title: Direct observation of photoinduced bent nitrosyl excited-state complexes.
abstract: Ground-state structures with side-on nitrosyl (eta (2)-NO) and isonitrosyl (ON) ligands have been observed in a variety of transition-metal complexes. In contrast, excited-state structures with bent-NO ligands have been proposed for years but never directly observed. Here, we use picosecond time-resolved infrared spectroscopy and density functional theory (DFT) modeling to study the photochemistry of Co(CO) 3(NO), a model transition-metal-NO compound. Surprisingly, we have observed no evidence for ON and eta (2)-NO structural isomers, but we have observed two bent-NO complexes. DFT modeling of the ground- and excited-state potentials indicates that the bent-NO complexes correspond to triplet excited states. Photolysis of Co(CO) 3(NO) with a 400-nm pump pulse leads to population of a manifold of excited states which decay to form an excited-state triplet bent-NO complex within 1 ps. This structure relaxes to the ground triplet state in ca. 350 ps to form a second bent-NO structure.
authors: Department of Chemistry, University of California, Berkeley, California 94720, USA.
authors: Karma R
authors: KR
authors: Sawyer
authors: Ryan P
authors: RP
authors: Steele
authors: Elizabeth A
authors: EA
authors: Glascoe
authors: James F
authors: JF
authors: Cahoon
authors: Jacob P
authors: JP
authors: Schlegel
authors: Martin
authors: M
authors: Head-Gordon
authors: Charles B
authors: CB
authors: Harris