Variation of the ultrafast fluorescence quenching in 2,6-sulfanyl-core-substituted naphthalenediimides by electron transfer.
The ultrafast fluorescence quenching of 2,6-sulfanyl-core-substituted naphthalenediimides was investigated by transient spectroscopy. We find a strong dependence of the relaxation on the chemical structure of the substituent. Direct linking of an aryl rest to the sulfur atom leads to a strong red shift of the fluorescence in 1 ps and the disappearance of the emission in 5-7 ps depending on the polarity and viscosity of the solvent. This complex behavior is interpreted with the help of quantum chemical calculations. The calculations suggest that the initial relaxation corresponds to a planarization of the substituents and an associated partial electron transfer. This is followed by a twisting of the phenylsulfanyl substituents out of the molecular plane that allows a complete localization of the electron-donating orbital on the aryl group. Finally the back transfer happens in another 5-7 ps. For an additional methylene spacer group between the sulfur and the aryl, this sequence of relaxation steps is not possible and a simple exponential decay, slower by about 1 order of magnitude, is found.
Lehrstuhl für BioMolekulare Optik, Ludwig-Maximilians-Universität München, Germany.
Igor
I
Pugliesi
Patrizia
P
Krok
Stefan
S
Lochbrunner
Alfred
A
Błaszczyk
Carsten
C
von Hänisch
Marcel
M
Mayor
Eberhard
E
Riedle
D004579:Electron Transport; D005453:Fluorescence; D007094:Imides / Q000737:chemistry*; D008958:Models, Molecular; D056004:Molecular Dynamics Simulation; D015394:Molecular Structure; D009281:Naphthalenes / Q000737:chemistry*; D011789:Quantum Theory; D013237:Stereoisomerism; D013438:Sulfhydryl Compounds / Q000737:chemistry*
D007094:Imides; D009281:Naphthalenes; D013438:Sulfhydryl Compounds; C542131:naphthalenediimide