Aza-oxa macrocyclic ligands functionalised with naphthylmethyl fluorescent groups

Compounds L-1 and L-2 were obtained by reaction of 2-(bromomethyl)naphthalene with 1,4,10-trioxa-7,13-diazacyclopentadecane and 1,4,7-trioxa-10-azacyclododecane, respectively. These receptors contain aza-oxa crowns attached covalently to fluorescent groups. The protonation and coordination behaviour of L-1 and L-2 against metal ions has been studied in dioxane:water (70:30 v/v, 25 degrees C, 0.1 M potassium nitrate) using potentiometric methods. All metal ions studied form complexes with L-1 and L-2 with the logarithm of the formation constants L + M2+ = [M(L)](2+) in the sequence Cd2+ congruent to Pb2+, Zn2+ < Hg2+ for L-1 and Zn2+ < Ni2+ < Pb2+ < Cd2+ < Cu2+ for L-2. The fluorescent behaviour of L-1 and L-2 was studied in dioxane:water (70:30, v/v) and in acetonitrile in the presence of Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, Pb2+ cations and chloride, bromide, sulfate and phosphate anions, The most significant feature is the quenching of the fluorescence produced by Cu2+ in acetonitrile. (C) 2000 Elsevier Science Ltd. All rights reserved.