Cyclic Water Clusters Research Articles

All-body concept and quantified limits of cooperativity and related effects in homodromic cyclic water clusters from a molecular-wide and electron density-based approach.

We strongly advocate distinguishing cooperativity from cooperativity-induced effects. From the MOWeD-based approach, the origin of all-body cooperativity is synonymous with physics- and quantum-based processes of electron (e) delocalization throughout water clusters. To this effect, over 10 atom-pairs contribute to the total e-density at a BCP(H,O) between water molecules in a tetramer. Intermolecular all-body e-delocalization, that is, cooperativity, is an energy-minimizing process that fully explains non-additive increase in stability of a water molecule in clusters with an increase in their size. A non-linear change in cooperativity and cooperativity-induced effects, such as (i) structural (e.g., a change in d(O,O)) or topological intra- and intermolecular properties in water clusters (e.g., electron density or potential energy density at bond critical points) is theoretically reproduced by the proposed expression. It predicted the limiting value of delocalized electrons by a H2O molecule in homodromic cyclic clusters to be 1.58e. O-atoms provide the vast majority of electrons that "travel throughout a cluster predominantly on a privileged exchange quantum density highway" (⋅⋅⋅O-H⋅⋅⋅O-H⋅⋅⋅O-H⋅⋅⋅) using Bader's classical bond paths as density bridges linking water molecules. There are, however, additional electron exchange channels that are not seen on molecular graphs as bond paths. A 3D visual representation of the "privileged" and "additional" exchange channels as well as detailed intra- and inter-molecular patterns of e-sharing and (de)localizing is presented. The energy stabilizing contribution made by three O-atoms of neighboring water molecules was found to be large (-597 kcal/mol in cyclic hexamer) and 5 times more significant than that of a classical O-H⋅⋅⋅O intermolecular H-bond.

A computational study of H-bonded networks in cyclic water clusters, (H2O)n (n = 3-12).

We have performed a detailed MM and DFT investigation of neutral water clusters (H2O)n (n = 3-12). Our results show the trend of interaction energies in these clusters as a function of the size of the cluster. They show that the H-bond strength increases with cluster size and that the model of water is better described if two different partial charges are used on the hydrogen, depending on whether hydrogen is H-bonded or not. The average binding enthalpy change due to the formation of H-bonds between water molecules is found to be - 25.9kJmol-1 at B3LYP/aug-cc-pVDZ level of theory. We observe the formation of cyclic H-bonded networks through the analysis of frontier orbitals and IR vibrational frequencies spectra. For the water cluster with n = 11, we observe an unusual reduction of the bandgap indicative of a cyclic H-bonded network. Calculations were performed with the MMFF94 force field and the B3LYP method using various large basis sets. Molecular orbital diagrams and population analysis were done using standard tools in Gaussian.

The strength of the OH-bend/OH-stretch Fermi resonance in small water clusters.

A novel Raman jet-spectrometer is used to study the Fermi resonance between the OH bending overtone and OH stretching fundamental in small cyclic water clusters (H2O)n with n = 3, 4, 5. The new setup features a recirculating vacuum system which reduces the gas consumption by 2 to 3 orders of magnitude and enables long-term measurements of very weak Raman signals. Raman spectra measured from highly diluted expansions with unprecedented signal-to-noise ratio are presented and cluster-specific intensity ratios and effective coupling constants are derived using Markov-Chain Monte-Carlo methods, yielding a high probability for an almost "perfect" resonance for the tetramer and pentamer, i.e. a close frequency match of bend overtone and stretch fundamental with intensity ratios close to 1, but a larger coupling constant for the trimer, with best estimates close to W5 ≲ 50 cm-1 < W4 ≲ 60 cm-1 < W3 ≈ 65 cm-1.

Insight into the Binding of Argon to Cyclic Water Clusters from Symmetry-Adapted Perturbation Theory.

