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dc.contributor.authorGarcía, Begoña-
dc.contributor.authorIbeas, S.-
dc.contributor.authorLeal, J. M.-
dc.contributor.authorSecco, F.-
dc.contributor.authorVenturini, M.-
dc.contributor.authorSenent, María Luisa-
dc.contributor.authorNiño, A.-
dc.contributor.authorMuñoz, Concepción-
dc.identifierdoi: 10.1021/ic049438g-
dc.identifierissn: 0020-1669-
dc.identifier.citationInorganic Chemistry 44: 2908-2919 (2005)-
dc.description.abstractA theoretical and experimental study on the structure and deprotonation of benzohydroxamic acid (BHA) has been performed. Calculations at the RHF/cc-pVDZ level, refined by the B3LYP/AUG-cc-pVDZ method, indicate that, in the gas phase, Z amide is the most stable structure of both neutral and deprotonated BHA. 1H-1H nuclear Overhauser enhancement spectroscopy and 1H-1H correlation spectroscopy spectra in acetone, interpreted with ab initio interatomic distances, reveal that BHA is split into the Z and E forms, the [E]/[Z] ratio being 75:25 at -80°C. The formation of E-E, Z-Z, and E-Z dimers has been detected; in the presence of water, the dimers dissociate to the corresponding monomers. The rates of proton exchange within the Z and E forms and between E and Z were measured by dynamic 1H NMR in the -60 to 40°C temperature range; an increase in water content lowers the rate of exchange of the E isomer. The effect of D2O on the NMR signals indicates a fast hydrogen exchange between D2O and the E and Z amide forms. The sequence of the acid strength at low temperatures is (N)HE ≈ (O)HE < (O)HZ ≈ (N)H Z. The kinetics of complex formation between BHA and Ni2+, investigated by the stopped-flow method, show that both neutral BHA and its anion can bind Ni2+. Whereas the anion reacts at a >normal> speed, the rate of water replacement from Ni(H2O)6 2+ by neutral BHA is about 1 order of magnitude less than expected. This behavior was interpreted assuming that, in aqueous solution, BHA mainly adopts a closed (hydrogen-bonded) Z configuration, which should open (with an energy penalty) for the metal binding process to occur. © 2005 American Chemical Society.-
dc.description.sponsorshipThis work was supported by MIUR (Italy) through COFIN 2002; Ministerio de Ciencia y Tecnología (Spain), Projects BQU 2002-01061 and AYA 2002-02117; Junta de Castilla y León (Spain), Project BU 26-02; and Junta de Comunidades de CastillasLa Mancha (Spain), Grant PAI-02-001.-
dc.publisherAmerican Chemical Society-
dc.titleConformations, protonation sites, and metal complexation of benzohydroxamic acid. A theoretical and experimental study-
dc.description.versionPeer Reviewed-
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