Benesi-Hildebrand Plot Research Articles

A highly sensitive and selective colorimetric/fluorescent probe for the detection of Ag+ based on a croconium dye

A novel colorimetric and fluorescent probe, 2,5-bis[3-ethyl-2-methylbenzothiazole]-croconine (BBC) has been synthesized and characterized. The BBC dye can effectively recognize Ag+ in the presence of potentially competitive metal ions (Co2+, Na+, Cd2+, K+, Mg2+, Zn2+, Ca2+, Ba2+, Ni2+, Cr3+, Al3+), which exhibited visible color change and fluorescence spectra behaviors. The Benesi-Hildebrand plot accurately showed the binding constant of BBC-Ag+. Correspondingly, the 1:1 stoichiometric structure of BBC and Ag+ was evaluated by using Job’s plot. Moreover, the complex mechanism of BBC toward Ag+ were also investigated by Fourier transform infrared (FT-IR) and 1H nuclear magnetic resonance (1H NMR). The results indicated that BBC could be used as a high effective colorimetric and fluorescent sensor to identify Ag+.

Salmon sperm DNA binding study to cabozantinib, a tyrosine kinase inhibitor: Multi-spectroscopic and molecular docking approaches

In the current work, the binding interaction of cabozantinib with salmon sperm DNA (SS-DNA) was studied under simulated physiological conditions (pH 7.4) using fluorescence emission spectroscopy, UV–Vis absorption spectroscopy, viscosity measurement, ionic strength measurement, FT-IR spectroscopy, and molecular modeling methods. The obtained experimental data demonstrated an apparent binding interaction of cabozantinib with SS-DNA. The binding constant (Kb) of cabozantinib with SS-DNA evaluated from the Benesi-Hildebrand plot was equal to 5.79 × 105 at 298 K. The entropy and enthalpy changes (∆S0 and ∆H0) in the binding interaction of SS-DNA with cabozantinib were 44.13 J mol−1 K−1 and −19.72 KJ mol−1, respectively, demonstrating that the basic binding interaction forces are hydrophobic and hydrogen bonding interactions. Results from UV–Vis absorption spectroscopy, competitive binding interaction with rhodamine B or ethidium bromide, and viscosity measurements revealed that cabozantinib binds to SS-DNA via minor groove binding. The molecular docking results revealed that cabozantinib fits into the AT-rich region of the B-DNA minor groove and the binding site of cabozantinib was 4 base pairs long. Moreover, cabozantinib has eight active torsions, implying a high degree of flexibility in its structure, which played a significant role in the formation of a stable cabozantinib-DNA complex.

From one to three, modifications of sensing behavior with solvent system: DFT calculations and real-life application in detection of multianalytes (Cu2+, Ni2+ and Co2+) based on a colorimetric Schiff base probe

A rhodamine-based colorimetric sensor, RBOV has been synthesized and modified for selective detection of Cu2+, Ni2+ and Co2+ ions simultaneously in aqueous medium. The difference in color change upon binding with these three cations makes it an interesting multianalyte sensor. Furthermore, the detection limits of RBOV for Cu2+, Ni2+ and Co2+ are down to 4.0 × 10−2 µM, 3.2 × 10−1 µM and 4.8 × 10−1 µM respectively. The possible sensing mechanism analyzed from Benesi-Hildebrand plot, Job's plot, FTIR and DFT studies showed a 1:1 stoichiometry of sensor-metal complex for all three analytes. Practical application of sensor was conducted in real time using test strips and MTT assay was conducted to determine its cytotoxicity.

