Evaluation of N-Alkyl-bis-o-aminobenzamide Receptors for the Determination and Separation of Metal Ions by Fluorescence, UV-Visible Spectrometry and Zeta Potential

This paper presents the synthesis and evaluation of physicochemical behavior of a new series of N-alkyl-bis-o-aminobenzamides (BOABs) in aqueous solution. The study was targeted to the complexing capacity of five metal ions (Fe²⁺, Cu²⁺, Cd²⁺, Hg²⁺ and Pb²⁺) of environmental concern as the medullar principle of a liquid phase sensor for its application in the determination of these metal ions due to its versatility of use. Molecular fluorescence, UV-visible and Zeta potential were measured for five BOABs and the effect of alkyl groups with different central chain length (n = 3, 4, 6, 8 and 10) on physicochemical performance determined. The results have shown that these derivatives present higher sensibility and selectivity for Cu²⁺ even in the presence of the other metal ions. An additional application test was done adding a pectin (0.1 wt %) solution to the BOAB-Cu⁺² complex to obtain a precipitate (flocs) as a potential selective separation process of Cu from aqueous solution. The solid was then lyophilized and analyzed by SEM-EDS, the images showed spheric forms containing Cu⁺² with diameter of approximately of 8 μm and 30 wt %.

A BODIPY-carbazole hybrid as a fluorescent probe: the design, synthesis, and discrimination of surfactants and the determination of the CMC values

A novel fluorescent probe (BDP-Zn²⁺) was developed to efficiently discriminate four kinds of surfactants and determine the CMC values.

A new fluorescent and electrochemical Zn2+ ion sensor based on Schiff base derived from benzil and L-tryptophan

Single molecule acting as both fluorescent and electrochemical sensor for Zn(2+) ion is rare. The product (L) obtained on condensation between benzil and L-tryptophan has been characterized by H NMR, ESI-MS and FT-IR spectroscopy. L in 1:1 (v/v) CH3OH:H2O solution shows fluorescence emission in the range 300 nm to 600 nm with λmax at 350 nm when is excited with 295 nm photon. Zn(2+) ion could induce a 10-fold enhancement in fluorescent intensity of L. Fluorescence and UV/Visible spectral data analysis shows that the binding ratio between Zn(2+) ion and L is 1:1 with log β=4.55. Binding of Zn(2+) ion disrupts the photoinduced electron transfer (PET) process in L and causes the fluorescence intensity enhancement. When cyclic voltammogram is recorded for L in 1:1 (v/v) CH3OH:H2O using glassy carbon (GC) electrode, two quasi reversible redox couples at redox potential values -0.630±0.005 V and -1.007±0.005 V are obtained (Ag-AgCl as reference, scan rate 0.1 V s(-1)). Interaction with Zn(2+) ion makes the first redox couple irreversible while the second couple undergoes a 0.089 V positive shift in redox potential. Metal ions - Cd(2+), Cu(2+), Co(2+), Hg(2+), Ag(+), Ni(2+), Fe(2+), Mn(2+), Mg(2+), Ca(2+)and Pb(2+), individually or all together, has no effect on the fluorescent as well as electrochemical property of L. DFT calculations showed that Zn(2+) ion binds to L to form a stable complex. The detection limit for both fluorescence as well as electrochemical detection was 10(-6) M.

An “off–on–off” fluorescent probe for the sequential detection of Zn2+ and hydrogen sulfide in aqueous solution

The fluorescent chemosensor L1 has been synthesized for the sequential detection of Zn²⁺ and hydrogen sulfide.

Zinc-specific fluorescent response of tris(isoquinolylmethyl)amines (isoTQAs)

Isoquinoline-based tetradentate ligands with C(3)-symmetry, tris(1- or 3-isoquinolylmethyl)amine (1- or 3-isoTQA), have been prepared and their zinc-induced fluorescence enhancement was investigated. Upon excitation at 324 nm, 1-isoTQA shows very weak fluorescence (ϕ = ∼0.003) in DMF/H(2)O (1/1) solution. In the presence of zinc ion, 1-isoTQA exhibits fluorescence increase (ϕ = 0.041) at 359 and 470 nm. This fluorescence enhancement at 470 nm is specific for zinc. However, 3-isoTQA exhibited a smaller fluorescence enhancement upon zinc complexation (ϕ = 0.017, λ(em) = 360 and 464 nm) compared with 1-isoTQA. Crystal structures of zinc complexes of isoTQAs demonstrate the diminished steric crowding and shorter Zn-N(aromatic) distances compared with isoTQENs (N,N,N',N'-tetrakis(isoquinolylmethyl)ethylenediamines) leads to a higher fluorescent response toward zinc relative to cadmium.