Dihydrogen Phosphate Anions Research Articles

Comparison of the crystal structures of the JAK1/2 inhibitor ruxolitinib and its hydrate and phosphate.

Ruxolitinib {RUX; systematic name: (3R)-3-cyclopentyl-3-[4-(7H-pyrrolo[2,3-d]pyrimidin-4-yl)-1H-pyrazol-1-yl]propanenitrile, C17H18N6} is an orally bioavailable JAK1/2 inhibitor approved for treating intermediate- or high-risk myelofibrosis (MF) and high-risk polycythemia vera (PV). Recent patents claim that RUX can exist in many different forms, information for which is important for the clinical utilization of RUX, especially for the formulation and bioavailability of the drug. But there has been no detailed study on its forms so far. Herein crystals of RUX and its dihydrate (RUX-2H; C17H18N6·2H2O) and phosphate (RUX-P; systematic name: 4-{1-[(1R)-2-cyano-1-cyclopentylethyl]-1H-pyrazol-4-yl}-7H-pyrrolo[2,3-d]pyrimidin-3-ium dihydrogen phosphate, C17H19N6+·H2PO4-) were prepared successfully and their structures studied in detail for the first time. Our study shows that the three crystals of RUX differ in the orientation of the pyrimidine ring relative to the pyrazole ring of the RUX molecule, and in their hydrogen-bond interactions. The water molecules in RUX-2H and the dihydrogen phosphate anion in RUX-P enrich the hydrogen-bond networks in these forms. The expected proton transfer occurs in RUX phosphate and the protonated N atom is engaged in a charge-assisted hydrogen bond with the counter-anion. Hydrogen-bonding interactions dominate in the crystal packing of the three forms. The detailed conformations and packing of the three forms were compared through the calculation of both Hirshfeld surfaces and fingerprint plots.

Anion-Binding Properties of Short Linear Homopeptides.

A comprehensive thermodynamic and structural study of the complexation affinities of tetra (L1), penta (L2), and hexaphenylalanine (L3) linear peptides towards several inorganic anions in acetonitrile (MeCN) and N,N-dimethylformamide (DMF) was carried out. The influence of the chain length on the complexation thermodynamics and structural changes upon anion binding are particularly addressed here. The complexation processes were characterized by means of spectrofluorimetric, 1H NMR, microcalorimetric, and circular dichroism spectroscopy titrations. The results indicate that all three peptides formed complexes of 1:1 stoichiometry with chloride, bromide, hydrogen sulfate, dihydrogen phosphate (DHP), and nitrate anions in acetonitrile and DMF. In the case of hydrogen sulfate and DHP, anion complexes of higher stoichiometries were observed as well, namely those with 1:2 and 2:1 (peptide:anion) complexes. Anion-induced peptide backbone structural changes were studied by molecular dynamic simulations. The anions interacted with backbone amide protons and one of the N-terminal amine protons through hydrogen bonding. Due to the anion binding, the main chain of the studied peptides changed its conformation from elongated to quasi-cyclic in all 1:1 complexes. The accomplishment of such a conformation is especially important for cyclopeptide synthesis in the head-to-tail macrocyclization step, since it is most suitable for ring closure. In addition, the studied peptides can act as versatile ionophores, facilitating transmembrane anion transport.

Modulating fluorescent sensing of the pyrene-based ion pair receptor by docking on graphene quantum dots

We successfully synthesized squaramide-based ion pair receptor 3, possessing a cation binding domain linked to the receptor scaffold so as act as an electron-withdrawing group and enhance anion binding. This compound was able to efficiently and cooperatively bind anions in the presence of sodium cations. Using reference compounds 1 and 2, we demonstrated that the presence of a carbonyl group on the aromatic ring significantly enhances the efficiency of anion binding. The incorporation of this group in the structure of receptor 3, combined with other strongly electron-withdrawing groups located on another aryl subunit, enabled the receptor to bind salts even in the presence of water. Furthermore, the capacity for modular synthesis of diarylsquaramides allowed to obtain sensor 4, which features a pyrene moiety directly attached to the anion-binding domain, selectively sensing dihydrogen phosphate anions. Besides the signaling feature, the presence of pyrene rings facilitated the docking of sensor 4 onto the surface of graphene quantum dots, resulting in a conjugate with improved fluorescent properties.

