title: Fluorimetric detection of Mg2+ and DNA with 9-(alkoxyphenyl)benzo[b]quinolizinium derivatives.
abstract: A benzo[b]quinolizinium-benzo-15-crown-5 ether conjugate 2a is presented that enables the fluorimetric detection of Mg(2+) and DNA by a significant light-up effect, along with a change of the emission wavelength with different analytes (Mg(2+): 495 nm; DNA: 550 nm). The mechanism of the excited-state deactivation of 2a was investigated by steady-state fluorescence spectroscopy in media of varied viscosity and compared with the photophysical properties of methoxyphenyl-substituted benzo[b]quinolizinium 2b (m,p-diOMe), 2c (m-OMe), and 2d (p-OMe) as reference compounds. Compounds 2a-c, which share the m-alkoxyphenyl substituent as the common feature, have low emission quantum yields (Φ(F) < 10(-2) in water) but exhibit a significant increase of their fluorescence intensity in viscous glycerol solutions. In contrast, the viscosity of the medium does not influence the emission properties of the parent phenyl-substituted benzo[b]quinolizinium 2e and of the p-methoxyphenyl-substituted derivative 2d. Based on these observations it is concluded that the excited-state deactivation in 2a-c is mainly due to the rotation of the m-alkoxy group about the C(ar)-O bond. The interaction of 2a-c with DNA or Mg(2+) ions was studied by spectrophotometric titrations and CD spectroscopy. Notably, the association of 2a or 2b with DNA or 2a with Mg(2+) ions induces a strong fluorescence enhancement (15- and 40-fold for DNA, 450-fold for Mg(2+)), which is rationalized by the suppression of the torsional-relaxation of the alkoxy-substituent in the excited state. Additionally, the cation-induced light-up effect of 2a is selective towards Mg(2+) ions as compared with other cations such as NH(4)(+), Li(+), Na(+), K(+) and Ba(2+).
authors.affiliation: University of Siegen, Organic Chemistry II, Adolf-Reichwein-Str. 2, D-57068, Siegen, Germany.
authors.forename: Maoqun
authors.initials: M
authors.lastname: Tian
authors.forename: Heiko
authors.initials: H
authors.lastname: Ihmels
authors.forename: Shite
authors.initials: S
authors.lastname: Ye
mesh_terms: D002413:Cations, Divalent; D002942:Circular Dichroism; D043844:Crown Ethers / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D004247:DNA / Q000032:analysis*; D005453:Fluorescence; D005456:Fluorescent Dyes / Q000138:chemical synthesis*; D005990:Glycerol / Q000737:chemistry; D008274:Magnesium / Q000032:analysis*; D008958:Models, Molecular; D015394:Molecular Structure; D011807:Quinolizines / Q000138:chemical synthesis* / Q000737:chemistry; D012680:Sensitivity and Specificity; D012996:Solutions; D013050:Spectrometry, Fluorescence; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: C573535:9-(2,3,5,6,8,9,11,12-octahydro-1,4,7,10,13-benzopentaoxacyclopentadecin-15-yl)-aminobenzo(b)quinolizinium; D002413:Cations, Divalent; D043844:Crown Ethers; D005456:Fluorescent Dyes; D011807:Quinolizines; D012996:Solutions; D014867:Water; D004247:DNA; D008274:Magnesium; D005990:Glycerol