Independent Water Molecules Research Articles

The physical basis of osmosis.

Osmosis is an important force in all living organisms, yet the molecular basis of osmosis is widely misunderstood as arising from diffusion of water across a membrane separating solutions of differing osmolarities, and hence different water concentrations. In 1923, Peter Debye proposed a physical model for a semipermeable membrane emphasizing the repulsive forces between solute molecules and membrane that prevent the solute from entering the membrane. His work was hardly noticed at the time and slipped out of view. We show that Debye's analysis of van 't Hoff's law for osmotic equilibrium also provides a consistent and plausible mechanism for osmotic flow. A difference in osmolyte concentrations in solutions separated by a semipermeable membrane leads to different pressures at the two water-membrane interfaces because the total repulsive force between solute molecules and the membrane is different at the two interfaces. Water is therefore driven through the membrane for exactly the same reason that pure water flows in response to an imposed hydrostatic pressure difference. In this paper, we present the Debye model in both equilibrium and flow conditions. We point out its applicability regardless of the nature of the membrane with examples ranging from the predominantly convective flow of water through synthetic membranes and capillary walls to the purely diffusive flow of independent water molecules through a lipid bilayer and the flow of a single-file column of water molecules in narrow protein channels.

Poly[[tetra-deca-kis-(μ-propionato)hepta-barium] propionic acid monosolvate tetra-hydrate

The title compound, {[Ba7(C3H5O2)14]·0.946C3H6O2·4H2O} n , is represented by a metal-organic framework structure that is held together by Ba-O-Ba bonds, as well as by O-H⋯O hydrogen bonds of moderate strength. The structure comprises of four independent Ba2+ cations (one of which is situated on a twofold rotation axis), seven independent propionate and two independent water mol-ecules. The bond-valence sums of all the cations indicate a slight overbonding. There is also an occupationally, as well as a positionally disordered propionic acid mol-ecule present in the structure. Its occupation is slightly lower than the full occupation while the disordered mol-ecules occupy two positions related by a rotation about a twofold rotation axis. In addition, the methyl group in the symmetry-independent propionic acid mol-ecule is also disordered, and occupies two positions. Each propionic acid mol-ecule coordinates to just one cation from a pair of symmetry-equivalent Ba2+ sites and is simultaneously bonded by an O-H⋯Opropionate hydrogen bond. This means that on a microscopic scale, the coordination number of the corresponding Ba2+ site is either 9 or 10. The methyl as well as hy-droxy hydrogen atoms of the disordered propionic acid mol-ecule were not determined.

ACr(C2O4)2(H2O)4 (A = Li or Na): two new coordination polymers of low dimensionality with different hydrogen-bond networks.

Single crystals of two new bimetallic oxalate compounds with the formula [ACr(C2O4)2(H2O)4]n (A = Li or Na), namely catena-poly[[diaqualithium(I)]-μ-oxalato-κ4O1,O2:O1',O2'-[diaquachromium(III)]-μ-oxalato-κ4O1,O2:O1',O2'], (I), and catena-poly[[diaquasodium(I)]-μ-oxalato-κ4O1,O2:O1',O2'-[di-aquachromium(III)]-μ-oxalato-κ4O1,O2:O1',O2'], (II), have been synthesized, characterized and their crystal structures elucidated by X-ray diffraction analysis and compared. The compounds crystallize in the monoclinic space group C2/m for (I) and in the triclinic space group P-1 for (II); however, they have somewhat similar features. In the asymmetric unit of (I), the Li and Cr atoms both have space-group-imposed 2/m site symmetry, while only half of the oxalate ligand is present and two independent water molecules lie on the mirror plane. The water O atoms around the Li atom are disordered over two equivalent positions separated by 0.54 (4) Å. In the asymmetric unit of (II), the atoms of one C2O42- ligand and two independent water molecules are in general positions, and the Na and Cr atoms lie on an inversion centre. Taking into account the symmetry sites of both metallic elements, the unit cells may be described as pseudo-face-centred monoclinic for (I) and as pseudo-centred triclinic for (II). Both crystal structures are comprised of one-dimensional chains of alternating trans-Cr(CO)4(H2O)2 and trans-A(CO)4(H2O)2 units μ2-bridged by bis-chelating oxalate ligands. The resulting linear chains are parallel to the [101] direction for (I) and to the [11-1] direction for (II). Within the two coordination polymers, strong hydrogen bonds result in tetrameric R44(12) synthons which link the metal chains, thus leading to two-dimensaional supramolecular architectures. The two structures differ from each other with respect to the symmetry relations inside the ligand, the role of electrostatic forces in the crystal structure and the molecular interactions of the hydrogen-bonded networks. Moreover, they exhibit the same UV-Vis pattern typical of a CrIII centrosymmetric geometry, while the IR absorption shows some differences due to the oxalate-ligand conformation. Polymers (I) and (II) are also distinguished by a different behaviours during the decomposition process, the precursor (I) leading to the oxide LiCrO2, while the residues of (II) consist of a mixture of sodium carbonate and CrIII oxide.

