Anionic Sheets Research Articles

Actinide Sulfate Structures from Caustic Solvents.

Four unique actinide sulfates were synthesized using solvothermal techniques with strong acids. The first plutonium(III) sulfate structure, Pu(HSO4)3, was synthesized and is isostructural with analogous lanthanide-based frameworks. A similar synthesis approach yielded crystals of NpNa0.5(HSO4)15(SO4)1.5, which has a comparable framework to the Pu(III) compound, but the neptunium metal is tetravalent and sodium is incorporated into the structure, as confirmed by chemical analysis. Anhydrous neptunium sulfate, Np(SO4)2, is reported and is isotypic with U(SO4)2. Finally, (H3O)2(UO2)(SO4)2, which contains a uranyl sulfate sheet structure, was synthesized and characterized. The corresponding sheet anion topology has previously been reported with various oxyanions, but this is the first report that contains sulfate. The sheets are charge balanced by hydronium cations in the interstitial space. This compound readily degrades and forms crystals of the synthetic analogue to the uranium mineral shumwayite, which is likely thermodynamically favorable. All four of these actinide sulfate compounds were synthesized in extremely acidic media, resulting in interesting and unique structures.

Crystal structure of a layered phosphate molybdate K2Gd(PO4)(MoO4)

The title compound dipotassium gadolinium(III) phosphate(V) molybdate(VI), K2Gd(PO4)(MoO4), was synthesized from a high-temperature melt starting from GdF3 as a source of gadolinium. Its structure is isotypic with other M I 2 M III(M VIO4)(PO4) compounds, where M I = Na, K or Cs, and M III = rare-earth cation, M VI = Mo or W. The three-dimensional framework is built up from [Gd(PO4)(MoO4)] anionic sheets, which are organized by adhesion of [GdPO4] layers and [MoO4] tetrahedra stacked above and below these layers. The interstitial space is occupied by K cations having eightfold oxygen coordination. The polyhedron of GdO8 was estimated to be a triangular dodecahedron by the continuous shape measurement method.

Anionic clay surface facilitates electron transfer between an excited donor encapsulated within a cationic capsule and a cationic electron acceptor

Fluorescence quenching of an excited guest encapsulated within a cationic host by a cationic molecule was examined on an anionic inorganic surface. Repulsion between the host and the quencher was overcome by adsorbing both an anionic surface. Dimethyl stilbene (DMS), octa amine (OAm216+), viologen derivatives (VD2+) and saponite are used as guest, cationic capsule, cationic electron acceptor and anionic inorganic surface, respectively. The fluorescence behavior of DMS within OAm216+ (denoted as DMS@OAm216+) was observed by steady-state and time-resolved fluorescence measurements. As a result of electron transfer the fluorescence of DMS@OAm216+ was quenched by VD2+ under the presence of saponite, while no quenching was observed in the absence of saponite. Those results indicate that the dynamic electron transfer between DMS@OAm216+ and VD2+ which are electrostatically repulsive, can be observed in the (DMS@OAm216+)-VD2+-saponite triad supramolecular system where the two cationic systems are brought closer by the anionic clay sheet.

Two-Dimensional Mixed Lead/Bismuth Oxychloride Based Materials As Anodes for Sodium-Ion Batteries

