A novel hydrogen-bonded cyclic dibromide in an organic diammonium salt

The organic diammonium salt N,N′-dibenzyl-N,N,N′,N′-tetramethylethylenediammonium dibromide dihydrate, (dbtmen)Br₂.2H₂O (1), was prepared by the reaction of N,N,N′,N′-tetramethyl-ethylenediamine (tmen) with benzyl bromide.1 crystallizes in the triclinic space group with the following unit cell dimensions for C₂₀H₃₄Br₂N₂O₂ (M = 494.31):a = 8.6672(6) ?,b = 11.7046(8) ?,c = 11.7731(8) ?, α = 76.988(8)°, β = 88.978(8)°, γ= 76.198(8)γ,V= 1129.26(13) ?³, Z=2. Three components, namely the (dbtmen)²⁺ dication, two bromide anions and two crystal water molecules constitute the structural arrangement of1. H₂O molecules are linked to bromide anions via O-H...Br hydrogen bonding interactions resulting in the formation of a four-membered O₂Br₂ cyclic dibromide. The O₂Br₂ units and the dications are arranged as alternating layers extending in the crystallographicbc plane. The arrangement of anions and cations may be viewed as a typical lamellar structure. The crystal water molecules can be removed by heating 1 at 140°C and the anhydrous dibromide thus formed can be fully rehydrated as evidenced by IR spectra and X-ray powder patterns. Dedicated to Prof S Chandrasekaran on the occasion of his 60th birthday     

Fluorimetric determination of traces of europium(III) using a new chelator and acetate or phosphate in dimethylsulfoxide as enhancers

A new Schiff-base ligand [N, N′, N″-Tri- (2,4-dihydroxyacetophenone) – triaminotriethylamine (TDATA)] with a tripodal structure was synthesized. Its fluorescence intensity with the europium(III) complex was increased about 178-fold in the presence of sodium acetate (NaAc) and about 126-fold in the presence of sodium phosphate (Na₃PO₄) solution. After adding the organic solvent dimethylsulfoxide (DMSO) to the above system, which leads to Eu³⁺ the fluorescence was further enhanced about 12-fold. Spectrofluorimetric determination of trace amounts of Eu³⁺ based on the phenomenon was performed. The excitation and emission wavelength is 365 nm and 615 nm, respectively. Under optimum conditions, the fluorescence intensities vary linearly with the concentration of Eu³⁺ in the range of 4.9 × 10⁻¹²–3.2 × 10⁻⁶ mol · L⁻¹ with a detection limit of 4.5 × 10⁻¹² mol · L⁻¹ (for the TDATA-NaAc-DMSO system) or 6.2 × 10⁻¹¹–8.6 × 10⁻⁶ mol · L⁻¹ with a detection limit of 6.0 × 10⁻¹¹ mol · L⁻¹ (for the TDATA-Na₃PO₄-DMSO system). Interferences of some rare earth metals and other inorganic ions are described. The method is a selective, sensitive, rapid and simple analytical procedure for the determination of europium(III) in a high purity yttrium oxide and synthetic sample. The mechanism for the fluorescence enhancement is also discussed.