Geometric and electronic structure of the heme-peroxo-copper complex [(F8TPP)FeIII-(O22-)-CuII(TMPA)](ClO4).
The geometric and electronic structure of the untethered heme-peroxo-copper model complex [(F(8)TPP)Fe(III)-(O(2)(2)(-))-Cu(II)(TMPA)](ClO(4)) (1) has been investigated using Cu and Fe K-edge EXAFS spectroscopy and density functional theory calculations in order to describe its geometric and electronic structure. The Fe and Cu K-edge EXAFS data were fit with a Cu...Fe distance of approximately 3.72 A. Spin-unrestricted DFT calculations for the S(T) = 2 spin state were performed on [(P)Fe(III)-(O(2)(2)(-))-Cu(II)(TMPA)](+) as a model of 1. The peroxo unit is bound end-on to the copper, and side-on to the high-spin iron, for an overall mu-eta(1):eta(2) coordination mode. The calculated Cu...Fe distance is approximately 0.3 A longer than that observed experimentally. Reoptimization of [(P)Fe(III)-(O(2)(2)(-))-Cu(II)(TMPA)](+) with a 3.7 A Cu...Fe constrained distance results in a similar energy and structure that retains the overall mu-eta(1):eta(2)-peroxo coordination mode. The primary bonding interaction between the copper and the peroxide involves electron donation into the half-occupied Cu d(z)2 orbital from the peroxide pi(sigma) orbital. In the case of the Fe(III)-peroxide eta(2) bond, the two major components arise from the donor interactions of the peroxide pi*(sigma) and pi*(v) orbitals with the Fe d(xz) and d(xy) orbitals, which give rise to sigma and delta bonds, respectively. The pi*(sigma) interaction with both the half-occupied d(z)2 orbital on the copper (eta(1)) and the d(xz) orbital on the iron (eta(2)), provides an effective superexchange pathway for strong antiferromagnetic coupling between the metal centers.
Del Río
Diego
D
Department of Chemistry, Stanford University, Stanford, California 94305, USA.
Sarangi
Ritimukta
R
Chufán
Eduardo E
EE
Karlin
Kenneth D
KD
Hedman
Britt
B
Hodgson
Keith O
KO
Solomon
Edward I
EI
D003300:Copper / Q000737:chemistry; D003576:Electron Transport Complex IV / Q000737:chemistry / Q000378:metabolism; D006418:Heme / Q000737:chemistry*; D007501:Iron / Q000737:chemistry; D026901:Membrane Transport Proteins / Q000737:chemistry*; D008956:Models, Chemical; D009942:Organometallic Compounds / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D010472:Perchlorates / Q000737:chemistry*; D010545:Peroxides / Q000737:chemistry*; D013816:Thermodynamics
D026901:Membrane Transport Proteins; D009942:Organometallic Compounds; D010472:Perchlorates; D010545:Peroxides; D006418:Heme; D003300:Copper; D007501:Iron; D003576:Electron Transport Complex IV; D010100:Oxygen