Reactions of pyridyl donors with halogens and interhalogens: an X-ray diffraction and FT-Raman investigation

Three different N-donors L, namely N-ethyl-N′-3-pyridyl-imidazolidine-4,5-dione-2-thione (1), N,N′-bis(3-pyridylmethyl)-imidazolidine-4,5-dione-2-thione (2), and tetra-2-pyridyl-pyrazine (3), bearing one, two and four pyridyl substituents, respectively, have been reacted with halogens X₂ (X = Br, I) or interhalogens XY (X = I; Y = Cl, Br). CT σ-adducts L · nXY, bearing linear N?XY moieties (L = 3; X = I; Y = Br, I; n = 2), and salts containing the protonated cationic donors H_nLⁿ⁺ (L = 1 − 3; n = 1, 2, 4), counterbalanced by Cl⁻, Br⁻, , , , , I₂Br⁻, , or anions, have been isolated. Among the reactions products, (H1⁺)Cl⁻, (H1⁺)Br⁻, , , and 3 · 2IBr have been characterised by single-crystal X-ray diffraction. The nature of the products has been elucidated based on elemental analysis and FT-Raman spectroscopy supported by MP2 and DFT calculations.     

Colorimetric and ratiometric fluorescence sensing of fluoride ions based on competitive intra- and intermolecular proton transfer

Receptors 1 and 4 show fluoride ion selective changes in their absorbance and emission behaviours amongst F⁻, Cl⁻, Br⁻, I⁻, , CH₃COO⁻, , and anions. Fluoride ion mediated ‘ON-OFF-ON’ switching behaviour of 4 provides opportunities for ratiometric estimation of fluoride ions.     

Quaternary ammonium salt-based chromogenic and fluorescent chemosensors for fluoride ions

Chemosensors 5-7 possessing a quaternary ammonium cation (for electrostatic interactions) and an N-H group(s) (for H-bonding) as recognition sites and an anthracene-9,10-dione as both a chromogenic and fluorescent moiety exhibit absorption and emission changes with fluoride ions only. No significant response to other anions such as Cl⁻, Br⁻, I⁻, , CH₃COO⁻, , and is observed. The dual emission at λ_max 580 nm (free 5/6) and λ_max 510 and 540 nm (5/6 + F⁻) in chemosensors 5 and 6 enables ratiometric analysis of fluoride ions.     

Syntheses and characterization of two new zinc phosphites with 1D chains decorated by Zn-centered complexes

Two inorganic-organic hybrid solids, Zn₂(phen)(HPO₃)₂ (1) and Zn(phen)(HPO₃) (2), have been synthesized under solvothermal conditions in the presence of 1,10-phenanthroline (phen) ligands. Their structures were determined by single-crystal X-ray diffraction and further characterized by FTIR, elemental analysis, powder X-ray diffraction, thermogravimetric analysis and fluorescent spectra. Compound 1 crystallizes in the triclnic system, space group P-1, , , , α=75.609(1)°, β=79.145(2)°, γ=67.157(2)°, , Z=2. Compound 2 is monoclinic, C2/c, , , , β=94.175(4)°, , Z=8. Both structures consist of 1D chains constructed from strictly alternating ZnO₄ and HPO₃ polyhedra through sharing vertices. The chains are further decorated by Zn-centered complex architectures, [Zn(phen)]²⁺ for 1 and [Zn(phen)₂]²⁺ for 2. The 2D and 3D supramolecular arrays for 1 and 2 are stably stacked via strong π-π interactions of the phen groups, respectively.     

One-dimensional chains in uranyl tungstates: Syntheses and structures of A8[(UO2)4(WO4)4(WO5)2] (A=Rb, Cs) and Rb6[(UO2)2O(WO4)4]

