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1.
The cooperative effects of hydrogen bonding in small water clusters (H 2O) n ( n=3–6) have been studied by using the partition of the electronic energy in accordance with the interacting quantum atoms (IQA) approach. The IQA energy splitting is complemented by a topological analysis of the electron density ( ρ( r )) compliant with the quantum theory of atoms‐in‐molecules (QTAIM) and the calculation of electrostatic interactions by using one‐ and two‐electron integrals, thereby avoiding convergence issues inherent to a multipolar expansion. The results show that the cooperative effects of hydrogen bonding in small water clusters arise from a compromise between: 1) the deformation energy (i.e., the energy necessary to modify the electron density and the configuration of the nuclei of the isolated water molecules to those within the water clusters), and 2) the interaction energy ( Eint) of these contorted molecules in (H 2O) n. Whereas the magnitude of both deformation and interaction energies is enhanced as water molecules are added to the system, the augmentation of the latter becomes dominant when the size of the cluster is increased. In addition, the electrostatic, classic, and exchange components of Eint for a pair of water molecules in the cluster (H 2O) n?1 become more attractive when a new H 2O unit is incorporated to generate the system (H 2O) n with the last‐mentioned contribution being consistently the most important part of Eint throughout the hydrogen bonds under consideration. This is opposed to the traditional view, which regards hydrogen bonding in water as an electrostatically driven interaction. Overall, the trends of the delocalization indices, δ( Ω, Ω′), the QTAIM atomic charges, the topology of ρ( r ), and the IQA results altogether show how polarization, charge transfer, electrostatics, and covalency contribute to the cooperative effects of hydrogen bonding in small water clusters. It is our hope that the analysis presented in this paper could offer insight into the different intra‐ and intermolecular interactions present in hydrogen‐bonded systems. 相似文献
2.
The effect of solvation on the conformation of acetylene has been studied by adding one water molecule at a time. Quantum chemical calculations of the H +(C 2H 2)(H 2O) n ( n=1-5) clusters indicate that the H 2O molecules prefer to form the OH… π interaction rather than the CH…O interaction. This solvation motif is different from that of neutral (C 2H 2)(H 2O) n ( n=1-4) clusters, in which the H 2O molecules prefer to form the CH…O and OH…C H-bonds. For the H +(C 2H 2)(H 2O) n cationic clusters, the first solvation shell consists of one ring structure with two OH… π H-bonds and three water molecules, which is completed at n=4. Simulated infrared spectra reveal that vibrational frequencies of OH… π H-bonded O-H stretching afford a sensitive probe for exploring the solvation of acetylene by protonated water molecules. Infrared spectra of the H +(C 2H 2)(H 2O) n( n=1-5) clusters could be readily measured by the infrared photodissociation technique and thus provide useful information for the understanding of solvation processes. 相似文献
3.
The effect of an external electric field on water clusters of the (H 2O) n type, with [1 n 15], in the ground state was analyzed at the B3LYP/cc-pVTZ level of theory. The calculations showed that an external electric field changes the number of hydrogen bonds, reduces the cluster sizes and increases the strength of the inter-cluster hydrogen bonds. The particular symmetry of the cluster and the null dipole moment in these specific configurations suggest that their stability can be associated with a perfect alignment of the water molecules, maximizing attractive electrostatic interactions caused by changes in the charge distribution of the clusters. 相似文献
4.
For the treatment of hydrogen bonding in SINDO1, 2 p orbitals are introduced on hydrogen. The optimization of the orbital exponent together with the generation of approximate formulas for the core attraction integrals is sufficient to obtain good geometries and binding energies in hydrogen bonded systems. The method is applied to the dimers (H 2O) 2, (NH 3) 2, (HF) 2, (HCOOH) 2, (HCN) 2, (H 2S) 2, and (HCI) 2, mixed dimers NH 3 · H 2O and H 2O · HCN, and cyclic polymers (HF) n( n = 3, 4, 6). © 1993 John Wiley & Sons, Inc. 相似文献
5.
