title: 9-Aryl-9-xanthenols: a convenient platform for the design of fluorimetric and colorimetric pH indicators.
abstract: In aqueous and alcohol solutions, colorless and non-fluorescent derivatives of 9-aryl-9H-xanthen-9-ol equilibrate with brightly colored and fluorescent 9-arylxanthylium cations, thus offering a convenient platform for the design of dual-mode indicators for emission and absorption-based pH measurements. The position of the prototropic equilibrium depends only on the hydronium ion concentration and is not affected by general acids or other ions. Furthermore, the equilibrium equivalence point can be readily adjusted by introducing substituents in the xanthenol core. As dehydroxylation of 3,6-dialkoxy-9-(o-tolyl)-9-xanthenol occurs at pH = 6.5, indicators of this type are well suited for biological applications as illustrated by in vitro cell culture studies with NIH 3T3 cells.
authors.affiliation: Department of Chemistry, University of Georgia, Athens, Georgia 30602, USA.
authors.forename: Emmanuel E
authors.initials: EE
authors.lastname: Nekongo
authors.forename: Pritha
authors.initials: P
authors.lastname: Bagchi
authors.forename: Christoph J
authors.initials: CJ
authors.lastname: Fahrni
authors.forename: Vladimir V
authors.initials: VV
authors.lastname: Popik
mesh_terms: D000818:Animals; D001692:Biological Transport; D003124:Colorimetry; D005456:Fluorescent Dyes / Q000138:chemical synthesis*; D005470:Fluorometry; D006863:Hydrogen-Ion Concentration; D006900:Hydroxylation; D007202:Indicators and Reagents; D007700:Kinetics; D008247:Lysosomes / Q000378:metabolism / Q000648:ultrastructure; D051379:Mice; D008856:Microscopy, Fluorescence; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D041681:NIH 3T3 Cells; D012996:Solutions; D014867:Water; D014966:Xanthenes / Q000138:chemical synthesis*
chemical_list: D005456:Fluorescent Dyes; D007202:Indicators and Reagents; D012996:Solutions; D014966:Xanthenes; D014867:Water