|
| ||
|
|
||
Acetonitrile Solution (acetonitrile + solution)
Selected AbstractsPhotosensitizing Properties of Triplet ,-Lapachones in Acetonitrile SolutionPHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2009José Carlos Netto-Ferreira The photochemical reactivity of ,-lapachone (1), nor -,-lapachone (2) and 1,2-naphthoquinone (3) towards amino acids and nucleobases or nucleosides has been examined employing the nanosecond laser flash photolysis technique. Excitation (, = 355 nm) of degassed solutions of 1,3, in acetonitrile, resulted in the formation of their corresponding triplet excited states. These transients were efficiently quenched by l -tryptophan, l -tryptophan methyl ester, l -tyrosine, l -tyrosine methyl ester and l -cysteine (kq , 109 L mol,1 s,1). For l -tryptophan, l -tyrosine and their methyl esters new transients were formed in the quenching process, which were assigned to the corresponding radical pair resulting from an initial electron transfer from the amino acids or their esters to the excited quinone, followed by a fast proton transfer. No measurable quenching rate constants could be observed in the presence of thymine and thymidine. On the other hand, efficient rate constants were obtained when 1,3 were quenched by 2,-deoxyguanosine (kq , 109 L mol,1 s,1). The quantum efficiency of singlet oxygen (1O2) formation from 1 to 3 was determined employing time-resolved near-IR emission studies upon laser excitation and showed considerably high values in all cases (,, = 0.6), which are fully in accord with the ,,* character of these triplets in acetonitrile. [source] Highly Selective and Sensitive Tin(II) Membrane Electrode Based on a New Synthesized Schiff's BaseELECTROANALYSIS, Issue 7 2009Morteza Hosseini Abstract Studies on complex formation of tris(3-(2-hydroxybenzophenone)propyl)amine (THPA) with a number of metal ions in acetonitrile solution revealed the occurrence of a selective 1,:,1 complexation of the proposed ligand with Sn2+ ion. Consequently, THPA was used as a suitable neutral ionophore for the preparation of a polymeric membrane-selective electrode. The electrode exhibits a Nernstian behavior with a slope of 29.4±0.3,mV per decade and a detection limit of 2.0×10,7 M. It also showed a good selectivity for Sn2+ ions in comparison with some of group A and B metal ions over a wide concentration range of 5.0×10,7,1.0×10,1 M. Improved selectivity was achieved compared to the best selectivity recently reported by other authors for tin(II). The electrode was successfully applied to the determination of Sn2+ ion in waste water and various canned products. [source] Synthesis and Characterization of a Series of New Luminescent NHC-Coordinated AuI,AgI Tetra- and Polymetallic Complexes Containing Benzoate-Bridged Ag2 DimersEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2009Amit K. Ghosh Abstract The reaction of [Au(CH3impy)2]PF6 (2), with substituted silver benzoate salts bearing different halide substituents produced a series of new mixed-metal species having two different structural motifs. One structural motif contains discrete tetrametallic Ag2Au2 diamond cores, whereas the other motif contains the same tetrametallic diamond core interconnected by benzoate-bridged silver dimers to form polymers. All the complexes are substitution-inert and stable both in the solid state as well as in solution. We also report the synthesis of oxidative addition products of [Au(CH3impy)2]PF6, which were also obtained during our attempts to oxidize the above-mentioned multimetallic assembly with bromine and iodine. Compounds 3,7 are intensely luminescent in frozen acetonitrile solution, but surprisingly no luminescence is observed at room temperature. All the complexes were completely characterized by 1H, 13C NMR, electronic absorption, emission spectroscopy, elemental analysis and X-ray crystallography. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Solid-State and Solution Structure of Lanthanide(III) Complexes with a Flexible Py-N6 Macrocyclic LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2009Cristina Núñez Abstract Lanthanide complexes of a hexaaza macrocyclic ligand containing a pyridine head unit (L) were synthesized (Ln = La,Lu, except Pm). The solid-state structures of the corresponding La, Ce, Pr, Nd, and Lu complexes were determined by single-crystal X-ray crystallography, and they reveal the presence of three different mononuclear complexes with three different conformations of the macrocycle and coordination environments around the metal ions. In all complexes the lanthanide ion is coordinated in an endomacrocyclic manner to the six nitrogen donor atoms of the ligand. In the La, Ce, and Pr complexes the metal ions show a 12-coordinate mononuclear environment in which 3 nitrate anions coordinate in a bidentate fashion. However, in the Nd analogue the metal ion displays a 10-coordinated environment with the coordination of 2 bidentate nitrate groups, whereas Lu shows a 9-coordinate environment interacting with 2 nitrate ligands, one of them acting as bidentate and the second one coordinating in a monodentate fashion. The 1H and 13C NMR spectra of the complexes recorded in CD3CN suggest that the complexes adopt in solution a similar structure to that observed for the Nd complex in the solid state. The [Ln(L)(NO3)3] and [Ln(L)(NO3)2]+ complexes were characterized by density functional theory (DFT) calculations (B3LYP model). The structures obtained from these calculations for La, Ce, Pr, and Nd are in good agreement with the experimental solid-state structures. The relative stabilities of the [Ln(L)(NO3)2]+ complexes with respect to the [Ln(L)(NO3)3] ones (Ln = La, Nd, Gd, Ho, or Lu) were studied both in vacuo and in acetonitrile solution (PCM model) at the same computational level. Our calculations indicate that in solution the [Ln(L)(NO3)2]+ species is the most stable one along the