Various Types Of Hydrogen Bonds Research Articles

Lignite powder briquetting with binder and adsorption model of binder on the coal surface

ABSTRACT The addition of different binders can improve the mechanical strength of briquette for the lignite powder. The changes of lignite in wettability, functional groups and surface electrical properties were analyzed after briquetting. The model of the interaction between the binder and coal particle was studied. The results revealed that starch and polyvinyl alcohol binders could make the compressive and drop strength of lignite briquette strong. When the potential value decreased, it was beneficial to the briquetting process. The Fourier transform infrared spectra (FTIR) analysis showed that functional groups of binder adsorbed the oxygen-containing functional groups of coal. After the binder interacted with the pulverized coal, the molecules in the binder were adsorbed on the surface of coal, which changed the hydrophobicity of the pulverized coal. An adsorption model was proposed as follows: The first was the various types of hydrogen bonds between the hydroxyl terminus of binder and the carboxyl group or hydroxyl group on the surface of coal. The second was the generation of hydrogen bonds among the binder molecules. The greater hydrogen bonding was, the higher the strength of briquette was.

High latent heat and recyclable form-stable phase change materials prepared via a facile self-template method

High latent heat, no leakage and recyclable are the comprehensive properties of phase change materials (PCMs). In this study, which was inspired by the structures of orange and pomegranate, a facile strategy via a self-template method was adopted to prepare form-stable phase change materials (FSPCMs) for the first time. Utilising poly(ethylene glycol) (PEG) spherulite crystals as templates, the cross-linked polymer (named CPA) was prepared as a supporting material by in situ polyaddition. The bionic vesicle structure microstructures were investigated by parallel optical stereo microscope and scanning electron microscope. The results suggest that a vesicle-like structure is formed in the prepared PEG/CPA FSPCMs. Compared with the FSPCMs prepared by interpenetrating cross-linked network method, the FSPCMs prepared by self-template method has higher PEG loading value. Especially, when PEG-20K (the molecular weight is 20 K) with a larger spherulite diameter was used as a template to prepare PEG-20K/CPA FSPCMs, the loading value was as high as 900%. Moreover, in a process attributed to the regeneration of various types of hydrogen bonds, ionic bonds and transesterification, the recyclable CPA enables the PEG-20K/CPA (9/1) FSPCMs to possess good thermally reversible reusability.

Hydrogen Bonds and FTIR Peaks of Polyether Polyurethane-Urea

Various types of hydrogen bonds exist in polyether polyurethane, polyurethane-urea and polyurea (PUA) and can cause microphase separation. The morphology, properties and applications of polyether PUA are determined by the microphase separation. All kinds of hydrogen bonds make it difficult to assignments of Fourier transform infrared spectroscopy (FTIR) peaks of ether linkage, amine and carbonyl group. This affects the calculation of the hydrogen bonding degree of the hard segments for estimating the degree of microphase separation. This paper summarized hydrogen bonding structures between proton donors and proton acceptors. By analyzing the influence of electronic effect, steric effect, various types of hydrogen bonds and the degree of order of hydrogen bonding on infrared peaks, the relationships between hydrogen bonding structures and infrared peaks are established. Lay the theoretical foundation for evaluating the degree of microphase separation by FTIR method.

A novel poly (vinyl alcohol)/poly (ethylene glycol) scaffold for tissue engineering with a unique bimodal open-celled structure fabricated using supercritical fluid foaming

