%0 Generic
%A Stylianou, Marios
%A Drouza, Chryssoula
%A Giapintzakis, John
%A Athanasopoulos, Georgios I.
%A Keramidas, Anastasios D.
%D 2015
%T Aerial Oxidation of a VIV–Iminopyridine
Hydroquinonate Complex: A Trap for the VIV–Semiquinonate
Radical Intermediate
%U https://acs.figshare.com/articles/dataset/Aerial_Oxidation_of_a_V_sup_IV_sup_Iminopyridine_Hydroquinonate_Complex_A_Trap_for_the_V_sup_IV_sup_Semiquinonate_Radical_Intermediate/2144935
%R 10.1021/acs.inorgchem.5b00571.s007
%2 https://ndownloader.figshare.com/files/3778786
%K metal complexes
%K chlorine atoms
%K semiquinonate compound exhibits
%K VVO
%K metal ions
%K conductivity measurements
%K OH
%K VIV ion
%K UV
%K oxidation states
%K O 2.
%K H 2O
%K O 2
%K Aerial Oxidation
%K acidic pH values
%K H 2bpymah
%K electrochemical measurements
%K IR
%K VO
%K VV
%K intramolecular electron transfer
%X The
reaction of 2,5-bis[N,N′-bis(2-pyridyl-aminomethyl)aminomethyl]-p-hydroquinone (H2bpymah) with VO2+ salts in acetonitrile or water at a low pH (2.2–3.5) results
in the isolation of [{VIV(O)(Cl)}2(μ-bpymah)],
the p-semiquinonate complex [{VIV(O)(Cl)}2(μ-bpymas)](OH), the cyclic mixed-valent hexanuclear
compound [{VV(O)(μ-O)VIV(O)}(μ-bpymah)]3, and [(VVO2)2(μ-bpymah)].
[{VIV(O)(Cl)}2(μ-bpymas)](OH) is an intermediate
of the radical-mediated oxidation of [{VIV(O)(Cl)}2(μ-bpymah)] from O2. At lower pH values (2.2),
a reversible intramolecular electron transfer from the metal to the
ligand of [{VIV(O)(Cl)}2(μ-bpymas)](OH)
is induced with the concurrent substitution of chlorine atoms by the
oxygen-bridging atoms, resulting in the formation of [{VV(O)(μ-O)VIV(O)}(μ-bpymah)]3. The
metal complexes were fully characterized by X-ray crystallography,
infrared (IR) spectroscopy, and magnetic measurements in the solid
state, as well as by conductivity measurements, UV–vis spectroscopy,
and electrochemical measurements in solution. The oxidation states
of the metal ions and ligands were determined by the crystallographic
data. The [{VIV(O)(Cl)}2(μ-bpymah)]–[{VIV(O)(Cl)}2(μ-bpymas)](OH) redox process is
electrochemically reversible. The VIV ion in the semiquinonate
compound exhibits a surprisingly low oxophilicity, resulting in the
stabilization of OH– counterions at acidic pH values.
An investigation of the mechanism of this reaction reveals that these
complexes induce the reduction of O2 to H2O2, mimicking the activity of enzymes incorporating two redox-active
centers (metal–organic) in the active site.
%I ACS Publications