Interstitial Water Molecules Research Articles

Appraising the structural and magnetic properties in template assisted neodymium based metal organic frameworks

This study demonstrates synthesis of two novel lanthanide-based metal-organic frameworks, namely [{NdIII(5 N3-H2isa)2(H2O)2}(H2O)2}]∞ (1) and [{NdIII(5 N3-H2isa)2(H2O)2}(H2O)(1,2-PE)}]∞ (2), synthesized via solvothermal methods using 5-azidoisophthalic acid (5 N3-H2isa) and NdCl3. Both compounds were extensively characterized using single crystal X-ray diffraction, as well as other physicochemical techniques such as IR, TGA, PXRD, and elemental analysis. Structural differences were observed in both compounds depending on the nature of the template molecule used. Compound 1 exhibits an infinite 2D architecture with lattice-occluded water molecules within the 2D layers. In contrast, compound 2, where 1-(-2-pyridyl)-2-(4-pyridyl)ethylene (1,2-PE) was used as the template, shows replacement of interstitial water molecules by the template molecule, resulting in significant changes in overall pore topology which is further corroborated by BET analysis. These structural variations were further supported by magnetic behaviour analyses, indicating an antiferromagnetic behaviour for both compounds.

The crystal structure of a mononuclear PrIII complex with cucurbit[6]uril.

A new mononuclear complex, penta-aqua-(cucurbit[6]uril-κ2 O,O')(nitrato-κ2 O,O')praseodymium(III) dinitrate 9.56-hydrate, [Pr(NO3)(CB6)(H2O)5](NO3)2·9.56H2O (1), was obtained as outcome of the hydro-thermal reaction between the macrocyclic ligand cucurbit[6]uril (CB6, C36H36N24O12) with a tenfold excess of Pr(NO3)3·6H2O. Complex 1 crystallizes in the P21/n space group with two crystallographically independent but chemically identical [Pr(CB6)(NO3)(H2O)5]2+ complex cations, four nitrate counter-anions and 19.12 inter-stitial water mol-ecules per asymmetric unit. The nona-coordinated PrIII in 1 are located in the PrO9 coordination environment formed by two carbonyl O atoms from bidentate cucurbit[6]uril units, two oxygen atoms from the bidentate nitrate anion and five water mol-ecules. Considering the differences in Pr-O bond distances and O-Pr-O angles in the coordination spheres, the coordination polyhedrons of the two PrIII atoms can be described as distorted spherical capped square anti-prismatic and muffin polyhedral.

Revealing the Molecular Origin of Anisotropy around Chloride Ions in Bulk Water.

A clear picture of the local solvation structure around halide anions in liquid water remains elusive. This discussion has been stimulated by pioneering simulation results that proposed a "hydrophobic cavity" around anions in the bulk, which is analogous to air at the air-water interface. However, there is also sound experimental and theoretical evidence that halide ions are rather symmetrically solvated in the bulk, leading to a different viewpoint. Using extensive ab initio molecular dynamics simulations of an aqueous Cl- solution, we indeed find an anisotropic arrangement of H-bonded versus interstitial water molecules. The latter are not H-bonded to the anions and thus do not couple much electronically to Cl-. The resulting purely electronic anisotropy of the local solvation environment correlates with that structural anisotropy, which however should not be understood as an empty cavity─as it would be at the air-water interface─but rather contains interstitial water molecules.

Preparation of Low-Defect Manganese-Based Prussian Blue Cathode Materials with Cubic Structure for Sodium-Ion Batteries via Coprecipitation Method.

