N,N''''-(2-苯并咪唑基甲基)亚氨基甲基膦酸的双核镍化合物Ni2(bbimp)2(4,4''''-bipy)(H2O)2·2H2O和Ni2(bbimp)2(H2O)2][Ni(bbimp)(H2O)2]2·4H2O的晶体结构和磁学性质

该文报道了N,N′-(2-苯并咪唑基甲基)亚氨基甲基膦酸{bbimpH_2,[(C7H5N2)CH2]2NCH2PO3H2}的2个镍化合物Ni2(bbimp)2(4,4′-bipy)(H2O)2·2H2O(1)和[Ni2(bbimp)2(H2O)2][Ni(bbimp)(H2O)2]2·4H2O(2)。化合物1是4,4′-联吡啶作为桥连配体的中性双核结构。化合物2含有1个中性的[Ni2(bbimp)2(H2O)2]双核分子与2个中性的[Ni(bbimp)(H2O)2]单核分子。双核分子单元中的2个Ni!离子被2个膦酸氧桥连。在化合物2中,膦酸氧桥连的2个Ni!离子之间存在铁磁性相互作用。     

电催化合成过氧化氢用于环境消毒

流行性疾病贯穿整个人类历史,伴随全球人口流动,它们可能演变成大型流行病.时至今日,我们仍在见证已知和新生的病原体对人类历史格局的改变.在与流行性疾病的抗争中,诸如紫外线辐射、巴氏杀菌和化学氧化法等技术被用于病原体的消杀和抗体的研制.然而,这些技术在环境消毒方面存在诸多不利,譬如过长的消杀时间、昂贵的特殊设备以及伴生的环境污染.过氧化氢是一种环境友好的多功能氧化剂,其分解的最终产物是氧气和水,广泛用于伤口消毒、纸浆和纺织品漂白、废水废气处理、化学合成、半导体清洗以及洗涤剂.目前,过氧化氢的生产严重依赖于传统的蒽醌法,该技术由Riedl和Pfleiderer于1939年提出,并沿用至今.然而,蒽醌法能耗高,该技术仅在较大规模上经济可行.不稳定的过氧化氢溶液存在危险性,这对大宗过氧化氢的运输和存储提出了额外的挑战.电化学合成过氧化氢被认为可有效替代传统蒽醌法,其反应条件温和,所需反应物是环境中广泛存在的水和氧气;与可再生能源相结合,有望实现分布式原位生产过氧化氢.过氧化氢既可以通过两电子的水氧化反应生成,又可以经由两电子的氧还原反应产生.Berl等在上世纪30年代首次报道了经由两电子的氧还原反应合成过氧化氢,并随后在1991年将其商业化(亦即Huron-Dow法).自此,Huron-Dow法被广泛用于纸浆和纸张的漂白过程.最近,Huron-Dow法进一步演变为电子-芬顿工艺,并被广泛用于饮用水净化和污水处理.目前,涉及高活性和高选择性的电化学合成过氧化氢的优秀综述见诸各大期刊;但是鲜有综述探讨该技术在环境消毒方面的应用.为了探寻提升公共卫生安全的有效替代方法,本文探讨了在电催化制备过氧化氢在环境消毒方面的可行性.本文涵盖三个主题,从基础理论到实践两个层次探讨了该技术在实际应用中的可行性.首先,回顾了H2O2消杀病原体的机理;其次,讨论了影响电催化制备过氧化氢的关键因素,并对现有的用于两电子水氧化和氧还原的催化剂进行了系统性的评述;最后,讨论了电极和电解池的合理设计,以实现电催化制备过氧化氢在实际中的应用.本文试图为最终实现电催化制备过氧化氢在环境消毒,尤其是公共卫生领域,提供可寻的研究方向.     