whole lanthanide series, in agreement with the NMR spectroscopic data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Metal Ion Complementarity: Effect of Ring-Size Variation on the Conformation and Stability of Lead(II) and Cadmium(II) Complexes with Pendant-Armed CrownsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 15 2007Martín Regueiro-Figueroa Abstract The binding tendencies of the pendant-armed crown ethers L1,L3 [L1 = N,N, -bis(benzimidazol-2-ylmethyl)-1,7-diaza-12-crown-4, L2 = N,N, -bis(benzimidazol-2-ylmethyl)-1,10-diaza-15-crown-5) and L3 = N,N, -bis(benzimidazol-2-ylmethyl)-4,13-diaza-18-crown-6] towards PbII and CdII have been investigated. The X-ray crystal structure of [Cd(L3)](ClO4)2·EtOH shows that, in the solid state, the CdII ion is eight-coordinate and fits quite well into the crown hole, favouring an anti arrangement of the organic receptor. NMR measurements recorded in acetonitrile solution indicate that increasing the crown size induces a conformational change in the series of CdII complexes. The conformation goes from a syn arrangement for L1 to an anti arrangement for L3, passing through a syn [lrarr2] anti equilibrium in the complex derived from L2. On the contrary, no conformational change was observed for the corresponding PbII complexes, which have a syn conformation in all cases. These results have been confirmed by means of density functional theory (DFT) calculations performed by using the B3LYP model. The binding constants obtained from UV/Vis titration experiments in DMSO solution demonstrate that a decrease in the crown size provokes a 102 -fold enhancement of the stability for this series of CdII complexes, whereas for PbII a gradual decrease of the binding constants is observed. Receptor L1 shows a certain degree of selectivity for CdII over PbII, with a selectivity factor > 102. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Receptor versus Counterion: Capability of N,N, -Bis(2-aminobenzyl)-diazacrowns for Giving Endo- and/or Exocyclic Coordination of ZnIIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 13 2007Lea Vaiana Abstract The structure of ZnII complexes with receptors L1 and L2[L1 = N,N, -bis(2-aminobenzyl)-1,10-diaza-15-crown-5 and L2 = N,N, -bis(2-aminobenzyl)-4,13-diaza-18-crown-6] was studied both in the solid state and in acetonitrile solution. Both receptors form mononuclear ZnII complexes in this solvent, while no evidence for the formation of dinuclear complexes was obtained. This is in contrast with previous investigations that demonstrated the formation of dinuclear complexes of L2 with first-row transition metals such as NiII, CoII and CuII. Compounds of formula [Zn(L1)](ClO4)2 (1), [Zn(L1)](NO3)2·2CH3CN (2), [Zn(L2)](ClO4)2 (3) and [Zn(L2)(NO3)2] (4) were isolated and structurally characterised by X-ray diffraction analyses. L1 forms seven-coordinate ZnII complexes in the presence of both nitrate and perchlorate anions, as a consequence of the good fit between the macrocyclic cavity and the ionic radius of the metal ion. The ZnII ion is deeply buried into the receptor cavity and the anions are forced to remain out of the metal coordination sphere. The cation [Zn(L1)]2+ present in 1 and 2 is one of the very few examples of seven-coordinate Zn complexes. Receptor L2 provides a very rare example of a macrocyclic receptor allowing endocyclic and exocyclic coordination on the same guest cation, depending on the nature of the anion present. Thus, in 3 the ZnII ion is endocyclically coordinated, placed inside the crown hole coordinated to four donor atoms of the ligand in a distorted tetrahedral environment, whereas in 4, the presence of a strongly coordinating anion such as nitrate results in an exocyclic coordination of ZnII, which is directly bound only to the two primarily amine groups of L2 and two nitrate ligands. Spectrophotometric titrations of [Zn(L2)]2+ with tetrabutylammonium nitrate in acetonitrile solution demonstrate the stepwise formation of 1:1 and 1:2 adducts with this anion in acetonitrile solution. The [Zn(L1)]2+, [Zn(L2)]2+ and [Zn(L2)(NO3)2] systems were characterised by means of DFT calculations (B3LYP model). The calculated geometries show an excellent agreement with the experimental structures obtained from X-ray diffraction analyses. Calculated binding energies of the macrocyclic ligands to ZnII are also consistent with the experimental data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Non-Covalent Aggregation of Discrete Metallo-Supramolecular Helicates into Higher Assemblies by Aromatic Pathways: Structural and Chemical Studies of New Aniline-Based Neutral Metal(II) DihelicatesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 17 2005Miguel Vázquez Abstract Neutral manganese(II), iron(II), cobalt(II), nickel(II), zinc(II) and cadmium(II) complexes with an N -tosyl-substituted N4 -donor Schiff base containing a 4,4'-methylenedianiline residue as spacer [H2La: N,N' -bis(2-tosylaminobenzylidene)-4,4'-methylenedianiline], and the zinc(II) complex with an analogous ligand [H2Lb: N,N' -bis(2-tosylaminobenzylidene)-4,4'-oxodianiline] have been prepared by an electrochemical procedure. FAB and ESI mass spectra of the complexes show peaks due to species corresponding to a general formula [M2(La,b)2 + H]+, thereby suggesting their dinuclear nature. A detailed study of the crystal packing in the unit cell of the zinc(II) complex with H2La shows that the helicates aggregate to form discrete prismatic moieties containing three molecules held together by ,,, and ,,, interactions. Moreover, the ZnII neutral dihelicate with H2Lb forms a 3D network in the solid state due to intermolecular ,-stacking interactions. 