Sodium-ion batteries have important application prospects in large-scale energy storage due to their advantages, such as safety, affordability, and abundant resources. Prussian blue analogs (PBAs) have a stable and open framework structure, making them a very promising cathode material. However, high-performance manganese-based Prussian blue cathode materials for sodium-ion batteries still suffer from significant challenges due to several key issues, such as a high number of vacancy defects and a high crystal water content. This article investigates the effects of the Fe-Mn molar ratio, Mn ion concentration, and reaction time on the electrochemical performance of MnHCF during the coprecipitation process. When Fe:Mn = 1:2, c(Mn2+) = 0.02 mol/L, and the reaction time is 12 h, the content of interstitial water molecules in the sample is low, and the Fe(CN)6 defects are few. At 0.1 C, the prepared electrode has a high initial discharge specific capacity (121.9 mAh g-1), and after 100 cycles at 0.2 C, the capacity retention rate is 65% (~76.2 mAh g-1). Meanwhile, the sample electrode exhibits excellent reversibility. The discharge capacity can still be maintained at around 75% when the magnification is restored from 5 C to 0.1 C. The improvement in performance is mainly attributed to two aspects: On the one hand, reducing the Fe(CN)6 defects and crystal water content is conducive to the diffusion and stable structure of N. On the other hand, reducing the reaction rate can significantly delay the crystallization of materials and optimize the nucleation process.

Crystal structure and thermally enhanced photoluminescence in Eu(III) coordination polymers self-assembled from p-nitrobenzoic acid

Luminescent thermal quenching is a very troublesome thing for the practical application of luminescent materials, but also is a very common phenomenon. In theory, artificially reducing the number of quenching group around the luminescent lanthanide ion can effectively enhance the luminescence of lanthanide luminescent materials. In this paper, {[Eu2(NBA)6(H2O)4]∙H2O}n [Eu-NBA, NBA = p-nitrobenzoic acid] coordination polymers containing abundant coordination and interstitial water molecules were synthesized via hydrothermal methods. The chemical composition, crystal structures, and thermal stability of Eu-NBA coordination polymers were systemically investigated by Frontier-transfer infrared (FTIR) spectra, single-crystal X-ray diffraction and thermogravimetric analysis. X-ray diffraction analysis results revealed that Eu-NBA coordination polymers were crystallized into one-dimensional (1D) chain structures, where the adjacent Eu3+ ions were linked together by bidentate and/or tetradentate bridging carboxylate groups of the NBA ligands. The temperature-dependent photoluminescence spectra revealed that the shape and intensity of the luminescence spectra strongly depended on the coordination environment around Eu3+, and significant luminescent thermal enhancement was observed. These experimental results provided useful theoretical support for further understanding of the luminescence enhancement mechanism of lanthanide coordination polymers.

Probing the Conformational Preference to β-Strand during Peptide Self-Assembly.

Alanine-rich tetrapeptides like A3K dominantly exist as polyproline II helices in dilute aqueous solutions. However, during self-assembly, based on the free energy calculation in implicit solvent for various peptide conformations, only the peptides in the β-strand conformation can be packed closely. This necessitates the conformational transition to the β-strand commonly observed during peptide self-assembly such as in amyloid fibril formation. In fact, the closest interpeptide distance of 4.8 Å is consistent with the interstrand distance determined from the X-ray diffraction pattern of many amyloid fibrils. The position of free energy minimum obtained from implicit solvent calculation matches exactly with the explicit solvent simulation through umbrella sampling when the peptide conformations are restrained, demonstrating the applicability of the former for rapid screening of peptide configurations favorable for self-assembly. The barrier in the free energy profile in the presence of water arises out of the entropic restriction on the interstitial water molecules while satisfying the hydrogen bonding of both the peptides by forming water mediated hydrogen bond bridge. Further, the high energy barrier observed for the β-strand suggests that peptides initially tend to self-assemble in the polyproline II structure to mitigate the desolvation energy cost; the transition to the β-strand would happen only in the later stage after crossing the barrier. The umbrella sampling simulations with peptides allowed to change conformations, relative to each other, confirm the dynamic conformational transition during the course of the self-assembly supporting the "dock and lock" mechanism suggested for amyloid fibrillar growth.

