酸性黄25插层水滑石薄膜的制备及其性能研究

采用原位生长法在铝片基底表面制备了ZnAl-NO3-LDHs水滑石薄膜,以其为前驱体,在弱酸性条件下通过离子交换反应将酸性黄25阴离子插层至ZnAl-LDHs/Al薄膜层间,制备了酸性黄25插层水滑石薄膜,并采用XRD、SEM、FTIR、TG-DTA、UV-Vis和色差计等手段对薄膜进行了表征。XRD和FTIR表征结果表明,酸性黄25阴离子成功地插层到了水滑石薄膜层间,ZnAl-LDHs的层间距由0.87 nm增加到2.96 nm,NO3-阴离子在1 384 cm-1处的特征吸收峰消失,同时出现了酸性黄25阴离子的特征吸收峰。SEM照片显示,水滑石晶片主要以c轴平行于铝片基底生长。TG-DTA分析、UV-Vis分析、色差分析和紫外光老化结果表明,插层后酸性黄25阴离子的耐热性和耐光性均得到了提高。     

Synthesis and UV absorption properties of 5, 5′-thiodisalicylic acid intercalated Zn−Al layered double hydroxides

5, 5′-Thiodisalicylic acid (TDSA) has been intercalated into a ZnAl-NO₃ layered double hydroxide (LDH) by an ion-exchange reaction. After intercalation of TDSA, the basal spacing in the LDH increased from 0.89 to 1.53 nm, suggesting that the TDSA anions were arranged in the interlayer galleries of ZnAl-TDSA-LDH as a tilted monolayer arrangement of dianions. The samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetry and differential thermal analysis (TGA-DTA), and UV-Visible spectroscopy (UV-Vis). The results show that the NO₃⁻ anions in the precursor have been completely replaced by TDSA anions to give ZnAl-TDSA-LDH having crystalline-layered structure. Detailed studies reveal the presence of a complex system of supramolecular interactions between LDH layers and TDSA anions. TGA-DTA curves suggest that the thermostability of TDSA was markedly enhanced by intercalation in the LDH host. Photostability tests show that the film of ZnAl-TDSA-LDH/PP possessed higher stability to UV radiation than either the film of TDSA/PP or pristine PP.     

Theoretical investigation on the structural and electronic properties of complexes formed by thymine and 2′-deoxythymidine with different anions

Hydrogen bonding interactions between thymine nucleobase and 2′-deoxythymidine nucleoside (dT) with some biological anions such as F⁻ (fluoride), Cl⁻ (chloride), OH⁻ (hydroxide), and NO₃ ⁻ (nitrate) have been explored theoretically. In this study, complexes have been studied by density functional theory (B3LYP method and 6-311++G (d,p) basis set). The relevant geometries, energies, and characteristics of hydrogen bonds (H-bonds) have been systematically investigated. There is a correlation between interaction energy and proton affinity for complexes of thymine nucleobase. The nature of all the interactions has been analyzed by means of the natural bonding orbital (NBO) and quantum theory atoms in molecules (QTAIM) approaches. Donors, acceptors, and orbital interaction energies were also calculated for the hydrogen bonds. Excellent correlations between structural parameter (δR) and electron density topological parameter (ρ _b) as well as between E(2) and ρ _b have been found. It is interesting that hydrogen bonds with anions can affect the geometry of thymine and 2′-deoxythymidine molecules. For example, these interactions can change the bond lengths in thymine nucleobase, the orientation of base unit with respect to sugar ring, the furanose ring puckering, and the C1′–N1 glycosidic linkage in dT nucleoside. Thus, it is necessary to obtain a fundamental understanding of chemical behavior of nucleobases and nucleosides in presence of anions.     

ZnO/Mg–Al layered double hydroxides as strongly adsorptive photocatalysts

Nanocomposites of magnesium aluminium layered double hydroxides with carbonate anions (Mg–Al–CO₃-LDHs) and ZnO nanorods were prepared by a homogeneous precipitation process. The ZnO nanorods give the calcined Mg–Al–CO₃-LDHs, strong adsorbents of anionic dyes, photocatalytic activity. The nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, and UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of the nanocomposites was investigated by degradation of acid red G in aqueous solution, and the nanocomposite with the ZnO-to-Mg–Al–CO₃-LDHs mass ratio of 1:1 had the highest photocatalytic activity in this photocatalytic reaction.     

