Hydration Of Complexes Research Articles

Exploring atmospheric nucleation processes: Hydration and fluoroalcoholic complexation of pyruvic acid.

This study examines the intermolecular interactions between small molecules and solvents, with a particular focus on pyruvic acid (PA). PA plays a significant role in biochemistry, astrochemistry, and atmospheric chemistry, particularly in aerosol particle formation. Previous studies on PA have been expanded upon by exploring its hydration and complexation with 2,2,2-trifluoroethanol (TFE). The clusters were generated using a supersonic expansion and characterized by broadband Fourier transform microwave spectroscopy. The structures of the clusters were identified by comparing the experimental results with high-level quantum-chemical computations. Among the possible isomers for the hydrated complex, the Tc-(H2O)2 kinetic complex, where PA exhibits an internal hydrogen bond, was favored over the Tt-(H2O)2 form, predicted to be the most stable conformer. Transitions from both the A and E internal rotation substates were observed exclusively in the dihydrate. The complex with TFE did not exhibit splitting due to the internal rotation of the methyl top. This is attributed to the presence of electronegative fluorine groups in TFE, stabilizing the complex through additional CH⋯F interactions, thereby hindering the internal rotation motion of the methyl top.

Calcium silicate hydrate complex konjac glucomannan-based hydrogel selectively adsorbed phosphate in low alkalinity solution

The selective recovery of phosphate from wastewater can manage nutrients and realize the recycling of phosphorus resources. In this study, a novel konjac glucomannan/pectin/calcium silicate composite hydrogel (KP-CSH) was developed for efficient recovery of phosphate in aqueous solution. The amount of alkali released after the reaction of KP-CSH in a neutral solution was small (the pH of the solution after the reaction was < 9). In a wide initial pH range (3–10), the adsorption capacity of KP-CSH in 50 mg-P/L phosphate solution reached 39∼45 mg-P/g. Besides, even if the pH of the solution after the reaction was less than 8, it could still well adsorb phosphate. The kinetic and isothermal adsorption experiments indicated that the adsorption process of phosphate by KP-CSH was chemical adsorption, and the maximum adsorption capacity was 61.2 mg-P/g. KP-CSH preferentially adsorbed phosphate even in the presence of high concentrations of competitive ions. In the actual biogas slurry, KP-CSH also exhibited the strongest selectivity/affinity for phosphate, and its distribution coefficient (Kd) was significantly higher than that of other co-existing anions and cations. The adsorption mechanism analysis indicated that Ca was the main adsorption site of KP-CSH, and that the adsorption process of target pollutants mainly involved ligand exchange and the intra-sphere complexation. Further plant seed germination and seedling growth experiments suggested that KP-CSH after phosphate recovery did not exert a negative effect on the growth of plant seedlings, and increased the chlorophyll content of seedling leaves. These results demonstrate that KP-CSH is a potential adsorbent for efficient phosphate recovery, which can be used as a slow-release phosphate fertilizer after recovering phosphate.

Orientation of Co2+ and Cu2+ ions introduced L-type zeolite observed with a magnetic field

L-type zeolite with Co2+ and Cu2+ ions in 3d-transition-metal ions were prepared via ion exchange. The suspension containing these zeolite was used for slip-casting under a 12 T magnetic field applied perpendicular to the substrate surface, resulting in an orientation parallel to the c-axis for Co-L and an orientation vertical to the c-axis for Cu-L. The orientation behavior was strongly affected by the magnetocrystalline anisotropy of the L-type zeolite introduced by Co2+ and Cu2+ ions. X-ray absorption fine structure and diffuse-reflectance measurements indicated that the introduced Co2+ and Cu2+ ions formed six-coordinated hydration complexes in the zeolite structure. These hydrated complexes have a distorted octahedral structure. The results suggest that the stable direction of the magnetic moment of the hydration complex at site B of L-type zeolite depends on the strain direction. The Co2+ and Cu2+ hydration complexes have different strain directions, and the difference in orientation is speculated to be due to the different stable directions of the magnetic moment within the zeolite.