1H NMR studies of the diamagnetic compounds reported herein have been performed. Finally, the ligand H2La and its ZnII and CdII complexes have been studied by spectrophotometric and spectrofluorimetric techniques in order to get a better understanding of the formation mechanisms of the complexes and of the nature of their fluorescence emission. Emission studies show that the ZnII and CdII dihelicates with H2La display a green fluorescence in acetonitrile solution (, = 473 nm, , = 0.03 and , = 476 nm, , = 0.01, respectively). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Kinetic and Thermodynamic Studies of the Disproportionation of Hydrogen Peroxide by Dimanganese(ii,ii) and -(ii,iii) Complexes of a Bridging Phenolate LigandEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2005Lionel Dubois Abstract The dimanganese(ii,ii) complexes [Mn2(L)(OAc)2(CH3OH)]-(ClO4) (1a) and [Mn2(L)(OBz)2(H2O)](ClO4) (1b) as well as the dimanganese(ii,iii) complex [Mn2(L)(OAc)2(CH3OH)]-(ClO4)2 (2a), where HL is the asymmetric phenol ligand2-[bis(2-pyridylmethyl)aminomethyl]-6-{[(benzyl)(2-pyridyl-methyl)amino]methyl}-4-methylphenol, react with hydrogen peroxide in acetonitrile solution. The initial reaction rates and their temperature and acid/base dependencies were investigated by monitoring the dioxygen evolution. These studies revealed a first-order dependence on both the catalyst and H2O2 and a strong influence of the carboxylate. Electrospray ionisation mass spectrometry as well as EPR and UV/Vis spectroscopy were used to monitor the reaction catalysed by 2a. The same bis(,-oxo)dimanganese(III,IV) and (,-oxo)dimanganese(ii,iii) active species as found for 1a were detected in the catalytic medium. The EPR spectra recorded during the catalase-like reaction revealed the accumulation of the magnetically uncoupled dimanganese(ii,iii) precursor of the active bis(,-oxo)dimanganese(III,IV) species which dominates the spectra in the case of 1a. This difference can be attributed to the different pH conditions generated by the reaction and reflects differences in the initiation phases for the two catalysts. Overall, the kinetic and thermodynamic studies of H2O2 disproportionation by these dimanganese complexes are fully consistent with the mechanism deduced from our previous extensive spectroscopic studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Simplified synthesis of 1,1,[14C]-methylene-di (2-naphthol).JOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 9 2004A radiochemical, kinetic approach Abstract The synthesis of the 1,1,[14C]-methylene-di-(2-naphthol) 2, as the radiolabeled probe of a possible interaction between the , -amyloid fibrils and the di-naphthol mojety in the Alzheimer's disease, is reported. Very simple radiochemical procedure, starting from [14C]paraformaldehyde, produced 8.66 MBq of compound 2 at the specific radioactivity of 1.22 TBq/mol. A mechanistic and kinetic approach allowed the comprehension of the right experimental conditions. The stability of compound 2 in acetonitrile solution was investigated, denoting a significative decomposition process through the transient formation of the 1,2-naphthyne intermediate. Copyright © 2004 John Wiley & Sons, Ltd. [source] Substituent effects in reductions of heteroaromatic cationsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 10 2002David Heyes Abstract A set of 11 each of 2,4,6-triphenylpyrylium, -thiopyrylium and - N -methylpyridinium tetrafluoroborates carrying a range of substituents in the phenyl rings were prepared. First and second wave reduction potentials were determined. For the thiopyrylium series there are linear correlations between scaled potentials (E°/0.05915) and summed Hammett constants for substituents in the pendant phenyl groups (,,=,2.29 and 3.38 for first and second waves respectively). For the pyrylium series, a good linear relationship (,,=,2.79) is obtained for all substituent patterns for the first wave reduction potentials, but for the second wave there are separate correlations for salts carrying substituents in the 4-phenyl and for those carrying substituents in 2- and 6-phenyls. For the pyridinium series, the first wave potentials show separate correlations for salts carrying substituents in the 4-phenyl and for those carrying substituents in 2-and 6-phenyls, but a single linear relationship for the second wave potentials. These are related to particular structural features in the cations, radicals and anions in each series. Rates and products were determined for reductions of the pyrylium and thiopyrylium cations by sodium cyanoborohydride and of all cations by sodium borohydride in acetonitrile solution. Reactions are first order in reducing agent and cation. Primary kinetic isotope effects were determined for borohydride reduction of the least reactive of each of the series of cations. Plots of logarithms of second-order rate constants against summed Hammett constants for substituents in the pendant phenyl groups are linear for all combinations of reagent and cation with 0.91 < , < 1.50 across all substituent patterns. For parent pyrylium and thiopyryliums, kBH4/kCNBH3,=,8.4,×,104 and 1.5,×,104, respectively, and for reductions by borohydride the reactivities of the pyrylium, thiopyrylium and pyridinium, series decrease in the order 1.4,×,105:8.8,×,103:1. Constant selectivities are not observed. Comparison of the correlations for electrochemical reduction and for hydride addition leads to the conclusion that charge neutralization in the hydride addition transition states runs ahead of bonding changes at the originating B,H bond. Copyright © 2002 John Wiley & Sons, Ltd. [source] Highly stable electrochromic polyamides based on N,N -bis(4-aminophenyl)- N,,N,-bis(4- tert -butylphenyl)-1,4-phenylenediamineJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 9 2009Sheng-Huei Hsiao Abstract A new triphenylamine-containing aromatic diamine monomer, N,N -bis(4-aminophenyl)- N,,N,-bis(4- tert -butylphenyl)-1,4-phenylenediamine, was synthesized by an established synthetic procedure from readily available reagents. A novel family of electroactive polyamides