An integrated approach using ozone nanobubble and cyclodextrin inclusion complexation to enhance the removal of micropollutants

Ozone (O3) has been widely used for the elimination of recalcitrant micropollutants in aqueous environments, due to its strong oxidation ability. However, the utilization efficiency of O3 is constrained by its low solubility and short half-life during the treatment process. Herein, an integrated approach, using nanobubble technology and micro-environmental chemistry within cyclodextrin inclusion cavities, was studied in order to enhance the reactivity of ozonisation. Compared with traditional macrobubble aeration with O3 in water, nanobubble aeration achieved 1.7 times higher solubility of O3, and increased the mass transfer coefficient 4.7 times. Moreover, the addition of hydroxypropyl-β-cyclodextrin (HPβCD) further increased the stability of O3 through formation of an inclusion complex in its molecule-specific cavity. At a HPβCD:O3 molar ratio of 10:1, the lifespan of O3 reached 18 times longer than in a HPβCD-free O3 solution. Such approach accelerated the removal efficiency of the model micropollutant, 4-chlorophenol by 6.9 times, compared with conventional macrobubble ozonation. Examination of the HPβCD inclusion complex by UV–visible spectroscopy and Nuclear Magnetic Resonance analyses revealed that both O3 and 4-chlorophenol entered the HPβCD cavity, and Benesi-Hildebrand plots indicated a 1:1 stoichiometry of the host and guest compounds. Additionally, molecular docking simulations were conducted in order to confirm the formation of a ternary complex of HPβCD:4-chlorophenol:O3 and to determine the optimal inclusion mode. With these results, our study highlights the viability of the proposed integrated approach to enhance the ozonation of organic micropollutants.

Role of Substituent Position in Coumarin Derivatives during their Interaction with TiO2 Nano Particles.

The effect of position of benzo group in coumarin derivatives, 5,6 benzo-4-azidomethyl coumarin (5BAMC) and 7,8 benzo-4-azidomethyl coumarin (7BAMC) during their interaction with TiO2 nanoparticles in ethyl acetate, tetrahydrofuran, butan-1-ol and acetonitrile solvents has been studied using different spectroscopic methods and electrochemical analysis. Benesi-Hildebrand plots indicate that nature of interaction between 7BAMC and TiO2 is 1:2 in solvent with low dielectric constant whereas for 5BAMC and TiO2, it is 1:1 in all the solvents. From the fluorescence quenching study and binding equilibria analysis, it is observed that interaction between 5BAMC and TiO2 depends on the dielectric constant of the solvent. Time resolved quenching study reveals that quenching is dynamic for 5BAMC in solvent with high dielectric constant. Whereas for 7BAMC, it is dynamic in solvent with low dielectric constant. Hence the nature of interaction of these two coumarin derivatives with TiO2 NPs is different. From electrochemical analysis, it is observed that, free energy change for electron transfer is more negative for 5BAMC-TiO2 compared to 7BAMC-TiO2 therefore quenching is more efficient for 5BAMC-TiO2 compared to 7BAMC-TiO2 system, which is also confirmed from fluorescence quenching studies. Non-radiative energy transfer rate is more than radiative energy transfer rate for both the systems according to FRET study.

The relationship between solvatochromic properties and in silico ADME parameters of new chloroethylnitrosourea derivatives with potential anticancer activity and their β-Cyclodextrin complexes

In view of the anticancer effect of nitrosoureas a set of four new N-(2-chloroethyl)-N-nitrosourea (CENU) derivatives was synthesized. An in silico absorption, distribution, metabolism, excretion and toxicity (ADME/Tox) prediction study revealed that the CENU derivatives satisfied all the required criteria for oral administration and introduced them as remarkable anticancer candidates in the central nervous system (CNS). A comparative solvatochromic study including the Kamlet-Taft, Catalán and Laurence models indicated that the solvatochromic behavior of the CENUs depended on both, unspecific and specific solvent–solute interactions. In detail, the solvatochromic effect of the solvent polarity on the absorption and emission maxima was significant for all CENUs, whereas the solvatochromic effect of the solvent’s ability to donate or accept hydrogen bonds on the absorption and emission maxima was critically dependent on the electron density of the N’-aryl group. From the solvatochromic comparison method, excellent correlations (r ≥ 0.890) were obtained between the ADME parameters and the solvatochromic regression coefficients obtained by the Catalán model. As potential stabilizers, inclusion complexes of the investigated CENU derivatives with β-cyclodextrin (β-CD) were also explored. The spectrofluorimetric host–guest experiments included double-reciprocal Benesi-Hildebrand plots as well as the molar ratio and continuous variation plots (Job’s plots), which established a 1:1 β-CD to CENU binding stoichiometry and relatively high affinities of β-CD for CENU derivatives.

