐5‐(4‐tert‐butyl‐phenyl)‐1,3,4‐oxadiazole (PBD). Both cross reactions show Ir(ppy)₃ emission and the cross reaction of PVK^+·/Ir(ppy)⁻₃ showed the highest ECL intensity. The comparisons of the reaction enthalpy and the energy of Ir(ppy)₃ light emitting shows that reaction between PVK^+· and Ir(ppy)⁻₃ is energy sufficient to populate metal‐to‐ligand charge transfer (MLCT) excited singlet (3.04 eV) of Ir(ppy)₃, while the reaction between Ir(ppy)⁺₃ and PBD^{− ·} is energy efficient to populate MLCT excited triplet (2.4 eV). The ECL result in solution reveals that the energy released from charge transfer between the Ir(ppy)₃ and PVK or PBD is sufficient to produce the excited state of Ir(ppy)₃ in solid polymer light‐emitting diodes (PLEDs) based on PVK:PBD hosts doped by Ir(ppy)₃. These results obtained will provide further insight into charge‐transfer excitation in PLEDs.     

Reaction of sulfur-containing structural units of transition metals

Two tri-n-butylphosphme-participated ( PBu3n) nickel (Ⅱ) complexes of 2-mercaptophenol(H2mp),i.e,Ni2Ru(mp)3(Hmp)(PBu3n)3 3 exhibiting a curved heterotrinuclear metal skeleton and its mononuclear "synthon",[HNEt3] [Ni(mp) (Hmp) (PBu3n)] 1 were synthesized and characterized by X-crystallography and 1H NMR,FAB-MS and cyclic valtammogram measurements.The nickel(Ⅱ) center in 1 has a square-planar geometry For 3,the ruthenium(Ⅲ) atom is in a distorted octahedral environment and the two mckel(Ⅱ) atoms exhibit square-planar and rare triangle-planar geometries,respectively.The Ni (1)-Ru-Ni(2 ) arrangement is severely asymmetric with the distances 0.254 and 0.394 nm,respectively,for Ni(1)-Ru and Ni(2)-Ru.The structural regularities of relevant complexes are summarized in relation to the structural as well as spectra data.