Synthesis and anion recognition of neutral receptors based on multiamide calix[4]arene

Two multiamide calix[4]arenes (5, 6) were synthesized and characterized by NMR, MS and elemental analysis. The binding properties of receptors with some anions (π-O₂NPhOPO₃²⁻, π-O₂NPhO⁻, H₂PO₄⁻, Ac⁻, Cl⁻, Br⁻ and I⁻) were studied by UV-Vis spectra. The results indicate that the tetraamide calix[4]arenes (5, 6) have a good selectivity to the anions containing aromatic ring (π-O₂NPhOPO₃ ²⁻, π-O₂NPhO⁻). The 1 : 1 complexes between host and guest were formed through multiple hydrogen bonding and π-π interactions. The hosts 5 and 6 also show a definite binding ability for the anions (H₂PO₄⁻, Ac⁻, Cl⁻) that have no ultraviolet absorption, which provides a simple method of spectrum detection for these anions.     

Chlorido(dimethyl 2,2′‐bipyridine‐4,4′‐dicarboxylate‐κ2N,N′)(η5‐pentamethylcyclopentadienyl)rhodium(III) chloride 1‐hydroxypyrrolidine‐2,5‐dione disolvate

The title complex, [Rh(C₁₀H₁₅)Cl(C₁₄H₁₂N₂O₄)]Cl·2C₄H₅NO₃, has been synthesized by a substitution reaction of the precursor [bis(2,5‐dioxopyrrolidin‐1‐yl) 2,2′‐bipyridine‐4,4′‐dicarboxylate]chlorido(pentamethylcyclopentadienyl)rhodium(III) chloride with NaOCH₃. The Rh^III cation is located in an RhC₅N₂Cl eight‐coordinated environment. In the crystal, 1‐hydroxypyrrolidine‐2,5‐dione (NHS) solvent molecules form strong hydrogen bonds with the Cl⁻ counter‐anions in the lattice and weak hydrogen bonds with the pentamethylcyclopentadienyl (Cp*) ligands. Hydrogen bonding between the Cp* ligands, the NHS solvent molecules and the Cl⁻ counter‐anions form links in a V‐shaped chain of Rh^III complex cations along the c axis. Weak hydrogen bonds between the dimethyl 2,2′‐bipyridine‐4,4′‐dicarboxylate ligands and the Cl⁻ counter‐anions connect the components into a supramolecular three‐dimensional network. The synthetic route to the dimethyl 2,2′‐bipyridine‐4,4′‐dicarboxylate‐containing rhodium complex from the [bis(2,5‐dioxopyrrolidin‐1‐yl) 2,2′‐bipyridine‐4,4′‐dicarboxylate]rhodium(III) precursor may be applied to link Rh catalysts to the surface of electrodes.     

Stable UV absorption material synthesized by intercalation of squaric acid anion into layered double hydroxides

A novel UV absorption material of squaric acid (SA) anion (O₄O₄^2?) intercalated layered double hydroxides (LDHs) was successfully synthesized by the co-precipitation method. After intercalation, the interlayer distance of MgAl-SA-LDHs increased to 1.04 nm compared to those of MgAl-CO₃-LDHs and SA anions present in form of a monolayer in the interlayer of LDHs. Thermal stability of SA clearly enhanced by the intercalation and the suppression of the deintercalation ability of MgAl-SA-LDHs was superior to that of 4-hydroxy-3-methoxybenzoic acid intercalated LDHs. The results of UV-DRS indicate the potential application of MgAl-SA-LDHs as UV absorbers.     

Theoretical Evidence of Aromaticity in X3 − (X = B, Al, Ga) Species

We investigated the electronic structure and chemical bonding of the B₃ ^–, Al₃ ^–, and Ga₃ ^– anions, and the gas phase NaB₃, NaAl₃, and NaGa₃ molecules. We found that the ground state of the neutral gas phase salts contains an equilateral triangular anion interacting with a Na⁺ cation. The B₃ ^–, Al₃ ^–, and Ga₃ ^– anions possess two delocalized electrons and are found to be aromatic. The triangular anions have been shown to be related to recently synthesized organometallic compound containing an aromatic -Ga₃ ^2– unit, but they are differ from them by four valence electrons. The reason for earlier appearance of the -orbital in the B₃ ^–, Al₃ ^–, and Ga₃ ^– anions is discussed.     