The continuous pursuit on building low cost and sustainable batteries to efficiently harvest renewable energy from intermittent sources is ever expanding. The research on Na-ion technology has gained significant interest due to inexpensive and broad availability of precursor materials. Until now, various Na-ion anodes including carbonaceous materials such hard carbon, alloy-based materials such as Bi, Pb, Sb and Sn based systems and conversion materials have been explored1. Along this line, the recent chase on two dimensional (2D) materials such as chalcogenides, MXenes and van der Waals types oxyhalide heterostructures, have become more intense due to their excellent electrical and structural properties 2. Among them, 2D Sillén-type metal oxyhalide heterostructures (MOX), due to their unique layered structure consisting of anionic sheets interleaved with cationic layers have gain particular interest as electrode materials. BiOCl is one such candidate with fluorite-like layers, [Bi2O2]2+ intergrown with halide Cl– anions, have been studied as anode in rechargeable batteries. However, its application is mainly challenged by rapid capacity decay originating from particle pulverization and unstable solid electrolyte interphase (SEI).In this work, 2D layered mixed lead bismuth oxychloride nanosheets (BiOCl4 and PbBiO2Cl 3) were synthesized by new rapid room temperature chemical precipitation route. In former anode, the electrolyte engineering approach has been used to enhance the cycling stability of BiOCl and at the same time, its electrochemical (de)sodiation mechanism is also clarified through in-operando XRD studies, which reveals the reversible formation of Bi ↔ NaBi ↔ cubic-Na3Bi phases. On the other hand, the later anode, i.e., 2D-PbBiO2Cl was further investigated with the combined in-operando XRD and ex-situ TEM, XPS studies, which reveal a distinct (de)sodiation process of the 2D-PbBiO2Cl in comparison with reported Na-(Pb/Bi) phase diagram. This 2D heterostructure demonstrated stable sodium storage performance (~250 mAh g–1 for 250 cycles at 100 mA g–1). Henceforth, the detailed understanding of formation process of these two structures (BiOCl and PbBiO2Cl) at room temperature using material characterizations and electrochemical studies combined with operando findings will be discussed to comprehend the reversible storage mechanism of 2D-MOX type heterostructures as anodes in SIBs.

Room-Temperature Synthesis and Stable Na-Ion Storage Performance of Two-Dimensional Mixed Lead-Bismuth Oxychloride Heterostructure

The endless pursuit on building low cost and sustainable batteries to effectively harvest renewable energy from intermittent sources is ever increasing. The research on Na-ion technology has gained significant interest due to inexpensive and broad availability of precursor materials. Until now, various Na-ion anodes have been explored including carbonaceous materials such hard carbon, alloy-based materials such as Bi, Pb, Sb and Sn based systems and conversion materials [1]. Along this line, the recent chase on two dimensional (2D) materials such as chalcogenides, MXenes and van der Waals types oxyhalide heterostructures, have become more intense due to their excellent electrical and structural properties [2]. Among them, 2D Sillén-type metal oxyhalide heterostructures (MOX), due to their unique layered structure consisting of anionic sheets interleaved with cationic layers have gain particular interest as electrode materials. BiOCl is one such candidate with fluorite-like layers, [Bi2O2]2+ intergrown with halide Cl– anions, have been studied as anode in rechargeable batteries. For instance, the 2D-(Bi1-xFex)OCl have increased insertion kinetics in Li-ion storage performances [3] in comparison with unsubstituted BiOCl, whereas 2D-(Bi1-xSbx)OCl heterostructures have shown synergetic effect of (Bi/Sb) alloys on with improved K-ion storage capacity [4]. However, in continuation, the further assessment of other mixed cationic Sillén heterostructures with the crystal structures of [BixM1-xO2]n+ (M = Na+/Ca2+/Pb2+/Fe3+/Sb3+; n = +1, +2 and +3) layers intergrown with single/double/triple halide anionic layers, remain unexplored. This is mainly challenged by their current synthesis strategies which demand high temperature, longer reaction durations, toxic chemicals, and complex reaction setup.In this work, 2D layered lead bismuth oxychloride (PbBiO2Cl) heterostructure nanosheets were synthesized by new rapid room temperature chemical precipitation route within ~45 mins. The stepwise reaction intermediates were harvested and investigated further with XRD and SEM mechanistic studies. The formation proceeds through topotactic ion exchange route from analogous PbBiO2NO3 intermediate. When employed as an anode material in Na half-cell configurations (as presented in Figure 1), this 2D heterostructure demonstrated stable sodium storage performance (~250 mAh g–1 for 250 cycles at 100 mA g–1). Surprisingly, the electrochemical profile of the 2D-PbBiO2Cl significantly differs from those of its individual counterparts Pb, Bi anodes. This was further investigated with the combined in-operando XRD and ex-situ TEM, XPS studies, which reveal a distinct (de)sodiation process of the 2D-PbBiO2Cl in comparison with reported Na-(Pb/Bi) phase diagram. Henceforth, the detailed understanding of formation process of 2D-PbBiO2Cl at room temperature using non-operando material characterizations and electrochemical studies combined with operando findings will be discussed to comprehend the reversible storage mechanism of 2D-PbBiO2Cl type heterostructures as anodes in SIBs.