Calix[4]amido crown functionalized visible sensors for cyanide and iodide anions.

This study comprises the design and development of calix[4] arene-amido-based ionophores by varying structural stringency and steric hindrance at the lower rim to probe the anion sensing properties. The ionophores are prepared, purified, and characterized using various analytical techniques. The molecular structure of the most active ionophore I is established by single-crystal X-ray characterisation. Out of various anions investigated, iodide and cyanide show the highest sensitivity towards the ionophores investigated. Both anions are sensitive enough to give a visibly distinct color change. The binding properties of the ionophores are established with 1H & 127I NMR, fluorescence, and UV-vis spectroscopy, revealing that three ionophores strongly interact with CN− and I−. The binding constants are calculated via Benesi–Hildebrand plots using absorption data. The time-dependent 1H NMR revealed strong hydrogen bonding between the OH and NH groups of the ionophore and cyanide anion. The 127I NMR shows the highest 27.6 ppm shift after 6 h for ionophore I. The crystal structure revealed hydrogen bonding of N–H protons of the amide pendulum and phenolic oxygen of the calix rim. The Job's plot depicted the possibility of a 1 : 1 complex of ionophores with both anions.

Fabrication of a "turn-on"-type enantioselective fluorescence sensor via a modified achiral MOF: applications for synchronous detection of phenylalaninol enantiomers.

Homochiral metal-organic frameworks (HMOFs) have garnered considerable attention due to their extrachiral properties and broad application for chiral recognition. However, assembling a pair of high-quality chiral MOFs for sensing enantiomers precisely is a formidable challenge because of the complicated chiral environment and uncontrollable coordinated conditions. Herein, one pair of homochiral UiO-66 analogues, S-1 (l-AP@UiO-66-(COOH)2) and R-1 (d-AP@UiO-66-(COOH)2), are reported for chiral recognition. They were fabricated via a condensation reaction between the carboxyl groups of UiO-66-(COOH)2 and amino groups of l/d-amino propanol (l/d-AP). These novel fluorescent probes exhibited highly enantioselective fluorescence enhancement towards l/d-phenylalaninol (l/d-PA). For example, when S-1 and R-1 were treated with l-PA or d-PA, they displayed different fluorescence responses: the enantiomeric fluorescence enhancement ratio (ef) was 2.51 and 0.41 for S-1 and R-1, respectively. Hence, a visible difference in fluorescence enhancement for l-PA and d-PA and excellent enantioselective behavior between S-1 and l-PA (or R-1 and d-PA) was displayed. Measurements of fluorescence lifetime, powder X-ray diffraction, molecular-dynamic simulations and Benesi-Hildebrand plots were employed to determine the observed high enantioselectivity for l/d-PA. In brief, we found that two post-modified HMOFs, S-1 and R-1, were outstanding enantioselective sensors for detecting l-PA and d-PA. They had a prominent difference in ef and remarkable enantioselectivity factor α and ΔΔG based on steric hindrance and stereochemical difference.

Effect of Temperature and Additives on the Interaction of Ciprofloxacin Hydrochloride Drug with Polyvinylpyrrolidone and Bovine Serum Albumin: Spectroscopic and Molecular Docking Study.

