Intramolecular charge transfer in pyrromethene laser dyes: photophysical behaviour of PM650

Chemphyschem. 2004 Nov 12;5(11):1762-71. doi: 10.1002/cphc.200400242.

Abstract

Absorption and fluorescence (steady-state and time-correlated) techniques are used to study the photophysical characteristics of the pyrromethene 650 (PM650) dye. The presence of the cyano group at the 8 position considerably shifts the absorption and fluorescence bands to lower energies with respect to other related pyrromethene dyes; this is attributed to the strong electron-acceptor character of the cyano group, as is theoretically confirmed by quantum mechanical methods. The fluorescence properties of PM650 are intensively solvent-dependent. The fluorescence band is shifted to lower energies in polar/protic solutions, and the evolution of the corresponding wavelength with the solvent is analysed by a multicomponent linear regression. The fluorescence quantum yield and the lifetime strongly decrease in polar/protic solvents, which can be ascribed to an extra nonradiative deactivation, via an intramolecular charge-transfer state (ICT state), favoured in polar media.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Fluorescent Dyes / chemistry*
  • Fluorescent Dyes / radiation effects
  • Lasers*
  • Molecular Conformation
  • Photochemistry
  • Porphobilinogen / analogs & derivatives*
  • Porphobilinogen / chemistry*
  • Porphobilinogen / radiation effects
  • Solvents / chemistry
  • Thermodynamics*
  • Time Factors

Substances

  • Fluorescent Dyes
  • Solvents
  • pyrromethene 546
  • pyrromethene 597
  • pyrromethene 650
  • Porphobilinogen