Dual fluorescence through Kasha's rule breaking: an unconventional photomechanism for intracellular probe design

J Phys Chem B. 2015 May 21;119(20):6144-54. doi: 10.1021/acs.jpcb.5b01119. Epub 2015 May 12.

Abstract

Dual fluorescence is an anomalous photophysical phenomenon observed in very few chromophores in which a two-color radiative process occurs that involves two distinct excited electronic states. To date its observation was linked either to electronic rearrangement of an excited fluorophore leading to two conformers with distinct emissive properties, or to a photochemical modification leading to different fluorescent species. In both cases, emission originates from the lowest excited state of the resulting molecular configurations, in line with the so-called Kasha's rule. We report here a combined theoretical and spectroscopic study showing, for the first time, an anti-Kasha dual-emission mechanism, in which simultaneous two-color emission takes place from the first and second excited state of a coumarin derivative. We argue that the observed environmental sensitivity of this peculiar optical response makes the present compound ideally suited for biosensing applications in living cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biosensing Techniques
  • Cell Line
  • Coumarins / analysis*
  • Electrons
  • Fluorescence Polarization
  • Fluorescent Dyes / analysis*
  • Humans
  • Microscopy, Confocal
  • Models, Molecular
  • Molecular Conformation

Substances

  • Coumarins
  • Fluorescent Dyes