This work systematically examines the interactions between a single argon atom and the edges and faces of cyclic H2O clusters containing three-five water molecules (Ar(H2O)n=3-5). Full geometry optimizations and subsequent harmonic vibrational frequency computations were performed using MP2 with a triple-ζ correlation consistent basis set augmented with diffuse functions on the heavy atoms (cc-pVTZ for H and aug-cc-pVTZ for O and Ar; denoted as haTZ). Optimized structures and harmonic vibrational frequencies were also obtained with the two-body-many-body (2b:Mb) and three-body-many-body (3b:Mb) techniques; here, high-level CCSD(T) computations capture up through the two-body or three-body contributions from the many-body expansion, respectively, while less demanding MP2 computations recover all higher-order contributions. Five unique stationary points have been identified in which Ar binds to the cyclic water trimer, along with four for (H2O)4 and three for (H2O)5. To the best of our knowledge, eleven of these twelve structures have been characterized here for the first time. Ar consistently binds more strongly to the faces than the edges of the cyclic (H2O)n clusters, by as much as a factor of two. The 3b:Mb electronic energies computed with the haTZ basis set indicate that Ar binds to the faces of the water clusters by at least 3 kJ mol-1 and by nearly 6 kJ mol-1 for one Ar(H2O)5 complex. An analysis of the interaction energies for the different binding motifs based on symmetry-adapted perturbation theory (SAPT) indicates that dispersion interactions are primarily responsible for the observed trends. The binding of a single Ar atom to a face of these cyclic water clusters can induce perturbations to the harmonic vibrational frequencies on the order of 5 cm-1 for some hydrogen-bonded OH stretching frequencies.

Water clusters in liquid organic matrices of different polarity

The cluster structure of water is continuously a subject of intense scientific discussion. Because of the electronic and structural characteristics, the experimental studies still present a great challenge. In this work, the water clusters formed in organic liquid matrices of different polarities are studied. Various chlorine hydrocarbons differing in dipole moment were used as dispersing media, namely: carbon tetrachloride, chloroform, dichloromethane and 1,2-dichloroethane. Simple infrared absorption spectroscopy combined with Molecular Dynamics simulations and Density Functional Theory calculations were found to be a very effective tool for the precise determination of the water cluster structure. For the first time, the correlation between experiments and computations is presented at this level of accuracy. The main results show that a higher polarity of the organic matrix favours the formation of stable, small, and cyclic water clusters, while in the nonpolar matrix water molecules tend directly to phase separation on the macroscopic scale. Moreover, the size of the clusters formed by water molecules strongly depends on the water content in the matrix.

Syntheses, Structural Insight and HirshFeld Surface Analysis of Two Heteroleptic Coordination Polymer of Cu(II)

Using a solvothermal method, we have synthesized two coordination polymers of Cu(II). One is a 1D polymer {[Cu(bpy)(NDC)(H 2 O)].2H 2 O} n (1, 1D) formed with 1,8-naphthalene dicarboxylic acid (H 2 NDC) and 2,2′ -bipyridine (bpy) as an auxiliary ligand, while the other is a 2D polymer {[Cu 3 (TMA)(Imd) 3 ].5H 2 O.2DMF} n (2, 2D) formed with trimellitic acid (H 3TMA) and imidazole (Imd) as an auxiliary ligand. Both coordination polymers 1 and 2 were formed through an in situ hydrolytic ring opening reaction of 1,8-naphthalic anhydride and trimelitic anhydride with bipyridine and imidazole ligands, respectively. The asymmetric unit of polymer 1 contains asymmetric η 1 binding mode (one of the carboxylate) linking distorted square-pyramidal [Cu(NDC)(bpy)(H 2 O)] 2+ coordination units. The syn-syn-η 1 :η 1 linear polymer conformation exist in the 1D coordination polymer with adjacent Cu…Cu distance is 6.849Å. A chain of cyclic tetrameric water clusters is present between the stacked layers of the 3D supramolecular structure. The formation of the 3D supramolecular structure is guided by various weak interactions such as OH…O, CH…O, CH…π and π…π interactions. The coordination polymers 2 forms 3D supramolecular architecture guided by various weak interactions such as OH…O, CH…O and NH…O interactions. The crystal structures of both coordination polymers have been determined using single crystal X-ray diffraction and their structural features are described.

