title: Nitric oxide-induced fluorescence enhancement by displacement of dansylated ligands from cobalt.
abstract: The cobalt complexes [Co(Ds-AMP)(2)] (1) and [Co(Ds-AQ)(2)] (2), where Ds-AMP and Ds-AQ are the conjugate bases of dansyl aminomethylpyridine (Ds-HAMP) and dansyl aminoquinoline (Ds-HAQ), respectively, were synthesized in two steps as fluorescence-based nitric oxide (NO) sensors and characterized by X-ray crystallography. The fluorescence of the two complexes was significantly quenched in CH(3)CN or CH(3)OH compared to that of the free Ds-HAMP or Ds-HAQ ligands. Addition of NO to a CH(3)CN solution of 1 or 2 enhanced the integrated fluorescence emission by factors of 2.1(+/-0.3) or 3.6(+/-0.4) within 35 or 20 min, respectively. Introduction of NO to methanolic solutions of the complexes similarly increased the fluorescence by 1.4(+/-0.1) for 1 or 6.5(+/-1.4) for 2 within 1 h. These studies demonstrate that 1 and 2 can monitor the presence of NO with turn-on emission and that their fluorescence responses are more rapid than those of previously reported cobalt systems in coordinating solvents such as CH(3)CN and CH(3)OH. (1)H NMR and IR spectroscopic data revealed the formation of a [Co(NO)(2)](10) cobalt-dinitrosyl adduct, with concomitant dissociation of one ligand from the cobalt center, as the metal-containing product of the NO reactions, a result indicating NO-induced ligand release to be the cause of the fluorescence increase.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology Cambridge, Massachusetts 02139, USA.
authors.forename: Mi Hee
authors.initials: MH
authors.lastname: Lim
authors.forename: Chaoyuan
authors.initials: C
authors.lastname: Kuang
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Lippard
mesh_terms: D003035:Cobalt / Q000737:chemistry*; D018360:Crystallography, X-Ray; D003619:Dansyl Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D005453:Fluorescence; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry*; D013050:Spectrometry, Fluorescence
chemical_list: D003619:Dansyl Compounds; D009569:Nitric Oxide; D003035:Cobalt