pK(a) values for the hydroxamic acid, alpha-NH3+, and epsilon-NH3+ groups of L-lysinehydroxamic acid (LyHA, H3L2+) were found to be 6.87, 8.89, and 10.76, respectively, in aqueous solution (I = 0.1 M, NaClO4) at 25 degreesC. O,O coordination to Fe(III) by LyHA is supported by H+ stoichiometry, UV-vis spectral shifts, and a shift in nu(CO) from 1648 to 1592 cm(-1) upon formation of mono(L-lysinehydroxamato)tetra(aquo)iron(III) (Fe(H2L)(H2O)(4)(4+)). The stepwise formation of tris(L-lysinehydroxamato)iron(III) from Fe(H2O)(6)(3+) and H3L2+ was characterized by spectrophotometric titration, and the values for log beta(1), log beta(2), and log beta(3) are 6.80(9), 12.4(2), and 16.1(2), respectively, at 25 degreesC and I = 2.0 M (NaClO4). Stopped-flow spectrophotometry was used to study the proton-driven stepwise ligand dissociation kinetics of tris(L-lysinehydroxamato)iron(III) at 25 degreesC and I = 2.0 M (HClO4/NaClO4). Defining k(n) and k(-n) as the stepwise ligand dissociation and association rate constants and n as the number of bound LyHA ligands, k(3), k(-3), k(2), k(-2,) k(1), and k(-1) are 3.0 X 10(4), 2.4 x 10(1), 3.9 x 10(2), 1.9 x 10(1), 1.4 x 10(-1), and 1.2 x 10(-1) M-1 s(-1), respectively. These rate and equilibrium constants are compared with corresponding constants for Fe(Ill) complexes of acetohydroxamic acid (AHA) and N-methylacetohydroxamic acid (NMAHA) in the form of a linear free energy relationship. The role of electrostatics in these complexation reactions to form the highly charged Fe(LyHA)(3)(6+) species is discussed, and an interchange mechanism mediated by charge repulsion is presented. The reduction potential for tris(L-lysinehydroxamato)iron(III) is -214 mV (vs NHE), and a comparison to other hydroxamic acid complexes of Fe(Ill) is made through a correlation between E-1/2 and pFe.