Oxygen Atom Of Water Molecule Research Articles

NMR and FT-IR analysis of new molecular complex 1-piperidine-carboxylate-piperidinium-H2O

Piperidine absorbs CO2 and H2O contents in air to form a molecular complex: piperidium-1-piperidinecarboxylate-H2O. The structure of the complex was characterized by FT-IR and NMR. The complex is stabilized via five hydrogen bonds between the three components, N···O electrostatic interaction and O···O interaction (electron transfer) between1-piperidinecarboxylate and H2O. Through electron transfer from the carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O—H bond is considerably shorter than that of free water molecule. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.

New crystal structure of molecular complex 1-piperidine carboxylate-piperidinium-H2O studied by X-ray single crystal diffraction

Piperidine absorbs CO2 and H2O in air to form a molecular complex: piperidium-1-piperidinecarboxylate-H2O. The structure of the complex was characterized by X-ray single crystal diffraction. The crystal structure was determined to be triclinic, space group P\(\bar 1\) with a=0.648 6(8) nm, b=0.809 2(10) nm, c=1.357 1(16) nm, α=96.967(16)°, β=102.506(15)°,, γ=104.202 (15)°, Z=2. The complex is stabilized via five hydrogen bonds between the three components, N—O electrostatic interaction and O—O interaction (electron transfer) between1-piperidinecarboxylate and H2O. Due to electron transference of carbamate ion, the oxygen atom in water molecule is strongly negatively charged and the O—H bond is considerably shorter than that of the free molecule of water. The formation of the molecular complex is a reversible process and will decompose upon heating. The mechanism of formation and stabilization is further investigated herein.

Coordination polymer of lanthanum: synthesis, properties and crystal structure of [La(4,4′-bipyridine)(CCl2HCOO)3(H2O)] n

A new mixed ligand complex of general formula [La(H2O)(4,4′-bpy)(CCl2HCOO)3] n has been synthesized and characterized by elemental and thermal analysis, IR spectroscopy and conductivity studies. The crystal and molecular structure was determined. The lanthanum atom is ten coordinate by four oxygen atoms from two chelating tridentate dichloroacetate substituents, two oxygen atoms from two bidentate bridging dichloroacetate groups, two oxygen atoms from two bridging tridentate dichloroacetate substituent, one oxygen atom of water molecule and one nitrogen atom from 4,4′-bipyridyl substituent. The coordination polyhedron of central atom can be described as tetradecahedron. The molecules are built up by O–H ··· N hydrogen bonds to a two-dimensional network.

Spectroscopic characterization, crystal structure determination and interaction with DNA of novel cyano substituted benzimidazole derivative

Novel cyano-substituted benzimidazole derivatives 3 and 4 were synthesized from 4-N,N-dimethylamino-benzaldehyde and 2-cyanomethyl-benzimidazole. 2-(1H-benzimidazol-2-yl)-3-(4-N,N-dimethylamino-phenyl)-acrylonitrile hydrochloride monohydrate 4 has been studied by 1H and 13C NMR, IR, MS, UV/Vis and fluorescence spectroscopy and confirmed by X-ray crystal structure analysis. The interaction of 4 with ct-DNA has also been investigated by fluorescence spectroscopy and melting temperature determination experiment. According to the emission spectra recorded in the absence and presence of ct-DNA at different ratios r ([compound]/[polynucleotide]), 4 showed marked decrease in the fluorescence intensity and very strong hypochromic effect. Melting temperature experiment showed weak stabilization of double helix. To determine binding mode of 4, other additional experiments are necessary. The molecules of 4 are almost planar with the dihedral angle between benzimidazole and phenyl rings of 6.99(6)°. The protonation of nitrogen atom of benzimidazole ring is followed by π-electrons delocalization in the region resulting in C–N bond distances equality [1.341(2) and 1.337(2) A]. Both NH groups of benzimidazole ring form intermolecular hydrogen bonds, one with the oxygen atom of water molecule [N···O 2.689(2) A] and the other with Cl− ion (N···Cl− 3.051(1) A). Except proton acceptor, water molecule acts as double proton donor in the formation of intermolecular hydrogen bonds with Cl− ion [O···Cl− 3.126(2) and 3.169(2) A]. In that way, infinite chains along [110] direction are formed.

