Steric effects of substituted quinolines on lithium coordination geometry

The X-ray crystal structures of a series of lithium quinolates – lithium 8-hydroxyquinolinate (Liq), lithium 2-methyl-8-hydroxyquinolinate (MeLiq), and 2-phenyl-8-hydroxquinolinate (PhLiq), are compared. The substitution at the 2-position of the 8-hydroxyquinoline ligand has significant impact on the aggregation of the lithium complex in the crystalline state. Liq and MeLiq molecules crystallize as hexamers, whereas PhLiq crystallizes as a tetramer. The possible influence of crystal-packing forces on the preferred cluster structure was probed using density functional theory calculations on a systematically varied set of Liq, MeLiq, and PhLiq clusters. For Liq and MeLiq, the observed structures match the most stable computed structures. In the PhLiq case, the observed tetrameric structure is computed to be less stable (+1.2 kcal/mol/monomer) than the lowest energy structure, a hexamer. In this case, solid-state effects probably outweigh small differences in cluster stability.     

Gold Nanoparticles as Effective ion Traps in Poly(dimethylsiloxane) Cross-Linked by Metal-Ligand Coordination

At this time, the development of advanced elastic dielectric materials for use in organic devices, particularly in organic field-effect transistors, is of considerable interest to the scientific community. In the present work, flexible poly(dimethylsiloxane) (PDMS) specimens cross-linked by means of ZnCl₂-bipyridine coordination with an addition of 0.001 wt. %, 0.0025 wt. %, 0.005 wt. %, 0.04 wt. %, 0.2 wt. %, and 0.4 wt. % of gold nanoparticles (AuNPs) were prepared in order to understand the effect of AuNPs on the electrical properties of the composite materials formed. The broadband dielectric spectroscopy measurements revealed one order of magnitude decrease in loss tangent, compared to the coordinated system, upon an introduction of 0.001 wt. % of AuNPs into the polymeric matrix. An introduction of AuNPs causes damping of conductivity within the low-temperature range investigated. These effects can be explained as a result of trapping the Cl⁻ counter ions by the nanoparticles. The study has shown that even a very low concentration of AuNPs (0.001 wt. %) still brings about effective trapping of Cl⁻ counter anions, therefore improving the dielectric properties of the investigated systems. The modification proposed reveals new perspectives for using AuNPs in polymers cross-linked by metal-ligand coordination systems.     

BaY2F8晶体生长基元与结晶机理的探讨

本文通过对BaY2F8晶体结构的分析,从晶体的生长基元为负离子配位多面体理论出发,对自然冷却条件下BaY2F8晶体自发结晶习性进行了研究,提出了以Ba2+为中心的近八配位十二面体和以Y3+为中心的近八配位十二面体是晶体生长的基元.并根据自发结晶的BaY2F8的XRD,说明了BaY2F8晶体的{200}、{130}、{021}、{330}、{-111}、{111}、{221}、{002}等面族比较发育的原因.本文证实了仲维卓的负离子配位多面体理论对BaY2F8晶体生长的适用性,并对探索新的BaY2F8单晶生长方法有参考作用.     

一种锌配合物用于炭疽生物标志物的检测

采用溶剂热合成方法,合成了一种新型金属配位聚合物{[Zn₂(L)(H₂O)(DMA)]·DMA·2.3H₂O}_n (1),其中L^4-为完全脱去质子的N,N''-二(4-羧基苄基)-5-氨基间苯二甲酸,DMA为N,N-二甲基乙酰胺。单晶X射线衍射结果显示,该配合物属于三斜晶系,空间群为P$overline{1}$,a=0.989 6(5) nm,b=1.370 5(5) nm,c=1.382 1(5) nm,α=80.067(5)°,β=76.729(5)°,γ=76.611(5)°,结构是由二维金属有机层通过π…π相互作用而扩展成的三维超分子骨架。红外光谱验证了锌离子与L^4-配体成功配位。粉末X射线衍射(PXRD)实验证实了配合物1具有较高的纯度。热重分析结果显示配合物1在室温至416.9 ℃区间内具有较好的热稳定性。在273 nm的激发光下,配合物1在437 nm处有较强的荧光发射,可以在30 s内快速检测乙醇溶液中的炭疽生物标志物——吡啶-2,6-二甲酸,具有选择性高、抗干扰能力强、检测限低(约为15 μmol·L^-1)等特点。结合PXRD图和紫外可见吸收光谱揭示了其检测机理为晶体骨架坍塌而诱导的荧光猝灭。     

