Two new tetranuclear complexes of the macrocyclic oxamide [MCu3] (M = Cd, Mn, macrocyclic oxamide = 1,4,8,11-tetraazacyclotradecanne-2,3-dione): syntheses, spectra and magnetic properties

Two new tetranuclear complexes of macrocyclic oxamide [Cd(CuL)₃](NO₃)₂·2.5H₂O 1, [Mn(CuL)₃(OH)₂](ClO₄)₂·Mn(H₂O)₆·4.5H₂O 2 (L = 1,4,8,11-tatraazacyclotradecanne-2,3-dione) have been synthesized, structurally characterized and preliminary investigated by magnetic studies. The structures of the title complexes consist of a tetranuclear units MCu₃ (M = Cd, Mn), the packing diagram shows two-dimensional and three-dimensional system through intermolecular weak interactions. The temperature-dependent magnetic susceptibilities of complex 2 were analyzed by an approximate treatment leading to J = −33 cm⁻¹, g_Cu = 2.10, g_Mn = 1.95 indicating antiferromagnetic exchange between Cu(II) and Mn(II) ions.     

Synthesis, crystal structure and properties of the Cu complex of a tetradentate imidazole-functionalized diazamesocyclic ligand, 1,4-bis(N-1-methylimidazol-2-yl-methyl)-1,4-diazacycloheptane

A new potential tetradentate ligand, 1,4-bis(N-1-methylimidazol-2-ylmethyl)-1,4-diazacycloheptane (l), together with its Cu^II complex [CulCl]ClO₄ (1), has been reported. The crystal structure of 1, determined by single-crystal X-ray analysis, shows that it is in chiral P2₁2₁2₁ space group. The Cu^II centre is penta-coordinated in square pyramidal geometry and the diazacycloheptane (DACH) ring adopts normal boat configuration. The most striking feature of this complex is the formation of a 3D network bridged through the C-H?Cl hydrogen bonds with the perchlorate anions in the cavities, and stabilized via π-π stacking interactions along the a-direction. The solution behaviour of 1 has been further investigated by UV/Vis and ESR techniques.     

Fluoropolyethers end‐capped by polar functional groups. III. Kinetics of the reactions of hydroxy‐terminated fluoropolyethers and model fluorinated alcohols with cyclohexyl isocyanate catalyzed by organotin compounds

The kinetics of the dibutyltin dilaurate (DBTDL)‐catalyzed urethane formation reactions of cyclohexyl isocyanate (CHI) with model monofunctional fluorinated alcohols and fluoropolyether diol Z‐DOL H‐1000 of various molecular weights (100–1084 g mol^?1) in different solvents were studied. IR spectroscopy and chemical titration methods were used for measuring the rate of the total NCO disappearance at 30–60 °C. The effects of the reagents and DBTDL catalyst concentrations, the solvent and hydroxyl‐containing compound nature, and the temperature on the reaction rate and mechanism were investigated. Depending on the initial reagent concentration and solvent, the reactions could be well described by zero‐order, first‐order, second‐order, or more complex equations. The reaction mechanism, including the formation of intermediate ternary or binary complexes of reagents with the tin catalyst, could vary with the concentration and solvent and even during the reaction. The results were treated with a rate expression analogous to those used for enzymatic reactions. Under the explored conditions, the rate of the uncatalyzed reaction of fluorinated alcohols with CHI was negligible. Moreover, there was no allophanate formation, nor were there other side reactions, catalysis by urethane in the absence of DBTDL, or a synergetic effect in the presence of the tin catalyst. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 3771–3795, 2002     

Potential Achilles heels of SARS-CoV-2 are best displayed by the base order-dependent component of RNA folding energy

The base order-dependent component of folding energy has revealed a highly conserved region in HIV-1 genomes that associates with RNA structure. This corresponds to a packaging signal that is recognized by the nucleocapsid domain of the Gag polyprotein. Long viewed as a potential HIV-1 "Achilles heel," the signal can be targeted by a new antiviral compound. Although SARS-CoV-2 differs in many respects from HIV-1, the same technology displays regions with a high base order-dependent folding energy component, which are also highly conserved. This indicates structural invariance (SI) sustained by natural selection. While the regions are often also protein-encoding (e. g. NSP3, ORF3a), we suggest that their nucleic acid level functions can be considered potential "Achilles heels" for SARS-CoV-2, perhaps susceptible to therapies like those envisaged for AIDS. The ribosomal frameshifting element scored well, but higher SI scores were obtained in other regions, including those encoding NSP13 and the nucleocapsid (N) protein.     

