63071-06-7Relevant academic research and scientific papers
Resonance Raman investigation of equatorial ligand donor effects on the CU2O22+ core in end-on and side-on μ-peroxo-dicopper(II) and bis-μ-oxo-dicopper(III) complexes
Henson, Mark J.,Vance, Michael A.,Zhang, Christiana Xin,Hong-Chang, Liang,Karlin, Kenneth D.,Solomon, Edward I.
, p. 5186 - 5192 (2007/10/03)
The effect of endogenous donor strength on CU2O2 bonds was studied by electronically perturbing [{(R-TMPA)CuII}2(O2)]2+ and [{(R-MePY2)Cu}2(O2)]2+ (R = H, MeO, Me2N), which form the end-on μ-1,2 bound peroxide and an equilibrium mixture of side-on peroxo- dicopper(II) and bis-μ-oxo-dicopper(III) isomers, respectively. For [{(R-TMPA)CUII}2(O2)]2+, vo-o shifts from 827 to 822 to 812 cm-1 and VCu-O(sym) shifts from 561 to 557 to 551 cm-1, respectively, as R- varies from H to MeO to Me2N. Thus, increasing the N-donor strength to the copper decreases peroxide π*σ donation to the copper, weakening the Cu-O and O-O bonds. A decrease in vCu-O of the bis-μ-oxo- dicopper(III) complex was also observed with increasing N-donor strength for the R-MePY2 ligand system. However, no change was observed for vO-O of the side-on peroxo. This is attributed to a reduced charge donation from the peroxide π*σ orbital with increased N-donor strength, which increases the negative charge on the peroxide and adversely affects the back-bonding from the Cu to the peroxide σ*orbital. However, an increase in the bis-μ-oxo-dicopper(III) isomer relative to side-on peroxo-dicopper(II) species is observed for R-MePY2 with R = H 2N. This effect is attributed to the thermodynamic stabilization of the bis-μ-oxo-dicopper(III) isomer relative to the side-on peroxo-dicopper(II) isomer by strong donor ligands. Thus, the side-on peroxo-dicopper(II)/bis-μ-oxo-dicopper(III) equilibrium can be controlled by electronic as well as steric effects.
Superoxide dismutase activity of iron(II)TPEN complex and its derivatives
Tamura,Urano,Kikuchi,Higuchi,Hirobe,Nagano
, p. 1514 - 1518 (2007/10/03)
Superoxide is involved in the pathogenesis of various diseases, such as inflammation, ischemia-reperfusion injury and carcinogenesis. Superoxide dismutases (SODs) catalyze the disproportionation reaction of superoxide to produce oxygen and hydrogen peroxide, and can protect living cells against the toxicity of free radicals derived from oxygen. Thus, SODs and their functional mimics have potential value as pharmaceuticals. We have previously reported that Fe(II)tetrakis-N,N,N',N'-(2-pyridylmethyl)ethylenediamine (Fe(II)TPEN) has an excellent SOD activity (IC50=0.5 μM) among many iron complexes examined (J. Biol. Chem., 264, 9243-9249 (1989)). Fe(II)TPEN can act like native SOD in living cells, and protect Escherichia coli cells from free radical toxicity caused by paraquat. In order to develop more effective SOD functional mimics, we synthesized Fe(II)TPEN derivatives with electron-donating or electron-withdrawing groups at the 4-position of all pyridines of TPEN, and measured the SOD activities and the redox potentials of these complexes. Fe(II) tetrakis-N,N,N',N'-(4-methoxy-2-pyridylmethyl)ethylenediamine (Fe(II)(4MeO)4TPEN) had the highest SOD activity (IC50=0.1 μM) among these iron-based SOD mimics. In addition, a good correlation was found between the redox potential and the SOD activity of 15 Fe(II) complexes, including iron-based SOD mimics reported in the previous paper (J. Organometal. Chem., in press). Iron-based SOD mimics may be clinically applicable, because these complexes are generally tissue-permeable and show low toxicity. Therefore our findings should be significant for the development of clinically useful SOD mimics.
