title: Role of ligand bending in the photodissociation of O2 vs CO-heme: a time-dependent density functional study.
abstract: Time-dependent DFT calculations reveal a strong dependence of low-lying excited states on the <Fe-O-O angle of a model O2-heme adduct and ready access to a metastable side-on isomer. The predicted state crossings provide a pathway for internal conversion to the ground state and account for the low quantum yield for O2 dissociation, while the side-on isomer can account for the observation of an unphotolyzable fraction at low temperature. For CO-heme, the angle-sensitive states lie above the photoaccessed Q state and do not participate in photodissociation.
authors.affiliation: Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA. filippo@thch.unipg.it
authors.forename: Filippo
authors.initials: F
authors.lastname: De Angelis
authors.forename: Roberto
authors.initials: R
authors.lastname: Car
authors.forename: Thomas G
authors.initials: TG
authors.lastname: Spiro
mesh_terms: D002248:Carbon Monoxide / Q000737:chemistry* / Q000378:metabolism; D006418:Heme / Q000737:chemistry* / Q000378:metabolism; D008968:Molecular Conformation; D009211:Myoglobin / Q000737:chemistry / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D010777:Photochemistry; D013816:Thermodynamics
chemical_list: D009211:Myoglobin; D006418:Heme; D002248:Carbon Monoxide; D010100:Oxygen