Syntheses and reactions of porphyrin and metalloporphyrin polymers

Various porphyrin functions such as protoporphyrin IX and chlorin a as well as metalloporphyrin functions such as Mg(II)– and Cu(II)–chlorophyllin a and Fe(III)– and Co(II)–protoporphyrin IX were incorporated into vinyl polymers by preparation and polymerization of their p-vinylbenzyl esters. The porphyrin function was also incorporated by reaction of poly-p-chloromethylstyrene with porphyrins or metalloporphyrins or by the reaction of p-aminostyrene polymers with chlorophyll b through Schiff-base formation. Mg(II)–porphyrin polymers were found to be remarkably effective as catalysts in photoredox systems; porphyrin polymers without central metal atoms were also effective to a lesser extent.     

Syntheses and characterization of statistical and block fluorinated copolymers with linear and star-like architectures via ATRP

The synthesis of a fluorinated macroinitiator for copper-catalyzed atom transfer radical polymerization (ATRP) is reported, as well as its use for the controlled living polymerization of poly(propylene glycol) methacrylate (PPGM) in MEK at 80 °C. The ATRP system used was efficient for polymerization of the functionalized monomer and the molecular weight of the polymer estimated by NMR spectroscopy was in close agreement with the theoretical molecular weight, as expected for controlled processes. The statistical copolymerization of PPGM or methyl ether poly(ethylene glycol) methacrylate (MPEGMA) with a perfluoroalkyl ethyl methacrylate by copper-mediated ATRP was also investigated and led to copolymers with essentially random incorporation of monomers. The syntheses and characterization of star-like homopolymers of MPEGMA or the fluorinated monomer via ATRP are also reported, as well as an amphiphilic star-like block copolymer containing ethyleneglycol units as the core and fluorinated moieties in the shell. The micellar behavior of this copolymer was investigated as a function of the external environment.     

Cyclic beta-tetra- and pentapeptides: synthesis through on-resin cyclization and conformational studies by X-ray, NMR and CD spectroscopy and theoretical calculations

The solution-phase synthesis of the simplest cyclic beta-tetrapeptide, cyclo(beta-Ala)4 (4), as well as the solid-phase syntheses through side chain anchoring and on-resin cyclization of the cyclic beta3-tetrapeptide cyclo(-beta3hPhe-beta3hLeu-beta3hLys-beta3hGln-) (14) and the first cyclic beta3-pentapeptide cyclo(-beta3hVal-beta3hPhe-beta3hLeu-beta3hLys-beta3hLys-) (19) are reported. Extensive computational as well as spectroscopic studies, including X-ray and NMR spectroscopy, were undertaken to determine the preferred conformations of these unnatural oligomers in solution and in the solid state. cyclo(beta-Ala)4 (4) with no chiral side chains is shown to exist as a mixture of rapidly interchanging conformers in solution, whereas inclusion of chiral side chains in the cyclo-beta3-tetrapeptide causes stabilization of one dominating conformer. The cyclic beta3-pentapeptide on the other hand shows larger conformational freedom. The X-ray structure of achiral cyclo(beta-Ala)4 (4) displays a Ci-symmetrical 16-membered ring with adjacent C=O and N-H atoms pointing pair wise up and down with respect to the ring plane. CD spectroscopic examinations of all cyclic beta-peptides were undertaken and revealed results valuable as starting point for further structural investigations of these entities.     

Fragmentation reactions of singly and doubly protonated thiourea- and sugar-substituted cyclams and their transition-metal complexes

Cyclam macrocycles tetrasubstituted with amino-, thiourea-, and sugar-terminated side chains are ionized by electrospray ionization mass spectrometry (ESI-MS) as singly or doubly protonated species or as transition-metal complexes. Their fragmentation behavior is examined in a Fourier-transform ion-cyclotron-resonance (FT-ICR) mass spectrometer by collision-induced dissociation (CID) experiments. Typically, fragmentation occurs within the side chains through a number of different 1,2-elimination reactions irrespective of the absence or presence of a transition metal ion such as Co(2+), Ni(2+), or Zn(2+). A remarkable exception is Cu(2+), which induces ring cleavage reactions. This is traced back to an electron transfer from the cyclam nitrogen atoms to the Cu(2+) ion. The electron transfer creates a cation-radical within the macrocycle, which induces typical fragmentation reactions such as alpha-cleavages that lead to fragmentation within the macrocycle. This interpretation is in line with fragmentation experiments on unsubstituted cyclam and its complexes.     

