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A Schiff-base compound, 2-((E)-1-(2-(dimethylamino)ethylimino)ethyl)phenol (HL), has been synthesized and characterized by different spectroscopic methods The chemosensor shows selective “turn–on” cyan colour fluorescence response to Al 3+ ion over a wide variety of other competing metal ions such as Zn 2+ , Cu 2+ , Co 2+ , Ni 2+ , Cd 2+ , Fe 2+ , Mg 2+ , Hg 2+ , Mn 2+ , Ca 2+ , Pb 2+ , Fe 3+ , Cr 3+ , Na + and K + . The fluorescence emission intensity at 462 nm displayed by the chemosensor, increases progressively during the addition of Al 3+ ion until saturation point, with over 20 fold intensity enhancement. Additionally, the linear range for the chemosensor has been found to be 0.5 × 10 −6 to 10 × 10 −6  mol/L, the detection limit of the chemosensor is 4.32 × 10 −6  M and the stability constant is 2.1 × 10 4  M −1 . Similar fluorescence behaviour is also observed in a variety of solvents and solvent mixtures in the presence of Al 3+ . The fluorescent emission has also been detected when a sample solution of HL containing Al 3+ is irradiated by UV light. UV–vis titration experiment has established that the chemosensor HL, binds to Al 3+ in 2:1 ratio. The Density Functional Theory (DFT) and Time Dependent-Density Functional Theory (TD–DFT) calculations were performed on HL, L − and its aluminium complex which give insight into the geometric, electronic, thermodynamic and optical properties of chemosensor-Al 3+ interactions. [ABSTRACT FROM AUTHOR]

A novel chemo-sensor based on diaminobenzidine (H 2 L) was synthesized and characterized. The chemo-sensor shows selective “turn-on” fluorescence response to Zn 2+ ion over a variety of other competing metal ions such as Al 3+ , Mn 2+ , Fe 3+ , Co 2+ , Ni 2+ , Cu 2+ , and Cd 2+ . The strong fluorescent emission can be observed even at ppm level concentration of the probe in the presence of Zn 2+ with over 54 fold intensity enhancement at 509 nm. Similar fluorescence behaviour is also observed in a variety of solvents and solvent mixtures in the presence of zinc(II). The fluorescent emission is also detected when the H 2 L sample solution containing Zn 2+ is exposed to UV radiation. The sensitive nature of fluorescent response of the probe to Zn 2+ is gauged from the very low detection limit of 8.6 × 10 −9 M. The chemo-sensor H 2 L binds to zinc(II) in 1:1 stoichiometry as determined by Job's plot and the binding constant is calculated as 7.8 × 10 4 M −1 . [ABSTRACT FROM AUTHOR]

• The chemosensor (H 3 L) showed high selectivity for Al3+ ion. • The binding ratio of H 3 L:Al3+ was obtained as 2:1 determined by the Job's plot and 1H NMR titration in solution phase. • DFT/TD-DFT calculations showed the stability of Al3+–complex. • The DFT/TD-DFT values for emission and electronic studies show good agreement with experimental values. A Schiff base chemosensor (H 3 L) based on the 4-(N,N-Diethylamino)salicylaldehyde moiety has been synthesized and characterized using several spectroscopic techniques i.e. 1H-NMR, FT-IR, Mass and UV-visible. The chemosensor shows high selectivity for Al3+ ion through 'turn-on' cyan colour fluorescence over a variety of metal ions i.e. Ni2+, Zn2+, Cd2+, Mn2+ ions except Co2+, Cu2+ and Fe3+ ions. The chemosensor exhibits 20 fold intensity enhancement at 481 nm (λ ex = 378 nm) against Al3+ ion until saturation point. Additionally, the detection limit and stability constant were found to be 1.2 × 10−6 M and 5.2 × 105 M−1, respectively with the low equivalent range of 1–34 µM. The chemosensor also displays similar fluorescence behaviour for Al3+ ion in a variety of solvents and solvent mixtures. The quantum yield (Ф F) values for H 3 L and Al3+–complex were observed to be 0.08 and 0.29, respectively. The Job's plot calculations show that, H 3 L binds to Al3+ ion in 2:1 ratio. 1H-NMR titration analysis indicates that the chemosensor undergoes mono-deprotonation while binding to Al3+ ion. The geometry of the chemosensor and Al3+–complex were optimised and some thermodynamic parameters were calculated using Density Functional Theory (DFT). The Gibbs free energy of complex was calculated to be -1272.00 kcal/mol. Further, the optical and electronic properties of the proposed complex were explained with the help of Time Dependent-Density Functional Theory (TD–DFT). [Display omitted] [ABSTRACT FROM AUTHOR]

A dinuclear doubly bridged copper(II) complex [Cu 2 L 2 ] where L represents N, N′-bis(3-ethoxysalicylidene)-4-methyl-1,3-phenylenediamine has been synthesised. The ligand was characterised by elemental analysis and spectroscopic techniques such as 1H NMR, 13C NMR, FT–IR, UV–visible and ESI–mass. The copper(II) complex was characterised using partial elemental analysis, FT-IR and UV–visible spectral techniques. The solid state structure of the complex was carried out using single crystal X-ray diffraction. The crystallographic study reveals that the two copper(II) metal ions are four coordinated (O 2 N 2) via phenolate O and azomethine N atoms, forming an unusual geometry between tetrahedral and square-planar. Cyclic voltammetry of complex reveals two consecutive quasi-reversible one electron redox couples corresponding to CuII–CuII/CuII–CuI and CuII–CuI/CuI–CuI. Density Functional Theory (DFT) and Time-dependent density functional theory (TD–DFT) calculations were carried out for the determination of the optimized structures. The theoretically obtained fundamental vibrational frequencies show good agreement with observed values. The ligand binds to Cu(II) in 1:1 stoichiometry as determined by Job's plot and the binding constant is calculated as 6.8 × 102 M−1 in solution phase. The photoluminescence property of the complex has also been investigated to understand its emission behaviour. Image 1 • A tetradentate m -phenylenediamine based ligand yields a dinuclear copper complex. • The strain involved during coordination introduces a distorted tetrahedral geometry. • UV-visible spectral titrations indicate a 1:1 binding ratio for Cu2+ and H 2 L. • · DFT/TD-DFT calculations demonstrate the stability of the binuclear copper complex. [ABSTRACT FROM AUTHOR]