Characterization of a highly Al3+ -selective fluorescence probe based on naphthalimide-Schiff base and its application to practical water samples.

A new fluorescent Al3+ -probe, N-allyl-4-[3,3'-((2-aminoethyl)azanediyl)-bis(N´-(2-hydroxybenzylidene)propanehy-drazide)]-1,8-naphthalimide (L), was designed and synthesized based on 1,8-naphthalimide. The probe L contains 1,8-naphthalimide moiety as the fluorophore and a Schiff base as the recognition group. The structure of L was determined by single crystal X-ray. L emission at 526 nm increased on addition of Al3+ under excitation wavelength at 350 nm. L exhibited high selectivity and sensitivity fluorescence emission towards to Al3+ in ethanol/Tris-HCl buffer solution (1:1, v/v, pH = 7.2) as compared with other tested metal ions. A good linearity with a correlation coefficient (R2 ) of 0.99 was observed in the concentration range 2-10 µM. The binding constant and the detection limit of L for Al3+ were calculated to 2.6 × 104  M-1 and 0.34 µM, respectively. The results of experiments that including Job plot, ultraviolet-visible (UV-Vis) light titration, fluorescence titration, ESI-MS and 1 H NMR titration, indicated a 1:1 stoichiometric complex between L and Al3+ . L was highly effective in monitoring Al3+ in real-life Yellow River and tap water samples.

A Highly Selective and Sensitive Fluorescent Turn-on Probe for Al3+ Based on Naphthalimide Schiff Base.

A simple and highly selective aluminium ion fluorescent probe (N-n-butyl-4-[3,3'-((2-aminoethyl)azanediyl)bis(N'-(2-hydroxy-3-methoxybenzylidene)-propanehydrazide)]-1,8-naphthalimide) (P-1) employing 1,8-naphthalimide as the fluorophore group and Schiff base as the recognition group has been successfully synthesized and systemically characterized. The structure of probe P-1 has been established by single crystal X-ray. The photophysical properties of probe P-1 revealed that the values of the fluorescence quantum yield are higher in non-polar solvents than in polar solvents. Compared with the free P-1, the fluorescence intensity of P-1 shows a significant fluorescence enhancement in the presence of Al3+ without any significant interference from other cations and anions. In addition, from the UV-vis titration, fluorescence titration,Job's plot and 1H NMR spectra analysis, we could primarily confirm that three important coordinative sites of P-1 for Al3+ were from imine nitrogen and tertiary amine nitrogen and formed a 1:1 complex. The fluorescence intensity for the (P-1) showed a good linearity with the concentration of Al3+ in the range of 3.0-10.0 µM, with a detection limit of 8.65 × 10-8 M and a binding constant (Kb) of 4.95 × 104 M-1. It is worthy of note that the probe P-1 was successfully applied in detection of Al3+ in Yellow River and tap water samples.

Cu(I) complexes regulated by N-heterocyclic ligands: Syntheses, structures, fluorescence and electrochemical properties.

Three mononuclear Cu(I) complexes, namely, [Cu(2-PBO)(PPh3)2]·ClO4·2CH2Cl2 (1), [Cu(3-PBO)(PPh3)2(ClO4)]·CH2Cl2 (2) and [Cu(PBM)(PPh3)2]·ClO4 (3) (2-PBO = 2-(2'-Pyridyl)benzoxazole, 3-PBO = 2-(3'-Pyridyl)benzoxazole, PBM = 2-(2'-Pyridyl)benzimidazole, PPh3 = triphenylphosphine) have been synthesized and characterized by elemental analyses, IR, 1H NMR, 13C NMR, X-ray single crystal diffraction and thermal analysis. Photoluminescent investigation shows that complexes 1-3 exhibit distinct tunable light green (512 nm)-to-yellow (557 nm) photoluminescence by varying the N-heterocyclic ligands. Three complexes show intense 2-PBO-based yellow, 3-PBO-based light green and intense PBM-based bright green luminescence upon irradiation with a standard UV lamp (λex = 254 nm) at room temperature. Moreover, the electrochemical properties of 1-3 have been investigated by cyclic voltammetry. The results suggest the frontier molecular orbits and the HOMO-LUMO energy gaps of these cuprous complexes are effectively adjusted through the introduction of different N-heterocyclic ligands, thus achieving the selective luminescence of the cuprous complexes.