Different Types Of Hydrogen Research Articles

T dependence of vibrational dynamics of water in ion-exchanged zeolites A: A detailed Fourier transform infrared attenuated total reflection study

In order to explore the influence of cation substitution on the vibrational dynamics of water molecules in zeolites, the evolution of structural properties of the O-H stretching band of water in fully hydrated Na-A and Mg-exchanged A zeolites has been studied, for different percentages of induced ion exchange, by Fourier transform infrared attenuated total reflection spectroscopy as a function of temperature. The differences revealed in the O-H stretching band shapes have been accounted by fitting the spectra as a sum of four components, corresponding to water molecules exhibiting different types of hydrogen bonding. The dependencies of the relative intensities, peak wave numbers, and bandwidths of the resolved components on temperature and Mg2+ content have been discussed. Evidence of the "structure-maker" role played by a zeolitic surface on physisorbed water, systematically enhanced by increasing the percentage of induced ion exchange, is given in the whole explored temperature range.

Advanced 1 H Solid-State NMR Spectroscopy on Hydrogels, 1

Summary: The nature of the pH dependent collapse of poly(methacrylic acid) (PMAA) hydrogels is investigated using recent 1H solid-state NMR methods. In aqueous solution, PMAA changes from an expanded conformation at high pHs to a compact contracted form at low pHs, where hydrogen bonds play a central role. In solid-state 1H NMR spectra, recorded under fast magic angle spinning (MAS), dried PMAA samples previously collapsed at low pHs show characteristic signals in the spectral region of the carboxylic acid protons. With the aid of 2D 1H-1H double-quantum (DQ) MAS NMR spectra, three signals can be distinguished at 8, 10.5 and 12.5 ppm, which are attributed to free carboxylic groups and two different types of hydrogen bonded forms, respectively. The 12.5 ppm signal arises from the hydrogen bond with the shortest HH distance, corresponding to the form that is most stable with respect to increasing temperature and pH. The weaker hydrogen-bonded form (with a signal at 10.5 ppm) requires a slightly lower pH, while the free acid signal (at 8 ppm) emerges under the most acidic medium. Moreover, the stabilities of the hydrogen-bonded carboxylic acid dimers can be inferred from the proton-proton distances within the dimers, i.e. (275 ± 5) pm and (295 ± 15) pm for the protons at 12.5 and 10.5 ppm, respectively, which are determined by means of DQ MAS sideband patterns. Both the stability of the hydrogen bonds and the acidity of the protons may be related to the stereochemistry and the conformation of the PMAA chains.

FTIR–ATR studies of water structure in reverse micelles during the synthesis of oxalate precursor nanoparticles

Abstract The structure of water in water-in-oil microemulsions used to synthesize oxalate precusor nanoparticles for the production of YBa 2 Cu 3 O 7− x (YBCO) superconductor powder has been studied by FTIR–ATR spectroscopy of the OH stretching band. Two initial microemulsions are mixed together and nanoparticles are formed by a precipitation reaction in the cores of the reverse micelles of the resulting microemulsion. The shapes of the water OH stretching bands for the microemulsions before and after the reaction exhibit noticeable differences when normalized at their peaks. These differences have been quantified by decomposing the water OH stretching band into three components corresponding to water molecules with different types of hydrogen bonding. In the microemulsion after the precipitation and formation of oxalate precusor nanoparticles, the structure of water is characterized with an increased fraction of bound water. These bound water molecules are also connected with stronger H-bonds. We propose that upon synthesis of the precursor nanoparticles, the observed water structure changes are due to a thin water layer formed around the newly synthesized nanoparticles.

Isomorphism and Crystal Engineering: Organic Ionic Ladders Formed by Supramolecular Motifs in Pyrimethamine Salts

Pyrimethamine [2,4-diamino-5-(p-chlorophenyl)-6-ethyl-pyrimidine] (PMN) is an antifolate drug. Four new organic salts, namely, PMN hydrogen maleate (1), PMN hydrogen succinate (2), PMN hydrogen phthalate (3), and PMN fumarate (4), have been synthesized and their hydrogen bonding patterns have been analyzed. As expected, in all the structures, the PMN moieties are protonated at one of the nitrogen atoms of the pyrimidine rings. The carboxylate group of the respective anions interacts with the protonated pyrimidine moiety in near linear fashion through a pair of N−H···O hydrogen bonds to form a cyclic hydrogen-bonded motif. The crystal structures of compounds 1 and 2 are isomorphous as revealed by the very good agreement among their cell parameters. Interestingly, the hydrogen succinate mimics the hydrogen maleate here. In all three crystal structures (1−3), the hydrogen bonding motifs and their supramolecular patterns are the same, which is significant from a crystal engineering point of view in the building up of organic ionic ladders. In compound 4, the cyclic hydrogen-bonded motifs are self-organized through N−H···O, N−H···Cl, and C−H···N hydrogen bonds to the formation of different types of hydrogen bonding patterns.

