Synthesis, photophysical properties, and cyanide detection in aqueous solution of BF2-curcumin dyes

Nonlinear Optical Properties and All Optical Switching of Curcumin Derivatives

In this work OR1(E1,6E) -1,7-bis (4-propyloxy phenyl) hepta-1,6-diene-3,5 dione compound is synthesized. The compound has been characterized via computational technique by studying the molecule's electronic structures through calculating its HOMO and LUMO energies, and its band gap energy (EHOMO-ELUMO). The nonlinear refractive index (NLRI) of the solution of OR1 compound in DMF solvent is determined using diffraction patterns (DPs) which resulted when a continuous wave laser beam of wavelength 473 nm traversed the compound solution in a glass cell of 1 mm thickness. By counting the number of rings under maximum beam input power, the NLRI of value 10- 6 cm2/W resulted. The NLRI is calculated once more via the Z-scan technique and a value of 0.25 × 10- 7 cm2/W is obtained. The vertical convection current in the OR1 compound solution appears to be responsible for the asymmetries noticed in the DPs. The temporal variation of each DP is noticed together with the evolution of DPs against beam input power. DPs are numerically simulated based on the Fresnel-Kirchhoff integral with good accord compared to the experimental findings. Dynamic and static all-optical switching in the OR1 compound using two laser beams (473 and 532 nm) is tested successfully.

Curcumin-based molecular probes for fluorescence imaging of fungi

Fluorescence imaging is a powerful and widely used method to visualize and study living organisms. However, fungi are notoriously difficult to visualize using fluorescence microscopy, given that their cell wall represents a diffusion barrier, and the synthetic organic dyes available are very limited when compared to molecular probes available for other organisms. Moreover, these dyes are usually available in only one colour, preventing co-staining experiments. To fill this gap, curcumin-based molecular probes were designed based on the rationale that curcumin is fluorescent and has moderate toxicity toward fungi, implying its ability to cross the cell wall to reach targets in the intracellular compartments. A family of boron diketonate complexes was synthesized, based on a curcumin backbone, tuning their emission color from blue to red. These probes did not present noticeable toxicity to filamentous fungus and, when applied to their visualization, readily entered the cells and precisely localized in sub-cellular organelles, enabling their visualization.

Photophysical and anion sensing properties of a triphenylamine-dioxaborinine trimeric compound

Herein, we report the synthesis and photophysical characterization of the novel tris(4-(2,2-difluoro-6-methyl-2H-1λ³,3,2λ⁴-dioxaborinin-4-yl)phenyl)amine trimeric probe (A2) via the reaction between triphenylamine (1), acetic anhydride, and BF₃·OEt₂ implying the twelve new bond formation in a one-pot manner. This highly fluorescent compound in solution (φ up to 0.91 at 572 nm) and solid state (φ = 0.24 at 571 nm) showed a better solvatofluorochromism than its analog monomeric A1 due to symmetry-broken charge transfer, which is consistent with high solvent dipolarity (SdP) response in Catalán's multiparametric regression. Notably, A2 had a high sensibility and selectivity for CN^- or F^- in solution (LODCN^-/F^- = 0.18/0.70 μM), and CN^- can be discriminated from F^- by the reaction of A2 with 3.0 equiv. of CN^-. In addition, A2 was impregnated on filter paper to prepare test strips that were applied to naked-eye qualitative sensing of CN^- or F^-. Finally, the octupolar system in A2 allows for better action of two-photon excitation cross-section values when compared with that of the dipolar structure in A1. These findings provide further information for the design of new efficient two-photon absorption dyes.