In this study, a novel poly (vinyl alcohol) (PVA)/poly (ethylene glycol) (PEG) scaffold was carefully designed via thermal processing and subsequent supercritical fluid (SCF) foaming. Interestingly, a bimodal open-celled structure with interconnected networks was successfully created in the plasticized PVA (WPVA)/PEG scaffold. Large cells were produced from the nucleation sites generated in the PVA phase during rapid depressurization, while plenty of small pores generate in the cell walls of the big cells. The formation mechanism of this cellular structure was studied by considering the various phase morphologies and the diffusion behaviour of the carbon dioxide (CO2) in individual phases. In addition, the intermolecular interactions of the WPVA/PEG blend were studied using X-ray diffraction and FTIR analysis. The results demonstrate that various types of hydrogen bonds among the hydroxyl groups on the PVA chains, PEG and water molecules are formed in the blend system. The realization of thermoplastic foaming of the PVA/PEG blend benefits from the interactions of complexation and plasticization between water and PEG molecules. The SEM images also revealed that L929 fibroblast cells were able to attach and spread on surfaces of the WPVA/PEG samples. Thus the WPVA/PEG scaffold with unique bimodal cellular structure is nontoxic and favours the attachment and proliferation of cells, making it promising for use as the candidate for tissue engineering applications.

Noncovalent Interactions between Molecular Hydrogen and the Alkali Fluorides: H-H···F-M (M = Li, Na, K, Rb, Cs). High Level Theoretical Predictions and SAPT Analysis.

Various types of hydrogen bonds have been recognized during the past century. In this research, a new type of noncovalent interaction, the dipole-induced hydrogen bond formed between a hydrogen molecule and an alkali halide, H-H···F-M, is studied. Proposed by Zhang and co-workers ( Phys. Chem. Chem. Phys. 2015, 17, 20361), these systems are extensively investigated initially using the "gold standard" CCSD(T) method in conjunction with augmented correlation-consistent polarized core-valence basis sets up to quadruple-ζ. The full triple excitations CCSDT method has been used to further refine the energies. Several properties including geometries, bond energies, vibrarional frequencies, charge distributions, and dipole moments have been reported. The earlier Zhang research considered only the linear H-H···F-M structures. However, we find these linear stationary points to be separated by very small barriers from the much lower lying bent C s structures. The CCSDT/aug-cc-pCVQZ(-PP) method predicts the dissociation energies for bent H-H···F-M (M = Li, Na, K, Rb, Cs) are 2.76, 2.96, 3.00, 2.89, and 2.49 kcal mol-1, respectively, suggesting that the H···F hydrogen bond becomes gradually stronger when alkali metal M goes down the periodic table from Li to K but becomes slightly weaker for Rb and even more for Cs. This Li < Na < K > Rb > Cs order is consistent with that for the dipole moments for the isolated MF (M = Li, Na, K, Rb, Cs) diatomics. Symmetry adapted perturbation theory (SAPT) is used to understand these unusual noncovalent interactions.

THEORETICAL STUDY ON THE HYDROGEN BONDING INTERACTIONS IN PARACETAMOL-WATER COMPLEXES

The paracetamol–water (PA–H2O) complexes formed by hydrogen bonding interactions were investigated at the MP2/6–311++G(d,p) level. Six PA–H2O complexes possessing various types of hydrogen bonds (H–bonds) were characterized by geometries, energies, vibrational frequencies. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) and the localized molecular orbital energy decomposition analysis (LMO–EDA) were performed to explore the nature of the hydrogen–bonding interactions in these complexes. The intramolecular H–bond formed between the methylene and carbonyl oxygen atom of paracetamol is retained in most of complexes. The H–bonds in PW1 and PW6 are stronger than other H–bonds, moreover, the researches show that both the hydrogen bonding interaction and structural deformation play important roles for the relative stabilities of PA–H2O complexes.

