title: Ultrafast photoinduced dynamics of the 3,6-diaminoacridinium derivative ATTO 465 in solution.
abstract: The excited state dynamics of the dye ATTO 465, a well-known fluorescence marker for biological applications, have been characterized in various solvents including THF, ethanol, methanol, water and the highly polar protic ionic liquid 2-hydroxyethylammonium formate (2-OH-EAF) by combining results from time-correlated single-photon counting (TCSPC) and ultrafast pump-supercontinuum probe (PSCP) spectroscopy as well as steady-state absorption and fluorescence. In water, 2-OH-EAF and two fluorinated alcohols, there is a pronounced blue-shift and broadening of the S(0) → S(1) absorption band and also a larger Stokes shift than in the other solvents, indicating a particular influence of hydrogen-bonding interactions. S(1) lifetimes from TCSPC at 25 °C range from 3.3 ns to 5.6 ns. An unusual increase in the S(1) lifetime with temperature is observed for ethanol and methanol, however water behaves in the opposite way. The behavior can be tentatively explained by a solvent- and temperature-dependent "proximity effect", where coupling of the close-lying S(1) and S(2) states influences the intramolecular relaxation rate of the dye. In addition, temperature-dependent complex equilibria of ATTO 465 with solvent molecules may influence the measured lifetimes. Several excited-state absorption (ESA) transitions are identified in the PSCP spectra, which are in good agreement with the position of the UV bands in the steady-state absorption spectra. Small shifts of the stimulated emission and ESA bands are consistent with solvation dynamics in the excited electronic state. An additional ~16 ps component in water, visible over the entire spectral range, is tentatively ascribed to a fast IC channel which is accessed by a fraction of ATTO 465 molecules.
authors.affiliation: Universität Siegen, Physikalische Chemie, Adolf-Reichwein-Str. 2, 57076 Siegen, Germany.
authors.forename: Jutta
authors.initials: J
authors.lastname: Arden-Jacob
authors.forename: Karl-Heinz
authors.initials: KH
authors.lastname: Drexhage
authors.forename: Sergey I
authors.initials: SI
authors.lastname: Druzhinin
authors.forename: Maria
authors.initials: M
authors.lastname: Ekimova
authors.forename: Oliver
authors.initials: O
authors.lastname: Flender
authors.forename: Thomas
authors.initials: T
authors.lastname: Lenzer
authors.forename: Kawon
authors.initials: K
authors.lastname: Oum
authors.forename: Mirko
authors.initials: M
authors.lastname: Scholz
mesh_terms: D000609:Aminoacridines / Q000737:chemistry*; D005456:Fluorescent Dyes / Q000737:chemistry*; D006860:Hydrogen Bonding; D052578:Ionic Liquids / Q000737:chemistry; D011370:Proflavine / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory; D012997:Solvents / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013696:Temperature
chemical_list: C582139:ATTO 465; D000609:Aminoacridines; D005456:Fluorescent Dyes; D052578:Ionic Liquids; D012997:Solvents; D011370:Proflavine