Copper(II) and nickel(II) complexes of N,N′-bis(2-cyanoethyl)-5, 7-dioxo-1,4,8,11-tetra-azacyclotetradecane

Summary Reaction of 5,7-dioxo-1,4,8,11-tetra-azacyclotetradecane with acrylonitrile gives the dicyanoethylated ligand (L). The Cu^II complex [CuLH_-2]·2H₂O has been isolated from basic solution where the macrocycle is deprotonated and acts as a dinegative quadridentate ligand. The ligand L is protonated in acidic solution and the ionisation equilibria can be summarised as LH _inf2 ^sup2+ LH⁺ +H⁺; K₁ LH⁺ L + H⁺; K₂ where pK₁ = 3.05 and pK₂ = 5.94 at 25 °C and I = 0.1 mol dm^-3 (NaNO₃). Complexation with Cu^II can be represented by the equilibria at 25 °C. Cu²⁺ + L [CuLH_-1]⁺ + H⁺; log_{11 – 1} = -3.43 Cu²⁺ + L [CuLH_-2] + 2H²⁺; log_{11 – 2} = -9.18 For Ni^II only the single equilibrium is of importance. Ni²⁺ + L [NiLH_-2] + 2H²⁺; log_{11 – 2} = -14.45     

Copper(II) and nickel(II) complexes of mono-oxocyclam(5-oxo-1,4,8,11-tetraazacyclotetradecane). Synthetic and potentiometric studies

Summary The macrocyclic mono-oxotetraamine, 5-oxo-1,4,8,11-tetraazacyclotetradecane (mono-oxocyclam=LH) has been prepared by reaction of methyl acrylate with 2,3,2-tetra(1,9-diamino-3,7-diazanonane). The protonation constants of the ligand are log K₁=9.40, log K₂=6.65 and log K₃=2.87 at 25 °C (I=0.1 mol dm^–3 NaClO₄). Detailed potentiometric studies of the interaction of the base with copper(II) and nickel(II) have been carried out. In the pH range 2.5–7.0 two complexes, [CuLH]²⁺ and [CuL]⁺, form; the deprotonated complex being 100% abundant at pH 7. For nickel(II), only [NiL]⁺ forms (log _11–1 = 3.90), the yellow low spin nickel complex reaching its maximum concentration above pH 6. The [CuL][ClO₄] · H₂O and [NiL][ClO₄] 0.5 H₂O complexes have been characterised in the solid state. The nickel(II) complex is square planar with a d-d band at 22625 cm^–1.     

The coordination chemistry of macrocyclic diamides. Transition metal complexes of 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane

Summary A convenient preparation of the 14-membered macrocyclic diamide 5,7-dioxo-1,4,8,11-tetraazacyclotetradecane (LH₂) is described. The pK _NH ⁺ values of the ligand are pK₁ = 5.76 and pK₂ = 9.63 at 25° and I = 0.1 mol dm^–3 (KNO₃). With metal ions able to ionise amide hydrogens, the ligand acts as a planar quadridentate, L^2–. Thus copper(II) and nickel(II) give the neutral complexes ML, and conductivity measurements confirm that they are nonelectrolytes in aqueous solution. Both the nickel(II) and copper(II) complexes are acid labile unlike the analogues of 1,4,8,11-tetraazacyclotetradecane (cyclam).The cobalt(III) complex [CoL(NH₃)₂]Cl has been characterised and¹H n.m.r. measurements established the N-meso stereochemistry at the chiral nitrogen centres.     

Synthesis and electronic properties of alternating alpha,alpha'-thiophene-phosphole oligomers

[structure: see text] Alternating thiophene-phosphole oligomers up to seven rings in length have been synthesized. A regular decrease of the HOMO-LUMO gap is observed upon increasing the length of the pi-conjugated system. The nature of the P-moieties dramatically influences the optical and electrochemical properties of these phosphole-based oligomers. Electro-oxidation of derivative 5a afforded an electroactive polymer exhibiting reversible p-doping.     