with di- tert -butyl-substituted N,N,N,,N,-tetraphenyl-1,4-phenylenediamine units were prepared via the phosphorylation polyamidation reactions of the newly synthesized diamine monomer with various aromatic or aliphatic dicarboxylic acids. All the polymers were amorphous with good solubility in many organic solvents, such as N -methyl-2-pyrrolidinone (NMP) and N,N -dimethylacetamide, and could be solution-cast into tough and flexible polymer films. The polyamides derived from aromatic dicarboxylic acids had useful levels of thermal stability, with glass-transition temperatures of 269,296 °C, 10% weight-loss temperatures in excess of 544 °C, and char yields at 800 °C in nitrogen higher than 62%. The dilute solutions of these polyamides in NMP exhibited strong absorption bands centered at 316,342 nm and photoluminescence maxima around 362,465 nm in the violet-blue region. The polyamides derived from aliphatic dicarboxylic acids were optically transparent in the visible region and fluoresced with a higher quantum yield compared with those derived from aromatic dicarboxylic acids. The hole-transporting and electrochromic properties were examined by electrochemical and spectro-electrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium-tin oxide-coated glass substrate exhibited two reversible oxidation redox couples at 0.57,0.60 V and 0.95,0.98 V versus Ag/AgCl in acetonitrile solution. The polyamide films revealed excellent elcterochemical and electrochromic stability, with a color change from a colorless or pale yellowish neutral form to green and blue oxidized forms at applied potentials ranging from 0.0 to 1.2 V. These anodically coloring polymeric materials showed interesting electrochromic properties, such as high coloration efficiency (CE = 216 cm2/C for the green coloring) and high contrast ratio of optical transmittance change (,T%) up to 64% at 424 nm and 59% at 983 nm for the green coloration, and 90% at 778 nm for the blue coloration. The electroactivity of the polymer remains intact even after cycling 500 times between its neutral and fully oxidized states. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2330,2343, 2009 [source] Synthesis, photoluminescence, and electrochromic properties of wholly aromatic polyamides bearing naphthylamine chromophoresJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 20 2006Guey-Sheng Liou Abstract A series of novel polyamides with pendent naphthylamine units having inherent viscosities of 0.15,1.02 dL/g were prepared via direct phosphorylation polycondensation from various diamines and a naphthylamine-based aromatic dicarboxylic acid, 1-[N,N -di(4-carboxyphenyl)amino]naphthalene. These amorphous polyamides were readily soluble in various organic solvents and could be cast into transparent and tough films. The aromatic polyamides had useful levels of thermal stability associated with high glass-transition temperatures (268,355 °C), 10% weight loss temperatures in excess of 480 °C, and char yields at 800 °C in nitrogen higher than 60%. These polymers showed maximum ultraviolet,visible absorption at 350,358 nm and exhibited fluorescence emission maxima around 435,458 nm in N -methyl-2-pyrrolidinone solutions with fluorescence quantum yields ranging from 0.4 to 15.0%. The hole-transporting and electrochromic properties were examined with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyamide films cast onto an indium tin oxide coated glass substrate exhibited one oxidative redox couple around 1.08,1.16 V (oxidation onset potential) versus Ag/AgCl in an acetonitrile solution and revealed good stability of the electrochromic characteristics, with a color change from colorless to green at applied potentials ranging from 0 to 1.6 V. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6094,6102, 2006 [source] Novel aromatic polyamides and polyimides functionalized with 4- tert -butyltriphenylamine groupsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2006Sheng-Huei Hsiao Abstract A new triphenylamine-containing diamine monomer, 4,4,-diamino-4,- tert -butyltriphenylamine, was successfully synthesized by the cesium fluoride-mediated N,N -diarylation of 4- tert -butylaniline with 4-fluoronitrobenzene, followed by the reduction of the nitro group. The obtained diamine monomer was reacted with various aromatic dicarboxylic acids and tetracarboxylic dianhydrides to produce two series of novel triphenylamine-based polyamides and polyimides with pendent tert -butyl substituents. Most of the polymers were readily soluble in polar organic solvents, such as N -methyl-2-pyrrolidone and N,N -dimethylacetamide (DMAc), and could be solution cast into tough and flexible polymer films. These polymers showed high glass transition temperatures between 282 and 320 °C, and they were fairly stable up to a temperature above 450 °C (for polyamides) or 500 °C (for polyimides). These polymers exhibited UV absorption maxima around 308 to 361 nm. The photoluminescence spectra of the polyamides in DMAc exhibited a peak emission wavelength in the blue at 421,433 nm. Cyclic voltammograms of polyamides and polyimides showed an oxidation wave at 1.0,1.1 V versus Ag/AgCl in an acetonitrile solution. All the polyamides and polyimides exhibited excellent reversibility of electrochromic characteristics by continuous several cyclic scans between 0.0 and 1.1,1.3 V, with a color change from the original pale yellowish neutral form to the green or blue oxidized forms. