%0 Journal Article %1 Pohl.1988 %A Pohl, Klaus %A Wieghardt, Karl %A Kaim, Wolfgang %A Steenken, Steen. %D 1988 %J Inorganic Chemistry %K deprotonation iron kinetics perchlorate pulsed reactivity;oxidn redox triazacyclononane triazacyclononane;disproportionation triazacyclononane;iron triazacyclononane;photolysis triazacyclononane;radiolysis triazacyclononane;safety %N 3 %P 440--447 %R 10.1021/ic00276a003 %T Redox reactivity of bis(1,4,7-triazacyclononane)iron(II/III) complexes in alkaline solution and characterization of a deprotonated species: Amidoiron(III) vs aminyliron(II) ground-state formulation. EPR, kinetic, pulse radiolysis, and laser photolysis study %V 27 %X The redox reactivity of low-spin Fe(H3L)23+ and Fe(H3L)22+ (H3L = 1,4,7-triazacyclononane) in alk. aq. soln. was studied. Orange FeIII(H3L)23+ is reversibly deprotonated (pKa = 11.4 $\pm$ 0.4) in alk. soln. to yield a deep blue species, which was characterized by its frozen-soln. EPR spectrum as the low-spin amidoiron(III) complex, FeII(H3L)(H2L)2+. The aminyl radical Fe(II) formation, FeIIH3L(H2L)2+, is proposed to be an electronically excited state (ligand-to-metal charge transfer). FeIII(H3L)(H2L)2+ disproportionates slowly under anaerobic conditions to yield FeII(H3L)22+ and probably FeII(H3L)(OH2)32+ and a 2-electron-oxidn. product of 1 H3L, which was not characterized. In the presence of an external oxidant (H2O2 or O) the blue species decomps. to produce quant. 1 equiv of oxidized macrocycle and FeIII(H3L)(OH2)33+. The kinetics of both reactions were measured. Pulse radiolysis expts. have shown that the oxidn. of Fe(H3L)22+ with Br2.bul.-, I2.bul.- and (SCN)2.bul.- and O-centered radicals such as OH.bul. and the phenoxy radical yield FeIII(H3L)3+ at nearly diffusion controlled rates at pH 4-10. At higher pH values (11-13) the blue amidoiron(III) species is formed. FeIII(H3L)(H2L)2+ oxidizes ascorbate(2-) to give FeII(H3L22+ and the ascorbate(1-) radical. Laser photolysis of solns. of FeL22+ at pH 8-10 with 20-ns pulses from a KrF excimer laser (l = 248 nm) produces Fe(H3L23+ and the hydrated electron with a quantum yield of 0.9; at pH \textgreater10 Fe(H3L)(H2L)2+ and e-(aq) are produced at the same rate. on SciFinder(R)

@article{Pohl.1988, abstract = {The redox reactivity of low-spin [Fe(H3L)2]3+ and [Fe(H3L)2]2+ (H3L = 1,4,7-triazacyclononane) in alk. aq. soln. was studied. Orange [FeIII(H3L)2]3+ is reversibly deprotonated (pKa = 11.4 $\pm$ 0.4) in alk. soln. to yield a deep blue species, which was characterized by its frozen-soln. EPR spectrum as the low-spin amidoiron(III) complex, [FeII(H3L)(H2L)2+. The aminyl radical Fe(II) formation, [FeIIH3L(H2L)]2+, is proposed to be an electronically excited state (ligand-to-metal charge transfer). [FeIII(H3L)(H2L)]2+ disproportionates slowly under anaerobic conditions to yield [FeII(H3L)2]2+ and probably [FeII(H3L)(OH2)3]2+ and a 2-electron-oxidn. product of 1 H3L, which was not characterized. In the presence of an external oxidant (H2O2 or O) the blue species decomps. to produce quant. 1 equiv of oxidized macrocycle and [FeIII(H3L)(OH2)3]3+. The kinetics of both reactions were measured. Pulse radiolysis expts. have shown that the oxidn. of [Fe(H3L)2]2+ with Br2.bul.-, I2.bul.- and (SCN)2.bul.- and O-centered radicals such as OH.bul. and the phenoxy radical yield [FeIII(H3L)]3+ at nearly diffusion controlled rates at pH 4-10. At higher pH values (11-13) the blue amidoiron(III) species is formed. [FeIII(H3L)(H2L)2+ oxidizes ascorbate(2-) to give [FeII(H3L2]2+ and the ascorbate(1-) radical. Laser photolysis of solns. of [FeL2]2+ at pH 8-10 with 20-ns pulses from a KrF excimer laser (\textgreek{l} = 248 nm) produces [Fe(H3L2]3+ and the hydrated electron with a quantum yield of 0.9; at pH {\textgreater}10 [Fe(H3L)(H2L)]2+ and e-(aq) are produced at the same rate. [on SciFinder(R)]}, added-at = {2022-06-15T11:26:56.000+0200}, author = {Pohl, Klaus and Wieghardt, Karl and Kaim, Wolfgang and Steenken, Steen.}, biburl = {https://puma.ub.uni-stuttgart.de/bibtex/2732beb7755e9d66a821446ce524f56d9/huebleriac}, doi = {10.1021/ic00276a003}, interhash = {d484ffef07fe45836c198a459aa29bfb}, intrahash = {732beb7755e9d66a821446ce524f56d9}, issn = {0020-1669}, journal = {Inorganic Chemistry}, keywords = {deprotonation iron kinetics perchlorate pulsed reactivity;oxidn redox triazacyclononane triazacyclononane;disproportionation triazacyclononane;iron triazacyclononane;photolysis triazacyclononane;radiolysis triazacyclononane;safety}, number = 3, pages = {440--447}, timestamp = {2022-06-15T09:26:56.000+0200}, title = {Redox reactivity of bis(1,4,7-triazacyclononane)iron(II/III) complexes in alkaline solution and characterization of a deprotonated species: Amidoiron(III) vs aminyliron(II) ground-state formulation. EPR, kinetic, pulse radiolysis, and laser photolysis study}, volume = 27, year = 1988 }