Supramolecular architectures from the self-assembly of lanthanide coordination compounds containing glycine and phen via hydrogen bonding and π–π stacking interactions

Single crystal X-ray diffraction shows that [La(gly) 2(H 2O) 2(phen) 2(CH 3CH 2OH)](ClO 4) 3(phen) 3·3H 2O ( 1), [Ln(gly) 2(H 2O) 2(phen) 2](ClO 4) 3 (phen) 4· nH 2O [ n=0, Ln=Nd ( 2); n=1, Ln=Ho ( 3)], and [Yb(gly) 4(H 2O)(phen)](ClO 4) 4(phen) 2(gly+H)·2H 2O ( 4) (gly=glycine, phen=1,10-phenanthroline) with the coordination number 9 for La 3+, 8 for Nd 3+ and Ho 3+, and 7 for Yb 3+, exhibit the effect of lanthanide contraction. Complexes 1– 4 are all mononuclear structures, with the ligand glycine coordinated to the Ln 3+ ion in the monodentate mode and in zwitterionic form. There exist free phen molecules and solvent molecules in the lattice. Therefore, there are different types of hydrogen bonding and π–π stacking interactions in the crystals that give rise to different supramolecular architectures. The structure of 1 is composed of 1D chains which extend in the [1 0 0] direction, while those of 2 and 3 are 2D structures extending in the (0 0 1) plane. However, complex 4 shows a complicated 3D network.

Vibrational study of the secondary thioamide function, the intramolecular resonance assisted and intermolecular hydrogen bonding in NN′-hydroxyalkyl dithiooxamides

The article describes the vibrational characterization of the secondary thioamide formation and especially a spectroscopical interesting study of different types of hydrogen bonding in NN′-dihydroxyalkyldithiooxamides.

Condensation of Nucleobases at Mercury/Aqueous Solution Interface–A Structural Perspective Using Hydrogen Bonding Considerations

The two-dimensional condensation behavior exhibited by nucleobases at a mercury/aqueous solution interface is analyzed on the basis of their hydrogen-bonded quadruplex structures, and the experimentally observed critical temperatures are rationalized incorporating different types of hydrogen bonding, surface coordination effects, and stacking considerations. The proposed methodology provides a structural basis for the interpretation of critical temperatures and enables the calculation of the same pertaining to different modified nucleobases. The applicability of the procedure to order–disorder transitions of water dipoles at Hg electrodes is also indicated.

Hydrogen bonded structures in organic amine oxalates

Oxalates of n-propylamine, n-butylamine, ethylenediamine, 1,4-butanediamine, piperazine, guanidine and 1,4-diazabicyclo[2,2,2]octane (DABCO) have been synthesized and characterized by single crystal X-ray diffraction and other techniques. The amine oxalates show different types of hydrogen bonded networks, linear hydrogen bonded chains characterizing the oxalates of the first five amines. Guanidinium oxalate has a sheet like structure while DABCO oxalate has dimeric hydrogen bonded rings. Hydrogen bonded structures of these oxalates are discussed in detail, besides relating their thermal stability to the strengths of the networks.

Hydrogen insertion and protonic conductivity in lead phosphate Pb 3(PO 4) 2

The influence of hydrogen insertion on the conductivity of lead phosphate Pb 3(PO 4) 2 is reported. Transmission infrared (IR) spectra of single crystals of Pb 3(PO 4) 2 after annealing in water-moistened nitrogen or air show a broad band at 3250 cm −1 and a doublet at 2750–2800 cm −1, which are characteristic of the stretching vibrations of two different types of hydrogen bonding formed on insertion of hydrogen. Annealing in wet nitrogen increases the conductivity of lead phosphate crystals by factor 20–40. The monoclinic phase of lead phosphate, which exists below 453 K displays a strong anisotropy of the conductivity with that in the a-direction being a factor 100 greater than that in the c-direction, although the values of activation enthalpies are similar ( H a=0.64 eV, H c=0.58 eV). In the trigonal phase above 453 K, the activation enthalpy of H a=0.24 eV is typical of a superionic conductor. The quasi-two-dimensional character of the dc conductivity of Pb 3(PO 4) 2 is similar to that observed in well-known proton conductors of the M 3H(AO 4) 2 family where M=K, Rb, NH 4, Cs; A=S, Se. The mechanism of proton transport in lead phosphate is discussed on the basis of its structural isomorphism with the latter acid salts.