Elucidating the role of primary and secondary sphere Zn2+ ligands in the cyanobacterial CO2 uptake complex NDH-14: The essentiality of arginine in zinc coordination and catalysis

Inorganic carbon uptake in cyanobacteria is facilitated by an energetically intensive CO2-concentrating mechanism (CCM). Specialized Type-1 NDH complexes function as a part of this mechanism to couple photosynthetic energy generated by redox reactions of the electron transport chain (ETC) to CO2 hydration. This active site of CO2 hydration incorporates an arginine side chain as a Zn ligand, diverging from the typical histidine and/or cysteine residues found in standard CAs. In this study, we focused on mutating three amino acids in the active site of the constitutively expressed NDH-14 CO2 hydration complex in Synechococcus sp. PCC7942: CupB-R91, which acts as a zinc ligand, and CupB-E95 and CupB-H89, both of which closely interact with the arginine ligand. These mutations aimed to explore how they affect the unusual metal ligation by CupB-R91 and potentially influence the unusual catalytic process. The most severe defects in activity among the targeted residues are due to a substitution of CupB-R91 and the ionically interacting E95 since both proved essential for the structural stability of the CupB protein. On the other hand, CupB-H89 mutations show a range of catalytic phenotypes indicating a role of this residue in the catalytic mechanism of CO2-hydration, but no evidence was obtained for aberrant carbonic anhydrase activity that would have indicated uncoupling of the CO2-hydration activity from proton pumping. The results are discussed in terms of possible alternative CO2 hydration mechanisms.

Three-Dimensional Amplitude versus Offset Analysis for Gas Hydrate Identification at Woolsey Mound: Gulf of Mexico

The Gulf of Mexico Hydrates Research Consortium selected the Mississippi Canyon Lease Block 118 (MC118) as a multi-sensor, multi-discipline seafloor observatory for gas hydrate research with geochemical, geophysical, and biological methods. Woolsey Mound is a one-kilometer diameter hydrate complex where gas hydrates outcrop at the sea floor. The hydrate mound is connected to an underlying salt diapir through a network of shallow crestal faults. This research aims to identify the base of the hydrate stability zone without regionally extensive bottom simulating reflectors (BSRs). This study analyzes two collocated 3D seismic datasets collected four years apart. To identify the base of the hydrate stability zone in the absence of BSRs, shallow discontinuous bright spots were targeted. These bright spots may mark the base of the hydrate stability field in the study area. These bright spots are hypothesized to produce an amplitude versus offset (AVO) response due to the trapping of free gas beneath the gas hydrate. AVO analyses were conducted on pre-stacked 3D volume and decreasing amplitude values with an increasing offset, i.e., Class 4 AVO anomalies were observed. A comparison of a time-lapse analysis and the AVO analysis was conducted to investigate the changes in the strength of the AVO curve over time. The changes in the strength are correlated with the decrease in hydrate concentrations over time.

Hydrogen Bonding and Molecular Geometry in Isolated Hydrates of 2-Ethylthiazole Characterised by Microwave Spectroscopy.

Broadband microwave spectra of the isolated 2-ethylthiazole molecule, and complexes of 2-ethylthiazole⋅⋅⋅H2O and 2-ethylthiazole⋅⋅⋅(H2O)2 have been recorded by probing a gaseous sample containing low concentrations of 2-ethylthiazole and water within a carrier gas undergoing supersonic expansion. The identified conformer of the isolated 2-ethylthiazole molecule and the 2-ethylthiazole sub-unit within each of 2-ethylthiazole⋅⋅⋅H2O and 2-ethylthiazole⋅⋅⋅(H2O)2 have C1 symmetry. The angle that defines rotation of the ethyl group relative to the plane of the thiazole ring, ∠(S-C2-C6-C7), is -98.6(10)° within the isolated 2-ethylthiazole molecule. Analysis of molecular geometries and non-covalent interactions reveals each hydrate complex contains a non-linear primary, N⋅⋅⋅Hb-O, hydrogen bond between an O-H of H2O and the nitrogen atom while the O atom of the water molecule(s) interacts weakly with the ethyl group. The ∠(Hb⋅⋅⋅N-C2) parameter, which defines the position of the H2O molecule relative to the thiazole ring, is found to be significantly greater for 2-ethylthiazole⋅⋅⋅H2O than for thiazole⋅⋅⋅H2O. The distance between the O atoms is determined to be 2.894(21) Å within the dihydrate complex which is shorter than observed within the isolated water dimer. The primary hydrogen bond within 2-ethylthiazole⋅⋅⋅(H2O)2 is shorter and stronger than that in 2-ethylthiazole⋅⋅⋅H2O as a result of cooperative hydrogen bonding effects.