Dynamics of proteins aggregation. I. Universal scaling in unbounded media

It is well understood that in some cases proteins do not fold correctly and, depending on their environment, even properly-folded proteins change their conformation spontaneously, taking on a misfolded state that leads to protein aggregation and formation of large aggregates. An important factor that contributes to the aggregation is the interactions between the misfolded proteins. Depending on the aggregation environment, the aggregates may take on various shapes forming larger structures, such as protein plaques that are often toxic. Their deposition in tissues is a major contributing factor to many neuro-degenerative diseases, such as Alzheimer's, Parkinson's, amyotrophic lateral sclerosis, and prion. This paper represents the first part in a series devoted to molecular simulation of protein aggregation. We use the PRIME, a meso-scale model of proteins, together with extensive discontinuous molecular dynamics simulation to study the aggregation process in an unbounded fluid system, as the first step toward MD simulation of the same phenomenon in crowded cellular environments. Various properties of the aggregates have been computed, including dynamic evolution of aggregate-size distribution, mean aggregate size, number of peptides that contribute to the formation of β sheets, number of various types of hydrogen bonds formed in the system, radius of gyration of the aggregates, and the aggregates' diffusivity. We show that many of such quantities follow dynamic scaling, similar to those for aggregation of colloidal clusters. In particular, at long times the mean aggregate size S(t) grows with time as, S(t) ∼ tz, where z is the dynamic exponent. To our knowledge, this is the first time that the qualitative similarity between aggregation of proteins and colloidal aggregates has been pointed out.

On 2:1 melamine – Squaric acid dihydrate complex: The structure and vibrational spectra

In the present paper we would like to describe the structural and dynamical properties of crystalline dihydrated complex of melamine (2,4,6–triamino-1,3,5–triazin-1-ium) with squaric acid (3,4-dihydroxycyclobut-3-ene-1,2-dione) abbreviated as MH·SQ. The X-ray diffraction studies show the presence of deprotonated units (C4O4)2- and single protonated melamine cations surrounded by tetrameric water assemblies (H2O)4. The formation of the water tetramers deserves a special attention. IR absorption and Raman spectra reflect a richness of structural units and numerous hydrogen bonds. The presence of the continua in the IR spectra, with a characteristic presence of the Hadži's trio enriched by a numerous submaxima, may be ascribed to the structural units and to the various types of hydrogen bonds. The density functional theory calculation with the periodic boundary conditions was use to precise analysis of experimental data.

Polymorphs in room-temperature ionic liquids: Hierarchical structure, confined water and pressure-induced frustration

Room-temperature ionic liquids (RTILs) can extract hidden information about water. Various types of hydrogen bonds of water are detected clearly in the liquid, glass, and crystal states. In addition to hydrogen bonding in water, balancing among charge (scalar), dipole (vector), and coordination number (topology) contribute to heterogeneous structure on the multiple scales in RTILs–water systems. The water-mediated hierarchical structure in the liquid is connected to macroscopic properties such as AC impedance, pH oscillations, density, and differential scanning calorimetry trace as a function of water concentration. Nanoscale water confinement was observed inside the RTILs, and the size and distribution of confined water were tuned by water concentration and temperature. The loosely packed confinement plays an important role in the engineering of next generation novel nanoheterogeneous materials. High-pressure crystal polymorphs were identified in pure RTILs by X-ray diffraction and Raman spectroscopy. By further compression, amorphous appeared partially in the deformed crystalline.

Color Polymorphism: Understanding the Diverse Solid-State Packing and Color in Dimethyl-3,6-dichloro-2,5-dihydroxyterephthalate

Dimethyl-3,6-dichloro-2,5-dihydroxyterephthalate (MCHT) is known to exist in three differently packed crystals having three different colors, namely yellow (Y), light yellow (LY), and white (W). Apart from the difference in their color, the molecules in the crystals also differ in their intramolecular O-H⋅⋅⋅O and O-H⋅⋅⋅Cl hydrogen bonds. Time-dependent DFT calculations reveal the role of the various types of hydrogen bonds in controlling the color of the polymorphs. Mechanistic pathways that lead to such transformations in the crystal are elucidated by solid-state dispersion-corrected DFT studies. Relative stabilities of the various polymorphs rationalize the experimentally observed transformations between them. Calculations reveal that the minimum-energy pathway for the conversion of the Y form to a W form is through stepwise disrotatory motion of the two -OH groups through a hybrid intermediate having one intramolecular OH⋅⋅⋅O and one O-H⋅⋅⋅Cl bond. The LY form is shown to exist on the higher-energy pathway involving a concerted Y→W transformation.