Metal complexes of tetramethylethylenediaminetetraacetate

Summary A number of metal complexes of the ligand tetramethylethylenediaminetetraacetate [Edta(OMe)₄ = L] have been characterised. The complexes may be formulated MLCl₂ · xH₂O where M²⁺ = Mn^II, Fe^II, Co^II, Ni^II, Cu^II, Cd^II, Hg^II and Sn^II. I.r., conductivity, magnetic susceptibility and electronic spectral data are discussed.     

Oxidatively stable and highly proton conductive membrane from poly(arylene ether)s containing biphenyl moiety as pendent groups

Novel poly(arylene ether)s with sulfonic acid groups attached onto pendent biphenyl rings were successfully synthesized by the nucleophilic displacement of aromatic dihalides with bisphenols in aprotic solvent in the present of excess potassium carbonate, followed by sulfonation with chlorosulfonic acid. The sulfonation took place only on the pendent biphenyl rings due to the specially designed molecular structure. The sulfonated polymers were very soluble in common organic solvents, such as dimethyl sulfoxide, N,N′-dimethylacetamide, dimethylformamide, and can be readily cast into tough and smooth films. These membranes showed excellent stabilities resistance to both oxidation and hydrolysis, as evidenced by subjecting to both Fenton's reagent test and immersion in boiling water. The proton conductivities (3.2 × 10⁻³ S cm⁻¹) of the as-made membranes were higher than that of Nafion^® 117 (1.9 × 10⁻³ S cm⁻¹) under same conditions. The satisfied properties of these new polymers demonstrated them as promising candidates for proton exchange membrane in PEM fuel cell applications.     

Structural design criteria for anion hosts: strategies for achieving anion shape recognition through the complementary placement of urea donor groups

The arrangement of urea ligands about different shaped anions has been evaluated with electronic structure calculations. Geometries and binding energies are reported for urea complexes with Cl-, NO(3)-, and ClO(4)-. The results yield new insight into the nature of urea-anion interactions and provide structural criteria for the deliberate design of anion selective receptors containing two or more urea donor groups.     

Temperature drop turbidity. IV. Polystyrene

The molecular weight distribution of fractionated and unfractionated polystyrene samples has been determined by temperature drop turbidimetry, in which polymer is precipitated from dilute solutions in cyclohexanol by progressively cooling from 388 to 310 K. Estimates of the molecular weight averages and the polydispersities, obtained by calibration of the temperature of initial onset of precipitation, T_i, and the weight-average molecular weight were low, but could be substantially improved by correcting for concentration changes during precipitation. An empirical procedure correlating the breadth of turbidity-temperature curves to the logarithm of the polydispersity, as measured by gel permeation chromatography, appeared to be a simpler method of characterizing the polymer samples and as accurate as the computational methods above.     

On the use of sensitivity analysis in model reduction to predict flows for varying inflow conditions

The proper orthogonal decomposition (POD)‐based model reduction method is more and more successfully used in fluid flows. However, the main drawback of this methodology rests in the robustness of these reduced order models (ROMs) beyond the reference at which POD modes have been derived. Any variation in the flow or shape parameters within the ROM fails to predict the correct dynamics of the flow field. To broaden the spectrum of these models, the POD modes should have the global characteristics of the flow field over which the predictions are required. Mixing of snapshots with varying parameters is one way to improve the global nature of the modes but is computationally demanding because it requires full‐order solutions for a number of parameter values in order to assemble atextitrich enough database on which to perform POD. Instead, we have used sensitivity analysis (SA) to include the flow and shape parameters influence during the basis selection process to develop more robust ROMs for varying viscosity (Reynolds number), changing orientation and shape definition of bodies. This study aims at extending these ideas to inflow conditions to demonstrate the effectiveness of the proposed approach in capturing the effect of varying inflow on the dynamics of the flow over an elliptic cylinder. Numerical experiments show that the newly derived models allow for a more accurate representation of the flows when exploring the parameter space. Copyright © 2011 John Wiley & Sons, Ltd.