Intensified electrochemiluminescence and photoluminescence via supramolecular anion recognition interactions.

Herein, intensified electrochemiluminescence (ECL) and photoluminescence (PL) via supramolecular anion recognition interactions are demonstrated. A bisindolylpyrrole derivative with a structure containing two indole groups and 2-hexyl-pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione, BIPPD, was designed and synthesized de novo to induce the enhanced ECL and PL emission based on hydrogen bonding interactions with the dihydrogen phosphate anion. Remarkably, the ECL quantum efficiency and PL quantum yield were discovered to increase up to 5.5-fold and 1.5-fold, respectively, via this anion coordination. Dopant PF6 - was found not to form hydrogen bonds, while HSO4 - doping does slightly with the receptor molecule. There was no enhancement in either ECL or PL in both scenarios, revealing great recognition selectivity of the synthesized BIPPD. Mechanistic studies via 1H NMR, ECL, and PL spectra illustrated that the ECL processes varied in the presence and absence of H2PO4 - doping, thus leading to the understanding of enhanced efficiency. The bisindolylpyrrole derivative will find applications in supramolecular and analytical chemistry via controlled hydrogen bonding interactions.

Ionic Copolymers Including Iodide and Dihydrogen Phosphate Anions for Increased Adsorption and Anticorrosion on Copper in Sulfuric Acid

Ionic Copolymers Including Iodide and Dihydrogen Phosphate Anions for Increased Adsorption and Anticorrosion on Copper in Sulfuric Acid

Selective turn-on sensing of adenosine diphosphate and phosphate anions by ruthenium (II) polypyridine anchored p-tert-butylcalix[4]arene platform

BackgroundNucleoside polyphosphate (NPP) anions are important for enzymatic activity and should be monitored by scientists in industry and medicine. By elucidating enzyme kinetics and processes, it aids in the discovery of effective inhibitors and activators. Nucleoside polyphosphate (NPP) anions are used by kinases, GTPases, and glycosyltransferases (GTs). Phosphorylation of certain amino acid residues (Ser, Thr, and Tyr) on proteins requires the breakdown of ATP by protein kinases, which produces ADP. Protein kinases, breakdown of ATP, and NPP are the focus of oncology drug development because the aberrant control of kinase activity is a common cause of cancer. ResultsHowever, a discriminative turn-on fluorescent property is exhibited by non-fluorescent p-tertbutylcalix[4]arene modified 1,2,3-triazole containing bis-ruthenium polypyridyl complex (RL) upon the addition of phosphate anions such as (dihydrogen pyrophosphate (H2P2O72−) and dihydrogen phosphate (H2PO4−)) in CH3CN solvent and Adenosine Diphosphate (ADP) in CH3CN/HEPES (pH = 7.4) buffer (9/1, v/v). The probe RL shows a better-recognizing ability with pyrophosphate anion (H2P2O72−) than dihydrogen phosphate anion (H2PO4−). With H2P2O72− and H2PO4− anions, the RL detection limit was calculated to be as low as 83 nM and 198 nM, respectively. SignificanceThe calix[4]arene macrocycle's excellent size and binding cone conformation make it a good host–guest interface for the pyrophosphate anion and ADP. The bis-ruthenium polypyridyl complex's connection to the p-tertbutyl calix[4]arene moiety creates the ADP selectivity turn-on sensor. When moving from mono-nuclear to bi-nuclear ruthenium complex anchored on p-tertbutyl calix[4]arene, the probe can differentiate ADP, ATP, and AMP. Furthermore, this platform is a great resource for creating devices to simultaneously assess phosphate anions in environmental samples.