Photocatalytic activity of MoS2 with water monolayers: Global optimization.

Atomically thin MoS2 has emerged to be promising for photocatalytic water splitting benefiting from its suitable geometrical and electronic structure for light harvesting. A better understanding of how water molecules affect the band edge levels of MoS2 is critical for promoting the interfacial reactivity. Here, we determine the structures of water monolayers on MoS2 using global optimizations achieved by molecular dynamics in combination with local minimization. It is shown that cyclic water clusters are formed on a surface through a hydrogen-bonding network. The absolute band edge positions are explored taking into account the derivative discontinuity of the exchange-correlation functional. Shifts in band edges are observed with the increase in H2O coverage, while bandgaps tend to be slightly decreased. In particular, the band alignment relative to water redox potentials has been investigated in detail. We find that the dimer configuration is likely to suppress the hydrogen evolution reaction (HER), while the polygon clusters lift the conduction band by 0.2-0.7eV, and thus, they would enhance HER. This effect is explained in terms of the linear dependence of the band edge offset on an interface electric dipole arising from water assemblies.

Terephthalato and succinato bridged Mn(II) and Zn(II) coordination polymers involving structure-guiding H-bonded tetrameric assemblies: Antiproliferative evaluation and theoretical studies

Two new coordination polymers of Mn(II) and Zn(II) viz. {[Mn(µ-tp)(3-Ampy)2(H2O)2]2(3-Ampy)·2(H2O)}n (1) and {[Zn(µ-succ)(3-Ampy)2]·2H2O}n (2) (tp = terephthalate, 3-Ampy = 3-aminopyridine, succ = succinate) have been synthesized and characterized using elemental and spectroscopic analyses, TGA and single crystal X-ray diffraction techniques. Uncoordinated 3-AMpy and water molecules of the polymeric co-crystal hydrate 1 are involved in the formation of cyclic tetrameric {(3-Ampy)2(H2O)2} assembly which provide rigidity to the structure. The presence of guest 3-Ampy and water molecules in the voids of supramolecular Mn(II) host tetramer in 1 provides additional reinforcement to the crystal structure. The lattice water molecules of 2 are aggregated via non-covalent interactions to form discrete cyclic {(H2O)4} tetrameric clusters in the crystal structure. Density functional theory (DFT), non-covalent index (NCI) plot and quantum theory of atoms in molecules (QTAIM) computational analyses reveal that the supramolecular H-bonded cyclic tetrameric structure-guiding synthon in 1 and the (H2O)4 cyclic water clusters in 2 have significant energetic contribution towards the stability of the polymers. In vitro anticancer activities of the compounds considering trypan blue and apoptosis assays revealed that the compounds induce concentration dependent cytotoxicity in Dalton’s lymphoma (DL) cancer cells with nominal effects in normal peripheral blood mononuclear cells (PBMC) cells. Comparative analysis reveals that compound 2 induced higher apoptosis in DL cells; which is well consistent with the trypan blue exclusion assay. Molecular docking and pharmacophore modelling studies of the compounds reveal that the compound 2 significantly interacts with the antiapoptotic proteins to establish structure activity relationship (SAR).

Beyond energetic and scalar measures: Next generation quantum theory of atoms in molecules