Preparation of 5-benzotriazolyl-4-hydroxy-3-sec-butylbenzenesulfonate anion-intercalated layered double hydroxide and its photostabilizing effect on polypropylene

An organic UV absorber has been intercalated into a layered double hydroxide (LDH) host by ion-exchange method using ZnAl-NO₃-LDH as a precursor with an aqueous solution of the sodium salt of 5-benzotriazolyl-4-hydroxy-3-sec-butylbenzenesulfonic acid (BZO). After intercalation of the UV absorber, the interlayer distance in the LDHs increases from 0.89 to 2.32 nm. Infrared spectra and thermogravimetry and differential thermal analysis (TG-DTA) curves reveal the presence of a complex system of supramolecular host-guest interactions. The thermostability of BZO is markedly enhanced by intercalation in the LDH host. ZnAl-BZO-LDHs/polypropylene composite materials exhibit excellent UV photostability.     

Poly(1-allylimidazole)-grafted silica,a new specific stationary phase for reversed-phase and anion-exchange liquid chromatography

A new specific stationary phase based on poly(1-allylimidazole)-grafted silica has been synthesized and characterized, by infrared spectra, elemental analysis, thermogravimetric analysis and X-ray photoelectron spectroscopy. The results of test showed that poly(1-allylimidazole) can effectively mask the residual silanol groups and reduce the adverse effect of residual silanol. Using this stationary phase, phenol compounds, aniline compounds, and polycyclic aromatic hydrocarbons were successfully separated with symmetric peak shapes in the reversed-phase chromatography. Inorganic anions (IO₃⁻, BrO₃⁻, Br⁻, NO₃⁻, I⁻, SCN⁻) were also separated completely in the anion-exchange chromatography using sodium chloride solution as the mobile phase. The effects of pH and the concentration of eluent on the separation of inorganic anions were studied. The separation mechanism appears to involve the mixed interactions of hydrogen bonding, hydrophobic, π–π, electrostatic, and anion-exchange interactions.     

Spectroscopic Measurement of a Halogen Bond Energy

Halogen bonding (XB) has emerged as an important bonding motif in supramolecules and biological systems. Although regarded as a strong noncovalent interaction, benchmark measurements of the halogen bond energy are scarce. Here, a combined anion photoelectron spectroscopy and density functional theory (DFT) study of XB in solvated Br^? anions is reported. The XB strength between the positively‐charged σ‐hole on the Br atom of the bromotrichloromethane (CCl₃Br) molecule and the Br^? anion was found to be 0.63 eV (14.5 kcal mol^?1). In the neutral complexes, Br(CCl₃Br)_1,2, the attraction between the free Br atom and the negatively charged equatorial belt on the Br atom of CCl₃Br, which is a second type of halogen bonding, was estimated to have interaction strengths of 0.15 eV (3.5 kcal mol^?1) and 0.12 eV (2.8 kcal mol^?1).     

Synthesis,Structure, and Properties of SrC(NH)3, a Nitrogen‐Based Carbonate Analogue with the Trinacria Motif

Strontium guanidinate, SrC(NH)₃, the first compound with a doubly deprotonated guanidine unit, was synthesized from strontium and guanidine in liquid ammonia and characterized by X‐ray and neutron diffraction, IR spectroscopy, and density‐functional theory including harmonic phonon calculations. The compound crystallizes in the hexagonal space group P6₃/m, constitutes the nitrogen analogue of strontium carbonate, SrCO₃, and its structure follows a layered motif between Sr²⁺ ions and complex anions of the type C(NH)₃^2?; the anions adopt the peculiar trinacria shape. A comparison of theoretical phonons with experimental IR bands as well as quantum‐chemical bonding analyses yield a first insight into bonding and packing of the formerly unknown anion in the crystal.     

Analysis of ;W and O NMR chemical shifts in polyoxometalates by extended Hückel mo calculations

The extended Hückel molecular orbital (EHMO) calculations have been carried out using cluster approach to polyoxo anions, i.e. calculations have been done for a single octahedron MO₆ of different symmetry and results have been used to analyze ¹⁸³ W and ¹⁷ O NMR spectra. Using five d→d* energy differences for the individual WO₆ the sum Σ1/ (E_d→E_d*) have been calculated and plotted against the ¹⁸³ W chemical shift (from +258 to −670 ppm) for corresponding type of tungsten atom and practically a linear correlation between two parameters have been observed. This points out the electronic nature of the ¹⁸³ W chemical shift. Similar correlation have been found for the ¹⁷O NMR chemical shifts (−90 to +800 ppm) when the plotted against product of the R⁻³ Σ1/ (E_p→E_p*) where the R⁻³ bond length of the corresponding W–O bond. Increasing the ¹⁸³ W nuclear magnetic shielding with the calculated electron population on tungsten atom for closely related anions has been observed, but no general tendency between δ and the calculated electronic charge if the symmetry of polyhedron is changed is expected.     