Curcumin Is an Iconic Ligand for Detecting Environmental Pollutants

The rapid increase in industrial revolution and the consequent environmental contamination demands continuous monitoring and sensitive detection of the pollutants. Nanomaterial-based sensing system has proved to be proficient in sensing environmental pollutants. The development of novel ligands for enhancing the sensing efficiency of nanomaterials has always been a challenge. However, the amendment of nanostructure with molecular ligand increases the sensitivity, selectivity, and analytical performance of the resulting novel sensing platform. Organic ligands are capable of increasing the adsorption efficacy, optical properties, and electrochemical properties of nanomaterials by reducing or splitting of band gap. Curcumin (diferuloylmethane) is a natural organic ligand that exhibits inherent fluorescence and electrocatalytic property. Due to keto-enol tautomerism, it is capable of giving sensitive signals such as fluorescence, luminescence, ultraviolet absorption shifts, and electrochemical data. Curcumin probes were also reported to give enhanced meterological performances, such as low detection limit, repeatability, reproducibility, high selectivity, and high storage stability when used with nanosystem. Therefore, research on curcumin-modified nanomaterials in the detection of environmental pollution needs a special focus for prototype and product development to enable practical use. Hence, this article reviews the role of curcumin as a natural fluorophore in optical and electrochemical sensing of environmentally significant pollutants. This review clearly shows that curcumin is an ideal candidate for developing and validating nanomaterials-based sensors for the detection of environmental pollutants such as arsenic, lead, mercury, boron, cyanide, fluoride, nitrophenol, trinitrotoluene, and picric acid and toxic gases such as ammonia and hydrogen chloride. This review will afford references for future studies and enable researchers to translate the lab concepts into industrial products.

2-Chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]styryl}pyrimidine: Synthesis, Spectroscopic and Computational Evaluation

A novel curcumin analog namely 2-chloro-4,6-bis{(E)-3-methoxy-4-[(4-methoxybenzyl)oxy]-styryl}pyrimidine (compound 7) was synthesized by three-step reaction. The condensation reaction of protected vanillin with 2-chloro-4,6-dimethylpyrimidine (6) was the most efficient step, resulting in a total yield of 72%. The characterization of compound 7 was performed by 1H and 13C nuclear magnetic resonance (NMR), as well as high-resolution mass spectrometry. The experimental spectrometric data were compared with the theoretical spectra obtained by the density functional theory (DFT) method, showing a perfect match between them. UV-visible spectroscopy and steady-state fluorescence emission studies were performed for compound 7 in solvents of different polarities and the results were correlated with DFT calculations. Compound 7 showed a solvatochromism effect presenting higher molar extinction coefficient (log ε = 4.57) and fluorescence quantum yield (ϕ = 0.38) in toluene than in acetonitrile or methanol. The simulation of both frontier molecular orbitals (FMOs) and molecular electrostatic potential (MEP) suggested that the experimental spectra profile in toluene was not interfered by a possible charge transfer. These results are an indication of a low probability of compound 7 in reacting with unsaturated phospholipids in future applications as a fluorescent dye in biological systems.

An insight into the in vivo imaging potential of curcumin analogues as fluorescence probes

Curcumin and its derivatives have good electrical and optical properties due to the highly symmetric structure of delocalized π electrons. Apart from that, curcumin and its derivatives can interact with numerous molecular targets, thereby exerting less side effects on human body. The fluorescence emission wavelength and fluorescence intensity of curcumin can be enhanced by modifying its π-conjugated system and ß-diketone structure. Some curcumin-based fluorescent probes have been utilized to detect soluble/insoluble amyloid-ß protein, intracranial reactive oxygen species, cysteine, cancer cells, etc. Based on the binding characteristics of curcumin-based fluorescent probes with various target molecules, the factors affecting the fluorescence intensity and emission wavelength of the probes are analyzed, in order to obtain a curcumin probe with higher sensitivity and selectivity. Such an approach will be greatly applicable to in vivo fluorescence imaging.

Synthesis and photophysical properties of ditrifluoroacetoxyboron complexes with curcumin analogues

A new class of ditrifluoroacetoxyboron complexes were designed and synthesized by chelation reaction of curcumins with boron trifluoroacetate. Their photophysical behaviors were studied in different solvents, powder state and PMMA polymer films. The results indicated that these complexes revealed a green to yellow emission at 486-595 nm in solution or PMMA films and an orange to red emission at 598-710 nm in powder state. Especially, complex 2c displayed the strongest emission intensity, the highest quantum yield in solution and the longest fluorescence lifetime in powder state in these complexes. In addtion, the emission bathochromic shifts of these complexes as a function of the solvent polarity parameter E_T(30) were investigated by Lippert-Mataga approximation. It was observed that these complexes exhibited the higher values of the dipole moment difference (Δμ) between the ground and excited states, which implied an intense intramolecular charge transfer characteristics and a noticeable emission solvatochromic effect.