Abnormal swelling in water of carboxylic ion exchanger in the forms of ammonium and tetraethylammonium ions

A fibrous carboxylic ion exchanger, obtained by post-radiation grafting of polyacrylic acid to polypropylene fiber, in the ammonium form has an abnormally low swelling in water, corresponding to 10 moles of water per equivalent, and in the form of tetraethylammonium ion (NEt4+) – abnormally high 25 moles of water/eq. Considering that NH4+ is a hydrophilic particle and NEt4+ is hydrophobic, this fact seems paradoxical. The article attempts to explain this phenomenon using molecular modeling (ab initio calculations of the structure of hydrate complexes in the HF MO LCAO approximation with the 6-31G basis set) in combination with the Predominant Hydrates Model, which made it possible to calculate the theoretical water sorption isotherms of the ion exchanger and compare them with experimental data. The abnormally low swelling of the ion exchanger in the NH4+-form is caused by the formation of a strong bond between the carboxylate anion and ammonium with a significant degree of covalence due to the superposition of the Coulomb interaction of the ions and the formation of a hydrogen bond between them. The abnormally high swelling of NEt4+-forms is caused by the absence of a strong interaction between cations and carboxylate groups due to the impossibility of their convergence due to steric reasons. The high swelling of the ion exchanger is caused by the absence of blocking of the hydrophilic carboxylate groups of the ion exchanger by hydrogen bonds with the cation. The ion exchanger matrix does not contain a cross agent and does not create a spatial restriction for the high swelling of the ion exchanger.

Ions-Induced Alginate Gelation According to Elemental Analysis and a Combinatorial Approach.

This study considers the potential of elemental analysis of polysaccharide ionotropic gels in elucidating the junction zones for different divalent cations. The developed algorithm ensures the correct separation of contributions from physically adsorbed and structure-forming ionic compounds, with the obtained results scaled to alginate C12 block. Possible versions of chain association into dimers and their subsequent integration into flat junction zones were analyzed within the framework of the "egg-box" model. The application of combinatorial analysis made it possible to derive theoretical relations to find the probability of various types of egg-box cell occurrences for alginate chains with arbitrary monomeric units ratio μ = M/G, which makes it possible to compare experimental data for alginates of different origins. Based on literature data and obtained chemical formulas, the possible correspondence of concrete biopolymer cells to those most preferable for filling by alkaline earth cations was established. The identified features of elemental composition suggest the formation of composite hydrated complexes with the participation of transition metal cations. The possibility of quantitatively assessing ordered secondary structures formed due to the physical sorption of ions and molecules from environment, correlating with the sorption capabilities of Me2+ alginate, was established.

Theoretical investigation of outer-sphere adsorption of hydrated yttrium ion on the basal surfaces of kaolinite: A density functional study

Ion-adsorption deposits (IADs) are important types of REE deposits. Previous studies have found that, in IAD, REE3+ adsorb on the surface of clay minerals in the form of multi-coordinated hydrated complexes, [REE(H2O)8/9]3+, forming exchangeable outer-sphere adsorption complex. Actually, there are two types of basal surfaces in clay minerals, the (001) surface and the (00−1) surface, and it is not clear whether there are differences in the adsorptions on these two types. Additionally, the electron transfer mechanism in the adsorption structures cannot be revealed. To address these issues, we employ first-principles calculations based on density functional study to simulate the outer-sphere adsorption structures of representative Y3+ ion on the two types of basal surface of kaolinite. The study reveals that both the (001) surface and the (00–1) surface can serve as adsorption surfaces, but the (00–1) surface forms more stable adsorption structures with adsorbate-[Y(H2O)8]3+ due to the absence of hydroxyl group repulsion effects. The adsorption process involves electron transfer from the kaolinite basal surface to the adsorbate, forming hydrogen bonds. The primary orbital interaction in this process is between the O-2p orbitals of the adsorbate and the surface O-2p orbitals. This work contributes to a quantum-level understanding of the nature of ion adsorption in ion-adsorption deposit.