AbstractNext generation quantum theory of atoms in molecules (NG‐QTAIM) is currently the only vector‐based quantum chemical theory as all other quantum chemical theories are scalar‐based. NG‐QTAIM can, for instance, be used to distinguish enantiomers, isotopomers undergoing normal modes of vibration, predict ring‐opening reaction products, ground and excited states at a conical intersection and predict reaction pathways of permutation‐inversion isomers. As a consequence, NG‐QTAIM can uniquely be used to investigate iso‐energetic phenomena where the reliance on differences in geometric measures is removed. NG‐QTAIM has already been used to determine molecular chirality consistent with the Cahn–Ingold–Prelog (CIP) classifications for chiral molecules in addition to the reactant and product of a chiral SN2 reaction. The CIP classifications however, cannot quantify the chirality of intermediate reaction structures due to their formally achiral nature. We identify the presence of chirality by quantifying a helical response of the bond electrons consistent with photoexcitation circular dichroism experiments that utilize the helical motion of the bound electrons for chiral discrimination. NG‐QTAIM can also be used to provide nongeometric based reasoning as to why there are stronger hydrogen‐bonds in cyclic water clusters compared with compact water clusters. Additionally, the effects of electric‐fields and laser irradiation in conditions not amenable to explanation using scalar measures are quantified. The QuantVec software is introduced, which coordinates external programs and efficiently computes the NG‐QTAIM analyses using the wavefunctions from a wide range of ground and excited states computed with DFT, coupled‐cluster, complete active space SCF, configuration interaction, or quantum dynamics methods.This article is categorized under: Structure and Mechanism &gt; Molecular Structures Structure and Mechanism &gt; Reaction Mechanisms and Catalysis Software &gt; Quantum Chemistry

Crystal structure of [Rh2(μ-OAc)2(μ-HNOCCF3)2(theophylline)2]·6H2O. Metal bonding to theophylline at the unexpected N(9) site due to the crystal packing effect and a review on intra-molecular interligand interactions affecting metal bonding properties of theophylline

• Crystal structure of a dinuclear Rh 2+ complex of theophylline was determined. • The Rh‒Rh core is occupied at either axial-side by theophylline ligands through N9. • Metal bonding not to expected N7 but to N9 is due to the crystal packing effect. • A discrete, cyclic hexameric water cluster intercalates between theophylline rings. • Metal binding sites of theophylline are reviewed in terms of interligand interaction. Reaction of theophylline with [Rh 2 (μ-OAc) 2 (μ-HNOCCF 3 ) 2 ] gave [Rh 2 (μ-OAc) 2 (μ-HNOCCF 3 ) 2 (theophylline) 2 ]·6H 2 O ( 1 ), whose crystal structure was determined by single-crystal X-ray diffraction. The dirhodium core, where the two different acetato and acetamidato ligands bridging the Rh‒Rh bond are in a trans configuration, is occupied at either axial-side by two theophylline ligands through N(9) with the formation of two kinds of intra-molecular interligand C−H (theophylline)···O hydrogen bonds, one being a bifurcated hydrogen bond between the C(3)-methyl hydrogen as a donor and the acetato and amidato oxygens as acceptors and the other between the C(8) hydrogen and the acetato oxygen. In the crystal lattice, a discrete, hydrogen-bonding, cyclic hexameric water cluster with the flattened chair conformation is sandwiched between theophylline bases, providing the first water hexagon that intercalates between aromatic rings. The participation of the acetamidato NH group in the formation of a hydrogen bond with a water molecule belonging to the water hexagon that governs the crystal packing makes it impossible for the acetamidato ligand to form an intra-molecular hydrogen bond with O(6), causing the failure of the metal bonding to theophylline through N(7). A critical review on metal bonding properties of theophylline observed in so far reported crystal structures is given, emphasizing the significance of intra-molecular interligand interactions (H-bonding, electrostatic repulsion, and steric constraint) as a factor that could affect metal binding sites/modes of theophylline.

Understanding chemical coupling in cyclic versus compact water clusters with the Ehrenfest Force

We explain why differences in the nature of the chemical coupling in the compact (H2O)6 cluster and cyclic (H2O)4 cluster results in relatively stronger hydrogen-bonds in (H2O)4 compared with (H2O)6. We have investigated and visualized the nature of the two-way donation of both covalent and hydrogen-bond character between covalent (sigma) and hydrogen-bonds. This was undertaken by calculating the precessions Kʹ of the eigenvectors around the bond-path for the Ehrenfest Force F(r) and compared with the corresponding QTAIM Kʹ. We explain the success of the Ehrenfest Force F(r) in determining the chemical coupling underlying the unusual strength of hydrogen-bonds in water.

Temperature Dependence of Intramolecular Vibrational Bands in Small Water Clusters.

