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2018-09-17

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Si us plau utilitzeu sempre aquest identificador per citar o enllaçar aquest document: https://hdl.handle.net/2445/127695

Ligand sequential replacement on chromium(III)-aqua complexes by L-alanine and other biological amino acids: a kinetic perspective

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https://doi.org/10.1021/acs.jpca.8b07824

Resum

The ligand sequential replacement on chromium(III)-aqua complexes by L-alanine in slightly acidic aqueous solutions (pH range: 3.55-5.61) has been kinetically followed by means of UV-Vis spectrophotometry. A two rate constant model has been applied to fit the absorbance-time data, corresponding to the formation (k1) and decay (k2) of an intermediate not reactive enough to be in steady state (long-lived intermediate). The kinetic orders of the amino acid were fractional (0.40 ± 0.03 for k1 and 0.40 ± 0.02 for k2). The two steps showed base catalysis, and the activation energies were 60 ± 3 (for k1) and 83 ± 6 (for k2) kJ mol-1. The rate constants for the coordination of the first L-alanine ligand followed the sequence CrOH2+ < Cr(OH)2+ < Cr(OH)3, Cr3+ being almost inactive. This suggests that the increase in the reaction rate with increasing pH was caused by the enhancement of the lability of the Cr(III)-aqua bonds induced by the presence of hydroxo ligands. The activation parameters for a series of ligand substitution on Cr(III)-aqua complexes by organic molecules yielded a statistically significant enthalpy-entropy linear plot with an isokinetic temperature of 296 ± 21 K.

Matèries

Crom, Cinètica química, Aminoàcids

Matèries (anglès)

Chromium, Chemical kinetics, Amino acids

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Articles publicats en revistes (Ciència dels Materials i Química Física)

Citació

PÉREZ DE BENITO, Joaquín f., MARTÍNEZ CEREZA, Guillem. Ligand sequential replacement on chromium(III)-aqua complexes by L-alanine and other biological amino acids: a kinetic perspective. _Journal of Physical Chemistry A_. 2018. Vol. 122, núm. 40, pàgs. 7962-7973. [consulta: 21 de gener de 2026]. ISSN: 1089-5639. [Disponible a: https://hdl.handle.net/2445/127695]

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