Stacks Of Anions Research Articles

Synthesis and structure of pentakis(2-aminopyridinium) nonavanado(V)tellurate(VI)

In the title compound, (C5H7N2)5[TeV9O28], the tellurium and vanadium atoms are statistically disordered over two of the ten metal-atom sites in the [TeV9O28]5– heteropolyanion. The anions stack along [100] and are extended into a three-dimensional supramolecular network through N—H...O and weak C—H...O hydrogen bonds involving the self-assembled 2-aminopyridinium pentamers, which are linked by C—H...π and π–π stacking interactions. The most important contributions to the Hirshfeld surface arise from O...H/H...O (54.8%), H...H (17.8%) and C...H/H...C (13.4%) contacts.

Empirical, computational studies and non-covalent interactions analysis of a novel salt with cadmium transition metal precursor

In this research paper, (C3H5N2)6[CdCl4][CdCl6] was successfully synthesized using a slow evaporation process. The structure was confirmed through single-crystal X-ray crystallography, FT-IR, and thermal analysis. The material was found to crystallize in the tetragonal system (space group I41/a) and the following parameters a = b = 12.0872 (8) Å; c = 24.6985 (16) Å, the crystal packing shows parallel layers of cations and stacks of discrete anions positioned at y = 1/4 and 3/4. The junction between the monoprotonated imidazolium cations and the anions, along with the crystal structure stability, relies on Cl···H−N, and Cl···H−C hydrogen bonds. Computational investigations, conducted using the B3LYP method with 6–311++G(d,p) and LANL2DZ mixed basis set, demonstrated close alignment between the computed and the experimental data, providing insights into the material's geometrical and vibrational properties. The non-covalent interactions were studied through Atoms-In-Molecule (AIM) and Reduced Density Gradient (RDG) analysis and quantitatively using the Hirshfeld surfaces associated with 2D fingerprint plots. Furthermore, thermal stability was assessed through Thermogravimetric and Differential Scanning Calorimetry (TG–DSC) analysis.

Spin and dielectric transitions promoted by dimerization of anionic radical stacks and volume-conserving motion of cations in an ion-pair compound.

Demonstrating the mechanism of a structural phase transition (SPT) is significantly important for guiding the precise design of new phase transition materials. Herein, an ion-pair compound [DPIm][Ni(mnt)2] (1, DPIm+ = 1,3-dipropylimidazolium and mnt2- = maleonitriledithiolate) has been obtained and thoroughly characterized through microanalysis, spectral, and thermal analysis techniques. The [Ni(mnt)2]- anions form columnar stacks, featuring one-dimensional (1D) S = ½ spin chains. 1 undergoes an SPT, associated with thermal, magnetic, and dielectric anomalies. The SPT results from the competition between antiferromagnetic (AFM) coupling interactions within anion stacks and elastic deformation of the lattice. The magnetic anomaly arises from changes in the magnetic coupling constant within an anion stack between two phases, while the dielectric anomaly is due to the volume-conserving motion of the imidazolyl ring in the cation. 1 exhibits high-κ characteristics, attributed to the electron polarization of both anions and cations, ion displacement, and dipole orientation polarization of cations. It is also demonstrated that a longer dialkyl chain inhibits the rotational freedom of the imidazolyl ring, resulting in the absence of a plastic crystal state in 1 compared to others containing [Ni(mnt)2]- and dialkylimidazolium.

Nanoarchitectonics and Molecular Docking of 4-(Dimethylamino)Pyridin-1-Ium 2-3 Methyl-4-Oxo-Pyri-Do[1,2-a]Pyrimidine-3-Carboxylate

A retro-Claisen reaction of 1-(4-oxo-4H-pyrido [1,2-a]pyrimidin-3-yl)butane-1,3-dione, 3, in the presence of potassium hydroxide and 4-dimethylamino-pyridine has been carried out, leading to 4-(dimethylamino)pyridin-1-ium 2-methyl-4-oxo-pyrido [1,2-a]pyrimidine-3-carboxylate 5. A plausible mechanism explaining the formation of the title compound has been proposed. A single-crystal X-ray diffraction analysis confirms the crystal structure of the isolated organic salt (5). In the crystal, the title compound adopts a layered structure where there are stacks of cations and anions formed by slipped π-stacking interactions. These stacks are linked by regions consisting of water molecules that are hydrogen-bonded together. DFT and Hirshfeld surface analysis supported the experimental results of the molecular geometry and the intercontacts between different units in the crystal. The druglikeness, ADMET properties, and predicted targets were investigated, and the observed results suggest that 5 may act as a carbonic anhydrase I inhibitor. The assumption is confirmed by docking 5 into the active binding site of carbonic anhydrase, which shows it to have good binding affinities and to form stable complexes with the active residues of carbonic anhydrase I.

