COMMUNICATIONS2 was adjusted to pH 7.1 with 2,6-lutidine and Ni" is added, no substantial decrease in IF was observed, even after the addition of one or more equivalents of metal ion (Fig. 3). When Cu" was added to the same solution, IF decreased linearly and reached zero on addition of one equivalent of the metal ion (Fig. 3 ) .Until now anthracene-based fluorescent sensors for metal ions have been known primarily for alkali and alkaline-earth metal ions. Typically the uncomplexed sensor does not fluorescence and the binding of the metal to the receptor results in fluoresce; this switching mechanism is triggered by photoinduced electron transfer."] Compound 2 is the prototype of a new family of pH-sensitive anthracene-based fluorescent sensors for transition metal ions. Here the uncomplexed sensor fluoresces, and the interaction with the 3d metal ion leads to fluorescence quenching; this switching mechanism is triggered by energy transfer. Sensor selectivity towards transition metal ions can be modified by changing the structural features of the chelating unit: this unit can be cyclic or noncyclic, the number and arrangement of amide groups can be changed, and other heteroatoms can be included. We are currently designing and testing these types of sensors.Experinwntul Procedure
A BF(2) complex containing an octafluorotetracene moiety was synthesized as a new type of electron acceptor. This compound exhibits a long-wavelength absorption based on the perfluorotetracene skeleton and high electron affinity due to its quadrupolar structure enhanced by fluorination. In the crystal, the molecules are arranged with short F...pi and F...F contacts affording a dense crystal packing. The BF(2) complex exhibited n-type semiconducting behavior.
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