Polymeric (NO)3(N2O) n , (NO)3(N2O) n + , and (NO)3(N2O) n − : an interpretation of experimental observations

Semi-empirical and ab initio calculations are reported which provide a possible explanation for reported experimental results on 2-photon ionization of NO containing a few percent of N₂O, which found (NO)₃(N₂O) _n ^+or? clusters to be significantly more abundant than other (NO) _m (N₂O) _n products. It is found that the observed abundances of (NO)₃(N₂O) _n ionic clusters may be accounted for by the existence of covalent cyclic trimers of nitric oxide attached to oligomers of nitrous oxide. The extra stability of NO trimers in the observed clusters appears to arise from (NO) ₃ ⁺ rather than (NO)₃. Attachment of an (N₂O) _n side chain to (NO) ₃ ⁺ occurs exothermically. It is suggested that the addition of N₂O to cyclic-(NO) ₃ ⁺ might provide a means of making a polymer of nitrous oxide, which could have useful properties.     

Theoretical study of [Ni (H2O)n]2+(H2O)m (n ≤ 6, m ≤ 18)

The [Ni-(H(2)O)(n)](2+)(H(2)O)(m) (n ≤ 6, m ≤ 18) complexes were studied by means of first-principles all-electron calculations performed with the BPW91 gradient corrected functional and the 6-311+G(d,p) basis sets for the H, O, and Ni atoms. Triplet states were found as low-lying states for each (n, m) combination. The estimated Ni(2+)-(H(2)O)(n) binding energies (112.8-57.4 kcal/mol for the first layer and 52.0-23.0 kcal/mol for the second one) decreases and the Ni(2+)-OH(2) bond lengths lengthen as n + m increases. With six H(2)O moieties the Ni(2+) ion furnishes its first coordination sphere of octahedral geometry. Further water addition renders the formation of the second layer. The effect of Ni(2+) on the (H(2)O)(n)···(H(2)O)(m) hydrogen bond formation for several "n" and "m" combinations was studied, revealing an enhancement of this kind of bonding, which is of key importance for the stabilization and growth of the clusters. For some n + m isomers the second layer appears before the first octahedral layer is fully formed. For example, the square planar Ni(2+)-(H(2)O)(4) core originates two-dimensional 4 + 2 and 4 + 4 isomers, where each outer water molecule accepts two H-bonds, lying 2.0 kcal/mol above the 6 and 6 + 2 ground states. The clusters were also studied by IR spectra; the OH stretching vibrational frequencies allowed us to identify the outer solvation shells by the presence of red-shifted hydrogen bond regions.     

Density functional investigations on the (H2O)n·CCH and (H2O)n·HCC complexes (n=1–3)

The electronic structures and energies of (H₂O)_n·CCH and (H₂O)_n·HCC complexes (n=1–3) between CCH and water have been theoretically investigated at the UB3LYP/6-311++G(2df,p)//UB3LYP/6-311G(d,p) level. The complexes with n=2–3 are cyclic structures with homodromic hydrogen-bond chain. The (H₂O)_n·CCH (n=1–3) complexes show increasing stabilities towards CCH- or H₂O-eliminations of 2.3, 5.8 and 7.6 kcal/mol and are energetically more stable than the corresponding (H₂O)_n·HCC complexes by 0.8, 2.7 and 3.4 kcal/mol, respectively, due to the charge-separation-enhanced hydrogen bonds within (H₂O)_n·CCH (n=2,3). Strong interactions between CCH and (H₂O)₂ and (H₂O)₃ clusters suggest special solvent effects of water on the chemical behavior of unsaturated radicals.     

Reactions of CH3SH and CH3SSCH3 with gas-phase hydrated radical anions (H2O)n(•-), CO2(•-)(H2O)n, and O2(•-)(H2O)n

The chemistry of (H(2)O)(n)(?-), CO(2)(?-)(H(2)O)(n), and O(2)(?-)(H(2)O)(n) with small sulfur-containing molecules was studied in the gas phase by Fourier transform ion cyclotron resonance mass spectrometry. With hydrated electrons and hydrated carbon dioxide radical anions, two reactions with relevance for biological radiation damage were observed, cleavage of the disulfide bond of CH(3)SSCH(3) and activation of the thiol group of CH(3)SH. No reactions were observed with CH(3)SCH(3). The hydrated superoxide radical anion, usually viewed as major source of oxidative stress, did not react with any of the compounds. Nanocalorimetry and quantum chemical calculations give a consistent picture of the reaction mechanism. The results indicate that the conversion of e(-) and CO(2)(?-) to O(2)(?-) deactivates highly reactive species and may actually reduce oxidative stress. For reactions of (H(2)O)(n)(?-) with CH(3)SH as well as CO(2)(?-)(H(2)O)(n) with CH(3)SSCH(3), the reaction products in the gas phase are different from those reported in the literature from pulse radiolysis studies. This observation is rationalized with the reduced cage effect in reactions of gas-phase clusters.     