Four compounds [Dy(H 2bidc)(Hbidc)(H 2O) 8] · 8H 2O ( 1 ), {[Dy(Hbidc)(H 2O) 2(Htzac)] · 3H 2O} n ( 2 ), [Dy(C 2O 4) 0.5(Hbidc)(H 2O) 3] n ( 3 ), {[Dy 2(Hbidc) 2(H 2O)(SO 4)] · H 2O} n ( 4 ) (H 3bidc = 1 H‐benzimidazole‐5,6‐dicarboxylic acid, H 2tzac = 1 H‐3‐amino‐5‐carboxy‐1,2,4‐triazole) were synthesized with hydrothermal synthesis and structurally characterized by elemental analysis, IR spectroscopy, and single‐crystal X‐ray diffraction. X‐ray analysis revealed that the four coordination compounds have different structures: Compound 1 is a three dimensional supermolecular structure joined by hydrogen bonding interactions based upon dinuclear units. Compound 2 is a three dimensional supermolecular structure combined by hydrogen‐bonding interactions based upon one dimensional coordination chain including a T4(1)‐type water cluster chain. The structure of compound 3 is built of two dimensional (3,6)‐connected kgd‐type (4 3) 2(4 6.6 6.8 3) layers with a right‐handed and a left‐handed helical chain, which are further extended into three dimensional supramolecular architecture by hydrogen bonding interactions. Compound 4 displays a three dimensional framework containing a dinuclear dysprosium building unit with a (3,8)‐connected (4.5 2) 2(4 2.5 10.6 12.7.8 3) topological framework. In addition, the photoluminescent property of compound 3 was investigated. 相似文献
6.
Quantum chemical computations using both density functional theory (B3LYP functional) and wavefunction (MP2 and CCSD(T)) methods, with the 6-311++G(3df,2p) and aug-cc-pV nZ ( n = D,T,Q) basis sets, in conjunction with a polarizable continuum model (PCM) method for treating structures in solution, were carried out to look again at a series of small negatively charged water species [(H 2O) n] •–. For each size n of [(H 2O) n] •– in aqueous solution with n = 2, 3, and 4, two distinct structural motifs can be identified: a classical water radical anion formed by hydrogen bonds and a molecular pincer in which the excess electron is directly interacting with H atoms. In aqueous solution, both motifs have comparable energy content and likely coexist and compete for the ground state. Some water anion isomers can dissociate when interaction with a water molecule, [(H 2O) n] •– + H 2O → H •(H 2O) m + OH –(H 2O) n–m, through successive hydrogen transfers with moderate energy barriers. This reaction can also be regarded as a water-splitting process in which the H transfers involved take place mainly within a water trimer, whereas other water molecules tend to stabilize transition structures through microsolvation rather than direct participation. Calculated absolute rate constants for the reversed reaction H •(H 2O) 2 + OH –(H 2O) 2 → [(H 2O) 4] •־ + H 2O with both H and D isotopes agree well with the experimentally evaluated counterpart and lend a kinetic support for the involvement of a tetramer unit. 相似文献
7.
The metal complexes [Cu(NO 3) 2(H 2O) 2(H 2azbpz) 2] · 2H 2O ( 1 ) and [Ni(H 2O) 4(H 2azbpz) 2](NO 3) 2 · 2H 2O ( 2 ) of 4,4′‐azobis(3,5‐dimethyl‐1H‐pyrazole) (H 2azbpz) incorporate the bipyrazole as a monodentate ligand and are associated into supramolecular architectures by hydrogen bonds and azo‐pz π interactions in the solid state. In 1 a cis configuration is integrated and the NH function adjacent to the metal‐coordinating nitrogen atom gives rise to a seven‐membered anion‐assisted hydrogen‐bonded ring around the central metal atom bringing the NH function in endo‐position to the azo‐bridge. The interplay of hydrogen‐bonds and dimeric azo‐pz π interactions in 1 forms one‐dimensional supramolecular chains, which are further interconnected by a heterodromic D2h symmetric tetrameric water ring. In 2 a trans form of H 2azbpz is mono‐coordinated and the synergy of hydrogen‐bonded rings around the central metal atom and continuous azo‐pz π interactions form a two‐dimensional supramolecular network structure. The supramolecular packings of 1 and 2 is further underpinned by the analysis of their Hirshfeld surface areas. 相似文献
8.
Summary Mixed ligand diglycinatocopper(II) complexes of the Cu(glygly)L· nH 2O type, where glygly stands for [NH 2-CH 2 CONCH 2CO 2] 2– and L for imidazole ( n = 1.5), N-methylimidazole ( n = 1), 2-methylimidazole ( n = 2), 4-methylimidazole ( n = 2), 4-phenylimidazole ( n = 2), N-acetylhistamine ( n = 2) and NH 3 ( n = 2), were prepared and characterized by elemental analyses, i.r., vis. and e.p.r. spectroscopic measurements. The molecular structure of [Cu(glygly)(achmH)]·2H 2O (achmH = acetylhistamine) was determined using three dimensional XRD data. The structure consists of distorted square planar [Cu(glygly)-(achmH)] units interconnected via the peptide oxygen at the apex to complete a square pyramidal structure, Cu—O-(peptide) 2.477(2) Å. The H 2O molecules, not binding directly to the copper ion, involve in intermolecular hydrogen bonding with the copper units. The dianionic glygly ligand and the imidazole ring bind strongly to the central copper ion with Cu—N(amino) 2.045(6) Å, Cu—N-(peptide) 1.891(5) Å, Cu—O(carboxylate) 2.001(4) Å and Cu—N(imidazole) 1.956(5) Å. The dihedral angle between the imidazole nucleus and the CuN 3O xy plane is 6.0°. Similar structures with a CuN 3O coordination plane are proposed for the imidazole complexes, based on spectroscopic data. The bonding properties of the glygly ligand and the unidentate imidazole ligands are elucidated and discussed with reference to the electronic structures of the complexes deduced from Gaussian analyses. 相似文献
9.
