A selective detection of fluoride ions in DMSO by fluorescent and colorimetry competition assays based on 4-bromo-2,6-bis-(hydroxymethyl)phenol

A novel and very simple colorimetric and fluorometric method for selectively sensing F^- was proposed based on 4-bromo-2,6- bis（hydroxymethyl）phenol（BBHMP）,which is a simple and available phenolic receptor the absence of any special chromophoric function and with over wide range of anions（Cl^-,Br^-,I^-,AcO^-,HSO₄^-,NO₃^- and BzO^-） in DMSO media.The colorimetric method is described for naked-eye detection of F^- in the presence of the BBHMP.The BBHMP was found to show selective and sensitive fluorescence quenching response toward fluoride over than Cl^-,Br^-,I^-,AcO^-,HSO₄^-,NO₃^- and BzO^-.     

Novel thiophene based colorimetric and fluorescent receptor for selective recognition of fluoride ions

A colorimetric anion sensor 2,2′-(1E,1′E)-(thiophene-2,5-diylbis(methan-1-yl-1-ylidene)) was synthesized and characterized by various spectroscopic techniques. Anion binding studies were carried out using UV-visible spectrophotometric titrations and emission spectra studies, revealed that the receptor exhibits selective recognition toward F⁻over other anions. The selectivity for F⁻among the halides is attributed mainly to the hydrogen-bond interaction of the receptor with F⁻. Receptor 1 showed color change from fluorescent green to orange in the presence of tetrabutylammonium fluoride with 1:1 stoichiometry. Receptor 1 exhibits remarkably enhanced fluorescence intensity.     

Formation of a layered framework structure based upon 4-methyl-2,6-bis(methylphosphonic acid) phenol

The trifunctional ligands, [(HO)2P(O)CH2]2C6H2(R)OH, (5-H4)(R = CH3, Br) were prepared in good yield via an Arbusov reaction between P(OEt)3 and the respective 4-R-2,6-bis(chloromethyl)phenols followed by acidic aqueous hydrolysis and they were spectroscopically characterized by IR and NMR techniques. The ligand 5-H4-CH3 readily dissolves lanthanide hydroxide residues and it forms a crystalline complex from aqueous LaCl3 solutions. This complex was characterized by single crystal X-ray diffraction methods and found to adopt a complex 2-D lamellar network in the bc plane. The La(III) inner coordination sphere is seven coordinate formed by oxygen atoms from two water molecules and five phosphonate oxygen atoms from three different ligands. The phenolic oxygen atom is not involved in the ligand binding to La(III).     

A new colorimetric and fluorescent chemosensor based on thiacalix[4]arene for fluoride ions

A new thiacalix[4]arene based fluorescent chemosensor thiacalix[4]arene-N-(quinolin-8-yl)acetamide (TCAN8QA) has been synthesized. TCAN8QA has been found to exhibit highly selective behavior for F⁻ ions among all other anions, that is, Cl⁻, Br⁻, I⁻, PO₄⁻³, OH⁻, H₂PO₄⁻, and CH₃COO⁻ in the absorption spectra as well as in the emission spectra. Red shift and quenching in emission spectra constituting the signature for fluoride detection are due to photoinduced charge transfer (PCT) which can be attributed to deprotonation of acidic NH proton in the presence of fluoride ions.     

A highly selective colorimetric and ratiometric fluorescent chemodosimeter for imaging fluoride ions in living cells

A simple but highly selective colorimetric and ratiometric fluorescent chemodosimeter was designed and synthesized to detect fluoride ions (F(-)) in aqueous solution and living cells by virtue of the strong affinity of F(-) toward silicon.     

Phototriggering of geometric dendrimer disassembly: an improved synthesis of 2,4-bis(hydroxymethyl)phenol based dendrimers

Dendrimers capable of phototriggered disassembly were prepared up to the second-generation using an improved synthesis of 2,4-bis(hydroxymethyl)phenol based dendrimers. It was found that disassembly proceeds to 75-80% completion after 2 h of irradiation at 310 nm for all molecules studied. The lack of complete reaction is attributed to an inefficient photochemical deprotection process rather than the disassembly itself.     

