Thiazole-based chemosensor II: synthesis and fluorescence sensing of fluoride ions based on inhibition of ESIPT

Novel chemosensors based on 2-(2′-hydroxyphenyl)-4-phenylthiazole were synthesized and their anion sensing behaviors were investigated. Sensors 1 and 2 show fluoride ion selective behaviors related to their absorption and emission spectra amongst F^?, CH₃CO₂ ^?, H₂PO₄ ^?, Cl^?, Br^?, I^?, ClO₄ ^?, NO₃ ^?, and HSO₄ ^? anions. Sensor 2 shows color change upon interaction with F^?. Interactions of 1, 2 and 3 with F^? cause a red-shift in UV–vis absorption and a large Stokes shift in fluorescence emission due to the inhibition of ESIPT induced by the deprotonation of phenolic proton by F^?.     

5-(1H-Indol-3-yl)-pyrazolyl derivatives as colorimetric sensor for anions

The synthesis, characterisation and binding and deprotonation studies with anions for four 5-(1H-indol-3-yl)-pyrazolyl derivatives (2–5) have been described. It is worthy to mention that sensor 2 shows a drastic change in absorption spectrum (ca. 335 nm) and colour (colourless to blue) upon addition of F^? in DMSO solution due to the deprotonation of indole –NH proton, as confirmed by ¹H NMR titration. Sensor 4 recognizes F^? and CN^? ions by deprotonation mechanism with visible colour change of the solution in a similar manner to that of 2. However, in contrary to 2 and 4, sensor 3 binds with F^?, CN^?, H₂PO₄ ^?, AcO^? and PhCOO^? ions exploiting hydrogen-bonding interaction with the shifting of absorption band to longer wavelength and subsequent colour change of the solution. Compound 5 recognizes F^? without any visual colour change and its binding is studied by ¹H NMR titration to acquire the important information about the nature of binding between F^? and 5.     

Anion Binding Properties of N-Confused Porphyrins at the Peripheral Nitrogen

Ni(II), Pd(II), and Cu(II) complexes of N-confused porphyrin (NCP) exhibit anion binding properties through a hydrogen bonding interaction at the peripheral NH of confused pyrrole ring. The binding constants of the tetrakis(pentafluorophenyl)-NCP metal complexes (1-M, M= Ni, Pd, Cu) for various halide anions in CH₂C1₂ increase in the order of F^? > Cl^? > Br^? > I^?, respectively. Zwitterionic resonance form of the NCP complexes as well as interactions between halide anions and a pentafluorophenyl group are suggested to be important for efficient anion binding.     

A novel colorimetric and fluorometric anion sensor based on BODIPY-calix[4]pyrrole conjugate

A novel fluorescent anion sensor 1 based on boradiazaindacenes (BODIPY) derivative was synthesized and its absorption and fluorescence properties were investigated in various solvents. 1 exhibited a red shift of absorption spectrum and fluorescence quenching in varying degree in the presence of F^?, AcO^?, H₂PO₄ ^? and Cl^? due to multiple hydrogen bonding interactions between these anions and calix[4]pyrrole receptor. As an anion sensor in the visible region, 1 displayed the similar selectivity and sensitivity toward anions compared to the parent calix[4]pyrrole. However, 1 can be used as an effective dual responsive optical sensor for F^? via chromogenical and fluorogenical signals.     

Reactions of photogenerated fluorine atoms with dopant molecules in solid argon

The products of UV photolysis of ternary Ar?CH₄(CD₄)?F₂ mixtures (1:c:c ₀,c, c ₀=0.001–0.01) at 13–16 K were identified by ESR and FTIR spectroscopy. These products are^?CH₃ (^?CD₃) radicals of typesI andII and molecular CH₃F?HF complexes. The latter were characterized by the IR bands of the stretching C?F (1003 cm^?1) and H?F (3774 cm^?1) vibrations. The ESR spectra of radicalsI are asymmetric. The anisotropy of theg-factor (Δg～10^?3) of radicalI indicates that the structure of the radicals is nonplanar. The ESR spectrum of the typeII radical is identical to that of matrix-isolated^?CH₃ (^?CD₃) radicals with the planar structure (Δg<5·10^?5). Under the experimental conditions, the amount of complexes formed in the photolysis is equal to 0.022·c. When the photolysis is ceased, radicalI disappears after ≈10³ s and radicalII is stabilized. The limiting concentrations of the stabilized^?CH₃ and^?CD₃ radicals are equal to 2·10^?2·c and 2·10^?3·c, respectively. A mechanism of the formation of the products is suggested. It is based on the assumption that both matrix-isolated CH₄ and F₂ and their heterodimers CH₄?F₂ are present in the samples and it takes into account the long-range migration of translationally excited flourine atoms. The CH₃F?HF complexes and radicalsI are generated by the photolysis of the CH₄?F₂ heterodimers. The decay of radicalsI is caused by geminate recombination of proximate F...CH₃ pairs. RadicalsII are formed in the reaction of translationally excited fluorine atoms with isolated CH₄ (CD₄) molecules.     

