Juan Aguilar

University of Valencia, Valenza, Valencia, Spain

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Publications (28)71.3 Total impact

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    ABSTRACT: ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
    ChemInform 08/2010; 30(35). DOI:10.1002/chin.199935189
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    ABSTRACT: The novel cyclophane receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane L presents a molecular architecture which enables recognition in aqueous solution of ATP, ADP and AMP through electrostatic, hydrogen bonding and pi-stacking interactions; electrostatic interactions occur between the polyammonium sites of L and the phosphate chain of the nucleosides, and pi-stacking interactions occur between the m-phenylene subunit incorporated in the receptor as a non-pendant integral part of the macrocyclic framework and the adenine ring of the nucleotides.
    ChemInform 03/2010; 27(11). DOI:10.1002/chin.199611279
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    ABSTRACT: A bibracchial lariat aza-crown ether ( L) consisting of 2-aminoethylnaphthyl moieties appended to a 2 : 2 azapyridinophane structure displays significant activation of H-D exchange in malonic acid. The compound forms very stable adducts with malonate anions ( MA) in the 2-10 pH range. Molecular dynamics studies performed for the species resulting from the interaction of the hexaprotonated macrocycle and the dianion show that malonate is encapsulated by L with distances between the CH2 group of malonate and the pyridine nitrogens of ca. 3.5 angstrom. The pendant arms of L cap above and below the anion, de. ning a pseudo-cage structure. Quantum chemical calculations for alpha-proton abstraction from malonate by the protonated ligand L, at the B3LYP/6-31G** computational level using reduced models, have allowed transition states to be obtained that denote a concerted mechanism in which alpha-proton abstraction is accompanied by proton transfer from protonated amino groups of the receptor to the carboxylate groups. Kinetic measurements for ligand L, performed at pD = 6 following the variation of the H-1-NMR MA-CH2 and MA-CHD signals, allow the following rate constants to be calculated: k(1)(H) = (60.2 +/- 0.5) x 10(-3) min(-1) and k(2)(H) = ( 75.3 +/- 0.6) x 10(-3) min(-1), with values that equal the experimental values of the free substrate at pD = 0. The rate enhancement produced by the open-chain reference ligand ( L-1), containing the polyamine tren ( tris(2-aminoethyl) amine) functionalized at one of its terminal amino groups with a naphthyl moiety, is much more moderate, with k(1)(H) = ( 9.2 +/- 0.2) x 10(-3) min(-1) and k(2)(H) = ( 11.56 +/- 0.03) x 10(-3) min(-1).
    New Journal of Chemistry 11/2007; 31(12-12):2065-2070. DOI:10.1039/b618787k · 3.16 Impact Factor
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    ABSTRACT: The characteristics as a chemosensor of the compound 3-methyl-6,8-di(2-pyridyl)-[1,2,3]triazolo[5',1':6,1]pyrido[2,3-]pyrimidine (1) have been analyzed. Interaction with Cu(2+) produces a quenching of the fluorescence, while interaction with Zn(2+) leads to a quenching of the fluorescence followed by a bathochromic shift. The crystal structure of the Zn(1)(H(2)O)(3)(ClO(4))(2) x H(2)O complex shows the coordination of Zn(2+) through the terpyridine moiety. The octahedral site is completed by three water molecules. Interactions of the Zn(2+) complex with the anions sulfate, nitrate, nitrite, and dihydrogenphosphate in ethanol produce hypsochromic shifts and restoration of the fluorescence whose magnitude depends on the anion involved. The maximum interaction is observed for H(2)PO(4)(-). Interactions of the Zn(2+) complex with the amino acids l-aspartate and l-glutamate have also been explored showing a higher interaction with l-aspartate.
