一种新的有机胺为模板剂的稀土硫酸钐合成，结构表征以及荧光性质

本文采用正丁醇与水的混合溶剂合成一种新的以有机胺为模板剂的硫酸钐盐:[C2N2H10]1.5[Sm(SO4)3(H2O)].2H2O(1),并通过X-射线衍射、红外、热重及元素分析对其进行了表征。该化合物晶体属于单斜晶系,P21/c空间群。其中a=0.65515(9)nm,b=2.648 3(4)nm,c=0.996 15(13)nm,β=104.067 0(10)°,V=1.676 5(4)nm3,Z=4。晶体结构分析显示化合物1中的波浪形层状结构由SmO9多面体与SO4多面体构成,同时非配位水与乙二胺通过氢键连接相邻的两个层。化合物1具有较强的荧光。     

catena‐Poly[[[pentaaquathulium(III)]‐μ‐5‐sulfonatobenzene‐1,3‐dicarboxylato] 4,4′‐bipyridyl 1.5‐solvate hemihydrate]

The crystal structure of the title compound, {[Tm(C₈H₃O₇S)(H₂O)₅]·1.5C₁₀H₈N₂·0.5H₂O}_n, is built up from two [Tm(SIP)(H₂O)₅] molecules (SIP³⁻ is 5‐sulfonatobenzene‐1,3‐dicarboxylate), three 4,4′‐bipyridyl (bpy) molecules and one solvent water molecule. One of the bpy molecules and the solvent water molecule are located on an inversion centre and a twofold rotation axis, respectively. The Tm^III ion coordination is composed of four carboxylate O atoms from two trianionic SIP³⁻ ligands and five coordinated water molecules. The Tm³⁺ ions are linked by the SIP³⁻ ligands to form a one‐dimensional zigzag chain propagating along the c axis. The chains are linked by interchain O—H...O hydrogen bonds to generate a two‐dimensional layered structure. The bpy molecules are not involved in coordination but are linked by O—H...N hydrogen bonds to form two‐dimensional layers. The two‐dimensional layers are further bridged by the bpy molecules as pillars and the solvent water molecules through hydrogen bonds, giving a three‐dimensional supramolecular structure. π–π stacking interactions between the parallel aromatic rings, arranged in an offset fashion with a face‐to‐face distance of 3.566 (1) Å, are observed in the crystal packing.     

Poly[[diaqua(μ3‐3‐nitrophthalato)calcium(II)] monohydrate]

The title 3‐nitrophthalate–calcium coordination polymer, {[Ca(C₈H₃NO₆)(H₂O)₂]·H₂O}_n, crystallizes as a one‐dimensional framework. The Ca^II centre has a distorted pentagonal–bipyramidal geometry, being seven‐coordinated by five O atoms from three different 3‐nitrophthalate groups and by two water molecules, resulting in a one‐dimensional zigzag chain along the a‐axis direction by the interconnection of the four O atoms from the two carboxylate groups. There is a D3 water cluster composed of the coordinated and the solvent water molecules within such chains. Adjacent chains are aggregated into two‐dimensional layers via hydrogen bonds in the c‐axis direction. The whole three‐dimensional structure is further stabilized by weak O—H...O hydrogen bonds between the O atoms of the nitro group and the water molecules.     

Structure and hydration of L-proline in aqueous solutions

The structure and hydration of L-proline in aqueous solution have been investigated using a combination of neutron diffraction with isotopic substitution, empirical potential structure refinement modeling, and small-angle neutron scattering at three concentrations, 1:10, 1:15, and 1:20 proline/water mole ratios. In each solution the carboxylate oxygen atoms from proline accept less than two hydrogen bonds from the surrounding water solvent and the amine hydrogen atoms donate less than one hydrogen bond to the surrounding water molecules. The solute-solute radial distribution functions indicate relatively weak interactions between proline molecules, and significant clustering or aggregation of proline is absent at all these concentrations. The spatial density distributions for the hydration of the COO- group in proline show a similar shape to that found previously in L-glutamic acid in aqueous solution but with a reduced coordination number.     