The solvothermal reaction of Zn(OAc) 2·2H 2O with 3,3′‐(diazenediyl)dibenzoic acid (H 2ADB) in H 2O at 393 K afforded the title complex, [Zn(C 14H 8N 2O 4)(H 2O)] n. The asymmetric unit contains half a Zn II cation, half an ADB ligand and half a water molecule. Each Zn II centre lies on a crystallographic twofold rotation axis and is five‐coordinated by four O atoms of bridging carboxylate groups from four ADB ligands and one O atom from a water molecule, forming a distorted trigonal–bipyramidal coordination geometry. The [Zn(H 2O)] subunits are bridged by carboxylate groups to give one‐dimensional [Zn(μ‐COO) 4(H 2O)] n chains. The chains are linked by ADB ligands into two‐dimensional sheets, and these sheets are further connected to neighbouring sheets via hydrogen bonds (O W—H W...O), forming a three‐dimensional hydrogen‐bond‐stabilized structure with an unprecedented 3 74 175 26 2 topology. 相似文献
10.
The effect of organic modifier concentration on retention and selectivity of two piperazine diastereomers in a typical n-octadecyl-bonded silica (ODS) column was investigated at pH 6.4 and pH 3.0 using phosphate-buffered acetonitrile (MeCN/H 2O) and methanol (MeOH/H 2O) mobile phases. The results show the logarithmic retention factors decrease with increasing organic concentration in a less rectilinear fashion in the MeCN/H 2O system than in the MeOH/H 2O system at high organic concentrations at both pHs. At pH 6.4, the MeOH/H 2O system provided significantly higher diastereomer selectivity than the MeCN/H 2O system, which can be ascribed to the hydrogen bonding interaction of methanol (as a hydrogen donor) with the piperazine amine moiety of the solute (as a hydrogen acceptor). At pH 3.0, both mobile phases provided high selectivity, in which both acetonitrile and methanol acted as hydrogen acceptors, while the protonated amine acted as the hydrogen donor. The effect of temperature on retention and selectivity was also studied in the two mobile phase systems at both pHs. It was found that at pH 6.4 the retention and selectivity were enthalpically driven in the MeOH/H 2O system, while entropically driven in the MeCN/H 2O system. However, the retention was entropically driven and the selectivity enthalpically driven in both systems at pH 3.0. Locally preferential solvating and hydrogen bonding effects are proposed to explain the anomalous retention and selectivity behaviors. 相似文献
11.
l‐Alanyl‐glutamine dipeptide assembles with Cu II ions to give the 2D coordination framework [Cu 2(C 8H 13N 3O 4) 2·2H 2O] n ( 1 ) in which amino acid residues result in specific void space. In presence of 4,4′‐bipyridine, framework 1 is turned into a binuclear complex [Cu 2(C 8H 13N 3O 4) 2(H 2O) 2(C 10H 8N 2)·8H 2O] ( 2 ), which is further linked into a 2D hydrogen‐bonded layer in which amino acid residues induce a hydrogen‐bonded water cluster containing eight water molecules in the void space. 相似文献
12.
4‐Hydroxypyridine‐2,6‐dicarboxylic acid (chelidamic acid, hypydc [H]H 2) reacts with MnCl 2·2H 2O in the presence of piperazine in water to afford the title complex, {[Mn 3(C 7H 2NO 5) 2(H 2O) 8]·3H 2O} n or {[Mn 3(hypydc) 2(H 2O) 8]·3H 2O} n. This compound is a one‐dimensional coordination polymer, with the twofold symmetric repeat unit containing three metal centres. Two different coordination geometries are observed for the two independent Mn II metal centres, viz. a distorted pentagonal bipyramid and a distorted octahedron. The 4‐oxidopyridine‐2,6‐dicarboxylate anions and two of the water molecules act as bridging ligands. The zigzag‐like geometry of the coordination polymer is stabilized by hydrogen bonds. O—H...O and C—H...O hydrogen bonds and water clusters consolidate the three‐dimensional network structure. 相似文献
13.