The Decoration of ZnO Nanoparticles by Gamma Aminobutyric Acid, Curcumin Derivative and Silver Nanoparticles: Synthesis, Characterization and Antibacterial Evaluation

Zinc oxide nanoparticles (ZnO NPs) are applied in various applications in catalysis, biosensing, imaging, and as antibacterial agents. Here we to prepare ZnO nanomaterials decorated by γ-amino butyric acid (GABA), curcumin derivatives (CurBF₂) and silver nanoparticles (CurBF₂-AgNPs). The structures of all ZnO nanostructures were characterized using Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), UV-VIS spectrophotometry, fluorescence spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HR-TEM). Further, their antibacterial activities against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria were investigated through analysis of minimum inhibitory concentration (MIC) method. Among the prepared nanostructures, the ZnO NPs-GABA/CurBF₂-AgNPs showed excellent antibacterial activity against both Gram-positive and -negative bacteria. ZnO NPs fabricated here may have potential use in future anti-bacterial compositions and coatings technologies.

The nonlinear optical properties of two dihydropyridones derived from curcumin

Two dihydropyridone compounds are synthesized from curcumin using microwave radiation. Both compounds were identified by their melting points and ¹HNMR spectra. The nonlinear properties viz., nonlinear absorption coefficients and nonlinear refractive index of both compounds were calculated at wavelength 473 nm using the diffraction ring patterns and Z-scan techniques separately. The diffraction ring patterns evolved from circular symmetric to asymmetric due to convection current in the vertical direction. As a result of using Gaussian laser beam, the Fraunhofer approximation of the Fresnel-Kirchhoff diffraction, have led to successful simulation of the diffraction ring patterns with good quantitative and excellent qualitative agreements compared with experimental results. Optical limiting property has been tested in both compounds.

Difluoroboron-Curcumin Doped Starch Film and Digital Image Colorimetry for Semi-Quantitative Analysis of Arsenic

This work presents a novel, simple, rapid, and cost effective method for semi-quantitative analysis of arsenic(III) in water sample. The method was based on the digital image colorimetry (DIC) of difluoroboron-curcumin doped starch film (BF₂-cur-film) and arsenic ion in water. A red BF₂-cur-film (9.4 μm) was fabricated by entrapped difluoroboron-curcumin (BF₂-curcumin, particle size of 60 - 113 nm) in tapioca starch film. When the standard solution of arsenic (1 mL) was added into small plastic tube containing BF₂-cur-film on its inner lid, blue solution (λ_max at 610 nm) was observed instead of orange color in blank solution (λ_max at 495 nm). When BF₂-cur-film was used in conjunction with DIC, a wide linear range of 0 - 10 mg L^-1 with good linearity (R² > 0.99) was obtained from green channel with low detection limit of 0.04 mg L^-1. Moreover, good precision (0.9 - 1.2%RSD, n = 4 days) and accuracy (0.03% relative error) were also achieved.

Synthesis, photophysical properties and theoretical studies of new bis-quinolin curcuminoid BF2-complexes and their decomplexed derivatives

This paper presents the synthesis and characterization of two series of new bis-quinolin curcuminoid BF₂-complexes 11 and their respective decomplexed bis-quinolin curcuminoid derivatives 12, in an attempt to understand their optical properties. The synthesized compounds showed interesting fluorescent characteristics in both solution and in solid-state. The characteristic of the electronic transitions involved in these systems were measured via Uv-vis spectroscopy and fluorescence spectroscopy. Results revealed that the absorption and emission bands are dependent of the structure of compounds 11 and 12 but also of the type of substituent, even showing a push-pull behavior in those derivatives substituted with methyl group. These findings were also confirmed through computational calculations at DFT level via simulations of the Uv-vis spectra and determining the topology of the border orbitals responsible for light absorption.

Pyridine-hydrazone-controlled cyanide detection in aqueous media and solid-state: tuning the excited-state intramolecular proton transfer (ESIPT) fluorescence modulated by intramolecular NH⋯Br hydrogen bonding

A new efficient pyridine-hydrazone-substituted naphthalimide receptor 4a-E has been synthesized as a selective colorimetric and fluorescent chemosensor for cyanide sensing in aqueous environments through a unique ESIPT mechanism.