A family of new glutarate compounds: synthesis, crystal structures of: Co(H2O)5L(1), Na2[CoL2] (2), Na2[L(H2L)4/2] (3), {[Co3(H2O)6L2](HL)2}.4H2O (4), {[Co3(H2O)6L2](HL)2}.10H2O (5), {[Co3(H2O)6L2]L2/2}.4H2O (6), and Na2{[Co3(H2O)2]L8/2].6H2O (7), and magnetic properties of 1 and 2 with H2L = HOOC-(CH2)3-COOH

Seven new glutaric acid complexes, Co(H 2O) 5L 1, Na 2[CoL 2] 2, Na 2[L(H 2L) 4/2] 3, {[Co 3(H 2O) 6L 2](HL) 2}.4H 2O 4, {[Co 3(H 2O) 6L 2](HL) 2}.10H 2O 5, {[Co 3(H 2O) 6L 2]L 2/2}.4H 2O 6, and Na 2{[Co 3(H 2O) 2]L 8/2].6H 2O 7 were obtained and characterized by single-crystal X-ray diffraction methods along with elemental analyses, IR spectroscopic and magnetic measurements (for 1 and 2). The [Co(H 2O) 5L] complex molecules in 1 are assembled into a three-dimensional supramolecular architecture based on intermolecular hydrogen bonds. Compound 2 consists of the Na (+) cations and the necklace-like glutarato doubly bridged [ C o L 4 / 2 ] 2 - infinity 1 anionic chains, and 3 is composed of the Na (+) cations and the anionic hydrogen bonded ladder-like [ L ( H 2 L ) 4 / 2 ] 2 - infinity 1 anionic chains. The trinuclear {[Co 3(H 2O) 6L 2](HL) 2} complex molecules with edge-shared linear trioctahedral [Co 3(H 2O) 6L 2] (2+) cluster cores in 4 and 5 are hydrogen bonded into two-dimensional (2D) networks. The edge-shared linear trioctahedral [Co 3(H 2O) 6L 2] (2+) cluster cores in 6 are bridged by glutarato ligands to generate one-dimensional (1D) chains, which are then assembled via interchain hydrogen bonds into 2D supramolecular networks. The corner-shared linear [Co 3O 16] trioctahedra in 7 are quaternate bridged by glutarato ligands to form 1D band-like anionic {[Co 3(H 2O) 2]L 8/2} (2+) chains, which are assembled via interchain hydrogen bonds into 2D layers, and between them are sandwiched the Na (+) cations. The magnetic behaviors of 1 and 2 obey the Curie-Weiss law with chi m = C/( T - Theta) with the Curie constant C = 3.012(8) cm (3) x mol (-1) x K and the Weiss constant Theta = -9.4(7) K for 1, as well as C = 2.40(1) cm (3) x mol (-1) x K and Theta = -2.10(5) K for 2, indicating weak antiferromagnetic interactions between the Co(II) ions.     

H_2O_2氧化N_2生成N_2O和H_2O机理的研究

采用量子化学计算方法研究了Ｈ２Ｏ２ 氧化Ｎ２ 生成Ｎ２Ｏ 和Ｈ２Ｏ 的机理．结果发现, Ｈ２Ｏ２ 氧化Ｎ２ 先通过１ 个四元环过渡态形成中间体Ｈ２Ｎ２Ｏ２ 分子,Ｈ２Ｎ２Ｏ２ 再通过一个五元环过渡态形成Ｎ２Ｏ和Ｈ２Ｏ．根据计算得到的每步反应的活化能,得知Ｈ２Ｏ２ 氧化Ｎ２ 生成中间体Ｈ２Ｎ２Ｏ２ 分子是整个反应的控制步骤．     

Vibrational energy transfer and relaxation in O2 and H2O

Near-resonant vibrational energy exchange between oxygen and water molecules is an important process in the Earth's atmosphere, combustion chemistry, and the chemical oxygen iodine laser (COIL). The reactions in question are (1) O2(1) + O2(0) --> O2(0) + O2(0); (2) O2(1) + H2O(000) --> O2(0) + H2O(000); (3) O2(1) + H2O(000) <--> O2(0) + H2O(010); (4) H2O(010) + H2O(000) --> H2O(000) + H2O(000); and (5) H2O(010) + O2(0) --> H2O(000) + O2(0). Reanalysis of the data available in the chemical kinetics literature provides reliable values for rate coefficients for reactions 1 and 4 and strong evidence that reactions 2 and 5 are slow in comparison with reaction 3. Analytical solution of the chemical rate equations shows that previous attempts to measure the rate of reaction 3 are unreliable unless the water mole fraction is higher than 1%. Reanalysis of data from the only experiment satisfying this constraint provides a rate coefficient of (5.5 +/- 0.4) x 10(-13) cm3/s at room temperature, between the values favored by the atmospheric and laser modeling communities.     