A crystal structure refinement of uralolite, Ca2Be4(PO4)3(OH)3∙5H2O, from Weinebene, Austria

The crystal structure of uralolite, Ca2Be4(PO4)3(OH)3·5H2O, from the spodumene deposit of Weinebene, Carinthia, Austria, has been refined with X-ray single crystal data gathered on a CCD diffractometer. Uralolite is monoclinic, space group P21/n, a = 6.553(1), b = 16.005(3), c = 15.979(3) Å, β = 101.63(1)°, V = 1641.5(5) Å3. While previously only isotropic displacement parameters and no hydrogen atom positions were reported for uralolite, now anisotropic displacement parameters were used for non-hydrogen atoms and hydrogen atoms were located and refined yielding R1 = 0.038 for 3909 observed reflections. Uralolite is built up from corrugated layers [Be4(PO4)3(OH)3]4- parallel to (010), which contain Z-shaped groups of four BeO4 tetrahedra sharing corners via three OH groups and are further crosslinked by PO4 tetrahedra. Two Ca atoms in Ca(Ophosphate)5(H2O)2 coordination and an interstitial water molecule link these layers along [010]. The OH groups and the Ca-bonded H2O molecules are all involved in hydrogen bonds with O···O distances of 2.780(2) − 3.063(2) Å and O-H···O angles of 150(1) − 179(1)° excluding a bifurcated bond. The interstitial water molecule displays a distorted tetrahedral environment of O atoms and accepts and donates each two hydrogen bonds. The crystal structure exhibits a C2/c pseudosymmetry for the [Be4(PO4)3(OH)3]4- layers and the Ca atoms. However, the disposition of the water molecules and an asymmetric hydrogen bond pattern involving OH groups as well as H2O molecules are decisive for the lowering of the symmetry of the structure to the true space group P21/n.

Investigating the role of interstitial water molecules in copper hexacyanoferrate for sodium-ion battery cathodes

The electrochemical performance of prussian blue analogues (PBAs) can be determined by the number of interstitial water molecules in the channels, which inhibits the insertion and diffusion of sodium-ions in an aqueous electrolyte system.

Tris‐dipicolinate Lanthanide Complexes: Influence of the Second Hydration Sphere on the Solid‐State Luminescence Properties

AbstractA series of tris‐dipicolinate europium complexes featuring different complexes has been prepared, and their photophysical study has been performed in the solid state highlighting the crucial role of second sphere water molecules. The non‐radiative deactivation constant (knr) varies significantly with the number of interstitial water molecules and their distance to the europium emitting center. The complex (NBu4)3[Eu(DPA)3], featuring the most lipophilic cation, exhibits excellent solubility and remarkable photophysical properties in aprotic solvents.

Ni-Containing Electrolytes for Superior Zinc-Ion Aqueous Batteries with Zinc Hexacyanoferrate Cathodes.

A one-step coprecipitation process is designed to synthesize zinc hexacyanoferrate (ZnHCF) cathodes in aqueous zinc-ion batteries (ZIBs). The morphology of the cathode is influenced by the concentration of the precursor solution and valence of iron ions. The rhombohedral ZnHCF sample exhibits high crystallinity on the microscale in the cut-angle cubic structure, whereas Na-rich NaZnHCF contains many interstitial water molecules in the rhombic nanoplates. Both samples show effective insertion of Zn ions in the aqueous ZnSO4 solution. ZnHCF shows a specific capacity of 66.7 mA h g–1, a redox voltage of 1.73 V, and fast decline in a few cycles. On the other hand, NaZnHCF has a lower specific capacity of 48.2 mA h g–1, showing two voltage platforms and robust cycling stability. However, owing to serious side reactions, both samples have low Columbic efficiency. To improve the properties such as Coulombic efficiency, specific capacity, and cycling stability, Ni ions are introduced by adding 10 wt % NiSO4 to the ZnSO4 electrolyte. The ZnHCF cathode in the Ni-containing electrolyte has the best properties such as a high specific capacity of 71.2 mA h g–1 at a current density of 100 mA g–1, 93% retention of the Coulombic efficiency, and a good rate performance manifested by a reversible capacity of 58.2 mA h g–1 at 1 A g–1. The results reveal a strategy to improve the electrochemical properties of aqueous ZIBs by modifying the electrolytes.

Crystal structure of an indium-salicyl-hydroximate complex cation: [In4(H2shi)8(H2O)6](NO3)4·8.57H2O.