Crystal structure, DSC, TGA, Hirshfeld and infrared study at ambient temperature of phenylammonium hexachlorobismuthate trihydrate [C6H5NH3]3BiCl6·3H2O

The synthesis, X-ray diffraction, Hirshfeld, DSC, TGA-dTG, and Infrared spectrum of a new [C6H5NH3]3BiCl6·3H2O crystal are reported. The crystal structure of the title compound at 293 K [P212121; Z = 4; a = 7.4348(3)Å, b = 16.5416(6)Å, c = 22.0510(8)Å] comprises units containing an isolated and distorted BiCl63−octahedron, three independent organic cations, and three independent water molecules linked together by NH⋯Cl, NH⋯O, OH⋯Cl, and OH⋯O hydrogen bonding to form organic-inorganic network. The X-rays powder diffraction pattern is satisfactory indexed and affined on the basis of an orthorhombic unit cell, with parametrs closed to those determined by single crystal X-ray diffraction. Hirshfeld surface analysis and fingerprint plots methods are used to identify and analyze the significant intermolecular interactions in the crystal network, and to determine the contribution of the component units in the crystal structure construction. DSC curves show two non reproducible and irreversible endothermic anomalies (T1 ≅ 115 °C, T2 ≅ 132 °C), which correspond to the dehydration due to removing of water species from the crystal structure. TG-dTG analyses confirm that the removed water is of crystallization in agreement with X-Ray and DSC analyses. The study of Infrared spectrum at room temperature confirms the presence of C6H5NH3+ cations, H2O molecules, which are linked to BiCl63− anions by hydrogen bonding.

Synthesis, crystal structure, infrared spectrum, and thermal properties of [Ni(1,10-phenanthroline)3](fumarate)·9H2O complex with hydrogen bonded supramolecular layers involving fumarate anions

Abstract From the aqueous-ethanolic system Ni(OH)2—H2 fum—phen (H2fum = fumaric acid, phen = 1,10-phenanthroline), novel complex [Ni(phen)3](fum)·9H2O (1) was isolated and characterized by chemical analyses and FT-IR spectroscopy. Results of single crystal X-ray structure analysis have shown that the ionic crystal structure of 1 is built of [Ni(phen)3]2+ complex cations, fumarate dianions and nine crystallographically independent water molecules of crystallization. The Ni(II) atom exhibits hexa-coordination by three phen ligands with mean Ni-N bond length of 2.090 Å. Water molecules form hydrophilic supramolecular layers with fumarate dianions via extended network of O—H···O type hydrogen bonds with O···O distances from the range of 2.676(2)—2. 916(2) Å; hydrophobic complex cations are embedded between these layers. Thermal study of 1 has shown that endothermic dehydration in the temperature range of 95—195 °C takes at least two steps of the process. Graphical Abstract Crystal structure of [Ni(phen)3]fum·9H2O (phen = 1,10-phenanthroline; H2 fum = fumaric acid) which is built of supramolecular layers formed by hydrogen bonded water solvate molecules and fum dianions and between the supramolecular layers embedded [Ni(phen)3]2+ complex cations is described here.

