Effect of amino substitution on the excited state dynamics of uracil.
The excited state deactivation of two amino-substituted uracils, 5-aminouracil (5AU) and 6-aminouracil (6AU) in aqueous solution was studied by femtosecond fluorescence upconversion. The fluorescence of 6AU decays as fast as that of uracil with a unique time constant of about 100 femtoseconds. The fluorescence of 5AU exhibits a more complex behavior, fundamentally different from what we found in any other uracils: the decays are globally slower (up to several picoseconds) and depend strongly on the wavelength. This difference is attributed to the particular character of the amino group, affecting the out-of-plane motion of the 5-substituent which has been shown to be crucial for the ultrafast internal conversion occurring in uracils. Our observations indicate instead the formation of a transient fluorescent state which in turn is deactivated by a different relaxation process specific to the amino group.
Bányász
Akos
A
Laboratoire Francis Perrin, CEA/DSM/IRAMIS/SPAM - CNRS URA 2453, Gif-sur-Yvette, France.
Gustavsson
Thomas
T
Keszei
Erno
E
Improta
Roberto
R
Markovitsi
Dimitra
D
D005453:Fluorescence; D005454:Fluorescence Polarization; D013997:Time Factors; D014498:Uracil / Q000031:analogs & derivatives* / Q000737:chemistry; D014867:Water / Q000737:chemistry
D014867:Water; D014498:Uracil; C013400:6-aminouracil; C011166:5-aminouracil