5-(3,4-Dicarboxylphenyl) picolinic acid (H3dppa) was applied as a new building block for the synthesis of two isomorphic coordination polymers, namely [Ni1.5dppa(H2O)3]n·nH2O (1), [Co1.5dppa(H2O)3]n·nH2O (2). Two compounds were generated by a hydrothermal self-assembly method using the corresponding metal(II) acetates and H3cppa ligand. Structure analysis reveals that compounds 1 and 2 are isomorphic both featuring a two-dimensional wave structure and are finally extended into the three-dimensional supramolecular architecture though hydrogen bonding interactions. Magnetic susceptibility measurements indicate that domain a weak ferromagnetic exchange coupling between the adjacent Ni(II) centers in 1, and a weak antiferromagnetic coupling between Co(II) ions in for 2. 相似文献
14.
The title complex, {[Fe(C 4H 4O 4)(H 2O) 4]} n, is an infinite polymeric compound bridged by the succinate dianion. Two carboxylate groups coordinate in a monodentate manner to the Fe II atom, in a trans fashion, with an O—Fe—O bond angle of 175.72 (6)° and Fe—O distances of 2.0886 (14) and 2.1008 (15) Å. One of the uncoordinated carboxylate O atom forms an intramolecular hydrogen bond with a coordinated water molecule. Extensive hydrogen bonding between parallel polymeric complex chains results in a three‐dimensional supramolecular structure. 相似文献
15.
A dinuclear copper(II) compound, [Cu(btssb)(H 2O)] 2 · 4(H 2O) ( 1), and a 1-D chain copper(II) compound, [Cu(ctssb)(H 2O)] n ( 2) [where H 2btssb is 2-[(5-bromo-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid and H 2ctssb is 2-[(3,5-dichloro-2-hydroxy-benzylidene)-amino]-ethanesulfonic acid], were prepared and characterized. Compound 1 crystallizes in the monoclinic space group P2 1/ c, with a = 10.109(2) Å, b = 20.473(4) Å, c = 6.803(1) Å, β = 100.32(3)°, V = 1385.1(5) Å 3, and Z = 2; R 1 for 1796 observed reflections [ I > 2 σ( I)] was 0.0357. The geometry around each copper(II) can be described as slightly distorted square pyramidal. The Cu II ··· Cu II distance is 5.471(1) Å. Compound 1 formed a 1-D network through O–H ··· O hydrogen bonds and 1-D water chains exist. The 1-D chain complex 2 crystallizes in the triclinic space group P 1, with a = 5.030(2) Å, b = 7.725(2) Å, c = 17.011(5) Å, α = 92.706(4)°, β = 97.131(4)°, γ = 102.452(3)°, V = 638.6(3) Å 3, and Z = 2; R 1 for 1897 observed reflections [ I > 2 σ( I)] was 0.0171. In 2, Cu(II) was also a slightly distorted square pyramid formed by two oxygens and one nitrogen from ctssb, one oxygen from another ctssb, and one water molecule. The complex formed a 1-D chain through O–S–O bridge of ctssb ligand. The 1-D chain further constructed a double chain through O?H ··· O hydrogen bonds. 相似文献
16.
The influence of temperature ( T 298-623 K) at constant pressure ( P 200 bar) on the structure of aqueous solutions LiBr: nH 2O ( n = 15, 8, 4) was studied using the method of integral equations. In the less concentrated solutions, heating results in disappearance of the tetrahedral ordering of solvent molecules; in the more concentrated soltion, this ordering is lacking even at 298 K. In the systems LiBr:15H 2O and LiBr:8H 2O, with heating, the hydrogen bonding and the coordinating power of the cation get considerably weakened, the amount of contact ion pairs grows, and the amount of hydration-separated ion pairs decreases. On heating, the H bonds between the anion and water molecules of its first coordination sphere are largely ruptured. At the same time, the structuring of the LiBr:4H 2O solution under extreme conditions has certain specific features: with increasing temperature, the intermolecular hydrogen bonding becomes stronger, and the amount of hydration-separated ion pairs increases. 相似文献
17.