Redox-gated recognition of dihydrogen phosphate using a ferrocene-tethered non-symmetric aryl-triazole pentad

ABSTRACT Anions play many roles in our environment. Consequently, the development of synthetic receptors capable of targeted anion binding is of ongoing importance. While many such receptors are known, simplified designs and measurement approaches are always beneficial. Herein, we report the synthesis of a non-symmetric aryl-triazole pentad receptor appended with a single ferrocene, its electrochemistry, and the selective binding to dihydrogen phosphate (H2PO4 –) anions of its oxidised form over various environmentally prevalent anions (HSO4 –, Cl–, NO3 –). The receptor was constructed using a modular architecture with simple installation of a ferrocene unit using click chemistry. Electrochemical analysis on the receptor revealed that addition of H2PO4 – anion led to a shift in the redox peaks of the receptor (FcP) towards more negative potentials, indicating higher anion affinity was achieved after the ferrocene was oxidised to its cationic form (FcP + ). This work verifies prior studies on the efficacy of cationic charge in simpler receptor design for the creation of functional host-guest systems.

Selective Separation of Singly Charged Chloride and Dihydrogen Phosphate Anions by Electrobaromembrane Method with Nanoporous Membranes.

The entrance of even a small amount of phosphorus compounds into natural waters leads to global problems that require the use of modern purification technologies. This paper presents the results of testing a hybrid electrobaromembrane (EBM) method for the selective separation of Cl- (always present in phosphorus-containing waters) and H2PO4- anions. Separated ions of the same charge sign move in an electric field through the pores of a nanoporous membrane to the corresponding electrode, while a commensurate counter-convective flow in the pores is created by a pressure drop across the membrane. It has been shown that EBM technology provides high fluxes of ions being separated across the membrane as well as a high selectivity coefficient compared to other membrane methods. During the processing of solution containing 0.05 M NaCl and 0.05 M NaH2PO4, the flux of phosphates through a track-etched membrane can reach 0.29 mol/(m2×h). Another possibility for separation is the EBM extraction of chlorides from the solution. Its flux can reach 0.40 mol/(m2×h) through the track-etched membrane and 0.33 mol/(m2×h) through a porous aluminum membrane. The separation efficiency can be very high by using both the porous anodic alumina membrane with positive fixed charges and the track-etched membrane with negative fixed charges due to the possibility of directing the fluxes of separated ions in opposite sides.

On the structures of free-base lepidine and some mineral acid salts

The crystal and molecular structures of free-base lepidine (4-methylquinoline, 1) and the mineral acid salts lepidinium chloride (2), nitrate (3) and dihydrogen phosphate (4) are reported. Compound 1 was studied by differential scanning calorimetry and in situ capillary cryocrystallography. In the crystal structures, the molecules of free-base lepidine in 1 and the lepidinium cations in 2–4 are face-to-face π⋅⋅⋅π-stacked. The quinoline nitrogen atom is not involved in directional intermolecular interactions such as weak hydrogen bonds in 1. In the salts 2–4, proton transfer to the quinoline nitrogen atom and N−H⋅⋅⋅Cl (in 2) and N−H⋅⋅⋅O (in 3 and 4) hydrogen bonding is observed. Hirshfeld surface analysis reveals that lepidinium salts 2 and 3 form hydrogen-bonded dimers in the crystal and confirms that the packing of 4 is dominated by hydrogen-bonded dihydrogen phosphate anion chains.

Improved renaturation process of aggregated recombinant proteins through the design of hydrated ionic liquids

Escherichia coli is the most commonly used host for recombinant protein expression. However, since inactive aggregation is obtained at a high rate and the renaturation rate is still low, the improvement of the treatment of aggregated recombinant proteins is a critical issue. This study aimed to evaluate the use of hydrated ionic liquids (ILs) to directly dissolve aggregated recombinant proteins and induce refolding. Selection of component ions and suitable water content resulted in a considerable improvement in the dissolution of the aggregated protein, followed by refolding behaviour. Ammonium or phosphonium cations with butyl groups coupled with dihydrogen phosphate anions were identified as appropriate ion pairs, showing high solubility and contributing to refolding. The column method showed great potential in the transition of dissolved and refolded proteins in hydrated ILs into the buffer solution, achieving both IL removal and protein purification. The successfully recovered activity levels of aggregated proteins indicate that this method is a promising approach for the development of novel treatments for aggregated recombinant proteins.