Structural organization and thermal behavior of the heteropolynuclear complex [Au2{S2CN(CH3)2}4][ZnCl4] and the heterovalent complex ([Au{S2CN(CH3)2}2][AuCl2]) n obtained in the chemisorption system [Zn2{S2CN(CH3)2}4]-Au3+/2 M HCl

Reactions of freshly precipitated binuclear zinc dimethyldithiocarbamate with [AuCl₄]^? anions in 2 M HCl were studied. The heteropolynuclear complex [Au₂{S₂CN(CH₃)₂}₄][ZnCl₄] (I) and the polymeric heterovalent complex ([Au{S₂CN(CH₃)₂}₂][AuCl₂]) _n (II) were preparatively isolated from the chemisorption system [Zn₂{S₂CN(CH₃)₂}₄]-Au³⁺/2 M HCl. The products were characterized by ¹³C MAS NMR data and by X-ray diffraction determination of crystal and molecular structures. The principal structural units of compounds I and II are the tetragonal planar complex cations [Au{S₂CN(CH₃)₂}₂]⁺ (in which the complex-forming ion coordinates two MDtc ligands in the S,S′-bidentate mode) and the anions, namely, the distorted tetrahedral anion [ZnCl₄]^2? in I and the linear [AuCl₂]^? anion in II. The further structural self-organization of complexes at the supramoleular level occurs through relatively weak secondary bonds Au?S and Au?Cl. The chemisorption capacities of zinc dimethyldithiocarbamate calculated from gold(III)-binding reactions are 644.1 and 1288.2 mg of gold per gram of the sorbent. Simultaneous thermal analysis studies of the thermal behavior of I and II were used to elucidate the conditions of gold recovery.     

Naphthyridine-based receptors for flurometric detection of urea and biotin

Naphthyridine-based receptors 1–4 have been designed and synthesized for the recognition of urea in CHCl₃ containing 1% CH₃CN. Receptor 1 also binds biotin and its methyl ester with moderate binding constant values. In comparison, receptor 2 is less efficient in recognising biotin and its methyl ester analogue. Receptor 1 binds urea and biotin with binding constant values of 1.02 × 10⁴ and 1.08 × 10⁴ M^?1, respectively, in CHCl₃ containing 1% CH₃CN and shows significant change in emission of naphthyridine upon complexation. Characterization and sensing properties of the receptors were evaluated by ¹H NMR, UV–vis and fluorescence spectroscopic methods.     

Study on the selectivity of anion receptors by adjusting the distance of two urea fragments and their analytical application

Three anion receptors based on urea: 1 N, N??-bis-(p-nitrophenylaminocarbonyl)-Hydrazine, 2 N, N??-bis-(p-nitrophenylaminocar-bonyl)-ethylenediamine and 3 N, N??-bis-(p-nitrophenylaminocarbonyl)-1, 3-propane-diamine are designed and synthesized. Studies of UV?Cvis spectra presented that 1 was an excellent sensor of F^? and 2 was sensitive to H₂PO₄ ^?. Unfortunately, 3 can not distinguish the anions investigated in this paper. The color changes of the hosts upon the addition of a variety of structurally different anions were also utilized as naked-eye detection which is very convenient. It also revealed significantly that the distance between two recognition sites of receptor had an immediate effect on the selectivity of receptor for anions, which had been confirmed by the ¹H NMR titration and IR.     

