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The Cu2+, Mn2+, and Fe3+ complexes of a 14 membered macrocycle were synthesized and their antioxidant capacities were evaluated against ABTS and DPPH radicals, with the objective of collecting insights into the biomimetic role of the... more
The Cu2+, Mn2+, and Fe3+ complexes of a 14 membered macrocycle were synthesized and their antioxidant capacities were evaluated against ABTS and DPPH radicals, with the objective of collecting insights into the biomimetic role of the central metal ions. The macrocycle, abbreviated as H2L14, is a derivative of EDTA cyclized with 1,4-diamine, and the moderately flexible macrocyclic frame permits the formation of [ML14·H2O] chelates with octahedral coordination geometries common among the metal ions. The metal complexes were characterized by electrospray-ionization mass spectrometry, Fourier transform infrared spectroscopy, and Raman and X-ray photoelectron spectroscopic methods, as well as thermogravimetric analysis; the octahedral coordination geometries with water coordination were optimized by DFT calculations. The antioxidant assays showed that [FeL14·H2O]+ was able to scavenge synthetic radicals with moderate capacity, whereas the other metal chelates did not show significant act...
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The absolute structure of D-glutamic acid hydrochloride [systematic name: (R)-1,3-dicarboxypropan-1-aminium chloride], C5H10NO4 +·Cl−, has been determined by single-crystal X-ray diffraction at room temperature using Cu Kα radiation.
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A new macrocycle bearing tyramine arms through amide linkages, 2,2 0-(2,9-dioxo-1,4,7,10-tetraazacy-clotridecane-4,7-diyl)bis(N-(4-hydroxyphenethyl)acetamide) abbreviated as L13Tyra, has been synthesized with amide-coupling agents in a... more
A new macrocycle bearing tyramine arms through amide linkages, 2,2 0-(2,9-dioxo-1,4,7,10-tetraazacy-clotridecane-4,7-diyl)bis(N-(4-hydroxyphenethyl)acetamide) abbreviated as L13Tyra, has been synthesized with amide-coupling agents in a microwave reactor. This macrocycle involves two potential metal-coordinating and bioactive sites, i.e., the tetraaza-macrocyclic ring (with a low basicity of the amino nitrogen) and the pendant phenol arms (with a small pK a 8.6). The Cu 2+ complex has different compositions in solid and in solution. An X-ray crystal study shows that a mononuclear complex [Cu (L13Tyra – 2H)] 0 is formed with a square coordination of two deprotonated amide nitrogen and two amino nitrogen atoms of the macrocyclic ring; a carbonyl oxygen atom from a pendant arm occupies an axial site to construct a square pyramid. UV–Vis spectrometric titrations in aqueous solutions indicate the formation of a binuclear complex [Cu 2 (L13Tyra – 4H)(H 2 O) x ] 0 in which phenolate oxygen atoms of the tyramine arms coordinate a Cu 2+ ion in addition to the coordination of the macrocyclic chelate; such a binuclear structure is maintained only in solution. The uncoordinated ligand has a high antioxidant capacity with a TEAC (Trolox equivalent antioxidant capacity) assay comparable to that of ascorbic acid, thanks to the phenolic OH of the tyramine arms. Copper(II) ion works as an inhibitor against the activity; the TEAC assay of the binuclear complex is as small as one-twentieth that of the uncoordinated ligand. Antiproliferative and cytotoxic assays with normal and cancer cell lines show no toxicity for both the ligand and its Cu 2+ complex.