Synthesis, photophysical and solvatochromic properties of diacetoxyboron complexes with curcumin derivatives

Five novel diacetoxyboron complexes of β-diketones incorporated curcumin moiety were designed and synthesized. Their photophysical behaviors were investigated by UV-vis absorption and fluorescence spectroscopy in different solvents and solid state. It was observed that their fluorescence spectra yielded a blue to yellow-green emission in solution and emitted a yellow to red emission in solid state. Especially, the complex 3b displayed the strongest emission and the highest quantum efficiency (Φ_u = 0.98) in toluene among these complexes. The CIE coordinate of the complex 3b in solid state was positioned in an ideal red region of the chromaticity diagram. The maximal emission of these complexes exhibited a large wavelength shift and Stokes shift increased with the increase of the solvent polarity. Their dipole moment differences between the ground and excited states were also estimated by using the Lippert-Mataga equation. Meanwhile, their HOMO, LUMO energy levels and energy band gaps were calculated by cyclic voltammetry.

Effect of substitution on the excited state photophysical and spectral properties of boron difluoride curcumin complex dye and their derivatives: A time dependent-DFT study

The optical, charge transport and electronic properties of boron difluoride curcumin (BFC) complex have been explored using the DFT (Density Functional Theory) method and B3LYP functional with the combination of 6-31 + G(d,p) as a basis set. The influence of substitution with various electron releasing and withdrawing groups on the above properties is analyzed and discussed in this work. The results reveal that the BFC complex on additional electron releasing substitution experiences redshifts in the optical transitions, and this is correlated with the dipole moment, NBO charges, HOMO-LUMO energy gap. Further, the absorption (λ_abs) and emission (λ_ems) spectra of substituted and unsubstituted BFCs are calculated using Time-Dependent Density Functional Theory (TD-DFT). The results show that the electron releasing groups strongly influence the absorption and emission spectra of BFC. Electron releasing groups in BFC derivatives generate the wavelength shift (Bathochromic), but the electron-withdrawing groups in BFC don't affect the λ_abs and λ_ems when compare to its original (parent) compound. The output of the research work strongly recommends that the amino, phenyl and N, N'-dimethylamino derivatives are potential candidates to act as fluorescent materials due to enhance the emission behavior of BFC and also can be used as an electron/charge transport material for organic light-emitting diodes (OLEDs).

The role of curcumin and its derivatives in sensory applications

Curcumin has recently attracted much attention due to the wide range of its physiological actions such as anti-tumor, anti-inflammatory, anti-thrombotic, anti-diabetic and anti-microbial effects. This phytochemical can be used as a sensing material for the detection of chemicals due to its optical properties as a fluorescent polyphenol. Curcumin and its derivatives can make complexes with many cations such as Cu²⁺, Fe²⁺, Hg²⁺, Pt²⁺, Re³⁺ and Al³⁺via bearing 1,3-diketones with keto-enol isomerization. The complexation of curcumin with certain metal ions leads to its solubility in water and producing various hues of colors as well as cytotoxic and antimicrobial effects. Curcumin can also form complexes with certain metal ions and thus serve as a chelating agent for anions such as ClO^-, CN^-, F^- and S^2-. Moreover, conjugation of curcumin with some organic compounds such as cysteine and poly-glycerol acrylate provides an efficient fluorescence detection system for picric acid and 2-vinyl pyridine in aqueous media. In this review, we focused on curcumin as a key element in a membrane composition of chemical sensors. In addition, the latest sensing platforms based on curcumin and its derivatives are briefly described.

Electrospun Nanobelt-Shaped Polymer Membranes for Fast and High-Sensitivity Detection of Metal Ions

Until now, no polymer nanobelt-shaped materials have been developed as electrochemical, optical, and mass sensors. In this work, we first develop polymer nanobelt-shaped membranes for fast and high-sensitivity detection of metal ions, which are fabricated by a new nanobelt-based processing method with simultaneous zein matrix cross-linking and curcumin cross-linking. Their morphologies, optimal detection pH, ion selectivity, and ion detection sensitivity are systematically analyzed. The limits of detection of electrospun curcumin-loaded zein membranes with a detection time of 0.5 h are as follows: cross-linked nanobelt-shaped membranes (0.3 mg/L) < uncross-linked nanobelt-shaped membranes (1 mg/L) ≈ cross-linked nanofibrous membranes (1 mg/L) < uncross-linked nanofibrous membranes (3 mg/L). The cross-linked nanobelt-shaped membranes are also applied to detect Fe³⁺ in drinking water and environmental water. Finally, the mechanisms of Fe³⁺ detection by these membranes are studied and discussed. The results demonstrate that the difference of limit of detection is dependent on if the curcumin sensor is cross-linked or not and the membrane nanostructures (nanobelts or nanofibers). Cross-linking produces stable sensor molecules on the surface and therefore induces low limits of detection. Compared with nanofibers, nanobelts have a higher surface-to-volume ratio and can have more sensor molecules on their surfaces and therefore have lower limits of detection. In addition, the as-prepared membranes had good membrane storage stability (at least 3 months at room temperature). All of these results suggest that cross-linked electrospun nanobelt-shaped membranes by a new nanobelt-based processing method are ideal platforms for sensing. We believe that they will attract increasing attention in scientific and engineering fields such as materials, environmental, and food science.