Synthesis and structure of palladium complexes [Ph3PhCH2P]+[PdCl3(DMSO)]− · DMSO, [Ph4P]+[PdCl3(DMSO)]−, and [Ph4Sb(DMSO)]+[PdCl3(DMSO)]−

[Ph₃PhCH₂P]⁺[PdCl₃(DMSO)]^? · DMSO (I), [Ph₄P]⁺[PdCl₃(DMSO)]^? (II), and [Ph₄Sb(DMSO)]⁺[PdCl₃(DMSO)]^? (III) complexes have been synthesized via the reaction of palladium chloride with equimolar amounts of triphenylbenzylphosphonium chloride, tetraphenylphosphonium chloride, and tetraphenylstibonium chloride, respectively. According to X-ray diffraction data, the cations of complexes I (CPC = 104.90(8)°–111.61(9)°) and II (CPC = 105.12(10)°–111.46(10)°) have slightly distorted tetrahedral structures with P-C bond lengths of 1.786(2)–1.809(2) and 1.791(2)–1.799(2) Å, respectively. The antimony atom in the [Ph₄Sb(DMSO)]⁺ cation has a trigonal bipyramidal surrounding with the dimethyl sulfoxide (DMSO) oxygen atom in an axial position (Sb...O 2.567(2) Å). The palladium atoms in the square mononuclear anions of complexes I, II, and III are tetracoordinate, and Pd-Cl distances are 2.3101(5)–2.3104(5) Å, 2.2950(7)–2.2038(7) Å, and 2.2986(9)–2.3073(9) Å, respectively. The DMSO ligands are coordinated to the palladium atom through the sulfur atom (Pd-S, 2.2318(5) (I), 2.2383(6) (II), and 2.2410(9) Å (III)).     

Study by fluorescence of calix[4]arenes bearing heterocycles with anions: highly selective detection of iodide

The present work describes a study of complexation efficiency of calix[4]arenes bearing benzoimidazolyl, benzothiazolyl, and benzoxazolyl heterocycles (5–7) towards several anions. The binding ability of calixarene derivatives 5–7 towards selected anions of different molecular geometries such as: F^?, HSO₄ ^?, I^?, N₃ ^?, NO₃ ^?, NO₂ ^?, SCN^?, ClO₄ ^?, Br^?, CN^?, Cl^?, CH₃COO^? CF₃SO₃ ^? in methanol, has been investigated by fluorescence spectroscopic techniques, all anions were used as tetrabutylammonium salts to avoid possible complexation of cationic species by the derivative calix[4]arenes. Fluorescent chemosensor ability of these three calixarene derivatives was highly selective for iodide in contrast with other anions studied. The best chemosensor found, corresponds to compound 7, with an association constant of 2.01 × 10⁴ mol^?1 L and a detection limits of 0.22 ppm for iodide.     

Biaryl-based anion receptors bearing thiourea groups: fluoride anion receptor

The synthesis, characterization and binding studies with anions for biaryl-based anion receptors bearing thiourea groups have been described. The results revealed that receptors (1 and 2) showed good selectivity and binding affinity for F^?, and among them binaphthyl-based receptor (1a) showed the best binding affinity for F^? in comparison to other tested anions (Cl^?, Br^?, I^?, $ {\text{NO}}_{3}^{ - } ,\;{\text{HSO}}_{4}^{ - } , $ AcO^? and $ {\text{H}}_{2} {\text{PO}}_{4}^{ - } $ ). This is probably due to the fact that the moderate rigidity of binaphthyl skeleton in 1a is able to provide the better geometry of two thiourea groups for incorporating F^? into the binding pocket. The higher basicity of F^? also participated in this selectivity.     

Dual colorimetric sensoring bis(indolyl)calix[4]crown-6

Calix-chromophore, bis(indolyl)calix[4]crown-6 (1) in an oxidized form showing selective colorimetric changes for both alkaline earth cations and F⁻ in CH₃CN, has been newly synthesized. It is observed that the binding ability of 1 for the Ca²⁺ binding enhances in the presence of F⁻. Compound 1 can operate three independent combinational NOR logic gates toward metal cations and anions.     

A selective fluorescent and colorimetry competition assay for fluoride ions in DMSO media based on 4-chloro-2,6-bis(hydroxymethyl) phenol

We report here a selective, efficient and very simple receptor which can easily detect F^? in the presence of a wide range of other anions [Cl^?, Br^?, I^?, HSO ₄ ^? , NO ₃ ^? , Acetate (AcO ^?) and Benzoate (BzO ^?)] by use of colorimetric or fluorometric detection. 4-Chloro-2,6-bis(hydroxymethyl) phenol (CBHMP) is a simple and available phenolic receptor having no special chromophoric function. In this colorimetric method, naked-eye detection of F^? with CBHMP is described. Interestingly, fluorometric detection of F^? is also possible by highly selective fluorescent quenching response CBHMP in dimethyl sulfoxide (DMSO) media.     