A new structure of water layer on Cu(111) electrode surface during hydrogen evolution

A layered structure of water molecules formed on a Cu(111) electrode surface during hydrogen evolution in sulfuric acid solution was studied by surface X-ray diffraction and infrared reflection absorption methods. Water molecules in the surface layers take a closest pack-like stacking structure with nearest-neighbor oxygen-oxygen distances in intra-(0.322(5) nm) and inter-(0.275(15) nm) layers of multi-domains; the infrared spectra of the layered water on the Cu electrode surface showed the existence of free OH(OD) and hydrogen-bonded OH(OD) of water molecule.     

Kinetic insights into the role of the solvent in the polymorphism of 5-fluorouracil from molecular dynamics simulations

We investigate the fundamental factors controlling polymorphism in 5-fluorouracil by performing molecular dynamics simulations of solutions of the compound in water, nitromethane, and wet nitromethane. Analysis of the effect of solvent on the initial aggregation of 5-fluorouracil molecules shows that the strong binding of water to the 5-fluorouracil molecule hinders the formation of the doubly hydrogen-bonded dimer and, by default, promotes close hydrophobic F...F interactions that are a feature of the unusual (Z' = 4) structure of form I. In contrast, doubly hydrogen-bonded dimers are observed to form readily in solution in dry nitromethane, consistent with the crystallization of the doubly hydrogen-bonded ribbon structure of form II from this solvent. When nitromethane is doped with water, the water forms hydrogen bonds to the solute, interfering with the formation of the doubly hydrogen-bonded dimers, which is consistent with the crystallization of form I from this hygroscopic solvent when it is not dried. Overall, the molecular dynamics simulations provide an atomistic picture of how solvent-solute interactions can significantly affect the initial association of 5-fluorouracil molecules to the extent that they determine the polymorphic outcome of the crystallization.     

Poly[[diaqua(μ3‐2,2‐dimethylmalonato)cadmium(II)] tetrahydrate]

In the title complex, {[Cd(C₅H₆O₄)(H₂O)₂]·4H₂O}_n, the dimethylmalonate–cadmium metal–organic framework co‐exists with an extended structure of water molecules, which resembles a sodalite‐type framework. In the asymmetric unit, there are five independent solvent water molecules, two of which are in special positions. The Cd atoms are eight‐coordinated in a distorted square‐antiprismatic geometry by six O atoms of three different dimethylmalonate groups and by two water molecules, and form a two‐dimensional honeycomb layer parallel to the bc plane. Two such layers sandwich the hydrogen‐bonded water layer, which has a sodalite‐type structure with truncated sodalite units composed of coordinated and solvent water molecules. This work is the first example of a dimethylmalonate cadmium complex containing truncated sodalite‐type water clusters.     

Influence of anions on the dimensionality of extended networks based on Cu I cations and 1,4,5,8,9,12-hexaazatriphenylene (HAT) ligands

Reactions of Cu I salts with 1,4,5,8,9,12-hexaazatriphenylene (HAT) afford three types of cationic coordination polymers depending on the anion present in the reaction solution. In the crystal structure of {[Cu(HAT)][BF4]x1/3(C6H6)}infinity, (1), Cu ions and HAT molecules form extended layers that are best described as strongly distorted honeycomb nets. The space between the layers is occupied by [BF4]- anions and solvent molecules. {[Cu(HAT)][PF6]}infinity, (2), crystallizes as a chiral (10,3)-a net with [PF6]- anions residing in the cavities of the three-dimensional metal-organic framework. The crystal structure of {[Cu4(HAT)3][SbF6]4x3C6H6}infinity, (3), is based on unique extended [Cu4(HAT)3]infinity "nanotubules" filled with solvent molecules and [SbF6]- anions.     

