Hydrogen-bonded Network Structure Research Articles

The role of hydrogen bonds in anomalies of dielectric properties of Diglycine Nitrate and Triglycine Tellurate

ABSTRACTDielectric spectroscopy measurements have been carried out at 10−1−107 Hz in the temperature range between 0 and 100°C on single crystals from the Triglycine Sulphate family - Triglycine Tellurate and Diglycine Nitrate, which contain 2.6÷2.9 Å hydrogen bonds. Temperature and frequency dependencies of complex dielectric permittivity, conductivity, electric modulus and calculated parameters of relaxation time spectra demonstrate anomalous behaviour at temperatures close to those of anomalies of physical properties of water. The results are interpreted from the point of view that the structure and dynamic properties of hydrogen bond network in water and in studied crystals are similar.

Long-Range Interactions Restrict Water Transport in Pyrophyllite Interlayers.

Water diffusion within smectite clay interlayers is reduced by confinement and hence is highly determined by the interlayer spacings that are adopted during swelling. However, a molecular understanding of the short- and long-range forces governing interlayer water structure and dynamics is lacking. Using molecular dynamics simulations of water intercalated between pyrophyllite (smectite prototype) layers we provide a detailed picture of the variation of interlayered water mobility accompanying smectite expansion. Subtle changes in hydrogen bond network structure cause significant changes in water mobility that is greater for stable hydration states and reduced for intermediate separations. By studying pyrophyllite with and without external water we reveal that long-range electrostatic forces apply a restraining effect upon interlayer water mobility. Our findings are relevant for broad range of confining nanostructures with walls thin enough to permit long-range interactions that could affect the mobility of confined solvent molecules and solute species.

Vibrational Spectroscopy and Dynamics of Water.

We present an overview of recent static and time-resolved vibrational spectroscopic studies of liquid water from ambient conditions to the supercooled state, as well as of crystalline and amorphous ice forms. The structure and dynamics of the complex hydrogen-bond network formed by water molecules in the bulk and interphases are discussed, as well as the dissipation mechanism of vibrational energy throughout this network. A broad range of water investigations are addressed, from conventional infrared and Raman spectroscopy to femtosecond pump-probe, photon-echo, optical Kerr effect, sum-frequency generation, and two-dimensional infrared spectroscopic studies. Additionally, we discuss novel approaches, such as two-dimensional sum-frequency generation, three-dimensional infrared, and two-dimensional Raman terahertz spectroscopy. By comparison of the complementary aspects probed by various linear and nonlinear spectroscopic techniques, a coherent picture of water dynamics and energetics emerges. Furthermore, we outline future perspectives of vibrational spectroscopy for water researches.

A facile approach for preparation of underwater superoleophobicity cellulose/chitosan composite aerogel for oil/water separation

We fabricate cellulose/chitosan (CE/CS) aerogel with stable superhydrophilic (θ ≈ 0°) and underwater superoleophobic (θoil > 150°) through a simple way. During the process of preparation of CE/CS aerogel, chitosan will self-assemble into number micron diameter particles on the surface of aerogel. Furthermore, the hydrogen bonding network structure of cellulose was destroyed and more hydrophilic groups (–OH) were exposed. Rough surface and hydrophilicity make CE/CS aerogel have a property of underwater superoleophobicity. CE/CS aerogel shows underwater superoleophobicity to different oils, and it still have stable superoleophobicity in corrosive solution. The important thing is that CE/CS aerogel can separate free oil/water mixture and surfactant-stabilized emulsions under gravity effectively. The sample is green, low cost, and environmental friendly, which is a promising candidate to be used in oil/water separation.

Water Hydrogen-Bonding Network Structure and Dynamics at Phospholipid Multibilayer Surface: Femtosecond Mid-IR Pump-Probe Spectroscopy.

The water hydrogen-bonding network at a lipid bilayer surface is crucial to understanding membrane structures and its functional activities. With a phospholipid multibilayer mimicking a biological membrane, we study the temperature dependence of water hydrogen-bonding structure, distribution, and dynamics at a lipid multibilayer surface using femtosecond mid-IR pump-probe spectroscopy. We observe two distinguished vibrational lifetime components. The fast component (0.6 ps) is associated with water interacting with a phosphate part, whereas the slow component (1.9 ps) is with bulk-like choline-associated water. With increasing temperature, the vibrational lifetime of phosphate-associated water remains constant though its relative fraction dramatically increases. The OD stretch vibrational lifetime of choline-bound water slows down in a sigmoidal fashion with respect to temperature, indicating a noticeable change of the water environment upon the phase transition. The water structure and dynamics are thus shown to be in quantitative correlation with the structural change of liquid multibilayer upon the gel-to-liquid crystal phase transition.

