Weakly coupled transition-metal centres: high-level calculations on a model Fe(IV)-Fe(IV) system.
We briefly review different approaches to calculating the Heisenberg exchange coupling between two weakly coupled metal centres in a complex, with particular emphasis on using multiconfigurational methods to treat individually all the states that arise, without the use of symmetry breaking to obtain a mixed state in which the spins are coupled antiferromagnetically. We illustrate the multiconfigurational approach first using very accurate calculations on two weakly interacting high-spin nitrogen atoms, and then we use these very accurate results to calibrate broken-symmetry single configuration approaches, including density-functional theory with various different functionals. We then consider a dinuclear iron complex chosen to reproduce qualitatively the environment around the diiron-dioxygen "diamond core" in soluble methane monooxygenase hydroxylase. Agreement between high-level multiconfigurational methods and broken-symmetry density-functional theory is only fair.
Department of Chemistry and Centre for Scientific Computing, University of Warwick, Coventry CV4 7AL, UK. p.r.taylor@warwick.ac.uk
Peter R
PR
Taylor
D000465:Algorithms; D007501:Iron / Q000737:chemistry*; D008958:Models, Molecular; D009584:Nitrogen / Q000737:chemistry; D010100:Oxygen / Q000737:chemistry; D010105:Oxygenases / Q000737:chemistry; D028561:Transition Elements / Q000737:chemistry*
D028561:Transition Elements; C066317:ferryl iron; D007501:Iron; D010105:Oxygenases; C021555:methane monooxygenase; D009584:Nitrogen; D010100:Oxygen