Cyclic Water Hexamers Research Articles

Ketone-hybridized Cyclic Water Hexamer with Chair-conformation in Crystal of Macrocyclic peri-Aroylnaphthalene Compound

The titled macrocyclic arene ether ketone compound affords peculiarly organized crystals of dimeric molecular aggregated motif including exquisitely aligned water molecules. In the crystal, four wa...

Ice-like Cyclic Water Hexamer Trapped within a Halide Encapsulated Hexameric Neutral Receptor Core: First Crystallographic Evidence of a Water Cluster Confined within a Receptor-Anion Capsular Assembly

Over the past few decades, the tren [tris(2-aminoethyl)amine] skeleton has materialized as one of the supreme anion binding building blocks demonstrating a strong interplay among topology, complementarity, cooperativity, and coordination. However, anion recognition by modest tren-based unsubstituted aromatic urea has been underexplored, mainly due to the deficiency of π-acidic or electron-withdrawing aryl terminals. This report establishes an infrequent hexameric neutral receptor-anion-water molecular self-assembly, where a conformationally flexible C3v-symmetric halide (F–/Cl–) encapsulated electron-rich naphthyl group containing N-bridged tripodal urea receptor effectively entraps a chair-shaped ice-like neutral cyclic water hexamer within the hexameric cavity of a neutral receptor-halide host–guest assembly.

Cyclic (H2O)6confined hexameric host–guest assemblies and aerial CO2fixation by electron-rich neutral urea/thiourea scaffolds

Neutral capsular assemblies of electron-rich tris-urea/thiourea receptors are formedviacyclic (H2O)6trapping or atmospheric CO2fixation.

Hydrogen bonding characterization in water and small molecules.

The prototypical hydrogen bond in water dimer and hydrogen bonds in the protonated water dimer, in other small molecules, in water cyclic clusters, and in ice, covering a wide range of bond strengths, are theoretically investigated by first-principles calculations based on density functional theory, considering not only a standard generalized gradient approximation functional but also, for the water dimer, hybrid and van der Waals corrected functionals. We compute structural, energetic, and electrostatic (induced molecular dipole moments) properties. In particular, hydrogen bonds are characterized in terms of differential electron density distributions and profiles, and of the shifts of the centres of maximally localized Wannier functions. The information from the latter quantities can be conveyed to a single geometric bonding parameter that appears to be correlated with the Mayer bond order parameter and can be taken as an estimate of the covalent contribution to the hydrogen bond. By considering the water trimer, the cyclic water hexamer, and the hexagonal phase of ice, we also elucidate the importance of cooperative/anticooperative effects in hydrogen-bonding formation.

Theoretical study of graphite intercalated with water cyclic hexamers

Water-treated graphite has attracted attention as a possible room-temperature superconductor. In this work, we use density functional theory to calculate the structural and electronic properties of crystal graphite intercalated with cyclic water hexamers. We treat two different stackings of this system. In the first, we consider an AB stacking which is typical of graphite. In the second, we consider two configurations of an AA stacking which is typical of the superconducting graphite intercalation compounds. All three of the configurations studied are stable and in all three cases, we found the system to be a semimetal. Certain impurities or hydrostatic pressure might change the system into a metal, which seems more suitable for studying its behaviour as a superconductor. This is the first work that considers a crystal structure in the problem of water-treated graphite.

Exceptional Isotopic‐Substitution Effect: Breakdown of Collective Proton Tunneling in Hexagonal Ice due to Partial Deuteration

AbstractMultiple proton transfer controls many chemical reactions in hydrogen‐bonded networks. However, in contrast to well‐understood single proton transfer, the mechanisms of correlated proton transfer and of correlated proton tunneling in particular have remained largely elusive. Herein, fully quantized ab initio simulations are used to investigate H/D isotopic‐substitution effects on the mechanism of the collective tunneling of six protons within proton‐ordered cyclic water hexamers that are contained in proton‐disordered ice, a prototypical hydrogen‐bonded network. At the transition state, isotopic substitution leads to a Zundel‐like complex, [HO⋅⋅⋅D⋅⋅⋅OH], which localizes ionic defects and thus inhibits perfectly correlated proton tunneling. These insights into fundamental aspects of collective proton tunneling not only rationalize recent neutron‐scattering experiments, but also stimulate investigations into multiple proton transfer in hydrogen‐bonded networks much beyond ice.

Exceptional isotopic-substitution effect: breakdown of collective proton tunneling in hexagonal ice due to partial deuteration.