Anion binding and transport with meso-alkyl substituted two-armed calix[4]pyrroles bearing urea and hydroxyl groups.

Calix[4]pyrroles bearing hydroxyl (1) or urea (3) groups attached to the meso-positions with propyl linkers were synthesized as cis- and trans-isomers. The anion binding properties of cis-1 and cis-3 were screened with ion-mobility mass spectrometry, where cis-1 formed complexes with Cl-, Br- and H2PO4-, whereas cis-3 formed complexes with most of the investigated anions, including Cl-, Br-, I-, NO3-, ClO4-, OTf-, SCN- and PF6-. The structures of the chloride complexes were further elucidated with density functional theory calculations and a crystal structure obtained for cis-1. In solution, chloride and dihydrogenphosphate anion binding with cis-1 and cis-3 were compared using 1H NMR titrations. To assess the suitability of two-armed calix[4]pyrroles as anion transporters, chloride transport studies of cis-1, cis-3 and trans-3 were performed using large unilamellar vesicles. The results revealed that cis-3 had the highest activity among the investigated calix[4]pyrroles, which was related to the improved affinity and isolation of chloride inside the binding cavity of cis-3 in comparison to cis-1. The results indicate that appending calix[4]pyrroles with two hydrogen bonding arms is a feasible strategy to obtain anion transporters and receptors with high anion affinity.

Effect of polar/non-polar facets on the transformation of nanoscale ZnO in simulated sweat and potential impacts on the antibacterial activity

The use of nanoscale zinc oxide (n-ZnO) in the personal care products would cause interactions between n-ZnO and human sweat. Facet engineering has been applied to n-ZnO to improve its activity. Nevertheless, it is not clear whether the exposed facet would affect transformation of n-ZnO in sweat. Herein, we prepared ZnO nanoneedles with the dominant (1010) non-polar facet (i.e., ZnO-1010) and ZnO nanoflakes with the dominant (0001) polar facet (i.e., ZnO-0001), respectively. We found that n-ZnO can undergo chemical transformation in the simulated sweat within 168 h or 24 h, transforming into amorphous materials and Zn3(PO4)20.4 H2O and/or Na(ZnPO4)·H2O. Given the rate constant (e.g., 0.093 h−1 for ZnO-0001 vs. 0.033 h−1 for ZnO-1010) of ZnO depletion and components of the precipitate from the simulated sweat, nevertheless, the transformation is highly dependent on the dominant exposed facet of n-ZnO. The ZnO-0001 relative to ZnO-1010 would likely undergo chemical transformation, demonstrating that the (0001) polar facet compared to (1010) non-polar facet had a superior activity to the dihydrogen phosphate anions in the simulated sweat, which is supported by density functional theory calculations. The chemical transformation can affect the antibacterial activity of n-ZnO to E. coli, moderating the toxicity due to a great decrease in the concentration of the dissolved zinc. In total, our findings provided insights into the facet-dependent transformation for n-ZnO in the simulated sweat, improving our understanding of potential risk of n-ZnO.

Copper oxides activate peroxymonosulfate for degradation of methylene blue via radical and nonradical pathways: surface structure and mechanism.

A one-step hydrothermal method for preparation of copper oxides with different valences using ascorbic acid as a reducing reagent was developed for environmental remediation. The results suggested that the notable degradation performance of CuO0 may be attributable to the abundant active sites, such as Cu or Cu-O, and was not significantly related to the Cu valence state. In contrast to direct degradation of pollutants by traditional superoxide radicals (O2•-), O2•- played an important role in the reduction of high-valence Cu ions (Cu(III)). In addition, a series of radical quenching, electron paramagnetic resonance (EPR), and electrochemical experiments validated the existence of direct electron transfer between methylene blue (MB) and PMS mediated by CuO0 and surface-bound radicals. The results suggested that the CuO0/PMS system may be less susceptible to diverse ions and natural organic matter other than dihydrogen phosphate anions. The mechanism of MB degradation under alkaline conditions was different from that under acidic conditions in that it was not reliant on radicals or charge transfer but direct oxidation by PMS. This study provides new insights into the heterogeneous processes involved in PMS activation by the copper oxides. Furthermore, this paper devotes to providing theoretical basis on pollutant removal via PMS activated by copper oxides and developing low-cost and high-efficiency catalysts.

