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131.
Fathi M. A. M. Aqra Shakeel A. Shah Sartaj Tabassum Rasheed M. A. Q. Jamhour Khwaja S. Siddiqi Osama Al-Jowder Fawzia Al-Saleh 《Transition Metal Chemistry》1995,20(2):123-125
Summary New ionic bimetallic complexes of the type [Cu(en)2]-[MCl4], where M = CuII, ZnII, CdII and HgII, were prepared by reacting bis(ethylenediamine)copper(II) dichloride (1 mol) with copper, zinc, cadmium and mercury dichlorides (1 mol) in absolute alcohol. Elemental analyses, conductivity and magnetic susceptibility measurements, and spectroscopic data (such as i.r., u.v.-vis. and e.p.r.) confirm that the compounds are 22 electrolytes in MeOH and that the copper(II) ion is paramagnetic, maintaining its square-planar geometry, while metal ions in the anionic moiety of the complexes achieve their usual tetrahedral environment. An augmented magnetic moment has been observed in the [Cu(en)2] [CuCl4] complex, which is attributed to the ferromagnetic effect and TIP.Author to whom all correspondence should be directed. 相似文献
132.
Fasih A. Siddiqi Santosh K. Saksena Ibadur Rahman Khan 《Journal of polymer science. Part A, Polymer chemistry》1977,15(8):1935-1956
Diffusion rate of biologically important electrolytes through parchment-supported silver chloride membrane have been determined by the use of Nernst-Planck equation at various temperatures taking into account membrane resistance Rm, membrane potential Em, etc. The diffusion rates were found to be primarily dependent upon the difference in the hydration energies of the counterion in the external solution. On the basis of Eisenman-Sherry theory the diffusion rate sequence of alkali metal cations point towards the weak field strengths of the fixed charge groups. The various thermodynamic parameters, namely, ΔH?, ΔF?, and ΔS? were evaluated. The values of ΔS? found to be negative, indicating that the diffusion is taking place with partial immobilization in the membrane phase. A formal relation between ΔHhydration, ΔFhydration, and ΔShydration of cations with the corresponding values of ΔH?, ΔF?, and ΔS? for diffusion was also found to exist for the investigated system. 相似文献
133.
Summary Reaction of 4-cyano-5-aminopyrazole, Hcpz, with ammoniacal solutions of metal(I) chlorides yields colorless and insoluble polymeric complexes, [Mcpz]n [where M=Cu(1) or Ag(2)]. However, pyrazolidebridged dimeric species [M(PPh3)2cpz]2
(3) or(4), soluble in most non-polar solvents, were obtained from the precursor [M(PPh3)3X] (X=Cl or NO3) under similar reaction conditions. The compounds have been characterized using physico-chemical methods and are diamagnetic. 相似文献
134.
Salman R. Salman Akl M. Awwad Etamad I. Allos Ayshan A. Hakim 《Journal of solution chemistry》1987,16(7):567-570
The interactions of N-formylmorpholine (NFM) with different alkanols were monitored using proton nuclear magnetic resonance and IR spectroscopy. It was found that the NFM interaction with alkanols decreases with increasing length and branching of the alkanols. A good correlation was obtained between the proton chemical shift and the volume of mixing of alkanols with NFM. 相似文献
135.
Lipophilic quaternary ammonium cations are insoluble in water when paired with any anion except fluoride or hydroxide. This phenomenon is the basis for a novel method for total anion determination. Tetra-n-octylammonium fluoride (TOAF) is used for the direct titration of any anion or mixture of anions with the exception of hydroxide. Anions for which no direct analytical method exists, e.g., nitrate or hydrogenfluoride (HF2?), are simply assayed by conductimetric titration with TOAF reagent. 相似文献
136.