The first example of a complex of N-perfluoroarylated azacrown ether: The crystal structure of diaqua{N,N′-bis(tetrafluoropyridyl)diaza-18-crown-6}lead(II) perchlorate

Complex formation of lead(II) perchlorate with N,N′-diaryldiaza-18-crown-6 (aryl = C6H5, 4-MeOC6H4, 4-C5F4N) has been studied. The stability of the complexes decreases with an increase in the electron-withdrawing character of the aryl substituent in the series (logβ, methanol): 4-MeOC6H4 (4.7), C6H5 (2.7), 4-C5F4N ( 2σ(I). In the complex cation [Pb(L)(H2O)2]2+, the coordination geometry of the metal atom is determined by partial delocalization of the lone pair. The Pb atom is asymmetrically bound to four oxygen atoms of substituted diaza-18-crown-6 and two oxygen atoms of water molecules (Pb-O, 2.450–2.726 A). The CN of the metal atom is completed to ten by two nitrogen atoms of the macrocycle and two ortho fluorine atoms of two tetrafluoropyridyl substituents of the ligand L at longer distances (Pb-N, 2.978 and 3.108 A; Pb-F, 2.890 and 3.123 A).

Synthesis, structural investigation and thermal stability of aqua magnesium(II) phthalocyanine adducts with 2-methoxyethylamine

Three new aqua magnesium phthalocyaninato complexes with 2-methoxyethylamine (MEA) in crystalline form have been obtained. The composition of the complexes depends on the crystallisation temperature. (MgPcH 2O) 2 · MEA ( I) and (MgPcH 2O) 2 · 2MEA ( II) were formed at about 170 °C and 80 °C, respectively, while room temperature (MgPcH 2O) 2 · 3MEA ( III) was obtained. In all crystals the Mg atom is 4+1 coordinated, equatorially by four N-isoindole atoms of Pc ligand and axially by O atom of water molecule. The MgPc moiety is non-planar, the Mg(II) deviates by ∼0.5 Å from the N 4-isoindole plane towards the oxygen atom of water molecule. The MEA molecules in the crystals interact via hydrogen bonds with coordinated water molecules of MgPcH 2O. The arrangement of MgPcH 2O and 2-methoxyethylamine molecules is determined by O–H⋯N and O–H⋯O hydrogen bonds and by π–π interactions. The thermogravimetric analyses show characteristic steeps responsible for the loss of MEA molecules (at lower temperature) and water (at higher temperature) and finally all the complexes transform into β-MgPc. From among the complexes only complex II exhibits an intense near-IR absorption band in the solid-state, while spectra in MEA solution are identical for all the complexes.

Synthesis, structural investigation and thermal stability of aqua magnesium(II) phthalocyanine bis(diethylamine) solvate

Aqua magnesium phthalocyanine bis(diethylamine) complex was obtained in the crystalline form and its crystal structure was determined by single-crystal X-ray diffraction. The Mg atom is 4 + 1 coordinated by four N isoindole atoms and one O atom. The MgPc moiety is non-planar, the Mg(II) is deviated by 0.492(2) Å from the N 4-isoindole plane towards the oxygen atom of water molecule. The arrangement of MgPc(H 2O) and diethylamine molecules is determined by O–H⋯N hydrogen bonds and π–π interactions. The complex is stable up to ∼140 °C. At this temperature the complex loses diethylamine molecules and next at ∼200 °C loses the water molecule and finally converts into β-MgPc.

Anomaly of the basicity of water in mixed solvents

Intermolecular interactions between water and N, N-dimethylformamide (DMF) in their mixtures were investigated by Raman spectroscopic and X-ray diffraction methods and by molecular orbital calculations. The Raman spectroscopic and X-ray diffraction measurements indicated the formation of water-DMF associates or clusters in the mixtures. Theoretical calculations for the electron density of H 2O-HOH-OH 2, ▪ of electron density on the oxygen atom of the water molecule in the DMF-HOH-DMF associate due to the accumulation of electrons transferred from DMF to the oxygen atom of the terminal water molecule. The increase resulted in a larger donicity of the terminal H 2O compared to normal water. Although the donor number D N of the water molecule in the DMF-H 2O-DMF associate was not determinable, it was estimated to be D N ∼ 30 from the behavior of the preferential solvation of the cobalt(II) ion in water-DMF mixtures.

