Triplet-state spectroscopy of dipyrromethene·BF2 laser dyes

The substituents at positions 2, 6 and 8 in the commercial dye PM567 have been changed and their influence on the triplet state of each dye has been studied in terms of the absorption spectra, lifetimes, quantum yields and triplet–triplet extinction coefficients. The dyes have in position 8 the groups p-acetoxypolymethylene, p-(acetoxypropyl)phenyl or p-(acetoxymethyl)polyphenylene, or in positions 2 and 6 the groups tert-butyl (commercial dye PM597) or 3′-acetoxypropyl. The triplet-state spectroscopy results nearly independent on the molecular structure for the mono- and di-substituted aliphatic derivatives. However, the 8-aryl substitution increases both the triplet absorption over the fluorescence spectral region and the triplet-state quantum yield, but reduces the triplet absorption coefficient.