Effect of Anion-Induced Cation Adsorption on the Electrical Double Layer Structure

Effect of supporting cations on the EDL structure is analyzed in the region of specific adsorption of anions. The analysis assumes that cations are pulled into the EDL dense part due to their interaction with specifically-adsorbed anions. The model describing this phenomenon is based on the introduction of a second, cationic IHP situated between the plane where centers of charges of specifically-adsorbed anions are localized and OHP. The adsorption of ions, electrode charge, PZC, and EDL capacitance are calculated using two adsorption isotherms for anions and cations.     

Infrared Spectroscopy and Structure of Trigonal Zirconium Orthophosphates with Lanthanides and Actinides

Binary zirconium orthophosphates R_1/3Zr₂(PO₄)₃ and M_1/4Zr₂(PO₄)₃, where R = Y, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu; M = Th, U, have been synthesized and studied by IR spectroscopy [structural family of NaZr₂(PO₄)₃ (NZP)]. Vibrational analysis for the PO₄ tetrahedron and investigation of symmetry relations among trigonal NZP phases showed that ordering of lanthanide atoms in structures of NaZr₂(PO₄)₃ type with space group R c leads to symmetry reduced to P c. The lanthanide atoms occupy the 2b sites. The phosphorus atoms occupy two independent sites: 6f with C ₂ symmetry and 12g with C ₁ symmetry. Factor group analysis admits that the IR spectrum can contain eight v₃ bands and two v₁ bands of the stretching vibrations of the PO₄ ions. The M atoms of actinides occupy statistical positions in the structure, and space group R c is retained.Original Russian Text Copyright © 2004 by V. S. Kurazhkovskaya, D. M. Bykov, and A. I. Orlova__________Translated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 6, pp. 1013–1019, November–December, 2004.     

DNA Quadruplex Structure with a Unique Cation Dependency

DNA quadruplex structures provide an additional layer of regulatory control in genome maintenance and gene expression and are widely used in nanotechnology. We report the discovery of an unprecedented tetrastranded structure formed from a native G-rich DNA sequence originating from the telomeric region of Caenorhabditis elegans. The structure is defined by multiple properties that distinguish it from all other known DNA quadruplexes. Most notably, the formation of a stable so-called KNa-quadruplex (KNaQ) requires concurrent coordination of K⁺ and Na⁺ ions at two distinct binding sites. This structure provides novel insight into G-rich DNA folding under ionic conditions relevant to eukaryotic cell physiology and the structural evolution of telomeric DNA. It highlights the differences between the structural organization of human and nematode telomeric DNA, which should be considered when using C. elegans as a model in telomere biology, particularly in drug screening applications. Additionally, the absence/presence of KNaQ motifs in the host/parasite introduces an intriguing possibility of exploiting the KNaQ fold as a plausible antiparasitic drug target. The structure's unique shape and ion dependency and the possibility of controlling its folding by using low-molecular-weight ligands can be used for the design or discovery of novel recognition DNA elements and sensors.     

Double Double Cation Order in the High‐Pressure Perovskites MnRMnSbO6

Cation ordering in ABO₃ perovskites adds to their chemical variety and can lead to properties such as ferrimagnetism and magnetoresistance in Sr₂FeMoO₆. Through high‐pressure and high‐temperature synthesis, a new type of “double double perovskite” structure has been discovered in the family MnRMnSbO₆ (R=La, Pr, Nd, Sm). This tetragonal structure has a 1:1 order of cations on both A and B sites, with A‐site Mn²⁺ and R³⁺ cations ordered in columns and Mn²⁺ and Sb⁵⁺ having rock salt order on the B sites. The MnRMnSbO₆ double double perovskites are ferrimagnetic at low temperatures with additional spin‐reorientation transitions. The ordering direction of ferrimagnetic Mn spins in MnNdMnSbO₆ changes from parallel to [001] below T_C=76 K to perpendicular below the reorientation transition at 42 K at which Nd moments also order. Smaller rare earths lead to conventional monoclinic double perovskites (MnR)MnSbO₆ for Eu and Gd.     

