MOLECULAR DYNAMICS SIMULATIONS OF FILLED AND EMPTY CAGE-LIKE WATER CLUSTERS IN LIQUID WATER AND THEIR SIGNIFICANCE TO GAS HYDRATE FORMATION MECHANISMS

Molecular dynamics simulations are performed to observe the evolutions of 512 and 51262 cage-like water clusters filled with or without a methane molecule immersed in bulk liquid water at 250 K and 230 K. The lifetimes of these clusters are calculated according to their Lindemann index δ (t) using the criteria of δ≥0.07. For both the filled and empty clusters, we find the dynamics of bulk water determines the lifetimes of cage-like water clusters, and that the lifetime of 512 62 cage-like cluster is the same as that of 512 cage-like cluster. Although the methane molecule indeed makes the filled cage-like cluster more stable than the empty one, the empty cage-like cluster still has chance to be long-lived compared with the filled clusters. These observations support the labile cluster hypothesis on the formation mechanisms of gas hydrates.

Theoretical Study of Small Water Clusters of Sulfur Dioxide

The intermolecular clusters of sulfur dioxide with water, SO2（H2O）n （n = 2～5）, are studied by using B3LYP density functional theory and MP2 ab initio methods along with the large basis sets （6-311＋＋G（d,p） and aug-cc-pVDZ）. The equilibrium geometries, intermolecular binding energies, and anharmonic frequencies of the clusters are calculated and compared with those of pure water clusters and available experiments. SO2 tends to form cyclic hydrogen-bonded complexes with two or three water molecules. In the larger clusters, however, water molecules begin to retain the structure of pure water clusters and segregate from SO2. Infrared absorption assignments for the small clusters are discussed to resolve a possible incorrect assignment in a recent spectroscopic experiment on the clusters.

A Novel Zn(Ⅱ)Complex with 1D Supramolecular Water Tape Formed by Cyclic Tetrameric Water Clusters

A new mixed-ligand Zn（II） complex, [Zn（4,4′-bipy）2（H2O）4]-2ANS·6H2O （1, 4,4′- bipy = 4,4′-bipyridine, HANS = 2-aminonaphthalene-l-sulfonic acid）, has been isolated and structurally characterized by single-crystal X-ray diffwaction, FT-IR spectrum, TG and elemental analysis. It crystallizes in the monoclinic system, space group P2 1/c with a = 12.4852（8）, b = 18.3163（12）, c = 10.9707（7） A, β = 114.2600（10）°, V= 2287.3（3） A3, Dc = 1.455 g/cm3, Mr = 1002.37, Z = 2, F（000） = 1048,μ = 0.704 mm＂1, the final R = 0.0408 and wR = 0.962 for 4029 observed reflections with I 〉 2σ（I）. Interestingly, an unusual one-dimensional （1D） water tape with cyclic tetrameric water clusters can be observed in 1, which are further trapped via Zn-O coordination bonds exhibiting a 2D Zn（Ⅱ）-water layer. These 2D Zn（Ⅱ）-water layers are stacked together into a 3D interdigitated supramolecular architecture via weak π…π interactions, in which free ANS anions are tightly filled by hydrogen-bonding interactions. Thus, π…π and classical hydrogen-bonding interactions are fotmd as main driving forces to stabilize the 2D Zn（Ⅱ）-water layers.

Pseudopolyrotaxanes of Cucurbit[6]uril： A Three-Dimensional Network Self-assembled by ClO4（H2O）2 Water Clusters

A pseudorotaxane of cucurbit[6]uril （CB[6]） with guest molecule N,N＇-hexamethylenebis （pyrazinyl perehlorate） （BPHP） was synthesized and characterized by IH NMR spectra, IR, single crystal X-ray diffraction analysis and thermogravimetric analysis. The structure of the pseudorotaxane （CB[6]BPHP） is stabilized by host-guest hydro- gen bonds. Self-assembly of the pseudorotaxane produces infinite one-dimensional and two-dimensional networks with intermolecular hydrogen bonds. In the molecular packing of the CB[6].BPHP, C104（H20）2 water clusters serve as bridges to associate these pseudorotaxanes and form three-dimensional networked pseudopolyrotaxane.