Catalytic and enantioselective aza-ene and hetero-Diels-Alder reactions of alkenes and dienes with azodicarboxylates

Lewis acids such as Cu(OTf)(2), Zn(OTf)(2), Yb(OTf)(3) and Nd(OTf)(3) catalyze the aza-ene reaction of alkenes with azodicarboxylates, giving the allylic amination adducts. The use of bis(2,2,2-trichloroethyl)azodicarboxylate as the amination reagent and Cu(OTf)(2) and Yb(OTf)(3) as the catalysts gave the aza-ene reaction of different alkenes, leading to the corresponding allyl amines in high yields. Chiral copper complexes prepared from Cu(OTf)(2) and chiral bisoxazoline ligands were found to catalyze the enantioselective aza-ene reaction of azodicarboxylates with alkenes and the hetero-Diels-Alder reaction with cyclopentadiene, giving the corresponding aza-ene- and hetero-Diels-Alder adducts, respectively, in good yields and moderate enantioselectivities.     

Electronic Structure and Substitution and Redox Reactivity of Imidazolate-Bridged Complexes of Pentacyanoferrate and Pentaammineruthenium

The mixed-valence compound [(NC)(5)Fe(II)-Im-Ru(III)(NH(3))(5)](-),M(i), was prepared in solution and as a solid sodium salt from [Fe(CN)(5)H(2)O](3)(-) and [Ru(NH(3))(5)Im](2+). The binuclear complex shows two bands at 366 nm (epsilon = 3350 M(-)(1) cm(-)(1)) and 576 nm (epsilon = 1025 M(-)(1) cm(-)(1)), assigned as LMCT transitions, as well as a near-IR band at 979 nm (epsilon = 962 M(-)(1) cm(-)(1)) associated with an intervalence transition. By calculation of the Hush model parameters alpha(2) and H(ab) (delocalization and electronic coupling factors, respectively), the complex is defined as a valence-trapped Fe(II)-Ru(III) system; this is confirmed by the measured redox potentials at -0.20 V and 0.30 V, associated with redox processes at the ruthenium and iron center, respectively. The formation stability constant of the mixed-valence ion was obtained through independent measurements of k(f) and k(d), the formation and dissociation specific rate constants, respectively. The stabilization of M(i) with respect to disproportionation into the isovalent states, as well as toward the formation of the electronic isomer, Fe(III)-Im-Ru(II), was also estimated. The fully reduced (R(i)) and fully oxidized (O(i)) binuclear complexes were prepared in solution and characterized by UV-vis spectroscopy. The kinetics of the reactions of R(i) and M(i) with peroxydisulfate were measured and a mechanistic analysis was performed, showing the relevance of electronic isomerization in completing the full conversion to O(i), through the assistance of the Ru(II)(NH(3))(5)(2+) center in the oxidation of the neighboring Fe(II)(CN)(5)(3)(-) moiety. The latter results are compared with those obtained with related complexes comprising different X(5)M-L moieties bound to Ru(II)(NH(3))(5)(2+). A linear correlation is displayed by plotting ln k(et) against E degrees (Ru), associated with the intramolecular oxidation rate constant of Ru(II) in the ion pair (binuclear species + peroxydisulfate) and the reduction potential of the corresponding Ru(III,II) couple in the ion pair.     

Synthesis and thermal characterization of new ternary chelates of piroxicam and tenoxicam with glycine and DL-phenylalanine and some transition metals

The ternary chelates of piroxicam (Pir) and tenoxicam (Ten) with Fe(II), Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in the presence of various amino acids such as glycine (Gly) or dl-phenylalanine (PhA) were prepared and characterized with different physicochemical methods. IR spectra confirm that Pir and Ten behave as a neutral bidentate ligand coordinated to the metal ions via the pyridine-N and carbonyl group of the amide moiety. Gly molecule acted as a uninegatively monodentate ligand and coordinate to the metal ions through its deprotonated carboxylic group. In addition, PhA acted as a uninegatively bidentate ligand and coordinate to the metal ions through its deprotonated carboxylic and amino groups. The solid reflectance spectra and magnetic moment measurements confirm that all the chelates have octahedral geometrical structures while Cu(II)- and Zn(II)-ternary chelates with PhA have square planar geometrical structures. Thermal behaviour of the complexes is extensively studied using TG and DTA techniques. TG results show that water molecules (hydrated and coordinated) and anions are removed in the first and second steps while Gly, PhA, Pir and Ten are decomposed in the next and subsequent steps. The pyrolyses of the chelates into different gases are observed in the DTA curves as exo- or endothermic peaks. Also, phase transition states are observed in some chelates. Different thermodynamic parameters are calculated using Coats-Redfern method and the results are interpreted.     