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The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by... more
The synthesis, acid-base behavior, and Cu(2+) coordination chemistry of a new ligand (L1) consisting of an azamacrocyclic core appended with a lateral chain containing a 3-hydroxy-2-methyl-4(1H)-pyridinone group have been studied by potentiometry, cyclic voltammetry, and NMR and UV-vis spectroscopy. UV-vis and NMR studies showed that phenolate group was protonated at the highest pH values [log K = 9.72(1)]. Potentiometric studies point out the formation of Cu(2+) complexes of 1:2, 2:2, 4:3, 1:1, and 2:1 Cu(2+)/L1 stoichiometries. UV-vis analysis and electrochemical studies evidence the implication of the pyridinone moieties in the metal coordination of the 1:2 Cu(2+)/L1 complexes. L1 shows a stronger chelating ability than the reference chelating ligand deferiprone. While L1 shows no cytotoxicity in HeLa and ARPE-19 human cell lines (3.1-25.0 μg/mL), it has significant antioxidant activity, as denoted by TEAC assays at physiological pH. The addition of Cu(2+) diminishes the antioxid...
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1Departamento de Investigación en Polímeros y Materiales, Universidad de Sonora, Hermosillo, Sonora, México 2Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, Ciudad... more
1Departamento de Investigación en Polímeros y Materiales, Universidad de Sonora, Hermosillo, Sonora, México 2Instituto de Investigaciones en Materiales, Universidad Nacional Autónoma de México, Apartado Postal 70-360, Ciudad Universitaria, México DF 04510, ...
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Electrical conductivities and ESR spectra were obtained for polyaniline salts that contained different counter anions. The electrical properties were markedly different from one salt to another, although the concentrations of... more
Electrical conductivities and ESR spectra were obtained for polyaniline salts that contained different counter anions. The electrical properties were markedly different from one salt to another, although the concentrations of counteranions were almost identical. The ESR ...
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ABSTRACT Three DTPA-amide cyclophanes – including conformational isomers – have been isolated by optimizing the conditions of a reaction between diethylenetriaminepentaacetic (DTPA) dianhydride and p-xylenediamine: a 2 + 2-cyclization... more
ABSTRACT Three DTPA-amide cyclophanes – including conformational isomers – have been isolated by optimizing the conditions of a reaction between diethylenetriaminepentaacetic (DTPA) dianhydride and p-xylenediamine: a 2 + 2-cyclization product, abbreviated as (cy2)H6, that integrates two phenylene groups in the macrocyclic frame and bears six pendant –CH2CO2H arms, and two isomeric 1 + 1-macrocyles, (cy1)H3, carrying three arms. A crucial factor for controlling the ring size is the concentration in the reaction. For (cy2)H6, whose binuclear Gd3+ complex is a potential paramagnetic protein sensor, the synthetic method has been established in 70% yield. The isomerism of (cy1)H3 is due to the conformation of the rigid macrocyclic frame; the 1H NMR and geometry optimization show that the conformation is of quasi-C2 symmetry in one (cy1)H3 isomer, and of quasi-mirror symmetry in the other. Their distinct conformations define the chemical properties and coordination capability toward Gd3+: in the C2-symmetric isomer, the amino nitrogen is less basic and the N–H bond is more covalent than in the mirror-symmetric isomer; the former forms a mononuclear Gd3+ complex whereas the latter does not show sign of complexation with Gd3+.
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Abstract The reaction of aniline with copper (II) perchlorate in acetonitrile yields highly-electroconductive polyaniline perchlorate,[(-C 6 H 4 NH-)(ClO 4) m· nH 2 O] x, which is soluble in dimethylsulfoxide (DMSO) and has low degrees of... more
Abstract The reaction of aniline with copper (II) perchlorate in acetonitrile yields highly-electroconductive polyaniline perchlorate,[(-C 6 H 4 NH-)(ClO 4) m· nH 2 O] x, which is soluble in dimethylsulfoxide (DMSO) and has low degrees of branching and/or ...