Volume properties of bioactive glycoluril-derivatives of gamma-aminobutyric acid in aqueous solutions between 278.15 and 318.15 K

The densities of aqueous solutions of 4-(3,7-dioxo-2,4,6,8-tetraazabicyclo[3.3.0]oct-2-yl)butanoic acid or glycoluril-butyric acid (GUBA) and its N,N-dimethyl-substituted analogue (DMGUBA), with molality ranged from m = (0.004–0.06) mol·kg−1, were measured at T = (278.15, 288.15, 298.15, 308.15, and 318.15) K and p ≈ 0.1 MPa. The uncertainty in density measurements was estimated to be 3 × 10−5 g cm−3. The apparent and standard (at infinite dilution) molar volumes, V∅,2 and V2°, as we as the standard molar expansibilities, Ep,2°, of GUBA and DMGUBA were calculated. The volume-hydration effects, ΔtrV2°, induced by the conversion of glycoluril (GU) and N,N-dimethylglycoluril (DMGU) into the derivatives of γ-aminobutyric acid (GUBA and DMGUBA) point to squeezing of the structure of the non-methylated “hydration complex” and its loosening at N-methylation of one of glycolurilic rings of the solute under the influence of increasing temperature. It is inferred that the decisive role in the process of hydration of both GUBA and DMGUBA belongs to hydrophilic effects associated with the interactions of proton-donor/acceptor moieties of solution components as well as protons and carboxyl ions formed during the solute partial dissociation under the influence of an aqueous medium (electrostriction effect).

Microwave-assisted rapid synthesize of cadmium–thallium mixed fluoride hydrate complex and its physiochemical properties

Herein we report a facile and rapid, cost-effective microwave-assisted synthesis of mixed cadmium-thallium fluoride hydrate compound using a homemade vessel with a special protective outer container. The physicochemical properties of the prepared compound were investigated by several characterization techniques. Single crystal X-ray diffraction measurement was performed to investigate the crystal structure of the prepared compound. The XEOL intensity shows a good linear response as a function of the delivered X-ray dose, which indicates that this material can be highly desirable for radiation detection applications. The fitting of scintillation decay kinetic from a241Am α− radiation source, shows the fastest decay time constant of 40 ns (16%) with medium and slow components of 380 ns (72%) and 1.5 μs (12%) at room temperature. The pulse height spectrum shows the photopeak of α− particles produced by the 241Am radiation source at 5.48 MeV.

Synthesis, crystal structure, DFT studies and catalytic activity of an N-(2,2-dimethyl-1,3-dioxolane-4yl-methyl)benzimidazole ruthenium(II) hydrate complex

In this study, the new N-coordinated benzimidazole ruthenium(II) complex was synthesized. The complex was fully characterized by FT-IR, 1H and 13C NMR spectroscopic methods. The molecular structure of the complex has been verified by X-ray crystallography. Besides, theoretical structure and spectroscopic data were obtained using density functional theory (DFT/HSEH1PBE) method with the cc-pVDZ basis set for C, H, N, O and Cl atoms, and the LANL2DZ basis set for the metal atom, and compared with the experimental data. This complex has also been tested for the N-alkylation of aromatic amines with arylmethyl alcohols under neat conditions in the presence of KOBut.

