Ratiometric fluorescent scaffold giving discrete response towards iodide ion: a combined experimental and DFT study.

A novel ratiometric fluorescent receptor (Z)-2-(4-[diethylamino]-2-hydroxybenzylideneamino) pyridine-3-carbaldehyde (3) bearing one phenolic OH and one aldehyde group as recognition sites was synthesized and characterized. The anion recognition behaviour of receptor 3 was evaluated by various spectroscopic (UV-visible, fluorescence and (1) H nuclear magnetic resonance) methods and was validated by computational studies. The receptor showed fast response time, excellent selectivity and reproducibility towards iodide ion detection among the other surveyed anions, with a binding constant of 6.12 × 10(4) M(-1) and a detection limit of 0.24 µM, thus confirming its potential applicability as a fluorescent sensor for iodide.

Al3+ selective colorimetric and fluorescent red shifting chemosensor: application in living cell imaging.

We report the development of a fluorescent probe based on the benzothiazole unit to monitor intracellular Al(3+) levels in living cells. The fluorescent probe exhibits a fluorescence response towards Al(3+) under physiological conditions with high sensitivity and selectivity and even facilitates naked-eye detection of Al(3+). The fluorescence intensity was significantly quenched with red shifting upon addition of 0.5 equiv. of Al(3+). The simple and cost effective receptor avails rapid detection of Al(3+) ions at concentrations as low as 0.42 µM and is expected to be effective for the design of efficient biological sensor.

Thermodynamic studies of aqueous solutions of 2,2,2-cryptand at 298.15 K: enthalpy-entropy compensation, partial entropies, and complexation with K+ ions.

The osmotic coefficient measurements for binary aqueous solutions of 2,2,2-cryptand (4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8] hexacosane) in the concentration range of ~0.009 to ~0.24 mol·kg(-1) and in ternary aqueous solutions containing a fixed concentration of 2,2,2-cryptand of ~0.1 mol·kg(-1) with varying concentration of KBr (~0.06 to ~0.16 mol·kg(-1)) have been reported at 298.15 K. The diamine gets hydrolyzed in aqueous solutions and needs proper approach to obtain meaningful thermodynamic properties. The measured osmotic coefficient values are corrected for hydrolysis and are used to determine the solvent activity and mean ionic activity coefficients of solute as a function of concentration. Strong ion-pair formation is observed, and the ion-pair dissociation constant for the species [CrptH](+)[OH(-)] is reported. The excess and mixing thermodynamic properties (Gibbs free energy, enthalpy, and entropy changes) have been obtained using the activity data from this study and the heat data reported in the literature. Further, the data are utilized to compute the partial molal entropies of solvent and solute at finite as well as infinite dilution of 2,2,2-cryptand in water. The concentration dependent non-linear enthalpy-entropy compensation effect has been observed for the studied system, and the compensation temperature along with entropic parameter are reported. Using solute activity coefficient data in ternary solutions, the transfer Gibbs free energies for transfer of the cryptand from water to aqueous KBr as well as transfer of KBr from water to aqueous cryptand were obtained and utilized to obtain the salting constant (ks) and thermodynamic equilibrium constant (log K) values for the complex (2,2,2-cryptand:K(+)) at 298.15 K. The value of log K = 5.8 ± 0.1 obtained in this work is found to be in good agreement with that reported by Lehn and Sauvage. The standard molar entropy for complexation is also estimated for the 2,2,2-cryptand-KBr complex in aqueous medium.

Synthesis of core-shell polystyrene nanoparticles by surfactant free emulsion polymerization using macro-RAFT agent.

Novel approach for the synthesis of core-shell polystyrene nanoparticles by living hydrophilic polymer consisting of thiocarbonyl thio end group is reported. The surfactant free emulsion polymerization of styrene in the presence of macro-RAFT (reversible addition fragmentation chain transfer) agent is carried out to synthesize stable latex particles with smaller particle size. A macro-RAFT agent is prepared by homopolymerization of sodium styrene sulfonate (NaSS) in aqueous phase by using dithioester as chain transfer agent. This synthesized polystyrene sulfonate-sodium (PSS-Na) based macro-RAFT agent, which is essentially water soluble macromolecular chain transfer agent used for the surfactant-free batch emulsion polymerization of styrene. Transmission electron microscopy (TEM) study of the synthesized colloids shows the narrow particle size distribution with core-shell morphology.