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Molecular recognition of an anionic meta-cyclophane towards bioactive amines and related compounds has been studied by H NMR titration: the meta-cyclophane, which is functionalised by pendant arms, is... more
Molecular recognition of an anionic meta-cyclophane towards bioactive amines and related compounds has been studied by H NMR titration: the meta-cyclophane, which is functionalised by pendant arms, is 2,9,18,25-tetraoxo-4,7,20,23-tetrakis(carboxymethyl)-1,4,7,10,17,20,23,26-octaaza[10.10]metacyclophane; the bioactive guests studied are histamine, tryptamine, tyramine, phenethylamine, imidazole, histidine, phenylalanine and 4-aminobenzoic acid. Complex formation of a para-cyclophane isomer has also been studied for comparison. The meta-cyclophane forms a
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Formation of host–guest complexes with acetic acid and benzoic acid was studied by NMR for amide-based octaazacyclophanes having pendant methyl ester arms; the cyclophanes were tetramethyl... more
Formation of host–guest complexes with acetic acid and benzoic acid was studied by NMR for amide-based octaazacyclophanes having pendant methyl ester arms; the cyclophanes were tetramethyl 2,9,18,25-tetraoxo-1,4,7,10,17,20,23,26-octaaza[10.10]paracyclophane-4,7,20,23-tetraacetate, its meta-isomer and analogues. Amide NH proton and CH2 proton adjacent to amide C = O in every cyclophane host showed down-field NMR shifts in the presence of the guest acids in CHCl3-d, suggesting the
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... Daniela Aguilera-Márquez a , Claudia Virués a & Motomichi Inoue a pages 737-742. ... Inorg. Chim. Acta , 324: 7380. [CrossRef], [Web of Science ®] View all references, 25 25. Inoue, MB, Villegas, CA, Asano, K.,... more
... Daniela Aguilera-Márquez a , Claudia Virués a & Motomichi Inoue a pages 737-742. ... Inorg. Chim. Acta , 324: 7380. [CrossRef], [Web of Science ®] View all references, 25 25. Inoue, MB, Villegas, CA, Asano, K., Nakamura, M., Inoue, M. and Fernando, Q. 1992. Inorg. Chem. ...
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Electrical conductivities and ESR spectra were obtained for polyaniline salts that contained different counter anions. The electrical properties were markedly different from one salt to another, although the concentrations of... more
Electrical conductivities and ESR spectra were obtained for polyaniline salts that contained different counter anions. The electrical properties were markedly different from one salt to another, although the concentrations of counteranions were almost identical. The ESR ...
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ABSTRACT Chelating aza-cyclophanes were synthesized by reactions of diethylenetriaminepentaacetic acid (or DTPA) dianhydride with aromatic diamines, 4,4′-diaminobibenzyl (DAB) and 4,4′-bis(1,1′-biphenyl-4,4′-diyldioxy)dianiline (BPA). The... more
ABSTRACT Chelating aza-cyclophanes were synthesized by reactions of diethylenetriaminepentaacetic acid (or DTPA) dianhydride with aromatic diamines, 4,4′-diaminobibenzyl (DAB) and 4,4′-bis(1,1′-biphenyl-4,4′-diyldioxy)dianiline (BPA). The former amine gave a 2:2-cyclization product bearing six –CH2CO2H arms, 2,12,29,39-tetraoxo-4,7,10,31,34,37-hexakis(carboxymethylene)-1,4,7,10,13,28,31,34,37,40-decaaza-[13.2.13.2]ethylenparacyclophane, abbreviated as cy(bisdtpadab)H6, whereas BPA yielded a 1:1-cyclization product carrying three –CH2CO2H arms, 2,12-dioxo-4,7,10-trakis(carboxymethylene)-1,4,7,10,13-pentaaza-20,33-dioxa[13.0.1]paracyclophane, abbreviated as cy(dtpabpa)H3. Their protonation and complexation with Gd(III) were studied by fluorescence spectra, 1H NMR and potentiometry. The macrocyclic framework of cy(dtpabpa)H3 has a high rigidity; as a consequence, this ligand is incapable of forming a complex with Gd(III). In contrast, cy(bisdtpadab)H6, which is moderately rigid, forms a binuclear Gd(III) complex, as confirmed by a sensitive quenching of the fluorescence upon complexation. On the basis of the pH dependence of the fluorescence spectra, the logarithmic overall formation constants were determined as log βM2L = 28.3, log βM2LH = 31.9, log βM2LH−1 = 21.0, logβM2LH−2 = 9.8. For the chelating cyclophanes, the rigidity is one of major controlling factors for the stability of their complexes. The sharp change in the fluorescence intensity upon complexation with Gd3+ ion suggests that the chelating cyclophane works potentially as fluorescent probes toward specific metal ions.
