Tuning the Excited-State Dynamics of GFP-Inspired Imidazolone Derivatives

Abstract

The excited-state dynamics of five derivatives of the GFP-chromophore, which differ by the position and nature of their substituents, has been investigated in solvents of various viscosity and polarity and in rigid media using femtosecond-resolved spectroscopy. In polar solvents of low viscosity, like acetonitrile or methanol, the fluorescence decays of all compounds are multiexponential, with average lifetimes of the order of a few picoseconds, whereas in rigid matrices (polymer films and low temperature glasses), they are single exponential with lifetimes of the order of a few nanoseconds and fluorescence quantum yields close to unity. Global analysis of the fluorescence decays recorded at several wavelengths and of the transient absorption spectra reveals the presence of several excited-state populations with slightly different fluorescence and absorption spectra and with distinct lifetimes. These populations are attributed to the existence of multiple ground-state conformers. From the analysis of the dependence of the excited-state dynamics on the solvent and on the nature of the substituents, it follows that the nonradiative deactivation of all these excited chromophores involves an intramolecular coordinate with large amplitude motion. However, depending on the solvent and substituent, additional channels, namely, inter-and intramolecular hydrogen bond assisted nonradiative deactivation, are operative. This allows tuning of the excited-state lifetime of the chromophore. Finally, an ultrafast photoinduced intramolecular charge transfer is observed in polar solvents with one derivative bearing a dimethylaminophenyl substituent.

Ultrafast Excited-State Dynamics of Eosin B: A Potential Probe of the Hydrogen-Bonding Properties of the Environment

“…13,[32][33][34][35][36][37][38][39] This process is enabled by the nitro groups of EB that are good hydrogen-bond acceptors. [24][25][26]40,41 In order to further confirm this hypothesis, TA measurements were carried out in perdeuterated water.…”

Ultrafast excited-state dynamics of strongly coupled porphyrin/core-substituted-naphthalenediimide dyads

“…33. Excitation was carried out with o90 ps pulses generated with a laser diode at 395 nm (PicoQuant model LDH-PC-400B) and fluorescence was detected at magic angle.…”

A two-state model of twisted intramolecular charge-transfer in monomethine dyes

“…[20][21][22][23][24][25][26][27][28][29][30] Twisting of the methine bonds in the excited state is predicted to lower the potential energy of the excited state, and to lead to charge-localized (for neutral dyes, charge-separated) states from which internal conversion is possible due to a reduced adiabatic energy gap. 31,32 In a) seth.olsen@uq.edu.au.…”