Syntheses and crystal structures of cobalt and nickel complexes of 2,6-bis(hydroxymethyl)pyridine

2?:?1 (L?:?M) Complexes of 2,6-bis(hydroxymethyl)pyridine (dhmp) with different Co(II) salts [CoCl₂·6H₂O, Co(SCN)₂, Co(NO₃)₂·6H₂O, CoSO₄·7H₂O and Co(OTos)₂·6H₂O] and Ni(II) salts [NiCl₂·6H₂O, Ni(NO₃)₂·6H₂O, NiSO₄·7H₂O and Ni(OTos)₂·6H₂O] have been prepared (1–9) and studied by infrared spectroscopy and X-ray crystallography. Influences on the distortion of the coordination polyhedron, the arrangement of the donor atoms and the packing structure of the complexes were investigated in terms of the different kinds of anions and cations. In the metal chloride Complexes 1 and 2, water of hydration was found, while in Complex 3 the counterion (SCN^–) acts as a ligand. The crystal structures of all complexes, except 3, show N₂O₄ hexacoordinated metal ions; in 3 the coordination environment is N₄O₂. Complex 1 is another exception in containing cobalt(III) instead of cobalt(II) as for the other complexes with cobalt salts. Logically, in Complex 1, one of the dhmp ligands is mono-deprotonated. In the neutral Complexes 2 and 4–9, the basal planes of the octahedra are made up of O donors and N atoms occupy the axial positions. In 1 as well as in 3, two N and two O atoms form the base, but in 1 O, and in 3 N atoms are on the axis of the coordination sphere. Moreover, the nickel Complexes 2, 5, 7 and 9 are more symmetrical in structure than the cobalt Complexes 1, 4, 6 and 8, in accordance with the Jahn–Teller effect. Packing structures of the complexes show specific interactions based on strong and weak H-bonds that involve the counterions, hydroxy groups and aromatic units, leading to extended network structures.     

A high selective anion colorimetric sensor based on salicylaldehyde for fluoride in aqueous media

A new and simple salicylaldehyde-based sensor 1 designed for fluoride sensing has been investigated in DMSO and even in the 9/1 DMSO/H₂O (v/v) mixtures. The affinity constants of receptor 1 for anionic species in the 9/1 DMSO/H₂O (v/v) reveal that it is sensitive to F. Also, the color changes induced by anions can provide a way of detection by ‘naked-eye’. These result can be substantiated by the spectrum changes upon the addition of 25 equiv. anions to 1 in the 9/1 DMSO/H₂O solution. The further insights to the nature of interactions between the sensor 1 and F⁻ were investigated by ¹H NMR titration experiments in 9/1 DMSO-d₆/H₂O (v/v). In addition, the proposed binding mode between 1 and F⁻ was suggested.     

A new fluoride selective electrochemical and fluorescent chemosensor based on a ferrocene-naphthalene dyad

A new difunctionalized receptor based on an aza-ferrocenophane structure shows electrochemical and fluorescent responses to fluoride anion.     

2,6-Bis(2-benzimidazolyl)pyridine as a chemosensor for fluoride ions

2,6-Bis(2-benzimidazolyl)pyridine, a neutral tridentate ligand, is employed as a chemosensor for the detection of fluoride ions. The binding of anionic guest species with this ligand is studied using UV-vis spectroscopy, fluorescence spectroscopy, and ¹H NMR techniques. The results indicate that 2,6-bis(2-benzimidazolyl)pyridine can be used as a chemical shift and optical modification based sensor for the detection of fluoride ions.     