    The Journal of Organic Chemistry 12/2006; 71(24):9030-4. DOI:10.1021/jo061326e · 4.64 Impact Factor
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    ABSTRACT: The synthesis of the terpyridinophane-type polyamine 2,6,9,12,16-pentaaza[17]-(5,5' ')-cyclo-(2,2':6',2' ')-terpyridinophane heptahydrobromide tetrahydrate (L.7HBr.4H2O) is described. L presents six protonation constants with values in the range 9.21-3.27 logarithmic units. L interacts with Cu2+ and Zn2+ forming in both cases, neutral, protonated, and hydroxylated mono- and binuclear complexes whose constants have been calculated by potentiometry in 0.15 M NaClO4 at 298.1 K. The crystal structures of the compounds [Cu(HL-carb)(H2O)](ClO4)3.2H2O (1) and [Cu2(H2L)(CO3)]2(ClO4)8.9H2O (2) have been solved by X-ray diffraction. In 1, the metal center presents square pyramidal geometry. The base of the pyramid is formed by the three nitrogen atoms of pyridine and one oxygen atom of a CO2 group which is forming a carbamate bond with the central nitrogen atom of the polyamine chain. The axial position is occupied by a water molecule. In 2, one Cu2+ is bound by the three pyridine nitrogens and the other one by the three central nitrogen atoms of the polyamine chain. The square planar coordination geometry is completed by a carbonate group taken up from the atmosphere that behaves as a bridging mu,mu'-ligand between the two centers. The pH-metric titrations on the ternary Cu2+-L-carbonate and Zn2+-L-carbonate systems show the extensive formation of adduct species which above pH 6 are formed quantitatively in solution. The stoichiometries of the main species formed in solution at pH = 6.8 agree with those found in the crystalline compounds. CO2 uptake by the Zn2+ and Cu2+ 1:1 complexes in aqueous solution has also been followed by recording the variations in the band at ca. 300 nm. The formation of the Zn2+ carbamate moiety has been evidenced by 13C NMR and ESI spectroscopy.
    Inorganic Chemistry 06/2006; 45(9):3803-15. DOI:10.1021/ic060278d · 4.79 Impact Factor
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    ABSTRACT: L-glutamate and L-aspartate selectivity is achieved by the action of two Cu2+ metal ions rightly disposed in a cyclophane-type macrocyclic framework; electrochemical sensing of glutamate has been achieved by adsorption of the copper complexes on graphite electrodes.
    Chemical Communications 07/2005; DOI:10.1039/b503417e · 6.72 Impact Factor
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    ABSTRACT: [structure: see text] The interaction of a macrocycle containing three trans-(1R,2R)-diaminocyclohexane units connected by p-xylene spacers with the isomers 1,3,5-benzenetricarboxylic (1,3,5-BTC), 1,2,4-benzenetricarboxylic (1,2,4-BTC), and 1,2,3-benzenetricarboxylic (1,2,3-BTC) acids and their relevant anions is studied by means of potentiometric and NMR analysis. The interaction is highest for the isomer 1,3,5-BTC, which perfectly fits within the macrocyclic cavity of the host species. The studies have been extended to the triacid 1,3,5-benzenetriacetic observing in this case the effect of a size mismatch between host and guest species.
    The Journal of Organic Chemistry 04/2005; 70(6):2042-7. DOI:10.1021/jo048000v · 4.64 Impact Factor
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    ABSTRACT: The synthesis, protonation behavior, and Cu2+ and Zn2+ coordination chemistry of the novel bibrachial aza lariat ether (naphthalen-1-ylmethyl)[2-(20-[2-[(naphthalen-1-ylmethyl)amino]ethyl]-3,6,9,17,20,23,29,30-octaazatricyclo[23.3.1.1*11,15*]triaconta-1(29),11(30),12,14,25,27-hexaen-6-yl)ethyl]amine (L) are discussed. The macrocycle, which has two aminoethyl naphthyl moieties symmetrically appended to a 2:2 azapyridinophane structure, displays, in the pH range 2-11, six protonation steps that correspond to the protonation of the secondary amino groups. Steady-state fluorescence measurements show emissions due to the monomer and to the excimer formed between the two naphthalene fragments of the macrocycle. The time-resolved fluorescence data, obtained by the time-correlated single photon counting technique, show that a significant percentage of excimer is preformed as ground-state dimers. The ligand L forms with the metal ions Cu2+ and Zn2+ mono- and dinuclear complexes in aqueous solution. The influence of metal coordination in the fluorescence emission of L is analyzed. The acid-base, coordination capabilities, and emissive behavior of L are compared with those presented by its synthetic precursor L1, which has a tripodal tris(2-aminoethyl)amine structure functionalized at one of its terminal amino groups with a naphthyl moiety.
