Spectroscopy and photophysics of 5-nitrotropolone in condensed media

The absorption, fluorescence and fluorescence excitation spectra, fluorescence quantum yields and fluorescence lifetimes of 5-nitrotropolone (5NT) have been measured in water at 0<pH<8, and in several glass-forming liquids of varying polarity at temperatures between 295 and 77 K. With pKa=3.3 and pKa*⩾−4.3, 5NT is much more acidic than tropolone itself and exists as the anion over a wide range of pH in aqueous media. The photophysical and kinetic parameters describing the decay of both the excited anion and the undissociated neutral molecule have been determined in various condensed media at temperatures between 77 and 298 K.