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We have synthesized silver nanoparticles from silver nitrate solutions using extracts of Rumex hymenosepalus, a plant widely found in a large region in North America, as reducing agent. This plant is known to be rich in antioxidant... more
We have synthesized silver nanoparticles from silver nitrate solutions using extracts of Rumex hymenosepalus, a plant widely found in a large region in North America, as reducing agent. This plant is known to be rich in antioxidant molecules which we use as reducing agents. Silver nanoparticles grow in a single-step method, at room temperature, and with no addition of external energy. The nanoparticles have been characterized by ultraviolet-visible spectroscopy and transmission electron microscopy, as a function of the ratio of silver ions to reducing agent molecules. The nanoparticle diameters are in the range of 2 to 40 nm. High-resolution transmission electron microscopy and fast Fourier transform analysis show that two kinds of crystal structures are obtained: face-centered cubic and hexagonal.
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ABSTRACT Complex formation of three anionic cyclophanes with the dications of diaminoalkanes and basic amino acid esters was studied by 1H NMR titrations in aqueous media. Every cyclophane bearing six CH2CO2− arms consists of two... more
ABSTRACT Complex formation of three anionic cyclophanes with the dications of diaminoalkanes and basic amino acid esters was studied by 1H NMR titrations in aqueous media. Every cyclophane bearing six CH2CO2− arms consists of two diethylenetriaminepentaacetic (DTPA) units linked by two aromatic diamine units through amide bonds; the interlinking amine is p-xylenediamine (abbreviated as px), 4,4′-methylenedianiline (ma) or 4,4′-diaminobibenzyl (dab). The cyclophanes that exist in the anionic form cyH24− (with two acidic protons) have multi-point electrostatic interaction with diaminoalkane dications +H3N(CH2)n NH3+, so as to construct ion pairs stabilized by hydrogen-bonding between CH2CO2− and NH3+. The formation constants vary from 31 to 2,477 M−1 depending on the cation–anion combinations; the highest stability is found for the complex of the px-derived cyclophane, cy(px)H24−, with diaminobutane, and the lowest for diaminobutane–cy(dab)H24− pair. The stability is correlated with the chain length of the diaminoalkanes as well as the size of the cyclophanes. These geometrical factors are also crucial for ion-pairing with the dications of methylated lysine and arginine; the formation constant is 2,884 M−1 for (lys)H22+–cy(px)H24−, and 1,688 M−1 for (arg)H22+–cy(px)H24−, while the constants of the cy(ma)H24− and cy(dab)H24− complexes are in a much smaller range of 39–230 M−1. Graphical Abstract Anionic cyclophanes bearing carboxylate arms have multi-point electrostatic interaction with the methylated basic amino acid dications as well as diaminoalkane dications in aqueous media, to construct ion pairs with intermolecular hydrogen bonding N+–H···O−. The formation constants vary from 31 to 2,884 M−1, depending on the alkyl chain length as well as the cyclophane frame size. The highest stability is found for a complex of lysine ester.
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... and their diester derivatives Michiko B. lnoue .b.,, Rosa Elena Navarre , Isaias O. Landfn , D. Margarita L6pez , Motomichi Inoue a, Quintus Fernando b CIPM. Universidad de Sonora. ... All calculations were performed on a VAX computer... more
... and their diester derivatives Michiko B. lnoue .b.,, Rosa Elena Navarre , Isaias O. Landfn , D. Margarita L6pez , Motomichi Inoue a, Quintus Fernando b CIPM. Universidad de Sonora. ... All calculations were performed on a VAX computer with the program package MolEn. ...