Theoretical study of the microhydration of 1‐chloro and 2‐chloro ethanol as a clue for their relative propensity toward dehalogenation

AbstractThis work reports a computational analysis of hydrogen‐bonded clusters of mono‐, di‐, tri‐, and tetrahydrates of the chlorohydrins CH3CHClOH (1ClEtOH) and CH2ClCH2OH (2ClEtOH). The goal of the study is to assess the role of the water solvent into the facilitation of the initial step for dehalogenation of these compounds, a process of interest in several contexts. Molecular orbital methods (MP2), density functional methods (B3LYP, M06, and ωB97X‐D), and composite model chemistries (CBS‐QB3, G4) were employed to investigate the structure, electronic distribution, and hydrogen‐bonded structure of seven monohydrates, six dihydrates, five trihydrates, and five tetrahydrates of both species. Standard reaction enthalpy and standard Gibbs free reaction energy () were computed for all aggregates with respect to n independent water molecules and with respect to the dimer, trimer, and tetramer of water, respectively, in order to evaluate stability and hydrogen bonding network. The influence of the water chains on the length and vibrational frequencies, especially of the CCl and OH bonds, was evaluated. Hydrogen bonding in the complexes is discussed at length.

Crystal structure of aqua-(1H-pyrazole-κN2)(pyridine-2,6-di-carboxyl-ato-κ3O2,N,O6)copper(II) dihydrate.

In the title compound, [Cu(C7H3NO4)(C3H4N2)(H2O)]·2H2O, the CuII atom is coordinated by three O atoms and two N atoms, provided by a tridentate pyridine-2,6-di-carboxyl-ate (pdc), one pyrazole and one water ligand, forming a slightly distorted square-pyramidal geometry [range of O-Cu-O and O-Cu-N bond angles = 79.55 (8)-166.22 (10)°]. The water mol-ecule is positioned at the apical position. In the crystal, the complex mol-ecule and the two crystallographically independent non-coordinating water mol-ecules are linked into a supra-molecular layer structure parallel to the ab plane via O-H⋯O and N-H⋯O hydrogen bonds.

EQE: An open‐source density functional embedding theory code for the condensed phase

AbstractIn this work, we present the main features and algorithmic details of a novel implementation of the frozen density embedding (FDE) formulation of subsystem density functional theory (DFT) that is specifically designed to enable ab initio molecular dynamics (AIMD) simulations of large‐scale condensed‐phase systems containing 1000s of atoms. This code (available at http://eqe.rutgers.edu) has been given the moniker of embedded Quantum ESPRESSO (eQE) as it is a generalization of the open‐source Quantum ESPRESSO (QE) suite of programs. The strengths of eQE reside in a hierarchical parallelization scheme that allows for an efficient and fully self‐consistent treatment of the electronic structure (via the addition of an additional DIIS extrapolation layer) while simultaneously exploiting the inherent symmetries and periodicities in the system (via sampling of subsystem‐specific first Brillouin zones and utilization of subsystem‐specific basis sets). While bulk liquids and molecular crystals are two classes of systems that exemplify the utility of the FDE approach (as these systems can be partitioned into weakly interacting subunits), we show that eQE has significantly extended this regime of applicability by outperforming standard semilocal Kohn–Sham DFT (KS‐DFT) for large‐scale heterogeneous catalysts with quite different layer‐specific electronic structure and intrinsic periodicities. eQE features very favorable strong parallel scaling for a model system of bulk liquid water composed of 256 water molecules, which allows for a significant decrease in the overall time to solution when compared to KS‐DFT. We show that eQE achieves speedups greater than one order of magnitude ( ) when performing AIMD simulations of such large‐scale condensed‐phase systems as: (1) molecular liquids via bulk liquid water represented by 1024 independent water molecules (3072 atoms with a 25.3× speedup over KS‐DFT), (2) polypeptide/biomolecule solvation via (gly)6 solvated in (H2O)395 (1230 atoms with a 38.6× speedup over KS‐DFT), and (3) molecular crystals via a 3 × 3 × 3 periodic supercell of pentacene (1940 atoms with a 12.0× speedup over KS‐DFT). These results represent a significant improvement over the current state‐of‐the‐art and now enable subsystem DFT‐based AIMD simulations of realistically sized condensed‐phase systems of interest throughout chemistry, physics, and materials science.