Synthesis and crystal structure of indium arsenate and phosphate dihydrates with variscite and metavariscite structure types

The hydrothermal synthesis, crystal structure analysis, and spectroscopic studies of InPO4·2H2O (1) and InAsO4·2H2O (2) are reported. Compound 1 is isomorphic with metavariscite: monoclinic P21/n (No. 14), a = 5.4551(3) A, b = 10.2293(4) A, c = 8.8861(3) A, β = 91.489(4)°, Z = 4, and compound 2 is isomorphic with variscite: orthorhombic Pbca (No. 61), a = 10.478(1) A, b = 9.0998(8) A, c = 10.345(1) A, Z = 8. Their three-dimensional frameworks are built of corner sharing InO4(H2O)2 octahedra and MO4 (M = P5+ or As5+) tetrahedra. The water molecules in both compounds have different environments and are involved in different types of hydrogen bonding. Infrared spectroscopy indicates that water molecules are true H2O species.

Structure and bonding of H2O2···X complexes with (X = NO+, CN-, HCN, HNC, CO)

Accurate B3LYP and MP2 theoretical calculations, with the 6-311+G(3df,2p) basis set, have been performed on different complexes, between hydrogen peroxide (HP) and NO+ (1), CN− (2–4), HCN (5–8), HNC (9–12) and CO (13 and 14). According to the binding energy obtained, the charged complexes (1–4) have large binding-energy values, yielding only cyclic stationary points. However, the neutral complexes (5–14) showed medium to small binding-energy values with linear and cyclic arrangements, the cyclic structures being transition states and the linear complexes minima, on their corresponding PESs. The “atoms in molecules” theory (AIM) was used to characterize the intermolecular interactions, ranging from electrostatic interactions for the HP···NO+ complex (1) to different types of hydrogen bonding for 2 to 14. For all the structures, the binding energy was corrected for the BSSE by the counterpoise (CP) method. Moreover, calculations were performed also on the BSSE-corrected PESs.

The Structure of Water in Crystalline Aluminophosphates: Isolated Water and Intermolecular Clusters Probed by Raman Spectroscopy, NMR and Structural Modeling

Raman spectroscopy, thermo-gravimetry and NMR together with EEM-Monte Carlo calculations are used to elucidate the properties of water in Metavariscite, AlPO4−H3, AlPO4-8 and VPI-5. The framework density of the aluminophosphates decreases along this sequence, the pore size increases, and the water is less confined. The Raman vibrations of water in different aluminum phosphates reflects the polarization by Al and the number, and the type of hydrogen bonds in which they participate. Metavariscite and AlPO4−H3 have well-defined symmetric νOH doublets in the region between 3000 and 3450 cm-1, corresponding to structural water molecules. AlPO4−H3 has additional free water with νOH at 3505 and 3563 cm-1. In AlPO4-8 and VPI-5 the majority of the water is zeolitic, and the corresponding feature is a broad band around 3200−3400 cm-1. The differences between Al-coordinated and zeolitic water is also evidenced by EEM-Monte Carlo calculations. For the octahedral Al, 27Al NMR is used to probe the different types involved. Mapping between principle hardness from electron population normal modes and force constants from the vibrational normal modes relates the influence of the environment of the water on the position and shape of the Raman bands. Perturbations imposed on water by the lattice Al (νOH < 3350 cm-1) and H bonding by O atoms alone (νOH > 3400 cm-1), change the symmetric OH-stretching polarization and decrease the principle hardness. The νOH vibrational frequency and the principal hardness splits as a result of different types of hydrogen bonding. When the number of interacting water molecules increases (Metavariscite → AlPO4-H3 → VPI-5) a broadening of the Raman bands and the hardness distribution of the OH polarization is seen. This EEM-Monte Carlo approach is used for the semiquantitative interpretation of Raman data.