Halide-Anion Water Clusters in Cucurbit[6]uril Supramolecular Systems

Three types of dihalide water clusters [X2（H20）8]2 （X=Cl, Br） and [I2（H20）10]^2- have been observed in cucurbit[6]uril supramolecular systems with same guest. According to the single crystal data and the quantitative theory computation, with the increase of electronegativity of halide ions, dihalide water clusters become more stable. A further comparison of three kinds of guests with different molecule length but the same anions, [p-phenylenediamine salt, hexamethylenediamine salt and N,N＇-hexamethylenebis（pyrazinylbromide）], gives the result that the dihalide water clusters collapse from 2D to 1D with the increase of the lengths.

Hydrogen Bond Cooperative Effect in Single Cage Water Clusters

In this paper,DFT method was used to study the relative stability of hydrogen bonding networks of numerous 512,51262 and 435663 water cluster isomers.Herein we introduced an optimized six-digit definition to characterize diverse sub-grouped hydrogen bonds to consider the cooperative effect of the nearest and nextnearest neighbor water molecules.There are totally 74 kinds of sub-grouped hydrogen bonds in cage hydrate clusters,and these energies can be obtained by iterative calculations.This improvement effectively explains some regularity contained in hydrogen bonding cooperative effect.In general,donor or acceptor fragment sharing identical value of three independent digits usually performs poor cooperative effect,indicating that the existence of those same-digital-array fragments is the necessary condition to judge poor cooperative effect.Vice versa,the existence of different-digital-array is also the necessary condition to judge strong cooperative effect.

Computer study of the formation of water-ammonia clusters and their dielectric properties

The absorption of one to six ammonia molecules by the （H2O）50 cluster is studied by the molecular dynamics method under near-atmospheric conditions. The capture of NH 3 molecules by a water cluster produces an increase in the integrated intensity of IR absorbance, substantially decreases emission power in the frequency range of 0≤ω≤3500cm-1,and transforms a continuous reflectance spectrum into a banded one. Adsorption of ammonia molecules by water clusters greatly diminishes the number of electrons that are active with respect to electromagnetic radiation. The present results are also compared with the experimental findings wherever available.

Synthesis,Crystal Structure and Photoluminescent Property of a Novel Dy^(3+) Coordination Compound Containing Rare(H_2O)_(22) Clusters

A novel Dy^（3＋） coordination compound,（H_2pipz）（H_3O）[Dy（pydc）_3]·11H_2O（1,pipz = piperazine and H_2pydc = pyridine-2,6-dicarboxylic acid）,has been hydrothermally synthesized and characterized by X-ray single-crystal diffraction,elemental analysis. It is interesting that the packing structure of compound 1 contains 22-core water clusters. Compound 1 is extended into a threedimensional supramolecular structure via O···H···O hydrogen bonding interactions. Furthermore,the luminescent property of compound 1 was also investigated.

The Gravito-Chemical Bond and Structures of Hydrocarbons and Water Molecules with Real Magnetic Charges

