title: New perspectives on iron-ligand vibrations of oxyheme complexes.
abstract: We report our studies of the vibrational dynamics of iron for three imidazole-ligated oxyheme derivatives that mimic the active sites of histidine-ligated heme proteins complexed with dioxygen. The experimental vibrational data are obtained from nuclear resonance vibrational spectroscopy (NRVS) measurements conducted on both powder samples and oriented single crystals, and which includes several in-plane (ip) and out-of-plane (oop) measurements. Vibrational spectral assignments have been made through a combination of the oriented sample spectra and predictions based on density functional theory (DFT) calculations. The two Fe-O(2) modes that have been previously observed by resonance Raman spectroscopy in heme proteins are clearly shown to be very strongly mixed and are not simply either a bending or stretching mode. In addition, a third Fe-O(2) mode, not previously reported, has been identified. The long-sought Fe-Im stretch, not observed in resonance Raman spectra, has been identified and compared with the frequencies observed for the analogous CO and NO species. The studies also suggest that the in-plane iron motion is anisotropic and is controlled by the orientation of the Fe-O(2) group and not sensitive to the in-plane Fe-N(p) bonds and/or imidazole orientations.
authors.affiliation: Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
authors.forename: Jianfeng
authors.initials: J
authors.lastname: Li
authors.forename: Qian
authors.initials: Q
authors.lastname: Peng
authors.forename: Alexander
authors.initials: A
authors.lastname: Barabanschikov
authors.forename: Jeffrey W
authors.initials: JW
authors.lastname: Pavlik
authors.forename: E Ercan
authors.initials: EE
authors.lastname: Alp
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Sturhahn
authors.forename: Jiyong
authors.initials: J
authors.lastname: Zhao
authors.forename: Charles E
authors.initials: CE
authors.lastname: Schulz
authors.forename: J Timothy
authors.initials: JT
authors.lastname: Sage
authors.forename: W Robert
authors.initials: WR
authors.lastname: Scheidt
mesh_terms: D006420:Hemeproteins / Q000737:chemistry* / Q000378:metabolism; D007093:Imidazoles / Q000737:chemistry*; D007501:Iron / Q000737:chemistry*; D008024:Ligands; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011166:Porphyrins / Q000737:chemistry*; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D006420:Hemeproteins; D007093:Imidazoles; D008024:Ligands; D011166:Porphyrins; D007501:Iron; D010100:Oxygen