Spectroscopy and photophysics of methylphenylsiloxaneand diphenylsiloxane-based molecules and polymers

Spectroscopy and photophysics of various types of methylphenylsiloxane- and diphenylsiloxane-based oligomers and polymers are reviewed. The molecules treated here include homopolymers such as poly(methylphenylsiloxane) and copolymers such as poly(dimethylsiloxane-codiphenylsiloxane) as well as related oligomers or molecules such as diphenyltetramethyldisiloxane. These polymers and oligomers normally exhibit monomer fluorescence in fluid solution at temperatures near room temperature, and the monomer fluorescence and phosphorescence in rigid matrices at 77 K. In addition to these emissions, the excimer fluorescence is often observed depending on the molecular structure of the siloxanes. These emission properties are rationalized based on the molecular structure and kinetics of the excimer formation processes as well as on the flexibility of the Si-O-Si bonds.     

Development and applications of the interfacial tension between water and organic or biological surfaces

The interfacial tension (gamma(SW)) between a condensed-phase material (S) and water (W) is one of the most important terms occurring (directly or indirectly) in the major surface thermodynamic combining rules, such as the different variants of the Dupré equation, as well as the Young and the Young-Dupré equations. Since the late 1950s, gamma(SL) (where L stands for liquid in general) could be correctly expressed, as long as one only took van der Waals attractions and electrical double layer repulsions into account, i.e., as long as both S and L were apolar. However for interfacial interactions taking place in water among apolar as well as polar solutes, particles or surfaces, gamma(SW) was not properly worked out until the late 1980s, due in particular to uncertainties about the treatment of the polar properties of liquid water and other condensed-phase materials. In this review the historical development of the understanding of these polar properties is outlined and the polar equation for gamma(SW), as well as the equations derived there from for the free energies of interaction between apolar or polar entities, immersed in water (deltaG(SWS)) are discussed. Also discussed is the role of the various terms of deltaG(SWS), in hydrophobic attraction (the "hydrophobic effect"), hydrophilic repulsion ("hydration forces") and in the quantitative expression of hydrophobicity and hydrophilicity. The DLVO theory of attractive and repulsive free energies between particles immersed in liquids, as a function of distance between suspended particles, was extended to allow its use in the expression of the polar interactions occurring in water. Finally, the free energy term, deltaG(SWS) and the related gamma(SW), have been directly linked to the aqueous solubility of organic and biological solutes, which allows the determination of interfacial tensions between such solutes and water from their solubilities.     

On the syntheses and some reactions of bis- and tris(methylthio)thiophenes

Reaction between various thienyllithium derivatives and dimethyl disulfide has been used for the preparation of 2,5-, 2,3-, and 3,4-bis(methylthio)thiophenes, as well as 2,3,4- and 2,3,5-tris(methylthio)thiophenes. Bromination of (methylthio)thiophenes with N-bromosuccinimide was found to be most convenient for the preparation of brominated (methylthio)thiophenes such as 3-bromo-2,5-bis(methylthio)- and 5-bromo-2,3-bis(methylthio)thiophene, 3,4-dibromo-2,5-bis(methylthio)-, 2,5-dibromo-3,4-bis(methylthio)- and 2,3-dibromo-4,5-bis(methylthio)thiophene as well as 3-bromo-2,4,5-tris(methylthio)thiophene. The reaction of methylthio substituted thienyllithium derivatives with methyl chloroformate was used for the syntheses of methyl methylthio substituted thiophenecarboxylates and using 1/3 of an equivalent for the direct preparation of methylthio substituted 3-thienylcarbinols as tris[2,4,5-tris(methylthio)-3-thienyl]carbinol.     

Flavonoids from Halostachys caspica and their antimicrobial and antioxidant activities

Seven flavonoids have been isolated from the aerial parts of Halostachys caspica C. A. Mey. (Chenopodiaceae) for the first time. By means of physicochemical and spectrometric analysis, they were identified as luteolin (1), chrysin (2), chrysin 7-O-β-D-glucopyranoside (3), quercetin (4), quercetin 3-O-β-D-glucopyranoside (5), isorhamentin-3-O-β-D-glucopyranoside (6), and isorhamentin-3-O-β-D-rutinoside (7). All flavonoids were evaluated to show a broad antimicrobial spectrum of activity on microorganisms including seven bacterial and one fungal species as well as pronounced antioxidant activity. Among them, the aglycones with relatively low polarity had stronger bioactivity than their glycosides. The results suggested that the isolated flavonoids could be used for future development of antimicrobial and antioxidant agents, and also provided additional data for supporting the use of H. caspica as forage.     

