Anthracene appended pyridinium amide–urea conjugate in selective fluorometric sensing of L-N-acetylvaline salt

A new anthracene labeled pyridinium amide–urea conjugate 1 has been designed and synthesized. The receptor shows a different fluorometric response with L-N-acetylvaline and L-N-acetylalanine salts in CH3CN in contrast to the other salts of L-N-acetyl α-amino acids and (S)-α-hydroxy acids studied. Upon complexation of the tetrabutylammonium salt of L-N-acetylvaline, the emission of 1 increases accompanied by the formation of a new band at higher wavelength and this characteristic change distinguishes it from other anionic substrates studied. The binding interaction has been studied by 1H NMR, fluorescence and UV titration experiments

A trinuclear crystallochromic Cd(II) complex with zwitterionic coordination terminals:Network of metalorganic motifs through C-H⋯N and charge promoted N^∂+-H⋯N associations in solid State

In aqueous medium at pH 6, cadmium acetate dihydrate combines with 4,6-dimethylpyrimidine-2-thiol to form a centrosymmetric Cl, S-bridged complex having zwitterionic terminals. The zwitterionic nature of this complex is evidenced by its pH and conductance values in methanol solution. It crystallizes in the space group P21/c (Z = 4 asymmetric units, two molecules), each molecule being uncommonly characterized by a centric Cd(II)S 2Cl2N2 as well as two acentric and anionic Cd(II)S3ClN2 coordination chromophores with counter cationic ligands. Relevant literature reports indicate a template relation between the structural designs of this complex and hydrated cadmium acetate, the metalorganic precursor. Packing of molecular motifs through weak C-H···N and strong charge-enhanced Nδ+- H···N interactions generate the crystal structure with numerous screw-glide related small voids. Attempt has been made to rationalize the crystallochromic nature of the complex (pale green in solution, pale orange while crystalline) by time dependent DFT and ZINDO/S studies. Graphical Abstract: In aqueous medium, cadmium acetate combines with 4,6- dimethylpyrimidine-2-thiol to form a centrosymmetric, trinuclear complex with zwitterionic terminals. The crystallochromic behaviour of this complex is investigated by quantum chemical treatment.[Figure not available: see fulltext.]</p

Quinoline based receptor in fluorometric discrimination of carboxylic acids

Quinoline and naphthalene-based fluororeceptors 1 and 2 have been designed and synthesized for detection of hydroxy carboxylic acids in less polar solvents. The receptor 1 shows monomer emission quenching followed by excimer emission upon hydrogen bond-mediated complexation of carboxylic acids. The excimer emission distinguishes aromatic dicarboxylic acids from aliphatic dicarboxylic acids and even long chain aliphatic dicarboxylic acids from short chain aliphatic dicarboxylic acids. The receptor 1 is found to be selective for citric acid with a strong excimer emission in CHCl3. On the contrary, the receptor 2 exhibited less binding constant value and did not form any excimer upon complexation with the same acids under similar conditions. This established the role of quinoline ring nitrogen in binding with the acids

Naphthalene and pyrrole substituted guanidine in selective sensing of Cu²⁺, Hg²⁺, Pb²⁺ and CN⁻ ions under different conditions

<p>Naphthalene and pyrrole substituted guanidine <b>1</b> has been designed and synthesised. Compound <b>1</b> efficiently distinguishes Cu²⁺, Hg²⁺ and Pb²⁺ ions by exhibiting different responses in fluorescence. While compound <b>1</b> exhibited <i>turn</i>-<i>on</i> emission selectively in the presence of Hg²⁺ and Pb²⁺ ions in CH₃CN and CH₃CN–H₂O (1:1, v/v), respectively, it showed decrease in emission upon interaction with Cu²⁺ ion in CH₃CN. Furthermore, the Cu-<b>1</b> ensemble has been established as a potential probe for selective detection of CN⁻ ion over a series of other anions involving colour change (in ordinary light: colourless to light yellow and under UV light: colourless to sky blue). Theoretical insight has been invoked to understand the mode of metal–ligand interaction.</p> <p>Naphthalene and pyrrole substituted guanidine <b>1</b> has been designed and synthesised. It efficiently distinguishes Cu²⁺, Hg²⁺ and Pb²⁺ ions by exhibiting different responses in fluorescence. The Cu-<b>1</b> ensemble has been established as a potential probe for selective detection of CN^- ion over a series of other anions involving colour change.</p

pH-regulated hydrothermal synthesis and characterization of Sb4O5X2 (X = Br/Cl) and its use for the dye degradation of methyl orange both with and without light illumination

A pH-regulated hydrothermal synthesis method was employed to synthesize Sb4O5Br2 and Sb4O5Cl2 crystallites. Characterization is done by single crystal X-ray diffraction, powder X-ray diffraction, infra-red spectroscopy, scanning electron microscopy and DFT studies. The compounds crystallize in monoclinic symmetry with a P2(1)/c space group. Complete structural analysis of the Sb4O5Br2 compound by using single crystal X-ray diffraction data is performed for the first time and a comparative study with Sb4O5Cl2 is also discussed. The SEM study reveals that the surface morphology changes with the variation of pH for bromide compounds, whereas pH change does not affect the morphology of the chloride analogues. Electronic band structures of the synthesized oxyhalides were investigated in order to understand their catalytic effects in the dye degradation reactions in dark as well as sunlight conditions