An infinite two-dimensional hybrid water-chloride network in a 4'-(furan-2-yl)-2,2':6',2''-terpyridine nickel(II) matrix.

A new complex, namely bis-[4'-(furan-2-yl)-2,2':6',2''-terpyridine]-nickel(II) dichloride deca-hydrate, [Ni(C19H13N3O)2]Cl2·10H2O, has been crystallized by solvent evaporation and characterized by single-crystal X-ray diffraction. The coordination environment of the NiII cation is distorted octa-hedral with slight deviations from an idealized geometry. The most intriguing structural feature is an infinite two-dimensional hybrid water-chloride network parallel to (011) constructed by O-H⋯O and O-H⋯Cl hydrogen bonds involving two independent chloride ions and ten independent solvent water mol-ecules with an l-shaped pattern. One of the furyl rings is disordered with a refined occupancy ratio of 0.786 (13):0.214 (13).

Synthesis and crystal structure of cesium actinide(VI) tricarbonate complexes Cs4AnO2(CO3)3·6H2O, An(VI) = U, Np, Pu

Tricarbonate complexes of hexavalent U, Np, and Pu with outer-sphere cesium cations, Cs4AnO2·(CO3)3·6H2O, were synthesized and studied by single crystal X-ray diffraction analysis. Crystals of Cs4AnO2·(CO3)3·6H2O consist of [AnO2(CO3)3]4– complex anions and hydrated Cs+ cations. The coordination polyhedron (CP) of An(VI) atoms is a distorted hexagonal bipyramid with three CO32– anions arranged in the equatorial plane. Four independent Cs+ cations have the coordination surrounding in the form of 11-, 10-, and 9-vertex polyhedra formed by the O atoms of CO32– anions, AnO22+ cations, and water molecules. Six crystallographically independent water molecules in the structure of Cs4AnO2(CO3)3·6H2O form a three-dimensional system of hydrogen bonds in which the O atoms of carbonate ions and water molecules act as proton acceptors. The “yl” oxygen atoms of AnO22+ cations are not involved in hydrogen bonding. The lengths of the An–Ocarb bonds in the equator of the U, Np, and Pu hexagonal bipyramids are noticeably influenced by incorporation of the O atoms of the CO32– anions in the coordination polyhedra of Cs+ ions and by involvement of these atoms in hydrogen bonding.

Water clusters with anion templates in cucurbit[6]uril supramolecular pseudorotaxanes

Two types of anion water clusters have been observed in cucurbit[6]uril based pseudorotaxanes with two kinds of guests. (COO−)2(C2H5OH)2(H2O)4 anion water clusters and (H2O)2 water clusters are formed with the carboxylate groups of the guest 1, 1′-(hexane-1, 6-diyl) dipyridinium-4-carboxylate inner salt (HDPC) and connect the pseudorotaxane molecules to form 3D networks. Anion water clusters Cl2−(H2O) with independent water molecules are observed in the crystal structure of the pseudorotaxane with the guest 1, 1′-(hexane-1, 6-diyl) dipyridinium-4-hydroximic acid dichloride (HDHD). The results revealed that terminal groups of the guests, the solvents and the anions species in cucurbit Arunachalam and Ghosh (2011) uril pseudorotaxanes could affect the structures and the sizes of water clusters.

Crystal structure of bassetite and saléeite: new insight into autunite-group minerals