Experimental and theoretical studies of the author (period: 1968-present) have shown that true sources of the magnetic field are magnetic fundamental particles (magnetic charges), and not moving electrons. The main reason for ignoring real magnetic charges, as well as true antielectrons in physical science is the hard conditions for confinement of these particles in atoms and substances, which is radically different from the confinement of electrons. Magnetic charges together with electric charges form the shells atoms which are electromagnetic, and not electronic. Namely, electromagnetic shells are sources of gravitational field which is a vortex electromagnetic field and described by the vortex rot [E - H]. Depending on the state polarization of vortex vectors rot [E - H] in compositions of atomic gravitational fields it is subdivided into paragravitational (PGF) and ferrogravitational fields (FGF). The overwhelming number of atoms emits PGF. Between the masses (bodies, atoms, nucleons and others) emitting PGF areas of negative gravitational “Dark Energy” are realized the forces of which press the masses towards each other. Namely, the compression of atoms by the forces of paragravitational “Dark Energy” underlies the chemical bond. The exception here is the ionic bond in ionic crystals. However, all ions have electromagnetic shells that generate the gravitational field. Consequently, ionic bonding is a relatively rare addition to gravito-chemical bond processes. The direct gravito-chemical bond of carbon atoms with hydrogen (1H) is physically forbidden due to the manifestation of the effect of ferrogravitational levitation between them and the repulsion of atoms from each other. Paradoxically, but all existing ideas about the structural device of hydrocarbons are based on such physically forbidden bonds which, moreover, must be realized through ionic bonds which in reality do not exist. Chemical bonding of carbon and hydrogen atoms to form hydrocarbons molecules is possible only if the hydrogen atoms are in the molecular form (1H2). In the composition of water, within the framework of the chemical formula H2O, two stable isomorphic molecular structures are formed. The chemical bond in the first structure is similar to the hydrocarbon scenario described above, i.e. in the process of combining paragravitational oxygen with a hydrogen molecule 1H2. The second molecular structure in water is formed under conditions of ferropolarization of the gravitational field of oxygen atoms under the influence of FGF of neighboring 1H atoms. In this case, the chemical bond is realized under the conditions of ferropolarization of the vortex vectors rot [E - H] of the gravitational fields of all atoms in the molecule and the co-directionality of them vectors Pfp ferropolarization. The gravito-physical properties of the presented molecular structures in the composition of water make it possible to name them, respectively, as heavy and light clusters.

Hydrothermal Synthesis,Crystal Structure and Thermal Stability of a Novel Water Cluster [Mn(phen)_2·H_2O·Cl]·p-FBA·3H_2O

A novel water cluster [Mn（phen）2·H2O·Cl]·p-FBA·3H2O （p-FBA = p-fluorobenzoic acid and phen = 1,10-phenanthroline） was synthesized by the hydrothermal reaction of MnCl2 with p-FBA and phen at 150 ℃ and characterized by elemental analysis,IR spectra and TG. Its crystal structure was determined by X-ray single-crystal diffraction study. The crystal belongs to the triclinic system,space group P1,with a = 10.5768（1）,b = 11.5960（1）,c = 12.9916（2） ,α = 101.816（2）,β = 95.397（2）,γ = 103.052（2）o,V = 1502.8（3） 3,Z = 2,Dc = 1.463 g/cm3,R = 0.0399 and wR = 0.0997. The crystal structure shows that the manganese（Ⅱ ） ion is six-coordinated by four nitrogen atoms,one chloride ion and one oxygen atom forming a distorted octahedral coordination geometry. The structure includes three acyclically connected water molecules and one coordinated water molecule thus forming a （H2O）4 water cluster. This water pattern forms a cross-linked discrete ring. The steady （H2O）4 is further extended into a cage-like structure by the hydrogen-bonding interaction formed by dissociative aqua molecule and Cl-ligand. The dimer structure is further extended into a one-dimensional （1D） structure through C-H···O interaction. π···π Stacking interaction among adjacent phen aromatic rings further stabilizes the crystal structure.

Unprecedented Pseudo Water Tapes Stabilized by a One-dimensional Cu(Ⅱ) Coordination Polymer

