title: Red-emitting dyes with photophysical and photochemical properties controlled by pH.
abstract: New unsymmetrical zinc azaphthalocyanines, bearing one substituted aniline as a peripheral substituent, were prepared by using a statistical condensation approach. Both fluorescence and singlet oxygen quantum yields were extremely low in DMF (Φ(F)<0.01, Φ(Δ)<0.02, respectively), but increased after the addition of sulfuric acid, reaching values comparable to controls without aniline substituents (Φ(F)=0.22-0.29, Φ(Δ)=0.40-0.59, respectively). This behavior was attributed to the deactivation of excited states by intramolecular charge transfer from a donor site (aniline), which was blocked after protonation in acidic media. In the protonated form, all of the compounds efficiently emitted light with λ(em) in the region of 662-675 nm. The investigated compounds were anchored to dioleoylphosphatidylcholine (DOPC) unilamellar vesicles and showed response to buffer pH. They were highly fluorescent at low pH values and almost nonfluorescent in neutral solutions. The pK(a) values were determined in DOPC vesicles and ranged between 2.2 and 4.2.
authors: Department of Biophysics and Physical Chemistry, Faculty of Pharmacy in Hradec Kralove, Charles University in Prague, Heyrovskeho 1203, Hradec Kralove, Czech Republic.
authors: Veronika
authors: V
authors: Novakova
authors: Miroslav
authors: M
authors: Miletin
authors: Kamil
authors: K
authors: Kopecky
authors: Petr
authors: P
authors: Zimcik
mesh_terms: D000814:Aniline Compounds / Q000737:chemistry*; D004396:Coloring Agents / Q000737:chemistry*; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D008027:Light; D015394:Molecular Structure; D010777:Photochemistry; D011789:Quantum Theory; D026082:Singlet Oxygen / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry; D013053:Spectrophotometry; D015032:Zinc / Q000737:chemistry*
chemical_list: D000814:Aniline Compounds; D004396:Coloring Agents; D012996:Solutions; D026082:Singlet Oxygen; D015032:Zinc