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101.
AbstractA small series of amino oligo-phenylenevinylenes (OPVs) were successfully synthesized from their nitro-analogs in a rapid, simple, and highly efficient fashion employing a sodium sulfide/pyridine system as a reducing agent. In this research, classic and sustainable reduction methodologies including NH4HCO2/Zn and a choline chloride/tin (II) chloride deep eutectic solvent (DES) were also evaluated, showing degradation products, incomplete reactivity, and product isolation difficulties in all cases. The straightforward Na2S/pyridine synthetic protocol proved to maintain the E-E stereochemistry of the OPV backbone that has been previously assembled by the Mizoroki–Heck cross-coupling reaction. Also, the optoelectronic properties were determined and discussed, considering the amino group insertion in these conjugated systems as a contribution for future construction of novel materials with applications in supramolecular electronics, light harvesting, and photocatalysis. 相似文献
102.
Jose M. Giron‐Sierra Jose G. Wagner‐Lopez 《International Journal of Mathematical Education in Science & Technology》2013,44(6):841-853
Because of their graphics capabilities, it is possible to use personal computers to analyse the behaviour of dynamical systems. We therefore require a way to introduce pedagogically both this technique and the important aspects of the study of non‐linear systems. This paper considers first the formal points of the phase plane method, and then presents three relevant examples: (a) second order linear systems; (b) the Van der Pol oscillator; and (c) the forced pendulum. In each case programs in Turbo‐Pascal are given for plotting the trajectories. 相似文献
103.
Kenneth W. Henderson Alan R. Kennedy Arlene E. McKeown Robert E. Mulvey 《Acta Crystallographica. Section C, Structural Chemistry》2001,57(6):674-675
The title complex, [ZrCl2(C4H8O)2(C14H14N)2]·0.5C7H8, was prepared in an unusual manner by utilizing [Mg{N(CH2Ph)2}2] as a ligand transfer reagent. The Zr atom lies in a distorted octahedral environment where steric repulsion from the large dibenzylamino ligands leads to a widening of the N—Zr—N angle [99.95 (9)°] and corresponding compression of other angles [Cl—Zr—Cl 160.95 (3)° and O—Zr—O 78.22 (7)°]. This distortion is compared with those found in the previously determined structures of the dimethylamino and diethylamino analogues. 相似文献
104.
Sara Sierra Katerina Duskova María-José Fernández Lourdes Gude Antonio Lorente 《Tetrahedron》2012,68(42):8773-8782
Cyclo-bisintercalands are macrocyclic systems containing aromatic subunits, which are commonly used as hosts for aromatic molecules and as DNA intercalators. In this article, a step-by-step synthesis of a series of cyclo-bisintercalands containing 3,6-diaminoacridines as aromatic units, and connected by rigid spacers of different lengths, is reported. In addition, we describe herein a more efficient synthetic alternative, involving single-step template-directed processes. The new routes allow the easy synthetic access to these macrocyclic systems with acceptable yields. The synthesized cyclo-bisintercalands and their precursors have been structurally characterized by UV–visible and NMR methods. Preliminary biological activity assays performed on the bisintercalands and cyclo bisintercalands revealed interesting cytotoxic properties against different tumor cell lines, especially in the case of the bisintercalands, highlighting their potential as cancer chemotherapeutic agents. 相似文献
105.
Gómez-Gallego M Pellico D Ramírez-López P Mancheño MJ Romano S de la Torre MC Sierra MA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(20):5997-6005
The very low reduction potential of the chelate Fe(III)-EDDHA (EDDHA = ethylenediamine N,N'-bis(2-hydroxy)phenylacetic acid) makes it unreactive in photochemically or chemically induced electron transfer processes. The lack of reactivity of this complex toward light invalidates photodegradation as an alternative mechanism for environmental elimination. However, in spite of its low reduction potential, the biological reduction of Fe(III)-EDDHA is very effective. Based on electrochemical measurements, it is proposed that Fe(III)-EDDHA itself is not the substrate of the enzyme ferric chelate reductase. Likely, at the more acidic pH in the vicinity of the roots, the ferric chelate in a closed form (FeL-) could generate a vacant coordination site that leads to an open hexacoordinate species (FeHL) where the reduction of the metal by the enzyme takes place. 相似文献
106.