硫化合物与H2O2在非催化反应中的非线性行为

硫化学反应中的非线性是近年来非线性化学研究的热点之一，我们注意到CU（11催化剂存在时H202氧化KSCN山、N。。S。0开］出现振荡或复杂振荡现象，但这两个反应的机理研究尚处在不成熟或模糊阶段＊‘1，由于K盯N、＊。。a0。和优（＊H小氧化过程有多种价态的变化，Cu（11）催化     

Photodetachment and photofragmentation pathways in the [(CO2)2(H2O)m]- cluster anions

The mass-selected [(CO(2))(2)(H(2)O)(m)](-) cluster anions are studied using a combination of photoelectron imaging and photofragment mass spectroscopy at 355 nm. Photoelectron imaging studies are carried out on the mass-selected parent cluster anions in the m=2-6 size range; photofragmentation results are presented for m=3-11. While the photoelectron images suggest possible coexistence of the CO(2) (-)(H(2)O)(m)CO(2) and (O(2)CCO(2))(-)(H(2)O)(m) parent cluster structures, particularly for m=2 and 3, only the CO(2) (-) based clusters are both required and sufficient to explain all fragmentation pathways for m>/=3. Three types of anionic photofragments are observed: CO(2) (-)(H(2)O)(k), O(-)(H(2)O)(k), and CO(3) (-)(H(2)O)(k), k6) is attributed to hindrance from the H(2)O molecules.     

Reactions of hydrated electrons (H2O)n- with carbon dioxide and molecular oxygen: hydration of the CO2- and O2- ions

The gas-phase reactions of hydrated electrons with carbon dioxide and molecular oxygen were studied by Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. Both CO2 and O2 react efficiently with (H2O)n- because they possess low-lying empty pi* orbitals. The molecular CO2- and O2- anions are concurrently solvated and stabilized by the water ligands to form CO2(-)(H2O)n and O2(-)(H2O)n. Core exchange reactions are also observed, in which CO2(-)(H2O)n is transformed into O2(-)(H2O)n upon collision with O2. This is in agreement with the prediction based on density functional theory calculations that O2(-)(H2O)n clusters are thermodynamically favored with respect to CO2(-)(H2O)n. Electron detachment from the product species is only observed for CO2(-)(H2O)2, in agreement with the calculated electron affinities and solvation energies.     

Synthesis and catalytic epoxidation activity with TBHP and H2O2 of dioxo-, oxoperoxo-, and oxodiperoxo molybdenum(VI) and tungsten(VI) compounds containing monodentate or bidentate phosphine oxide ligands: crystal structures of WCl2(O)2(OPMePh2)2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2.C4H10O, WCl2(O)2dppmO2, Mo(O)(O2)2dppmO2, and W(O)(O2)2dppmO2

The dioxo tungsten(VI) and molybdenum(VI) complexes WCl2(O)2(OPMePh2)2, WCl2(O)2dppmO2, and MoCl2(O)2dppmO2, the oxoperoxo compounds WCl2(O)(O2)(OPMePh2)2, WCl2(O)(O2)dppmO2, and MoCl2(O)(O2)dppmO2, and the oxodiperoxo complexes, W(O)(O2)2dppmO2 and Mo(O)(O2)2dppmO2 have been prepared and characterized by IR spectroscopy, 31P NMR spectroscopy, elemental analysis, and X-ray crystallography. The structural and X-ray crystallographic data of compounds WCl2(O)2(OPMePh2)2, WCl2(O)(O2)(OPMePh2)2, MoCl2(O)2dppmO2.4H10O, WCl2(O)2dppmO2, Mo(O)(O2)2dppmO2, and W(O)(O2)2dppmO2 are also detailed. All complexes were studied as catalysts for cis-cyclooctene epoxidation in the presence of tert-butyl hydroperoxide (TBHP) or H2O2 as an oxidant. The Mo-based catalysts showed a superior reactivity over W-based catalysts in the TBHP system. On the other hand, in the H2O2 system, the W-based catalysts (accomplishing nearly 100% epoxidation of cyclooctene in 6 h) are more reactive than the Mo catalysts (<45% under some conditions). Various solvent systems have been investigated, and ethanol is the most suitable solvent for the H2O2 system.     