Effect of solvent on the construction of Co(II) coordination polymers containing a semi-rigid bis(benzimidazole) derivative: syntheses,structures, and properties

Two Co(II) coordination polymers, [CoL(npa)]·2H₂O (1) and [CoL(Hnpa)₂] (2) (L = 1,4-bis(5,6-dimethylbenzimidazole-1-yl)benzene, H₂npa = 5-nitroisophthalic acid), have been synthesized in different solvent systems and characterized by Infrared (IR) spectroscopy, elemental analysis, and powder and single crystal X-ray diffraction. Compound 1 was synthesized under solvothermal conditions with DMF as solvent and had a pair of L ligands adopting a μ₂-bridging mode and connecting two Co²⁺ cations to generate a 26-membered Co₂L₂ loop. The npa^2? link adjacent Co₂L₂ loops via a bis(monodentate) bridging mode to create a 1-D channel-like chain structure. Compound 2 was obtained under hydrothermal conditions, and the carboxylate of the monodeprotonated Hnpa^? adopt a μ₁-η^0?:?η¹ coordination to connect adjacent Co²⁺ cations into a 2-D polymeric layer. The μ₂-bridging L ligands connect adjacent 2-D [Co(Hnpa)]_n polymeric layers into a 3-D NaCl-like framework. The Co²⁺ cations and the L ligands in compounds 1 and 2 exhibit different coordination geometries and conformations. Effects of solvents on the construction of Co(II) coordination polymers were investigated. In addition, the electrochemical behavior of carbon paste electrodes containing 1 and 2 and the thermal stabilities of 1 and 2 were investigated.     

Strategic commitment to price to stimulate downstream innovation in a supply chain

It is generally in a firm’s interest for its supply chain partners to invest in innovations. To the extent that these innovations either reduce the partners’ variable costs or stimulate demand for the end product, they will tend to lead to higher levels of output for all of the firms in the chain. However, in response to the innovations of its partners, a firm may have an incentive to opportunistically increase its own prices. The possibility of such opportunistic behavior creates a hold-up problem that leads supply chain partners to underinvest in innovation. Clearly, this hold-up problem could be eliminated by a pre-commitment to price. However, by making an advance commitment to price, a firm sacrifices an important means of responding to demand uncertainty. In this paper we examine the trade-off that is faced when a firm’s channel partner has opportunities to invest in either cost reduction or quality improvement, i.e. demand enhancement. Should it commit to a price in order to encourage innovation, or should it remain flexible in order to respond to demand uncertainty. We discuss several simple wholesale pricing mechanisms with respect to this trade-off.     

Evolutionary insights on the willingness to communicate

While in previous models of pre-play communication players are forced to communicate, we investigate what happens if players can choose not to participate in this cheap talk. Outcomes are predicted by analyzing evolutionary stability in a population of a priori identical players. If the game following the communication rewards players who choose the same action then an efficient outcome is only guaranteed when participation in the pre-play communication is voluntary. If however players aim to coordinate on choosing different actions in the underlying game and there are sufficiently many messages then the highest payoff is selected when players are forced to talk to each other before playing the game. Received: September 2000/Revised: March 2003     

On the Application of the Auxiliary Problem Principle

The auxiliary problem principle (APP) derives from a general theory on decomposition-coordination methods establishing a comprehensive framework for both one-level and two-level methods. In this paper, the results of the two-level methods of APP are specialized for an efficient application to some engineering problems.     

Evaluating Individual Market Power in Electricity Markets via Agent-Based Simulation

We use agent-based simulation in a coordination game to analyse the possibility of market power abuse in a competitive electricity market. The context of this was a real application to the England and Wales electricity market as part of a Competition Commission Inquiry into whether two particular generators could profitably influence wholesale prices. The research contributions of this paper are both in the areas of market power and market design policy issues for electricity markets, and in the methodological use of large industry-wide evolutionary simulation models.     

二茂铁有机锡衍生物的13C,119Sn NMR研究

本文测定了几种二茂铁有机锡衍生物的¹¹⁹Sn,¹³C NMR谱。对其中几种衍生物的¹³C NMR谱进行了归属,从而进一步验证了这类化合物的结构。着重讨论了结构如化合物中取代基X的改变对¹¹⁹Sn化学位移的影响。并对结构如 类化合物N→Sn异侧配位的问题进行了讨论。