New Radical Cation Salts Based on BDH-TTP Donor: Two Stable Molecular Metals with a Magnetic [ReF6]2− Anion and a Semiconductor with a [ReO4]− Anion

Three radical cation salts of BDH-TTP with the paramagnetic [ReF6]2− and diamagnetic [ReO4]− anions have been synthesized: κ-(BDH-TTP)4ReF6 (1), κ-(BDH-TTP)4ReF6·4.8H2O (2) and pseudo-κ″-(BDH-TTP)3(ReO4)2 (3). The crystal and band structures, as well as the conducting properties of the salts, have been studied. The structures of the three salts are layered and characterized by alternating κ-(1, 2) and κ″-(3) type organic radical cation layers with inorganic anion sheets. Similar to other κ-salts, the conducting layers in the crystals of 1 and 2 are formed by BDH-TTP dimers. The partial population of positions of Re atoms and disorder in the anionic layers of 1–3 are their distinctive features. Compounds 1 and 2 show the metallic character of conductivity down to low temperatures, while 3 is a semiconductor. The ac susceptibility of crystals 1 was investigated in order to test the possible slow relaxation of magnetization associated with the [ReF6]2− anion.

Litharge-derived compounds structurally based on layers of Cl− and Br−-centered tetrahedra: Synthesis and structures of the new representatives of MX(ReO4) family (M=Ba, Pb; X=Cl, Br)

Two new layered barium perrhenate halides, BaX(ReO4) (X = Cl and Br), were prepared and their structures were refined from single-crystal and powder data, respectively. Both compounds are isostructural to the previously reported BaCl(MnO4), exhibiting a matlockite (PbFCl)-derived motif. The structure of previously reported PbBr(ReO4) was also refined, in order to obtain a complete data set; it is similar to PbCl(ReO4). The structures of Ba and Pb compounds correspond to the centro- and non-centrosymmetric versions (pseudo-polymorphs) of the same motif corresponding to the alternation of [M2X2]2+ litharge-derived slabs and double sheets of perrhenate anions. Strong relationships exist to the structures of LnX(TO4) (X = Cl, Br; T = Mo, W) which are monoclinically distorted versions of the orthorhombic permanganates and perrhenates. Crystal chemistry and further perspectives of the compounds with litharge slabs constructed of Cl, Br, and I-centered tetrahedra are discussed.

Layered assembly of cationic and anionic supramolecular polymers.

The chemical synthesis and the supramolecular assembly of an aromatic oligoamine are described. The self-assembly of the cationic oligomers in aqueous solution leads to the formation of vesicular objects. The assembly process of the oligomers is monitored by absorption and fluorescence spectroscopy and the formed vesicles are characterized by atomic force and transmission electron microscopy. The electrostatic complementarity of anionic supramolecular polymers sheets and the cationic vesicles is used for a layered assembly process.

Polymorphism in a Multicomponent Crystal System of Trimesic Acid and t-Butylamine

Polymorphism in a multicomponent crystal system of trimesic acid (TMA) and t-butylamine (TBA) with stoichiometry (TMA)2(TBA)3 is reported, with the discovery and structural characterization of two polymorphs with rhombohedral and triclinic symmetries. In each polymorph, the TBA molecules exist as protonated cations, and the two independent TMA molecules are deprotonated by loss of a total of three protons (the specific protonation state of each TMA anion depends on the interpretation of hydrogen-bond disorder in the crystal structure). Both structures are based on sheets of TMA anions arranged in a hydrogen-bonded honeycomb network; these sheets are essentially planar in the rhombohedral polymorph but corrugated in the triclinic polymorph. The TBA cations are linked by hydrogen bonding to the TMA anions in this network, with the t-butyl groups occupying the void space within the honeycomb network and the regions of space between adjacent sheets. Periodic DFT-D calculations suggest that the rhombohedral polymorph is more energetically stable than the triclinic polymorph.