    Inorganic Chemistry 10/2004; 43(19):6114-22. DOI:10.1021/ic049694t · 4.79 Impact Factor
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    ABSTRACT: The synthesis of the novel macrocycle 2,6,9,12,16-pentaaza-[17](2,9)(1,10)phenanthrolinophane (L3) is reported. Speciation studies on the systems Zn-II-L3 and Zn-II-L2 (L2 = 2,6,10,13,17,21-hexaaza[22]metacyclophane) performed in aqueous solution show the formation of mono- and dinuclear Zn-II complexes. In the two systems, the dinuclear complexes readily hydroxylate, with the hydroxo species being the main ones in solution at relatively low pH values. This feature makes these complexes promising hydrolytic agents for carboxy and phosphate esters. The hydrolytic ability of the L1-L3 dinuclear complexes toward the carboxy and phosphate ester bond was tested by addition of p-nitrophenyl acetate (NA) and bis(p-nitrophenyl)phosphate (BNP). While in the case of NA the cleavage takes place through a simple bimolecular mechanism and the hydrolysis rate depends on
    Berichte der deutschen chemischen Gesellschaft 10/2004; DOI:10.1002/ejic.200400164
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    ABSTRACT: The synthesis, protonation and Cu(II) coordination features of the novel azacyclophane type receptors 2,6,10,13,17,21-hexaza[22]-(2,6)-pyridinophane (L2), 2,6,9,12,15,19-hexaza[20]-(2,6)-pyridinophane (L5) and 2,6,9,12,15,19-hexaza[20]metacyclophane (L6) are presented. The protonation and Cu(II) constants are analysed and compared with the previously reported open-chain polyamines 4,8,11,15-tetrazaoctadecane-1,18-diamine (L1) and 4,7,10,13-tetraazahexadecane-1,16-diamine (L4) and of the cyclophane 2,6,10,13,17,21-hexaaza[22]paracyclophane (L3). All the systems form mono- and dinuclear complexes whose stability and pH range of existence depend on the type of hydrocarbon chains and molecular topology. The effects of the cyclic or open-chain nature and of the presence of the pyridine rings on the protonation and formation of mono- and dinuclear complexes are discussed. Stopped-flow kinetic measurements on the acid-promoted decomposition of the Cu(II) complexes have been carried out for the different systems. With respect to the decomposition of the dinuclear complexes, because the size of the macrocycles forces both metal ions to be close to each other, the release of the first ion occurs within the mixing time of the stopped-flow except for the dinuclear complexes of L2. However, the most interesting kinetic result is the observation of different kinetics of decomposition for the different mononuclear complexes formed by a given ligand. This effect is especially evident for L3 and L6 and indicates a change in the coordination mode of the ligand for the different mononuclear species. Therefore the Cu(II) ion performs a slippage motion through the macrocyclic cavity driven by pH changes. The stopped-flow experiments are an excellent tool to detect these slippage processes that may be present for the complexes with other macrocycles.
    Dalton Transactions 02/2004; DOI:10.1039/b311772c · 4.10 Impact Factor
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    ABSTRACT: Cited By (since 1996): 1, Export Date: 20 December 2011, Source: Scopus, Language of Original Document: English, Correspondence Address: García-España, E.; Departamento de Quimica Inorganica, Universidad de Valencia, C/ Dr. Moliner 50, 46100 Burjassot, Valencia, Spain; email: enrique.garcia-es@uv.es, References: Bianchi, A., Micheloni, M., Paoletti, P., (1991) Coord. Chem. Rev., 110, p. 17;
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    ABSTRACT: One of the first kinetic evaluations of a metal ion interchange between the two coordination sites of a ditopic macrocycle is presented.
    Chemical Communications 01/2004; DOI:10.1039/B309721H · 6.72 Impact Factor
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    ABSTRACT: The interaction in aqueous solution of adenosine 5′-triphosphate (ATP) with a series of open-chain polyamines linked at one or both ends to anthrylmethyl or naphthylmethyl fragments was followed by potentiometric titration, 1H-, 13C-, and 31P-NMR spectroscopy, and by steady-state fluorescence measurements. The results revealed greater stabilities for the compounds containing one anthracene moiety than for those with one naphthalene moiety, the stabilities of the compounds with both ends N-substituted with naphthylmethyl groups being close to those containing just one anthrylmethyl unit. The 1H-NMR spectra showed that in all systems, there is involvement of π-π stacking interactions in the stabilization of the adduct species. The competitive effect of the anions afforded by the supporting electrolyte was checked in some of the studied systems working at two different ionic strenghts (0.15M and 1.0M NaCl). The joint analysis of the spectrofluorimetric titrations and pH-metric species-distribution curves showed that for all the ATPreceptor systems, a quenching of the fluorescence occurred upon protonation of the adenine N(1)atom. Steady-state fluorescence and time-correlated single-photon-counting analysis of a system made up of ATP and a bis-chromophoric polyamine receptor containing anthracene and naphthalene fluorophores established that the energy-transfer process between the naphthalene and anthracene moieties is still operative despite the presence of ATP.
