2-Aza-1,3-butadiene ligands for the selective detection of Hg2+ and Cu2+ ions

NFe6NFeNFeNFe789N10OOOOON11OOOOO Results and Discussion Synthesis The synthetic route used for the preparation of these ligands is depicted in Scheme 1. Specifically, the preparation of the ferrocene derivatives 6,7 and 10 bearing a fluorophore unit linked to the 1 position of the 2-azadiene bridge were prepared starting from the appropriate N- substituted diethylaminophosphonate 2 or 38b which were obtained in almost quantitative yield, by condensation of diethylaminophosphonate 19 with the adequate aldehyde R1-CHO. Treatment of those N-substituted diethylaminophosphonates n-BuLi at -78ºC and subsequent reaction of the resulting metalloylide with a new carbonyl derivative R2-CHO provided 6, 7 and 10 in good yields (Scheme 1). (EtO)2P-CH2NH2O1(E,E) 2: R1 = 2-Naphthyl3: R1 = 1-Pyrenyl4: R1 = Fc5: R1 = 4'-benzo-crown-56: R1 = 2-Naphthyl; R2 = Fc7: R1 = 1-Pyrenyl; R2 = Fc 8: R1 = Fc; R2 = 2-Naphthyl9: R1 = Fc; R2 = 1-Pyrenyl10: R1 = 1-Pyrenyl; R2 = 4'-benzo-crown-511: R1 = 4'-benzo-crown-5; R2 = 1-Pyrenyl95% (a)(b) 55%-80% NP(OEt)2OR1NR2R1 Reagents and conditions: (a) i) appropriate aldehyde (R1-CHO)/CH2Cl2/rt, ii) anhydrous Na2SO4; (b) i) n-BuLi/-78ºC, ii) appropriate aldehyde (R2-CHO). Scheme 1. Preparation of 2-aza-1,3-butadiene derivatives. 0