Theoretical Study On The Redox Potential Of Several Mononuclear Iron-based Complexes

The calculation of redox potential is not only a hot topic in theoretical research,but also a powerful supplement to experimental measurement.It is difficult to calculate the redox potential of transition metal organic coordination compounds because of their complex structure,d-electron and variable valence.In order to solve this problem,the potential of thirty metal complexes were studied and a new B4(XQ3)LYP functional containing the empirical correction parameter G_xwas proposed by Galstyan and Knapp.The reduction potentials of eighteen systems have been verified by using this method,and the performance is excellent.However,the authors did not verify for simple ferrocene compounds.In this paper,we first used B4(XQ3)LYP functional to study the reduction potential of Fc⁺/Fc and its derivatives in acetonitrile solvent.We found that B3LYP was used to optimize the geometry of Fc⁺and Fc,and B3LYP,B3LYP*and?B97X-D were used to calculate E⁰of Fc⁺and Fc pairs.The results were in good agreement with the experimental values,while B4(XQ3)LYP results were in large deviation from the experimental values.The mean absolute deviation(MAD)of B4(XQ3)LYP calculated potential of ferrocene and its derivatives from the experimental value is about 0.3V,which indicates that the three parameters of the functional correction term need to be refitted for ferrocene and its derivatives.Next,we calculated the redox potentials of three hexa coordinated Fe(II/III)compounds by using B4(XQ3)LYP functional.Combined with SMD solvation model,the mean absolute deviation between the calculated results and the experimental values is 0.137 V.Among them,the calculated results of Fe(edta)^-/2-system are very good,only 11 m V higher than the experimental values.Finally,we also verified that the redox potential of high valence Fe(III/IV)=O system[Fe(TMC)O]^2+/+using B4(XQ3)LYP functional with PCM solvation model.The error between the calculation result and the experimental value is 79 m V,which proved that B4(XQ3)LYP functional is feasible to calculate the reduction potential of this system in acetonitrile solvent.