A series of fluorescent dicationic compounds including N-benzylated or alkylated at quinolyl fragments inserted in N,N�-bis(quinolyl)pyridine-2,6-dicarboxamide have been synthesized, characterized by crystal structures and studied as fluorescent probes for anions (nucleotides and inorganic species) in buffered water (pH = 6.5). In general, all the compounds display efficient fluorescent quenching by additions of inorganic anions such as halide and oxoanions (Stern-Volmer quenching constants between 10 and 150 M-1) with a very high affinity for chloride in the case the N-benzylated receptor (Kass = 5000 M-1), from crystal structures of triflate and chloride salts of this receptor is possible to observed that chloride is accommodated in the cavity of receptor, symmetrically between amide groups with hydrogen bond interaction N-H . . . Cl which can be result in the high affinity . Quenching emission by nucleoside triphosphate is much more efficient than by inorganic anions (Ksv = 90 -570 M-1) and the affinity is also higher (Kass = 1600 � 6000 M-1) with a peak of selectivity for ATP following the order ATP > GTP > ADP > CTP > AMP. The profiles of Stern-Volmer for the receptors show the combination of static and dynamic quenching process by addition of anions. Association constants, KA, with anions were calculated from analysis of concentration profiles of the quenching effects on the fluorescence. These fluorescent probes allow for sensing in micromolar range of anions in water.   

Anion sensing based on cationic receptors by fluorescence spectroscopy in water

248th National Meeting (2014)

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