Density functional theory, natural bond orbital and quantum theory of atoms in molecule analyses on the hydrogen bonding interactions in tryptophan-water complexes

The tryptophan-water (Trp-H2O) complexes formed by hydrogen bonding interactions were investigated at the ωB97XD/6–311+ +G(d,p) level. Five Trp-H2O complexes possessing various types of hydrogen bonds (H-bonds) were characterized by geometries, energies, vibrational frequencies. The nature of the H-bonds were characterized by the natural bond orbital (NBO) and the quantum theory of atoms in molecule (QTAIM) analyses as well. The intramolecular H-bond formed between the amino and carboxyl oxygen atom of tryptophan was retained in most of the complexes, and the cooperativity between the intra and intermolecular H-bonds exist in some complexes. The intramolecular H-bond and some intermolecular H-bonds are strong and have partial covalent character. The H-bonds formed between carboxyl and oxygen/nitrogen atoms are stronger than other H-bonds. The H-bonds involving methylene of tryptophan as H-donor are weak H-bonds. For all complexes, ΔE ele and ΔE ex makes major contributions to the total interaction energy (ΔE MP2), while ΔE disp is the smallest component of the interaction energy. Both hydrogen bonding interaction and structural deformation play important roles in the relative stabilities of the complexes. Regardless of strong H-bonds, the stabilities of some complexes are weakened by the serious structural deformations. The hydrogen bonding interactions between tryptophan (Trp) and water have been investigated by the density functional theory (DFT) approach, the QTAIM and NBO analyses to elucidate the hydrogen bonding interaction characteristics in Trp–H2O complexes.

Theoretical Study on the Hydrogen Bonding Interactions in Complexes of 5‐Hydroxytryptamine with Water

AbstractThe energies, geometries and harmonic vibrational frequencies of 1:1 5‐hydroxytryptamine‐water (5‐HT‐H2O) complexes are studied at the MP2/6‐311++G(d,p) level. Natural bond orbital (NBO), quantum theory of atoms in molecules (QTAIM) analyses and the localized molecular orbital energy decomposition analysis (LMO‐EDA) were performed to explore the nature of the hydrogen‐bonding interactions in these complexes. Various types of hydrogen bonds (H‐bonds) are formed in these 5‐HT‐H2O complexes. The intermolecular C4H55‐HT···Ow H‐bond in HTW3 is strengthened due to the cooperativity, whereas no such cooperativity is found in the other 5‐HT‐H2O complexes. H‐bond in which nitrogen atom of amino in 5‐HT acted as proton donors was stronger than other H‐bonds. Our researches show that the hydrogen bonding interaction plays a vital role on the relative stabilities of 5‐HT‐H2O complexes.

Hydrogen-bonding interactions in adrenaline–water complexes: DFT and QTAIM studies of structures, properties, and topologies

ωB97XD/6-311++G(d,p) calculations were carried out to investigate the hydrogen-bonding interactions between adrenaline (Ad) and water. Six Ad-H(2)O complexes possessing various types of hydrogen bonds (H-bonds) were characterized in terms of their geometries, energies, vibrational frequencies, and electron-density topology. Natural bond orbital (NBO) and quantum theory of atoms in molecules (QTAIM) analyses were performed to elucidate the nature of the hydrogen-bonding interactions in these complexes. The intramolecular H-bond between the amino and carboxyl oxygen atom of Ad was retained in most of the complexes, and cooperativity between the intra- and intermolecular H-bonds was present in some of the complexes. H-bonds in which hydroxyls of Ad/water acted as proton donors were stronger than other H-bonds. Both hydrogen-bonding interactions and structural deformation play important roles in the relative stabilities of the complexes. The intramolecular H-bond was broken during the formation of the most stable complex, which indicates that Ad tends to break the intramolecular H-bond and form two new intermolecular H-bonds with the first water molecule.