Phase Control in the Synthesis of Iron Sulfides.

The identity and repeating arrangement of atoms determine the properties of all solids. Even combinations of two atoms can have multiple crystal structures of varying stoichiometries and symmetries with vastly different electronic and chemical behaviors. The conditions of existing bottom-up routes for achieving one phase over another are serendipitous, and the links among precursor reactivity, decomposition mechanism, temperature, and time are elusive. Our studies take a systematic approach to understanding the role that the precursor kinetic decomposition has in the synthesis of iron sulfides, isolating it from other mechanistic factors. The data suggest that phase determination in binary solids can be logically predicted through the consideration of the anion stacking and thermodynamic relationships between phases. Mapping these relationships allows for the rational synthetic targeting of metastable crystalline phases.

Oxonium diimidotriphosphate from the hydrolysis of trimetaphosphimic acid

Trimetaphosphimates decompose not only upon heating but also in water. Hydrolysis of trimetaphosphimic acid leads to the formation of diimidotriphosphoric acid by ring opening. Single-crystal structure determination using synchrotron radiation revealed the oxonium salt of the latter acid with double stacks of rod-shaped anions along [001]. Anharmonic displacement parameters were used to model slight disorder of part of the anions. These are interconnected by hydrogen bonds within and between the stacks. Powder X-ray diffraction confirmed phase purity. At temperatures above 120 °C, diimidotriphosphoric acid decomposes into unknown crystalline compounds. It thus seems a promising precursor for the synthesis of oxonitridophosphates at moderate temperatures.Graphical abstract

Thermochromism of rapid responses to temperature changes versus mechanochromism in a Ni-dithiolene complex salt.

A thermochromic or mechanochromic material can switch between at least two stable states in response to changes in temperature or static pressure/strain. In this study, we investigated a Ni-dithiolene dianion salt, 1,1'-diheptyl-4,4'-bipyridinium bis(maleonitriledithiolato)nickelate (1), and found that its cations and anions stack alternately to form a uniform mixed stack. These mixed stacks then combine to form a molecular solid through Coulomb and van der Waals interactions. Upon heating, 1 undergoes a reversible phase transition at around 340/320 K during the first heating/cooling cycle, resulting in rapid thermochromism with a color change from green (stable state) to red (metastable state) within a few seconds. This is the first report of a crystal of bis(maleonitriledithiolato)nickelate(II) salt with green color. Additionally, 1 exhibits irreversible mechanochromism, intense near-IR absorbance, and a dielectric anomaly. The structural phase transition is responsible for these properties, as it induces alterations in the π-orbital overlap between the anion and cation within a mixed stack. The intense near-IR absorbance arises from the ion-pair charge transfer transition from [Ni(mnt)2]2- to 4,4'-bipyridinium.

Switchable magnetic, dielectric, conductivity, and phase transition properties of charge-transfer crystals

The properties can be switched between different states and can be used in sensors, displays, and memory devices. In this study, two multi-functional switchable materials [C5-Pmim][Ni(mnt)2] (1) and [C6-Hmim][Ni(mnt)2] (2) (where mnt2-= maleonitriledithiolate, C5-Pmim = 1-pentyl-3-methylimidazolium, and C6-Hmim = 1-hexyl-3-methylimidazolium) have been designed and synthesized, which has segregated cation and anion stacks in the crystal structure. 1 shows two-step switchable dielectric transition with a thermal hysteresis loop accompanying structure phase transition. Dielectric transition of 1 can be attributed to the reorientation of the polar cations and crystal to mesophase transition. Switchable conductivity properties of 1 and 2 were realized by the crystal to mesophase structure transition. The conductivity of the mesophase for 1 and 2 is higher than the corresponding crystal phase. Furthermore, magnetic phase transition with the non-common hysteresis loop for 2 is observed being triggered by the structure and dielectric transition. To the best of our knowledge, this study might be the rare multi-functional switchable examples with dielectric, conductivity, and magnetic transition.

Azide-Locked Prodrug Co-Assembly into Nanoparticles with Indocyanine Green for Chemophotothermal Therapy.