Dissolution of poorly soluble uranyl phosphate phases in the Metaautunite Subgroup under uranyl peroxide cage cluster forming conditions

Abstract Uranyl phosphate minerals are widespread in uranium deposits and normally exhibit very low solubility in aqueous systems. Uranyl phosphates of the autunite group and metaautunite subgroup impact the mobility of uranium in the environment and have inspired groundwater remediation strategies that emphasize their low solubility. The importance of soluble uranium-bearing macro-anions, including nanoscale uranyl peroxide cage clusters, is largely unexplored relative to solubilization of normally low-solubility uranium minerals. Eight synthetic analogs of metaautunite subgroup minerals have been prepared and placed in various alkaline aqueous solutions containing hydrogen peroxide and tetraethylammonium hydroxide. Each uranyl phosphate studied has a topologically identical anionic sheet of uranyl square bipyramids and phosphate tetrahedra combined with various cations (Li+, Na+, K +, Rb+, Cs+, Mg2+, Ca2+, Ba2+) and water in the interlayer. Uranyl peroxides formed under many of the experimental conditions examined, including solid studtite [(UO2)(O2)(H2O)2](H2O)2 and soluble uranyl peroxide cage clusters containing as many as 28 uranyl ions. Uranyl phosphate solids in contact with solutions in which uranyl peroxide cage clusters formed dissolved extensively or completely. The greatest dissolution of uranyl phosphates occurred in systems that contained cations with larger hydrated radii, Li+ and Na+. The details of the uranium speciation in solution depended on the pH and counter cations provided from the interlayers of the uranyl phosphate solids.

Square Grid Metal-Chloranilate Networks as Robust Host Systems for Guest Sorption.

Reaction of the chloranilate dianion with Y(NO3 )3 in the presence of Et4 N+ in the appropriate proportions results in the formation of (Et4 N)[Y(can)2 ], which consists of anionic square-grid coordination polymer sheets with interleaved layers of counter-cations. These counter-cations, which serve as squat pillars between [Y(can)2 ] sheets, lead to alignment of the square grid sheets and the subsequent generation of square channels running perpendicular to the sheets. The crystals are found to be porous and retain crystallinity following cycles of adsorption and desorption. This compound exhibits a high affinity for volatile guest molecules, which could be identified within the framework by crystallographic methods. In situ neutron powder diffraction indicates a size-shape complementarity leading to a strong interaction between host and guest for CO2 and CH4 . Single-crystal X-ray diffraction experiments indicate significant interactions between the host framework and discrete I2 or Br2 molecules. A series of isostructural compounds (cat)[MIII (X-an)2 ] with M=Sc, Gd, Tb, Dy, Ho, Er, Yb, Lu, Bi or In, cat=Et4 N, Me4 N and X-an=chloranilate, bromanilate or cyanochloranilate bridging ligands have been generated. The magnetic properties of representative examples (Et4 N)[Gd(can)2 ] and (Et4 N)[Dy(can)2 ] are reported with normal DC susceptibility but unusual AC susceptibility data noted for (Et4 N)[Gd(can)2 ].

