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Red‐Emitting Dyes with Photophysical and Photochemical Properties Controlled by pH
Author(s) -
Novakova Veronika,
Miletin Miroslav,
Kopecky Kamil,
Zimcik Petr
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201101123
Subject(s) - chemistry , singlet oxygen , protonation , aniline , photochemistry , fluorescence , substituent , intramolecular force , excited state , quantum yield , sulfuric acid , singlet state , vesicle , oxygen , medicinal chemistry , inorganic chemistry , stereochemistry , organic chemistry , membrane , ion , biochemistry , physics , quantum mechanics , nuclear physics
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 p K a values were determined in DOPC vesicles and ranged between 2.2 and 4.2.