H2O2-Na2S2O3反应对pH和反应物起始浓度比的依赖性

在H2O2-Na2S2O3反应体系中，pH值和[H2O2]0/[Na2S2O3]0对反应产物的浓度大小起着关键作用.本文通过考察这两种因素对反应产物的影响，以及对反应机理的模拟，得出了pH值和氧化剂与还原剂浓度比影响反应产物浓度的一般规律.结果表明：pH< 3时，反应主要生成单质硫， 3< pH< 6时， 较为稳定，提高pH和[H2O2]0/[Na2S2O3]0有利于SO42-生成，在中性或弱碱性溶液中S(Ⅳ)(HSO42-或SO32-)物质浓度出现峰值.     

Hydrogen NMR of H2-TDF-D2O clathrate

The three-component clathrate H2-TDF-D2O offers hydrogen storage at lower pressure, but with reduced weight fraction of H2, compared to H2-H2O clathrate. In H2-TDF-D2O, H2 resides exclusively and singly in the small cages of structure II, allowing the rotational behavior of H2 in this nominally uniform environment to be probed. Here we report NMR measurements of the H2 line shape and relaxation times T1, T2, and T1rho. The principal differences in the results, compared to the H2-D2O binary system, are the dips in T2 and T1rho near 28 K due to thermally activated reorientation of TDF molecules, line-narrowing and decreases in T2 and T1rho near 175 K due to D2O reorientations and diffusion, and the apparent absence of H2 diffusion between small cages.     

Single fluorescent probe responds to H2O2, NO, and H2O2/NO with three different sets of fluorescence signals

Hydrogen peroxide (H(2)O(2)) acts as a signaling molecule in a wide variety of signaling transduction processes and an oxidative stress marker in aging and disease. However, excessive H(2)O(2) production is implicated with various diseases. Nitric oxide (NO) serves as a secondary messenger inducing vascular smooth muscle relaxation. However, mis-regulation of NO production is associated with various disorders. To disentangle the complicated inter-relationship between H(2)O(2) and NO in the signal transduction and oxidative pathways, fluorescent reporters that are able to display distinct signals to H(2)O(2), NO, and H(2)O(2)/NO are highly valuable. Herein, we present the rational design, synthesis, spectral properties, and living cell imaging studies of FP-H(2)O(2)-NO, the first single-fluorescent molecule, that can respond to H(2)O(2), NO, and H(2)O(2)/NO with three different sets of fluorescence signals. FP-H(2)O(2)-NO senses H(2)O(2), NO, and H(2)O(2)/NO with a fluorescence signal pattern of blue-black-black, black-black-red, and black-red-red, respectively. Significantly, we have further demonstrated that FP-H(2)O(2)-NO, a single fluorescent probe, is capable of simultaneously monitoring endogenously produced NO and H(2)O(2) in living macrophage cells in multicolor imaging. We envision that FP-H(2)O(2)-NO will be a unique molecular tool to investigate the interplaying roles of H(2)O(2) and NO in the complex interaction networks of the signal transduction and oxidative pathways. In addition, this work establishes a robust strategy for monitoring the multiple ROS and RNS species (H(2)O(2), NO, and H(2)O(2)/NO) using a single fluorescent probe, and the modularity of the strategy may allow it to be extended for other types of biomolecules.     

