Mössbauer study of some Fe-containing M6 and M5 clusters

Isomer shift (δ) and quadrupole splitting (Δ) parameters have been assigned to the iron sites in [FeRh₅(CO)₁₆]⁻, trans- and cis-[Fe₂Rh₄(CO)₁₆]²⁻, [Fe₃-Rh₃(CO)₁₇]³⁻, [FeRh₄(CO)₁₅]²⁻, [Fe₃Pt₃(CO)₁₅]²⁻ and [Fe₄M(CO)₁₆]²⁻ (M = Pd or Pt) from ⁵⁷Fe Mössbauer spectra recorded at 78 K. The data for the closo compounds [FeRh₅(CO)₁₆]⁻ and [Fe₂Rh₄(CO)₁₆]²⁻ are compared with those for [Fe₆(CO)₁₆C]²⁻. In [Fe₃Rh₃(CO)₁₇]³⁻, the three major Fe sites were identified. For both [Fe₄M(CO)₁₆]²⁻ compounds two isomers were shown to be present in the solid state.     

Electronic coupling in covalently-linked MM quadruple bonds: M2δ to ligand π conjugation

Dimetal tetracarboxylates, M₂(O₂CR)₄, where R=alkyl and M=Mo or W, can be linked in a perpendicular or parallel manner through the agency of a variety of ligands to give ‘dimers of dimers’ [M₂(O₂CR)₃]₂(bridge), or extended chains. A ring of formula [M₂(O₂CR)₂(bridge)]₄ is an alternative to a chain [M₂(O₂CR)₃]₂(bridge)₂]_∞ and ‘molecular squares’ of formula [(RNCHNR)₂M₂(bridge)]₄ have recently been reported by Cotton and Murillo, where M=Mo and Rh and R=p-MeOC₆H₄. The electronic coupling between the M₂ units manifests itself in electrochemical data and in the electronic spectra of the compounds. The electronic coupling occurs by M₂δ to ligand π-conjugation and specific examples are illustrated for the bridging ligands oxalate, perfluoroteraphthalate, 1,8-anthracenedicarboxylate and 2,7-dioxynaphthyridine. Correlations of a variety of spectroscopic data and computations employing density functional theory are presented.     

三元体系MCl-M′Cl-HOAc(25℃)的研究(M,M′=K、Rb、Cs,M≠M′)

测定了25℃下KCl-RbCl-HOAc,KCl-CsCl-HOAc,RbCl-CsCl-HOAc三个体系的溶度数据,绘制了相应的相图以及分配图。第一个体系中只有一种固相存在,属于Roozeboom第Ⅰ型;后两个体系互溶性都有十分明鲜的裂隙,但比以水为溶剂的体系中的互溶性显著增强,二者均属Roozeboom第Ⅳ型。     

Tunability of the M(II)M(III)/M(II)(2) and M(III)(2)/M(II)M(III) (M=Mn, Co) couples in bis-μ-O,O'-carboxylato-μ-OR bridged complexes

A comparison of the electrochemical properties of a series of dinuclear complexes [M(2)(L)(RCO(2))(2)](+) with M = Mn or Co, L = 2,6-bis(N,N-bis-(2-pyridylmethyl)-sulfonamido)-4-methylphenolato (bpsmp(-)) or 2,6-bis(N,N-bis(2-pyridylmethyl)aminomethyl)-4-tert-butylphenolato (bpbp(-)) and R = H, CH(3), CF(3) or 3,4-dimethoxybenzoate demonstrates: (i) The electron-withdrawing sulfonyl groups in the backbone of bpsmp(-) stabilize the [M(2)(bpsmp)(RCO(2))(2)](+) complexes in their M(II)(2) oxidation state compared to their [M(2)(bpbp)(RCO(2))(2)](+) analogues. Manganese complexes are stabilised by approximately 550 mV and cobalt complexes by 650 mV. (ii) The auxiliary bridging carboxylato ligands further attenuate the metal-based redox chemistry. Substitution of two acetato for two trifluoroacetato ligands shifts redox couples by 300-400 mV. Within the working potential window, reversible or quasi-reversible M(II)M(III)? M(II)(2) processes range from 0.31 to 1.41 V for the [Co(2)(L)(RCO(2))(2)](+/2+) complexes and from 0.54 to 1.41 V for the [Mn(2)(L)(RCO(2))(2)](+/2+) complexes versus Ag/AgCl for E(M(II)M(III)/M(II)(2)). The extreme limits are defined by the complexes [M(2)(bpbp)(CH(3)CO(2))(2)](+) and [M(2)(bpsmp)(CF(3)CO(2))(2)](+) for both metal ions. Thus, tuning the ligand field in these dinuclear complexes makes possible a range of around 0.9 V and 1.49 V for the one-electron E(M(II)M(III)/M(II)(2)) couple of the Mn and Co complexes, respectively. The second one-electron process, M(II)M(III)? M(III)(2) was also observed in some cases. The lowest potential recorded for the E°(M(III)(2)/M(II)M(III)) couple was 0.63 V for [Co(2)(bpbp)(CH(3)CO(2))(2)](2+) and the highest measurable potential was 2.23 V versus Ag/AgCl for [Co(2)(bpsmp)(CF(3)CO(2))(2)](2+).     