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4579,4592, 2006 [source] Novel thermally stable poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s for luminescent and electrochromic materialsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 15 2005Guey-Sheng Liou Abstract We describe the preparation, characterization, and luminescence of four novel electrochromic aromatic poly(amine hydrazide)s containing main-chain triphenylamine units with or without a para-substituted N,N -diphenylamino group on the pendent phenyl ring. These polymers were prepared from either 4,4,-dicarboxy-4,- N,N -diphenylaminotriphenylamine or 4,4,-dicarboxytriphenylamine and the respective aromatic dihydrazide monomers via a direct phosphorylation polycondensation reaction. All the poly(amine hydrazide)s were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent and flexible films with good mechanical properties. These poly(amine hydrazide)s exhibited strong ultraviolet,visible absorption bands at 346,348 nm in N -methyl-2-pyrrolidone (NMP) solutions. Their photoluminescence spectra in NMP solutions or as cast films showed maximum bands around 508,544 and 448,487 nm in the green and blue region for the two series of polymers. The hole-transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. All obtained poly(amine hydrazide)s and poly(amine-1,3,4-oxadiazole)s exhibited two reversible oxidation redox couples at 0.8 and 1.24 V vs. Ag/AgCl in acetonitrile solution and revealed excellent stability of electrochromic characteristics, changing color from original pale yellow to green and then to blue at electrode potentials of 0.87 and 1.24 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 3245,3256, 2005 [source] Novel family of triphenylamine-containing, hole-transporting, amorphous, aromatic polyamides with stable electrochromic propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2005Tzy-Hsiang Su Abstract We report the preparation and characterization of a series of novel electrochromic, aromatic poly(amine amide)s with pendent triphenylamine units. The synthesis proceeded via direct phosphorylation polycondensation between a novel diamine, N,N -bis(4-aminophenyl)- N,,N,-diphenyl-1,4-phenylenediamine, and various aromatic dicarboxylic acids. All the poly(amine amide)s were amorphous and readily soluble in many common organic solvents and could be solution-cast into transparent, tough, and flexible films with good mechanical properties. They exhibited good thermal stability and 10% weight-loss temperatures above 540 °C. Their glass-transition temperatures were 263,290 °C. These polymers in N -methyl-2-pyrrolidinone solutions exhibited strong ultraviolet,visible absorption peaks at 307,358 nm and photoluminescence peaks around 532,590 nm in the green region. The hole-transporting and electrochromic properties were studied with electrochemical and spectroelectrochemical methods. Cyclic voltammograms of poly(amine amide) films prepared by the casting of polymer solutions onto an indium tin oxide coated glass substrate exhibited two reversible oxidation redox couples at 0.65 and 1.03 V versus Ag/AgCl in an acetonitrile solution. All the poly(amine amide)s showed excellent stability with respect to their electrochromic characteristics; the color of the films changed from pale yellow to green and then blue at 0.85 and 1.25 V, respectively. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 2085,2098, 2005 [source] Evaluation of sulfobetaine-type polymer resin as an SPE adsorbent in the analysis of trace tetracycline antibiotics in honeyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 21 2009Tomoyasu Tsukamoto Abstract A new sulfobetaine polymer resin SPE method combined with HPLC-MS/MS for the determination of tetracycline (TC) antibiotics residues from honey samples is presented. The sulfobetaine resin was synthesized and was packed into a syringe-type tube, which served as the SPE cartridge for selective adsorption of TCs. TCs were quantitatively adsorbed on the sulfobetaine cartridge, when the loading solvent was 95%,v/v acetonitrile solution, and TCs adsorbed were not eluted by aqueous acetonitrile washing solution. TFA aqueous solution was used for eluting the adsorbed TCs. The proposed SPE method has been applied to the determination of TCs in honey samples. The recoveries of TCs spiked in honey samples ranged from 70 to 80%. Reduction of the recoveries might be derived from low solubility of TCs in acetonitrile. Compared with other SPE resins, this resin was superior in terms of selectivity with simple pretreatment. [source] Cathodic electrochemiluminescence of acetonitrile, acetonitrile,1,10-phenanthroline and acetonitrile,ternary Eu(III) complexes at a gold electrodeLUMINESCENCE: THE JOURNAL OF BIOLOGICAL AND CHEMICAL LUMINESCENCE, Issue 2 2006Hong-Xiao Yu Abstract Cathodic electrochemiluminescence (ECL) behaviours of the acetonitrile, acetonitrile,1,10-phenanthroline (phen) and acetonitrile,ternary Eu(III) complex systems at a gold electrode were studied. One very weak cathodic ECL-2 at ,3.5 V was observed in 0.1 mol/L tetrabutylammonium tetrafluoroborate (TBABF4) acetonitrile solution. When 10 mmol/L tetrabutylammonium peroxydisulphate [(TBA)2S2O8] was added to 0.1 mol/L TBABF4 acetonitrile solution, another cathodic ECL-1 at ,2.7 V appeared and the potential for ECL-2 was shifted from ,3.5 to ,3.1 V. Furthermore, ECL-2 intensity was enhanced about 20-fold. When 1 × 10,4 mol/L phen was added to 0.1 mol/L TBABF4 + 10 mmol/L (TBA)2S2O8 acetonitrile solution, the ECL intensities of ECL-1 and ECL-2 were enhanced about 20-fold compared with those of 0.1 mol/L TBABF4 + 10 mmol/L (TBA)2S2O8 acetonitrile solution. The maximum emission peaks of ECL-1 and ECL-2 in the three systems mentioned above appeared at about 530 nm. The products obtained by electrolysing 0.1 mol/L TBABF4 acetonitrile solution at ,3.5 V for 20 min were analysed by Fourier Transform Infrared (FTIR) spectra and gas chromatography,mass spectrometry (GC,MS) and the emitter of ECL-1 and ECL-2 was identified as excited state polyacetonitrile. When ternary Eu(III) complexes were presented in 0.1 mol/L TBABF4 + 10 mmol/L (TBA)2S2O8 acetonitrile solution, another maximum emission peak with a narrow band centred at about 610 nm appeared in ECL-1 in addition to the maximum emission peaks at about 