Synthesis and characterization of the open-framework barium bisphosphonate [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O

Following the strategy of using polyfunctional phosphonic acids for the synthesis of open-framework metal phosphonates, the phosphonocarboxylic acid (H2O3PCH2)2NCH2C6H4COOH was used in the hydrothermal synthesis of new Ba phosphonates. Its decomposition led to the first open-framework barium phosphonate [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O. The synthesis was also successfully performed using iminobis(methylphosphonic acid), (H2O3PCH2)2NH, as a starting material, and the synthesis was optimized to obtain as a pure material. The reaction setup as well as the pH are the dominant parameters, and only a diffusion-controlled reaction led to the desired compound. The crystal structure was solved from single-crystal data: monoclinic; C2/c; a=2328.7(2), b=1359.95(7), and c=718.62(6) pm; beta=98.732(10) degrees ; V=2249.5(3)x10(6) pm3; Z=4; R1=0.036; and wR2=0.072 (all data). The structure of [Ba3(O3PCH2NH2CH2PO3)2(H2O)4].3H2O is built up from BaO8 and BaO10 polyhedra forming BaO chains and layers, respectively. These are connected to a three-dimensional metal-oxygen-metal framework with the iminobis(methylphosphonic acid) formally coating the inner walls of the pores. The one-dimensional pores (3.6x4 A) are filled with H2O molecules that can be thermally removed. Thermogravimetric investigations and temperature-dependent X-ray powder diffraction demonstrate the stability of the crystal structure up to 240 degrees C. The uptake of N,N-dimethylformamide and H2O by dehydrated samples is demonstrated. Furthermore, IR, Raman, and 31P magic-angle-spinning NMR data are also presented.     

Femtosecond dynamics of Cu(H(2)O)(2)

The ultrafast relaxation dynamics of Cu(H(2)O)(2) is investigated using femtosecond photodetachment-photoionization spectroscopy. In addition, stationary points on the Cu(H(2)O)(2) anion, neutral, and cation potential energy surfaces are characterized by ab initio electronic structure calculations. Electron photodetachment from Cu(-)(H(2)O)(2) initiates the dynamics on the ground-state potential energy surface of neutral Cu(H(2)O)(2). The resulting Cu(H(2)O)(2) complexes experience large-amplitude H(2)O reorientation and dissociation. The time evolution of the Cu(H(2)O)(2) fragmentation products is monitored by time-resolved resonant multiphoton ionization. The parent ion, Cu(+)(H(2)O)(2), is not detected above background levels. The rise to a maximum of the Cu(+) signal from Cu(-)(H(2)O)(2), and the decay of the Cu(+)(H(2)O) signal from Cu(-)(H(2)O)(2) have similar tau approximately 10 ps time dependences to the corresponding signals from Cu(-)(H(2)O), but display clear differences at very short and long times. The experimental observations can be understood in terms of the following picture. Prompt dissociation of H(2)O from nascent Cu(H(2)O)(2) gives rise to a vibrationally excited Cu(H(2)O) complex, which dissociates to Cu+H(2)O due to coupling of H(2)O internal rotation to the dissociation coordinate. This prompt dissociation removes all intra-H(2)O vibrational excitation from the intermediate Cu(H(2)O) fragment, which quenches the long time vibrational predissociation to Cu+H(2)O previously observed in analogous experiments on Cu(-)(H(2)O).     

Monitoring dehydration and condensation processes of Na2HPO4*12H2O using thermo-Raman spectroscopy

Thermal dehydration and condensation processes of disodium hydrogen phosphate dodecahydrate (Na2HPO4*12H2O) were monitored by thermo-Raman spectroscopy (TRS). Various hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were observed, followed by condensation of Na2HPO4 to sodium pyrophosphate (Na4P2O7) in a dynamic thermal process. Representative Raman spectra of all the hydrated forms Na2HPO4*12H2O, Na2HPO4*8H2O, Na2HPO4*7H2O, Na2HPO4*2H2O, Na2HPO4*H2O and Na2HPO4 were detected in both H2O and PO4(3- )regions are reported. The thermo-Raman intensity (TRI) thermogram also showed systematic loss of water in five steps of dehydration, with the differential TRI thermogram in agreement shows five dips corresponding to the five steps of dehydration, respectively. Thermogravimetry (TG) and differential thermogravimetry (DTG) are in harmony with the results of TRS, though, the two could not resolve the steps involved.     