Tris(1,9‐diethyl­adeninium) triiodide diiodide

X‐ray analysis of the title compound reveals three crystallographically distinct cations of 1,9‐diethyl­adeninium, two iodide anions and one triiodide anion in the asymmetric unit, giving six residues and the formula 3C₉H₁₄N₅⁺·I₃⁻·2I⁻. Standard purine nomenclature is used to identify the atoms of each adenine moiety. Hydrogen bonding is observed between atoms N6 and N7 of a pair of cations [N⋯N = 2.885 (4)/2.902 (3) and 2.854 (3)/2.854 (3) Å], with additional hydrogen bonding to I⁻ anions via the other N6 H atom [N⋯I = 3.708 (3), 3.738 (3) and 3.638 (3) Å]. The triiodide anion is not involved in hydrogen bonding. The bond lengths and angles of the 1,9‐diethyl­adeninium cations are compared with literature values and confirm the formation of the imine tautomer.     

Metallocages for Metal Anions: Highly Charged [Co@Ge9]5− and [Ru@Sn9]6− Clusters Featuring Spherically Encapsulated Co1− and Ru2− Anions

Endohedral clusters count as molecular models for intermetallic compounds—a class of compounds in which bonding principles are scarcely understood. Herein we report soluble cluster anions with the highest charges on a single cluster to date. The clusters reflect the close analogy between intermetalloid clusters and corresponding coordination polyhedra in intermetallic compounds. We now establish Raman spectroscopy as a reliable probe to assign for the first time the presence of discrete, endohedrally filled clusters in intermetallic phases. The ternary precursor alloys with nominal compositions “K₅Co_1.2Ge₉” and “K₄Ru₃Sn₇” exhibit characteristic bonding modes originating from metal atoms in the center of polyhedral clusters, thus revealing that filled clusters are present in these alloys. We report also on the structural characterization of [Co@Ge₉]^5? ( 1a ) and [Ru@Sn₉]^6? ( 2a ) obtained from solutions of the respective alloys.     

Metamagnetic DyAlO<Subscript>3</Subscript> nanoparticles with very low magnetic moment

Nanocrystalline dysprosium monoaluminate (DyAlO₃) has been synthesized by modified sol–gel method after sintering the precursor gel at 950 °C. The micro-structural features have been verified by X-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy. The XRD pattern confirms the formation of single-phase DyAlO₃; the average size of the nanoparticles is 50 nm. X-Ray photoelectron spectroscopy has been used to study the chemical composition and bonding in the samples. The binding energies of core-level electrons in Dy, Al and O in DyAlO₃ nanopowder have been found slightly shifted compared to the respective values of the same elements. Both AC and DC magnetic susceptibilities have been measured in the temperature range 2–300 K. Unusually low effective magnetic moment of Dy³⁺, μ_eff = 0.38, has been derived from the inverse magnetic susceptibility–temperature plot between 4 and 252 K. The Nèel temperature, T_N = 3.920 K and exchange interaction constant J/k = −1.74 K, have been also determined.     

From a Tb<Superscript>3+</Superscript> chelated compound to a hybrid material: selective emission responses to anions

A novel terbium 2-hydroxymethyl-benzoimidazole-6-carboxylic acid complex has been designed and unique emission changes to fluoride anions in comparison with HSO₄⁻, AcO⁻, Cl⁻, Br⁻, and I⁻ were observed. Then, the complex was encapsulated into an inorganic matrix. The novel hybrid material, with strong green emission was successfully synthesized as an anions receptor in water. More importantly, this hybrid material not only gave luminescence response to F⁻, but also to HSO₄⁻. Spectroscopic studies demonstrated that the recognition process for fluoride ions can be mainly ascribed to its hydrogen bonding interactions with hydrogen bond donor units (NH and OH). In case of hydrogen sulfate, the sensing effects can be probably attributed to its acidity instead of hydrogen bonding interactions.     