Yunta F García-Marco S Lucena JJ Gómez-Gallego M Alcázar R Sierra MA 《Inorganic chemistry》2003,42(17):5412-5421
Iron chelates such as ethylenediamine-N,N'-bis(2-hydroxyphenyl)acetic acid (EDDHA) and their analogues are the most efficient soil fertilizers to treat iron chlorosis in plants growing in calcareous soils. EDDHA, EDDH4MA (ethylenediamine-N,N'-bis(2-hydroxy-4-methylphenyl)acetic acid), and EDDCHA (ethylenediamine-N,N'-bis(2-hydroxy-5-carboxyphenyl)acetic acid) are allowed by the European directive, but also EDDHSA (ethylenediamine-N,N'-bis(2-hydroxy-5-sulfonylphenyl)acetic acid) and EDDH5MA (ethylenediamine-N,N'-bis(2-hydroxy-5-methylphenyl)acetic acid) are present in several commercial iron chelates. In this study, these chelating agents as well as p,p-EDDHA (ethylenediamine-N,N'-bis(4-hydroxyphenyl)acetic acid) and EDDMtxA (ethylenediamine-N,N'-bis(2-metoxyphenyl)acetic acid) have been obtained following a new synthetic pathway. Their chemical behavior has been studied to predict the effect of the substituents in the benzene ring on their efficacy as iron fertilizers for soils above pH 7. The purity of the chelating agents has been determined using a novel methodology through spectrophotometric titration at 480 nm with Fe(3+) as titrant to evaluate the inorganic impurities. The protonation constants were determined by both spectrophotometric and potentiometric methods, and Ca(2+) and Mg(2+) stability constants were determined from potentiometric titrations. To establish the Fe(3+) and Cu(2+) stability constants, a new spectrophotometric method has been developed, and the results were compared with those reported in the literature for EDDHA and EDDHMA and their meso- and rac-isomers. pM values have been also determined to provide a comparable basis to establish the relative chelating ability of these ligands. The purity obtained for the ligands is higher than 87% in all cases and is comparable with that obtained by (1)H NMR. No significant differences have been found among ligands when their protonation and stability constants were compared. As expected, no Fe(3+) complexation was observed for p,p-EDDHA and EDDMtxA. The presence of sulfonium groups in EDDHSA produces an increase in acidity that affects their protonation and stability constants, although the pFe values suggest that EDDHSA could be also effective to correct iron chlorosis in plants. 相似文献
107.
F. Sierra C. Sanchez-Pedreño T. Perez C. Martinez M. Hernandez 《Analytica chimica acta》1975,78(2):277-283
Phenosafranine in the presence of ethylenediaminetetraacetic acid is reduced to the leuco dye form on illumination with white light. The rate of photoreduction is strongly pH-dependent and exhibits a maximum at about pH 6. Variables such as wavelength and intensity of the light and the concentration of reactants have been studied. The photoreduction involves a long-lived excited state of the dye and is retarded by small amounts of p-phenylenediamine and iodide. The dye is used as an amperometric indicator in titrations of Pb(II), Zn(II) and Cu(II) with EDTA; the method is applicable in the range 0.02–0.0005 M. The current is caused by anodic oxidation of the phenosafranine reduced in the photochemical reaction with EDTA. 相似文献
108.
Yolanda Pérez Isabel del Hierro Isabel Sierra Magda Monari Antonio Otero 《Journal of organometallic chemistry》2004,689(22):3492-3500
A variety of monocyclopentadienyl alkoxo titanium dichloride and bisalkoxo titanium dichloride complexes have been prepared and characterized by spectroscopic techniques. The titanium derivatives containing both cyclopentadienyl and various alkoxo ligands [Ti(η5-C5H5)(OR)Cl2] (1-5) have been synthesized from the reaction of [Ti(η5-C5H5)Cl3] with 1 equivalent of the corresponding alcohol in THF in the presence of triethylamine (ROH = Adamantanol, 1R,2S,5R-(−)-menthol, 1S-endo-(−)-borneol, cis-1,3-(−)-benzylideneglycerol, 1,2:3,4-di-O-isopropylidene-α-d-galactopyranose). The bisalkoxo titanium dichloride derivatives [TiCl2(OR)2] (6-10) have been prepared by a redistribution reaction between Ti(OR)4 and TiCl4 compounds 6-8 (OR = Adamantanoxy, (1R,2S,5R)-(−)menthoxy, (1S-endo)-(−)-borneoxy) and by reaction of [Ti(OR)2(OPri)2]2 with CH3COCl compounds 9 and 10 (OR = 1,2:3,4-di-O-isopropylidene-α-d-galactopyranoxy, and 1,2:5,6-di-O-isopropylidene-α-d-glucofuranoxy). The molecular structures of 2 and 3 have been determined by single crystal X-ray diffraction studies. 相似文献
109.
RaquelM. Cravero Manuel Gonzlez‐Sierra GuillermoR. Labadie 《Helvetica chimica acta》2003,86(8):2741-2753
Different convergent approaches to the highly oxygenated sesquiterpene natural product saudin ( 1 ), has been investigated. Our strategy has included a Michael addition and aldol condensation reaction as key steps. During the synthetic development, we have found serious steric hindrance when an α‐Me‐substituted alkyl vinyl ketone was used. Such steric hindrance has been overcome by synthesizing the vinyl ketone 16 through an anionic fragmentation, which was carefully studied. Finally, the intermediate 18 has been synthesized in a one‐pot reaction from the vinyl ketone 16 and has been cyclized to obtain the promising tricyclic intermediate 20 . 相似文献
110.
Dr. Matthieu Fonvielle Dr. Inés Li de La Sierra‐Gallay Dr. Afaf H. El‐Sagheer Maxime Lecerf Delphine Patin Dr. Dénia Mellal Dr. Claudine Mayer Dr. Didier Blanot Dr. Nittaya Gale Dr. Tom Brown Dr. Herman van Tilbeurgh Dr. Mélanie Ethève‐Quelquejeu Dr. Michel Arthur 《Angewandte Chemie (International ed. in English)》2013,52(28):7278-7281