The synthesis and crystal structure for the title compound, hexa-aqua-hexa-kis(μ-2-hy-droxy-benzene-carbo-hydrox-a-mato)bis-(2-hy-droxy-benzene-carbo-hydrox-a-m-ato)tetra-indium(III) tetra-nitrate 8.57-hydrate + unknown solvent, [In4(H2shi)8(H2O)6](NO3)4·8.57H2O·solvent, where H2shi- is salicylhydrox-imate (C7H5NO3), are reported. The complex cation of the structure, [In4(H2shi)8(H2O)6]4+, is a dimer with a step-like topology and possesses an inversion center that relates each [In2(H2shi)4(H2O)3]2+ side of the complex cation. Each InIII ion is seven-coordinate with a penta-gonal-bipyramidal geometry, and the salicyl-hydroximate ligands have a 1- charge as only the oxime oxygen of the ligand is deprotonated. Four inter-stitial nitrate anions maintain the charge balance of the compound. One of the nitrate anions (and its symmetry equivalent) is disordered over two different orientations with an occupancy ratio of 0.557 (7) to 0.443 (7). The inter-stitial solvent water mol-ecules show substantial disorder. Approximately 8.57 water mol-ecules per formula unit were refined as disordered and partially occupied, while a suitable model could not be devised for the other extensively disordered solvent mol-ecules (water and possibly methanol as this was the synthesis solvent). Thus, these latter solvent mol-ecules were instead treated with the SQUEEZE routine [Spek (2015). Acta Cryst. C71, 9-18.] as implemented in the program PLATON, and the procedure corrected for 151 electrons within solvent-accessible voids of 367 Å3.

Changes in hydration of liposome membranes exposed to nanosecond electric pulses detected by wide-field Coherent anti-Stokes Raman microspectroscopy

Electropulsation has become a powerful technological platform for electromanipulation of cells and tissues for various medical and biotechnological applications, but the molecular changes that underlay the very first initiation step of this process have not been experimentally observed.Here, we endowed a wide-field Coherent anti-Stokes Raman Scattering platform with an ad-hoc electromagnetic exposure device and we demonstrated, using artificial lipid vesicles (i.e. liposomes), that electropulsation is initiated by the increase of interstitial water content in liposome membranes. A pulse-dependent accumulation of the interstitial water molecules is observed in the membranes and a plausible mechanism supported by a computational electrochemical model is presented and discussed.

As-Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe-Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering.

A novel mixed-valent hybrid chiral and polar compound, Fe7As3Se12(en)6(H2O), has been synthesized by a single-step solvothermal method. The crystal structure consists of 1D [Fe5Se9] chains connected via [As3Se2]-Se pentagonal linkers and charge-balancing interstitial [Fe(en)3]2+ complexes (en = ethylenediamine). Neutron powder diffraction verified that interstitial water molecules participate in the crystal packing. Magnetic polarizability of the produced compound was confirmed by X-ray magnetic circular dichroism (XMCD) spectroscopy. X-ray absorption spectroscopy (XAS) and 57Fe Mössbauer spectroscopy showed the presence of mixed-valent Fe2+/Fe3+ in the Fe-Se chains. Magnetic susceptibility measurements reveal strong antiferromagnetic nearest neighbor interactions within the chains with no apparent magnetic ordering down to 2 K. Hidden short-range magnetic ordering below 70 K was found by 57Fe Mössbauer spectroscopy, showing that a fraction of the Fe3+/Fe2+ in the chains are magnetically ordered. Nevertheless, complete magnetic ordering is not achieved even at 6 K. Analysis of XAS spectra demonstrates that the fraction of Fe3+ in the chain increases with decreasing temperature. Computational analysis points out several competing ferrimagnetic ordered models within a single chain. This competition, together with variation in the Fe oxidation state and additional weak intrachain interactions, is hypothesized to prevent long-range magnetic ordering.

Low- and high-density forms of liquid water revealed by a new medium-range order descriptor

We present in this paper a computational approach based on molecular dynamics simulations and graph theory to characterize the structure of liquid water considering not only the local structural arrangement within the first (or second) hydration shell, but also the medium- to long-range order. In particular, a new order parameter borrowed from the graph-theory framework, i.e., the node total communicability (NTC), is introduced to analyze the dynamic network of water molecules in the liquid phase. This order parameter is able not only to accurately report on the different high-density-liquid (HDL) and low-density-liquid (LDL) water phases postulated in the liquid–liquid phase transition hypothesis, but also to show that HDL-like forms are not homogeneous but rather composed by regions at different local density. In particular, the presence of patches at very high density with an increased number of interstitial water molecules is unveiled, both under pressure and at ambient conditions.