Calix[4]pyrrole-Based Molecular Capsule: Dihydrogen Phosphate-Promoted 1:2 Fluoride Anion Complexation.

A molecular capsule (1) consisting of two calix[4]pyrroles connected via ethylene diamide linkers has been prepared as an anion receptor. 1H NMR spectroscopic studies carried out in CD2Cl2 revealed that receptor 1 recognizes a variety of anions with different binding modes and stoichiometries. For instance, receptor 1 binds fluoride and acetate with 1:2 receptor/anion stoichiometry and other test anions with 1:1 stoichiometry in solution when their respective tetrabutylammonium (TBA+) salts were used. In contrast, with tetraethylammnium (TEA+) salts, receptor 1 forms 1:2 complexes with chloride and bromide in addition to fluoride, overcoming expected Columbic repulsions between the anions co-bound in close proximity. Receptor 1 is also able to bind oxoanions, such as oxalate (C2O42-), dihydrogen phosphate (H2PO4-), sulfate (SO42-), and hydrogen pyrophosphate (HP2O73-), in the form of 1:1 complexes as the result of presumed cooperation between the two calix[4]pyrrole subunits. The selectivity of receptor 1 for fluoride versus dihydrogen phosphate varies depending on their relative concentrations. For instance, in the presence of less than 1.0 equiv of an equimolar mixture of fluoride and dihydrogen phosphate, receptor 1 shows high selectivity for dihydrogen phosphate. In contrast, in the presence of ≥2.0 anion equiv, receptor 1 binds fluoride preferentially, forming a 1:2 complex. Moreover, when treated with F-, the preformed 1:1 H2PO4- complex of receptor 1 is converted to the corresponding 1:2 receptor/fluoride complex with the release of the prebound dihydrogen phosphate anion. As inferred from gas-phase computations, this seemingly counterintuitive behavior is rationalized in terms of the precomplexed dihydrogen phosphate serving to reduce the reorganization energy required to bind two fluoride anions. The presence of a water molecule in addition to the bound fluoride anions may also favor the formation of the 1:2 F- complex. The present study provides a new approach for fine-tuning the binding selectivity of polytopic anion receptors.

Highly Emissive Quasi-2D Perovskites Enabled by a Multifunctional Molecule for Bright Light-Emitting Diodes.

Quasi-two-dimensional (quasi-2D) perovskite has exhibited great potential to be an ideal luminescent material for perovskite light-emitting diodes (PeLEDs). However, the low-order phases (especially n = 1 phase) and the inevitable defects result in massive nonradiative recombination and poor emission efficiency. Herein, a multifunctional molecule of tetrabutylammonium dihydrogen phosphate (TDP) is introduced to simultaneously suppress the low-n phase, passivate the defects, and increase the exciton binding energy of the quasi-2D perovskite for massive radiative recombination and thus high emission efficiency. The multifunctional roles of TDP are realized by the synergistic effects of tetrabutylammonium cation and dihydrogen phosphate anion, both of which show strong interaction with the lead bromide octahedron of the perovskite. As a result, the TDP-incorporated perovskite films show a great enhancement of the emission efficiency with a remarkable increase in photoluminescence quantum yield (PLQY) from 34.6 to 96.9% at the wavelength of 522 nm. The strengthened radiative recombination promotes efficient emission efficiency with over 2.5-fold improvement in external quantum efficiency (EQE) and current efficiency (CE) from 3.27% and 10.83 cd A-1 to 9.25% and 28.35 cd A-1, respectively, as well as high brightness with over 37% enhancement from 12713 to 17536 cd m-2. Consequently, this work contributes to an efficient approach to employ a multifunctional molecule for highly emissive quasi-2D perovskites and enhanced quasi-2D PeLED performances.