The crystal structures of two autunite-group minerals have been solved recently. The crystal structure of bassetite, Fe 2+ [(UO 2 )(PO 4 )] 2 (H 2 O) 10 , from the type locality in Cornwall, United Kingdom (Basset Mines) was solved for the first time. Bassetite is monoclinic, space group P 2 1 /n, a = 6.961(1), b = 20.039(2), c = 6.974(1) A and β = 90.46(1)°. The crystal structure of saleeite, Mg[(UO 2 )(PO 4 )] 2 (H 2 O) 10 , from Shinkolobwe, Democratic Republic of Congo, was also solved. Saleeite is monoclinic, space group P 2 1 /n, a = 6.951(1), b = 19.942(1), c = 6.967(1) A and β = 90.58(1)°. The crystal structure investigation of bassetite ( R 1 = 0.0658 for 1879 observed reflections with | F o | ≥ 4σ F ) and saleeite ( R 1 = 0.0307 for 1990 observed reflections with | F o | ≥ 4σ F ) confirms that both minerals are topologically identical and that bassetite contains ten water molecules per formula unit. Their structure contains autunite-type sheets, [(UO 2 )(PO 4 )] − , consisting of corner-sharing UO 6 square bipyramids and PO 4 tetrahedra. Iron and magnesium are surrounded by water molecules to form Fe(H 2 O) 6 or Mg(H 2 O) 6 octahedra located in interlayer, between the autunite-type sheets. Two isolated independent water molecules are also located in interlayer. Energy-dispersive X-ray spectroscopy analysis confirmed the chemical composition obtained from structure refinement. These new data prompt a re-assessment of minerals of the autunite and meta-autunite groups.

Avoiding fractional electrons in subsystem DFT based ab-initio molecular dynamics yields accurate models for liquid water and solvated OH radical.

In this work we achieve three milestones: (1) we present a subsystem DFT method capable of running ab-initio molecular dynamics simulations accurately and efficiently. (2) In order to rid the simulations of inter-molecular self-interaction error, we exploit the ability of semilocal frozen density embedding formulation of subsystem DFT to represent the total electron density as a sum of localized subsystem electron densities that are constrained to integrate to a preset, constant number of electrons; the success of the method relies on the fact that employed semilocal nonadditive kinetic energy functionals effectively cancel out errors in semilocal exchange-correlation potentials that are linked to static correlation effects and self-interaction. (3) We demonstrate this concept by simulating liquid water and solvated OH(•) radical. While the bulk of our simulations have been performed on a periodic box containing 64 independent water molecules for 52 ps, we also simulated a box containing 256 water molecules for 22 ps. The results show that, provided one employs an accurate nonadditive kinetic energy functional, the dynamics of liquid water and OH(•) radical are in semiquantitative agreement with experimental results or higher-level electronic structure calculations. Our assessments are based upon comparisons of radial and angular distribution functions as well as the diffusion coefficient of the liquid.

5-Acetamido-1H-pyrazole-4-carboxamide monohydrate

There are two independent molecules of the title carboxamide compound, C6H8N4O2·H2O, as well as two independent water molecules in the asymmetric unit. The two independent carboxamide molecules differ primarily in the relative orientations of the peripheral methyl and amino groups. Intramolecular N—H...O hydrogen bonds assist in determining the orientations of the acetamido substituents. The three-dimensional crystal packing is directed by a large network of O—H...O, N—H...O, C—H...O and C—H...N hydrogen bonds.

Crystal structures of tetra-methyl-ammonium (2,2'-bi-pyridine)-tetra-cyanidoferrate(III) trihydrate and poly[[(2,2'-bi-pyridine-κ(2) N,N')di-μ2-cyanido-dicyanido(μ-ethyl-enedi-amine)(ethyl-enedi-amine-κ(2) N,N')-cadmium(II)iron(II)] monohydrate