Construction and Conversion of a Self-assembled Hydrogen-bonding Network Structure Composed of S-Bridged Trinuclear Nickel(II) Units with Chiral Multidentate Ligands

Treatment of dicyandiamide, D-penicillamine (D-H2pen), and NiII produced a NiII3 trinuclear complex, [Ni3(D-bgpen)2(D-pen)] (1), as a kinetic product, which was converted to a NiII2 dinuclear complex, [Ni2(D-bgpen)2] (2), as a thermodynamic product by soaking the crystals of 1 in heated water. In both 1 and 2, self-assembled hydrogen-bonding 3D network structures are constructed through double hydrogen bonds between the biguanide moiety as a hydrogen-bonding donor and the carboxylate group as an acceptor.

(Acetato-κO){2-[(2-aminoethyl-κN)disulfanyl]ethanaminium}dichloridozinc(II)

In the title compound, [Zn(C4H13N2S2)(CH3COO)Cl2], the ZnIIion is in a tetrahedral coordination geometry, coordinated by one acetate, two chloride and one 2-[(2-aminoethyl)disulfanyl]ethanaminium ligand, with a Zn—O distance of 1.977 (3) Å, a Zn—N distance of 2.015 (3) Å and Zn—Cl distances of 2.2673 (18) and 2.2688 (15) Å. In the crystal, molecules are self-assembled by N—H...Cl hydrogen bonds, leading to a one-dimensional chain structure. The chains interact with each other through N—H...O, N—H...S, C—H...Cl and C—H...S hydrogen bonding, completing a three-dimensional hydrogen-bonding network structure.

Supramolecular homochiral helicity and zigzag hydrogen bonded chains in 1,2,4-triazole derived aminoester and aminoacid

Two new triazole ligands were synthesized, and their crystal structure analysis revealed unprecedented homochiral helical and 2D hydrogen bonded network structures.

Energetics of the Proton Transfer Pathway for Tyrosine D in Photosystem II

The proton transfer pathway for redox active tyrosine D (TyrD) in photosystem II is a hydrogen-bond network that involves D2-Arg180 and a series of water molecules. Using quantum mechanical/molecular mechanical calculations, the detailed properties of the energetics and structural geometries were investigated. The potential-energy profile of all hydrogen bonds along the proton transfer pathway indicates that the overall proton transfer from TyrD is energetically downhill. D2-Arg180 plays a key role in the proton transfer pathway, providing a driving force for proton transfer, maintaining the hydrogen-bond network structure, stabilising P680•+, and thus deprotonating TyrD-OH to TyrD-O•. A hydrophobic environment near TyrD enhances the electrostatic interactions between TyrD and redox active groups, e.g. P680 and the catalytic Mn4CaO5 cluster: the redox states of those groups are linked with the protonation state of TyrD, i.e. release of the proton from TyrD. Thus, the proton transfer pathway from TyrD may ultimately contribute to the conversion of S0 into S1 in the dark in order to stabilise the Mn4CaO5 cluster when the photocycle is interrupted in S0.

Propensity of Self-Assembled Leucine-Lysine Diblock Copolymeric α-Helical Peptides To Remain in Parallel and Antiparallel Alignments in Water.

Molecular dynamics simulation study of α-helical diblock copolypeptides preassembled in parallel and antiparallel alignments in water are presented. The assembled peptide lamellar structures were not disrupted even after performing three-step simulation protocols. Primarily hydrogen bonds between peptide are responsible for the stability. The analysis of the trajectory also suggests that water plays a significant role in favoring self-assembly. We have detected continuous hydrogen bonded network structure, which is further responsible for the stability of the lamellar structures. We have performed a detailed analysis of the hydrogen bonded network structure and its length. Further, free energy calculations revealed that the degree of stability for both lamellae are similar. The present study provides structural insight into the stability of self-assembled structures of block copolypeptides.