Rates and mechanisms of water exchange of UO2(2+)(aq) and UO2(oxalate)F(H2O)2-: a variable-temperature 17O and 19F NMR study

This study consists of two parts: The first part comprised an experimental determination of the kinetic parameters for the exchange of water between UO2(H2O)5(2+) and bulk water, including an ab initio study at the SCF and MP2 levels of the geometry of UO2(H2O)5(2+), UO2(H2O)4(2+), and UO2(H2O)6(2+) and the thermodynamics of their reactions with water. In the second part we made an experimental study of the rate of water exchange in uranyl complexes and investigated how this might depend on inter- and intramolecular hydrogen bond interactions. The experimental studies, made by using 17O NMR, with Tb3+ as a chemical shift reagent, gave the following kinetic parameters at 25 degrees C: kex = (1.30 +/- 0.05) x 10(6) s(-1); deltaH(not equal to) = 26.1 +/- 1.4 kJ/mol; deltaS(not equal to) = -40 +/- 5J J/(K mol). Additional mechanistic indicators were obtained from the known coordination geometry of U(VI) complexes with unidentate ligands and from the theoretical calculations. A survey of the literature shows that there are no known isolated complexes of UO2(2+) with unidentate ligands which have a coordination number larger than 5. This was corroborated by quantum chemical calculations which showed that the energy gains by binding an additional water to UO2(H2O)4(2+) and UO2(H2O)5(2+) are 29.8 and -2.4 kcal/mol, respectively. A comparison of the change in deltaU for the reactions UO2(H2O)5(2+)--> UO2(H2O)4(2+) + H2O and UO2(H2O)5(2+) + H2O --> UO2(H2O)6(2+) indicates that the thermodynamics favors the second (associative) reaction in gas phase at 0 K, while the thermodynamics of water transfer between the first and second coordination spheres, UO2(H2O)5(2+) --> UO2(H2O)4(H2O)2+ and UO2(H2O)5(H2O)2+ --> UO2(H2O)6(2+), favors the first (dissociative) reaction. The energy difference between the associative and dissociative reactions is small, and solvation has to be included in ab initio models in order to allow quantitative comparisons between experimental data and theory. Theoretical calculations of the activation energy were not possible because of the excessive computing time required. On the basis of theoretical and experimental studies, we suggest that the water exchange in UO2(H2O)5(2+) follows a dissociative interchange mechanism. The rates of exchange of water in UO2(oxalate)F(H2O)2- (and UO2(oxalate)F2(H2O)2- studied previously) are much slower than in the aqua ion, kex = 1.6 x 10(4) s(-1), an effect which we assign to hydrogen bonding involving coordinated water and fluoride. The kinetic parameters for the exchange of water in UO2(H2O)52+ and quenching of photo excited *UO2(H2O)5(2+) are very near the same, indicating similar mechanisms.     

Mass spectrometric separation and quantitation of overlapping isotopologues. H2O/HOD/D2O and H2Se/HDSe/D2Se mixtures

Three conceptually different mathematical methods are presented for accurate mass spectrometric determination of H2O/HOD/D2O and H2Se/HDSe/D2Se concentrations from mixtures. These are alternating least-squares, weighted two-band target entropy minimization, and a statistical mass balance model. The otherwise nonmeasurable mass spectra of partially deuterated isotopologues (HOD and HDSe) are mathematically constructed. Any recorded isotopologue mixture mass spectra are then deconvoluted by least-squares into their components. This approach is used to study the H2O/D2O exchange reaction, and is externally validated gravimetrically. The H2O/D2O exchange equilibrium constant is also measured from the deconvoluted 70 eV electron impact GC/MS data (K = 3.85 +/- 0.03).     

