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Photophysics and stability of cyano-substituted boradiazaindacene dyes.
Autorzy
Rok wydania
2009
Czasopismo
Photochemical and Photobiological Sciences
Numer woluminu
8
Strony
1006-1015
DOI
10.1039/b905054j
Kolekcja
Język
Angielski
Typ publikacji
Artykuł
The solvatochromic photophysical properties of two fluorescent, cyano-substituted BODIPYdyes—8-(4-bromophenyl)-3,4,4,5-tetracyano-4-bora-3a,4a-diaza-s-indacene (4CN)and8-(4-bromophenyl)-3,5-dicyano-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (2CN)—have been studiedin various solvents by UV–vis spectrophotometry and steady-state and time-resolved fluorometry.These two BODIPY analogues have comparable photophysical properties, implying that displacementof F by CN at boron has a negligible effect. Both compounds have high fluorescence quantum yieldsUf(0.65–0.90 for4CNand 0.63–0.88 for2CN) in the solvents studied and display mono-exponentialfluorescence decay profiles in nonprotic solvents. A new, generalized treatment of the solvent effectbased on four mutually independent, empirical solvent scales (dipolarity, polarizability, acidity, andbasicity of the medium) indicates that solvent polarizability and, to a lesser degree, solvent (di)polarityare crucial factors causing the solvent-dependent shifts of the UV–vis absorption and fluorescenceemission. The rate constants of radiative deactivation (kf) are nearly independent of the nonproticsolvent [kf=(1.4±0.1)¥108s-1for4CNand (1.5±0.2)¥108s-1for2CN]. Both compounds undergo acolor change in polar aprotic solvents (acetone, acetonitrile, andN,N-dimethylformamide), which canbe stopped by addition of HClO4. The kinetics of this color change indicates that the decomposition ofthese cyano-substituted BODIPY compounds is complex.
Adres publiczny
http://doi.org/10.1039/b905054j