A new compound,[Cu（mal）（tmdpy）（H2O）]·4H2O（1,H2mal = malonic acid,tmdpy = 4,4＇-trimethylenedipyridine） has been synthesized by the hydrothermal synthesis and structurally characterized by X-ray crystallography. It crystallizes in triclinic,space group P1^- with a = 9.1662（6）,b = 10.6266（7）,c = 11.3056（7）A,α = 84.6390（10）,β = 72.1030（10）,γ = 73.0420（10） o,V = 1002.37（11）A^3,C16H26CuN2O9,Mr = 453.93,Z = 2,Dc = 1.504 g/cm^3,μ = 1.140 mm^-1,F（000） = 474,R = 0.0375 and wR = 0.0975 for 3187 observed reflections（I 〉 2σ（I）） . In the structure of 1,the tmdpy ligands link the [Cu（mal）（H2O） ] units into an infinite chain,and the water molecules and carboxylate oxygen donors（O（2） and O（4）） from the mal ligands cooperatively built an interesting hydrogen bonding network with unprecedented pseudo water tape substructures.

A Novel Three-dimensional Mn(Ⅱ) Coordination Polymer Constructed from Biphenyl-3,3',5,5'-tetracarboxylic Acid and Water

The title Mn（Ⅱ） coordination polymer,poly{[heptaaqua-（μ4-bi-phenyl-3,3？,5,5？-tetracarboxylate）-bimanganese（Ⅱ）] pentahydrate},[Mn_2（bpta）（H_2O）_7]_n·5n H_2O（I）,is crystallized from a mixture of biphenyl-3,3？,5,5？-tetracarboxylic acid（H_4bpta） and MnCl_2·4H_2O in waterethanol under room temperature. Its asymmetric unit consists of one and two halves of crystallographically independent Mn（Ⅱ） cations,one fully deprotonated H4 bpta ligand,seven coordinated water molecules and five solvent water as guest molecules. In I,each Mn（Ⅱ） atom is octahedrally coordinated by six oxygen atoms from bpta^（4-） anions and coordinated water molecules. In the Mn（Ⅱ） cations,one half Mn（Ⅱ） ion of them located at a 2-fold axis generating a trinuclear [Mn_3（H_2O）_2（RCOO）_2] linker by μ1,1-O（water） and μ1,3-O,O？（carboxylate） bridges and another half Mn（Ⅱ） ion with an inversion is a mononuclear linker. These neighbouring trinuclear and mononuclear Mn（Ⅱ） cations are linked together by biphenyl-3,3？,5,5？-tetracarboxylates to form a three-dimensional framework with a（42.84） topology of a（4,4）-connected net,in which the positions of the trinuclear [Mn_3（H_2O）_2（R-COO）_2] linker as a 4-connector linking four bpta^（4-） ligands in I reproduce an eagle-shaped arrangement. The polymeric structure exhibits a water channel with an accessible void of 797.1 ？~3,amounting to 15.7% of the total unit-cell volume. Each of the cavities in the network is occupied by solvent water molecules.

Identification of coastal water quality by multivariate statistical techniques in two typical bays of northern Zhejiang Province,East China Sea

The Hangzhou Bay（HZB） and Xiangshan Bay（XSB）, in northern Zhejiang Province and connect to the East China Sea（ECS） were considerably affected by the consequence of water quality degradation. In this study, we analyzed physical and biogeochemical properties of water quality via multivariate statistical techniques. Hierarchical cluster analysis（HCA） grouped HZB and XSB into two subareas of different pollution sources based on similar physical and biogeochemical properties. Principal component analysis（PCA） identified three latent pollution sources in HZB and XSB respectively and emphasized the importance of terrestrial inputs, coastal industries as well as natural processes in determining the water quality of the two bays. Therefore, proper measurement for the protection of aquatic ecoenvironment in HZB and XSB were of great urgency.