    Helvetica Chimica Acta 09/2003; 86(9):3118 - 3135. DOI:10.1002/hlca.200390253 · 1.39 Impact Factor
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    ABSTRACT: Cited By (since 1996): 10, Export Date: 20 December 2011, Source: Scopus, CODEN: CHCOF, Language of Original Document: English, Correspondence Address: Basallote, M.G.; Depto. Cie. Mat. e Ing. Metalurgica, Facultad de Ciencias, Universidad de Cádiz, Apartado 40, Puerto Real, 11510 Cádiz, Spain; email: Manuel.basallote@uca.es, Chemicals/CAS: 1,10 phenanthroline, 3829-86-5, 66-71-7; proton, 12408-02-5, 12586-59-3, References: Boyer, P.D., (1998) Angew. Chem. Int. Ed., 37, p. 2296;
    Chemical Communications 01/2003; 9:3032-3033. · 6.72 Impact Factor
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    ABSTRACT: The interaction of the polyamines 4,7,10,13-tetraazahexadecane-1,16-diamine (L1) and 4,7,10-triazatridecane-1,13-diamine (L2) with H+, Cu2+, Zn2+, Co2+ and the nucleotides ATP, ADP and AMP has been followed by NMR and potentiometric studies performed at 298.1 K in 0.15 mol dm−3 NaClO4. The influence of the different sequences of hydrocarbon chains and chelate rings present in the ligands on the values of the protonation constants, the stability of the metal ion complexes as well as in the co-ordination to nucleotides is analysed. The formation of mixed complexes has been investigated for the system Cu2+–L1–AMP.
    Inorganica Chimica Acta 11/2002; 339:307-316. DOI:10.1016/S0020-1693(02)00947-7 · 2.04 Impact Factor
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    ABSTRACT: A series of α,ω-diarylamines with a variable number of ethylenediamine units between terminal naphthylrings shows dramatic affinity changes towards double-stranded nucleic acids, particularly upon complexation with Cu(II) ions. Metal salts alone have under the applied conditions only a negligible effect. The affinity of the metal-free ligands towards nucleic acids shows significant differences to those of the underlying polyamines, with a reversed stabilization of DNA instead of the usually observed preference for RNA. The affinity changes and preliminary NMR studies are in line with intercalation of naphthylrings into the double-stranded nucleic acid, which is hampered by complex formation with Cu(II).
    Tetrahedron Letters 10/2002; 43(43):7801-7803. DOI:10.1016/S0040-4039(02)01765-3 · 2.39 Impact Factor
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    ABSTRACT: A comparative study of the binding of nitrate and sulfate with a polyammonium monocycle L(1), (3,6,9,17,20,23-hexaazatricyclo[23.3.1.1(11,15)]-triaconta-1(29),11,13,15(30),25,27-hexaene), and the corollary bicycle L(2), (1,4,12,15,18,26,31,39-octaazapentacyclo-[13.13.13.1(6,10).1(20,24).1(33,37)]-tetratetraconta-6,7,9,20(43),21,23,33(42),34,36-nonaene), is reported. Potentiometric studies indicated negligible binding for L(1) and nitrate, but high affinity was observed for sulfate (log K(H5L(SO4)/H5L-SO4) = 3.53(1), log K(H6L(SO4)/H6L-SO4) = 4.36(1)). Stronger binding was observed for the cryptand L(2) with both nitrate and sulfate (log K(H6L(NO3)/H6L-NO3) = 3.11(5), log K(H7L(NO3)/H7L-NO3) = 3.55(5); log K(H6L(SO4)/H6L-SO4) = 4.43(1), log K(H7L(SO4)/H7L-SO4) = 4.97(5)). Five crystal structures are reported: the nitrate (1) and sulfate (2) salts of L(1), the free base (3) of L(2), and the nitrate (4) and tosylate (5) salts of L(2). Structural results for L(1) indicate relatively planar monocycles with cis and trans orientations of the phenyl groups for 2 and 1, respectively, with the anions above and below the monocycle rings. For L(2), key features include an encapsulated water and intricate water network in 3, two encapsulated and four external nitrates and two external water molecules in 4, and six external tosylates with sulfonate groups pointing into the cavity and eight external waters in 5.