The fluoroquinolone antibiotic drug namely ciprofloxacin hydrochloride (CFH) is widely prescribed for the treatment of different bacterial infections. The interaction of CFH with a synthetic polymer, polyvinyl pyrrolidone (PVP), and biopolymer, bovine serum albumin (BSA) was studied by UVvisible and fluorescence spectroscopic methods at different temperatures. The binding constant (K b ) for the CFH-PVP complex was determined from the Benesi-Hildebrand plot. PVP of different molecular weights (MW) (such as 24,000, 40,000, 360,000, and 700,000 g. mole-1) were used for the interaction between CFH and PVP. The gradual increase in K b value and the complexation reaction was found to be much enhanced with the augmentation of the MW of PVP. The values of K b were also found to be increased with increasing temperatures as well as with the increase of electrolyte/acetic acid concentration. The Gibbs free energy of binding (∆G 0) values of the interaction process was negative which indicates the complex formation is thermodynamically spontaneous. The positive values of enthalpy (∆H 0) and entropy (∆S 0) of binding connote that the binding force for CFH-PVP complexation is hydrophobic in nature and the complexation is entropy controlled. The negative intrinsic enthalpy (∆H *,0) values indicate the high stability of CFH-PVP complexes. Molecular docking calculation discloses the existence of similar binding forces between CFH and PVP obtained by the analysis of experimental data from UV-visible spectroscopic method. The binding constant between CFH and BSA (K b ), quenching constant (K sv ), the number of binding sites (n), and the quenching rate constant (K q ) for the CFH-BSA system were also calculated. The values of K sv , K q , and n for the CFH-BSA system are lower in 0.05 mol L-1 urea solution and higher in PVP solutions compared to those of aqueous medium.

Effect of pH and structural orientation on supramolecular complexation of chloroquine in β-cyclodextrin medium

The supramolecular interaction of host-guest structure between Chloroquine (CQ) plus nano-hydrophobic cavity beta-cyclodextrin (β-CD) and the complex has observed by employing techniques such as UV and fluorescence spectroscopy. Here, the compound formed is of 1: 2 stoichiometric ratio. The chloroquine molecule has extremely caught into the cavity of β-cyclodextrin that is established by an in-depth analysis of spectral changes and matching to the absorption and fluorescence spectrometric interpretations. The binding constant for the inclusion complex at room temperature has evaluated by the use of Benesi-Hildebrand plot. The monocation and neutral forms of CQ with moist along with β-CD platform have discussed for the determination of pKa and pKa⁎. The thermal stability for the inclusion complex of CQ with β-CD has been examined by utilizing DSC technique. The change of the crystal arrangement of the substantial complex has substantiated by powder XRD technique. The mechanism of the inclusion complex and its orientation is done by utilizing Patch-Dock server. The cytotoxic exploration has again done to pure CQ along with its inclusion complex on MDA MB 231 cell line; then it is presented that the activity is subtle for the two materials.

1,3-Alternate Calix[4]arene Functionalized With Pyrazole and Triazole Ligands as a Highly Selective Fluorescent Sensor for Hg2+ and Ag+ Ions.

We report here the synthesis of a 1,3-alternate calix[4]arene 8, with bis-pyrazolylmethylpyrenes on the one end and bis-triazolylmethylphenyls on the other end, as a homoditropic fluorescent sensor for both Hg2+ and Ag+ ions. Calix[4]arene 3, with lower-rim bis-pyrazolylmethylpyrenes in cone conformation, was also synthesized as a control compound. UV-Vis and fluorescence spectra were used for metal ions screening, and we found that both ligands 8 and 3 showed strong excimer emission of pyrenes when they are as a free ligand in CHCl3/MeOH (v/v, 3:1) solution; however, they both showed a high selectivity toward Hg2+ and Ag+ ions with strong fluorescence quenching and yet with different binding ratios. The fluorescence of ligand 8 was strongly quenched by Hg2+ but was only partially quenched by Ag+ ions; however, the fluorescence of ligand 3 was strongly quenched by Hg2+, Ag+, and Cu2+ ions. Job plot experiments showed that ligand 8 formed a 1:2 complex with both Hg2+ and Ag+ ions; ligand 3 formed a 1:1 complex with Hg2+, but it formed a 2:3 complex with Ag+. The binding constant of ligand 3 with Hg2+ and Ag+ ions was determined by the Benesi-Hildebrand plot of UV-vis titration experiments to be 2.99 × 103 and 3.83 × 103 M−1, respectively, while the association constant of ligand 8 with Hg2+ and Ag+ was determined by Hill plot to be 1.46 × 1012 and 9.24 × 1011 M−2, respectively. Ligand 8 forms a strong complex with either two Hg2+ or two Ag+ ions using both the upper and lower rims of the 1,3-alternate calix[4]arene as the binding pockets; hence, it represents one of the highly selective fluorescent sensors for the homoditropic sensing of Hg2+ and Ag+ ions.