M受体拮抗剂的研究进展

毒蕈碱受体是人体内一种重要的胆碱受体,广泛分布于中枢和周围神经系统、心肌、平滑肌及腺体等组织中,参与机体多种重要的生理功能.设计与合成对M受体产生拮抗或激动作用的化合物已经成为研究能够治疗膀胱过度活动症、呼吸道及支气管疾病、近视和心律失常等疾病药物的重要途径.本文主要介绍了作用于不同M受体亚型拮抗剂的研究进展.     

Halogen bonds and metal bonds involving superalkalies M2OCN/M2NCO (M = Li,Na) complexes

Structural Chemistry - A new type of halogen bond formed by supermetals or superalkalies with dihalogen molecules was analyzed by means of ab initio at the MP2/aug-cc-pVTZ level. The results reveal...     

Mbius结构理论与首次全合成分子的Mbius带

一、引言A.F.M(?)bius(或 Moebius)是德国数学家。M(?)bius 带的简单模型可用一条纸带将一端扭转180°,然后将两端粘接起来表示。这样形成的带,既没有内面,也没有外面,内面和外面相结合形成一个连续状态,成为具有一个边一个     

Study of series of the M1,M2‖F,Cl,Br quaternary reciprocal systems (M1 and M2 are group 1 s-block elements)

Quaternary reciprocal systems of alkali metal fluorides, chlorides, and bromides were partitioned into simplexes by a geometric method and a graph method. Phase transformations and chemical reactions in the bordering ternary reciprocal systems were described. Conversion lines were experimentally studied, and information on crystallizing phases within the composition prisms of the M₁,M₂‖F,Cl,Br systems (M₁ and M₂ are group 1 s-block elements) was obtained.     

M2TNR(M=AG, CHZ)的制备和晶体结构

通过三硝基间苯二酚(TNR,斯蒂酚酸)和氨基胍(AG)重碳酸盐、碳酰肼(CHZ)反应,制备斯蒂酚酸氨基胍和斯蒂酚酸碳酰肼。并用X-射线衍射分析、元素分析、差示扫描量热法和红外光谱对其进行了结构表征。它们的分子式分别为(NH2NHCNHNHNH2)2^+[C6H(NO3)3O2]^2.0.5H2O,(NH2NHCONHNH3)2^+[C6H(NO3)3O2]^2^-,二者都属于单斜晶系,C2/c空间群。     

Transition-metal-centered nine-membered boron rings: MⓒB9 and MⓒB9(-) (M = Rh, Ir)

We report the observation of two transition-metal-centered nine-atom boron rings, Rh?B(9)(-) and Ir?B(9)(-). These two doped-boron clusters are produced in a laser-vaporization supersonic molecular beam and characterized by photoelectron spectroscopy and ab initio calculations. Large HOMO-LUMO gaps are observed in the anion photoelectron spectra, suggesting that neutral Rh?B(9) and Ir?B(9) are highly stable, closed shell species. Theoretical calculations show that Rh?B(9) and Ir?B(9) are of D(9h) symmetry. Chemical bonding analyses reveal that these complexes are doubly aromatic, each with six completely delocalized π and σ electrons, which describe the bonding between the central metal atom and the boron ring. This work establishes firmly the metal-doped B rings as a new class of novel aromatic molecular wheels.     

Mössbauer Spectroscopy of Spinels

Soon after the discovery of the Mössbauer effect, studies were performed on spinels containing various transition metal ions (mostly Fe²⁺). This method proved very useful for investigating the local symmetry at transition metal ions. In spite of the numerous results, the correct interpretation of the complex quadrupole split spectra is still not given for numerous spinel structures. Since spectra of different shapes were measured for FeAl₂O₄ and FeCr₂O₄ by different authors, we performed new measurements on these spinels. The results on FeAl₂O₄ showed that the statistical distribution of another kind of ions in the positions A may influence the electric field gradient at the Fe²⁺ ions in the tetrahedral interstices. In FeCr₂O₄ and in the mixed Fe_0.5Mg_0.5Cr₂O₄, the electric field gradient exists at the Fe²⁺ ions at room temperature indicating that the degeneracy of the orbital doublet of the Fe²⁺ is removed.     

