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Coordination Chemistry of Iron Porphycenes in the Presence of CO, CO2, and N-Methylimidazole: Electrochemical, ESR, and UV-Vis Study

Abstract : The electrochemical behavior of iron porphycenes in benzonitrile, tetrahydrofuran, N,N-dimethylformamide, and dichloromethane in the presence of Lewis bases is reported. This analysis combined the use of polarographic, steady-state voltammetric, cyclic voltammetric, and spectroelectrochemical methods. Iron(III) 2,7,12,17-tetran-propylporphycene ([FeIIITPrPn]Cl) is reduced in three one-electron steps and is oxidized in two one-electron steps: All the processes are reversible. The corresponding iron μ-oxo dimer [FeIIITPrPn](N-MeIm)2+O undergoes four one-electron oxidations as well as four one-electron reductions. [FeIIITPrPn]Cl forms a stable [FeIIITPrPn](N-MeIm, the iron (II) complex in the presence of N-MeIm. This complex is reduced stepwise to [FeIITPrPn]N-MeIm, the iron(II) radical anion [FeIIPrPṅ]- and the iron(II) dianion [FeIITPrPn]2- as confirmed by UV-vis and ESR spectroscopy of the electrogenerated species. In the presence of CO, the reduction of iron(III) generates [FeII(CO)TPrPn]. In contrast to porphyrins, one- and two-electron reductions of the latter compound are shifted to more negative potentials in DMF and THF and these electron transfers remain reversible. UV - vis spectroelectrochemical experiments at an optically transparent thin layer electrode (OTTLE) demonstrate that the generated species are respectively [FeII(CO)TPrPṅ]- and [FeII(CO)TPrPn]2-. This redox behavior is distinctively different from that of Fe-CO porphyrins. In the presence of CO2, electrocatalytic reduction of CO2 is observed, as for porphyrins.
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https://hal.univ-brest.fr/hal-01770740
Contributor : Nicolas Renard Connect in order to contact the contributor
Submitted on : Thursday, April 19, 2018 - 10:58:22 AM
Last modification on : Monday, December 13, 2021 - 1:36:04 PM

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  • HAL Id : hal-01770740, version 1

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C. Bernard, Y. Le Mest, J.P. Gisselbrecht. Coordination Chemistry of Iron Porphycenes in the Presence of CO, CO2, and N-Methylimidazole: Electrochemical, ESR, and UV-Vis Study. Inorganic Chemistry, American Chemical Society, 1998, 37, pp.181--190. ⟨hal-01770740⟩

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