Rate constants of atomic hydrogen formation in H3O+(H2O) n + e → H + (H2O) n gas-phase processes

Using the Maxwellian electron velocity distribution and the Breit-Wigner approximation of the reaction cross section, the kinetic parameters of the hydrogen atom formation upon the electron capture by positively charged hydronium-water clusters are estimated. Calculations of the cross sections and rate constants are based on the data of quantum chemical studies of H₃O⁺(H₂O) _n and H₃O(H₂O) _n clusters, particularly on the detailed analysis of the spacing of high-lying states of the radicals and the character of the unpaired electron density distribution, as well as on the general trend in the electron affinity change of the cations depending on the number of water molecules. The lifetimes of the radicals before the dissociation are taken from the classical nonempirical molecular dynamics runs. The results are compared to available experimental data. The article is published in the original.     

Photoelectron spectroscopy of (CO2)n(H2O) m − clusters

Photoelectron spectra of (CO₂)_nH₂O^? (2≤n≤8) and (CO₂)_n(H₂O) ₂ ^? (1≤n≤2) were measured at the photon energy of 3.49 eV. The spectra show unresolved broad features, which are approximated by Gaussians. The vertical detachment energies (VDEs) were determined as a function of the cluster size. For (CO₂)_nH₂O^?, the VDE-n plots exhibit a sharp discontinuity between n=3 and 4; the VDE value is ≈3.5 eV at n=3, while it drops down abruptly to 2.59 eV at n=4. This discontinuity in VDE is ascribed to "core switching" at n=4; a C₂O ₄ ^? dimer anion forms the core of (CO₂)_nH₂O^? for n≤3, while a monomer CO ₂ ^? is the core for n≥4. The (CO₂)₂(H₂O) ₂ ^? ion has a VDE of 2.33 eV, indicating the presence of a CO ₂ ^? monomer core in the binary clusters containing two H₂O molecules.     

Gas phase reactions of Cl2O with X−(D2O)n=0–4 (X = O,OD, O2, DO2, and O3)

The reactions of Cl₂O with the cluster ions X⁻(D₂O)_n=0–4 (X = O, OD, O₂, DO₂, and O₃) were studied in a He buffer gas at temperatures within the range 171–298 K and pressures of 0.27–0.51 Torr, using a flow-tube apparatus. All ions were found to react with Cl₂O at rates slower than predicted by the collision rate and the charge center was transferred from X⁻ to Cl⁻ or ClO⁻. The primary product ions Cl⁻(DOCl) and ClO⁻(DOCl) were observed to react further to produce the ions Cl₃O⁻ and Cl₃O₂⁻. The rate constants for the observed reactions are reported and the role that thermodynamics plays in determining possible reaction channels is discussed.     

Production of doubly charged clusters (H2O)n · Ba2+ and (H2O)n · Ca2+ under low temperature fast atom bombardment conditions

Production of doubly charged ions of alkaline earth metals Ba²⁺ and Ca²⁺ and their doubly charged clusters with water molecules (H₂O)_n · Ba²⁺, (H₂O)_n · Ca²⁺ (n = 1, 2, 3) by means of low temperature fast atom bombardment technique is observed in the case of crystalline hydrates of BaCl₂ and CaCl₂ salts, formed during freezing of water-salt solutions. Reasons for a possibility of production of the doubly charged species in the case of the two indicated salts and their absence in the case of chlorides of some other divalent metals (Mg, Mn, Co, Cu, Zn) are discussed. As to singly charged secondary ions Me⁺, MeCl⁺, MeOH⁺, [(H₂O)_n · MeCl]⁺, [(H₂O)_n · MeOH]⁺ (where Me is metal), high efficiency of their production from crystalline hydrates was observed and possible explanation of the phenomenon is suggested.     

