title: Triggered dye release via photodissociation of nitric oxide from designed ruthenium nitrosyls: turn-ON fluorescence signaling of nitric oxide delivery.
abstract: Two new fluorescein-tethered nitrosyls derived from designed tetradentate ligands with carboxamido-N donors have been synthesized and characterized by spectroscopic techniques. These two diamagnetic {Ru-NO}(6) nitrosyls, namely, [(Me(2)bpb)Ru(NO)(FlEt)] (1-FlEt, Me(2)bpb = 1,2-bis(pyridine-2-carboxamido)5-dimethylbenzene, FlEt = fluorescein ethyl ester) and [((OMe)(2)IQ1)Ru(NO)(FlEt)] (2-FlEt, (OMe)(2)IQ1 = 1,2-bis(isoquinoline-1-carboxamido)-4,5-dimethoxybenzene), display NO stretching frequencies (ν(NO)) at 1846 and 1832 cm(-1) in addition to their FlEt carbonyl stretching frequencies (ν(CO)) at 1715 and 1712 cm(-1), respectively. Coordination of the dye ligand enhances the absorptivity and NO photolability of these two nitrosyls in the visible region (450-600 nm) of light. Exposure to visible light promotes rapid loss of NO from both {Ru-NO}(6) nitrosyls to generate Ru(III) photoproducts in dry aprotic solvents, such as MeCN and DMF. The FlEt(-) moiety remains bound to the paramagnetic Ru(III) center in such cases, and hence, the photoproducts exhibit very weak fluorescence from the dye unit. In the presence of water, the Ru(III) photoproducts undergo further aquation and loss of the FlEt(-) moiety via protonation. These steps lead to turn-ON fluorescence (from the free FlEt unit) and provide a visual signal of the NO photorelease from 1-FlEt and 2-FlEt in aqueous media.
authors.affiliation: Department of Chemistry and Biochemistry, University of California, Santa Cruz, California 95064, USA.
authors.forename: Nicole L
authors.initials: NL
authors.lastname: Fry
authors.forename: Julia
authors.initials: J
authors.lastname: Wei
authors.forename: Pradip K
authors.initials: PK
authors.lastname: Mascharak
mesh_terms: D019793:Fluorescein / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D009942:Organometallic Compounds / Q000737:chemistry*; D010782:Photolysis; D012428:Ruthenium / Q000737:chemistry*
chemical_list: D005456:Fluorescent Dyes; D009942:Organometallic Compounds; D009569:Nitric Oxide; D012428:Ruthenium; D019793:Fluorescein