Definition of water exchange zone between the Bohai Sea and Yellow Sea and the effect of winter gale on it

The marine dynamic environment of the Bohai Sea and the Yellow Sea in the winter of 2006 is simulated by the Regional Ocean Modelling System（ROMS） marine numerical model. Using the simulated temperature and salinity, the water exchange zone between the Bohai Sea and Yellow Sea is defined through the Spectral Mixture Model（SMM）. The influence of winter gales on the water exchange is also discussed. It is found that the Yellow Sea water masses in winter are distributed in a ＂tongue＂ shape in the Bohai Strait region, the water exchange zone presents a zonal distribution along the margin of the ＂tongue＂, with a tendency of running from northwest to southeast, and the water exchange is intensified at the tip of the ＂tongue＂. Besides, the coastal area in the northernmost Yellow Sea does not participate in the water exchange between the Bohai Sea and Yellow Sea. The result shows that the winter gale events play a role in enhancing the water exchange. It is specifically shown by the facts： the Yellow Sea warm current is enhanced to intrude the Bohai Sea by the gale process; the water exchange zone extends into the Bohai Sea; the water exchange belt in the southern part becomes wider; the mixture zone of river runoff with the Bohai Sea water upon its entry is enlarged and shifts northwards. Within two days after the gale process, the exchange zone retreats toward the Yellow Sea and the exchange zone resulted from the Huanghe River（Yellow River） runoff also shrinks back shoreward.

Two Nickel(Ⅱ) Complexes Constructed by Novel Bis(3-methoxy-2-pyridyl)ether-6,6′-dicarboxylic Acid Ligand:Lattice Water Control of Structure

Under given conditions, two complexes of [Ni（H20）2BEDA]·2H2O 1 and [Ni（Py）2- BEDA]·6H2O 2 （BEDA = bis（3-methoxy-2-pyridyl）ether-6,6′-dicarboxylic acid） have been synthesized and characterized by elemental analysis and X-ray single-crystal diffraction. Crystal data for 1： C14H18NiN2O11, monoelinic C2/c, a = 14.3844（17）, b = 12.9900（15）, c = 9.6309（11） A, β = 104.3350（10）°, V= 1743.5（4） A3, Z = 4, Dc= 1.711 g/cm^3, F（000） = 928, μ = 1.179 mm^-1, Mr= 449.01, the final R = 0.0228 and wR = 0.0625. Crystal data for 2： C24H32NiN4O13, triclinic P1, a = 9.423（2）, b = 11.863（3）, c = 13.089（3） A, α = 91.511（3）, β = 92.465（3）, γ = 100.696（2）°, V = 1435.6（6） A^3, Z = 2, Dc= 1.488 g/cm^3, F（000） = 672, μ = 0.748 mm^-1, Mr= 643.25, the final R = 0.0400 and wR = 0.0975. Interestingly, in the two complexes, lattice water molecules dominate its crystal structures. Therefore, extensive intermolecular hydrogen bonds assemble 1 and 2 into 2D extended sheets and a 3D open framework, respectively. Furthermore, water molecules present in 2 are associated to form water clusters.

Density Functional Theory Study of Water Diffusion and Clustering on Pd(111)

The internal structures as well as adsorption and hopping energies of monomers, dimers, trimers, tetramers, pentamers and hexamers of water on Pd（111） have been studied by density functional theory （DFT） plane-wave pseudopotential method which performs the firstprinciples quantum-mechanical calculations to explore the properties of crystals and surfaces in materials. Based on the calculations, we suppose that their absorption is via one water molecule for monomers, dimmers and trimers, but three water molecules for pentamers and hexamers. Moreover, there is one water molecule bonding with Pd atom by O atom in pentamers and hexamers, which explains why pentamers and hexamers are stable. The binding energies of polymers may be used to explain why the trimer comes close to two nearby monomers to form a stable pentamer instead of tetramer. And the difference of mobility of small water clusters is due to their different hopping energies.

Computer study of the spectral characteristics of the disperse water methane system

The interaction of water clusters that adsorbed methane molecules with infrared radiation is studied by molecular dynamics. The presence of methane molecules in the disperse water system leads to an increase in absorption and emission of infrared radiation and a strong depletion of the Raman spectrum. In this case, the reflection coefficient of a monochromatic plane electromagnetic wave increases and its frequency spectrum significantly changes. The comparison of experimental data for similar characteristics of water, methane, or their mixtures is presented.