Structurally nonrigid molecular complexes (HF)n(H2O)m (n + m ≥ 2) and their spectroscopic features

The problem of the formation and stability of structurally nonrigid, donor—acceptor molecular complexes is considered. These complexes are formed between the molecules of water and hydrogen fluoride, the latter being the hydrolysis product of the chemical, radiochemical, and metallurgical industrial wastes. Based on the results of ab initio quantum-chemical calculations of the potential energy surfaces by the Hartree—Fock—Roothaan method, the equilibrium configurations of the (H₂O) _n (HF) _m complexes (n : m = 1 : 1; 1 : 2; 2 : 1; 2 : 2; and 3 : 3) were determined. These configurations are necessary for correct interpretation of the IR absorption spectra and for routine remote monitoring of such environmentally hazardous complexes in the Earth atmosphere. The harmonic vibrational frequencies of the (H₂O) _n (HF) _m complexes (n + m 2) were calculated and the interaction energies between the monomers were found. The influence of UV radiation on the (H₂O) _n (HF) _n complexes (n = 1—3) upon the transition from the ground to the lowest excited singlet electronic state was studied. Characteristic spectroscopic features of the (H₂O) _n (HF) _m complexes were established.     

H3+O和H3+O(H2O)n(n=1,2,3)阳离子振动力场和光谱频率的理论计算

本文利用多原子分子振动力场的模型势函法对H₃⁺O和H₃⁺O(H₂O)_n(n=1～3)阳离子的振动力场作了理论计算,并对其光谱频率进行了预测.H₃⁺O和H₉⁺O₄的振动频率的结果优于从头算梯度法的结果.本文首次给出了H₅⁺O₂、H₇⁺O₃伸缩振动频率的理论预测值.     

Theoretical Studies on the Intermonomer Interaction of F-·(H2O)n (n = 1,2)

Five optimized geometries of F-·(H2O)n (n = 1, 2) were obtained with ab initio calculation at the B3LYP/6-311++G** level.The accurate intermonomer interaction energy was calculated using the MP2 electron correlation correction as well as the basis set superposition error correction by the Boys-Bernardi "counterpoise" protocol.Natural bond orbital (NBO) theory was applied to quantify the relative strength of these interactions and account for their effects on the stability, structural and vibrational parameters of Fˉ·(H2O)n (n = 1, 2).It is shown that the charge transferring from the lone pair of F-1 to the σ*OH(…F) antibonding orbital is important.The results indicate the occupancy of σ*OH(…F) is increased (denoted Δσ*OH(…F)) and the ΔROH(…F) bond is leng- thened (denoted (ROH(…F)), leading to the red-shift and the red-shift values have linear correlation with both Δσ*OH(…F) and ΔROH(…F).     

Ab initio electron correlated studies on the intracluster reaction of NO+ (H2O)(n) → H3O+ (H2O)(n-2) (HONO) (n = 4 and 5)

Hydrated nitrosonium ion clusters NO(+)(H(2)O)(n) (n = 4 and 5) were investigated by using MP2/aug-cc-pVTZ level of theory to clarify isomeric reaction pathways for formation of HONO and fully hydrated hydride ions. We found some new isomers and transition state structures in each hydration number, whose lowest activation energies of the intracluster reactions were found to be 4.1 and 3.4 kcal mol(-1) for n = 4 and n = 5, respectively. These thermodynamic properties and full quantum mechanical molecular dynamics simulation suggest that product isomers with HONO and fully hydrated hydride ions can be obtained at n = 4 and n = 5 in terms of excess hydration binding energies which can overcome these activation barriers.     

Halide substitutions in the [Rh2(O f2 p− )(OH)2(H2O) n ]3+ complex

Summary Transition metal complexes containing activated dioxygen continue to attract considerable attention and are widely used as models, either as oxygen carriers or as catalysts in biological and industrial oxidations ^(1,2).Cobalt complexes containing the coordinated O₂ molecule are well known^(3,4), but the rhodium analogues are rare^(5–8). The known complexes with coordinated O₂ are rhodium(III) compounds containing strong nitrogen donor ligands.Our recent studies have focused on a synthesis of dioxygen rhodium derivatives in which a superoxide anion (O _f2 ^p– ) is bound to the [Rh^III—Rh^III] core surrounded by other donor molecules, e.g. H₂O, RCO _f2 ^p– (7,8), to investigate the effect of a coordination sphere of the metal centre on the redox properties of the O _f2 ^p– radical combined to it⁽⁹⁾.The [Rh₂(O _f2 ^p– )(OH)₂(H₂O) _n ]³⁺ cation, the product of oxidative addition of dioxygen to the [Rh₂(H₂O)₁₀]⁴⁺ dimer, was isolated by us and examined in aqueous HC1O₄ ^(7,9). So far we have been unable to isolate its solid but the water molecules coordinated to the [Rh₂(O _f2 ^p– )-(OH)₂] ³⁺ moiety were found to undergo substitution relatively easily⁽⁸⁾.     