Dipole Correlation of the Electronic Structures of theConformations of Water Molecule Evolving Through theNormal Modes of Vibrations Between Angular (C2v) to Linear(D∝h) Shapes

In order to settle the issue of equivalence or non-equivalence of the two lone pairsof electrons on oxygen atom in water molecule, a quantum chemical study of the dipolecorrelation of the electronic structure of the molecule as a function of conformationsgenerated following the normal modes of vibrations between the two extremeconformations, C2v (∠HOH at 90o) and D∝h (∠HOH at 180o), including the equilibrium one,has been performed. The study invokes quantum mechanical partitioning of moleculardipoles into bond moment and lone pair moment and localization of delocalized canonicalmolecular orbitals, CMO’s into localized molecular orbitals, LMO’s. An earlier suggestion,on the basis of photoelectron spectroscopy, that one lone pair is in p-type and the other is ins-type orbital of O atom of water molecule at its equilibrium shape, and also the qualitative“Squirrel Ears” structure are brought under serious scrutiny. A large number ofconformations are generated and the charge density matrix, dipole moment of eachconformation is computed in terms of the generated canonical molecular orbitals, CMO’sand then Sinanoğlu’s localization method is invoked to localize the CMO’s of eachconformation and the quantum mechanical hybridizations of all the bonds and lone pairs onO center are evaluated in terms of the localized molecular orbitals. Computed datademonstrate that the electronic structures i.e. two bond pairs and two lone pairs and itshybridization status of all conformations of water molecule are straightforward in terms ofthe LMO’s. It is further revealed that the pattern of orbital hybridization changescontinuously as a function of evolution of molecular shape. The close analysis of thegenerated LMO’s reveals that one lone pair is accommodated in a pure p orbital and anotherlone pair is in a hybrid orbital in almost all conformations. One more important result of the present study is that, with the physical process of structural evolution from close angular shape to the linear transition state, the length of the σ (O–H) decreases and its strength increases as a monotone function of reaction coordinates. The bond length is shortest and the strength is largest at the transition state of structural inversion. Result of structural effect of the present study during the evolution of molecular conformations is quite consistent with the result of a very refined calculation that one physically significant feature of force field that the stretching force constants at the linear geometry are considerably larger than their equilibrium counter parts. The variation of bond strength and the hybridization of s and p orbitals on O atom center to form the σ (O–H) bond as a function of evolution of conformations is in accordance with Coulson’s prediction. The total dipole moment of all conformations is partitioned into the contribution from bonds and lone pairs and correlated in terms of the computed hybridization in lone pairs. The analysis of the variation of dipole moment as a function of angular to linear structural evolution reveals that the dipole moment of H2O molecule is not due to the bond moments only but a significant contribution comes from a lone pair. It is strongly established that the dipole moment of water molecule at and around the equilibrium geometry is not due to the bond moments only and the major part of the molecular dipole comes from the contribution of lone pair electrons. This necessitates the accommodation of a lone pair of electrons in a hybrid orbital on O atom. The computed LMO’s webbed with partitioned molecular dipole reveal that one lone pair is in a pure p- type orbital and the other lone pair is in a hybrid of s and p, and not in a pure s type orbital as suggested on the basis of photoelectron spectra. The possibility of qualitative “Squirrel Ears” structure is also ruled out. The problem of equivalence or non-equivalence of the two lone pairs of the O atom in water seems to have been finally resolved by the present quantum chemical calculation. An attempt of locating the origin of barrier to the physical process of inversion of water molecule is made in terms of energy partitioning method. It is found that the dipole can be used as a descriptor for the elucidation of electronic structure of molecules.

