A Schiff base-derived new model compound for selective fluorescence sensing of Cu(II) and Zn(II) with ratiometric sensing potential: Synthesis, photophysics and mechanism of sensory action

Hydrazine bridged coumarin-pyrimidine conjugate as a highly selective and sensitive Zn2+ sensor: Spectroscopic unraveling of sensing mechanism with practical application

We report the synthesis and Zn²⁺ sensing of a novel coumarin-hydrazine conjugate 3-{1-[(4, 6-Dimethyl-pyrimidin-2-yl)-hydrazono]-ethyl}-chromen-2-one (3). Compound 3 can act as a neat fluorescent Zn²⁺ sensor by an increment in fluorescence intensity along with an appreciable red shift. Fluorescence enhancement is caused by complexation through cis-trans isomerization process in the presence of Zn²⁺ ion. The practical utility of 3 was demonstrated by successful test kit experiment to detect Zn²⁺ in water under UV-light.

A new rhodamine-based colorimetric chemosensor for naked-eye detection of Cu(2+) in aqueous solution

A new colorimetric probe 1 based on rhodamine B lactam was developed for naked-eye detection of Cu(2+). The optical feature of 1 for Cu(2+) was investigated by UV-vis absorption spectroscopy. Upon the addition of Cu(2+), the 1 displayed a distinct color change from colorless to pink, which can be directly detected by the naked eye. The stoichiometry of 1 to Cu(2+) complex was found to be 1:1 and the naked-eye detection limit was determined as low as 2 μM. The results suggest that the probe 1 may provide a convenient method for visual detection of Cu(2+) with high sensitivity.

A novel pyrazole based single molecular probe for multi-analyte (Zn2+ and Mg2+) detection in human gastric adenocarcinoma cells

A newly designed fluorescent sensor 5-methyl-1H-pyrazole-3-carboxylic acid (6-methoxy-naphthalen-2-ylmethylene)-hydrazide (PYN) shows excellent selectivity and sensitivity with a fluorescence enhancement towards Zn²⁺ and Mg²⁺ ions in aqueous acetonitrile solution.

Highly selective and sensitive colorimetric and fluorescent chemosensor of Fe3+ and Cu2+ based on 2,3,3-trimethylnaphto[1,2-d] squaraine

2,3,3-trimethylnaphto[1,2-d]pyrrole squaraine (TPSQ) based dual signaling probe was found to exhibit selective colorimetric and fluorescent properties on binding towards Fe³⁺ and Cu²⁺ in ethanol/water (4 : 1, v/v) solution, respectively.

Inverse Temperature Dependence in Static Quenching versus Calorimetric Exploration: Binding Interaction of Chloramphenicol to β-Lactoglobulin

The binding interaction between the whey protein bovine β-lactoglobulin (βLG) with the well-known antibiotic chloramphenicol (Clp) is explored by monitoring the intrinsic fluorescence of βLG. Steady-state and time-resolved fluorescence spectral data reveal that quenching of βLG fluorescence proceeds through ground state complex formation, i.e., static quenching mechanism. However, the drug-protein binding constant is found to vary proportionately with temperature. This anomalous result is explained on the basis of the Arrhenius theory which states that the rate constant varies proportionally with temperature. Thermodynamic parameters like ΔH, ΔS, ΔG, and the stoichiometry for the binding interaction have been estimated by isothermal titration calorimetric (ITC) study. Thermodynamic data show that the binding phenomenon is mainly an entropy driven process suggesting the major role of hydrophobic interaction forces in the Clp-βLG binding. Constant pressure heat capacity change (ΔCp) has been calculated from enthalpy of binding at different temperatures which reveals that hydrophobic interaction is the major operating force. The inverse temperature dependence in static quenching is however resolved from ITC data which show that the binding constant regularly decreases with increase in temperature. The modification of native protein conformation due to binding of drug has been monitored by circular dichroism (CD) spectroscopy. The probable binding location of Clp inside βLG is explored from AutoDock based blind docking simulation.

Two fluorescent Schiff base sensors for Zn2+: the Zn2+/Cu2+ion interference

While theenol-iminetautomer inL1exhibits Zn²⁺/Cu²⁺ion interference, theketo-enaminetautomer inL2recognizes only Zn²⁺.

A new pyridoxal based fluorescence chemo-sensor for detection of Zn(ii) and its application in bio imaging

A new pyridoxal-based chemosensor (PydDmen) was reported for selective detection of Zn²⁺ in solution. The experimental and theoretical supports are provided to establish Zn²⁺ induced transformation of PydDmen to 3-pyridone tautomeric form.

A new pyrene-based Schiff-base: a selective colorimetric and fluorescent chemosensor for detection of Cu(II) and Fe(III)

A new receptor 1 was prepared, for the detection of Cu2+ and Fe3+ in solutions as a colorimetric and fluorescent sensor, respectively. Receptor 1 shows highly selective and sensitive recognition toward Cu2+ and Fe3+ by naked eye UV-Vis and fluorescent color changes in aqueous solution (DMSO/H2O=8/2, v/v), respectively. The sensitivity toward Cu2+ or Fe3+ was not interfered with by the presence of other metal ions such as Mg2+, Cd2+, Ag+, Zn2+, Ni2+, Co2+, Mn2+, Cr3+, Ca2+, Na+, Pb2+, K+, Fe2+, Li+ and Hg2+ ions. Receptor 1 can be used for semi-quantitative recognition of Cu2+ ions at ppm level. The fluorescence microscopy experiments showed that the receptor is efficient for detection of Fe3+ in vitro, developing a good image of the biological organelles.