人工神经网络用于预测离子交换分配系数

用前向神经和扩展的ｄｅｌｔａ－ｂａｒ－ｄｅｌｔａ算法对主族特征价阳离子的离子交换分配系数（Ｋｄ）进行了预测，对网络结构，学习次数进行了优化并研究了学习集的大小，１ｎＫｄ的均方根偏差的（ＲＭＳ）小于７％。     

ESR Studies on N-Alkylphenothiazine Radical Cation Salts

ＥＳＲＳｔｕｄｉｅｓｏｎＮ－ＡｌｋｙｌｐｈｅｎｏｔｈｉａｚｉｎｅＲａｄｉｃａｌＣａｔｉｏｎＳａｌｔｓＧＵＯＱｉｎｇ－ｘｉａｎｇ￣（１,２）,ＬＩＵＢｏ￣１ａｎｄＬＩＵＹｏｕ－ｃｈｅｎｇｉ￣（１,２）．（￣＊ＮａｔｉｏｉｉａｌＬａｂｏｒａｔｏｒｙｏｆＡ...     

固相萃取-分光光度法测定海水中痕量活性磷酸盐

磷钼蓝（PMB）与十六烷基三甲基溴化铵（CTMAB）可生成疏水性的PMB-CTMAB离子缔合物,被Sep—Pak C18小柱萃取富集,基于此建立了SEP—PAK C18小柱固相萃取-分光光度法测定海水中痕量活性磷酸盐的新方法。对洗脱液酸度、萃取流速、试剂用量、反应时间与温度等实验参数进行了优化选择,并考察了盐度对测定结果的影响。实验结果表明,PMB-CTMAB在SEP-PAK C19小柱上可被有效地定量萃取;盐度在25～45范围内,对测定结果没有影响。在优化的实验条件下,以盐度为35的人工海水作为基底,方法的线性范围为0．18～4．00μg/L;平均回收率为98．5％;检出限为0．05μg／L。对实际海水中痕量活性磷酸盐进行测定,相对标准偏差（RSD）为2．7％-5．6％。与广泛采用的MAGIC法比较,结果无显著差异。新方法具有消耗试样体积少、测定速度快等优点。     

Structure and Reactivity of the 1,10-Phenanthroline Complex with Nitrenium Cation

According to the X-ray diffraction data, the cationic fragment in 1-amino-1,10-phenanthrolinium mesitylenesulfonate is a unidentate n-complex whose asymmetric structure is retained in solution. Quantum-chemical calculations by the AM1 method and ab initio (6-31G, 6-31G*, MP2/6-31G) give geometric parameters of the cation, which are similar to those determined experimentally. No dynamic processes involving intra- or intermolecular transfer of the NH2 group was observed up to 100°C by NMR spectroscopy. 1-Amino-1,10-phenanthrolinium cation does not react with 4-methylpyridine and 4-methyl-1,10-phenan-throline with transfer of the amino group, and it fails to react with mesitylene and anthracene at elevated temperature.     

Molecular and Crystal Structure of 1,10-Phenanthroline Complex with Nitrosonium Cation

1,10-Nitroso-1,10-phenanthrolinium tetrafluoroborate was subjected to X-ray diffraction analysis. A distinctive feature of the complex is the NO group position between two nitrogen atoms of the phenanthroline skeleton, and so the complex may be regarded as belonging to bidentate type. The distance from the N atom of the group to the nitrogens of the skeleton are approximately equal (2.3 Å) and are considerably shorter that the average intermolecular contacts of the pair of nitrogen atoms N...N (3.0 Å). In the crystal two types of cations are present where the NO groups are oriented at angles 54 and 61° with respect to phenanthroline skeleton, and the length of N-O bonds is close to that in NO⁺ cation. The geometrical parameters of cation obtained by ab initio calculations are close to experimental data.     