Studies on the supramolecular complex of a guanosine with beta-cyclodextrin and evaluation of its anti-proliferative activity

The behavior of the inclusion behavior of guanosine (GU) with beta-cyclodextrin (β-CD) in the liquid, solid and virtual state were investigated. The absorption and fluorescence spectral were used to determine the inclusion behavior in liquid state. FT-IR, NMR, TGA, DSC, PXRD and FESEM techniques were used to investigate the inclusion behavior in solid-state, meanwhile the virtual state studies are done by molecular docking. The solid inclusion complex (GU: β-CD) was prepared by using the co-precipitation method. The binding constant (K) of (GU: β-CD) was calculated by using Benesi-Hildebrand. Besides that, the 1:1 stoichiometric ratio of inclusion complex was confirmed by using the Benesi-Hildebrand plot and Job's plot of continuous variation method. The most preferable model of GU: β-CD that suggested via molecular docking studies was in good agreement with experimental results. The inclusion complex of GU: β-CD exerted its toxicity effects towards HepG2 cell lines based on the reduced number of cell viability and lowest IC50 value compared to the GU and β-CD viability.

Host-guest inclusion complex of β-cyclodextrin and 4,4′-(1,4-phenylenediisopropylidene)bisaniline: Spectral, structural and molecular modeling studies

The Host-Guest inclusion complex of β-Cyclodextrin (β-CD) and 4,4′-(1,4-phenylenediisopropylidene)bisaniline (PDB) was prepared in solid and solution state and characterized by UV-Visible, Fluorescence, FT-IR, Time resolved fluorescence spectroscopy, DSC, SEM, AFM, XRD and Molecular modeling approach. These studies were adopted to approve the formation of PDB: β-CD inclusion complex . Job's plot and Benesi-Hildebrand plot obtained by using UV and Fluorescence spectral readings confirmed the 1:2 PDB: β-CD complex formation.. FT-IR study revealed that aromatic rings of PDB are partially encapsulated in to the β-CD cavity. The interaction between PDB and β-CD is shown by enhancement of thermal stability of PDB after the complexation. AFM and SEM analysis were also confirmed inclusion complex formation in solid state. Molecular docking study revealed the fact that 1:2 inclusion complex possesses a good molecular shape complementarity score for its most probable structure.

Novel rhodamine probe for colorimetric and fluorescent detection of Fe3+ ions in aqueous media with cellular imaging.

A novel rhodamine-pyridine conjugated spectroscopic probe RhP was synthesized and its X-ray single crystalline properties were revealed with tabulation. The RhP displayed a distinct pale-pink colorimetric and "turn-on" fluorescent response to Fe3+ in aqueous media [H2O:DMSO (95:5, v/v)] than that of other interfering ions. During the Fe3+ recognition, the absorption (UV-Vis) and photoluminescence (PL) spectral studies revealed new peaks at 561 and 592nm, respectively. The 1:1 stoichiometry and binding sites were verified by Job's plot, ESI-mass, and 1H NMR titrations. Subsequently, LOD and binding constant for RhP+Fe3+ complex were estimated as 102.3nM and 6.265×104M-1 from linear fitting and Benesi-Hildebrand plots, correspondingly. Sensor reversibility of RhP+Fe3+ by EDTA was demonstrated by UV/PL and TRPL investigations. Moreover, the photoinduced energy transfer mechanism and band gap changes were established from the DFT interrogations. Lastly, cellular imaging studies were carried out to authenticate the real applicability of RhP in Fe3+ detection.