Mohammad Shakir Ajax K. Mohamed Saji P. Varkey Zafar A. Siddiqi 《Transition Metal Chemistry》1996,21(2):162-165
Summary The synthesis of a new series of 14- and 16-membered hexaazamacrocyclic complexes has been achieved by the template condensation of ethylenediamine or 1,3-propylenediamine with formaldehyde and acetamide in a 121 molar ratio in the presence of metal chlorides. Octahedral structural formulae for selective metal complexes are proposed on the basis of physico-chemical and spectroscopic data. The redox behaviour in DMSO solution of the CuII complexes has been studied by cyclic voltammetry. 相似文献
137.
Mahamed G. H. Omran Salah al-Sharhan Ayed Salman Maurice Clerc 《Computational Optimization and Applications》2013,56(2):457-480
In this paper, we investigate the use of low-discrepancy sequences to generate an initial population for population-based optimization algorithms. Previous studies have found that low-discrepancy sequences generally improve the performance of a population-based optimization algorithm. However, these studies generally have some major drawbacks like using a small set of biased problems and ignoring the use of non-parametric statistical tests. To address these shortcomings, we have used 19 functions (5 of them quasi-real-world problems), two popular low-discrepancy sequences and two well-known population-based optimization methods. According to our results, there is no evidence that using low-discrepancy sequences improves the performance of population-based search methods. 相似文献
138.
Bilinear tensor least squares problems occur in applications such as Hammerstein system identification and social network analysis. A linearly constrained problem of medium size is considered, and nonlinear least squares solvers of Gauss–Newton‐type are applied to numerically solve it. The problem is separable, and the variable projection method can be used. Perturbation theory is presented and used to motivate the choice of constraint. Numerical experiments with Hammerstein models and random tensors are performed, comparing the different methods and showing that a variable projection method performs best. 相似文献
139.
Rahul K. Shukla Akshay M. Nair Salman Khan Prof. Chandra M. R. Volla 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(39):17190-17196
An efficient Cp*CoIII-catalyzed C8-dienylation of quinoline-N-oxides was achieved by employing allenes bearing leaving groups at the α-position as the dienylating agents. The reaction proceeds by CoIII-catalyzed C−H activation of quinoline-N-oxides and regioselective migratory insertion of the allene followed by a β-oxy elimination, leading to overall dienylation. Site-selective C−H activation was achieved with excellent selectivity under mild reaction conditions, and 30 mol % of a NaF additive was found to be crucial for the efficient dienylation. The methodology features high stereoselectivity, mild reaction conditions, and good functional-group tolerance. C8-alkenylation of quinoline-N-oxides was achieved in the case of allenes devoid of leaving groups as coupling partners. Furthermore, gram-scale preparation and preliminary mechanistic experiments were carried out to gain insights into the reaction mechanism. 相似文献
140.
A novel diamine monomer, pyridine-2, 6-bis((4-aminophenyl)thioureido)carbonyl(PATC) was synthesized efficiently and polymerized with various aromatic dianhydrides. Consequently, poly(pyridine thiourea-imide)s(PPTIs) with good thermal properties and flame retardancy were fabricated. The structures of PATC and PPTIs were characterized by FTIR, 1H-NMR, 13C-NMR spectroscopy along with elemental analysis, crystallinity, organosolubility, inherent viscosity and gel permeation chromatographic measurements. PPTIs containing C=S, CONH and meta substituted pyridine moieties in the polymer backbone showed amorphous nature and were readily soluble in highly polar organic solvents and even in less polar solvents such as tetrahydrofuran(THF). Polymers had inherent viscosities in the range of 0.91-1.16 d L/g and molecular weight was found between 68000-77000 g/mol. The electrical properties of the PPTIs were estimated in terms of dielectric constant over a range of frequencies. Their thermal stability was determined by 10% weight loss temperature found in the range of 519-563 °C under inert atmosphere. The glass transition temperature of the polyimides varied between 247 °C and 267 °C. The flame retardant properties of PPTIs were investigated in terms of limiting oxygen index(LOI) which was found in the range of 38.26-39.95. Introduction of thiourea in the polymer backbone is an effective way to improve the thermal stability and flame retardancy. Thus PATC can be considered as an excellent candidate for the synthesis of high performance polymers. 相似文献