Synthesis and crystal structure of the lanthanum cyanurate complex La[H2N3C3O3]3 · 8.5 H2O

Abstract Single crystals of La[H2N3C3O3]3 · 8.5 H2O were obtained from stoichiometric amounts of as-precipitated La(OH)3 with cyanuric acid (CYA) [H3N3C3O3]3 in a boiling aqueous solution, followed by slow cooling and evaporation of water under ambient conditions. According to the X-ray structure analysis of the colorless and transparent crystals, La[H2N3C3O3]3 · 8.5 H2O adopts the triclinic space group P1 (no. 1) and exhibits the unit-cell parameters a = 987.24(7), b = 1110.97(8), c = 1179.81(9) pm, α = 113.716(2), β = 97.053(2), γ = 101.502(2)° for Z = 2. The CYA is singly deprotonated to give monoanions [H2N3C3O3]– which are O,N-coordinated to the La3+ cations. These dihdrogencyanurate anions are assembled in ribbons with two crystallographically different La3+ cations coordinating to either one or two different ligands, respectively. The coordination sphere of the La3+ cations is comprised of water molecules, and interstitial water molecules fill the dead volume of the crystals. The anionic ribbons are stacked to maximize the contact between the six-membered rings, showing distances of about 330 pm.

The Crystal Structures of Two Hydro-closo-Borates with Divalent Tin in Comparison: Sn(H2O)3[B10H10] · 3 H2O and Sn(H2O)3[B12H12] · 4 H2O

Single crystals of Sn(H2O)3[B10H10] · 3 H2O and Sn(H2O)3[B12H12] · 4 H2O are easily accessible by reactions of aqueous solutions of the acids (H3O)2[B10H10] and (H3O)2[B12H12] with an excess of tin metal powder after isothermal evaporation of the clear brines. Both compounds crystallize with similar structures in the triclinic system with space group Pbar{1 } and Z = 2. The crystallographic main features are electroneutral {}_{infty }^{1} {Sn(H2O)3/1[B10H10]3/3} and {}_{infty }^{1} { Sn(H2O)3/1[B12H12]3/3} double chains running along the a-axes. Each Sn2+ cation is coordinated by three water molecules of hydration (d(Sn–O) = 221–225 pm for the B10 and d(Sn–O) = 222–227 pm for the B12 compound) and additionally by hydridic hydrogen atoms of the three nearest boron clusters (d(Sn–H) = 281–322 pm for the B10 and d(Sn–H) = 278–291 pm for the B12 compound), which complete the coordination sphere. Between these tin(II)-bonded water and the three or four interstitial crystal water molecules, classical bridging hydrogen bonds are found, connecting the double chains to each other. Furthermore, there is also non-classical hydrogen bonding between the anionic [BnHn]2− (n = 10 and 12) clusters and the crystal water molecules pursuant to B–Hδ−cdotsδ+H–O interactions often called dihydrogen bonds.

Multi-dimensional copper(I) and silver (I) coordination polymers assembled with a pyridyl bis-urea macrocyclic ligand

We report the synthesis of a new flexible multimodal macrocyclic ligand, protected pyridyl bis-urea macrocycle 1, and two of its coordination polymers Cu2I2(1)2·(CH3CN)1.63 (2) and [Ag(1)](NO3).(H2O)2.49 (3). The ligand possesses conformational flexibility and adopts different conformations and binding modes depending on the metal ions. The crystal structure of 2 shows a 2D coordination network constructed from rhomboidal Cu2I2 dimer units and 1 as a bridging ligand binding through the pyridyl N atoms. 3 forms a sophisticated 3D structure with 1D chains formed by N-Ag-N links between pyridyl N atoms of two adjacent macrocyclic ligands and Ag(I) ions. These chains form 2D layers through longer Ag-O interactions and the chains are linked together into a 3D network by hydrogen bonding involving interstitial water molecules. These results indicate the potential of ligand 1 in the self-assembly of coordination polymers with diverse topology and functional applications.