Substituted 2-Aminobenzothiazoles Salicylidenes Synthesis and Characterization as Cyanide Sensors in Aqueous Medium

(E)-2-((benzo[d]thiazol-2-ylimino)methyl)-4-nitrophenol 1 and (E)-2-(((6-methoxybenzo[d]thiazol-2-yl)imino)methyl)-4-nitrophenol 2 were synthesized efficiently under microwave conditions. The structures were confirmed using IR, ¹H NMR, and 13C NMR. UV-vis. Fluorescence investigations demonstrated that 1 and 2 are sensitive and selective sensors for detection of cyanide over all other anions SCN−, AcO−, N₃−, H₂PO₄−, H₂AsO₄−, F−, Cl−, Br−, and I− in aqueous media. Cyanide induces colorimetric change from pale yellow to dark yellow and from transparent to pale yellow for 1 and 2, respectively. It enhances the absorption at wavelengths 385 nm and 425 nm of 1 and 385 nm and 435 nm of 2. Acidic anions H₂PO₄− and H₂AsO₄− displayed significant interference with the interaction of cyanide and sensors 1 and 2. Sensor 1 has lower detection limit (LDL) 1 × 10−6 M, while 2 has LDL 1.35 × 10−6 M.

A new azine derivative colorimetric and fluorescent dual-channel probe for cyanide detection

A novel azine derivative colorimetric and fluorescent dual-channel probe salicylaldehyde hydrazine-3,5-dibromosalicylaldehyde (1) has been designed, synthesized and characterized. The probe 1 is confirmed to have especial selectivity and good sensitivity on detecting CN^- via UV-vis absorption and fluorescence spectrum in aqueous solution (H₂O/DMSO, 1:4, v/v). This colorimetric and fluorescent dual-channel probe response to CN^- owed to the deprotonation process and established the mechanism by using ¹H NMR spectroscopy. Further researches showed that the detection limit of the probe 1 to CN^- anions is 8.01×10^-9M, significantly lower than the maximum level 1.9×10^-6M in potable water from WHO guidelines.

Self-assembly of Gd3+/SDS/HEPES complex and curcumin entrapment for enhanced stability, fluorescence image in cellular system

At present, strategies to disperse hydrophobic molecules in water without altering their chemical structures include conventional surfactant-based micellar and vesicular systems, encapsulation into water dispersible polymeric nanoparticles, and loading onto the surface of various metal nanoparticles. Here, we report a simple and low cost platform to incorporate hydrophobic molecules into a stable water dispersible nanostructure that can significantly increase the stability of the encapsulated materials. The platform is based on the incorporation of hydrophobic molecules into the self-assembled complex of gadolinium ion (Gd³⁺), sodium dodecyl sulfate (SDS), and 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) called GdSH. After being incorporated, the two model hydrophobic dyes, curcumin and curcumin borondifluoride show approximately 50% and 30% improved stability, respectively. Investigation of the self-assembled 10-14 multilayered 60nm spheres with inter-layer distances of 4.25nm indicates coordination of SDS and HEPES with Gd³⁺. Incorporation of the hydrophobic molecules into the multilayered spheres results in reduction of the interlayer distance of the multilayer spheres to 4.17nm, suggesting enhanced packing of the hydrophobic chain of SDS and HEPES around the Gd³⁺. The incorporation of the two curcuminoids into the self-assembled complex also causes an increase in fluorescence quantum yield of the two dyes, thus suggesting spatial confinement of the packed dye molecules. The better cellular uptake of the nanoparticles is responsible for the expected enhancement in fluorescence image of the encapsulated materials.

