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Vectorial Photoinduced Energy Transfer Between Boron–Dipyrromethene (Bodipy) Chromophores Across a Fluorene Bridge
Author(s) -
Puntoriero Fausto,
Nastasi Francesco,
Campagna Sebastiano,
Bura Thomas,
Ziessel Raymond
Publication year - 2010
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201000466
Subject(s) - bodipy , chromophore , fluorene , photochemistry , luminescence , absorption spectroscopy , absorption (acoustics) , chemistry , ultrafast laser spectroscopy , spectroscopy , materials science , fluorescence , organic chemistry , optoelectronics , polymer , optics , composite material , physics , quantum mechanics
A series of novel multichromophoric, luminescent compounds has been prepared, and their absorption spectra, luminescence properties (both at 77 K in rigid matrix and at 298 K in fluid solution), and photoinduced intercomponent energy‐transfer processes have been studied. The series contains two new multichromophoric systems 1 and 2 , each one containing two different boron–dipyrromethene (Bodipy) subunits and one bridging fluorene species, and two fluorene–Bodipy bichromophoric species, 6 and 7 . Three monochromophoric compounds, 3 , 4 , and 5 , used as precursors in the synthetic process, were also fully characterized. The absorption spectra of the multichromophoric compounds are roughly the summation of the absorption spectra of their individual components, thus demonstrating the supramolecular nature of the assemblies. Luminescence studies show that quantitative energy transfer occurs in 6 and 7 from the fluorene chromophore to the Bodipy dyes. Luminescence studies, complemented by transient‐absorption spectroscopy studies, also indicate that efficient inter‐Bodipy energy transfer across the rigid fluorene spacer takes place in 1 and 2 , with rate constants, evaluated by several experimental methods, between 2.0 and 7.0×10 9 s −1 . Such an inter‐Bodipy energy transfer appears to be governed by the Förster mechanism. By taking advantage of the presence of various protonable sites in the substituents of the lower‐energy Bodipy subunit of 1 and 2 , the effect of protonation on the energy‐transfer rates has also been investigated. The results suggest that control of energy‐transfer rate and efficiency of inter‐Bodipy energy transfer in this type of systems can be achieved by an external, reversible input.