Structural states and isotopic compositions of water in hydrothermal quartz, Koryu Deposit, Japan

Two different types of hydrogen in hydrothermal quartz from the Koryu deposit were distinguished by measurement of hydrogen isotope ratios and unpolarized and polarized infrared absorption spectra at room temperature and at -150 degrees C. The results of these measurements suggest that the hydrogen species in the hydrothermal quartz are liquid water (H 2 O) in fluid inclusions, silanol-type OH in the crystal structure of quartz, and liquid water in nanometer-sized domains of water molecules. Among them, the liquid water in liquid domains is most abundant. The hydrogen isotope ratio of liquid water in liquid domains is 40 per mil lower than that of water in fluid inclusions. This implies that a large amount of silanol OH was incorporated into the quartz during the rapid crystal growth stage and liquid domains of nanometer size were then formed in the quartz during subsequent hydrothermal activity and cooling. The water extracted between 300 degrees and 500 degrees C yields the delta D value of the hydrothermal solution associated with quartz precipitation.

Hydrogen bonding pattern in N-benzoyl(- dl-)- l-phenylalanines as revealed by solid-state NMR spectroscopy

The nature of the hydrogen bonding pattern has been investigated in N-benzoyl- dl-phenylalanine ( 1) and N-benzoyl- l-phenylalanine ( 2) polymorphes by solid-state NMR spectroscopy. It has been shown that the multiple resonances of carboxyl carbon in 2 are directly connected to different types of hydrogen bonding. The differences in intermolecular distances of carboxyl groups involved in different types of hydrogen bonding have been visualized by the 2D exchange and 1D ODESSA experiments. Potential applications of such a new approach include the exploration of intermolecular distances in hydrogen bonded compounds with singly labeled biomolecules.

Characterization of coal tar pitches with different softening points by [formula omitted] NMR : Role of the different kinds of protons in the thermal process

Optimum experimental conditions for a quantitative 1 H Nuclear Magnetic Resonance ( 1 H NMR) analysis of coal tar pitches are given. From the variety of sample concentrations studied, it was found that 3% in weight was the most suitable concentration for 1 H NMR experiments. The cut-off points were adjusted and the different types of hydrogen in the resultant regions were identified. The patterns used for both purposes were prepared according to the quali- and quantitative information given by Gas Chromatography (gc). Using these conditions, four coal tar pitches with different softening point were characterized. Some new parameters were defined with the aim of obtaining an important amount of more reliable information.

A new class of flexible energetic salts, part 2: The crystal structures of the cubane-1,4-diammonium dinitramide and cubane-1,2,4,7-tetraammonium dinitramide salts

The crystal structures of cubane-1,4-diammonium dinitramide, 1, and cubane-1,2,4,7-tetraammonium dinitramide, 2, have been determined. 1 crystallizes in the space group P21/c with cell dimensions a = 6.018(2), b = 11.642(3), c = 9.754(3) A, β = 107.24(2), while 2 crystallizes in the space group P21/c with cell dimensions a = 9.401(4), b = 9.603(3), c = 12.603(4) A, β 111.08(3). In these structures the ammonium substituents are symmetrically attached with respect to the cubane skeleton and have neither low lying empty orbitals nor available lone pairs of electrons thus they have a minimal effect on the metrical parameters of the cubane skeleton. All C–C bond lengths are close to the overall average C–C bond length for all reported cubanes of 1.559 A. The conformations adopted by the dinitramide ions in both structures are quite different, with the bend, twist, and torsion angles for the dinitramide ion in 1 being significantly larger than those found for the dinitramide ions in 2, due to the different types of hydrogen bonding found in the two structures. In 2, the conformation adopted by the adjacent ammonium ions allows two of the three protons from each ammonium cation to form hydrogen bonds in such a manner that they span either the syn or the anti oxygen atoms of a single dinitramide anion. The dinitramide anion is thus constrained by these interactions and is less free to twist and bend. These results provide further confirmation that the metrical parameters of both the cubane and dinitramide moieties are flexible and reflect their local environment.

Self assembly in transition metal complexes: structural characterisation of the zinc carboxylate{bis(2-pyrrolecarboxylato)bis(1-methylimidazole)}zinc(II)

The synthesis, spectral characterisation of the zinc(II) pyrrolecarboxylates, [Zn(2-Hpyrrc) 2(H 2O)] ( 1) and [Zn(2-Hpyrrc) 2(1-methylimidazole) 2] ( 2) (2-H 2pyrrc = 2-pyrrolecarboxylic acid) is reported as well as the X-ray structure determination of the latter compound. The molecular structure of 2 exhibits a distorted tetrahedral geometry around the zinc atom. The pyrrole-2-carboxylic acid acts as a monodentate ligand, syn-bound via one carboxylate oxygen atom. In the crystal structure, the discrete molecules of 2 are organised in dimers linked by a complex network of hydrogen bonds. A comparative IR study confirms the existence of different types of hydrogen bonding.

