On the unusual fluorescence properties of xanthone in water.
Photo-excited xanthone is known to undergo ultrafast intersystem crossing (ISC) in the 1 ps time domain. Correspondingly, its fluorescence quantum yield in most solvents is very small ( approximately 10(-4)). Surprisingly, the quantum yield in water is 100 times larger, while ISC is still rapid ( approximately 1 ps), as seen by ultrafast pump probe absorption spectroscopy. Temperature dependent steady state and time resolved fluorescence experiments point to a delayed fluorescence mechanism, where the triplet (3)npi* state primarily accessed by ISC is nearly isoenergetic with the photo-excited (1)pipi* state. The delayed fluorescence of xanthone in water decays with a time constant of 700 ps, apparently by internal conversion between the (3)npi* state and the lowest lying triplet state (3)pipi*.
Heinz
B
B
Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538, München, Germany.
Schmidt
B
B
Root
C
C
Satzger
H
H
Milota
F
F
Fierz
B
B
Kiefhaber
T
T
Zinth
W
W
Gilch
P
P
D049449:Luminescence; D049408:Luminescent Agents / Q000032:analysis* / Q000737:chemistry*; D012997:Solvents / Q000032:analysis / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D014867:Water / Q000032:analysis / Q000737:chemistry*; D044004:Xanthones / Q000032:analysis* / Q000737:chemistry*
D049408:Luminescent Agents; D012997:Solvents; D044004:Xanthones; D014867:Water; C009689:xanthone