Crystal and Molecular Structures of Barium cis(NO2)-trans(N)-Bis(glycinato)dinitrocobaltate(III) Hydrate [Ba(H2O)4][Co(Gly)2(NO2)2]2 · 1.43H2O

Crystals of [Ba(H2O)4][Co(Gly)2(NO2)2]2 · 1.43H2O (a=8.1917(6) A, b=8.4440(4) A, c=19.444(1) A, β=98.189(9)°, Z=2, space group P2/n) contain infinite strips of alternating axially symmetric [Ba(H2O)4]2+ fragments and two dinitro-bis(glycinato)cobaltate(III) ions. In addition to four oxygen atoms of water molecules, the nearest environment of Ba includes six oxygen atoms of the carboxyl groups of four anions, two of which are also coordinated by the cobalt atoms (Ba-O, 2.77–3.01 A). The nitrite ions do not interact with the Ba2+ ions.

Freezing Point of Mixtures of C6H6 with C6D6 or 13C6H6 and of CH3COOH with CH3COOD or CD3COOD

The freezing points of mixtures of benzene, C6H6, with one of its isotopes, C6D6 and 13C6H6, and those of acetic acid CH3COOH with its isotopes, CH3COOD and CD3COOD, were measured as functions of the molal concentrations of C6D6 and 13C6H6, CH3COOD and CD3COOD, respectively. They changed linearly or non-linearly with increasing molal concentration of C6D6 and 13C6H6, CH3COOD, and CD3COOD, respectively. These findings confirm Kiyosawa’s previous conclusion drawn from experiments on the freezing points of mixtures of H216O with H218O or H217O. This hypothesis states that even a difference in the number of neutrons in the hydrogen or oxygen atoms of water molecules makes water molecules behave as different entities with respect to the colligative properties of solutions. This concept can be extended to mixtures of ordinary benzene with either of its isotopes, C6D6 or 13C6H6, and those of ordinary acetic acid CH3COOH with either of its isotopes, CH3COOD or CD3COOD.

Freezing Point of Mixtures of H216O with H217O and Those of Aqueous CD3CH2OH and CH313CH2OH Solutions

The freezing point of mixtures of H216O with H217O was measured as a function of the molal concentration. The freezing points rose linearly with increasing molal concentration above that of pure ordinary water, H216O, at 273.15 K. This confirms Kiyosawa's previous conclusion [K. Kiyosawa, J. Solution Chem.20, 583 (1991).], drawn from findings on changes in the freezing point of mixtures of H216O with H218O or D216O that even a difference in the number of neutrons in the hydrogen or oxygen atoms of water molecules makes them behave as different entities with respect to the colligative properties of solutions. This has been confirmed to also occur in mixtures of H216O with H217O.

Synthesis, structure and spectroscopic properties of novel half-sandwich nickel(II) complexes with less hindered hydrotris(pyrazolyl)borate ligand

This paper presents the syntheses, crystal structures and spectroscopic properties of a series of half-sandwich nickel(II) complexes with hydrotris(3,5-dimethylpyrazolyl)borate and azide or thiocyanate, [Tp*Ni(pz)* 2(N 3)] ( 1), [Tp*Ni(pz*)(SCN)(H 2O)] ( 2) and [Tp*Ni(SCN)(CH 3OH) 2] ( 3) (Tp*: hydrotris(3,5-dimethylpyrazolyl)borate; pz*: 3,5-dimethylpyrazole). Compound 1 crystallizes in the triclinic system, P 1 ̄ space group (No. 2), a=10.2957(11) Å, b=11.5080(12) Å, c=13.6748(15) Å, α=81.993(2)°, β=72.999(2)°, γ=74.533(2)°, Z=2, R 1=0.0454, wR 2=0.1272. The nickel(II) ion in 1 is coordinated to six nitrogen atoms of Tp* and azide ion to form a distorted N 6 octahedron. The structure of 2 is roughly determined by X-ray crystal diffraction and shown two structurally independent [Tp*Ni(pz)(SCN)(H 2O)] units. The nickel(II) ion in 2 is six-coordinated to five nitrogen atoms of Tp*, pz*, thiocyanate and one oxygen atom of water molecule to form a N 5O octahedral environment. Compound 3 crystallizes in the monoclinic system, P2 1/ c space group, a=13.416(4) Å, b=11.964(3) Å, c=14.636(4) Å, β=96.195(5)°, Z=4, R 1=0.0379, wR 2=0.1079 . The coordination environment of nickel(II) ion in 3 is better to be described as the N 4O 2 octahedron made up of three nitrogen atoms of Tp*, one nitrogen atom of thiocyanate and two oxygen atoms of coordinated methanol molecules. The half-sandwich compound [Tp*Ni(η 2-O 2N)(CH 3OH)] 4 ( 4), which has been previously reported in a short communication, has the nickel(II) center with N 3O 3 coordination environment. The influences of N 3 −, SCN − and NO 2 − in all these half-sandwich nickel(II) complexes were discussed in this paper.