Structural Features and Thermal Behavior of Ion-Exchanged Clinoptilolite from Beli Plast Deposit (Bulgaria)

The structural features and the thermal behavior of natural, Na-, Ca-, K-, Mg-, and Cd-exchanged clinoptilolite from the Beli Plast deposit (Bulgaria) were studied. Purified clinoptilolite sample was preliminary prepared and ion-exchanged at 100 °C for six days. DSC-TG analyses were performed for all studied forms. The effects in the DSC curves show differences with temperature due to release of weakly bound H2O molecules and strongly bound ones. The endotherm minima temperatures were between 78 and 115 °C decreasing in the sequence K- &lt; Na- &lt; Natural- &lt; Ca- ≤ Mg- &lt; Cd-clinoptilolite. The hydrate complexes around the exchanged cations also influenced the DSC curves. The cation-coordinating H2O molecules and the non-coordinating ones were determined by XRD structural refinement for all exchanged samples. The H2O molecules of the cation–hydrate complexes are released at higher temperatures than weakly bound ones and affected the DSC curves differently. The structural adjustments made by the Rietveld method, as well as the applied EDS analyzes for the chemical composition of the samples, allowed us to correlate these data to the thermal characteristics of the studied clinoptilolite samples.

Microhydrated 3-Methyl-3-oxetanemethanol: Evolution of the Hydrogen-Bonding Network from Chains to Cubes.

Broadband rotational spectroscopy is used to investigate the geometries of 3-methyl-3-oxetanemethanol and its complexes with up to six water molecules, which are produced in supersonic jets. The main low-energy isomers of these clusters are unambiguously identified in the spectra with the support of quantum-chemical calculations. The conformation of the 3-methyl-3-oxetanemethanol geometry is found to be influenced by the microsolvation effects. The hydrogen-bond arrangements in the hydrate complexes, which are governed by the water-water and water-solute interactions, exhibit characteristic configurations with increasing number of water molecules and resemble the main isomers of the corresponding pure water clusters. Evolution of the hydrogen-bonding structures from one-dimensional chains to two-dimensional rings and further to multicyclic three-dimensional networks is observed, which provides information about the build-up process.

Microhydrated 3‐Methyl‐3‐oxetanemethanol: Evolution of the Hydrogen‐Bonding Network from Chains to Cubes

AbstractBroadband rotational spectroscopy is used to investigate the geometries of 3‐methyl‐3‐oxetanemethanol and its complexes with up to six water molecules, which are produced in supersonic jets. The main low‐energy isomers of these clusters are unambiguously identified in the spectra with the support of quantum‐chemical calculations. The conformation of the 3‐methyl‐3‐oxetanemethanol geometry is found to be influenced by the microsolvation effects. The hydrogen‐bond arrangements in the hydrate complexes, which are governed by the water‐water and water‐solute interactions, exhibit characteristic configurations with increasing number of water molecules and resemble the main isomers of the corresponding pure water clusters. Evolution of the hydrogen‐bonding structures from one‐dimensional chains to two‐dimensional rings and further to multicyclic three‐dimensional networks is observed, which provides information about the build‐up process.

Coumarin 337 in aqueous solution: interplay between excitation and hydration

Excitation of the C337, highly fluorescent dye in an aqueous solution was studied by the TD-DFT. Through the B3PW91/6-311++G(d, p)/IEFPCM theory level, we obtained the C337 vibronic absorption spectrum which exactly reproduces the experimental maximum. Significant differences are shown between the results of calculating the transition energies using the models of vertical and vibronic transitions. Upon excitation, the main shift of the electron density occurs from C10 to C4 neighboring atom. Thus, large-scale ICT not occur. The effect of excitation on the vibrational spectra of C337 was analyzed. A single C337 molecule and its five different hydration complexes with strongly bound water molecules have been analyzed. Various hydrate complexes of the dye have been studied, and the effect of hydration on its excitation vibrational properties has been elucidated. It was taken into account that a water molecule can attach to the nitrogen atom N1 ("A" type) and the C=O carbonyl ("B" type), and cyano C≡N ("C" type) groups of the dye.

