Proton-Coupled O−O Activation on a Redox Platform Bearing a Hydrogen-Bonding Scaffold
摘要:
Porphyrin architectures bearing a hydrogen-bonding scaffold have been synthesized. The H-bond pendant allows proton-coupled electron transfer (PCET) to be utilized as a vehicle for effecting catalytic O-O bond activation chemistry. Suzuki cross-coupling reactions provide a modular synthetic strategy for the attachment of porphyrins to a rigid xanthene or dibenzofuran pillar bearing the H-bond pendant. The resulting HPX (hanging porphyrin xanthene) and HPD (hanging porphyrin dibenzofuran) systems permit both the orientation and acid-base properties of the hanging H-bonding group to be controlled. Comparative reactivity studies for the catalase-like disproportionation of hydrogen peroxide and the epoxidation of olefins by the HPX and HPD platforms with acid and ester hanging groups reveal that the introduction of a proton-transfer network, properly oriented to a redox-active platform, can orchestrate catalytic O-O bond activation. For the catalase and epoxidation reaction types, a marked reactivity enhancement is observed for the xanthene-bridged platform appended with a pendant carboxylic acid group, establishing that this approach can yield superior catalysts to analogues that do not control both proton and electron inventories.
Examination of the Magneto-Structural Effects of Hangman Groups on Ferric Porphyrins by EPR
作者:Joscha Nehrkorn、Shannon A. Bonke、Azar Aliabadi、Matthias Schwalbe、Alexander Schnegg
DOI:10.1021/acs.inorgchem.9b02348
日期:2019.10.21
allowed the determination of zero-field splitting parameters, revealing minor rhombicity E/D and D values in a narrow range of 6.24(8) to 6.85(5) cm–1. Thus, the hangman porphyrins display D values in the expected range for ferric porphyrin chlorides, though D appears to be correlated with the Fe–Cl bond length. Extrapolating this trend to the ferric hangman porphyrin chlorides, for which no crystal structure
2<sup>nd</sup> coordination sphere controlled electron transfer of iron hangman complexes on electrodes probed by surface enhanced vibrational spectroscopy
作者:H. K. Ly、P. Wrzolek、N. Heidary、R. Götz、M. Horch、J. Kozuch、M. Schwalbe、I. M. Weidinger
DOI:10.1039/c5sc02560e
日期:——
Surface enhanced vibrational spectroscopy shows the correlation between electron transfer kinetics and protonation degree of Fe Hangman complexes on electrodes.