Ab initio electronic structure-property-function calculations of Fe8S9(SH)2 as a model for nitrogenase cofactor

INOR 902

Michael R Philpott, philpott@imr.edu, Center for Computational Materials Science, Tohoku University, Institute for Materials Research, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan, R. L. Jaffe, rjaffe@mail.arc.nasa.gov, NASA Ames Research Center, Mail Stop 230-3, Moffet Field, CA 94035, and Yoshiyuki Kawazoe, kawazoe@imr.edu, Tohoku University, Institute for Materials Research, 2-1-1 Katahira, Aoba-ku, Sendai, 980-8577, Japan.
We report ab initio DFT calculations of structure-property-function of the neutral molecule Fe8S9(SH)2 considered as a model for aspects of the nitrogenase cofactor responsible for nitrogen fixation. Results are presented for: states with total electronic spin S = 0 to S = 5 (10 unpaired electrons), derivatives with atoms and diatomic molecules in the endohedral cavity (C, N, O, S, N2), and metal Fe atoms substituted by Mo, V or Ru. The molecular geometry and pattern of iron spins varies with total spin. Substitution of a terminal iron by molybdenum or vanadium results in a low spin site. Atoms C, N, O or S in the iron prism cavity bond strongly to the closest metal atoms and alter the spin. For diatomic nitrogen oriented axially, each N atom binds to three iron atoms. Diatomic H2 is dissociated.
 

Computational Chemistry
8:30 AM-12:10 PM, Wednesday, 13 September 2006 Moscone Center -- Room 305, Oral

Division of Inorganic Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006