The crystal structures of the building block tetra-methyl-ammonium (2,2'-bi-pyridine-κ(2) N,N')tetra-cyanidoferrate(III) trihydrate, [N(CH3)4][Fe(CN)4(C10H8N2)]·3H2O, (I), and a new two-dimensional cyanide-bridged bimetallic coordination polymer, poly[[(2,2'-bi-pyridine-κ(2) N,N')di-μ2-cyanido-dicyanido(μ-ethyl-enedi-amine-κ(2) N:N')(ethyl-enedi-amine-κ(2) N,N')cadmium(II)iron(II)] monohydrate], [CdFe(CN)4(C10H8N2)(C2H8N2)2]·H2O, (II), are reported. In the crystal of (I), pairs of [Fe(2,2'-bipy)(CN)4](-) units (2,2'-bipy is 2,2'-bi-pyri-dine) are linked together through π-π stacking between the pyridyl rings of the 2,2'-bipy ligands to form a graphite-like structure parallel to the ab plane. The three independent water mol-ecules are hydrogen-bonded alternately with each other, forming a ladder chain structure with R 4 (4)(8) and R 6 (6)(12) graph-set ring motifs, while the disordered [N(CH3)4](+) cations lie above and below the water chains, and the packing is stabilized by weak C-H⋯O hydrogen bonds. The water chains are further linked with adjacent sheets into a three-dimensional network via O-H⋯O hydrogen bonds involving the lattice water mol-ecules and the N atoms of terminal cyanide groups of the [Fe(2,2'-bipy)(CN)4](-) building blocks, forming an R 4 (4)(12) ring motif. Compound (II) features a two-dimensional {[Fe(2,2'-bipy)(CN)4Cd(en)2]} n layer structure (en is ethyl-enedi-amine) extending parallel to (010) and constructed from {[Fe(2,2'-bipy)(CN)4Cd(en)]} n chains inter-linked by bridging en ligands at the Cd atoms. Classical O-H⋯N and N-H⋯O hydrogen bonds involving the lattice water mol-ecule and N atoms of terminal cyanide groups and the N-H groups of the en ligands are observed within the layers. The layers are further connected via π-π stacking inter-actions between adjacent pyridine rings of the 2,2'-bipy ligands, completing a three-dimensional supra-molecular structure.

Structural characterization, vibrational spectroscopy accomplished with DFT calculation, thermal and dielectric behaviors in a new organic-inorganic tertrapropylammonium aquapentachlorostannate dihydrate compound

In this work a novel compound tertrapropylammonium aquapentachlorostannate dihydrate was synthesized and characterized by; single crystal X-ray diffraction, vibrational spectroscopy, differential scanning calorimetric and dielectric measurement. The crystal structure refinement at room temperature reveled that this later belongs to the monoclinic compound with P121/c1 space group with the following unit cell parameters a = 8.2699(3) Å, b = 12.4665(4) Å, c = 22.3341(7) Å and β = 92.94(0)°. The crystal arrangement can be described by stacked organic-inorganic layers in the c direction with two independent water molecules placed between each two layers. The detailed interpretations of the vibrational properties of the studied compound were performed using density functional theory (DFT) with the B3LYP/LanL2DZ basis set, and has enabled us to make the detailed assignments by comparative study of the experimental and calculated Raman and IR spectra. The differential scanning calorimetry (DSC) measurement disclosed two anomalies in the temperature range 356–376 (T1) K and at 393 K (T2) characterized by the dehydration of the sample and probably a reconstruction of a new structure after T2 transition. The temperature dependences of dielectric permittivity show a relaxation process around T2 anomaly indicating the occurrence of the disorder at high temperature. The dependence of the exponent m(T) on temperature, extracted from the straight lines of log(ε″) with log (ω), suggests that the correlated barrier hopping is the appropriate model for the conduction mechanism.

Preparation, First Structure Analysis, and Magnetism of the Long‐Known Nickel Benzoate Trihydrate – A Linear Ni···Ni···Ni Polymer and Its Parallels with the Active Site of Urease

AbstractNickel benzoate trihydrate (1) has been prepared in single‐crystalline form by the reaction of nickel carbonate with benzoic acid in boiling aqueous solution. Its crystal structure comprises positively charged [Ni(Bz)(H2O)2]nn+ chains, benzoate anions, and one independent water molecule of solvation. The hexacoordinate NiII centers in the chains are triply bridged by one syn‐syn carboxylato and two aqua bridges, and adjacent chains are linked by O–H···O hydrogen bonds [O···O distances are in the range 2.647(3)–2.684(3) Å] through solvate water molecules and benzoate anions. Thermal analysis revealed that 1 is stable up to 100 °C; further heating led to full dehydration accompanied by an additional decomposition reaction, as characterized by IR analysis of the intermediates. The geometrical features of the Ni centers have been compared with similar features at the active sites of urease. The effective magnetic moment per formula unit µeff has a value of 3.17µB at room temperature and upon cooling reaches a maximum value of 12.39µB at T = 4.6 K, which indicates ferromagnetic coupling between the nearest NiII atoms [3.0671(1) Å] within the chains; at lower temperatures this is counteracted by zero‐field splitting.