Multiple proton transfer controls many chemical reactions in hydrogen-bonded networks. However, in contrast to well-understood single proton transfer, the mechanisms of correlated proton transfer and of correlated proton tunneling in particular have remained largely elusive. Herein, fully quantized ab initio simulations are used to investigate H/D isotopic-substitution effects on the mechanism of the collective tunneling of six protons within proton-ordered cyclic water hexamers that are contained in proton-disordered ice, a prototypical hydrogen-bonded network. At the transition state, isotopic substitution leads to a Zundel-like complex, [HO⋅⋅⋅D⋅⋅⋅OH], which localizes ionic defects and thus inhibits perfectly correlated proton tunneling. These insights into fundamental aspects of collective proton tunneling not only rationalize recent neutron-scattering experiments, but also stimulate investigations into multiple proton transfer in hydrogen-bonded networks much beyond ice.

An unprecedented mixed valence cobalt(III)/cobalt(II) ion-pair complex ([CoCO3(bipy)2]2[Co(DCA)2]⋅16H2O) with two novel water tapes

An unprecedented mixed valence cobalt(III)/cobalt(II) ion-pair complex, [CoCO3(bipy)2]2[Co(DCA)2]⋅16H2O (1) [bipy = 2,2′-bipyridine, DCA = demethylcantharidate, exo-1,4-epoxy-cyclohexyl-2,3-dicarboxylate group, (C8H8O5)2 −], has been synthesized and characterized by elemental analysis, IR, UV–vis, Thermogravimetric analysis (TGA) and single crystal X-ray diffraction. The crystal structure of 1 consists of three independent molecular moieties: [CoCO3(bipy)2]+, [Co(DCA)2]2–, and water molecules of crystallization. Interestingly, two novel water tapes, one comprises of alternate cyclic water tetramer and octamer, the other is constructed by alternate cyclic water hexamer and carboxylate–water hybrid octamer [(H2O)2(COO)2]2 −, have been detected for the first time in the host framework of 1. The two novel water tapes are linked together by the DCA and carbonate ligands via hydrogen bonds into a 2D water layer, and then the water layers assemble complex ions ([CoCO3(bipy)2]+ and [Co(DCA)2]2 −) through hydrogen bonds, π–π interactions and electrostatic interactions to form the overall 3D metal–organic framework structure.

Self-assembly of water cluster in Cu(II) complexes and magnetic property

Two new complexes, namely {[Cu2(L)3(bipy)2]·6.87H2O·NO3} (1) and {[Cu2(L)4(H2O)2]·2H2O} (2) (HL=2-ethoxynicotinic acid and bipy=2,2′-bipyridine) have been synthesized and structurally characterized by single-crystal diffraction analysis. In the dinuclear Cu(II) compounds of 1 and 2, hydrogen bond ineractions exist between host and guest molecules, resulting in interesting 3D supramolecular motifs. 1D T6(2)T8(2) water tape consisting of alternative cyclic water hexamers and octamers and dimmer water cluster are observed in complexes 1 and 2, respectively. Magnetic studies reveal the overall antiferromagnetic interaction between neighboring Cu(II) ions in compounds 1 and 2.

Chain of water hexamers and tetramers hosted in a redox product of a Co(III) metal complex: Syntheses, characterization and single crystal X-ray structure determination of Co(II/III) complexes with sulfur oxo-anions

In the present study, four new Co(II/III) metal complexes, [Co(phen)3]S4O6·2H2O (1), [Co(phen)3]S4O6·7H2O (2), [Co(phen)3]2(S4O6)3·6.5H2O (3) and [Co(phen)3]S2O3·9H2O (4), have been synthesized and characterized by elemental analysis, TGA and various spectroscopic techniques. In the case of 1 and 2, an unexpected redox reaction took place and the complexes formed are different in terms of their water of crystallization. The structures of 1–3 have been determined by single crystal X-ray crystallography. Complex salts 1–3 crystallize in the orthorhombic (Pbca), triclinic (P1¯) and monoclinic (P21/c) crystal systems, respectively. Their X-ray crystal structure determination revealed the presence of non-covalent cation-to-anion (C–H⋯Oanion hydrogen bonds), anion-to-cation (anion⋯π interactions) and cation-to-cation (C–H⋯π and π⋯π stacking interactions) interactions. Interestingly, a detailed packing analysis has shown the presence of rare chains of cyclic water hexamers (chair form) and tetramers, stabilized by O–H⋯O and C–H⋯O hydrogen bond interactions in the supramolecular complex [Co(phen)3]S4O6·7H2O (2).