Fabrication of self-delivery drug systems can surmount low drug bioavailability and achieve a precise therapeutic process. In this study, a hydrogen sulfide-responsive (H2S) small molecule prodrug was synthesized by linking two chemotherapy drugs, camptothecin (CPT) and gemcitabine (GT), using a reductive disulfide bond simultaneously with a lock GT strategy using a H2S-responsive azide group (denoted as N3-GT-CPT). The ingenious design endows the easy coprecipitation peculiarity of the prodrug with clinical indocyanine green (ICG) via a combined interaction force of hydrophobic, π-π stacking, and electrostatic interactions of anions and cations, thus producing a more stable and multifunctional therapeutic nanosystem. Considering the great photothermal and imaging ability of ICG, the obtained nanosystem showed an excellent therapeutic ability against colon tumors in vitro and in vivo with selective response to intercellular H2S, thus offering a good combination-based multiple therapy for treatment of tumors.

Anionic Stacks of Alkali-Interlinked Yttrium and Dysprosium Bicyclooctatetraenes in Isolation.

Electrospray ionization of THF solutions of preformed [K(18-c-6)][M(COT)2] (M = Dy(III), Y(III); COT = C8H82-,18-c-6 = C12H24O6) yields the isolated species [(M(COT)2)n+1 + nK]- with n = 0-3. High-resolution ion mobility spectrometry combined with density functional theory calculations performed for the n = 0-2 aggregates indicate that anionic multidecker stacks interlinked by potassium cations are formed. The alternating metal ions are aligned linearly: COT2--M3+-COT2--K+-COT2--M3+-COT2-. The different M3+ ionic radii lead to slight but resolvable changes in mobility and thus collision cross sections indicative of different overall heights of the multidecker stacks. CID measurements show that the aggregates fragment by cleavage at the K+ interconnections.

Crystal structure of osimertinib mesylate Form B (Tagrisso), (C28H34N7O2)(CH3O3S)

The crystal structure of osimertinib mesylate Form B has been solved and refined using synchrotron X-ray powder diffraction data and optimized using density functional techniques. Osimertinib mesylate Form B crystallizes in space group P-1 (#2) with a = 11.42912(17), b = 11.72274(24), c = 13.32213(22) Å, α = 69.0265(5), β = 74.5914(4), γ = 66.4007(4)°, V = 1511.557(12) Å3, and Z = 2. The crystal structure is characterized by alternating layers of cation–anion and parallel stacking interactions parallel to the ab-planes. The cation is protonated at the nitrogen atom of the dimethylamino group, which forms a strong hydrogen bond between the cation and the anion. That hydrogen atom also participates in a weaker intramolecular hydrogen bond to an amino nitrogen. There are two additional N–H⋅⋅⋅O hydrogen bonds between the cation and the anion. Several C–H⋅⋅⋅O hydrogen bonds also link the cations and anions. The powder pattern has been submitted to ICDD® for inclusion in the Powder Diffraction File™.

Shape and nanocrystal transformations

Nanomaterials Cation exchange reactions that change the composition of a nanocrystal (NC) under mild conditions usually preserve the sublattice of the larger anions. Li et al. found that the shape of roxbyite (Cu1.8S) nanocrystals, which have a distorted, hexagonal, close-packed sulfide anion sublattice, affected the outcome of exchange reactions with cobalt ions. Flat nanoplates retained the anion lattice and formed cobalt sulfide, but tall nanorods transformed into Co9S8 nanocrystals with a cubic, close-packed structure. Facile crystal plane sliding in the taller nanocrystals appears to have driven the different layer stacking of sulfide anions. Science , abh2741, this issue p. [332][1] [1]: /lookup/doi/10.1126/science.abh2741

Transformations of Ionic Nanocrystals via Full and Partial Ion Exchange Reactions.

