title: Comparative photo-release of nitric oxide from isomers of substituted terpyridinenitrosylruthenium(II) complexes: experimental and computational investigations.
abstract: The 4'-(2-fluorenyl)-2,2':6',2''-terpyridine (FT) ligand and its cis(Cl,Cl)- and trans(Cl,Cl)-[Ru(II)(FT)Cl2(NO)](PF6) complexes have been synthesized. Both isomers were separated by HPLC and fully characterized by (1)H and (13)C NMR. The X-ray diffraction crystal structures were solved for FT (Pna21 space group, a = 34.960(4), b = 5.9306(7), c = 9.5911(10) Å), and trans(Cl,Cl)-[Ru(II)(FT)Cl2(NO)](PF6)·MeOH (P1[combining macron] space group, a = 10.3340(5), b = 13.0961(6), c = 13.2279(6) Å, α = 72.680(2), β = 70.488(2), γ = 67.090(2)°). Photo-release of NO˙ radicals occurs under irradiation at 405 nm, with a quantum yield of 0.31 and 0.10 for cis(Cl,Cl)-[Ru(II)(FT)Cl2(NO)](PF6) and trans(Cl,Cl)-[Ru(II)(FT)Cl2(NO)](PF6), respectively. This significant difference is likely due to the trans effect of Cl(-), which favors the photo-release. UV-visible spectroscopy and cyclic voltammetry indicate the formation of ruthenium(iii) species as photoproducts. A density functional theory (DFT) analysis provides a rationale for the understanding of the photo-physical properties, and allows relating the weakening of the Ru-NO bond, and finally the photo-dissociation, to HOMO → LUMO excitations.
authors.affiliation: Laboratoire de Chimie de Coordination du CNRS, 205 route de Narbonne, F-31077 Toulouse, France. pascal.lacroix@lcc-toulouse.fr isabelle.malfant@lcc-toulouse.fr.
authors.forename: Joëlle
authors.initials: J
authors.lastname: Akl
authors.forename: Isabelle
authors.initials: I
authors.lastname: Sasaki
authors.forename: Pascal G
authors.initials: PG
authors.lastname: Lacroix
authors.forename: Isabelle
authors.initials: I
authors.lastname: Malfant
authors.forename: Sonia
authors.initials: S
authors.lastname: Mallet-Ladeira
authors.forename: Patricia
authors.initials: P
authors.lastname: Vicendo
authors.forename: Norberto
authors.initials: N
authors.lastname: Farfán
authors.forename: Rosa
authors.initials: R
authors.lastname: Santillan
mesh_terms: D018360:Crystallography, X-Ray; D009569:Nitric Oxide / Q000032:analysis*; D055668:Photochemical Processes; D056951:Photoelectron Spectroscopy / Q000379:methods; D011725:Pyridines / Q000032:analysis* / Q000737:chemistry; D012428:Ruthenium / Q000032:analysis* / Q000737:chemistry; D014961:X-Ray Diffraction
chemical_list: D011725:Pyridines; D009569:Nitric Oxide; D012428:Ruthenium