Transition metal-catalyzed regio- and stereoselective aminobromination of olefins with TsNH2 and NBS as nitrogen and bromine sources

[reaction: see text] A new synthetic procedure for aminohalogenation of olefins has been developed for the preparation of vicinal haloamine derivatives in high yields by using Cu, Mn, or V catalysts with p-toluenesulfonamide (TsNH(2)) and N-bromosuccinimide (NBS) as nitrogen and bromine sources, respectively. Unprecedented regio- and stereoselectivity (anti:syn > 99:1) toward the aminohalogenation process is shown for olefinic substrates as well as transition metal catalysts.     

Synthesis and characterization of star-comb polybutadiene and poly(ethylene-co-butene)

<正>A novel star-comb polybutadiene(SC-PB) was synthesized with n-butyllithium(n-BuLi) as initiator,epoxidized star liquid polybutadiene(ESPB) as coupling agent,cyclohexane as solvent by living anionic polymerization and grafting-onto technology. The SC-PB was subsequently hydrogenated by homogeneous catalysis(catalytic hydrogenation using nickel naphthenate/ triisobutyl aluminum),to transform the SC-PB into the corresponding star-comb poly(ethylene-co-butene)(SC-PEB).The SC-PB was characterized by SEC-TALLS,~1H NMR,DSC and WAXD techniques.The hydrogenation degree and crystallinity degree of SC-PEB were also determined.     

Vitrification of Cs and Sr loaded Iranian natural and synthetic zeolites

Summary This study deals with the treatment of Cs⁺and Sr²⁺by using natural clinoptilolite from Ardakan region (Yazd province) of Iran and its relevant zeolite P as well as the vitrification process for immobilizing the Cs and Sr radionuclides in borosilicate glass matrices. The evaluation of various samples was carried out using X-ray techniques (XRF, XRD) as well as atomic absorption spectroscopy (AAS) for leaching experiments.     

Synthesis and Surface Properties of N-Alkyl-N-methylgluconamides and N-Alkyl-N-methyllactobionamides

Three series of nonionic N-alkylaldonamides, N-alkyl-N-methylgluconamides (Cn-MGA, Cn: n-C(10)H(21), n-C(12)H(25), n-C(14)H(29), n-C(16)H(33), and n-C(18)H(37)), N-alkyl-N-methyllactobionamides (Cn-MLA, alkyl as above-mentioned), and N-oleyl-N-methylglucon/lactobionamide, were synthesized in the reaction of an appropriate N-alkyl-N-methylamine with delta-D-glucolactone and lactobionic acid, respectively. Krafft temperatures of aqueous solutions and surface properties of these surfactants at 20 degrees C, i.e., surface excess concentration, Gamma(cmc), surface area demand per molecule, A(min), efficiency in surface tension reduction, pC(20), effectiveness in surface tension reduction, Pi(cmc), critical micelle concentration, CMC, and CMC/C(20) parameter as well as standard free energies of adsorption, DeltaG degrees (ads), and of micellization, DeltaG degrees (mic), were determined. It was shown that introduction of the methyl group to the amide nitrogen increased the solubility of the surfactants, which was confirmed by their Krafft temperatures. Lactobionamides are more water soluble than gluconamides. On the other hand, the Cn-MGA surfactants are more surface active than the respective Cn-MLA ones. This observation is based on the determined adsorption and micellization parameters. The presence of one double bond in a hydrocarbon chain as in oleyl-amides increases their hydrophilic character compared with that of saturated C18 derivatives. No distinct differences were observed between the A(min) values obtained for both series studied, although they differ markedly in the size of the hydrophilic groups. Copyright 2001 Academic Press.     

Alkaloids of and ( )

and provided a variety of and alkaloids as well as novel ring-opened indole alkaloids including leuconolam (6), rhazinilam (8) and 5,21-dihydrorhazinilam (9). Facile acid and base reactions of leuconolam lead to ring reclosure products. Physical and spectral data of norfluorocurarine ( ), norfluorocurarine-N_b-oxide ( ), eburnamine (2), kopsinine (5) and epileuconolam (7) as well as some derivatives of leuconolam are also provided.     