Exploration of the Existence Forms and Patterns of Dissolved Oxygen Molecules in Water

The structure of liquid water is primarily composed of three-dimensional networks of water clusters formed by hydrogen bonds,and dis-solved oxygen is one of the most important indicators for assessing water qual-ity.In this work,distilled water with different concentration of dissolved oxygen were prepared,and a clear negative correlation between the size of water clus-ters and dissolved oxygen concentration was observed.Besides,a phenomenon of rapid absorption and release of oxygen at the water interfaces was unveiled,suggesting that oxygen molecules predominantly exist at the interfaces of water clusters.Oxygen molecules can move rapidly through the interfaces among water clusters,allowing dissolved oxygen to quickly reach a saturation level at certain partial pressure of oxygen and temperature.Further exploration into the mechanism by molecular dynamics simulations of oxygen and water clusters found that oxygen molecules can only exist stably at the interfaces among water clusters.A semi-empirical formula relating the average number of water molecules in a cluster(n)to ^(17)O NMR half-peak width(W)was summarized:n=0.1 W+0.85.These findings provide a foundation for exploring the structure and properties of water.

Synthesis and Crystal Structure of a Ternary Complex:[Ni(phen)_2(pmal)]·8H_2O

A new ternary complex [Ni（phen）（pmal）]·8H2O （phen = 1,10-phenanthroline, pmal^2- = phenethyl malonic acid） has been synthesized by the reaction of nickel acetate, phen and phenethyl malonic acid. Elemental analysis, IR spectra and X-ray single-crystal diffraction were carried out to determine the composition and crystal structure. Crystal data for this complex： triclinic system, space group PI^-, a = 10.387（5）, b = 13.112（6）, c = 14.229（6） °A, α= 76.176（7）, β = 83.778（8）, γ = 71.770（6）°, C35H42N4O12Ni, Mr= 769.44, Z = 2, F（000） = 808, V = 1786.1°A^3, Dc = 1.431 g/cm^3,μ= 0.612 mm^-1, the final R = 0.0653 and wR = 0.1033 for 9379 （Rint = 0.0244） independent reflections and 4730 observed reflections （I〉 2σ（I））. Structural analysis shows that the coordination geometry of Ni（Ⅱ） is a distorted octahedron. A novel two-dimensional structure is constructed from （H2O）4 and （H2O）12 water clusters, and the complex forms a 3-D network supramolecular structure by hydrogen bonds and π-π stacking of neighboring phens.

Density functional study on chirospectra of hydrogen-bonded systems X^-(H_2O)_3(X=F,Cl,Br,I)

This paper calculates the molecular structures, infrared, Raman, circular dichroism spectra and optical rotatory powers of some hydrogen-bonded supramolecular systems as a cyclic water trimer, （H2O）3 and its pyramidal halide complexes, X- （H2O）3 （X= F, Cl, Br, I） with the gradient-corrected density functional theory method at the B3LYP/6- 311＋＋G（2d,2p） and B3LYP/Aug-cc-pVTZ levels. It finds that the complexation of halide anions with the water trimer can efficiently modulate the chirally optical behaviors. The calculated vibrational circular dichroism spectrum illuminates that the vibrational rotational strength of S（＋） （H2O）3 mostly originates from the O-H rocking modes, whereas chirality of S（-）-X-（H2O）3 （X = F, Cl, Br, I） has its important origin in the O-H stretching modes. The calculated optical rotatory power demonstrates that S（＋） （H2O）3 and S（＋）-F-（H2O）3 are positively chiral, whereas S（-）-X-（H2O）3 （X=Cl, Br, I） are negatively chiral. With the polarizable continuum model, calculated bulk solvent effect in the solvents water and carbontetrachloride and argon shows that the positive chirality of S（＋）-（H2O）3 is enhanced and the negative chirality of S（-）-X-（H2O）3 （X=Cl, Br, I） and the positive chirality of S（＋）-F-（H2O）3 are reduced with an augmentation of the solvent dielectric constant.