Dihydrogenphosphate Anionic Template-Assisted Hydrogen Bonded Networks in 2-Benzylaminopyridinium and 4-Ethyoxyanilinium Dihydrogenphosphate Salts

In the title compounds, namely 2-benzylaminopyridinium dihydrogenphosphate C12H13N 2 + ·H2PO 2 − , (I) and 4-ethoxyanilinium dihydrogenphosphate C8H12NO+·H2PO 4 − , (II), the H2PO 4 − anions form a one-dimensional chain and a two-dimensional supramolecular sheet built through O-H⋯ O hydrogen bonds. The asymmetric unit of (II) consists of two symmetry-independent molecules with almost similar geometrical parameters, differing in the orientation of cations with respect to the anions. The 2-benzylaminopyridinium cations of I are linked to the anionic one-dimensional chain, while the 4-ethoxyanilinium cations of II are anchored to the anionic two-dimensional sheet through N-H⋯ O hydrogen bonds. These anion-cation interactions lead to the formation of an organic-inorganic supramolecular one-dimensional chain and two-dimensional sheets in I and II respectively. In dihydrogenphosphate salts the formation of anionic supramolecular motifs and networks are very much influenced by the nature of cations and their interaction with the H2PO 4 − anions.

The sulfonate group as a ligand: a fine balance between hydrogen bonding and metal ion coordination in uranyl ion complexes.

Nine uranyl ion complexes have been synthesized using two kinds of sulfonate-containing ligands, i.e. 2-, 3- and 4-sulfobenzoic acids (2-, 3- and 4-SBH2), which include additional carboxylic donors, and p-sulfonatocalix[4]arene (H8C4S), with additional phenolic groups, and [Ni(cyclam)]2+, [Cu(R,S-Me6cyclam)]2+ or PPh4+ as counterions. [Ni(cyclam)][UO2(4-SB)2(H2O)2]·2CH3CN (1) and [Ni(cyclam)][UO2(3-SB)2(H2O)2] (2) are molecular species in which only the carboxylate groups are coordinated to uranyl, the sulfonate groups being essentially hydrogen bond acceptors. In contrast, uranyl κ1-O(S);κ1-O(C)-chelation is found in the four complexes involving 2-SB2-, different bridging interactions producing diverse geometries. [UO2(2-SB)2Ni(cyclam)]·H2O (3) crystallizes as a two-dimensional (2D) assembly with fes topology, in which uranyl ion dimeric subunits are bridged by six-coordinate NiII cations. Complexes [UO2(2-SB)2Cu(R,S-Me6cyclam)]2·2H2O (4) and [(UO2)2(2-SB)2(C2O4)Cu(R,S-Me6cyclam)] (5), obtained together from the same solution, are a molecular tetranuclear complex and a 2D species with fes topology, respectively, depending on the coordination number, 5 or 6, of the CuII cation. The complex [PPh4]2[(UO2)2(2-SB)3(H2O)]·H2O (6) is a one-dimensional (1D), ribbon-like coordination polymer with a layered packing of alternate cationic and anionic sheets. No heterometallic complex was obtained with H8C4S, but the copper-only compound [{Cu(R,S-Me6cyclam)}5(H3C4S)2]·17H2O (7) displays mixed coordination/hydrogen bonding association of the copper azamacrocycle complex with the phenolic groups. The complexes [PPh4]5[UO2(H4C4S)(H2O)4][UO2(H3C4S)(H2O)4]·14H2O (8) and [PPh4]3[UO2(H3C4S)(H2O)3]·9H2O (9) were crystallized from the same solution and are a molecular complex and a 1D polymer, respectively, with monodentate sulfonate coordination to uranyl, while [PPh4]2[UO2(H4C4S)(H2O)3]·11H2O (10) is also a 1D polymer. The anionic complexes in the last three complexes form layers (9) or double layers (8 and 10) separated from one another by hydrophobic layers of PPh4+ cations. The balance between coordination and hydrogen bonding interactions with the macrocyclic ligands provides an indication of the energy of the sulfonate coordinate bond. Complex 6 is the only luminescent species in this series, albeit with a low quantum yield of 3%, and its emission spectrum is typical of a uranyl complex with five equatorial donors.

