Kinetics and mechanism of aluminum(III)/siderophore ligand exchange: mono(deferriferrioxamine B)aluminum(III) formation and dissociation in aqueous acid solution |
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| Institution: | 1. Dipartimento di Scienze Psicologiche, della Salute e del Territorio (DiSPUTer), Università di Chieti-Pescara, 66013 Chieti, Italy;2. Dipartimento di Biologia, Ecologia e Scienze della Terra (DiBEST), Università della Calabria, Via P. Bucci – Cubo 15B, 87036 Arcavacata di Rende, CS, Italy |
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| Abstract: | The kinetics and mechanism of a linear trihydroxamic acid siderophore (deferriferrioxamine B, H4DFB+) ligand exchange with Al(H2O)63+ to form mono(deferriferrioxamine B)aluminum(III) (Al(H2O)4H3DFB)3+ have been investigated at 25 °C over the H+] range 0.001?1.0 M and I = 2.0 M (HClO4/NaClO4) by 27Al NMR. Kinetic results are consistent with Al(H2O)4(H3DFB)3+ formation and dissociation proceeding through a parallel path mechanistic scheme involving Al(H2O)63+(k2/k?1) and Al(H2O)5(OH)2+(k2/k?2) where k1 = 0.13 M?1 s?1, k?1 = 8.7 × 10?3 M?1 s?1, k2 = 2.7 × 103 M?1 s?1, and k?2 = 9.6 × 10?4 s?1. Relative complex formation rates at Al(H2O)63+ and Al(H2O)5OH2+, and comparison with kinetic data for a series of synthetic hydroxamic acids, suggest that an interchange mechanism is operative. These results are also discussed in relation to kinetic data for the corresponding iron(III)-deferriferrioxamine B system. |
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