Three new uranyl tungstates, A₈[(UO₂)₄(WO₄)₄(WO₅)₂] (A=Rb (1), Cs (2)), and Rb₆[(UO₂)₂O(WO₄)₄] (3), were prepared by high-temperature solid-state reactions and their structures were solved by direct methods on twinned crystals, refined to R₁=0.050, 0.042, and 0.052 for 1, 2, and 3, respectively. Compounds 1 and 2 are isostructural, monoclinic P2₁/n, (1): a=11.100(7), b=13.161(9), , β=90.033(13)°, , Z=8 and (2): , , , β=89.988(2)°, , Z=8. There are four symmetrically independent U⁶⁺ sites that form linear uranyl [O=U=O]²⁺ cations with rather distorted coordination in their equatorial planes. There are six W positions: W(1) and W(2) have square-pyramidal coordination (WO₅), whereas W(3), W(4), W(5), and W(6) are tetrahedrally coordinated. The structures are based upon a novel type of one-dimensional (1D) [(UO₂)₄(WO₄)₄(WO₅)₂]⁴⁻ chains, consisting of WU₄O₂₅ pentamers linked by WO₄ tetrahedra and WO₅ square pyramids. The chains run parallel to the a-axis and are arranged in modulated pseudo-2D-layers parallel to (0 1 0). The A⁺ cations are in the interlayer space between adjacent pseudo-layers and provide a 3D integrity of the structures. Compounds 1 and 2 are the first uranyl tungstates with 2/3 of W atoms in tetrahedral coordination. Such a high concentration of low-coordinated W⁶⁺ cations is probably responsible for the 1D character of the uranyl tungstate units. The compound 3 is triclinic, P1¯ a=10.188(2), b=13.110(2), , α=97.853(3), β=96.573(3), γ=103.894(3)°, , Z=4. There are four U positions in the structure with a typical coordination of a pentagonal bipyramid that contain uranyl ions, UO₂²⁺, as apical axes. Among eight W sites, the W(1), W(2), W(3), W(4), W(5), and W(6) atoms are tetrahedrally coordinated, whereas the W(7) and W(8) cations have distorted fivefold coordination. The structure contains chains of composition [(UO₂)₂O(WO₄)₄]⁶⁻ composed of UO₇ pentagonal bipyramids and W polyhedra. The chains involve dimers of UO₇ pentagonal bipyramids that share common O atoms. The dimers are linked into chains by sharing corners with WO₄ tetrahedra. The chains are parallel to [−101] and are arranged in layers that are parallel to (1 1 1). The Rb⁺ cations provide linkage of the chains into a 3D structure. The compound 1 has many structural and chemical similarities to its molybdate analog, Rb₆[(UO₂)₂O(MoO₄)₄]. However, the compounds are not isostructural. Due to the tendency of the W⁶⁺ cations to have higher-than-fourfold coordination, part of the W sites adopt distorted fivefold coordination, whereas all Mo atoms in the Mo compound are tetrahedrally coordinated. Distribution of the WO₅ configurations along the chain extension does not conform to its ‘typical’ periodicity. As a result, both the chain identity period and the unit-cell volume are doubled in comparison to the Mo analog, which leads to a new structure type.     

The synthesis and crystal structure of vanadium complexes: [VO2(phen)2]·6H2O and [2,2′-(bipy)2VO2](H2BO3)·3H2O

The organic-inorganic hybrid materials vanadium oxide [V^IVO₂(phen)₂]·6H₂O (1) and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O (2) have been conventional and hydrothermal synthesized and characterized by single crystal X-ray diffraction, elemental analyses, respectively. Although the method and the ligand had been used in the syntheses of the compounds (1) and (2) are different, they almost possess similar structure. They all exhibit the distorted octahedral [VO₂N₄] unit with organonitrogen donors of the phen and 2,2′-bipy ligands, respectively, which coordinated directly to the vanadium oxide framework. And they are both non-mixed-valence complexes. But the compound (1) is isolated, and the compound (2) consists of a cation of [(2,2′-bipy)₂V^VO₂]⁺ and an anion of (H₂BO₃)⁻. So the valence of vanadium of (1) and (2) are tetravalence and pentavalence, respectively. Meanwhile it is noteworthy that π-π stacking interaction between adjacent phen and 2,2′-bipy groups in compounds 1 and 2 also play a significant role in stabilization of the structure. Thus, the structure of [V^IVO₂(phen)₂]·6H₂O and [(2,2′-bipy)₂V^VO₂](H₂BO₃)·3H₂O are both further extended into interesting three-dimensional supramolecular. Crystal data: (1) Triclinic, a=8.481(4), b=12.097(5), and α=66.32(2), β=82.97(3), and γ=82.59(4)°, Z=2, R₁=0.0685, wR₂=0.1522. (2) Triclinic, a=6.643(13), b=11.794(2), and α=101.39(3), β=101.59(3), and γ=97.15(3)°, Z=2, R₁=0.0736, wR₂=0.1998.     

Tetramidocavitand: strong anion receptor by well-organized four -(CO)N-H?X interactions

Resorcin[4]arene-based tetramidocavitands containing four secondary amide groups on their upper rim showed strong (R = methyl or ethyl) binding properties. The caviplex formation through hydrogen bonds of -(CO)N-H?X⁻ was supported by ¹H NMR and crystal structure analyses. In a mixture of C₂D₂Cl₄/DMSO/D₂O = 5:15:2 at 25 °C, the thermodynamic parameters for caviplex @1, ΔG (kcal mol⁻¹), ΔH (kcal mol⁻¹), and ΔS (cal K⁻¹ mol⁻¹), are −3.7, −8.6, and −16.7, respectively.     

