title: BODIPY-based hydroxyaryl derivatives as fluorescent pH probes.
abstract: [structures: see text] Seven new 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY) dyes with phenolic or naphtholic subunits on position 8 and with substituents having different electron driving forces on positions 3 and 5 were synthesized. Their absorption and steady-state fluorescence properties were investigated as a function of solvent. The novel compounds, with the exception of 4,4-difluoro-8-(4-hydroxyphenyl)-3,5-bis-(4-methoxyphenyl)-4-bora-3a,4a-diaza-s-indacene, are characterized by absorption maxima in the range 493-515 nm and small (400-600 cm(-1)) Stokes shifts. The exceptional dye has absorption maxima in the 570-580 nm region and fluorescence emission maxima around 610-620 nm, depending on the solvent. In aqueous solution, the dyes show a large fluorescent enhancement upon increasing the acidity of the solution. They can be used in aqueous solution as fluorescent pH probes excitable with visible light, with pKa values ranging from 7.5 to 9.3, depending on the substitution pattern on positions 3, 5, and 8.
authors.affiliation: Department of Chemistry, Katholieke Universiteit Leuven, 3001 Leuven, Belgium.
authors.forename: Mukulesh
authors.initials: M
authors.lastname: Baruah
authors.forename: Wenwu
authors.initials: W
authors.lastname: Qin
authors.forename: Nikola
authors.initials: N
authors.lastname: Basarić
authors.forename: Wim M
authors.initials: WM
authors.lastname: De Borggraeve
authors.forename: Noël
authors.initials: N
authors.lastname: Boens
mesh_terms: D001896:Boron Compounds / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D009284:Naphthols / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism; D019800:Phenol / Q000138:chemical synthesis / Q000737:chemistry* / Q000378:metabolism
chemical_list: C095489:4,4-difluoro-4-bora-3a,4a-diaza-s-indacene; D001896:Boron Compounds; D005456:Fluorescent Dyes; D009284:Naphthols; D019800:Phenol