Excited state intramolecular proton transfer and photophysics of a new fluorenyl two-photon fluorescent probe

Alma R. Morales, Katherine J. Schafer-Hales, Cicerón O. Yanez, Mykhailo V. Bondar, Olga V. Przhonska, Adam I. Marcus, Kevin D. Belfield

Research output: Contribution to journalArticlepeer-review

41 Scopus citations


The steady-state photophysical, NMR, and two-photon absorption (2PA) properties of a new fluorene derivative (1) containing the 2-{2'-hydroxyphenyl) benzothiazole (HBT) terminal construct is investigated for use as a fluorescence probe in bioimaging. A comprehensive analysis of the linear spectral properties reveals inter- and intramolecular hydrogen bonding and excited state intramolecular proton transfer (ESIPT) processes in the HBT substituent. A specific electronic model with a double minimum potential energy surface is consistent with the observed spectral properties. The 2PA spectra are obtained using a standard two-photon induced fluorescence method with a femtosecond kHz laser system, affording a maximum 2PA cross section of -600 GM, a sufficiently high value for two-photon fluorescence imaging. No dependence of twophoton absorption efficiency on solvent properties and hydrogen bonding in the HBT substituent is observed. The potential use of this fluorenyl probe in bioimaging is demonstrated via one- and two-photon fluorescence imaging of COS-7 cells.

Original languageEnglish (US)
Pages (from-to)2073-2081
Number of pages9
Issue number12
StatePublished - Aug 24 2009
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Atomic and Molecular Physics, and Optics
  • Physical and Theoretical Chemistry


  • Bioimaging agents
  • Fluorescent probes
  • Hydrogen bonding
  • Photophysics
  • Two-photon induced fluorescence


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