FTIR study on molecular structure of poly(N-isopropylacrylamide) in mixed solvent of methanol and water

The intrachain and interchain hydrogen bonding of poly(N-isopropylacrylamide) (PNIPA) and intermolecular hydrogen bonding between PNIPA chains and the solvent molecules in the mixed solvent of methanol and water have been quantitatively investigated by using Fourier transform infrared (FTIR) spectroscopy at 25 °C. In this spectroscopic system with curve fitting program, we found that in the C-H stretching region, both the N-isopropyl group and the backbone underwent conformational change upon the solvent composition. An analysis of the amide I band suggested that the amide groups of PNIPA were mainly involved in intermolecular hydrogen bonding with water molecules, and the polymer chains were flexible and disordered in the mixed solvent when the methanol volume fraction (χ_v) was lower than 15%. While χ_v was in the range of 15-65%, about 30% of these intermolecular hydrogen bonding between the polymer and water were replaced by intrachain and interchain hydrogen bonding, consequently, PNIPA shrinked as aggregates. If χ_v was above 65%, the interchain hydrogen bonding became predominant due to the solubility characteristics of amphiphilic methanol, and the PNIPA system was homogeneous solution again. We believe that the reentrant transition is related to the weaker interaction between PNIPA molecules and methanol-water complexes, (H₂O)_m(CH₃OH)_n (m/n = 5/1, 5/2, 5/3, 5/4, 5/5) as compared to that between PNIPA and free water or free methanol.     

溶剂对镍（域）金属有机骨架结构的影响

通过乙酸镍和4-咪唑-1-基-苯甲酸( HL)在不同溶剂热条件下合成了3个新型金属有机骨架化合物[Ni(L)2]n·DMF(1), Ni(H2 O)2(L)2(2)和 Ni(L)2(CH3 OH)2(3)。化合物1是用 N,N-二甲基甲酰胺(DMF)作为溶剂合成的具有菱形孔道的三维骨架化合物;化合物2是在DMF/H2O(体积比4︰1)中合成的水作为终端配体参与配位的二维层状化合物,并通过层与层之间的氢键作用构筑形成了三维超分子结构;当溶剂为甲醇时,得到了二维层状化合物3,且甲醇作为终端配体参与配位。磁学和电化学性质研究结果表明,化合物1~3中相邻镍离子之间存在反铁磁相互作用;在一定的电势范围内出现一对明显的Ni (Ⅱ)/Ni(Ⅲ)氧化还原峰,表明化合物1~3是潜在的磁性材料或电催化剂材料。     

Structural studies on the hydration of L-glutamic acid in solution

A combination of neutron diffraction augmented with isotopic substitution and computer modeling using empirical potential structure refinement has been used to extract detailed structural information for L-glutamic acid dissolved in 2 M NaOH solution. This work shows that the tetrahedral hydrogen bonding network in water is severely disrupted by the addition of glutamic acid and NaOH, with the number of water-water hydrogen bonds being reduced from 1.8 bonds per water molecule in pure water to 1.4 bonds per water molecule in the present solution. In the glutamic acid molecule, each carboxylate oxygen atom forms an average of three hydrogen bonds with the surrounding water solvent with one of these hydrogens being shared between the two oxygen atoms on each carboxylate group, while each amine hydrogen forms a single hydrogen bond with the surrounding water solvent. Additionally, the average conformation of the glutamic acid molecules in these solutions is extracted.     

水和甲醇混合溶剂氢键相互作用及对高分子链溶解能力的理论研究

用密度泛函理论对水和甲醇混合溶剂体系的氢键结构进行了详细研究.通过构象和频率分析发现在水团簇中五聚体和六聚体环状结构最为稳定,同时发现一个全新的特征,即甲醇分子能与水五聚体和六聚体形成双氢键.根据各相互作用的稳定化能,分析了水和甲醇混合溶剂对PNIPAM溶解能力的影响,并对实验现象给予了合理解释.     