Reactions of strong bases with vinyl fluoride formation and characterization of 1-fluorovinyl anion and the fluoride-acetylene hydrogen-bonded complex

Vinyl fluoride reacts with strong bases to afford I-fluorovinyl anion (1a) and a fluoride-acetylene cluster (1b). The former ion can be prepared independently, and cleanly, by the fluorodesilylation of 1-(trimethylsilyl) fluoroethylene. Reactions of 1a are reported, and its proton affinity is assigned (387 ± 3 kcal mol^?1). Vinyl fluoride is 22 kcal mol^?1 more acidic than ethylene. This unusually large substituent effect is reproduced by ab initio calculations, and can be accounted for by geometric changes which minimize the electron-electron repulsion in 1a. Computations on 2-fluorovinyl anions (1c and 1d) have also been carried out, and both ions are only slightly less stable than 1a. The cis isomer (1c) has a larger barrier for fluoride elimination and is a reasonable target for preparation.     

Isomeric ion-neutral complexes generated from ionized 2-Methylpropanol and n-Butanol: the effect of the polarity of the neutral partner on complex-mediated reactions

Photoionization was used to characterize the energy dependence of C₃H ₇ ⁺ , C₃H ₆ ⁺ , CH₃OH ₂ ⁺ and CH₂=OH⁺ formation from (CH₃)₂)CHCH₂OH^+? (1) and CH₃CH₂CH₂CH₂OH^+? (2). Decomposition patterns of labeled ions demonstrate that close to threshold these products are primarily formed through [CH ₃ ⁺ CHCH₃ ^?CH₂OH] (bd3) from 1 and through [CH₃CH₂CH₂ ^?CH₂=OH⁺] (9) from 2. The onset energies for forming the above products from 1 are spread over 85 kJ mol^?1, and are all near thermochemical threshold. The corresponding onsets from 2 are in a 19 kJ mol^?1 range, and all except that of CH₂=OH⁺ are well above their thermochemical thresholds. Each decomposition of 3 occurs over a broad energy range (> 214 kJ mol^?1), This demonstrates that ion-permanent dipole complexes can be significant intermediates over a much wider energy range than ion-induced dipole complexes can be. H-exchange between partners in the complexes appears to be much faster than exchange by conventional interconversions of the alcohol molecular ions with their distonic isomers. The onsets for water elimination from 1 and 2 are below the onsets for the complex-mediated processes, demonstrating that the latter are not necessarily the lowest energy decompositions of a given ion when the neutral partner in the complex is polar.     

Synthesis,characterization, and thermal behavior of palladium(II) complexes containing 4-iodopyrazole

The mononuclear pyrazolyl complexes [PdCl₂(HIPz)₂] (1), [PdBr₂(HIPz)₂] (2), [PdI₂(HIPz)₂] (3), [Pd(SCN)₂(HIPz)₂] (4), and [Pd(NHCOIPz)₂] (5) have been prepared. Compound 1 was obtained from the displacement of acetonitrile from [PdCl₂(CH₃CN)₂] precursor by the 4-iodopyrazole (HIPz) ligand, whereas 2–5 were synthesized by substitution of the chlorido in 1 by the respective anionic group. The compounds were characterized by elemental analysis, infrared spectroscopy, and ¹H NMR spectroscopy. The thermal behavior of 1–5 has been studied by TG and DTA. The thermal stability of [PdX₂(HIPz)₂] compounds varies according to the trends X = Cl^? < I^? ? SCN^?< Br^?. No stable intermediates were isolated during the thermal decompositions due to the overlap of the degradation processes. The final products of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Synthesis, spectroscopic characterization and structure-activity relationship of some phosphoramidothioate pesticides