{[Sr(CHZ)2(H2O)]·(NTO)2·3.5H2O}n的制备和晶体结构

将SrCO3与3-硝基-1, 2, 4-三唑-5-酮(NTO)分散于蒸馏水中,加热搅拌制备出NTO锶溶液,再与碳酰肼(CHZ)水溶液反应合成了新型配合物:{[Sr(CHZ)2(H2O)]?NTO)2?.5H2O}n。 其化学式为 C6H23N16O12.5Sr,Mr=606.97),并对其进行了元素分析和红外表征,利用单晶分析测定了晶体结构。晶体属于单斜晶系,空间群为C2/c,晶体学数据如下:a=24.587(5), b=12.689(2), c=16.481(4) ? =121.15(1)埃琕=4400.4(2) ?,Z=8,Dc=1.833 g/cm3,?= 0.255 cm-1, F(000) = 2472,R=0.0989,wR=0.0750。     

Assessment of multicoefficient correlation methods, second-order Møller-Plesset perturbation theory, and density functional theory for H3O(+)(H2O)n (n = 1-5) and OH(-)(H2O)n (n = 1-4)

We have assessed the ability of 52 methods including 15 multicoefficient correlation methods (MCCMs), two complete basis set (CBS) methods, second-order M?ller-Plesset perturbation theory (MP2) with 5 basis sets, the popular B3LYP hybrid functional with 6 basis sets, and 24 combinations of local density functional and basis set to accurately reproduce reaction energies obtained at the Weizmann-1 level of theory for hydronium, hydroxide, and pure water clusters. The three best methods overall are BMC-CCSD, G3SX(MP3), and M06-L/aug-cc-pVTZ. If only microsolvated ion data is included, M06-L/aug-cc-pVTZ is the best method; it has errors only half as large as the other density functionals. The deviations between the three best performing methods are larger for the larger hydronium- and hydroxide-containing clusters, despite a decrease in the average reaction energy, making it impossible to determine which of the three methods is overall the best, so they might be ranked in order of increasing cost, with BMC-CCSD least expensive, followed by M06-L/aug-cc-pVTZ. However, the cost for M06-L will increase more slowly as cluster size increases. This study shows that the M06-L functional is very promising for condensed-phase simulations of the transport of hydronium and hydroxide ions in aqueous solution.     

Syntheses and crystal structures of two Cd(II) coordination polymers: one-dimensional chain [Cd(C4H6N2)2(C4H2O4)(H2O)2] n and two-dimensional sheet [Cd(C4H6N2)(H2O)(C4H4O4)] n · n H2O

Two new Cd(II) coordination polymers, [Cd(C₄H₆N₂)₂(C₄H₂O₄)(H₂O)₂] _n (1) (where C₄H₆N₂?=?2-methylimidazole, C₄H₂O₄?=?fumarate), and [Cd(C₄H₆N₂)(H₂O)(C₄H₄O₄)] _n ?·?nH₂O (2), (where C₄H₄O₄?=?succinates), have been prepared and structurally characterized by single crystal X-ray diffraction. Complex 1 crystallizes in the triclinic space group P 1 in a one-dimensional chain structure, in which carboxy is monodentate; a three-dimensional supermolecular network structure was formed through hydrogen bonding. In complex 2, the coordination geometry of the Cd atoms is a pentagonal bipyramid, and a two-dimensional sheet is formed though carboxyl group bridging. In 1 and 2, IR spectra indicate the presence of bridging carboxyl groups, confirmed by structure analyses.     