530 nm for ECL-1 and ECL-2. The emitter of ECL emission at 610 nm was identified as the excited states Eu(III)*. The mechanisms for cathodic ECL behaviours of the acetonitrile, acetonitrile,phen and acetonitrile,ternary Eu(III) complex systems at a gold electrode have been proposed. The extremely sharp emission bands for ternary Eu(III) complexes may have analytical potential. Copyright © 2006 John Wiley & Sons, Ltd. [source] Powder X-ray studies of meso -hexamethyl propylene amine oxime (meso -HMPAO) in two different phasesACTA CRYSTALLOGRAPHICA SECTION C, Issue 9 2010Mahmoud Al-Ktaifani Two different forms of meso -3,3,-[2,2-dimethylpropane-1,3-diylbis(azanediyl)]dibutan-2-one dioxime, commonly called meso -hexamethyl propylene amine oxime (HMPAO), C13H28N4O2, designated , and ,, were isolated by fractional crystallization and their crystal structures were determined by powder X-ray diffraction using the direct-space method with the parallel tempering algorithm. The , form was first crystallized from acetonitrile solution, while the , form was obtained by recrystallization of the , phase from diethyl ether. The , form crystallizes in the triclinic system (space group P), with one molecule in the asymmetric unit, while the crystal of the , form is monoclinic (space group P21/n), with one molecule in the asymmetric unit. In both phases, the molecules have similar conformations and RS/EE geometric isomerism. The crystal packing of the two phases is dominated by intermolecular hydrogen-bonding interactions between the two O,H oxime groups of an individual molecule and the amine N atoms of two different adjacent molecules, which lead to segregation of extended poly(meso -HMPAO) one-dimensional chains along the c direction. The structures of the two phases are primarily different due to the different orientations of the molecules in the chains. [source] Oxidation of alkanes and alcohols with hydrogen peroxide catalyzed by complex Os3(CO)10(µ-H)2,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6 2010Georgiy B. Shul'pin Abstract Trinuclear carbonyl hydride cluster, Os3(CO)10(µ-H)2, catalyzes oxidation of cyclooctane to cyclooctyl hydroperoxide by hydrogen peroxide in acetonitrile solution. The hydroperoxide partly decomposes in the course of the reaction to afford cyclooctanone and cyclooctanol. Selectivity parameters obtained in oxidations of various linear and branched alkanes as well as kinetic features of the reaction indicated that the alkane oxidation occurs with the participation of hydroxyl radicals. A similar mechanism operates in transformation of benzene into phenol and styrene into benzaldehyde. The system also oxidizes 1-phenylethanol to acetophenone. The kinetic study led to a conclusion that oxidation of alcohols does not involve hydroxyl radicals as main oxidizing species and apparently proceeds with the participation of osmyl species, ,OsO'. Copyright © 2010 John Wiley & Sons, Ltd. [source] [Pt(topy)(Htopy)(ONO2)] complex (Htopy = 2- p -tolylpyridine) and its analogs: 195Pt NMR spectra and fabrication of light-emitting devicesAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 4 2009Hiroto Fukuda Abstract We report fast, high-yield syntheses of a series of [Pt(C,N)(HC,N)X] complexes, where HC,N is 2-phenylpyridine (Hppy) or 2- p -tolylpyridine (Htopy) and X, is Cl,, Br,, I,, ONO2,, NO2, or SCN,. The structure of [Pt(topy)(Htopy)(ONO2)] was analyzed by single-crystal X-ray diffraction. Substitution of Cl, with Br, or I, in our complexes shifted the 195Pt NMR peaks upfield in the order Cl, < Br, < I,, but the magnitudes of their shifts were one-tenth those observed for non-cyclometalated platinum(II) complexes. As the two nitrato complexes showed strong emissions in acetonitrile solution,three to six times those of other complexes,they were used to fabricate OLEDs. Although their emissions were not particularly strong, devices fabricated with platinum(II) complexes containing bulky ligands emitted green light with a short lifetime (,). Copyright © 2009 John Wiley & Sons, Ltd. [source] Luminescence characteristics and X-ray crystal structure of [Cd(bipy)3][PF6]2 (bipy = 2,2,-bipyridine)APPLIED ORGANOMETALLIC CHEMISTRY, Issue 12 2005Nabanita Kundu Abstract The photoluminescence characteristics of the [Cd(bipy)3][PF6]2 complex are reported. A moderately large quantum yield (,) of 1.07 × 10,2 is exhibited in acetonitrile solution at 298 K. Crystallography shows the dication to have a distorted octahedral geometry and the crystal structure to be stabilized by CH···, and CH···F interactions. Copyright © 2005 John Wiley & Sons, Ltd. [source] Synthesis, structure and reactivity of cationic base-stabilized gallyleneiron complexes,APPLIED ORGANOMETALLIC CHEMISTRY, Issue 6-7 2003Keiji Ueno Abstract Addition of 2,2,-bipyridine (bpy) to an acetonitrile solution of dichlorogallyliron complex FpGaCl2 (1: Fp = (,-C5H5)Fe(CO)2) afforded almost quantitatively a salt consisting of a cationic base-stabilized gallylene complex [FpGaCl·bpy]+ ([3a]+) and an anionic complex [FpGaCl3], ([4],). Reaction of Fp,GaCl2 (Fp, = Fp (1), Fp* (2); Fp* = (,-C5Me5)Fe(CO)2) with NaBPh4 in the presence of a bidentate donor (Do2) gave [Fp,GaCl·Do2]BPh4 where Do2 was bpy or 1,10-phenanthroline (phen). These cationic complexes may be useful precursors for the synthesis of gallyleneiron complexes with various substituents on the gallium atom. Indeed, reaction of [Fp*GaCl·phen]BPh4 ([5b]BPh4) with NaSpTol or Me3SiSpTol afforded the gallyleneiron complex [Fp*GaSpTol·phen]BPh4 ([6]BPh4), the first example of a gallium,transition metal complex having a thiolate group on the gallium atom. The molecular structures of [5b]BPh4 and [6]BPh4 were determined by single crystal X-ray diffraction. Copyright © 2003 John Wiley & Sons, Ltd. [source] Development of a novel HPLC-MS/MS method for the determination of aconitine and its application to in vitro and rat