Spectroscopic studies of the excited-state intramolecular proton and electron transfer processes of methyl benzoate derivatives in cucurbit[7]uril nanocage

The encapsulation of four methyl benzoate derivatives (I-IV) in aqueous solution in the presence of the macrocyclic host molecule cucurbit[7]uril (CB[7]) was studied using steady-state, time-resolved and 1H NMR spectroscopic techniques. The significant changes in the steady-state and time-resolved fluorescence spectra (and calculated from them fluorescence decay times) were attributed to the formation of a well-defined, stable 1:1 inclusion complex. To understand the mechanism of supramolecular solvation dynamics, the time-dependent fluorescence Stokes' shifts, represented by the normalized spectral response function c(t), were studied. Our studies have shown that solvation dynamics of water are significantly inhibited inside a cucurbit cavity. The experimental results were also used to calculate, according to Benesi-Hildebrand plot and nonlinear least-squares regression analysis, equilibrium constants of the formed inclusion complex. For all investigated dyes, the K1 value is significantly larger than this previously calculated for I-IV inclusion into cyclodextrins (CDs), indicating the superior host abilities of CB[7] as compared to CDs. The position of the guest molecule inside the host cavity was investigated by 1H NMR experiment. The nature of the 1H NMR shifts for different protons is qualitatively different for methoxy derivative-CB[7] complex (I-CB[7] and III-CB[7] systems) and hydroxy derivative-CB[7] complex (II-CB[7] and IV-CB[7] systems), which indicates that the inclusion complexes of hydroxy and methoxy derivatives with CB[7] are of a difference in nature. The CB[7]-induced chemical shifts clearly demonstrate that for II-CB[7] and IV-CB[7] complexes, benzene ring is fully embedded in the interior of CB[7], while for I-CB[7] and III-CB[7] complexes, only the part of the benzene ring is located within the CB[7] cavity. Finally, 1H NMR chemical shifts and evolution of the steady-state and time-resolved emission spectra clearly indicate that -NMe2 group attached to the III and IV is located outside of the CB[7] portal.

Spectrophotometric determination of chloroquine, pyrimethamine and trimethoprim by ion pair extraction in pharmaceutical formulation and urine

A simple and accurate method for the determination of chloroquine diphosphate (CQ), pyrimethamine (PYM) and trimethoprim (TMP) in pure, pharmaceutical and urine samples is described. The method involved an ion pair extraction procedure with chloroform using an acid base indicator, bromocresol purple (BCP), as a counter ion. The ion pair extracted in organic phase was yellow, and the absorbance was measured at λmax = 420 nm. Beer's law was obeyed over the concentration range of 1.25-8.75, 0.62-7.5, and 1.25-10.71 μg/mL, respectively. The Sandell's sensitivity was 0.01258, 0.01102 and 0.01464 μg/cm2. The Ringbom optimum concentration range, which was 2.5-7.5, 1.25-7.5 and 2.5-10.7 μg/mL for CQ, PYM, and TMP, respectively, exhibited reliability of the method. Stoichiometry and thermodynamic of the complexes were evaluated by Job's method and Benesi-Hildebrand plot. The statistical results of intra- and inter-day estimation of drugs and comparison with the reported methods demonstrated high precision and accuracy of the method. The procedure was rapid, simple and suitable for quality control purpose.

Polycyclic aromatic hydrocarbon functionalized organosilocanes based chemosensors: Synthesis, magnetic nanoparticles and biological application

This present work highlights the construction of new chemosensors based on polycyclic aromatic hydrocarbon (PAH) appended organosilocane which have been structurally characterized by various spectroscopic techniques such as IR, NMR, and mass spectrometry. The prepared chemosensors were found to be proficient for the detection of Sn2+ and Cr3+ ions with UV–Visible spectroscopy and Cu2+ ion with fluorescence technique. The limit of detection for Sn2+, Cr3+ and Cu2+ ions turns out to be 5.74 ppb, 5.14 ppb and 0.55 ppm, respectively, as calculated by Benesi-Hildebrand plot and Stern Volmer graph. Moreover, biological applications like total antioxidant activity and cytotoxic studies of the prepared organosilocanes have been evaluated. Total antioxidant activity was of IC50 0.06 ± 0.01 mM and 0.2 ± 0.01 mM, for compounds 3a and 3b, respectively. Interestingly, compound 3a has a noteworthy cytotoxic activity against SAF-1 cell line with EC50 of 4.07 ± 0.32 μM. Further immobilisation of compound 3a onto the surface of magnetic silica (Fe3O4@SiO2) nanoparticles enhanced the properties of chemosensitivity for Sn2+ ion and the limit of detection lowered to 0.1 ppb. The resultant nanoparticles have been characterized by physicochemical techniques such as FT-IR, XRD, EDX, FESEM and TGA.