Synthesis and crystal structure of a heterobimetallic nickel-manganese 12-metallacrown-4 methanol disolvate monohydrate compound.

The synthesis and crystal structure of the title compound [systematic name: di-μ-acetato-tetra-kis-(μ4-N,2-dioxido-benzene-1-carboximidato)hexa-methano-ltetra-manganese(III)nickel(II) methanol disolvate monohydrate], [Mn4Ni(C7H4NO3)4(C2H3O2)2(CH4O)6]·2CH4O·H2O or Ni(OAc)2[12-MCMn(III)N(shi)-4](CH3OH)6·2CH3OH·H2O, where MC is metallacrown, -OAc is acetate, and shi3- is salicyl-hydroximate, are reported. The macrocyclic metallacrown is positioned on an inversion center located on the NiII ion that resides in the central MC cavity. The macrocycle consists of an MnIII-N-O repeat unit that recurs four times to generate an overall square-shaped mol-ecule. Both the NiII and MnIII ions are six-coordinate with an octa-hedral geometry. In addition, the MnIII ions possess an elongated Jahn-Teller distortion along the z-axis of the coordination environment. The inter-stitial water mol-ecule is slightly offset from and disordered about an inversion center.

Aluminum vanadate hollow spheres as zero-strain cathode material for highly reversible and durable aqueous zinc-ion batteries

The intercalation and conversion compounds have long been exploited in aqueous zinc-ion batteries such as Prussian blue, VS2, Zn0.25V2O5, MnO2 and so on. However, the lattice distortion of host materials during Zn ions insertion is the major issue with cycling stability. Metastable-phase vanadium oxide with bilayer structure, low crystallinity and interstitial water molecules may decrease lattice distortion, leading to long cycle stability. Herein we demonstrate H11Al2V6O23.2 (HAVO) microspheres with large interlayer distance (d001 ​= ​1.336 ​nm) as cathode materials for zinc-ion batteries. The Zn ions insertion/extraction behaviors are investigated deeply. Ex-situ XRD and Raman spectra of HAVO collected at various states show no shift during battery operation, indicating the lattice distortion is nearly negligible. In addition, the lattice structure is well maintained even after 1000 cycles and the HAVO delivers an outstanding reversibility (88.6% capacity retention after 7000 cycles).

X-ray structures of catalytic intermediates of cytochrome c oxidase provide insights into its O2 activation and unidirectional proton-pump mechanisms

Cytochrome c oxidase (CcO) reduces O2 to water, coupled with a proton-pumping process. The structure of the O2-reduction site of CcO contains two reducing equivalents, Fe a32+ and CuB1+, and suggests that a peroxide-bound state (Fe a33+-O--O--CuB2+) rather than an O2-bound state (Fe a32+-O2) is the initial catalytic intermediate. Unexpectedly, however, resonance Raman spectroscopy results have shown that the initial intermediate is Fe a32+-O2, whereas Fe a33+-O--O--CuB2+ is undetectable. Based on X-ray structures of static noncatalytic CcO forms and mutation analyses for bovine CcO, a proton-pumping mechanism has been proposed. It involves a proton-conducting pathway (the H-pathway) comprising a tandem hydrogen-bond network and a water channel located between the N- and P-side surfaces. However, a system for unidirectional proton-transport has not been experimentally identified. Here, an essentially identical X-ray structure for the two catalytic intermediates (P and F) of bovine CcO was determined at 1.8 Å resolution. A 1.70 Å Fe-O distance of the ferryl center could best be described as Fe a34+ = O2-, not as Fe a34+-OH- The distance suggests an ∼800-cm-1 Raman stretching band. We found an interstitial water molecule that could trigger a rapid proton-coupled electron transfer from tyrosine-OH to the slowly forming Fe a33+-O--O--CuB2+ state, preventing its detection, consistent with the unexpected Raman results. The H-pathway structures of both intermediates indicated that during proton-pumping from the hydrogen-bond network to the P-side, a transmembrane helix closes the water channel connecting the N-side with the hydrogen-bond network, facilitating unidirectional proton-pumping during the P-to-F transition.