ConspectusElaborate chemical synthesis methods allow the production of various types of inorganic nanocrystals (NCs) with uniform shape and size distributions. Many single-step synthesis approaches, such as the reduction of metal ions, the decomposition of metal complexes, double replacement reactions, and hydrolysis, have been adapted to promote the generation of monodisperse metal and ionic NCs. However, the question has become, how can we synthesize NCs with thermodynamically metastable phases or very complex structures? The transformation of already-synthesized NCs via elemental substitutions, such as ion exchange reactions for ionic NCs and galvanic replacement reactions for metal NCs, can overcome the difficulties facing conventional one-step syntheses. In particular, NC ion exchange reactions have been studied with numerous combinations of foreign ions and ionic NCs with various shapes. They have been investigated extensively because the reactions proceed under relatively mild conditions thanks to the large surface-to-volume ratio of the NCs relative to their bulk form. The functionality of the resulting ionic NCs, including semiconducting and plasmonic properties, can be easily tuned in a wide range, from the visible to near-infrared. Because anions generally have much larger ionic radii than cations within the frameworks of NCs, the cation exchange reactions proceed much faster than the anion exchange reactions. For ionic NCs above a critical size, the anion framework remains intact, and the original shape of the parent NCs is retained throughout the cation exchange reaction. In contrast, the anion exchange reaction often provides the new NCs with unique structures, such as hollow or anisotropically phase-segregated assemblies.This Account focuses on the full and partial ion exchange reactions involving ionic NCs, which have been thoroughly investigated by our group and others while highlighting important aspects such as the preservation of appearance and dimensions. First, we discuss how each type of ion exchange reaction progresses to understand the morphologies and crystal structures of their final products. This discussion is supported by emphasizing important examples, which help to explore the formation of NCs with thermodynamically metastable phases and complex structures, and other significant features of the ion exchange reactions leading to structure-specific functions. As a special case, we examine how the shape-dependent anionic framework (surface anion sublattice and stacking pattern) of polyhedral Cu2O NCs determines the crystalline structure of the anion-exchanged products of hollow CuxS NCs. In addition, we review the characteristic anion exchange behavior of metal halide perovskite NCs observed in our laboratory and other laboratories. Finally, a general outline of the transformation of NCs via ion exchange reactions and future prospects in this field are provided.

Fabrication of Keggin-type Polyoxometalate Membranes at the Gas-Liquid Interface.

Keggin-type polyoxometalates are effective catalytic materials for acid-catalyzed reactions and oxidation reactions. In this paper, we describe the fabrication of a porous membrane of Keggin-type polyoxometalates at the gas-liquid interface and the structural characterization of the membrane via aberration-corrected scanning transmission electron microscopy. The membrane is formed by the introduction of n-octylamine vapor into aqueous solution of Keggin-type silicotungstic acid (H4SiW12O40) and cesium chloride. The membrane obtained has the cubic structure of cesium salts of silicotungstic acid (CsxH4-xSiW12O40), exposing the (110) crystal plane preferentially. The single-unit cell layer of the upper surface of the membrane is densely packed with Keggin anions, while the lower layers are rich in vacancies at both the anion and cation sites. This structure results from the fast formation of the single-unit cell layer at the surface of the solution and slow stacking of Keggin anions under the layer.

Design of a One-Dimensional Stacked Spin Peierls System with Room-Temperature Switching from Quantum Mechanical Predictions.

Planar bis-1,2-dithiolene complex anions of a transition metal (denoted as [M(dithiolato)2]- and M = Ni, Pd, or Pt ion) favor forming columnar stacks of anions in the crystal that feature S = 1/2 spin-chains, and such a spin-chain compound often undergoes a spin-Peierls-type transition, making this a promising material for conducting and magnetic switching. However, current examples show the transition temperatures are far too low for most applications. We use quantum mechanics to predict that changing the cation arrangement from the boat-type to the chair-type packing configuration in a spin-Peierls-type [Ni(dithiolato)2]- complex will substantially stabilize the antiferromagnetic coupling, dramatically increasing the transition temperature. We estimate that the [Ni(mnt)2]-based complexes (mnt = maleonitriledithiolate) with chair-type packing of cations will lead to critical temperatures of ∼170, ∼252, and ∼310 K for S-, Se-, and Te-based mnt, respectively. We also suggest how to stabilize the chair-type configurations of these systems.

π-Metalated [15]Paracyclophanes: Synthesis and Binding to Oxo-Anions via Anion-π Interactions.

The host-guest properties of [15]paracyclophane ([15]PCPs) are engendered by π-metalation, which exhibits fantastic regioselectivity toward a macrocyclic molecule. The synthesis and characterization of mono-, di-, and trimetalated [15]PCPs are discussed in this article, and the anion binding behavior of 3Ru-[15]PCP-II6+, one of the trimetalated [15]PCPs, driven by anion-π interactions, is comprehensively demonstrated in both solution and the solid state. The anion binding properties of 3Ru-[15]PCP-II6+ in solution are investigated by 1H NMR titrations, showing selectivity toward ReO4- in both organic and aqueous solutions. The binding mode is unexpected; the anionic guest stacks over the host rather than threads it. This selectivity for ReO4- is also supported by water-nitromethane extraction experiments, which demonstrate that its partition from water into the organic phase by 3Ru-[15]PCP-II·6OTf is maintained to some extent in the presence of excess Cl-, SO42-, H2PO4-, NO3-, and ClO4-.