Detailed Molecular Model for Dielectric Constant of Multicomponent, Associating Liquids

We propose a new theory for relating the dielectric constant to the internal structure of association fluids containing any number of associating components, the molecules of which may possess any number of electron-rich and electron-deficient sites. The theory combines concepts proposed earlier by Kirkwood (1939) for describing dielectric behavior with more recent theoretical advances made in the area of associating fluids. The derived expressions account for correlations between all pairs of dipoles located within transient associated clusters of all possible sizes, molecular sequences, and shapes, the only exception being closed-ring structures. They reduce to known forms derived earlier using other methods for relatively simple systems, such as water, alcohols, and aqueous mixtures of alcohols and ketones. An application of the theory to the DMSO−water mixture suggests two modes of association between DMSO and water molecules (in addition to that between water molecules): (i) the oxygen atom of DMSO molecules associating with the protons of water molecules, as proposed by several workers in the recent past, and (ii) the oxygen atom of water molecules associating with the sulfur atom of DMSO molecules, as proposed originally by Tomilla and Murto (1963).

An analysis of bifurcated H‐bonds: crystal and molecular structures of O,O‐diphenyl 1‐(3‐phenylthioureido)­pentanephosphonate and O,O‐diphenyl 1‐(3‐phenylthioureido)butanephosphonate

AbstractIn the crystal structures of O,O‐diphenyl 1‐(3‐phenylthioureido)pentanephosphonate (1) and O,O‐diphenyl 1‐(3‐phenylthioureido)butanephosphonate (2) analysed here, bifurcated H‐bonds within R21(6) motifs are formed. It seems that such interactions play a crucial role in the crystal architecture. This is supported by ab initio MP2/6–311 ++ G** calculations on simple, modelled complexes of urea, thiourea and their derivatives with water, where the oxygen atom of water molecule is the bifurcated proton‐accepting centre. The calculations show that single H‐bonds within bifurcated systems are of medium strength (2.7–3.6 kcal mol−1). The topological parameters obtained from the Bader theory are applied for the analysis of these bifurcated H‐bonds. Copyright © 2003 John Wiley & Sons, Ltd.

Synthesis, crystal structure and spectroscopic properties of copper(II) complexes derived from 2-methylamino-5-pyridin-2-yl-1,3,4-oxadiazole

Two new complexes with the formulae [Cu(L)(oxalatoo)(H 2O)]·H 2O ( 1) and [Cu(L) 2(H 2O) 2](NO 3) 2 ( 2), where L=(C 8H 8N 4O)=2-methylamino-5-pyridin-2-yl-1,3,4-oxadiazole, have been synthesized and characterized. The structure of compound 1 contains monomeric entities in which the copper(II) ions exhibit five-coordinate square-pyramidal geometry. The oxadiazole bidentate ligand links to the metal ion through the N pyridine and one of the N oxadiazole atoms. Two oxygen atoms from the oxalato ligand complete the basal positions. The oxygen atom of a water molecule occupies the apical one. Solvation water molecules are also present in the lattice. The structure of compound 2 consists of monomeric distorted octahedral copper(II) species. The copper(II) ions are coordinated to both bidentate oxadiazole ligands in the equatorial plane, with the two oxygen atoms of both water molecules placed in the axial positions. Nitrate groups act as counterions. The presence of π–π stacking interactions interconnecting the monomeric entities in both complexes is discussed. The EPR spectra of compounds 1 and 2 show axial symmetries.

