大尺寸磷酸二氢钾晶体的折射率均一性研究

采用德国Trioptics公司生产的新一代全自动高精度折射率测量仪,测量了磷酸二氢钾(KDP)晶体不同部位的样品位于近紫外到近红外波段(0.253—1.530μm)内12个不同波长处的折射率,测量精度达到10-6量级.结果表明,大尺寸KDP晶体不同部位样品的折射率存在不均一性,靠近晶体恢复区的样品折射率小于晶体锥头区的样品折射率,偏差在10-5—10-4量级.研究发现,这种折射率不均一性与晶体不同部位的结晶质量存在差异有关.另外,将测量数据与其他文献中的数据进行对比.结果显示,所测试的样品数、波段宽度、测量点数量以及数据的精度均超过其他文献,结合测试条件分析了不同文献数据存在差异的原因.最后,使用最小二乘法拟合得到了KDP晶体较为可靠的Sellmeier方程.     

Synthesis and study of organic nitrates of the heterofunctional series

The first representative of organic nitrates of the oxazoline series, 4,4-dihydroxymethyl-2-(3-pyridyl)-2-oxazoline dinitrate, was synthesized by the reaction ofN-nicotinoyltri(hydroxymethyl)aminomethane trinitrate hydronitrate (1) with a solution of KOH in alcohol. The reactivities of compound1 andN-nicotinoylethanolamine nitrate (nicorandil) in the reaction of intramolecular heterocyclization were compared. The structure of the compound synthesized has been established by X-ray diffraction analysis. For Part 1, see Ref. 1 Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 478–481, March, 1998.     

Elongated dihydrogen versus compressed dihydride complexes: the temperature dependence of the H-D spin-spin coupling constant as a criterion to distinguish between them

To be able to propose experimental tests to distinguish elongated dihydrogen transition-metal complexes from compressed dihydride transition-metal complexes, a thorough density functional study of the electronic structure in combination with quantum nuclear dynamics calculations have been performed for complexes [Cp*Ru(H2PCH2PCH2(H2)]+ and [CpRe(CO)2H2]. The results of this study suggest that elongated dihydrogen complexes and compressed dihydride complexes have different properties and that it should be possible to distinguish between them experimentally. In particular, different behavior is predicted with respect to 1) the sign of the isotope geometric effect on the H-H distance at 0 K, 2) the temperature dependence of the H-H distance, and 3) the temperature dependence of the H-D spin-spin coupling constant in 1H NMR spectroscopy.     

Effect of citrate impurities on the reference pH value of potassium dihydrogen buffer solution

Solutions of potassium dihydrogen citrate, KH₂C₆H₅O₇, exhibit reference pH values close to those of the primary standard pH buffer solutions of tartrate and phthate. Nevertheless, as opposed to all other recommended primary buffer standards, the citrate reagent is not commercially available as a standard reference material (SRM).In this work, experiments have been performed on solid reagent from different sources, which revealed the presence of the various citrate species in variable amounts. This may arise from the sensitivity of the system to the purification strategy, owing to the proximity of the acidity constants of the triprotic citric acid, H₃C₆H₅O₇.An experimental procedure has been developed which leads to a satisfactory preparation of the citrate reagent, to an extent that its solutions, independently of batch on supplier, exhibit reproducible pH values, in agreement with the conventionally assigned pH (S) = 3.776 at 25 °C for 0.05 m KH₂C₆H₅O₇.Comparison of expected and experimental values is used as a quantitative test for the quality of reagent, eventually indicating the need for purification according to recommendations.     

Transparent and anhydrous proton conductors based on PVA/imidazole/NH4H2PO4 composites

A new anhydrous proton conducting membrane for solid-state electrochromic device (ECD) based on poly(vinyl alcohol) (PVA), imidazole (Imi), and ammonium dihydrogen phosphate (NH₄H₂PO₄) was prepared. The structure of PVA/Imi/NH₄H₂PO₄ composite membrane was studied by X-ray diffraction and differential scanning calorimetry (DSC). The transmittance of the membrane always decreases with increasing content of the imidazolium. Compared with the PVA/NH₄H₂PO₄ membrane, the addition of proper amount of Imi can enhance the proton conductivity to a certain extent. At low PVA content, equal molar ratio of Imi and NH₄H₂PO₄ is favorable for high proton conductivity, while higher molar ratio of Imi and NH₄H₂PO₄ is beneficial at high PVA content.     