Cyclic water clusters are pivotal for understanding atmospheric reactions as well as liquid water, yet the temperature (T) dependence of their dynamics and spectroscopy is poorly studied. The development of highly accurate water potentials, such as MB-pol, partly rectifies this. It remains to account for the quantum nuclear effects (NQE), because quantum nuclear dynamics become increasingly inaccurate at low temperatures. From a practical point of view, we find that NQE can be accounted for simply by subtracting a constant from the frequencies obtained from the velocity autocorrelation functions (VACF) of classical nuclear dynamics, resulting in unprecedented agreement with experiment, mostly within 5 cm-1. We have performed classical simulations of (H2O)n clusters (n = 2-5) from 20 K and up to their melting temperature, calculating both all-atom and partial VACF, thus generating the temperature dependence of the vibrational frequencies (IR and Raman bands). Focusing on the hydrogen-bonded (HBed) OH stretch and HOH bend, we find opposing T dependencies. The HBed OH modes blue shift linearly with T, attributed to ring expansion rather than any specific conformational change. The lowest-frequency Raman concerted mode is predicted to show the largest such shift. In contrast, the HOH bend undergoes a red-shift, with the highest frequency concerted band undergoing the largest red-shift. These results can be explained by a coupled-oscillator model for n hydrogen atoms on a ring, constrained to move either tangentially (stretch) or perpendicularly (bend) to the ring. With increasing temperature and weakening of HBs, the intrinsic force constant increases (stretch) or remains constant (bend), while the nearest-neighbor coupling constant decreases, and this results in the interesting behavior revealed herein. T-dependent Raman studies are required for testing some of these predictions.

Infrared spectral-shift induced by hydrogen bonding cooperativity in cyclic and prismatic water clusters

A direct representation of the cooperative vibrating properties of hydrogen bonds (H-bonds) is presented for cyclic and prismatic water clusters. Through collaborating nuclear vibrations, which are inherent in H-bonding, these weak bonds constitute a simple form of cooperativity, which gives H-bonds an unexpectedly amplified effect. Hence, abnormal shifting activities of infrared vibration modes are observed. The nuclear vibrating patterns clearly reveal that H-bonds retain three effects: i) arousing collective nuclear vibrations, ii) intensifying donor symmetric stretching modes (Symst), and iii) inhibiting donor asymmetric stretching modes (Asyst). H-bonds in aqueous systems show diverse cooperative behavior that originates from the versatile assembly of water molecules. For the first time, we directly show that “coherent” H-bonds reinforce Symst and restrict Asyst extremely powerfully, in contrast to incoherent H-bonds. However, anharmonic nuclear vibrations partially destabilize the cooperative effects of H-bonds. Beyond the present model systems, our findings advance a new perspective on the intrinsic cooperativity of H-bonding, and should stimulate incentives for future spectroscopic and biological dynamic studies.

Study on distribution characteristics of microscopic residual oil in low permeability reservoirs

In order to develop methods to further enhance oil recovery after water flooding in low permeability reservoirs by improving oil displacement efficiency, the displacement mechanism of residual oil was studied by the application of different pertinent measures. For in-depth investigation of oil displacement and variations in residual oil saturation, a large number of visual glass model displacement experiments were performed with different methods, such as changing the displacement direction, cyclic water flooding, displacement pressure difference variation and polymer flooding. In this paper, the models were divided into three (low, medium and high) permeability levels, and the residual oil after water flooding was categorized in five different types: cluster, oil film, oil drop, columnar and blind end residual oil. The experimental results showed that cluster residual oil accounted for the largest proportion after water flooding. In addition, with the increase in model permeability, cluster residual oil saturation increased and other types of residual oil saturations decreased. Compared to other methods, polymer flooding showed maximum displacement efficiency for the same displacement pressure and permeability model. The procedure was then followed by changing the displacement direction, cyclic water flooding and changing the displacement pressure difference. The different residual oil types can be activated by different methods, for example, cluster and columnar residual oil by changing the displacement direction, cluster and columnar residual oil by cyclic water flooding, cluster and oil drop residual oil by increasing displacement pressure difference. Moreover, all of the above mentioned five (05) types of residual oil can be activated by polymer flooding.