Gas phase reaction between germane GeH 4 and water H 2O was investigated at CCSD(T)/[aug-cc-pVTZ-pp for Ge + Lanl2dz for H and O]//MP2/6-31G(d,p) level. Only the hydrogen elimination
channels are monitored. Within the energy range of 100 kcal/mol, we located nine equilibrium and six transition states on
the potential energy surface (PES) of the Ge–O–H systems. GeH 4 reacts with H 2O exothermically (by 2.37 kcal/mol) without a barrier to form a non-planar complex GeH 4·H 2O which isomerizes to GeH 3OH·H 2 and H 2GeOH 2·H 2 with a barrier of 44.34 kcal/mol and 53.75 kcal/mol respectively. The first step of hydrogen elimination gives two non-planar
species, GeH 3OH and H 2GeOH 2 but germinol GeH 3OH is found to be more stable. Further thermal decomposition reactions of GeH 3OH involving hydrogen elimination have been studied extensively using the same method. The final hydrogen elimination step
gives HGeOH which can exist in cis and trans forms. As the trans form is more stable, only the trans form is considered on the potential energy surface (PES) of the reaction. The important thermochemical parameters (∆ rE tot + ZPE), ∆ rH and ∆ rG for the H 2 elimination pathways are predicted accurately. 相似文献
18.
Density functional B3LYP method with 6-31++G** basis set is applied to optimize the geometries of the luteolin, water and luteolin–(H 2O) n complexes. The vibrational frequencies are also studied at the same level to analyze these complexes. We obtained four steady luteolin–H 2O, nine steady luteolin–(H 2O) 2 and ten steady luteolin–(H 2O) 3, respectively. Theories of atoms in molecules (AIM) and natural bond orbital (NBO) are used to investigate the hydrogen bonds involved in all the systems. The interaction energies of all the complexes corrected by basis set superposition error, are within −13.7 to −82.5 kJ/mol. The strong hydrogen bonding mainly contribute to the interaction energies, Natural bond orbital analysis is performed to reveal the origin of the interaction. All calculations also indicate that there are strong hydrogen bonding interactions in luteolin–(H 2O) n complexes. The OH stretching modes of complexes are red-shifted relative to those of the monomer. 相似文献
19.
Reactions of phenol and hydroxyl radical were studied under the aqueous environment to investigate the antioxidant characters of phenolic compounds. M06‐2X/6‐311 + G(d,p) calculations were carried out, where proton transfers via water molecules were examined carefully. Stepwise paths from phenol + OH • + (H 2O) n ( n = 3, 7, and 12) to the phenoxyl radical (Ph O •) via dihydroxycyclohexadienyl radicals ( ipso, ortho, meta, and para OH‐adducts) were obtained. In those paths, the water dimer was computed to participate in the bond interchange along hydrogen bonds. The concerted path corresponding to the hydrogen atom transfer (HAT, apparently Ph OH + OH • → Ph O • + H 2O) was found. In the path, the hydroxyl radical located on the ipso carbon undergoes the charge transfer to prompt the proton (not hydrogen) transfer. While the present new mechanism is similar to the sequential proton loss electron transfer (SPLET) one, the former is of the concerted character. Tautomerization reactions of ortho or para (OH)C 6H 5=O + (H 2O) n → C 6H 4(OH) 2(H 2O) n were traced with n = 2, 3, 4, and 14. The n = 3 (and n = 14) model of ortho and para was calculated to be most likely by the strain‐less hydrogen‐bond circuit. 相似文献
20.
Three coordination complexes, namely, [Zn(btbp)(3‐npa)] n ( 1 ), [Co(btbh)(3‐npa)] n ( 2 ), and {[Co(btbb)(5‐nipa)(H 2O)] · H 2O} n ( 3 ) (btbp = 1,3‐bis(thiabendazole)propane, btbh = 1,6‐bis(thiabendazole)hexane, btbb = 1,4‐bis(thiabendazole)butane, 3‐H 2npa = 3‐nitrophthalic acid and 5‐H 2nipa = 5‐nitroisophthalic acid) were synthesized under hydrothermal conditions and characterized by physicochemical and spectroscopic methods as well as by single‐crystal X‐ray diffraction. Complex 1 features a fascinating meso‐helical chain, which is further extended into a 2D supramolecular framework involving π ··· π stacking interactions. Complexes 2 and 3 show dinuclear structures. Complex 2 is further connected through C–H ··· O hydrogen bonding interactions to afford a 2D supramolecular layer, whereas complex 3 is further extended to a rare 2‐nodal (3,4)‐connected supramolecular sheet with a point symbol of {3.4 2.5.6.7} 2{3.8 2} by O–H ··· O hydrogen bonding interactions. The electrochemical behaviors of the two cobalt complexes 2 and 3 were reported. Moreover, the luminescent properties for 1 and the photocatalytic properties for the complexes were investigated. 相似文献
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