Dihydrogenphosphate anionic template-assisted hydrogen bonded networks in 2-benzylaminopyridinium and 4-ethyoxyanilinium dihydrogenphosphate salts

In the title compounds, namely 2-benzylaminopyridinium dihydrogenphosphate C12H13N2+⋅H2PO4–, (I) and 4-ethoxyanilinium dihydrogenphosphate C8H12NO+⋅H2PO4–, (II), the H2PO4– anions form a one-dimensional chain and a two-dimensional supramolecular sheet built through O—H⋯O hydrogen bonds. The asymmetric unit of II consists of two symmetry-independent molecules with almost similar geometrical parameters, differing in the orientation of cations with respect to the anions. The 2-benzylaminopyridinium cations of I are linked to the anionic one-dimensional chain, while the 4-ethoxyanilinium cations of II are anchored to the anionic two-dimensional sheet through N—H⋯O hydrogen bonds. These anion-cation interactions lead to the formation of an organic-inorganic supramolecular one-dimensional chain and two-dimensional sheets in I and II respectively. In dihydrogenphosphate salts the formation of anionic supramolecular motifs and networks are very much influenced by the nature of cations and their interaction with the H2PO4– anions.

Structural, mechanical and Raman spectroscopic characterization of the layered uranyl silicate mineral, uranophane-α, by density functional theory methods

ABSTRACTThe layered uranyl silicate clay-like mineral, uranophane-α, Ca(UO2)2(SiO3OH)2·5H2O, was studied by first-principles calculations based on the density functional theory method. The structure, observed in nature in a wide variety of compounds having the uranophane sheet anion topology, is confirmed here for the first time by means of rigorous theoretical solid-state calculations. The computed lattice parameters, bond lengths and bond angles were in very good agreement with the experimental ones, and the calculated X-ray powder trace accurately reproduced its experimental counterpart. The mechanical properties of uranophane-α, for which there are no experimental data for terms of comparison, were determined, and the satisfaction of the mechanical stability Born conditions of the structure was demonstrated by calculations of the elasticity tensor. The Raman spectrum was computed by the density functional perturbation theory and compared with the experimental spectrum. The vibrational properties of this mineral were well characterized, showing a good performance in all of the studied spectral range. Theoretical methods allowed assignment of the Raman bands to vibrations localized in different fragments within the crystal unit cell. Finally, the possibility of incorporation of strontium inside the uranophane structure was studied. The computed structure, X-ray powder trace and Raman spectrum of Sr-exchanged uranophane were very close to those of the ordinary Ca-uranophane.

Synergetic Influence of Alkali-Metal and Lone-Pair Cations on Frameworks of Tellurites.

Four new tellurites were hydrothermally synthesized by the adjustment of different alkali-metal ions, and all of the compounds demonstrate 2D layer structures. Rb2Te4O9·2H2O in centrosymmetric space group Pccn features a new [Te4O9]∞2- anion sheet consisting of rare [Te8O22]12- groups. RbNaTe8O14(OH)6·8H2O in CS space group P1̅ exhibits a [Te4O9]∞2- anion layer by linkage of the TeO3 and TeO4 units. NaPb4Te4O12F located in CS space group P4/ n displays an unusual [PbTeO3]∞ neutral layer made up of PbO3 and TeO3 trigonal pyramids. RbK3Te8O18·5H2O lying in noncentrosymmetric (NCS) space group Cc shows a [Te4O9]∞2- anion layer composed of the TeO3 and TeO4 units; its second-harmonic-generation response is about 0.2 times that of KH2PO4; structure analysis and local dipole moment calculation verify that the weak polarization mostly from the [Te4O9]∞2- layer results from the inverse arrangement of TeO n units, and further theoretical calculation confirms that TeO n groups dominate the band gap of RbK3Te8O18·5H2O and optical properties. Meanwhile, systematic analyses of a series of metal tellurites reveal that the alkali-metal cations exert a considerable impact on polarization of the crystal structures, which puts forward a feasible idea about the design of new NCS materials.