Polyoxometalate (W/Mo) compounds connected via lanthanide cations with a three-dimensional framework, H2{[K(H2O)2]2[Ln(H2O)5]2(H2M12O42)}.nH2O: synthesis, structures, and magnetic properties

A series of 10 novel polyoxometalate (W/Mo) compounds connected via a trivalent lanthanide cation bridge, H2{[K(H2O)2]2[Ln(H2O)5]2(H2M12O42)}.n(H2O) (Ln = La, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, Lu; M = W or W/Mo) (1-10), were designed and synthesized on the basis of the abduction of Al3+ in aqueous solution. X-ray diffraction analyses reveal that the structures of complexes 1-10 are three-dimensional frameworks assembled from the arrangement of H2M12O42(10-) (named paradodecmetalate-B) and Ln(H2O)53+ with two planes, which are constructed via the unification of H2M12O42(10-) and Ln(H2O)53+, along the [100] and [001] directions. Magnetic measurements reveal the paramagnetic properties and a strong ferromagnetic coupling between the two nearest-neighboring lanthanide cations, Ln3+ (Ln = Dy, Er), within the circle for compounds 2 and 4-9.     

Theoretical Modeling of Water Exchange on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)

Density functional theory is applied to modeling the exchange in aqueous solution of H(2)O on [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)]. Optimized structures for the starting molecules are reported together with trigonal bipyramidal (tbp) systems relevant to an associative mechanism. While a rigorous tbp geometry cannot by symmetry be the actual transition state, it appears that the energy differences between model tbp structures and the actual transition states are small. Ground state geometries calculated via the local density approximation (LDA) for [Pd(H(2)O)(4)](2+) and relativistically corrected LDA for the Pt complexes are in good agreement with available experimental data. Nonlocal gradient corrections to the LDA lead to relatively inferior structures. The computed structures for analogous Pd and Pt species are very similar. The equatorial M-OH(2) bonds of all the LDA-optimized tbp structures are predicted to expand by 0.25-0.30 ?, while the axial bonds change little relative to the planar precursors. This bond stretching in the transition state counteracts the decrease in partial molar volume caused by coordination of the entering water molecule and can explain qualitatively the small and closely similar volumes of activation observed. The relatively higher activation enthalpies of the Pt species can be traced to the relativistic correction of the total energies while the absolute DeltaH() values for exchange on [Pd(H(2)O)(4)](2+) and [Pt(H(2)O)(4)](2+) are reproduced using relativistically corrected LDA energies and a simple Born model for hydration. The validity of the latter is confirmed via some simple atomistic molecular mechanics estimates of the relative hydration enthalpies of [Pd(H(2)O)(4)](2+) and [Pd(H(2)O)(5)](2+). The computed DeltaH() values are 57, 92, and 103 kJ/mol compared to experimental values of 50(2), 90(2), and 100(2) kJ/mol for [Pd(H(2)O)(4)](2+), [Pt(H(2)O)(4)](2+), and trans-[PtCl(2)(H(2)O)(2)], respectively. The calculated activation enthalpy for a hypothetical dissociative water exchange at [Pd(H(2)O)(4)](2+) is 199 kJ/mol. A qualitative analysis of the modeling procedure, the relative hydration enthalpies, and the zero-point and finite temperature corrections yields an estimated uncertainty for the theoretical activation enthalpies of about 15 kJ/mol.     

Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O: a layered cadmium phosphonate with reversible dehydration/hydration properties

In a recent systematic study on the influence of the reaction temperature on the structure formation in the system CdCl2/H(HO3PCH2)2NH-CH2C6H4-COOH (H5L) /NaOH, [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O was obtained as a microcrystalline compound. We have now been able to elucidate the structure from single-crystal data: triclinic, P; a=5.4503(9), b=12.880(2), and c=16.417(3) A; alpha=67.841(6) degrees, beta=80.633(6) degrees, gamma=87.688(8) degrees, V=1052.9(3) A3; Z=1; R1=0.1143, R2=0.2108 (all data); 0.0705, 0.1823 ((I>2sigmaI)). The structure of [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O is built up of cadmium phosphonate layers connected by water-mediated hydrogen bonds between aryl-carboxylic acid groups and water molecules coordinated to Cd2+ ions of adjacent layers (C-OH...H2O...H2O-Cd2+). The title compound was characterized by IR spectroscopy and energy dispersive X-ray, elemental, and thermogravimetric analyses. Furthermore, temperature-dependent X-ray diffraction data are presented. [Cd3(H2O)3((O3PCH2)2NH-CH2C6H4-COOH)2].11H2O can be reversibly dehydrated, and mechanical stress and grinding in the presence of water leads to the intercalation of additional water molecules.