Ion aggregation in high salt solutions. III. Computational vibrational spectroscopy of HDO in aqueous salt solutions.

The vibrational frequency, frequency fluctuation dynamics, and transition dipole moment of the O-D stretch mode of HDO molecule in aqueous solutions are strongly dependent on its local electrostatic environment and hydrogen-bond network structure. Therefore, the time-resolved vibrational spectroscopy the O-D stretch mode has been particularly used to investigate specific ion effects on water structure. Despite prolonged efforts to understand the interplay of O-D vibrational dynamics with local water hydrogen-bond network and ion aggregate structures in high salt solutions, still there exists a gap between theory and experiment due to a lack of quantitative model for accurately describing O-D stretch frequency in high salt solutions. To fill this gap, we have performed numerical simulations of Raman scattering and IR absorption spectra of the O-D stretch mode of HDO in highly concentrated NaCl and KSCN solutions and compared them with experimental results. Carrying out extensive quantum chemistry calculations on not only water clusters but also ion-water clusters, we first developed a distributed vibrational solvatochromic charge model for the O-D stretch mode in aqueous salt solutions. Furthermore, the non-Condon effect on the vibrational transition dipole moment of the O-D stretch mode was fully taken into consideration with the charge response kernel that is non-local polarizability density. From the fluctuating O-D stretch mode frequencies and transition dipole vectors obtained from the molecular dynamics simulations, the O-D stretch Raman scattering and IR absorption spectra of HDO in salt solutions could be calculated. The polarization effect on the transition dipole vector of the O-D stretch mode is shown to be important and the asymmetric line shapes of the O-D stretch Raman scattering and IR absorption spectra of HDO especially in highly concentrated NaCl and KSCN solutions are in quantitative agreement with experimental results. We anticipate that this computational approach will be of critical use in interpreting linear and nonlinear vibrational spectroscopies of HDO molecule that is considered as an excellent local probe for monitoring local electrostatic and hydrogen-bonding environment in not just salt but also other confined and crowded solutions.

Hydrogen-bonded 2D network structure and abrupt spin transition with thermal hysteresis of iron(III) complexes [FeIII(Him)2(3-MeOsalen)]·H2O·EtOH·X (Him = imidazole, 3-MeOsalen = N,N′-bis(3-methoxysalicylidene)ethylenediaminato, and X = PF6, AsF6, SbF6)

Spin crossover (SCO) iron(III) complexes exhibiting thermal hysteresis, [FeIII(Him)2(3-MeOsalen)]·H2O·EtOH·X (Him=imidazole, 3-MeOsalen=N,N′-bis(3-methoxysalicylidene)ethylenediaminato, and X=PF6, AsF6, SbF6), were synthesized in ethanol. The FeIII ion has an octahedral coordination geometry with N2O2 donor atoms of the planar tetradentate ligand (3-MeOsalen) and two nitrogen atoms of two imidazoles at the axial positions. Through H2O and EtOH the complex-cations are assembled into a hydrogen-bonded 2D network structure and the anion X is accommodated in the void of the 2D network. The temperature dependences of the magnetic susceptibilities revealed an abrupt and two-step spin transition with thermal hysteresis for the PF6 and AsF6 salts.

Hydrogen-bonded ring closing and opening of protonated methanol clusters H(+)(CH3OH)(n) (n = 4-8) with the inert gas tagging.

The preferential hydrogen bond (H-bond) structures of protonated methanol clusters, H(+)(MeOH)n, in the size range of n = 4-8, were studied by size-selective infrared (IR) spectroscopy in conjunction with density functional theory calculations. The IR spectra of bare clusters were compared with those with the inert gas tagging by Ar, Ne, and N2, and remarkable changes in the isomer distribution with the tagging were found for clusters with n≥ 5. The temperature dependence of the isomer distribution of the clusters was calculated by the quantum harmonic superposition approach. The observed spectral changes with the tagging were well interpreted by the fall of the cluster temperature with the tagging, which causes the transfer of the isomer distribution from the open and flexible H-bond network types to the closed and rigid ones. Anomalous isomer distribution with the tagging, which has been recently found for protonated water clusters, was also found for H(+)(MeOH)5. The origin of the anomaly was examined by the experiments on its carrier gas dependence.

Ion aggregation in high salt solutions. II. Spectral graph analysis of water hydrogen-bonding network and ion aggregate structures.