Monodisperse water clusters grown on the semimetallic Bi(111) surface

All forms of water are essential for life and a wide range of scientific and technological processes. When adsorbed on metal surfaces, water usually forms a variety of clusters with a broad size distribution. Here we report the monodisperse water clusters formed on the semimetallic Bi(111) surface. High-resolution scanning tunneling microscopy images combined with density functional theory calculations demonstrate that the monodisperse clusters are built exclusively from hexagonal arrangement of six water molecules with slight buckling. All the water hexamers are oriented at the same direction and reveal the identical motif: three-lobed protrusions at high bias and a trigonal hole at low bias. The monodispersity of cyclic water clusters can be rationalized by the fact that hydrogen bonding is the dominant interaction responsible for water cluster stability on Bi(111). The water hexamer is the most favorable because of the maximum strength of H bonds. The decrease of H bonds (the presence of double acceptors) makes it difficult for water molecules to form a smaller (larger) cluster.

Copper(II) complex derived from axial chiral heterocyclic spiro ligand: Crystal structure, characterization and SOD activity

A new Cu(II) coordination polymer (1) constructed from an axially chiral heterocyclic spiro ligand, 2,4,8,10-tetraoxaspiro[5,5]undecane-3,9-dicarboxylic acid (H2L) and 1,3-bis(4-pyridyl)propane (bpp), has been prepared and characterized by single-crystal X-ray diffraction analysis, infrared spectra (IR), elemental analysis, powder X-ray diffraction (PXRD), and thermogravimetric analysis (TGA). Structural analysis shows that 1 features a 2D undulated layer of rhombic meshes with (4, 4) topology. Interestingly, a 1D wave-like water tape formed by the cyclic centrosymmetric chairlike octamer water clusters (H2O)8 are observed between the 2D sheets. Furthermore, the experimental data and computational studies of superoxide dismutase (SOD) activity of H2L and 1 were investigated.

A Combined Experimental and Theoretical Study on the Formation of a Cyclic Tetrameric Water Cluster and a Similar Type of Cyclic Cluster in Copper(II) Schiff Base Complexes

Two copper(II) complexes, [CuL1]⋅2H2O (1) and [CuL2]⋅H2O (2) [where H2L1 {= N,N′-bis(3-methoxysalicylidene)propane-1,3-diamine} and H2L2 {=N,N′-bis(3-ethoxysalicylidene)propane-1,3-diamine} are potential hexadentate N2O4 donor compartmental Schiff bases], were synthesized and characterized. In each complex, copper(II) was placed in the inner N2O2 environment, with a four-coordinate distorted square planar environment keeping the outer O4 compartment pendant. Lattice water molecules were hydrogen bonded with the pendant O4 compartments of the Schiff base ligands. Both complexes formed self-assembled dimers via chelate ring⋅⋅⋅chelate ring and C–H⋅⋅⋅π interactions. A cyclic tetrameric water cluster was stabilized by the oxygen rich region of the Schiff-base ligand in complex 1. A similar type of cyclic cluster involving two water molecules was also observed in complex 2. These supramolecular assemblies were analysed via a DFT study at the M06-2X/def2-TZVP level of theory.

Spectral characterization, crystal structures and biological activities of iminodiacetate ternary complexes