Formation of a hydrogen-bonded heptazine framework by self-assembly of melem into a hexagonal channel structure

Self-assembly of melem C(6)N(7)(NH(2))(3) in hot aqueous solution leads to the formation of hydrogen-bonded, hexagonal rosettes of melem units surrounding infinite channels with a diameter of 8.9 ?. The channels are filled with strongly disordered water molecules, which are bound to the melem network through hydrogen bonds. Single-crystals of melem hydrate C(6)N(7)(NH(2))(3)?xH(2)O (x≈2.3) were obtained by hydrothermal treatment of melem at 200 °C and the crystal structure (R ?3c, a=2879.0(4), c=664.01(13) pm, V=4766.4(13)×10(6) pm(3), Z=18) was elucidated by single-crystal X-ray diffraction. With respect to the structural similarity to the well-known adduct between melamine and cyanuric acid, the composition of the obtained product was further analyzed by solid-state NMR spectroscopy. Hydrolysis of melem to cyameluric acid during syntheses at elevated temperatures could thus be ruled out. DTA/TG studies revealed that, during heating of melem hydrate, water molecules can be removed from the channels of the structure to a large extent. The solvent-free framework is stable up to 430 °C without transforming into the denser structure of anhydrous melem. Dehydrated melem hydrate was further characterized by solid-state NMR spectroscopy, powder X-ray diffraction, and sorption measurements to investigate structural changes induced by the removal of water from the channels. During dehydration, the hexagonal, layered arrangement of melem units is maintained whereas the formation of additional hydrogen bonds between melem entities requires the stacking mode of hexagonal layers to be altered. It is assumed that layers are shifted perpendicular to the direction of the channels, thereby making them inaccessible for guest molecules.     

Solvothermal Synthesis,Crystal Structure and Properties of a New Organic Templated Lanthanum Sulfate [C4N3H16][La(SO4)3(H2O)]

A new organic templated lanthanum sulfate [C₄N₃H₁₆][La(SO₄)₃(H₂O)] ( 1 ) has been solvothermally synthesized by using n‐butanol as solvent. The colorless block crystals were characterized by IR, TGA, ICP, and XRD. The structure was determined by single‐crystal X‐ray diffraction: Monoclinic, P2₁/c, a = 10.8878(19), b = 15.478(3), c = 9.9639(18) Å, β = 114.062(2)°, V=1533.2(5) ų, Z = 4]. Crystal structure analysis shows that the one dimensional chain of 1 consists of the LaO₉ polyhedra and the sulfate groups. Coordination water molecules link adjacent chains by using hydrogen bonds to generate 2D layers, whereas the organic amines are inserted between the layers. The formation of 1 demonstrates that solvents play an important role during the synthesis.     

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(C₁₈H₁₂N₆)]·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 π–π stacking interactions. Furthermore, interlayer π–π stacking interactions and weak C—H...Cl hydrogen bonds complete the formation of a three‐dimensional framework.     

Supramolecular formation of large hydrogen-bonded rings in the structures of two amino acid derivatives

Two new amino acid derivatives N-(2-oxopyrrolidin-1-ylmethyl)-l-valine (PMV) and N,N-bis(2-oxopyrrolidin-1-ylmethyl)-β-alanine (PMA) were synthesized and their structures were determined by single crystal X-ray crystallography. The geometry and conformation of both molecular aggregates and their hydrogen bond networks are not similar. In the PMV crystal structure, PMV and the solvent water molecule are linked by O–H⋯O intermolecular hydrogen bonds resulting in two ring motifs R₁₂¹²(48) and R₄⁴(22). A three-dimensional supramolecular structure is formed by hydrogen bonds N–H⋯O between the layers. In the PMA crystal structure, each water molecule connects three PMA molecules through O–H⋯O intermolecular hydrogen bonds, and a ring motif R₄⁴(24) is formed in the structure. But there is no hydrogen bond interaction between the layers, in which van der Waals' interaction is involved only.     