Graph theory in mathematics and computer science is the study of graphs that are structures with pairwise connections between any objects. Here, the spectral graph theory and molecular dynamics simulation method are used to describe both morphological variation of ion aggregates in high salt solutions and ion effects on water hydrogen-bonding network structure. From the characteristic value analysis of the adjacency matrices that are graph theoretical representations of ion clusters, ion networks, and water H-bond structures, we obtained the ensemble average eigenvalue spectra revealing intricate connectivity and topology of ion aggregate structure that can be classified as either ion cluster or ion network. We further show that there is an isospectral relationship between the eigenvalue spectra of ion networks in high KSCN solutions and those of water H-bonding networks. This reveals the isomorphic relationship between water H-bond structure and ion-ion network structure in KSCN solution. On the other hand, the ion clusters formed in high NaCl solutions are shown to be graph-theoretically and morphologically different from the ion network structures in KSCN solutions. These observations support the bifurcation hypothesis on large ion aggregate growth mechanism via either ion cluster or ion network formation. We thus anticipate that the present spectral graph analyses of ion aggregate structures and their effects on water H-bonding network structures in high salt solutions can provide important information on the specific ion effects on water structures and possibly protein stability resulting from protein-water interactions.

Spectroscopic tracking of Schiff base compounds' hydrogen bonding reorganization associated with solid-to-solid phase transition.

A series of 2,6-dihydroxynaphthalene-1-methylidene alkylamines whose alkyl chain lengths ranged from 9 to 12 was spectroscopically examined. Transmission ultraviolet-visible absorption microspectroscopy revealed that the spectra of solid thin-films of the crystalline samples showed two distinct profiles depending on polymorphs as well as on alkyl chain length. We concluded that these spectral changes occurred not because of conventional intramolecular proton transfer but because of the molecules' interactions with an external proton source, that is, the intermolecular proton transfer. The spectral changes were accompanied by changes in the intermolecular hydrogen bonding network. When a crystal of a sample compound was heated, its spectrum changed dramatically before the crystal underwent a solid-to-solid phase transition to another polymorph. We concluded that these spectral changes indicated strengthening of intermolecular hydrogen bonding or intermolecular proton transfer, which would have triggered a drastic change in the hydrogen bonding network structure.

Structure and energetics of hydrogen-bonded networks of methanol on close packed transition metal surfaces.

Methanol is a versatile chemical feedstock, fuel source, and energy storage material. Many reactions involving methanol are catalyzed by transition metal surfaces, on which hydrogen-bonded methanol overlayers form. As with water, the structure of these overlayers is expected to depend on a delicate balance of hydrogen bonding and adsorbate-substrate bonding. In contrast to water, however, relatively little is known about the structures methanol overlayers form and how these vary from one substrate to another. To address this issue, herein we analyze the hydrogen bonded networks that methanol forms as a function of coverage on three catalytically important surfaces, Au(111), Cu(111), and Pt(111), using a combination of scanning tunneling microscopy and density functional theory. We investigate the effect of intermolecular interactions, surface coverage, and adsorption energies on molecular assembly and compare the results to more widely studied water networks on the same surfaces. Two main factors are shown to direct the structure of methanol on the surfaces studied: the surface coverage and the competition between the methanol-methanol and methanol-surface interactions. Additionally, we report a new chiral form of buckled hexamer formed by surface bound methanol that maximizes the interactions between methanol monomers by sacrificing interactions with the surface. These results serve as a direct comparison of interaction strength, assembly, and chirality of methanol networks on Au(111), Cu(111), and Pt(111) which are catalytically relevant for methanol oxidation, steam reforming, and direct methanol fuel cells.