Synthesis, crystal structure, and spectra of the Np(V) terephthalate [C(NH2)3]3[NpO2(C6H4(COO)2)2]·5H2O and An(VI) terephthalates [AnO2(C6H4(COO)2)] (An = U, Np, Pu)

The structure and spectra of the Np(V) terephthalate [C(NH2)3]3[NpO2(C6H4(COO)2)2]·5H2O (I) and An(VI) terephthalates [AnO2(C6H4(COO)2)] (II), where An = U, Np, or Pu, were studied. The crystal structure of I is build of NpO2 + cations and terephthalate anions linked with each other in infinite anionic chains [NpO2(C6H4(COO)2)2]n 3−, with the water molecules and guanidinium cations arranged between them. The Np atom has the coordination surrounding in the form of a hexagonal bipyramid whose equatorial plane is formed by the O atoms of three [C6H4(COO)2]2− anions. There are two independent [C6H4(COO)2]2− anions in the structure. One of them is bidentate chelating, and the other is chelating and bridging, with both of its carboxylate groups bonded to the NpO2 + cations in the anionic chains in the bidentate fashion. Five crystallographically independent water molecules are localized in the structure of I. Together with the [C(NH2)3]+ cations, these water molecules form a three-dimensional system of hydrogen bonds. The crystal structure of II is built of neutral [AnO2(C6H4(COO)2)]n layers formed by the AnO2 2+ cations and terephthalate anions. The An(VI) atom has the coordination surrounding in the form of a tetragonal bipyramid whose equatorial plane is formed by the O atoms of four [C6H4(COO)2]2− anions. The IR and electronic absorption spectra of the compounds are presented.

Crystal structure of tetra-kis-(μ3-2-{[1,1-bis-(hy-droxy-meth-yl)-2-oxidoeth-yl]imino-meth-yl}phenolato)tetra-copper(II) ethanol monosolvate 2.5-hydrate.

The title compound, [Cu4(C11H13NO4)4]·CH3CH2OH·2.5H2O, is an electronically neutral tetra­nuclear copper(II) complex with a cubane-like Cu4O4 core. The complete molecule has point group symmetry 2. The phenol hy­droxy group and one of the three alcohol hy­droxy groups of each 2-{[tris­(hy­droxy­meth­yl)meth­yl]imino­meth­yl}phenol ligand are depro­ton­ated, while the secondary amine and the other two hy­droxy groups remain unchanged. The CuII atoms in the Cu4O4 core are connected by four μ3-O atoms from the deprotonated alcohol hy­droxy groups. Each of the penta­coordinated CuII ions has an NO4 distorted square-pyramidal environment through coordination to the tridentate Schiff base ligands. The Cu—N/O bond lengths span the range 1.902 (4)–1.955 (4) Å, similar to values reported for related structures. There are O—H⋯O hydrogen-bond inter­actions between the complex molecules and the ethanol and water solvent molecules, leading to the formation of a three-dimensional network. The ethanol solvent molecule is disordered about a twofold rotation axis. One of the two independent water molecules is also located on this twofold rotation axis and shows half-occupancy.

Thermodynamics of water dimer dissociation in the primary hydration shell of the iodide ion with temperature-dependent vibrational predissociation spectroscopy.

The strong temperature dependence of the I(-)·(H2O)2 vibrational predissociation spectrum is traced to the intracluster dissociation of the ion-bound water dimer into independent water monomers that remain tethered to the ion. The thermodynamics of this process is determined using van't Hoff analysis of key features that quantify the relative populations of H-bonded and independent water molecules. The dissociation enthalpy of the isolated water dimer is thus observed to be reduced by roughly a factor of three upon attachment to the ion. The cause of this reduction is explored with electronic structure calculations of the potential energy profile for dissociation of the dimer, which suggest that both reduction of the intrinsic binding energy and vibrational zero-point effects act to weaken the intermolecular interaction between the water molecules in the first hydration shell. Additional insights are obtained by analyzing how classical trajectories of the I(-)·(H2O)2 system sample the extended potential energy surface with increasing temperature.