Recombination of Coordination Bonds of a Mononuclear Precursor into a 3D d‐d′ Heterometallic Coordination Polymer with Double Helices

Abstract. Based on a mononuclear precursor [Mn(Hstp)₂(4,4′‐Hbpy)₂] ( 1 ), a hetero‐metallic complex, [Mn₂Ni(stp)₂(4,4′‐bpy)(H₂O)₄] ( 2 ) [stp = 2‐sulfoterephthalate, 4,4′‐bpy = 4,4′‐bpyridine] was synthesized by solvothermal reaction. Single‐crystal X‐ray diffraction analysis reveals that the Mn^II ion of the precursor 1 is hexacoordinate by four oxygen atoms from two Hstp^2– anions and two nitrogen atoms from two protonated 4, 4′‐Hbpy, and hydrogen bonding plays a significant role in constructing 3D supramolecular structure. While complex 2 features a self‐weaving framework from 1D straight chains and 2D wavy networks with double helical chains. Magnetic behavior of complex 2 was analyzed in connection with its crystal structure, which exhibits the weak antiferromagnetic interactions between the Mn^II and Ni^II ions.     

Can anion interaction accelerate transformation of cytosine tautomers? Detailed view form QTAIM analysis

The relative stabilities and noncovalent interactions of the six low-lying energy tautomers of cytosine nucleobase with some biological anions (such as F^?, Cl^?, and CN^?) have been investigated in gas phase by density functional theory (DFT) method in conjunction with 6-311++G (d,p) atomic basis set. Furthermore, to systematically investigate all possible tautomerisms from cytosine induced by proton transfer, we describe a study of structural tautomer interconversion in the gas phase and in a continuum solvent using DFT calculation. We carried out geometrical optimizations with the integral equation formalism of polarizable continuum (IEF-PCM) model to account for the solvent effect, and the results were compared with those in the gas phase. The result of calculation revealed that anions bind mostly in a bidentate manner via hydrogen bond, and stabilization energies of these complexes are larger than those in the case when anions bind in a monodentate manner. The quantum theory of atoms in molecules (QTAIM), natural bonding orbital (NBO) and energy decomposition analysis (EDA) have also been applied to understand the nature of hydrogen bond interactions in these complexes. NBO analysis reveals that the interaction patterns between the anions and the tautomers are ??-type interaction between lone pairs and $ \sigma_{{_{{{\text{N}}--{\text{H}}}} }}^{*} $ , $ \sigma_{{_{{{\text{O}}--{\text{H}}}} }}^{*} $ and $ \sigma_{{_{{{\text{H}}--{\text{F}}}} }}^{*} $ antibonding orbitals. Also, according to these theories, the interactions are found to be partially electrostatic and partially covalent. EDA results identify that these bonds have less than 35% covalent character and more than 65% electrostatic, and the covalent character increases in different anions in the order F^??>?CN^??>?Cl^?. On the other hand, orbital interaction energies of complexes of F^? anion are more than those of Cl^? and CN^? complexes. The lower orbital interaction energies in complexes of Cl^? and CN^?anions imply less charge transfer and stronger ionic bond character. Furthermore, relationship between the orbital interaction energy (E ²) with hydrogen bonding energy (E _H···X) and the electron density (??(r)) with hydrogen bonding energy of F^?, Cl^? and CN^? complexes have also been investigated.     

Six-coordinate dinuclear hexaazamacrocyclic complexes of nickel(II), copper(II) and zinc(II) with tetraamide group ligands

Summary A series of 20–24 membered macrocyclic dinuclear transition metal complexes [M₂L¹X₄]-[M₂L⁴X₄] (M = Ni^II, Cu^II or Zn^II; X = Cl or NO₃) have been synthesized by template condensation of diethylenetriamine with dicarboxylic acids. The bonding and stereochemistry of the complexes have been characterized by i.r.,¹H-n.m.r., e.p.r. and electronic spectral studies, magnetic susceptibility and conductivity measurements. The Ni and Zn complexes exhibit octahedral geometry around the metal ion, whereas the Cu complexes possess a distorted octahedral geometry. Each metal ion is coordinated by two amide nitrogens and two secondary nitrogens of the diethylenetriamine moiety; the fifth and sixth coordination sites are occupied by the anions.