Spectroscopic studies for the inclusion complexation of ketoprofen enantiomers with β-cyclodextrin.

Inclusion complexes of R-ketoprofen and S-ketoprofen enantiomers with β-cyclodextrin (β-CD) in aqueous solution were studied using various spectroscopic techniques such as Raman, FTIR, UV and fluorescence. The different relative intensities and characteristic band shifts of the two enantiomers from Raman spectra suggests different interaction when complexed with β-CD. Raman experiments revealed a noticeable diminishing of the CC vibration and ring deformation, which indicate the embedding of ketoprofen inside the β-CD cavity. It's revealed that distinct differences between R- and S-ketoprofen in the presence of β-CD at neutral pH. The stoichiometry ratio and binding constant of the inclusion complexes were calculated using Benesi-Hildebrand plot. Both enantiomers showed stoichiometry ratio of 1:1 inclusion complex with β-CD. The binding constant of R-ketoprofen (4088M-1) is higher than S-ketoprofen (2547M-1). These values indicated that β-CD formed inclusion complexes more preferentially with R-ketoprofen than S-ketoprofen. Results demonstrated that β-CD can be used as a promising chiral selector for ketoprofen enantiomers.

A highly selective and sensitive “turn-on” fluorescent probe for rapid recognition and detection of Cu2+ in aqueous solution and in living cells

A 5-formyl-2-hydroxybenzoicacid-based fluorescence probe (L) for Cu2+ ions was designed and synthesized. L in CH3CN:H2O (1:9, v/v) solution displayed highly selective and sensitive fluorescence ‘off-on’ response over all the other competitive metal ions including Fe2+, Fe3+, Mn2+, Ba2+, Pb2+, Co2+, Cr3+, Cd2+, Na+, Zn2+, Hg2+, Ag+, Ca2+, Al3+, Mg2+, K+, Ni2+ and Y3+. The fluorescence intensity of L presented good linear relationship to the Cu2+ concentration and with the lower detection limits of 2.19 × 10−7 M for Cu2+ ion. Job’s plot, mass spectra, Benesi-Hildebrand plot and DFT calculation confirmed that fluorescence increased was caused by the formation of 1:2 complex between L and copper ion. The recovery tests demonstrated that L could accurately detect the existence of Cu2+ ions in water samples. In addition, L can recognize Cu2+ ion in living cells via the fluorescence confocal images and in water samples via test papers mode.

A selective proton transfer optical sensor for copper II based on chelation enhancement quenching effect (CHEQ)

A novel selective fluorescent sensor for Cu2+ in solution has been developed by means of chelation enhancement quenching effect (CHEQ). The compound N,N′-bis(salycilidene)-(2-(3′,4′-diaminophenyl)benzothiazole (BTS) is reactive to intramolecular proton transfer on the electronic excited state (ESIPT) presenting fluorescence emission in the blue region with very large Stokes shift (8794 cm−1). Spectroscopic titration experiments indicate that not only the fluorescence quenching but also of the ESIPT reaction allowed naked eye detection as a paper strip-based sensor. This chemosensor showed to be selective to Cu2+ among 13 other cations. The sensor:Cu2+ ratio was determined by both Job and Benesi-Hildebrand plots as 1:2. In addition, the binding between sensor and metal was investigated by 1H NMR, FTIR and HRMS in order to elucidate the formed complex and corroborate the results of BTS:Cu2+ ratio. The binding constant was also found as 3.0 × 1010 mol−2 L2 at 25 °C. The detection and quantification limits were also obtained as 32 ppb and 108 ppb, respectively.