|Ph.D Student||Luobeznov Inna|
|Subject||Activation of Small Molecules by Low Valent|
Corrole Metal Complexes
|Department||Department of Chemistry||Supervisor||Professor Zeev Gross|
|Full Thesis text|
In this research we have demonstrated the synthesis and characterizations of new corrole metal complexes for activation of small molecules. Exploration of the catalytic properties of the new complexes focused on the activation of three most important small molecules in biology: N2, NO, O2.
Our interest in activation of dinitrogen led us to synthesize and to study the vanadium(IV) complexes of corroles. We found that the new (oxo)vanadium(IV) complex (2) is rather unusual. The EPR spectrum of 2 revealed a rich signal consistent with a VIV(O) (d1, S = 1/2) corrole species. Complex 2 did undergo one reversible oxidation at Epa= 0.68 V and Epc = 0.47 V and one highly irreversible reduction at Epc = -0.4 V, under aerobic atmosphere. The reduction was assigned to a VIV/III process. Replacing Air by N2 led to a very large increase in the catalytic current at Epc= -0.4 V. Electrolysis of (Htpfc)VIV(O) solution that were saturated with N2 resulted in the consumption of many electrons per VIV, indicative of catalytic reduction of coordinated N2 by the reduced vanadium corrole.
The bis-formylated iron(III) corrole (Fe[tpfc(CHO)2] (10) was prepared for its utilization as sensing component for NO gas. The direct reaction between Fe[tpfc(CHO)2] in the solid state and gaseous NO provided a new iron complex (11). Complex 11 was independently prepared and characterized by UV-vis and NMR spectroscopy methods, as a diamagnetic (nitrosyl)iron complex.
We have also prepared and characterized antimony corroles and checked their potency for photocatalytic activation of O2. The reaction products from the treatment of H3(tpfc) with SbCl3 was isolated as the pyridine-coordinated antimony(III) corrole (12). The (oxo)antimony(V) corrole (13) was obtained in quantitative yields by either slow aerobic or fast chemical oxidation of 12. Treatment of either 12 or 13 with aqueous HF led to the isolation of trans-difluoroantimony(V) complex (14). All three antimony corroles displayed high activity and selectivity in the photocatalytic oxidation of thioanisole by molecular oxygen. Allylic and tertiary benzylic CH bonds were also oxidized under those conditions, with absolute selectivity to the corresponding hydroperoxides. All evidence pointed toward singlet oxygen as the sole oxidant in these reactions.