Supramolecular Synthon Promiscuity in Phosphoric Acid-Dihydrogen Phosphate Ionic Cocrystals.

Approximately 80% of active pharmaceutical ingredients (APIs) studied as lead candidates in drug development exhibit low aqueous solubility, which typically results in such APIs being poorly absorbed and exhibiting low bioavailability. Salts of ionizable APIs and, more recently, pharmaceutical cocrystals can address low solubility and other relevant physicochemical properties. Pharmaceutical cocrystals are amenable to design through crystal engineering because supramolecular synthons, especially those sustained by hydrogen bonds, can be anticipated through computational modeling or Cambridge Structural Database (CSD) mining. In this contribution, we report a combined experimental and CSD study on a class of cocrystals that, although present in approved drug substances, remains understudied from a crystal engineering perspective: ionic cocrystals composed of dihydrogen phosphate (DHP) salts and phosphoric acid (PA). Ten novel DHP:PA ionic cocrystals were prepared from nine organic bases (4,4′-bipyridine, 5-aminoquinoline, 4,4′-azopyridine, 1,4-diazabicyclo[2.2.2]octane, piperazine, 1,2-bis(4-pyridyl)ethane, 1,2-bis(4-pyridyl)xylene, 1,2-di(4-pyridyl)-1,2-ethanediol, and isoquinoline-5-carboxylic acid) and one anticonvulsant API, lamotrigine. From the resulting crystal structures and a CSD search of previously reported DHP:PA ionic cocrystals, 46 distinct hydrogen bonding motifs (HBMs) have been identified between DHP anions, PA molecules, and, in some cases, water molecules. Our results indicate that although DHP:PA ionic cocrystals are a challenge from a crystal engineering perspective, they are formed reliably and, given that phosphoric acid is a pharmaceutically acceptable coformer, this makes them relevant to pharmaceutical science.

Dihydrogen phosphate anion boosts the detection of sugars in electrospray ionization mass spectrometry: A combined experimental and computational investigation.

Sugars are key molecules of life but challenging to detect via electrospray ionization mass spectrometry (ESI-MS). Unfortunately, sugars are challenging analytes for mass spectrometric methods due to their high gas-phase deprotonation energies and low gas-phase proton affinities which make them difficult to ionize in high abundance for MS detection. Hydrogen-bond interactions in H2 PO4 - -saccharide anionic systems were studied both experimentally (via electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry, ESI-FT-ICR-MS) and computationally by several sophisticated density-functional theoretical methods (DFT and DFT-D3). The H2 PO4 - dopant boosts the detection of sugars up to 51-times in the case of sucrose and up to 263-times for glucose (at 0.1 ppm concentration level). H2 PO4 - binds toward sugar molecules with noticeably more hydrogen bonds than the established dopant chloride Cl- does, with increasing binding energies in the order: Monosaccharides < Trisaccharides < Disaccharides. Analysis of a complex oak plant sample revealed that NH4 H2 PO4 specifically labeled a diverse set of sugar-type plant metabolites in the form of [M + H2 PO4 ]- complexes. We reveal the mechanism of interaction of H2 PO4 - with different sugars and glycosylated organic compounds, which significantly enhances their ionization in mass spectrometry. A computational and experimental investigation is presented. A strong correlation between the MS signal intensities of detected [M + H2 PO4 ]- anions of different saccharides and their calculated dissociation enthalpies was revealed. Thus, the variation in MS signal intensities can be very well described to a large extent by the variation in calculated saccharide affinities toward the H2 PO4 - dopant anion, showing that DFT-D3 can very well describe experimental FT-ICR-MS observations.