Tris(1,10-phenanthroline-κ2N,N′)cadmium(II) bis(perchlorate) 3.5-hydrate: a water chain stabilized by perchlorate anions

The title compound, [Cd(C(12)H(8)N(2))(3)](ClO(4))(2).3.5H(2)O, contains a cross-shaped one-dimensional channel along the c axis which encapsulates an ordered water chain. This water chain features a centrosymmetric cyclic water hexamer unit with a chair-like conformation. Neighbouring hexamers are linked by bridging water molecules. The host perchlorate anions recognize and stabilize the guest water chain via three kinds of hydrogen-bond patterns, leading to the formation of a complex one-dimensional {[(H(2)O)(7)(ClO(4))(4)](4-)}(n) anionic chain. One perchlorate acts as a single hydrogen-bond acceptor dangling on the chain, the second perchlorate on the chain serves as a double hydrogen-bond acceptor for only one water molecule to form an R(2)(2)(6) ring, where both entities lie on a twofold axis, while the third perchlorate, which also lies on a twofold axis, accepts two hydrogen bonds from two equivalent water molecules and is involved in the construction of an R(6)(5)(14) ring.

A novel (3,4,10)-connected three-dimensional hydrogen-bonded supramolecular network containing a cyclic water hexamer

The title compound, 4,4'-(1,1,1,3,3,3-hexafluoroisopropylidene)diphthalic acid hexahydrate, C(19)H(10)F(6)O(8).6H(2)O, crystallizes in the centrosymmetric space group Pbcn, with half of the diphthalic acid residue and three water molecules in the asymmetric unit. The organic molecule is located on a crystallographic twofold axis. In the solid, cyclic water hexamers in chair conformations have crystallographically imposed inversion symmetry. Strong O-H...O hydrogen bonds between the hexamers and organic molecules result in a unique three-dimensional supramolecular network [O...O = 2.554 (2)-2.913 (2) A]. This compound represents the first example of a (3,4,4,10)-connected four-nodal supramolecular topology with the Schläfli symbol (4(3).5.6.7)(2)(4(3).5(2).7)(2)(4(3))(2)(4(6).5(6).6(2).7(8).8(14).9(9)).

Counter cation Al 3+ assisting formation of a 2D water sheet that contains both cyclic water hexamers in boat and chair conformations and cyclic water tetramers in an Anderson-type polyoxometalate [Al(H 2O) 6][Al(OH) 6Mo 6O 18]·10H 2O

For the first time, a 2D water sheet that contains both cyclic water hexamers around Al 3+ in boat and chair conformations and cyclic water tetramers was crystallographically observed in an Anderson-type supramolecular complex, [Al(H 2O) 6][Al(OH) 6Mo 6O 18]·10H 2O 1, in which the element type of both the counter cation and the heteroatom of the polyanion are the same, that is Aluminum. The counter cation Al 3+ is coordinated by six water molecules forming a nearly ideal octahedron. The octahedron is then hydrogen-bonded to its surrounding lattice water molecules producing a novel Al 3+-containing 1D water chain composed of both boat- and chair-like water hexamers. More interestingly and importantly, the water chains further on join together through a parallelogram composed of four water molecules to yield a unique 2D water sheet.

Novel L4(6)6(6) water layers trapped in an organic host framework 3-(1H-imidazol-1-yl)-1-phenylpropan-1-one

Using a flexible imidazole derivate ligand 3-(1H-Imidazol-1-yl)-1-phenylpropan-1-one (L), novel 2D (two-dimensional) L4(6)6(6) water layers can be observed, which consist of fused cyclic water tetramers and hexamers. These 2D water layers are also trapped in supramolecular architecture L·3H 2O ( 1). It is interesting that the C–H···π interactions obviously play an important role in stabilizing the packing structure, which also reveal the cooperative interactions between these supramolecular contacts in the construction of 2D water layers.

Ice nanoclusters at hydrophobic metal surfaces

Studies of the structure of supported water clusters provide a means for obtaining a rigorous molecular-scale description of the initial stages of heterogeneous ice nucleation: a process of importance to fields as diverse as atmospheric chemistry, astrophysics and biology. Here, we report the observation and characterization of metal-supported water hexamers and a family of hydrated nanoclusters--heptamers, octamers and nonamers--through a combination of low-temperature scanning tunnelling microscopy experiments and first-principles electronic-structure calculations. Aside from achieving unprecedented resolution of the cyclic water hexamer--the so-called smallest piece of ice--we identify and explain a hitherto unknown competition between the ability of water molecules to simultaneously bond to a substrate and to accept hydrogen bonds. This competition also rationalizes previous structure predictions for water clusters on other substrates.

