Reduction potentials of heterometallic manganese–oxido cubane complexes modulated by redox-inactive metals

Abstract

Understanding the effect of redox-inactive metals on the properties of biological and heterogeneous water oxidation catalysts is important both fundamentally and for improvement of future catalyst designs.

Redox-inactive metal ions modulate the reactivity and oxygen release of mononuclear non-haem iron(III)–peroxo complexes

“…Alternatively, the [(TMC)Fe III (μ,η 2 :η 2 -O 2 )] + –M n + complexes could be prepared by replacing the Ca 2+ ion of 1-Ca 2+ with redox-inactive metal ions of a stronger Lewis acidity (for example, Zn 2+ , Lu 3+ , Y 3+ and Sc 3+ ) (equation (4); see the Supplementary Experimental Section), which is similar to the substitution of the Ca 2+ ion by metal ions with a stronger Lewis acidity reported for heterometallic manganese–oxido clusters as a synthetic model of OEC 8–10 . The [(TMC)Fe III (μ,η 2 :η 2 -O 2 )] + –M n + ( 1 -M n + ) complexes were characterized with high confidence using various spectroscopic methods (see insets of Fig.…”

Artificial Photosynthesis: Molecular Systems for Catalytic Water Oxidation

“…For the cubane [MMn 3 O 4 ] complexes, the redox potentials were decreased by almost 1000 mV as compared to the previously characterized dioxido complexes [MMn 3 O 2 ] 608. …”

“…607 Also, heterometallic complexes of the type [MMn 3 O 4 ] (M = Sr 2+ , Zn 2+ , Sc 3+ , Y 3+ ) were prepared, containing a structural motif that was more structurally relevant to the OEC than the core in the previously synthesized dioxido complexes ( Figures 120 and 121). 608 It was of interest to see if these newly developed cubane-type complexes exhibited a correlation between the Lewis acidity of the redox-inert metal and the redox potential. Plotting the Lewis acidity of the redox-inactive metal against the redox potentials for the [MMn 3 IV O 4 ] complexes revealed a correlation, with a slope of ∼100 mV per pK a unit.…”

Effect of the Mn Oxidation State on Single-Molecule-Magnet Properties: MnIII vs MnIV in Biologically Inspired DyMn3O4 Cubanes

“…5b,c The reduced species ([LY III Mn IV 2 Mn III O 4 (OAc) 3 (DMF)] ( 2-Y ) and [LDy III Mn IV 2 Mn III O 4 (OAc) 3 (DMF) 2 ] ( 2-Dy )) were prepared by the treatment of a tetrahydrofuran (THF) suspension of a cationic precursor ( 1-Y and 1-Dy , respectively) with 1 equiv of decamethylferrocene (Figure 1). Single-crystal X-ray diffraction studies were performed for compounds 1-Dy , 2-Y , and 2-Dy .…”

“…Dysprosium trifluoromethanesulfonate (Dy(OTf) 3 ) and decamethylferrocene were purchased from Strem, and yttrium trifluoromethanesulfonate (Y-(OTf) 3 ) was purchased from Aldrich. [LDyMn 3 O 4 (OAc) 3 (DMF) 2 ]-[OTf] 5b and [LYMn 3 O 4 (OAc) 3 (DMF) 2 ][OTf] 5c were prepared according to previously published procedures.…”