    Inorganic Chemistry 09/2001; 40(18):4710-20. DOI:10.1021/ic010135l · 4.79 Impact Factor
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    ABSTRACT: The complexation properties of Cu 2 + ions with the cyclophane receptors 2,6,9,13-tetraaza[14]metacyclophane (L1), 2,6,10,13,17,21-hexaaza[22]metacyclophane (L2) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L3) are presented. Formation of mononuclear complexes in the case of L1 and of mono-and binuclear complexes in the case of the hexaaazcyclophane ligands L2 and L3 is observed. The coordination numbers around each Cu 2 + in the binuclear complexes involve at most three nitrogen donors for each metal ion. Cyclophanes L1–L3 and several acyclic polyamine ligands are tested for their affinity towards double-stranded nucleic acid models of RNA and DNA. The binding affinity of the acyclic and macrocyclic polyamines towards DNA and RNA models, measured by changes in their melting temperature DT M , increases progressively with the average number of charges present on the amine, with higher stabilisation for RNA. Unusually large differences of up to D(DT M) =30°C were observed with tripropylenetetraamine (L15) and with the macrocyclic amines (L2 and L3). Introduction of copper in the ligands leads to considerable affinity variations. One macrocyclic copper complex (with L3) shows a strong discrimination between the RNA and DNA polymers with a record value of DDT M = 41°C, and a small destabilisation of the DNA. The copper complexes exhibit nuclease activity; with plasmid DNA nicking was increased by one complex by a factor of k/k un = 10 7 . Experiments with hydroxyl radical quenchers indicate a predominant redox cleavage mechanism. © 2001 Elsevier Science B.V. All rights reserved.
    Inorganica Chimica Acta 05/2001; 316(s 1–2). DOI:10.1016/S0020-1693(01)00380-2 · 2.04 Impact Factor
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    ABSTRACT: Two polyammonium macrocyclic receptors, the monocyclic 3,6,9,17,20,23-hexaazatricyclo [23.3.1.1]triaconta-1(29), 11,13,15(30),25,27-hexaene (L) and its bicyclic analog 1,4,12,15,18,26,31,39-octaazapentacyclo[13.13.13.1. 1.1]-tetratetraconta-6,7,9,20(43),21,23,33(42),34,36-nonaene (L), have been synthesized as their hexatosylate salts. The propensity for binding fluoride ion was examined using both NMR and potentiometric techniques. The fluoride salts of both receptors have been characterized by X-ray crystallographic methods. For the monocycle, the complex crystallized as the mixed fluoride-bifluoride salt, [H6L] ·4F ·2FHF ·4H2O, and the bicycle crystallized as a complex salt, [H6L] ·F ·2FHF ·1.5SiF6 ·7H2O.
    Supramolecular Chemistry 05/2001; 13(3-3):405-417. DOI:10.1080/10610270108029457 · 2.13 Impact Factor
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    ABSTRACT: The interaction in aqueous solution of the cyclophane receptors 2,6,10,13,17,21-hexaaza[22]orthocyclophane (L-1) and 2,6,10,13,17,21-hexaaza[22]paracyclophane (L-2) with the nucleotides ATP, ADP and AMP has been studied by pH titration and NMR. The obtained results are compared with those previously reported for the analogous meta-substituted receptor 2,6,10,13,17,21-hexaaza[22]metacyclophane (L). All the experimental data support the actuation of these cyclophane molecules as multi-point binders of nucleotides through electrostatic, hydrogen bonding and pi-stacking interactions. The combined use of NMR and molecular dynamics permits us to get a rather reliable picture of the way in which the molecules organise in solution and how the intermolecular interactions (electrostatics, hydrogen bonding, pi-stacking) are established.
    01/2000; DOI:10.1039/b000118j