Fourier Transform Raman and DFT Study of Blue Shift C–H Stretching Vibration of Diazines on Hydrogen Bond Formation

Abstract Diazines form various types of hydrogen bonds with water, wherein C–H groups are sometimes involved directly and sometimes indirectly. On hydrogen bond formation, the wavenumber of C–H stretching vibration are usually red shifted (normal hydrogen bond) but blue shift of C–H modes (anomalous hydrogen bond) is also possible in some cases. The Raman spectra of the C–H stretching bands of three diazines; pyrimidine, pyridazine, and pyrazine in pure form and at many concentrations in mole fractions of diazines in the mixture of diazines + water have been measured to analyze the wavenumber shifts experimentally. Theoretical wavenumber shifts have been calculated and NBO analysis has been performed using DFT methods to understand the cause of the shifts. All the four C–H stretching bands of diazines are blue shifted on dilution with water both experimentally and theoretically. The NBO calculations reveal that the cause of the shift is decrease in the charge density in the antibonding orbital of C–H bond on complex formation.

Characteristics of X-H···π Interactions: Ab Initio and QTAIM Studies

The MP2/6-311++G(d,p) calculations were performed on several hydrogen-bonded systems. Different complexes were taken into account to analyze various types of hydrogen bonds, possessing different types of proton donors and proton acceptors as well as characterized by the broad range of the interaction energy. The Quantum Theory of Atoms in Molecules is applied. The results of the hybrid variational-perturbational approach are discussed. The unique properties of hydrogen bonds, where π-electrons act as the proton acceptor (X-H···π), are analyzed, and these interactions are compared with the other types of hydrogen bonds, mainly with C-H···Y interactions. It is shown that for X-H···π systems the ellipticity at the bond critical point of the proton···acceptor interaction is much greater than for the other types of hydrogen bonds. However, both X-H···π and C-H···Y interactions are characterized by the dominance of the dispersive energy.

Chiral Biphenyldicarboxylic Acid Networks Stabilized by Hydrogen Bonding

The self-assembly of 4,4′-biphenyldicarboxylic acid on a Au(111) surface is investigated by means of in situ ultra-high-vacuum scanning tunneling microscopy. Three types of open networks with increasing interpore distance are observed. Experiments and theoretical calculations reveal that the two-dimensional porous networks are stabilized by various types of hydrogen bonds between carboxyl groups and by van der Waals interactions. Cyclic tetrameric and half-cyclic trimeric hydrogen-bonding motifs are shown to induce chirality in the open networks.

Geometrical Preferences of the Hydrogen Bonds on Protein-Ligand Binding Interface Derived from Statistical Surveys and Quantum Mechanics Calculations.

We have conducted potential of mean force (PMF) analyses to derive the geometrical parameters of various types of hydrogen bonds on protein-ligand binding interface. Our PMF analyses are based on a set of 4535 high-quality protein-ligand complex structures, which are compiled through a systematic mining of the entire Protein Data Bank. Hydrogen bond donor and acceptor atoms are classified into several basic types. Both distance- and angle-dependent statistical potentials are derived for each donor-acceptor pair, from which distance and angle cutoffs are obtained in an objective, unambiguous manner. These donor-acceptor pairs are also studied by quantum mechanics (QM) calculations at the MP2/6-311++G** level on model molecules. Comparison of the outcomes of PMF analyses and QM calculations suggests that QM calculation may serve as an alternative approach for characterizing hydrogen bond geometry. Both of our PMF analyses and QM calculations indicate that C-H···O hydrogen bonds are relatively weak as compared to common hydrogen bonds formed between nitrogen and oxygen atoms. A survey on the protein-ligand complex structures in our data set has revealed that Cα-H···O hydrogen bonds observed in protein-ligand binding are frequently accompanied by bifurcate N-H···O hydrogen bonds. Thus, the Cα-H···O hydrogen bonds in such cases would better be interpreted as secondary interactions.