Curcumin, a Compound from Natural Sources, a True Scientific Challenge - A Review

Curcumin, a plant-derived polyphenolic compound, naturally present in turmeric (Curcuma longa), has been the subject of intensive investigations on account of its various activities. The implementation of safe, beneficial and highly functional compounds from natural sources in human nutrition/prevention/therapy requires some modifications in order to achieve their multi-functionality, improve their bioavailability and delivery strategies, with the main aim to enhance their effectiveness. The low aqueous solubility of curcumin, its rapid metabolism and elimination from the body, and consequently, poor bioavailability, constitute major obstacles to its application. The main objectives of this review are related to reported strategies to overcome these limitations and, thereby, improve the solubility, stability and bioavailability of curcumin. The effectiveness of curcumin could be greatly improved by using nanoparticle-based carriers. The significance of the quality of a substance delivery system is reflected in the fact that carrying curcumin as a food additive/nutrition also means carrying the active biological product/drug. This review summarizes the state of the art, and highlights some examples and the most significant advances in the field of curcumin research.

Luminescent Difluoroboron β-Diketonate PLA-PEG Nanoparticle

Luminescent difluoroboron β-diketonate poly(lactic acid) (BF₂bdkPLA) materials serve as biological imaging agents. In this study, dye structures were modified to achieve emission colors that span the visible region with potential for multiplexing applications. Four dyes with varying π-conjugation (phenyl, naphthyl) and donor groups (-OMe, -NMe₂) were coupled to PLLA-PEG block copolymers (∼11 kDa) by a postpolymerization Mitsunobu reaction. The resulting dye-polymer conjugates were fabricated as nanoparticles (∼55 nm diameter) to produce nanomaterials with a range of emission colors (420-640 nm). For increased stability, dye-PLLA-PEG conjugates were also blended with dye-free PDLA-PEG to form stereocomplex nanoparticles of smaller size (∼45 nm diameter). The decreased dye loading in the stereoblocks blue-shifted the emission, generating a broader range of fluorescence colors (410-620 nm). Tumor accumulation was confirmed in a murine model through biodistribution studies with a red emitting dimethyl amino-substituted dye-polymer analogue. The synthesis, optical properties, oxygen-sensing capabilities, and stability of these block copolymer nanoparticles are presented.

Multifunctional organic dyes: anion-sensing and light-harvesting properties of curcumin boron complexes

Organoboron compounds containing curcumin (i.e. natural phenols) were synthesised as a new type of multifunctional organic dye.

Influence of the electron donor groups on the optical and electrochemical properties of borondifluoride complexes of curcuminoid derivatives: a joint theoretical and experimental study

The optical and electrochemical properties of borondifluoride complexes of curcuminoids differently substituted with lateral aromatic and/or meso groups were systematically investigated.

CRANAD-1 as a cyanide sensor in aqueous media: a theoretical study

The lethal toxicity of cyanide ions to animals and the environment has led to considerable research into the development of methods for rapid and sensitive cyanide detection.

Mechanochemical synthesis of 2,2-difluoro-4, 6-bis(β-styryl)-1,3,2-dioxaborines and their use in cyanide ion sensing

The conversion of arylaldehydes to 1,7-diaryl-5-hydroxyhepta-1,4,6-trien-3-ones (curcuminoids) and the mechanochemical cyclization of these products to 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines using BF3-Et2O are described. Investigation of the cyanide ion sensing ability of the 2,2-difluoro-4,6-bis(β-styryl)-1,3,2-dioxaborines, in relation to the substituent groups on the aryl ring, showed that a hydroxy susbstituent is required, preferably para to the intervening carbon bridge.

Facile synthesis of highly fluorescent BF2 complexes bearing isoindolin-1-one ligand

A new class of isoindolin-1-one based BF₂ complexes containing pyridine or benzothiazole groups has been prepared from a “one-pot” reaction.

Syntheses and photophysical properties of BF2 complexes of curcumin analogues

Highly photostable π-extended curcumin-BF₂ complexes with strong absorption and fluorescence ranging from 400 to 800 nm were reported.