The ternary complexes with stoichiometry [M(imda)(bipy)]·6H2O (M = Cu) and [M(imda)(bipy)(H2O)]·4H2O (M = Ni, Co and Mn) where H2imda = iminodiacetic acid and bipy = 2,2′-bipyridine, are prepared and characterized to exploit as novel antimicrobial agents and SOD mimics. The chemical structures were elucidated by IR, FAB-Mass, 1H, 13C NMR, EPR and spectral techniques. Single crystal X-ray and spectral studies of the complexes (1) and (2) have confirmed a square pyramidal geometry around Cu(II) ion while a saturated six coordinate (distorted octahedral) geometry around the Ni(II), Co(II) and Mn(II) ions due to the additional coordination from water. A supramolecular network is formed by extensive H-bonding in complex (1). The supramolecular assembly in complex (1) is additionally consolidated via the existence of unusual cyclic hexameric water clusters. The antimicrobial activities for the present complexes have been examined against Escherichia coli (K-12), Bacillus subtilis (MTC-121), Staphylococcus aureus (IOASA-22), Salmonella typhymurium (MTCC-98), Candida albicans, Aspergillus fumigatus and Penicillium marneffei. The superoxide dismutase (SOD) activity of the Cu(II) complex (1) is also assessed employing nitrobluetetrazolium (NBT) assay.

Local Mode Approach to OH Stretch Spectra of Benzene–(H2O)n Clusters, n = 2–7

Isomer-specific resonant ion-dip infrared spectra are presented for benzene-water (Bz-(H2O)n) clusters with two to seven water molecules. Local mode Hamiltonians based on scaled M06-2X/6-311++G(2d,p) density functional calculations are presented that accurately model the spectra across the entire OH stretch region (3000-3750 cm(-1)). The model Hamiltonians include the contribution from the water bend overtone and an empirical parameter for the local OH stretch-bend Fermi coupling. The inclusion of this coupling is necessary for accurate modeling of the infrared spectra of clusters with more than three water molecules. For the cyclic water clusters (n = 3-5), the benzene molecule perturbs the system in a characteristic way, distorting the cycle, splitting degeneracies, and turning on previously forbidden transitions. The local OH stretch site frequencies and H···OH hydrogen bond lengths follow a pattern based on the each water monomer's proximity to benzene. The patterns observed for these cyclic water clusters provide insight into benzene's effects on the three-dimensional hydrogen-bonded networks present in water hexamer and heptamer structures, which also have their spectra dramatically altered from their pure water counterparts.

CLUSTERS OF WATER IN THE COMPOSITION OF ANTIFREEZES

Antifreezes based on water eutectics are widely spread in engineering and by crio-preservation of biological objects as well. Salts of inorganic and organic acids, alcohols, glycols, glycol ethers, glycerin, acids, bases, amino- acids, and other chemical compounds are suitable here as supplementary means. Part of these compounds is capable to take part in the formation of H-bonds with water molecules, the others do not form H-bonds (CaCl2), but they are united into crystal-hydrates of CaCl2 · 6 Н2О type. In this case H-bond of water molecules can become the bond of intermolecular-cluster type. It is assumed that basic structural components of liquid water are cyclic penta- (H2O)5 and hexamers (H2O6), built with the participation of the long hydrogen bond and capable of producing the crown effect. Cyclic water clusters - short-range order of water in terms of cavity size and the number of oxygen atoms correspond to crown ethers: 15-crown-5 and 18-crown-6, sodium and calcium ions being absorbed into them. Energy estimation of water and ice (snow) interaction with the components of antifreezes: ethylene- and diethylene glycols, ethylene glycol ethers, hydrogen chloride and ammonia is made. Possibility of solution formation with low freezing temperatures is shown. The analysis of the eutectics and diagrams of water antifreeze fusion based on the salts, alcohols, ethylene glycol, ethylene glycol ethers, hydrogen chloride and ammonia by comparison with an ideal solution of water concerning cryoscopic constant is carried out. It is established that the coefficient K in the equation of linear melting curve y = К·x + в for effective antifreezes, in terms of freezing temperature, exceeds the cryoscopic constant of water, that testifies to the destruction of long-range order of water. Penta- and hexamers of water responsible for short-range order of water pass into the eutectics as monomers or oligomers with the degree of cross linking equal to 2-4. To create effective antifreeze it is important to avoid the destruction of cyclic water clusters. It is desirable, as in the case with ethylene, to have the second component of water antifreeze in a cyclic form too. There is an analogy with naphthenic (cyclic) hydrocarbons of oil, which provide mobility of the condensed state. Promising are antifreezes based on mixtures of inorganic and organic compounds.