Synthesis, structural characterization of tetraazamacrocyclic ligand, five-coordinated zinc(II) complex

1,4,7,10-tetrakis(2-cyanoethyl-)-1,4,7,10-tetraazacyclododecane(L) and Zn (1), Y(2), Er(3), Pr(4), Gd(5) complexes with L was synthesized and characterized. All metal complexes are in the general formula: [M(L)(H 2O)](NO 3) 2 (M=Zn, n=1); and [M(L)(NO 3) 2]NO 3· mH 2O· nCH 3CN (M=Y, Er, m=5, n=0; M=Pr, Gd, m=0, n=1, 1.5). Both ionic nitrate ion and bidentate coordinated nitrate ions are existed in complex 2– 5. Structures of diprotonated L and zinc complexes were determined by X-ray diffraction. L was crystallized in diprotonated nitrate salt. In zinc complex, the central metal ion was coordinated with four nitrogen atoms of macrocyclic ligand and oxygen atom of water molecule, which defined a tetragonal pyramidal polyhedron. The bond lengths of ZnN are in the range of 2.160(5)–2.177(6) Å and the bond length of ZnO is 1.918(4) Å.

Kinetics of the oxidation of carbon black by NO 2: Influence of the presence of water and oxygen

In a fixed bed reactor, the rate of carbon black oxidation by NO 2 is significant for temperatures above 300°C, leading to NO, CO and CO 2 formation. The presence of O 2 in the feed gas increases the rate of oxidation, as well as the presence of water. A cumulative effect is observed when both water and oxygen are present. An oxygen balance shows that oxygen atoms of water molecules are not consumed. Water acts as a catalyst for the C–NO 2 reaction. A kinetic mechanism in which intermediate nitro-oxygenated species are formed in the presence of NO 2 during an initial step is in agreement with all these observations. Oxygen and NO 2 are able to react with these species at 300°C. A parametric study of the effects of the temperature, NO 2, O 2 and H 2O concentrations was performed. With a one-dimensional model of NO 2 consumption along the thickness of the carbon black bed, kinetic constants were derived and a phenomenological law was proposed, accounting for the effect of the presence of oxygen and water.

Extended network via hydrogen bond linkages of coordination compounds: synthesis, crystal structure and thermal behaviour of the complexes [M(L)2(NO3)2] (MII=Cu, Co) and [Ni(L)2(H2O)2][(NO3)2] (L=malonamide)

A series of monomeric complexes of general formula [MII(L)2(NO3)2] (MII=Cu, Co) (1), (2, 3), and [NiII(L)2(H2O)2][(NO3)2] (4) with L=malonamide have been isolated and characterized by single crystal X-ray structure. The crystalline structures for all compounds show multi-dimensional arrays or networks structures created by two types of hydrogen-bonding interactions. The first, between hydrogen atoms of the amide moiety and oxygen atoms of malonamide N-H(malonamide)⋯O(malonamide) forming two-dimensional arrays. The second type, between the hydrogen atoms of the amide moiety and the oxygen atoms of the nitrate molecules N-H(malonamide)⋯O(nitrate) generating three-dimensional arrangements. Nevertheless, for the Ni compound two contacts between the oxygen atoms of water molecules and oxygen atoms of nitrate moiety O(water)⋯O(nitrate) are present too. All the compounds have been characterized through thermogravimetric (TG) and calorimetric analyses (DSC).

Fractionation of hydrogen isotopes in crystal water of copper chloride dihydrate-saturated solution-water vapor system.

The D/H fractionation factors between the crystal water of copper chloride dihydrate and a saturated aqueous solution of copper(II) chloride, αCW-st.sol, and between the saturated aqueous solution and water vapor, αst.sol-V, were experimentally determined at 25°C in equilibrium. The observed values of αCW-st.sol and αst.sol-V, were 0.950 ± 0.002 and 1.052 ± 0.001, respectively. The D/H fractionation factor between the crystal water of copper chloride dehydrate and water vapor in equilibrium, αCW-V, was calculated to be 0.999 ± 0.002 from the observed values of αCW-st.sol and αst.sol-V, and is used to discuss D/H fractionation in crystal water of crystalline hydrates. It is shown that such D/H fractionation is better expressed by αCW-V than by the conventionally used fractionation factor between crystal water and mother liquor, αCW-st.sol, because αCW-V represents the activity ratio, whereas αCW-st.sol is simply the concentration ratio. Based on the results in this study, we consider that the coordination bond between divalent cupreous ions and oxygen atoms in water molecules and the hydrogen bond between crystal water and chlorine ions contribute substantially to the fractionation of hydrogen isotopes.