超分子结构草甘膦插层水滑石的组装及结构研究

提出了一种新的绿色农药缓释剂模型——超分子结构草甘膦缓释剂.依据插层组装理论,以阴离子层状材料镁铝水滑石(MgAl-LDH)为插层主体,以除草剂草甘膦为插层客体,由共沉淀法一步组装得到超分子结构草甘膦插层镁铝水滑石(MgAl-LDH-gly).通过对MgAl-LDH-gly的结构、主客体相互作用及化学组成确认,建立了MgAl-LDH-gly的近似超分子结构模型,并对其缓慢释放草甘膦的可行性进行了分析.     

一个新的二茂铁-钴四核双螺旋配合物的合成，结构和电化学性质研究

利用1，1′-双羧酸二茂铁为配体设计合成了一个新的二茂铁-钴四核双螺旋配合物并研究了其电化学性能。该配合物具有一个垂直于其螺旋轴的C₂对称性，四个金属中心形成一个边长为5.4?菱形结构。二茂铁配体的两个羧基以顺式结构与两个金属中心配位。电化学研究表明作为桥联基团的金属钴配位中心能够有效传递二茂铁基团间的氧化还原性能。     

Syntheses and Cation Complexation Studies of New Cavitand Derivatives

A series of new cavitands containing four esters, nitriles, 2-pyridyl, or 3-pyridyl groups were synthesized fromtetrahydroxycavitand. Their binding properties towards various metal ions are investigated.     

土壤阳离子交换量测定方法的比较研究

本文介绍了BaCl_2-三乙醇胺法与EDTA-铵盐快速法的比较。目前我国测定土壤阳离子交换量广泛采用的EDTA-铵盐快速法。具有简使快速的优点。但此法的主要缺点是难以取得正确的结果,即以95%酒精洗去过量交换剂时,多余交换剂未完全洗去,结果偏高,洗     

Synthesis,Identification and Thermal Decomposition of Double Sulphates of Some Lanthanides and Y with Ethanolammonium Cation

On evaporation at room temperature of an aqueous mixture of Ln(III) sulphate and ethanolammonium sulphate in a molar ratio higher than 1:12, in the presence of sulphuric acid, double sulphates of Sm, Eu, Ho, Tm, Yb and Y with a waxy feel were obtained. The stoichiometry of the obtained compounds was determined by means of elemental and TG analysis. On the basis of X-ray powder diffraction patterns it was concluded that an isostructural group with a general formula: Ln₂(HOCH₂CH₂NH₃)₈(SO₄)₇·8H₂O was obtained. The above compounds have a stoichiometry and a crystal structure different from those of the double sulphates of La, Ce, Pr and Nd with the same monovalent cation, as presented earlier. The thermal decomposition of the investigated compounds in the temperature range from ambient temperature up to 1173 K occurred in a similar way, mainly in three not well-differentiated steps. Lanthanide oxysulphates were obtained as final products. This revised version was published online in July 2006 with corrections to the Cover Date.     

Isolation of a Three‐Coordinate Boron Cation with a Boron–Sulfur Double Bond

The reaction of the bulky bis(imidazolin‐2‐iminato) ligand precursor (1,2‐(L^MesNH)₂‐C₂H₄)[OTs]₂ ( 1 ²⁺ 2[OTs]^?; L^Mes=1,3‐dimesityl imidazolin‐2‐ylidene, OTs=p‐toluenesulfonate) with lithium borohydride yields the boronium dihydride cation (1,2‐(L^MesN)₂‐C₂H₄)BH₂[OTs] ( 2 ⁺ [OTs]^?)_. The boronium cation 2 ⁺ [OTs]^? reacts with elemental sulfur to give the thioxoborane salt (1,2‐(L^MesN)₂‐C₂H₄)BS[OTs] ( 3 ⁺ [OTs]^?). The hitherto unknown compounds 1 ²⁺ 2[OTs]^?, 2 ⁺ [OTs]^?, and 3 ⁺ [OTs]^? were fully characterized by spectroscopic methods and single‐crystal X‐ray diffraction. Moreover, DFT calculations were carried out to elucidate the bonding situation in 2 ⁺ and 3 ⁺. The theoretical, as well as crystallographic studies reveal that 3 ⁺ is the first example for a stable cationic complex of three‐coordinate boron that bears a B?S double bond.