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5326947 
Journal Article 
Fluorene Analogues of Prodan with Superior Fluorescence Brightness and Solvatochromism 
Kucherak, OA; Didier, P; Mely, Y; Klymchenko, AS 
2010 
Journal of Physical Chemistry Letters
ISSN: 1948-7185 
616-620 
English 
In a search for environmentally sensitive (solvatochromic) dyes with superior properties, we extended the electronic conjugation of one of the best solvatochromic dyes, Prodan, by substituting its naphthalene core with fluorene. The newly synthesized fluorene derivatives bearing strong electron-donor (dialkylamino) and -acceptor (carbonyl) groups at the 2 and 7 positions showed red-shifted absorption (close to 400 nm), twice as large of a absorption coefficient (43 000 M-1 cm-1), and a manifold larger two-photon absorption cross section (∼400 GM) compared to Prodan. Studies in solvents revealed much stronger fluorescence solvatochromism of the new dyes, which is connected with their twice as large transition dipole moment (14.0 D). Similarly to Prodan, they exhibit high fluorescence quantum yields, while their photostability is largely improved. Thus, substitution of the naphthalene core in Prodan with fluorene resulted in new fluorophores with superior spectroscopic and solvatochromic properties. We expect them to find a variety of applications as environmentally sensitive probes and labels in biology. © 2010 American Chemical Society.