系列线型[M2M‘S4O4]^2—簇的合成及光谱与结构的关系（M=Mo,W;M…

报道了６种线型簇合物（Ｅｔ４Ｎ）２（Ｍ２Ｍ＇Ｓ４Ｏ４）（Ｍ＝Ｍｏ，Ｗ；Ｍ＇＝ＣＯ，ＮＩ，Ｆｅ）的合成，通过对ＵＶ－Ｖｉｓ，ＩＲ及ＸＰＳ光谱的对比分析，讨论了簇阴离子（ＭＷＭ＇Ｓ４Ｏ４）＾２－中心金属Ｍ＇的ｄ电子结构、氧化态以及（Ｍ＇Ｓ４）的微环境，由此推了簇阴离子构型，并讨论了化合物的稳定性。     

Erweiterte M?glichkeiten der Flammenphotometrie

Zusammenfassung Der Zusatz von n-Butanol führt zu einer erheblichen Erweiterung der analytischen Möglichkeiten bei der quantitativen flammenspektrometrischen Bestimmung.Bei allen untersuchten Spektren werden die Intensitäten der Linien und Banden erheblich verstärkt. Die besonders starke Anregung der Banden ermöglicht eine weitgehende Ausnützung der Bandenspektren für analytische Zwecke.Verschiedene Banden und Linien der Elemente erscheinen überhaupt erst nach Zugabe von n-Butanol in einer vermeßbaren Größe.Die gegenseitige Beeinflussung der Elemente wird wesentlich geringer.Durch die Messung der effektiven Linien bzw. Bandenintensitäten können Störungen, die ihre Ursache in einer Beeinflussung der jeweiligen Intensität des Kontinuums haben, ausgeschaltet werden.Mitgliedsinstitut der AIF (Arbeitsgemeinschaft Industrieller Forschungsvereinigungen).Die vorliegende Arbeit wurde mit finanzieller Unterstützung des Bundeswirtschaftsministeriums durchgeführt. Es sei an dieser Stelle dafür verbindlichst gedankt.     

Thermodynamic investigation on M–Te–O (M = Sc, Y) system

The standard Gibbs energy of formation of M₂TeO₆ and M₆TeO₁₂ (where M = Sc, Y), was determined from its vapor pressure measurements by employing thermogravimetry-based transpiration technique. This technique was validated by measuring the vapor pressure of well-studied substances such as TeO₂(s) and CdCl₂(s). The temperature dependence of the vapor pressure of TeO₂(g) over the mixtures M₆TeO₁₂ + M₂O₃ (where M = Sc, Y), generated by the incongruent vaporization reaction, M₆TeO₁₂(s) → 3M₂O₃(s) + TeO₂(g) + ½O₂(g) were measured in the temperature range 1,413–1,473 K and 1,623–1,743 K for Sc₆TeO₁₂(s) and Y₆TeO₁₂(s), respectively. Similarly, the vapor pressure of TeO₂(g) over the mixtures M₂TeO₆(s) + M₆TeO₁₂(s) generated by the vaporization reaction, 3M₂TeO₆(s) → M₆TeO₁₂(s) + 2TeO₂(g) + O₂(g) was measured in the temperature range (1,223–1,293 K) and (1,333–1,423 K) for Sc₂TeO₆(s) and Y₂TeO₆(s), respectively. From the vapor pressure measurements, the standard Gibbs energy of formation of M₆TeO₁₂ and M₂TeO₆ were derived.     

金属串配合物[MM′M″(dpa)4(Cl)2](M=Co,Ni;M′,M″=Co,Rh)电子输运的理论研究

采用密度泛函理论DFT/BP86方法研究金属串配合物[MM'M″(dpa)₄(Cl)₂] [MM'M″=CoCoCo(1), CoCoRh(2), CoRhRh(3), NiCoRh(4)] 的结构和电子输运性质. 结果表明, 配合物1, 2和4的最稳定自旋态均存在1个(MM'M″)⁶⁺的离域$\sigma_{3}^{3}$键($\sigma^{2}\sigma_{nb}^{1}\sigma^{*0}$); 但配合物3具有1个(MM'M″)⁶⁺的离域$\sigma_{3}^{4}$键($\sigma^{2}\sigma_{nb}^{2}\sigma^{*0}$)和2个$\pi_{3}^{5}$键($\pi^{4}\pi_{nb}^{4}\pi^{*2}$), 故Rh—Rh键和Co—Rh键较强; Rh的引入使M—M键增强, Ni的引入则使M—M键减弱, 键强次序为Rh—Rh>Co—Rh>Co—Co>Ni—Co. 配合物14的传输通道均含有π和σ型轨道. 正偏压下, 配合物2和3的电流大于配合物1和4的. 负偏压下, 配合物4中出现负微分电阻效应. 配合物3中形成传输通道的σ_nbα/β和π^*α/β轨道能级分裂明显, (MM'M″)⁶⁺对β自旋的π^*轨道的贡献(88%)比α自旋(74%)的大, 使β自旋的电子更易传输, 具有较好的自旋过滤效应(70%80%).