Hexanuclear copper(II) cages built on a central {μ3-O···H···μ3-O} moiety, 1,3-bis(dimethylamino)-2-propanolato and capping R-phosphonates: crystal structures, magnetic behavior, and DFT studies

The syntheses, structural characterization, and magnetic behavior of two new hexanuclear copper(II) complexes derived from R-phosphonic acids and 1,3-bis(dimethylamino)-2-propanol (Hbdmap) with formulas [Cu(6)(μ-bdmap)(3)(μ(3)-Ph-PO(3))(2)(μ(3)-O···H···μ(3)-O)(ClO(4))(2)(H(2)O)]·5H(2)O (1) and [Cu(6)(μ-bdmap)(3)(μ(3)-t-Bu-PO(3))(2)(μ(3)-O···H···μ(3)-O)(μ(1,3)-dca)(dca)(H(2)O)]·6H(2)O (2) (Ph-H(2)PO(3) = phenylphosphonic acid, t-Bu-H(2)PO(3) = tert-butylphosphonic acid, dca = dicyanamide) are reported. Compounds 1 and 2 are hexanuclear 3.111 R-phosphonate(2-)/1,3-bis(dimethylamino)-2-propanolato(1-) cages including in the center the [μ(3)-O···H···μ(3)-O](3-) unit. The temperature dependence of the magnetic properties of 1 and 2 clearly indicates an overall strong antiferromagnetic coupling confirmed by DFT calculations.     

Effect of 165-keV Ar-ion irradiation on microstructural and mechanical properties of zircaloy-4

Journal of Radioanalytical and Nuclear Chemistry - Cold-worked zircaloy-4 was irradiated by 165 keV Ar ion at room temperature. The aim of the study is to understand the correlation...     

Reforming of Rice Ash Waste by Incorporated Nanotitania in Silica Framework for Photo-catalytic Treatment of Wastewater

The nano-composites based on the burnt rice straw waste, reformed by nano-TiO₂ and copper phthalocyanine (CuPc), namely, RSA-TiO₂, RSA-CuPc, and RSA-TiO₂-CuPc were prepared by a mechano-chemical method. The as-prepared composite systems were characterized by adopting FE-SEM, TEM, XRD, FTIR, SBET, and optical techniques. Their photo-catalytic performance in the degradation of methylene blue dye was evaluated under visible light irradiation. The co-existence of the two components in RSA, SiO₂ and organic carbon, plus the inherently intimate contact between nano-TiO₂ and CuPc could improve the photo-degradation of MB dye. The complete degradation of MB dye was achieved by using RSA-TiO₂ (50) nano-composite and the time is taken for 50% degradation of a dye is 53 min under visible light radiation. The kinetic study revealed that photo-degradation of MB follows a pseudo-first-order reaction mechanism, where the kinetic rate constant was 0.013 min⁻¹.     

Optimal procedures for the discrete time/cost trade-off problem in project networks

We describe two algorithms, based on dynamic programming logic, for optimally solving the discrete time/cost trade-off problem (DTCTP) in deterministic activity-on-arc networks of the CPM type, where the duration of each activity is a discrete, nonincreasing function of the amount of a single nonrenewable resource committed to it. The first algorithm is based on a procedure proposed by Bein, Kamburowski and Stallmann for finding the minimal number of reductions necessary to transform a general network to a series-parallel network. The second algorithm minimizes the estimated number of possibilities that need to be considered during the solution procedure. Both procedures have been programmed in C and tested on a large set of representative networks to give a good indication of their performance, and indicate the circumstances in which either algorithm performs best.     

Excess enthalpies of binary mixtures of n-octane with each of the hexane isomers at 298.15 K

Excess molar enthalpies, measured at 298.15 K in a flow microcalorimeter, are reported for the five binary systems formed by mixing n-octane with n-hexane, 2-methylpentane, 3-methylpentane, 2,2-dimethylbutane and 2,3-dimethylbutane. The results for equimolar mixtures, together with similar data for other n-alkane + hexane isomer mixtures, are correlated in terms of the acentric factors of the n-alkanes.     

Crystal growth and characterisation of new organic nonlinear optical materials: 6-cyano and 6-nitro-2,2-dimethyl-3,4-epoxychroman

Two chiral organic nonlinear optical materials, (3S,4S)-(−)-6-cyano-2,2-dimethyl-3,4-epoxychroman (1) and (3R,4R)-(+)-6-nitro-2,2-dimethyl-3,4-epoxychroman (2), have been grown into single crystals of cm³-size. Although both compounds crystallise in the orthorhombic P2₁2₁2₁ space group, they are not isomorphous and their crystal packings are quite different. Angle tuned type II phase-matched second harmonic generation between 0.8 and 1.064 μm has been evidenced, with effective nonlinear coefficients d_eff of 1 and 5 pm/V at 0.96 μm for 1 and 2, respectively. These values are in agreement with those estimated in the oriented gas model approximation using EFISH first order hyperpolarisability values (β₀=2.6 and 4.0×10⁻³⁰ esu for 1 and 2, respectively).     

Kinetics of aquation of chloropentamminecobalt(III) perchlorate in ethylene glycol-water media

Summary The aquation of chloropentamminecobalt(III) ion has been studied in ethylene glycol-water mixtures up to 80% by weight at five temperatures from 35 to 55°C. Specific solvent effects on the reaction rate and mechanism have been investigated and discussed. The validity of our previously proposed equations, correlating the specific reaction rate with the dielectric constant of the medium has been examined. The thermodynamic parameters of activation have been calculated and presented as evidence for the solvation effects and in support of the proposed reaction mechanism.     

Structural Variances in the Homologous Series of Alkaline Earth Metallated Octamethylcyclotetrasilazandiides

The magnesium, calcium, and strontium metal derivatives of 2, 2, 4, 4, 6, 6, 8, 8‐octamethylcyclotetrasilazane (OMCTS) have been synthesized and structurally characterized by X‐ray diffraction studies. These are the first complexes of the homologous series of alkaline earth metalated OMCTS. Similar to the homologous series of the corresponding alkali metal complexes, the structural properties show remarkable tendencies in the series from magnesium to strontium. The magnesium dication causes the most pronounced deformation along the transannular N^‐···N^‐ vector of the [(c‐N‐SiMe₂‐NH‐SiMe₂‐)₂]^2‐ dianionic ring. The lengths of the Si‐N bonds are correlated to the bond types, so that shorter distances result when the bonds become more ionic. The difference between the long Si‐N(H) bonds and the short Si‐N^‐ bonds decreases gradually with the increasing mass of the alkaline earth metal dication.     

Variation of Some Physical Properties of Brownmillerite Doped with a Transition Metal Oxide

Hyperfine Interactions - Cement clinker is the main component of Portland cement. It is composed of four main phases. One of them is the brownmillerite or the ferrite phase of cement clinker. It is...