title: 2-Amino-7-nitro-fluorenes in neat and mixed solvents-optical band shapes and solvatochromism.
abstract: Femtosecond transient absorption spectroscopy of amino-nitro-fluorenes in the UV-visible range shows that the dynamic Stokes shift of the emission band is sensitive to infrared-active modes of the solvent. Bandshapes for stationary absorption and emission are needed to quantify the observed spectral evolution. They are reported for 2-amino-7-nitro-fluorene (ANF), 2-dimethylamino-7-nitro-fluorene (dM-ANF), and 2-di(n-butyl)amino-7-nitro-9-di(n-propyl)-fluorene (dBdP-ANF) in a variety of solvents. Bands broaden systematically with increasing solvent polarity. This effect is taken into account in an improved location of band positions. The resulting solvatochromic plots differ significantly from those that use peak positions of absorption spectra and fluorescence quantum distributions. Absorption spectra were also measured in aqueous solvent mixtures, and shifts are described by binding curves for hydrogen bonding and stepwise solvent exchange.
authors.affiliation: Department of Chemistry, Humboldt-Universität zu Berlin, Brook-Taylor-Strasse 2, D-12489 Berlin, Germany.
authors.forename: Venugopal
authors.initials: V
authors.lastname: Karunakaran
authors.forename: Tamara
authors.initials: T
authors.lastname: Senyushkina
authors.forename: Ginagunta
authors.initials: G
authors.lastname: Saroja
authors.forename: Jürgen
authors.initials: J
authors.lastname: Liebscher
authors.forename: Nikolaus P
authors.initials: NP
authors.lastname: Ernsting