Highly efficient energy transfer in BODIPY–pyrene decorated cyclotriphosphazene

• New BODIPY–pyrene substituted cyclic phosphazenes have been synthesized.
• The photophysical properties of the compounds have been studied in dichloromethane.
• Ground state electronic absorption and fluorescence spectra revealed enhanced Stokes shifts.
• Enhanced FRET was noted for some molecules.

In this study, two different cyclophosphazene compounds bearing five pyrene units and one borondipyrromethene unit were designed and synthesized. All compounds were fully characterized by elemental analysis, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, 1H, 13C and 31P NMR spectroscopy. The photophysical properties of the new compounds were investigated by means of absorption and fluorescence spectroscopies in dilute dichloromethane solutions. Both systems exhibit a highly efficient energy transfer process, from the excited pyrene units to the borondipyrromethene units. The photophysical studies indicated that the compounds exhibit large Stokes' shifts unlike reference simple BODIPY dyes.

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