Syntheses and structures of p-HOOCC6F4COOH · H2O (H2L · H2O) and luminescent coordination polymers [Tb2(H2O)4(L)3 · 2H2O] n and Tb2(Phen)2(L)3 · 2H2O

Compounds p-HOOCC₆F₄COOH · H₂O (H₂L · H₂O), [Tb₂(H₂O)₄(L)₃ · 2H₂O] _n (I), and Tb₂(Phen)₂(L)₃ · 2H₂O (II) are synthesized. According to the X-ray structure analysis data, the crystal structure of H₂L · H₂O is built of centrosymmetric molecules H₂L and molecules of water of crystallization. The crystal structure of compound I is built of layers of coordination 2D polymer [Tb₂(H₂O)₄(L)₃] _n and molecules of water of crystallization. The ligands are the L^2? anions performing both the tetradentate bridging and pentadentate bridging-chelating functions. The coordination polyhedron TbO₉ is a distorted three-capped trigonal prism. Acid H₂L manifests photoluminescence in the UV region (??_max = 368 nm). Compounds I and II have the green luminescence characteristic of the Tb³⁺ ions, and the band with ??_max = 545 nm (transition ⁵ D ₄?? ⁷ F ₅) is maximum in intensity. The photoluminescence intensity of compound II is higher than that for compound I.     

Unique seven-node rare-earth octacyanomolybdate(IV) three-dimensional molecular frameworks: {[Er(H2O)5(Er(H2O)4)3][Mo(CN)8]3·11H2O}n and {[Eu(H2O)5(Eu(H2O)4)3][Mo(CN)8]3·11H2O}n

The crystal structure analyses of {[Er(H₂O)₅(Er(H₂O)₄)₃][Mo(CN)₈]₃·11H₂O}_n (1) and {[Eu(H₂O)₅(Eu(H₂O)₄)₃][Mo(CN)₈]₃·11H₂O}_n (2), show that they are not only new neutral three-dimensional rare-earth octacyanomolybdate(IV) molecular frameworks, but that they also belong to an unknown structure type having seven different nodes. To the best of our knowledge this is different to any other known molybdenum(IV) octacyanide complexes published to date. Both compounds crystallize in the triclinic system, space group P-1, and are isostructural and isotypic. The coordination polyhedra of the molybdenum atoms in the three different [Mo(CN)₈]⁴⁻ anions are trigonal prisms, with two additional atoms. A new bridging mode for octacyanometallates is also observed with five of the eight cyanide groups involved in bridging either three or four rare-earth atoms, while the three remaining cyanide groups are terminal and are involved in hydrogen bonding. The four rare-earth atoms in 1 and 2 have different coordination polyhedra in the form of trigonal prisms with two additional atoms. The three-dimensional structures are made up of infinite two-dimensional slabs linked by one of the rare-earth metal atoms. In both compounds, apart from the 17 coordinated water molecules, there are 11 lattice water molecules of crystallization present in the cavities of the three-dimensional frameworks. The 28 water molecules and the terminal CN⁻ groups are involved in an extensive O–H⋯O and O–H⋯N hydrogen bonding network.     

Observation of the novel “three-pointed star” cage-like (H2O)5 cluster in a polymeric solid {[Ag2(bpp)2(H2O)2](chd)·9H2O} n

Coordination polymeric solid, {[Ag₂(bpp)₂(H₂O)₂](chd)·9H₂O} _n (1) (bpp = 1,3-bis(4-pyridyl) propane, H₂chd = 1,4-cyclo-hexanedicarboxylic acid), has been obtained by the solution phase ultrasonic synthesis techniques. The structure established through X-ray structural analysis shows that the compound traps an interesting 1D water tape built by the alternating ??three-pointed star?? cage-like pentameric and D _2h tetrameric clusters (C2/c, Z = 4; a = 30.37(2) ?, b = 9.271(5) ?, and c = 18.89(1) ?; ?? = 128.47°; V = 4164(4) ?³). The novelty of the present complex is the rarely crystallographic example of the cage-shaped water pentamer, which is usually ascribed to a less-stable species. A first-principle density functional theory (DFT) calculation demonstrates that the interconnectivity between cage-like pentamers and D _2h tetramers is beneficial for contribution to the structural stabilization of these less-stable water cluster species.     

(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)簇结构及其热力学性质

用HF自洽场理论和密度泛函理论(DFT)的B3LYP方法,在6 31G水平上研究了低聚物(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)簇的几何构型、电子结构和聚合反应热力学性质,比较了两个系列化合物中化学键的强度.结果表明,Cl2AlNH2和H2AlNH2分子为C2 (EC)平面型结构,其中Al－N为由一个σ键和一个键组成的双键.(Cl2AlNH2)n和(H2AlNH2)n(n=1～5)分子为Dnh对称,Al－N是典型的σ单键 .低聚物(Cl2AlNH2)n和(H2AlNH2)n的稳定性顺序分别为: 3 > 2 > 4> 5 > 1和8 > 7 > 9 > 11 > 6.