2-[(Prop-2-yn-1-yl)amino]anilinium chloride

The title compound, C9H11N2+·Cl−, is an anilinium chloride salt, in which the Car—N—C—C (ar = aromatic) torsion angle is −84.95 (18)°. In the crystal, a bilayer of cation–anion sheets runs parallel to (100), primarily through an extensive range of N—H...Cl hydrogen bonds. Weak offset π-stacking interactions between the benzene rings stack molecules alongc.

(BEDT-TTF)2Cu2(HCOO)5: An Organic-Inorganic Hybrid Conducting Magnet.

A dual‐functional organic–inorganic hybrid (BEDT‐TTF)2Cu2(HCOO)5 (1) (BEDT‐TTF=bis(ethylenedithio)tetrathiafulvalene) was obtained through the electrochemical oxidation of neutral BEDT‐TTF in the presence of an ammonium salt of the one‐dimensional copper‐formate framework [(C2H5)3NH]2Cu2(HCOO)5 in a C6H5Cl–C2H5OH solution. Compound 1 was composed of organic donor BEDT‐TTF+0⋅5 in a θ‐phase arrangement and Jahn–Teller distorted (4,4) grid anion sheets [Cu2(HCOO)5 ‐]n with S=1/2. We identified the material as a semiconductor with values of σ 300K=10−1 S cm−1. The anion sheet is a coordination isomer of [Cu2(HCOO)5 ‐]n and, compared with the starting material, shows antiferromagnetic behavior as the well‐known inorganic Cu−O, Co−O square layers for creating inorganic conducting magnets. Long‐range antiferromagnetic ordering was observed at 8.0 K.

A new model for the C-S-H phase formed during the hydration of Portland cements

A model is developed to explain why the C-S-H phase that grows during the hydration of Portland Cements initially requires a high water content, much of which is lost by gentle drying. It is proposed that the rapid growth of C-S-H during the hydration of alite (C3S) in Portland cements initially occurs by adsorption of fully hydrated aqueous calcium cations onto anhydrous anionic basal sheets of a silicate-deficient (dimeric) tobermorite-like composition. Both divalent (Ca2+) and univalent (CaOH+) solvated cations are incorporated to balance the negative charge of the basal sheet, leading to significant structural disorder, explaining the poorly-crystalline nature of the C-S-H formed. Some of the solvation water is lost irreversibly on first drying due to the formation of Si-O-Ca-O-Si bridges, explaining irreversible shrinkage. The initially-formed C-S-H is metastable relative to a form with longer silicate chains, towards which it may slowly evolve with separation of water and CH.

Anionic H-Bonds in the Chlorosulfolipid Surface Bilayer of O. danica the Strength of a Bacterial Cell Wall

Ochromonas danica, a protozoan algal di-flagellate grows in fresh water bogs at pH 4.3. Despite the absence of a wall, its bilayer membrane protects it from osmotic bursting. Lacking P-lipids, its flagellar membrane is made of single-chain (C20) poly-chlorinated 1,14-disulfates with up to 6 chloros. The C1-sulfate on each chain forms an H-bonded dense anionic surface sheet attracting H3O+ (hydronium ions) to the membrane fresh-water surface. Each H3O+ ion can enter the low dielectric and H-bond to the chloros spaced along the chains, due to chloro-electronegativity. The field created by the anionic hydrophobic-C14-sulfate sheet deep in the bilayer attracts the H3O+ ions toward it. The sulfate-H-sulfate H-bonds, or anionic H-bonds (AHbs) are much stronger than those same bonds at the C1-sulfate sheet, because the C1-sheet faces water, which weakens AHbs. Both sulfate sheets require AHbs to strengthen the bilayer but the C14-sulfate sheet is significantly stronger because of its aprotic environment. (Sigala, et al. JACS (2015)137,5730). Like the single-chain bilayers of the chlorosulfolipids, single-chain oleic acid bilayers use a COOH AHb and also have a second binding domain in the low dielectric, a Δ9 double bond. We use it to compare energy measurements. O. danica's surface bilayer also contains unique PUFAs, dominated by arachidonic, linoleic, and linolenic acids, which further strengthen the bilayer.