Authentication and chemical study of isodonis herba and isodonis extracts

Isodonis Herba is used as a Japanese dietary supplement and folk medicine. The extract of the herb (Isodonis extract) is also used as a food additive whose major compound is enmein (1). Here we compared internal transcribed spacer sequences of nuclear ribosomal DNA from Isodonis Herba available on the Japanese and Chinese crude drug markets, and found that the former derived from Isodon japonicus and Isodon trichocarpus, while the latter derived from distinct species such as Isodon eriocalyx. The liquid chromatography/mass spectrometry profiles of Isodonis Herba were classified into four chemotypes (A to D) according to the ratio of the major constituents. Types B and C contained 1 and oridonin (2) as major components, respectively. An intermediate (or mixed) form of types B and C in various ratios was designed type A. Type D contained eriocalyxin B (3) as its major component. Japanese herba were types A-C, while Chinese herba were types C and D. The commercial Isodonis extract products tested were classified as type D, suggesting that they originated from Chinese Herba. Understanding the relationship between extract constituents and DNA profiles is important for the official specification of dietary supplements and food additives of plant origin.     

Determination of lanthanides and yttrium in rocks and minerals by atomic-absorption and flame-emission spectrometry

The sensitivity of atomic-absorption and flame-emission determination of lanthanides and yttrium is improved by a factor of 2-5 when an absolute ethanol solution of the perchlorate of the metal (instead of an aqueous solution) is aspirated into a nitrous oxide-acetylene flame. Based on this, a method has been developed for accurate determination of small amounts of certain rare earths and yttrium. Lanthanum (1%) is used as a spectroscopic buffer to eliminate interferences and to enhance the sensitivities in certain determinations. Where the use of lanthanum is not practicable because of interferences (such as in the determination of praseodymium and samarium by flame emission), sodium (2000 ppm) is used as the spectroscopic buffer. Studies with synthetic solutions indicate that yttrium and most lanthanides can be directly determined in minerals without any chemical separation. With rock samples it is necessary to preconcentrate the traces of the rare earths by fluoride or oxalate precipitation with calcium as the carrier, followed by removal of calcium by hydroxide precipitation using mg amounts of iron as the carrier. The method developed has been applied to the determination of certain lanthanides and yttrium in a variety of rocks, including the Canadian reference rocks, syenites SY-1, SY-2 and SY-3, and some minerals such as britholite, cenosite, chevkinite, allanite, apatite and sphene.     

Assemblies of dendrimers and proteins on carbon and gold electrodes

Dendritic macromolecules of two adjacent (G3.5 and G4) generations have been used to modify gold or carbon electrodes. The structure and stability of deposited films have been explored by quartz crystal microbalance (QCM), Surface Plasma Resonance (SPR) and electrochemistry. Dendrimers have been shown to adsorb spontaneously on electrode materials as compressed macromolecular films. They are able to inhibit (G3.5) or promote (G4) electroactive anionic species such as Fe(CN)(6)(3-/4-) used as a probe system. Mixed protein/dendrimer assemblies have been constructed with proteins differing in charge, nature of the prosthetic groups and sizes such as lysozyme, cytochrome c, polyhemic cytochrome c(3) or glucose oxidase. Generally, the stability of adsorbed films seems to be limited to one dendrimer/protein bilayer. Owing to the satisfactory stability of composite cytochrome c(3)/G3.5 or glucose oxidase/G4 films, biosensing applications are described for metal bioremediation and glucose detection, respectively.     

纳米阵列电极研究*

纳米阵列电极作为一种人工组装的纳米结构体系,具有高传质速率、低双电层充电电流、小时间常数、小IR降及高信噪比、可操作性强和测量灵敏度高等优势,因而在电化学理论研究、生物传感器、电催化材料和高能化学电源电极材料等方面等具有广阔的应用前景。迄今为止,人们采用多种材料设计制备出包括圆盘状、圆柱形、球形、圆锥形、叉指状和井状等各种形状的纳米阵列电极。其制作方法主要包括模板法、刻蚀法和自组装法等,电极的表征主要采用电子显微镜技术和电化学方法。本文结合我们的工作和国内外文献,就纳米阵列电极制作方法、表征和应用等方面进行了评述,并对目前纳米阵列电极研究中存在的问题及发展前景进行了探讨和展望。