Isothiouronium-based amphiphilic gold nanoparticles with a colorimetric response to hydrophobic anions in water: a new strategy for fluoride ion detection in the presence of a phenylboronic acid

Gold nanoparticles modified with isothiouronium-derived amphiphile units 1 were prepared by the reduction of with NaBH₄ in the presence of bis(5-(N-(2-(2-methoxyethoxy)ethyl)-N-methyl-S-isothiouronio)pentyl) disulfide 2. The obtained nanoparticles 1 showed a selective coloration for hydrophobic anions in water, possibly due to an anion exchange and subsequent aggregation. On the basis of this observation, the detection of F⁻ in water has been achieved using 3-nitrophenylboronic acid as a mediator at pH 5.5, thereby providing a new strategy for the design of a F⁻ sensory system.     

A new fluorescent chemosensor for F based on inhibition of excited-state intramolecular proton transfer

New fluorescent chemosensor 1 with two amidoanthraquinone groups (1-AAQs) at the lower rim of p-tert-butylcalix[4]arene has been synthesized. The significant changes of absorption and fluorescence bands show that chemosensor 1 is selective toward fluoride ion (F⁻) over other anions such as Cl⁻, Br⁻, I⁻, CH₃COO⁻, , , and OH⁻. The ESIPT process of 1 is inhibited by the fluoride-induced H-bonding followed by deprotonation of NH of the 1-AAQ.     

A novel calix[4]arene fluorescent receptor for selective recognition of acetate anion

A novel bridged fluorescent calix[4]arene with 1,8-diaminoanthracene and glycine at the upper rim has been prepared, which exhibited selective recognition towards AcO⁻ over other anions such as F⁻, Cl⁻, Br⁻, , , I⁻ and by fluorescence spectroscopy and ¹H NMR method.     

Palladium complexes with meso-bioxazoline ligands for alternating styrene/CO copolymerisation: Counterion effect

Two sets of mono- and dicationic palladium complexes (8) and (10), having and as counterions, were synthesised. The interionic structure of the methyl-acetonitrile complexes [Pd((R,S)-Bn-Box)(CH₃)(NCCH₃)](X) (8) in solution, was investigated by pulsed-gradient spin-echo (PGSE) diffusion measurements and (¹H, ¹⁹F)-HOESY NMR spectroscopy. A high degree of ion-pairing was found in each complex. The HOESY spectra showed that the and anions take up selective positions, on the side of the complex remote from the benzyl groups, but close to the acetonitrile ligand, while the triflate is, partially, occupying a pseudo fifth coordination position on the side of the cation remote from the two benzyl-groups. The complexes 8 and 10 were used as catalyst precursors for the copolymerisation of styrene with carbon monoxide, producing syndiotactic copolymers, with the exception of complex 10a, that led to isotactic copolymers.     

The coordination chemistry and reactivity of amino-dithiaphospholanes with rhodium, iridium, and ruthenium

Novel amino-dithiaphospholane complexes of ruthenium, iridium, and rhodium were synthesized, and their properties were studied. Reaction of the new amino-dithiaphospholane (RS)₂ (R = binaphthyl, R′ = CH₂Ph, (rac)-4) with [RuCl₂(p-cymene)]₂ afforded [RuCl₂(p-cymene)((rac)-4)] in 67% isolated yield. Similarly, the new amino-dithiaphospholanes (RS)₂ (R = cyclohexyl, (rac)-7) and (RS)₂ (R = phenyl, 9) gave upon reaction with [RhCl(CO)₂]₂ and [IrCp^∗Cl₂]₂ the novel complexes [RhCl(CO)(L)₂] and [IrCp^∗Cl₂(L)] (L = (rac)-7, 9) in 61-96% yields. The ruthenium complex is catalytically active for the etherification of propargylic alcohols with methanol and ethanol (8-48 h, 90 °C, 40-85% isolated yields).     

Anion-induced ring-opening of fluorescein spirolactam: fluorescent OFF-ON

N-(2,7-Dichlorofluorescein)lactam-N′-phenylthiourea (L) was developed as a colorimetric and fluorescent chemosensor for anions such as AcO⁻, F⁻ and . The addition of AcO⁻ anion to the solution of L in CH₃CN results in a distinct fluorescence “ON” observation as well as color change (from colorless to pink). The H-bonding interaction between AcO⁻ anion and thiourea moiety of L induced the ring-opening of the spirolactam of fluorescein moiety, which gave rise to the dual chromo- and fluorogenic changes.