microdialysis samplesBIOMEDICAL CHROMATOGRAPHY, Issue 7 2009Quan-long Zhang Abstract A sensitive and selective LC-MS/MS method was developed and validated for the determination of aconitine in microdialysate and rat plasma. Extraction of plasma sample was conducted by use of 1% trichloracetic acid and acetonitrile solution with 10 ng/mL internal standard (propafenone) spiked. Microdialysates were analyzed without sample purification. After sample preparation, 2 µL were injected and separated with an isocratic mobile phase consisting of acetonitrile:0.1% formic acid (60:40, v/v) at a flow rate of 0.3 mL/min. The Agilent G6410A triple quadrupole LC/MS system was operated under the multiple-reaction monitoring mode (MRM) using the electrospray ionization technique in positive mode. Overall, the assay exhibited good precision and accuracy. The diffusion properties of aconitine investigated in in vitro microdialysis experiments revealed unfavourable concentration dependence avertable by keeping a constant pH 5.77 using isotonic phosphate buffer solution as perfusate. The mean relative recoveries were 48.23% [coefficient of variation (CV 4.47%)] and 55.38% (CV 2.89%) for retrodialysis and recovery experiments, respectively. The in vivo recovery of aconitine was 34.48% (CV 3.05%) and was stable over the 6 h study period. Following characterization of aconitine both in vitro and in vivo microdialysis, the developed setting is suitable for application in pharmacokinetics and pharmacodynamics studies. Copyright © 2009 John Wiley & Sons, Ltd. [source] ChemInform Abstract: Synthesis of 9-Alkyl-6-amino[1,2,4]triazolo[3,4-c]-5-azaquinoxalines.CHEMINFORM, Issue 33 2010Effective SNAr Amination of Highly Electron-Poor Heterocycles. Abstract The previously reported substrates (I) readily undergo an SNAr reaction with ammonia in acetonitrile solution under thermal or microwave conditions. [source] A Novel Tripodal Ligand Containing Three Different N -Heterocyclic Donor Functions and Its Application in Catechol Dioxygenase MimickingCHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2009Marit Wagner Dipl.-Chem. Abstract Prominent donors: A pyridyl, an imidazolyl, and a pyrazolyl donor function are part of the novel tripodal ligand depicted, which thus combines three of the most prominent donors applied in ligands for bioinorganic chemistry within one coordination unit. To exploit its behaviour and potential, first investigations have been carried out in relation to catechol dioxygenase mimicry. We describe a novel chiral ligand, L, in which three different N -donor functions are linked to a methoxymethine unit: a methylpyrazole derivative, a methylimidazole unit, and a pyridyl residue. Complexes with FeCl2, FeBr2, and FeCl3 have been synthesized and fully characterized, including with respect to their molecular structures. While in combination with FeCl3L coordinates in a tripodal fashion, with FeX2 (X=Cl, Br) it binds only through two functions and the pyridyl unit remains dangling. For potential modelling of intradiol and extradiol catechol dioxygenase reactivity, the complexes [LFeCl2], 1, and [LFeCl3], 3, have been treated with 3,5-di- tert -butylcatechol, triethylamine, and O2. Both complexes yielded similar results in such investigations, since the LFeII,catecholate complex reacts with O2 through one-electron oxidation in the first step. Employing 3 in acetonitrile solution, intradiol cleavage occurred, although the undesired quinone was formed as the main product. If reagents were added (NaBPh4, H+) or reaction conditions were chosen (CH2Cl2 instead of CH3CN as the solvent) that made the coordination sphere at the iron centre more accessible for a third substrate donor function, an alternative reaction route, presumably involving O2 binding at the metal, became more important, which led to extradiol cleavage. In the extreme case (CH2Cl2 as the solvent and with the addition of NaBPh4), mainly the extradiol cleavage products were formed; the intradiol products were only observed as side products then and quinone formation became negligible. Protonated base functions in the second coordination sphere increased the efficiency of extradiol cleavage only slightly. The obtained results are in line with current understanding of the function of intradiol/extradiol dioxygenases. [source] Ground-State Equilibrium Thermodynamics and Switching Kinetics of Bistable [2]Rotaxanes Switched in Solution, Polymer Gels, and Molecular Electronic DevicesCHEMISTRY - A EUROPEAN JOURNAL, Issue 1 2006Jang Wook Choi Abstract We report on the kinetics and ground-state thermodynamics associated with electrochemically driven molecular mechanical switching of three bistable [2]rotaxanes in acetonitrile solution, polymer electrolyte gels, and molecular-switch tunnel junctions (MSTJs). For all rotaxanes a ,-electron-deficient cyclobis(paraquat- p -phenylene) (CBPQT4+) ring component encircles one of two recognition sites within a dumbbell component. Two rotaxanes (RATTF4+ and RTTF4+) contain tetrathiafulvalene (TTF) and 1,5-dioxynaphthalene (DNP) recognition units, but different hydrophilic stoppers. For these rotaxanes, the CBPQT4+ ring encircles predominantly (>90,%) the TTF unit at equilibrium, and this equilibrium is relatively temperature independent. In the third rotaxane (RBPTTF4+), the TTF unit is replaced by a ,-extended analogue (a bispyrrolotetrathiafulvalene (BPTTF) unit), and the CBPQT4+ ring encircles almost equally both recognition sites at equilibrium. This equilibrium exhibits strong temperature dependence. These thermodynamic differences were rationalized by reference to binding constants obtained by isothermal titration calorimetry for the complexation of model guests by the CBPQT4+ host in acetonitrile. For all bistable rotaxanes, oxidation of the TTF (BPTTF) unit is accompanied by movement of the CBPQT4+ ring to the DNP site. Reduction back to TTF0 (BPTTF0) is followed by relaxation to the equilibrium distribution of translational isomers. The relaxation kinetics are strongly environmentally dependent, yet consistent with a single electromechanical-switching mechanism in acetonitrile, polymer electrolyte gels, and MSTJs. The ground-state equilibrium properties of all three bistable [2]rotaxanes were reflective of molecular structure in all environments. These results provide direct evidence for the control by molecular structure of the electronic properties exhibited by the MSTJs. [source] Photoinduced Energy- and Electron-Transfer Processes in Dinuclear RuII,OsII, RuII,OsIII, and RuIII,OsII Trisbipyridine Complexes Containing a Shape-Persistent Macrocyclic SpacerCHEMPHYSCHEM, Issue 1 2006Margherita Venturi Prof. Abstract The PF6,salt of the dinuclear [(bpy)2Ru(1)Os(bpy)2]4+complex, where 1 is a phenylacetylene macrocycle which incorporates two 2,2,-bipyridine (bpy) chelating units in opposite sites of its shape-persistent structure, was prepared. In acetonitrile solution, the Ru- and Os-based units display their characteristic absorption spectra and electrochemical properties as in the parent homodinuclear compounds. The luminescence spectrum, however, shows that the emission band of the RuIIunit is almost completely quenched with concomitant sensitization of the emission of the OsIIunit. Electronic energy transfer from the RuIIto the OsIIunit takes place by two distinct processes (ken=2.0×108and 2.2×107s,1at 298 K). Oxidation of the OsIIunit of [(bpy)2Ru(1)Os (bpy)2]4+by CeIVor nitric acid leads quantitatively to the [(bpy)2RuII(1)OsIII(bpy)2]5+complex which exhibits a bpy-to-OsIIIcharge-transfer band at 720 nm (,max=250,M,1cm,1). Light excitation of the RuIIunit of [(bpy)2RuII(1)OsIII(bpy)2]5+is followed by electron transfer from the RuIIto the OsIIIunit (kel,f=1.6×108and 2.7×107s,1), resulting in the transient formation of the [(bpy)2RuIII(1)OsII(bpy)2]5+complex. The latter species relaxes to the [(bpy)2RuII(1)OsIII(bpy)2]5+one by back electron transfer (kel,b=9.1×107and 1.2×107s,1). The biexponential decays of the [(bpy)2*RuII(1)OsII(bpy)2]4+, [(bpy)2*RuII(1)OsIII(bpy)2]5+, and [(bpy)2RuIII(1)OsII(bpy)2]5+species are related to the presence of two conformers, as expected because of the steric hindrance between hydrogen atoms of the pyridine and phenyl rings. Comparison of the results obtained with those previously reported for other Ru,Os polypyridine complexes shows that the macrocyclic ligand 1 is a relatively poor conducting bridge. [source] Reaction of para -Hydroxy-Substituted Diphenylmethanes with tert -Butoxy RadicalCHEMPHYSCHEM, Issue 8 2004Catarina F. Correia What is the outcome of this reaction? In acetonitrile solution, the methylenic CH bond is approximately 25 kJ,mol,1 weaker than the OH bond in the same molecule (see picture), as demonstrated by time-resolved photoacoustic calorimetry and quantum chemical methods. However, as shown by electron spin resonance spectroscopy, the tert -butoxy radical selectively abstracts the hydrogen atom from the OH group. [source] Two-photon Dissociation Study of Carbon Disulfide in Acetonitrile at 266 nmCHINESE JOURNAL OF CHEMISTRY, Issue 1 2006Hao-Jie Fang Abstract Using laser flash photolysis/transient absorption technique for the study of two photon photodissociation of carbon disulfide in acetonitrile solution at 266 nm, the transient UV-Vis absorption spectrum of Rydberg state CS2 (6s,g) within 240,370 nm and subsequent dissociation product CS (,3,) with the maximum absorption at 260 nm were directly observed. The lifetime of CS (,3,) in the nitrogen and oxygen saturated solution is also studied in our experiment. [source] Synthesis, Characterisation and Optical Properties of Silica Nanoparticles Coated with Anthracene Fluorophore and Thiourea Hydrogen-Bonding SubunitsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 36 2008Pilar Calero Abstract Bifunctionalised hybrid silica nanoparticles have been synthesised and characterised, and their optical emission properties in the presence of certain anions in acetonitrile solutions have been studied. The alkoxysilane derivatives N -butyl- N, -[3-(trimethoxysilyl)propyl]thiourea (1), N -phenyl- N, -[3-(trimethoxysilyl)propyl]thiourea (2) and 3-[(anthracen-10-yl)methylthio]propyltriethoxysilane (3) were prepared and used to functionalise uncoated LUDOX silica nanoparticles with a mean diameter of 18,±,2 nm. The functionalisation of the nanoparticle surfaces was carried out by two different approaches. The first approach relies on the consecutive grafting of the two subunits. In this protocol, the nanoparticles were first functionalised with anthracene derivative 3 (solid NA), and then treated with the corresponding binding sites 1 or 2 to result in the NA-Pt3 and NA-Bt3 solids. The second approach deals with the simultaneous grafting of 1 or 2 and the signalling subunit 3 in different ratios. This method was used for the preparation of the NA1Pt1, NA1Bt1, NA1Pt3 and NA1Bt3 nanoparticles. The bifunctionalised silica nanoparticles were characterised by using standard techniques. Acetonitrile suspensions of NA nanoparticles (5 mg in 20 mL) showed anthracene bands centred at ca. 350, 370 and 390 nm. Upon excitation at 365 nm, a typical emission band with fine structure in the 390,450 nm range was observed. Similar absorption and emission spectra were found for the bifunctionalised nanoparticles. The work is completed with a prospective study of the fluorescence of the prepared nanoparticles in the presence of organic (acetate, benzoate) and inorganic (F,, Cl,, Br,, CN,, HSO4, and H2PO4,) anions. The apparent binding constants (adsorption constants) for the interaction of NA-Pt3 with anions in acetonitrile were determined by performing a Langmuir-type analysis of fluorescence titration data.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] | ||||||||||||||||||||||