A novel development of dithizone as a dual-analyte colorimetric chemosensor: detection and determination of cyanide and cobalt (II) ions in dimethyl sulfoxide/water media with biological applications

The behavior of dithizone (DTZ), an easily available dye has been studied for the first time in chromogenic sensing of CN(-) as an anionic species and for Co(2+) as a cationic species in DMSO/H2O media. So employing DTZ an efficient colorimetric chemosensor was afforded with a chromogenic selectivity for Co(2+) over other cations with detection limit of 0.04 μmol L(-1). The complex of Co(2+) with DTZ also displayed ability to detect up to 0.43 μmol L(-1) CN(-) (K(+) salts) among other competing anions through a fast response time of less than 30s which is much lower than most recently reported chromogenic probes. The linear dynamic ranges for the determination of Co(2+) and CN(-) were 0.3-4.4 and 3.3-58.6 μmol L(-1) respectively. This method could have potential application in a variety of cases requiring rapid and accurate analysis of Co(2+) and CN(-) for human serum and water samples.

Synthesis and photophysical properties of difluoroboron complexes of curcuminoid derivatives bearing different terminal aromatic units and a meso-aryl ring

The synthesis of nine curcuminoids and their difluoroboron complexes is described, with seven of them containing a meso-phenyl ring. Dynamic (19)F NMR confirmed the fact that rotation of that meso-aryl fragment is restricted in the latter systems at room temperature and become allowed at higher temperature (>45 °C). The molecular structure of a meso-substituted derivative in the solid state showed that the phenyl ring lies in a highly twisted plane with respect to the mean curcuminoid plane. The photophysical properties of the nine compounds were investigated in solvents of different polarity. Meso-substitution with a phenyl ring has little influence on fluorescence emission properties in solution, radiative and nonradiative kinetic constants being similar for meso- and nonsubstituted compounds, which is in contrast to the case of BODIPY derivatives. However, introduction of an electron donor p-methoxy group at the meso-phenyl ring leads to small perturbation of the curcuminoid π-system fluorescence emission. We also report the influence of the meso-phenyl group on the emission properties of the aggregated solids.

BF3·OEt2-Promoted Concise Synthesis of Difluoroboron-Derivatized Curcumins from Aldehydes and 2,4-Pentanedione

A concise and one-pot cascade method has been developed to achieve the synthesis of difluoroboron-derivatized curcumins (BF₂C). Treatment of 2,4-pentanedione with BF₃·OEt₂, followed by condensation with aldehydes in the presence of tributyl borate and butylamine at 65 °C in toluene furnished the corresponding symmetric (s-BF₂C) and unsymmetric difluoroboron-derivatized curcumins (us-BF₂C) in good (60 - 99%) and moderate yields (23 - 42%) within 6 - 12 h, respectively.

Chromogenic and fluorogenic chemosensors and reagents for anions. A comprehensive review of the years 2010-2011

This review focuses on examples reported in the years 2010-2011 dealing with the design of chromogenic and fluorogenic chemosensors or reagents for anions.

Self-assembled coordination nanoparticles from nucleotides and lanthanide ions with doped-boronic acid-fluorescein for detection of cyanide in the presence of Cu2+ in water

The sensor molecule, F-oBOH, containing boronic acid-linked hydrazide and fluorescein moieties was synthesized. For anion sensing applications, F-oBOH was studied in aqueous media. Unfortunately, F-oBOH was found to be hydrolyzed in water. Therefore, a new strategy was developed to prevent the hydrolysis of F-oBOH by applying self-assembly coordination nanoparticles network (F-oBOH-AMP/Gd(3+) CNPs). Interestingly, the nanoparticles network displayed the enhancement of fluorescent signal after adding Cu(2+) following by CN(-). The network, therefore, possessed a high selectivity for detection of CN(-) compared to other competitive anions in the presence of Cu(2+). Cyanide ion could promote the Cu(2+) binding to F-oBOH incorporated in AMP/Gd(3+) CNPs to give the opened-ring form of spirolactam resulting in the fourfold of fluorescence enhancement compared to Cu(2+) complexation without CN(-). Additionally, the log K value of F-oBOH-AMP/Gd(3+) CNPs⊂Cu(2+) toward CN(-) was 3.97 and the detection limits obtained from naked-eye and spectrofluorometry detections were 20μM and 4.03μM, respectively. The proposed method was demonstrated to detect CN(-) in drinking water with high accuracy.