Von lokalen kovalenten Bindungen zu langreichweitigen elektrischen Wechselwirkungen der Protonenhydratation

AbstractScheinbar einfache und doch überraschend schwierig ist die Untersuchung überschüssiger Protonen in Wasser, die ein komplexes Quantenobjekt mit starken Wechselwirkungen zum ausgedehnten und sich dynamischen ändernden Wasserstoffbrücken‐Netzwerk der Flüssigkeit darstellen. Die auftretende Protonenhydratation spielt eine entscheidende Rolle im Energietransport von Brennstoffzellen und bei der Signalübertragung in Transmembranproteinen. Während Geometrie und Stöchiometrie bereits umfangreich in Experimenten und in der Theorie adressiert worden sind, ist die elektronische Struktur dieser spezifischen hydratisierten Protonenkomplexe bisher Verborgenen geblieben. In dieser Studie zeigen wir, Schicht für Schicht, wie der Einsatz neuer Flachstrahltechnologie für akkurate röntgenspektroskopische Messungen in Kombination mit Infrarot‐Spektralanalyse sowie Berechnungen es uns ermöglicht, orbitalspezifische spektrale Signale zu finden, die es erlauben zwei Haupteffekte in der elektronsichen Struktur zu unterscheiden: Lokale Orbitalwechselwirkungen bestimmen kovalente Bindungen zwischen dem Proton und den benachbarten Wassermolekülen, während Verschiebungen der Orbitalenergien ein Maß für die Stärke des langreichweitigen elektrischen Feldes des Protons sind.

From Local Covalent Bonding to Extended Electric Field Interactions in Proton Hydration.

Seemingly simple yet surprisingly difficult to probe, excess protons in water constitute complex quantum objects with strong interactions with the extended and dynamically changing hydrogen-bonding network of the liquid. Proton hydration plays pivotal roles in energy transport in hydrogen fuel cells and signal transduction in transmembrane proteins. While geometries and stoichiometry have been widely addressed in both experiment and theory, the electronic structure of these specific hydrated proton complexes has remained elusive. Here we show, layer by layer, how utilizing novel flatjet technology for accurate x-ray spectroscopic measurements and combining infrared spectral analysis and calculations, we find orbital-specific markers that distinguish two main electronic-structure effects: Local orbital interactions determine covalent bonding between the proton and neigbouring water molecules, while orbital-energy shifts measure the strength of the extended electric field of the proton.

Peculiar points of aqueous solutions of mono-hydrogen alcohols

The work is devoted to the detailed study of the peculiar points in aqueous solutions of mono-hydrogen alcohols. The main attention is focused on water-methanol and water–ethanol solutions for which there are numerous experimental data. It is taken into account that H-bond interaction between alcohol and water molecules stimulates the formation of hydration complexes or elementary clusters, stable for temperatures: T<42°C. A solution at the peculiar point has a cell-like structure, where every cell consists of one alcohol molecule surrounded by water molecules forming mono-molecular layer. The volume and dissolution heat per cluster are determined. It is shown that the peculiar point arises at the concentration leading to the full filling of a solution by elementary clusters. The instability of elementary clusters near the peculiar point is considered. The possible existence of peculiar point of another type is discussed.

(Diaqua)hexakis(4,4,4-trifluoro-1-(1-methyl-1H-pyrazol-4-yl)butane-1,3-dionato-κ2O,O’)(μ-(1,4-dioxane))digadolinium (III), Solvate with Two Molecules of 1,4-Dioxane

A binuclear gadolinium (III) complex was obtained through the interaction of GdCl3·6H2O, 4,4,4-trifluoro-1-(1-methyl-1H-pyrazol-4-yl)butane-1,3-dione and NaOH in MeOH solution. Molar ration of reagents equal to 1:3:3 was used. Upon recrystallization of wet 1,4-dioxane, an intermediate hydrated complex formed stable crystalline solvate with the composition [(Gd2(L)3(H2O))2(C4H8O2)]•2(C4H8O2). The structured of complex was established by single crystal XRD experiment. Furthermore, some photophysical properties of the complex were measured. Thus, the energy of the first exited triplet state for the diketonate ligand was found to be 22400 cm−1, which makes 4,4,4-trifluoro-1-(1-methyl-1H-pyrazol-4-yl)butane-1,3-dione a promising ligand for the preparation of highly luminescent Eu3+ and Sm3+ complexes.