In this work, some phosphoramidothioates (PATs) with the general formula of (CH₃O)₂P(S)X and (CH₃O)(CH₃S)P(O)X, where, X = NH₂ (1 & 6), NH(CH₃) (2 & 7), N(CH₃)₂ (3 & 8), N(Et)₂ (4 & 9), (CH₃CH₂O)₂P(S)NH(CH₃) (5) and (CH₃CH₂O)(CH₃CH₂S)P(O)NH(CH₃) (10), were synthesized and characterized by ³¹P, ³¹P{¹H}, ¹³C and ¹H NMR spectroscopy. The ability of the compounds to inhibit AChE was predicted by PASS software (version 1.193). They were also experimentally evaluated by a modified Ellman??s assay. The structure-activity relationship (SAR) between IC50 and some physico-chemical properties such as lipophilicity (logP), electronic and steric effects of the compounds was studied. The logP values were experimentally determined by the shake-flask (gas chromatography) method. Inhibitory potency for the compounds 1?C10 was 1 (3.38 mM) > 2 (3.97 mM) > 3 (4.75 mM) > 4 (6.00 mM) > 5 (5.51 mM) > 6 (0.07 mM) > 7 (0.23 mM) > 8 (0.39 mM) > and 9 (0.55 mM) > 10 (0.51 mM), respectively. IC₅₀ and logP parameters of the P=O moiety were more than the P=S moiety in PAT analogues.     

anti-syn and anti-anti coordination of the bridging CO 3 2− group in [Cu2(Phen)4(μ-CO3)]B10H10 binuclear complexes: Synthesis, structure, and magnetic properties

A redox reaction that occurs in the [Cu₂B₁₀H₁₀]/Phen system in CH₃CN/DMSO and CH₃CN/DMF in air yields a Cu(II) binuclear complex, [(Phen)₂Cu(CO₃)Cu(Phen)₂]²⁺. The [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 2.5DMSO · 2H₂O (I) and [Cu₂(Phen)₄(μ-CO₃)]B₁₀H₁₀ · 4DMF (II) compounds have been isolated and studied by X-ray crystallography at 150 K and EPR at 295 K. Their magnetic properties have been studied in the range 300–2 K. In the cations of both compounds, the bridging CO ₃ ^2? group is bidentately coordinated to two Cu atoms. The cations in I and II have different spatial orientations of the Cu-O bonds: anti-syn and anti-anti, respectively. Compound I has weak magnetic interactions caused by a short Cu…Cu distance (4.441 Å) in the dimer. No exchange coupling is observed in II.     

Coordination chemistry of bis(2-pyridylimine) ligands with Ag(I): formation of two structurally different coordination polymers and one metallocycle controlled by linker and the solvent system

Reaction of equimolar amounts of AgClO₄ and bis[4-(2-pyridylmethyleneamino)phenyl] methane (L¹) or bis[4-(2-pyridylmethyleneamino)phenyl] ether (L²) in a 1:1 solvent mixture of CH₃CN and CH₂Cl₂ leads to the formation of two infinite coordination polymers of the composition {[Ag(L¹)]ClO₄·CH₃CN}_n (1) and {[Ag(L²)]ClO₄·CH₂Cl₂}_n (2). Whereas 1 represents a homochiral single-stranded helicate the related complex 2 shows a typical zigzag chain arrangement. Both structures are characterized by a distorted tetrahedral coordination environment of the Ag(I) centres each based on a N₄ coordination pattern of two ligand molecules. The resulting strands are connected by a hydrogen bonding network including ClO₄ ^? anions and solvent molecules forming 2-D layers. Additional ?ШC?? and CH?C?? interactions between the aromatic parts of the ligand molecules give a 3-D arrangement of the packing. In contrast, a discrete dinuclear metallocycle, [Ag₂(L²)₂](ClO₄)₂·CH₃OH (3), has been formed by reaction of AgClO₄ with L² when CH₂Cl₂ in the solvent mixture was replaced by CH₃OH. Again each Ag(I) has a distorted tetrahedral geometry and is coordinated to two pyridylimine units of two ligand molecules. Additional weak hydrogen bonds involving perchlorate and solvent molecules as well as edge-to-face and face-to-face ?ШC?? interactions allow a 3-D packing arrangement.     

F− Preference of Polyamide Cryptand to Cl−

The variations in geometry structure, IR spectra, as well as the molecular orbitals upon anion recognition for polyamide cryptand are explored with the hybrid density functional theory. The cavity generated by six amide NH groups shrinks upon F ^? recognition because of the strong hydrogen bonds between the amide protons and F ^? , while the cavity expands upon Cl ^? binding because of the strong electron repulsion between the p electron of Cl ^? and the lone pair electrons of the nitrogen atom of the pyridine moieties. The “electropositive field space” …Cl ^? coupling exists when Cl ^? is recognized. The strong anion binding energy with F ^? indicates that the polyamide cryptand prefers F ^? to Cl ^? .