The structure and Hirshfeld surface analysis of the salt 3-methacryl-amido-N,N,N-tri-methyl-propan-1-aminium 2-acryl-amido-2-methyl-propane-1-sulfonate.

The title salt, C10H21N2O+·C7H12NO4S-, comprises a 3-methacryl-amido-N,N,N-tri-methyl-propan-1-aminium cation and a 2-acryl-amido-2-methyl-propane-1-sulfonate anion. The salt crystallizes with two unique cation-anion pairs in the asymmetric unit of the ortho-rhom-bic unit cell. The crystal studied was an inversion twin with a 0.52 (4):0.48 (4) domain ratio. In the crystal, the cations and anions stack along the b-axis direction and are linked by an extensive series of N-H⋯O and C-H⋯O hydrogen bonds, forming a three-dimensional network. Hirshfeld surface analysis was carried out on both the asymmetric unit and the two individual salts. The contribution of inter-atomic contacts to the surfaces of the individual cations and anions are also compared.

Two-dimensional Acetate-based Light Lanthanide Fluoride Nanomaterials (F-Ln, Ln = La, Ce, Pr, and Nd): Morphology, Structure, Growth Mechanism, and Stability.

Discovery of novel two-dimensional (2D) materials is of fundamental importance but remains challenging. In this work, we design a simple and facile bottom-up approach to fabricate a new family of 2D acetate-based light lanthanide fluoride nanomaterials (F-Ln, Ln = La, Ce, Pr, Nd) at room temperature and atmosphere pressure, for the first time. Various characterization techniques confirm that as-synthesized F-Ln exhibit an ultrathin morphology with thickness up to 1.45 nm and lateral dimensions up to several hundred nanometers. Microstructure analysis demonstrates that F-Ln are a series of defect-rich 2D nanomaterials, which consist of nanocrystals with sub-10 nm domains. Structure characterization of F-Ce, a typical example, infers that BN-like F-Ce one-atom-layers sandwiched by intercalated acetate anions stack alternately along [001] direction to form nanocrystal building blocks of F-Ce. The study of growth mechanism suggests that three procedures are involved in the formation of F-Ce: hydrolysis reaction of cerium(III) acetate, structure transformation induced by fluorine ions, and assembly process guided by acetate anions. The as-prepared nanosheets show excellent stability with respect to environment stimuli such as air, heat, solvent, and high-energy electron beam. This study enriches the library of 2D materials and paves the way for future application of such 2D materials in areas such as catalysis, adsorption, separation, and energy storage/conversion.

Influence of organic cations on the stacking of semiquinone radical anions

A series of salts of tetrachloro- and tetrabromosemiquinone radical anions reveal four types of stacks: 1) pancake bonded dimers, 2) pancake-bonded trimers, 3) equidistant radicals and 4) a novel type of equidistant stacks of partially charged radicals.

Wide Magnetic Thermal Memory Effect (∼55 K) Above Room Temperature Coupled to a Structure Phase Transition of Lattice Symmetry Reduction in High-Temperature Phase in an S = 1/2 Spin Chain Molecule Crystal.

One-dimensional (1D) S = 1/2 Heisenberg antiferromagnetic (AFM) chain system shows frequently a spin-Peierls-type transition owing to strong spin-lattice coupling. From high-temperature phase (HTP) to low-temperature phase (LTP), the spin chain distortion leads to the reduction in lattice symmetry in LTP, called the symmetry breaking (SB) phase transition. Herein, we report the first example of 1D S = 1/2 AFM molecular crystal, [Et3( n-Pr)N][Ni(dmit)2] (Et3( n-Pr)N+ = triethylpropylammonium, dmit2- = 2-thioxo-1,3-dithiole-4,5-dithiolate), which shows a structural phase transition with lattice symmetry increase in LTP, which is contrary to the SB phase transition. Particularly, the structure phase transition leads to magnetically bistable state with TC↑ ≈ 375 K, TC↓ ≈ 320 K, and surprisingly large thermal hysteresis (∼55 K). Additionally, LTP and HTP coexist in a temperature region near TC but not at TC in this 1D spin system. The large hysteresis is related to the huge deformation of anion stack, which needs high activation energy for the structure transformation and magnetic transition between LTP and HTP. This study would not only provide new insight into the relationship of spin-Peierls-type transition and structure phase transition but also offer a roadmap for searching molecular-scale magnetic bistable materials, which are in huge demand in future electronic, magnetic, and photonic technologies.