Matrix isolation infrared studies of complexes formed between substituted phenols and trimethylamine

Infrared spectroscopy and matrix isolation technique have been used to study the 1 : 1 complexes formed between 2,4,5-trichlorophenol (TCP), pentachlorophenol (PCP) or 2-chloro-4,6-dinitrophenol (CNP) and trimethylamine (TMA) isolated in solid argon. The results were analyzed in relation to the type of complex formed. Depending on the proton-donor ability of the phenol three different types of hydrogen bonded complexes have been identified in argon matrices. The weakest phenol in the series, TCP (pKa = 6.72), forms a strong molecular hydrogen bonded complex with TMA as indicated by the broad ν(OH⋯N) absorption with a maximum at 2490 cm−1 and a band at 811 cm−1 due to the νs(C3N) mode of the perturbed amine. The strongest phenol, CNP (pKa = 2.01), interacts with TMA in an argon matrix to form ionic complex with the proton transferred to the base molecule. This is evidenced by the presence of the ν(NH+O−) absorption between 3000−1800 cm−1, by the νas(C3N+) and νs(C3N+) absorptions due to the protonated amine and by numerous product bands due to the relatively strongly perturbed modes of the phenol ring. The interaction between TMA and a phenol of intermediate strength, PCP (pKa = 4.74), in solid argon probably leads to the formation of two types of hydrogen bonded complexes: an ionic complex with the proton transferred to the amine molecule and a pseudosymmetric one with the proton more or less equally shared between the phenol and amine molecules. In this case the protonic absorption consists of two broad features situated in the 3000–1600 cm−1 and 950–400 cm−1 regions due to the ν(NH+⋯O−) and ν(O⋯H⋯N) modes, respectively.

Vibrational characterization of azobenzenes, azoxybenzenes and azoaromatic and azoxyaromatic polyethers

Raman and infrared spectra of a bisphenol-A-containing azoaromatic polyether, a bisphenol-A-containing azoxyaromatic polyether and a bisphenol-A-containing 2-hydroxyazoaromatic polyether were analyzed. Vibrational spectra were also collected for the corresponding model compounds 4,4′-(4-tert-butylphenoxy)azobenzene, 4,4′-(4-tert-butylphenoxy)azoxybenzene and 4,4′-(4-tert-butylphenoxy)-2-hydroxyazobenzene. Comparisons with substituted azobenzenes and azoxybenzenes were used in assigning the spectra in the 1650–900 cm-1 region. Assignments of the N=N stretch (1410–1390 cm-1) demonstrate that all of the compounds are in the trans configuration. The azo bridge vibrations of the azoaromatic ethers are very similar to those of azobenzene. Different types of hydrogen bonding are seen in the 2-hydroxyazoaromatic compounds. The polyether has an OH stretch at 3355 cm-1 which indicates a network of intermolecular hydrogen bonds among the polymers. The 2-hydroxyazoaromatic model compound has no IR peak above 3100 cm-1 and N=N, CO and CN stretches which are shifted due to an intramolecular hydrogen bond with the azo nitrogen. The N=N stretch of the azoxyaromatic ethers is at the same wavenumber as in the azo compounds. Assignment of the N→O stretch vibration is difficult because of mixing with other modes of the azoxy bridge. © 1997 John Wiley & Sons, Ltd.

Solution blends of polyacrylonitrile with segmented polyurethanes: Effect of soft segments

Abstract Solution blends of a modified polyacrylonitrile (PAN) with polyurethane (PU) obtained from 4, 4′-diphenylmethane diisocyanate (MDI) and two different types of polyols– i.e., ether-linked polytetramethylene ether glycol (PTEG) and ester-linked polytetramethylene adipate glycol (PTAG) – were prepared in N, N-dimethylformamide (DMF). The domains in the PTAG-PU blends were much finer than those in the PTEG-PU blends. Shift of the soft segment transition temperatures (T gs) of PU toward lower temperature with increasing PAN was more significant for PTAG-PU blends. Miscibility was also examined through Fourier transform infrared spectra. These showed clear carbonyl peak shifts due to the different types of hydrogen bonding. The PTAG-PU/PAN (30/70) blend had the maximum draw ratio at failure, measured in 100°C water; it was over 2.5 times that of pure PAN.