Extended Tapes of Cyclic Water Hexamers in an Unusual Oxalate-Bridged One-Dimensional Copper(II) Complex

Extended tapes of cyclic water hexamers are formed in a one-dimensional copper(II) complex bridged by oxalate with a rare mono, bidentate coordination mode. The water tapes are stabilized by the hydrogen bond interactions between uncoordinated oxalate oxygen atoms and water molecules. Magnetic analysis reveals weak ferromagnetic interactions mediated by the oxalate bridge with the exchange parameter J = 0.36 cm-1.

A planar cyclic hexamer of water molecules in dichlorido(2,4,6-tri-2-pyridyl-1,3,5-triazine)cadmium(II) trihydrate

In the title compound, [CdCl2(C(18)H(12)N(6))].3H2O, the Cd atom has a distorted square-pyramidal coordination geometry. The solvent water molecules are hydrogen bonded to each other to form planar cyclic water hexamers, which, together with other hydrogen bonds, interlink the Cd complex molecules to give one-dimensional supramolecular ribbons that extend along the [111] direction. The chains are assembled into two-dimensional layers parallel to (111) by pi-pi stacking interactions. Furthermore, interlayer pi-pi stacking interactions and weak C-H...Cl hydrogen bonds complete the formation of a three-dimensional framework.

Conformational study of Co(II), Ni(II), and Cr(III) complexes of the edta-type: Crystal structure of 1D polymeric trans(O 6)-Ba[Co(1,3-pddadp)] · 8H 2O complex stabilized by infinite water tapes

The trans(O 6) isomer of the Ba[Co(1,3-pddadp)] · 8H 2O complex (where 1,3-pddadp represents hexadentate 1,3-propanediamine- N, N′-diacetate- N, N′-di-3-propionate ion) has been prepared and characterized by X-ray crystallography. In the crystal structure the complex cations and anions are bridged by carboxylate oxygen atoms from the in-plane coordinated glycinate rings (G-rings) of [Co(1,3-pddadp)] 2− and by the barium-coordinated water molecules, thus forming 1D polymeric chains, separated by infinite water tapes hydrogen bonded to the [Co(1,3-pddadp)] 2− carboxylate oxygens from the out-of-plane β-alaninate rings (R-rings). Conformational analysis of the three possible geometrical isomers: trans(O 5), trans(O 5O 6), and trans(O 6) of the [Co(1,3-pddadp)] 2− complex, with ligand acting as hexadentate, as well as of the corresponding complexes of Ni(II) and Cr(III) has been performed using the consistent force field (CFF) method, with the parameters developed previously for edta-type complexes of chromium(III) and supplemented with new parameters for cobalt(II) and nickel(II). The energy-minimized structure of the trans(O 5O 6) isomer represents the global minimum for the [M(1,3-pddadp)] n− (M = Co(II), Ni(II), and Cr(III)) species. The occurrence of the least energetically favored trans(O 6) isomer in a crystal and the exceptional conformation of the axially oriented β-alaninate rings can be accounted for by the stabilizing role of the infinite tapes of planar cyclic water pentamers and hexamers which act as a “glue” to reinforce the coordination polymeric chains.

Crystallized Water: Internal and External Ice Fragments in Polycyclic Hosts

Two crystal structures of cyclic water hexamers are reported, one with a bicyclic cryptand and the other with a tricyclic host. In the bicycle structure, the water molecules lie between the cryptands. In the tricycle structure, the hexameric water cluster is almost totally encapsulated within the host framework.

Controllable assembly of a 3-D metal–organic supramolecular framework with the inclusion of a well-resolved 1-D water morph

Two mixed-ligand metal–organic complexes [Cd 2(adipato)(phen) 2(NO 3) 2(H 2O) 2](H 2O) 6 ( 1) and {[Cd(adipato)(phen)](H 2O) 3} n ( 2) have been synthesized upon the reaction of Cd(II) nitrate with 1,10-phenanthroline (phen) and adipate under similar conditions. For 1, the adipato-bridged dinuclear entities are extended into a 3-D supramolecular architecture via hydrogen bonds and π–π stacking. Interestingly, a well-resolved 1-D water morphology consisting of alternate cyclic water tetramer and hexamer is detected as the guests in each channel of this 3-D lattice. Whereas 2 represents a layered coordination polymer in which the Cd II centers are interlinked by adipate dianions via different coordination modes.