Various Types of Hydrogen Bonds, Their Temperature Dependence and Water−Polymer Interaction in Hydrated Poly(Acrylic Acid) as Revealed by 1H Solid-State NMR Spectroscopy

Various types of hydrogen bonds, their temperature dependence and water−polymer interaction in hydrated poly(acrylic acid) (PAA) were systematically investigated using 1H CRAMPS solid-state NMR techniques in the temperature range from 25 to 110 °C. The 1H CRAMPS NMR methods are based on a recently developed continuous phase modulation technique for 1H−1H homonuclear dipolar decoupling. The 1H CRAMPS experiments revealed four types of protons in hydrated PAA which are assigned to protons from the mutually hydrogen-bonded COOH groups (1), from the free COOH groups (2), from the COOH groups bounded with water or from water bounded with COOH groups which are undergoing fast chemical exchange mutually (3), and from main chain groups (4), respectively. Furthermore, we proposed double-quantum filtered and dipolar filtered 1H CRAMPS experiments to further assign the protons according to their dipolar coupling strength. In addition, high-resolution spin echo 1H CRAMPS experiments were further employed to accurately determine the chemical shift of these protons. These NMR techniques were also used to elucidate the molecular mobility of the different groups. It was found that dehydration in PAA promotes the formation of hydrogen bonds between COOH groups. Variable-temperature 1H CRAMPS experiments demonstrated that the dissociation of the hydrogen bonds between COOH groups occurs dramatically at lower temperature in hydrated PAA and slowly over a wide range of temperature in dehydrated PAA. It was also found that the dehydration of water bounded with COOH groups in hydrated PAA occurs significantly at high temperature. The NMR results were compared with previous work using DSC and other techniques. Besides undergoing fast chemical exchange, the adsorbed water was also demonstrated in proximity with the free COOH groups and far from the hydrogen bonds between COOH groups by using two-dimensional 1H−1H spin-exchange NMR experiments.

Hydrogen Bonding Contribution to Lipophilicity Parameters. Hydrogen Acceptor and Hydrogen Acceptor Donor Parameters

In our analysis of the composition of lipophilicity parameters by the intermolecular force (IMF) model we have made use of nH, the number of OH and/or NH bonds, as a measure of the hydrogen donor capacity of a substituent; and nn, the number of lone pairs on O and/or N atoms in the substituent, as a measure of the hydrogen acceptor capacity of the substituent. The basis of this method is the reasonable assumption that in 55.6 molar water hydrogen bonding is maximized. The method does not account however for differences in the energy of different types of hydrogen bonds, but further assumes that these differences are to a first approximation negligible. In order to improve the model we have defined a scale of group hydrogen bonding acceptor parameters, ηXHA, and overall hydrogen bond parameters ηXHAD from the water/1-octanol partition coefficients of AkX where Ak is alkyl. These parameters should account for both the extent of hydrogen bonding in water and for the difference in hydrogen bond energies of the various types of hydrogen bonds encountered. Correlations of log P values for Ph(CH2)nX, X1(CH2)X2, and substituted amino acids Xaa with the IMF equation using the ηXHA and ηXHAD parameters demonstrated their use. Correlation of log P values for PhX suggested that for many groups separate sets of ηXHA and ηXHAD values are required when they are bonded to sp2 hybridized carbon rather than sp3 hybridized carbon.

2H NMR studies of betaine phosphate

2H NMR measurements on single crystals of betaine phosphate in the antiferrodistortive and paraelectric phases were performed, in order to study the behaviour of the deuterium atoms in the hydrogen bridges and in the methylene groups and to characterize structural changes near the phase transition. By means of two dimensional 2H NMR exchange experiments the dynamics of the proton ordering in the various types of hydrogen bonds is investigated.