Synthesis and properties of novel aromatic polyamides based on 4-aryl-2,6-bis(4-chlorocarbonylphenyl) pyridines

A facile synthesis of three new diacid chlorides containing pyridine ring bearing aromatic type pendant groups on its 4-position is described. The monomers were characterized by FTIR, 1HNMR, mass spectroscopies and elemental analysis. Polycondensation reactions of the prepared diacid chlorides with different commercially available diamines resulted in the preparation of novel polyamides. Optimal conditions for polyamidations were obtained via study of the model compounds. The polymers were characterized by FTIR, 1HNMR, and elemental analysis and their physical properties including solution viscosity, solubility properties, thermal stability and thermal behavior were studied as well. The polyamides show excellent thermal stability and solubility in polar aprotic solvents.     

A novel chemosensor based on Fe(III)-complexation for selective recognition and rapid detection of fluoride anions in aqueous media

A novel fluorogenic receptor 1 was prepared by the reaction of thiosemicarbazide with 1-naphthaldehyde. Based on in situ-formed 1-Fe(III) complexes having the specific binding affinity for F⁻ anions, this sensory system allows rapid recognition and quantitative detection of fluoride in neutral aqueous media in an ‘off-on’ fashion. The fluoride measurement method not only exhibits a low detection limit but also has strong anti-interference ability to common coexisting ions, as evidenced by competitive experiments.     

A novel highly selective fluorescent chemosensor for Hg（Ⅱ） in fully aqueous media

A novel fluorescent Hg~(2 ) chemosensor based on dithia-dioxa-monoaza crown ether was synthesized in four steps from inexpensive starting materials.This new sensor exhibited very strong fluorescence response to Hg~(2 ) (F_(Hg~(2 ))/F_(free)>130) and it was highly selective to Hg~(2 ) over the other metal ions by more than 45-fold.     

Novel fluorimetric bulk optode membrane based on 5,8-bis((5′-chloro-8′-hydroxy-7′-quinolinyl)methyl)-2,11-dithia-5,8-diaza-2,6-pyridinophane for selective detection of lead(II) ions

A novel fluorescence chemical sensor for the highly sensitive and selective determination of Pb²⁺ ions in aqueous solutions is described. The preliminary potentiometric and spectrofluorimetric complexation studies in solution revealed that the lipophilic ligand 5,8-bis((5′-chloro-8′-hydroxy-7′-quinolinyl)methyl)-2,11-dithia-5,8-diaza-2,6-pyridinophane (L2) forms a highly stable and selective [PbL2]²⁺ and [Pb(L2)₂]²⁺ complexes which results in a strong fluorescence quenching of the ligand. Thus, a novel fluorescence Pb²⁺ sensing system was prepared by incorporating L2 as a neutral lead-selective fluoroionophore in the plasticized PVC membrane containing tetrakis(p-chlorophenyl) borate as a liphophilic anionic additive. The response of the sensor is based on the strong selective fluorescence quenching of L2 by Pb²⁺ ions. At pH 5.5, the proposed sensor displays a calibration curve over a wide concentration range of 3.0 × 10⁻⁷ to 2.5 × 10⁻² M with a relatively fast response time of less than 5 min. In addition to high stability, reversibility and reproducibility, the sensor shows a unique selectivity towards Pb²⁺ ion with respect to common coexisting cations. The proposed fluorescence optode was successfully applied to the determination of lead in plastic toys and tap water samples.     

A "turn-on" fluorescent sensor for selective Hg(II) detection in aqueous media based on metal-induced dye formation

A Hg-promoted desulfurization reaction of a thiocarbazone derivative was introduced in the design of a fluorescent sensor for selective Hg(II) detection. Crystal structural and spectroscopic investigations demonstrated the formation of a triazanaphthalene ring and the "turn-on" responding for Hg(II) in aqueous media.     

Methylaluminum complexes based on tridentate 2,6-bis(mercaptoalkyl)pyridine SNS-ligands

New SNS-ligands were obtained by consequent ring-opening of substituted thiiranes by lithiated 2,6-lutidine, mono- functionalized SN-ligands having been isolated as the intermediate compounds. The molecular structure of ligand 2,6-Py(CH₂CH₂CBn₂SH)₂ was elucidated by XRD analysis.The reaction of AlMe₃ with SNS-ligands afforded monomeric methyl aluminum complexes which have been tested in ring- opening polymerization of ε caprolactone in bulk.