p—Si上电沉积Ni—W—P薄膜的结构与热稳定性

研究了ｐ－Ｓｉ上恒电流沉积Ｎｉ－Ｗ－Ｐ合金薄膜组成与结构的关系，讨论了镀层的组成、结构随沉积时间的变化．测定了非晶合金的晶体结构随热处理温度的改变以及ＤＴＡ曲线，结果表明，非晶Ｎｉ－Ｗ－Ｐ合金在晶化过程中形成两个纳米超微晶相，非晶Ｎｉ－Ｗ－Ｐ薄膜的热稳定性远高于通常使用的非晶Ｎｉ－Ｐ薄膜．     

Coordination solids via assembly of adaptable components: systematic structural variation in alkaline earth organosulfonate networks

A family of alkaline earth organosulfonate coordination solids is reported. In contrast to more typical crystal engineering approaches, these solids are sustained by the assembly of building blocks that are coordinatively adaptable rather than rigid in their bonding preferences. The ligand, 4,5-dihydroxybenzene-1,3-disulfonate, L, progressively evolves from a 0D, 1D, 2D, to a 3D microporous network with the Group II cations Mg(2+), Ca(2+), Sr(2+), and Ba(2+), (compounds 1-4), respectively. This trend in dimensionality can be explained by considering factors such as hard-soft acid-base principles and cation radii, a rationalization which follows salient crystal engineering principles. The selective gas sorption properties of the microporous 3D network [Ba(L)(H(2)O)].H(2)O, 4, with different gaseous guests are also presented.     

Sr3(BS3)2 und Sr3(B3S6)2: Zwei neue nicht‐oxidische Chalkogenoborate mit trigonal‐planar koordiniertem Bor

Sr₃(BS₃)₂ and Sr₃(B₃S₆)₂: Two Novel Non‐oxidic Chalcogenoborates with Boron in a Trigonal‐Planar Coordination The thioborates Sr₃(BS₃)₂ and Sr₃(B₃S₆)₂ were prepared from strontium sulfide, amorphous boron and sulfur in solid state reactions at a temperature of 1123 K. In a systematic study on the structural cation influence on this type of ternary compounds, the crystal structures were determined by single crystal X‐ray diffraction. Sr₃(BS₃)₂ crystallizes in the monoclinic spacegroup C2/c (No. 15) with a = 10.187(4) Å, b = 6.610(2) Å, c = 15.411(7) Å, β = 102.24(3)° and Z = 4. The crystal structure of Sr₃(B₃S₆)₂ is trigonal, spacegroup R3¯ (Nr. 148), with a = 8.605(1) Å, c = 21.542(4) Å and Z = 3. Sr₃(BS₃)₂ contains isolated [BS₃]^3— anions with boron in a trigonal‐planar coordination. The strontium cations are found between the layers of orthothioborate anions. Sr₃(B₃S₆)₂ consists of cyclic [B₃S₆]^3— anions and strontium cations, respectively.     

Ti接枝MCM-41催化剂的结构设计及化学亲和选择性研究

 用二氯化钛茂作为活性物种的来源，利用Si－MCM－41催化剂表面羟基的反应性，得到了Ti接枝MCM－41催化剂的两种结构模型．结构表征结果表明，Ti接枝MCM－41催化剂不仅长程结构好，孔径分布均一，而且催化剂表面活性中心含量高．两种结构模型催化剂上芳烃羟化反应性能表明，Ti接枝MCM－41催化剂表面的亲水／憎水性可以在较宽的范围内调变，从而可实现控制芳烃羟化的化学亲和选择性．另外，研究结果还表明，Ti接枝MCM－41催化剂具有很好的活性稳定性．     

用石英晶体微天平研究表面活性剂在银固态表面上的动态吸附

吸附是表面活性剂的一个重要特征.迄今用于原位监测表面活性剂在固体表面上吸附重量变化的方法尚不多见.近年来压电石英晶体作为一种高灵敏的质量传感器(石英晶体微天平)已被用于大气和溶液中多种微量成分的监测.用石英晶体微天平研究I~-、Br~-和表面活性剂在金电极上的吸附行为亦有报道.本文研究了十六烷基三甲基溴化铵(CTAB)、十二烷基磺酸钠(SDSO)、十二烷基硫酸钠(SDS)在银固态表面上的吸附平衡动力学特性及其吸附机制.     

2,4-二硝基苯丙氨酸钠盐·2,4-二硝基苯丙氨酸的合成、分子结构和二次谐波效应

合成了一种新的有非线性光学性能的标题化合物晶体NaAP·HAP,晶体属正交晶系,空间群为P2_12_12_1,a=25.773(6),b=12.377(3),c=7.2037(6)(?),z=4,D_c=1.54g·cm~(-3)。晶体结构由HAP分子(2,4-二硝基苯丙氨酸)、AP~-离子和Na~+离子组成。Na~+离子由周围的六个氧原子形成扭曲的八面体配位。这些NaO_6八面体通过共点形成无限链状结构。可用晶体结构的空间因素来解释实验测定的MAP和NaAP·HAP的二次谐波相对强度的顺序。