Phase transitions and ionic conductivity of ionic plastic crystals based on pyrrolidinium cations and dihydrogen phosphate anion

Ionic plastic crystals (IPCs) have been studied as solid-state proton conductors due to their properties such as non-volatility, plasticity, and high ionic conductivity. In order to further improve their proton transport property, understanding the relationship between the ion structure and the properties of IPCs is needed. For this purpose, five pyrrolidinium salts with dihydrogen phosphate anion ([DHP] − ) were synthesized. 1-Ethyl-1-methylpyrrolidinium ([C 1,2 pyr] + ) cation and 1-(2-hydroxyethyl)-1-methylpyrrolidinium ([C 1,2OH pyr] + ) cation exhibited one or more solid-solid phase transitions in DSC traces. The 1 H and 31 P solid state NMR results indicated that the component ions in [C 1,2 pyr][DHP] exhibited rotational mobility in Phase I. [C 1,2 pyr][DHP] and [C 1,2OH pyr][DHP] exhibited higher ionic conductivity values than the other pyrrolidinium salts after the addition of H 3 PO 4 , and their ionic conductivity was over 10 −3 S cm −1 at 120 °C. Thus, rotational mobility and the hydroxyl group on the pyrrolidinium cation will contribute to proton transport in the solid-state phases. • Five pyrrolidinium salts with dihydrogen phosphate anion were synthesized. • One or more solid-solid phase transitions were observed for some pyrrolidinium salts. • Ionic conductivity exhibited a large increase at the phase transition temperature. • Plastic crystalline behavior was effective in achieving high ionic conductivity.

Chromogenic detection of fluoride, dihydrogen phosphate, and arsenite anions based on 2,4-dinitrophenyl hydrazine receptors: spectral and electrochemical study

ABSTRACT The colorimetric recognition of biologically relevant fluoride (F−), acetate (AcO−), and dihydrogen phosphate (H2PO4 −) ions, and poisonous arsenite (AsO2 −) ions, was devised and new receptors for these anions synthesised via the Schiff base condensation procedure. UV–visible titration, fluorescence titration, 1H-NMR titration, and cyclic voltammetry were used to explore the interactions of receptors R1–R3 with anions and possible detection mechanisms. The synthesised probes could sense inorganic fluoride, acetate, dihydrogen phosphate, and arsenite in the organo–aqueous medium (H2O/ Dimethylsulphoxide, 1: 9, v/v) and displayed a change in colour detectable to the naked eye. Out of the three synthesised receptors, receptor R1 showed better sensing ability of fluoride, acetate, dihydrogen phosphate, and arsenite ions in the organo–aqueous medium with a lower detection limit of 0.1 ppm, 0.171 ppm, 0.194 ppm, and 0.144 ppm, respectively. All three receptors formed complexes with the anions through H-bonding interaction followed by deprotonation of the NH proton.

Crystal structure, chemical bonds nature and thermodynamic functions for the new ionic liquid pyridinium bis(dihydrogen phosphate)

A crystal structure (confirmed via single X-ray diffraction analysis) of the new ionic liquid pyridinium bis(dihydrogen phosphate) ([H–Pyr]+([H2PO4]–)2) is presented in this work for the first time. Optimized molecular geometry of [H–Pyr]+([H2PO4]–)2 is determined by means of density functional theory (DFT) at B3LYP/6-311++G(2d,2p) level and a good correlation between experimental and calculated structural parameters (bond lengths and angles) is revealed. Different types of intramolecular hydrogen bonds between [H–Pyr]+ and [H2PO4]– fragments are found to stabilize the title compound structure. Moreover, a hydrogen bond between the dihydrogen phosphate anions is also detected. The Quantum theory of atoms in molecules and natural bond orbital analysis have been performed to elucidate the chemical bonds nature and electron density delocalization, respectively in [H–Pyr]+([H2PO4]–)2. The standard thermodynamic functions specific heat capacity (Cp,m∘), enthalpy and entropy for the title compound are calculated. Polynomial equations for solid and liquid phases describe the temperature dependence of Cp,m∘for [H–Pyr]+([H2PO4]–)2 sample. A relationship between the internal hydrogen bonding, chemical bonds nature and the standard thermodynamic functions is presented.