EPR and Raman investigations into anionic redox chemistry of nanoporous 12CaO·7Al2O3 interacting with O2, H2 and N2O

EPR and Raman spectroscopy jointed with temperature-programmed reduction (TPR) and oxidation (TPO) were used to elucidate of the anionic redox processes occurring during the interaction of dioxygen, nitrous oxide and dihydrogen with nanoporous 12CaO·7Al₂O₃. The results showed that hydrogen and oxygen enter the mayenite cages following a dissociative pathway involving hydride, hydroxyl and peroxide intermediates, respectively. Generation and annihilation of the cage O ₂ ⁻ and O⁻ radicals upon oxidative and reductive treatments, confined to the near to the surface region, were found to be reversible. The key intermediates of this process were identified and a detailed mechanism of the surface and cage reactions was proposed.     

The properties of weak and strong dihydrogen-bonded D-H...H-A complexes.

The properties of six dihydrogen-bonded (DHB) dimers with the BeH2 molecule as a proton acceptor were calculated by MP2, CCSD(T) and B3LYP methods. The structural, energetic and spectroscopic parameters are presented and analyzed in terms of their possible correlation with the interaction energy and the intermolecular H...H separation. The symmetry-adapted perturbation theory (SAPT) calculations were performed to gain more insight into the nature of the H...H interactions. The studied complexes are divided into three groups based on the calculated intermolecular distances and the interaction energies which range from approximately -1 to -42 kJ mol(-1). The analysis of the interaction energy components indicates that, in contrast to conventional hydrogen bonds, the induction energy is the most important term in the BeH2NH4+ complex. On the other hand, there is no sharp boundary between the DHB complexes classified as hydrogen bonded and van der Waals systems. The complexation-induced changes in vibrational frequencies and in proton shielding constants show a relationship with the interaction energy. The values of the 2hJXH and 3hJBeX coupling constants correlate well with the interaction energy and with the intermolecular distance.     

Ultrasound-promoted greener approach to synthesize α-hydroxy phosphonates catalyzed by potassium dihydrogen phosphate under solvent-free condition

We report a new environmentally-benign, convenient, and facile methodology for the synthesis of α-hydroxyphosphonates from an aromatic/heteroaromatic aldehyde with triethyl phosphite in the presence of potassium dihydrogen phosphate (KH₂PO₄) under ultrasound-assisted solvent-free conditions. Furthermore, a series of compounds were synthesized and characterized by melting point, EI-MS, NMR, and IR tools. Utilization of easy reaction conditions, isolation, and purification makes this manipulation very interesting from an economic perspective.     

A dihydrogen phosphate anionic network as a host lattice for cations in 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate) and 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1)

In the salt 1‐methylpiperazine‐1,4‐diium bis(dihydrogen phosphate), C₅H₁₃N₂²⁺·2H₂PO₄⁻, (I), and the solvated salt 2‐(pyridin‐2‐yl)pyridinium dihydrogen phosphate–orthophosphoric acid (1/1), C₁₀H₉N₂⁺·H₂PO₄⁻·H₃PO₄, (II), the formation of O—H...O and N—H...O hydrogen bonds between the dihydrogen phosphate (H₂PO₄⁻) anions and the cations constructs a three‐ and two‐dimensional anionic–cationic network, respectively. In (I), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional pseudo‐honeycomb‐like supramolecular architecture along the (010) plane. 1‐Methylpiperazine‐1,4‐diium cations are trapped between the (010) anionic layers through three N—H...O hydrogen bonds. In solvated salt (II), the self‐assembly of H₂PO₄⁻ anions forms a two‐dimensional supramolecular architecture with open channels projecting along the [001] direction. The 2‐(pyridin‐2‐yl)pyridinium cations are trapped between the open channels by N—H...O and C—H...O hydrogen bonds. From a study of previously reported structures, dihydrogen phosphate anions show a supramolecular flexibility depending on the nature of the cations. The dihydrogen phosphate anion may be suitable for the design of the host lattice for host–guest supramolecular systems.     

A new unconventional halogen bond C?X···H?M between HCCX (X = Cl and Br) and HMH (M = Be and Mg): An ab initio study

In this article, a new type of halogen‐bonded complex YCCX···HMY (X = Cl, Br; M = Be, Mg; Y = H, F, CH₃) has been predicted and characterized at the MP2/aug‐cc‐pVTZ level. We named it as halogen‐hydride halogen bonding. In each YCCX···HMY complex, a halogen bond is formed between the positively charged X atom and the negatively charged H atom. This new kind of halogen bond has similar characteristics to the conventional halogen bond, such as the elongation of the C? X bond and the red shift of the C? X stretch frequency upon complexation. The interaction strength of this type of halogen bond is in a range of 3.34–10.52 kJ/mol, which is smaller than that of dihydrogen bond and conventional halogen bond. The nature of the electrostatic interaction in this type of halogen bond has also been unveiled by means of the natural bond orbital, atoms in molecules, and energy decomposition analyses. © 2009 Wiley Periodicals, Inc. J Comput Chem 2010