Correlations in liquid water for the TIP3P-Ewald, TIP4P-2005, TIP5P-Ewald, and SWM4-NDP models

Water is one of the simplest molecules in existence, but also one of the most important in biological and engineered systems. However, understanding the structure and dynamics of liquid water remains a major scientific challenge. Molecular dynamics simulations of liquid water were performed using the water models TIP3P-Ewald, TIP4P-2005, TIP5P-Ewald, and SWM4-NDP to calculate the radial distribution functions (RDFs), the relative angular distributions, and the excess enthalpies, entropies, and free energies. In addition, lower-order approximations to the entropy were considered, identifying the fourth-order approximation as an excellent estimate of the full entropy. The second-order and third-order approximations are ~20% larger and smaller than the true entropy, respectively. All four models perform very well in predicting the radial distribution functions, with the TIP5P-Ewald model providing the best match to the experimental data. The models also perform well in predicting the excess entropy, enthalpy, and free energy of liquid water. The TIP4P-2005 and SWM4-NDP models are more accurate than the TIP3P-Ewald and TIP5P-Ewald models in this respect. However, the relative angular distribution functions of the four water models reveal notable differences. The TIP5P-Ewald model demonstrates an increased preference for water molecules to act both as tetrahedral hydrogen bond donors and acceptors, whereas the SWM4-NDP model demonstrates an increased preference for water molecules to act as planar hydrogen bond acceptors. These differences are not uncovered by analysis of the RDFs or the commonly employed tetrahedral order parameter. However, they are expected to be very important when considering water molecules around solutes and are thus a key consideration in modelling solvent entropy.     

Preparation of Superconducting Na(x)(H2O)yCoO2 using NaMnO4 as the deintercalation and oxidation agent

We have used aqueous NaMnO4 solution as the deintercalation and oxidation agent to treat gamma-Na0.7CoO2 powders and to successfully obtain superconducting sodium cobalt oxyhydrates, Nax(H2O)yCoO2, with onset Tc approximately 4.6 K without using highly toxic Br2/CH3CN solution. Chemical analyses indicate that the sodium content x decreases with increasing concentration of NaMnO4 solution and depends slightly on the immersion time. Unlike using a high concentration of aqueous KMnO4 as the deintercalation and oxidation agent, all the hydrated products are the c approximately 19.6 A phase with bilayers of water molecules intercalated between the CoO2 layers and sodium layers because of the absence of K+ in the Na+ layers.     

Mechanism of OH radical hydration: a comparative computational study of liquid and supercritical solvent

Flexible models of the radical and water molecules including short-range interaction of hydrogen atoms have been employed in molecular dynamic simulation to understand mechanism of (●)OH hydration in aqueous systems of technological importance. A key role of H-bond connectivity patterns of water molecules has been identified. The behavior of (●)OH(aq) strongly depends on water density and correlates with topological changes in the hydrogen-bonded structure of water driven by thermodynamic conditions. Liquid and supercritical water above the critical density exhibit the radical localization in cavities existing in the solvent structure. A change of mechanism has been found at supercritical conditions below the critical density. Instead of cavity localization, we have identified accumulation of water molecules around (●)OH associated with the formation of a strong H-donor bond and diminution of non-homogeneity in the solvent structure. For all the systems investigated, the computed hydration number and the internal energy of hydration Δ(h)U showed approximately linear decrease with decreasing density of the solvent but a degree of radical-water hydrogen bonding exhibited non-monotonic dependence on density. The increase in the number of radical-water H-acceptor bonds is associated with diminution of extended nets of four-bonded water molecules in compressed solution at ~473 K. Up to 473 K, the isobaric heat of hydration in compressed liquid water remains constant and equal to -40 ± 1 kJ mol(-1).