title: Dirhodium tetracarboxylate scaffolds as reversible fluorescence-based nitric oxide sensors.
abstract: We report the synthesis and characterization of dirhodium tetracarboxylate complexes [Rh(2)(mu-O(2)CR)(4)(L)(2)], with R = Me and L = dansyl-imidazole (Ds-im) or dansyl-piperazine (Ds-pip). The fluorophores coordinate to the axial sites of the dirhodium core through the imidazole or piperazine N-atom and emit only weakly when excited at 365 or 345 nm for the Ds-im and Ds-pip complexes, respectively. These fluorophore-containing complexes were investigated for their ability to elicit a fluorescence response in the presence of NO. An immediate increase in fluorescence emission of greater than 15-fold occurs when NO is admitted to solutions containing [Rh(2)(mu-O(2)CMe)(4)] and Ds-pip or Ds-im. In both systems, the fluorescence response, which arises by NO-induced displacement of the axially coordinated fluorophore, is reversible with a sensitivity of approximately 4 microM. The related dinitrosyl complexes [Rh(2)(mu-O(2)CR)(4)(NO)(2)], where R = Me, Et, or n-Pr, were prepared, structurally characterized, and found to be air-stable, losing NO upon standing in solution. Sequestration of a methylene chloride solution of the Ds-pip complex from aqueous media by a NO-permeable membrane allows for fluorescence detection of NO for potential applications in biological fluids.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
authors.forename: Scott A
authors.initials: SA
authors.lastname: Hilderbrand
authors.forename: Mi Hee
authors.initials: MH
authors.lastname: Lim
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D015374:Biosensing Techniques / Q000379:methods; D002264:Carboxylic Acids / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D007093:Imidazoles / Q000737:chemistry; D007202:Indicators and Reagents / Q000138:chemical synthesis* / Q000737:chemistry; D008958:Models, Molecular; D009569:Nitric Oxide / Q000032:analysis*; D010879:Piperazines / Q000737:chemistry; D012238:Rhodium / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D002264:Carboxylic Acids; D007093:Imidazoles; D007202:Indicators and Reagents; D010879:Piperazines; D009569:Nitric Oxide; D012238:Rhodium