Synthesis, Three-Dimensional Network Structure, Weak Interactions, and Magnetic Properties of Bis(quinolinium) Tetrachlorocobaltate(II) Dihydrate

A new tetrachlorocobalt(II) salt, [QlH]2[CoCl4]·2H2O(1) ([QlH]+ = quinolinium), has been prepared and characterized by elemental analysis, IR, UV-Vis, ESI-MS, single-crystal X-ray diffraction, and magnetic susceptibility. Compound 1 crystallizes in the monoclinic space group C2/c with cell dimensions a = 11.848(2) Å, b = 10.069(1) Å, c = 18.494(2) Å, β = 101.35(1) Å, V = 2163.3(4) Å3, Z = 4. The unit cell contains two [QlH]+ cations, one [CoCl4]2– anion and two water molecules. The [QlH]+ cations stack and form a 1D column through p···π and π···π interactions. The water molecules are linked to the anions through O-H···Cl hydrogen bonds to form two-dimensional molecular networks. The cations and [CoCl4]2– anions are linked through N-H···O and C-H···O hydrogen bonds and give further rise to a 3D hydrogen-bonding network structure. Magnetic susceptibility measurement in the temperature range 2–300 K shows that 1 exhibits a weak antiferromagnetic coupling behavior with θ = –2.90 K.

Isomorphous free-base, Ni(ii)- and Cu(ii)-5,10,15,20-tetra(4-hydroxyphenyl)porphyrin nitrobenzene hexasolvates with tetragonal 3D hydrogen-bonded network structures

The crystal structures of 5,10,15,20-tetra(4-hydroxyphenyl)-21,23H-porphyrin nitrobenzene hexasolvate (1), 5,10,15,20-tetra(4-hydroxyphenyl)porphyrinatonickel(ii) and -copper(ii)nitrobenzene hexasolvates (2and3) are described.

Picosecond Pulse Radiolysis Study of Dynamics of Solvation of Electron and Fluorenone Anion in Primary Alcohols

We have studied the dynamics of solvation of electron injected directly into primary alcohols as well as that of fluorenone anion using pulse radiolysis technique with the time resolution of about 15 ps. Unlike in the previous reports, we observe nonexponential dynamics of both electron and anion solvation. While the ultrafast component, τ1 (<15 ps) representing the inertial time scale of the dynamics is faster than the time resolution of the spectrometer, the slower component, τ2, has been assigned to the translational motion leading to structural changes of the hydrogen bonding network of the solvent in the inner solvation cell or alcohol cluster. τ2 agrees well with the electron solvation times reported by the earlier authors. τ3 is associated with the restructuring of the hydrogen bond network structure of the solvent in the region outside the solvation cell. Nonexponential solvation dynamics of the fluorenone anion has been described well by a two-component process. The most important observation in this work is that the lifetime of the shorter component, τ1, determined in four alcoholic solvents, is much longer than the electron solvation time in the corresponding solvents determined in this work or anion solvation time reported earlier. The lifetime of this component is nearly comparable with the average dipolar solvation time but shorter than the longitudinal relaxation time of the solvent. In the case of anion, τ1 has been assigned to the restructuring of the first solvation shell by breakage of solvent hydrogen bonds of the fluorenone molecule and formation of hydrogen bonds with the anion. In this case, too, the longer component, τ2, with the lifetime of a few nanoseconds, has been assigned to reorganization of hydrogen bonds in the solvent hydrogen bond network structure.

Experimental and Computational Studies on the 1:1 Complex of Anthranilic Acid with P-Toluenesulfonic Acid

The proton-transfer compound (3) was synthesized in good yields by the reaction of anthranilic acid with p-toluenesulfonic acid. It was characterized by elemental analysis, infrared spectroscopy, and X-ray single-crystal determination. The crystal structure analysis of 2-carboxyanilinium p-toulenesulfonate (3) has revealed a one-dimensional hydrogen-bonded network structure, involving the tosylate anion, the carboxyl group, and the ammonium group. The H(N)···O distances range from 1.97 to 2.23 Å. The molecular geometry and vibrational frequencies of 3 were calculated using the ab-initio method (HF) with the 6–31G(d) and 6–31+G(d,p) basis sets. The computed results indicate that the optimized geometry reproduces the crystal structure well, and the assignments of fundamental vibrations also agree well with the theoretical frequencies. The intermolecular proton transfer process between the ionic (3) and nonionic (4) structures was also investigated with the theoretical computations. The nonionic form (4) is energetically more stable than the ionic form (3) and TS(3→4) by 9.76 and 7.01 kcal/mol, respectively, including the zero-point vibrational energy correction at the HF/6–31+G(d,p) level. In addition, the atomic charges, the molecular electrostatic potentials, the nucleus-independent chemical shifts, and the frontier molecular orbitals of 3 were carried out at the HF/6–31+G(d,p) level of theory. Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures and tables