Inclusion Complexation of Carbaryl and β-Cyclodextrin in Solution and in the Solid State

This study was carried out with the aim ofinvestigating the interactions between-cyclodextrin and carbaryl, a carbamatepesticide, and their effect on some physico-chemicalproperties of carbaryl, such as aqueous solubility andlipophilicity. The interactions between carbaryl and-cyclodextrin were thoroughly investigated bothin solution and in the solid state. The effect of-cyclodextrin on the aqueous solubility ofcarbaryl was evaluated by the phase solubility method.The amount of carbaryl dissolved increased linearlywith the addition of -cyclodextrin according toan A_L type plot and without precipitation of thecomplex. The apparent stability constant of thecomplex was 289 ± 21 M^-1, assuming a 1 : 1stoichiometry; this value was confirmed by a methodbased on circular dichroism measurements.Equimolar carbaryl/-cyclodextrin solid systemswere prepared by physical-mixing and freeze-drying,and fully characterised by Differential ScanningCalorimetry, X-ray powder diffractometry and FourierTransform Infra-Red analysis. The results of the solidstate study demonstrated that the freeze-drying methodyields a system with a high degree of amorphisationand yields an inclusion complex.The dissolution profile of the pesticide was affectedby the physico-chemical properties of each solidsystem, the freeze-dried form dissolving more rapidly. However, the physical association of-cyclodextrin and carbaryl enhanced the aqueoussolubility of the insecticide as well.     

Application of special reduction procedures to metrological data

To improve the reduction of metrological data, that are typically grouped in series and cannot be considered as replicated data, a modelling procedure has been obtained by adding to the model representing the physical behaviour, common to all data, a specific term for each series. Such a procedure combines both the advantages of preserving the individuality of each series and of improving the variance estimate which arises from fitting the overall data. A non-parametric bootstrap method for the error analysis has been developed, which does not imply the assumption of the Normal distribution in the least squares estimation. Two examples of application of the method to thermodynamic data series are reported.     

Coordination behavior toward copper(II) and zinc(II) ions of three ligands joining 3-hydroxy-2-pyridinone and polyaza fragments

The synthesis and characterization of new polydentate ligand 2-(N),2'-(N')-bis[2-(3-hydroxy-2-oxo-2H-pyridin-1-yl)acetamido]-1(N'),2(N),2'(N')-trimethyl-2,2'-diaminodiethylamine (L3) is reported. The coordination properties of L3 and of two analogous macrocyclic ligands (L1 and L2) toward Cu(II) and Zn(II) metal ions are reported. All three ligands show the 3-hydroxy-2(1H)-pyridinone (HPO) groups attached as sidearms to a polyaza fragment, which is a macrocyclic framework in the case of L1 and L2 while it is an open chain in the case of L3. The role of the polyaza fragments in preorganizing the two sidearms was investigated. The basicity of L3 and the binding properties of L1-L3 were determined by means of potentiometric measurements in aqueous solution (298.1 +/- 0.1 K, I = 0.15 mol dm(-3)). UV-vis spectra as well 1H and 13C NMR experiments were used to understand the role of the HPO and of the polyaza fragments in the stabilization of the cations. While L1 forms stable mono- and dinuclear complexes, L2 and L3 can form only mononuclear species with each of the metal ions investigated. In the main mononuclear species of L2 and L3, the two HPO moieties stabilize the M(II) in a square planar geometry due to the two oxygen atoms of each HPO. The coordination sphere of the metal is completed by adding a secondary ligand such as water molecules in the case of Cu(II) systems or OH- in the Zn(II) systems. These results are confirmed by the crystal structures of the [CuH(-1)L2]+ and [CuH(-1)L3]+ species reported herein. Two conformations of L1 can be hypothesized in the formation of the dinuclear species, as suggested by NMR experiments on the [ZnH(-2)L1] species, which shows two conformers slowly interchanging on the NMR time scale, one of which was found to be more insoluble.     

Steric and electronic tuning of chiral bis(oxazoline) ligands with 3,3'-bithiophene backbone

[structure: see text] The role played by the electronic properties and the steric features of bis(oxazoline) ligands in the Cu(I)-catalyzed cyclopropanation of styrene effected with ethyl diazoacetate was investigated. Two pairs of new bis(oxazolines) displaying flexible and atropisomeric 3,3'-bithiophene backbones were synthesized and structurally and electronically characterized. For the first time, the electrochemical oxidative potential was used as a reliable index of the electronic density on the nitrogen atom of the chelating groups of new and, for comparative purposes, of already known bis(oxazolines). The Cu(I) complexes of the new ligands were prepared, and their enantioselection ability and catalytic efficiency were tested. This investigation suggests that steric factors and catalyst geometrical features are clearly more important than any consideration of the electronic properties of the chiral ligands.     

Pyrrolo[3,2-c][1,2,5]benzotriazocine: A new ring system

A nucleophilic substitution reaction in the pyrrole series, achieved by a neutral nucleophile, led to the key intermediate 7 which by reduction and successive diazotization afforded the new ring system pyrrolo[3,2-c][1,2,5]benzotriazocine 9 in good yield.     

Local asymptotic stability for dissipative wave systems

We study the question of asymptotic stability, as time tends to infinity, of solutions of dissipative wave systems, governed by time-dependent nonlinear damping forces and by strongly nonlinear potential energies. This problem had been considered earlier for potential energies which arise from restoring forces, whereas here we allow as well for the effect of amplifying forces. Global asymptotic stability can then no longer be expected, and should be replaced by local stability. The conclusions are related to and supplement earlier work of Payne and Sattinger [7], who treated the nondissipative case, and of Hale [1], who showed the existence of connected global attractors.     

2‐Diazo‐2H‐indoles

2‐Diazo‐2H‐indoles were prepared by diazotization of the corresponding 1H‐indol‐2‐amines and subsequent neutralization. On the basis of NMR data and ab initio and semiempirical calculations, we suggest that the zwitterionic form A is the most representative structure for 2‐diazo‐2H‐indoles. In fact, spectral data are compatible with a 1H‐indole structure, and the fully optimized molecules gave distances in agreement with those reported for the anion obtained from 1H‐indole. The calculated charges are compatible with a zwitterionic structure in which the negative charge is mainly located at the ring N‐atom at variance with the case of diazopyrroles and 3‐diazo‐3H‐indoles where the negative charge is essentially located on the ipso C‐atom.     

Sol-Gel Preparation and Characterization of Ag-TiO2 Nanocomposite Thin Films

Ag-TiO₂ thin films were prepared with a sol-gel route, using titanium isopropoxide and silver nitrate as precursors, at 0.03 and 0.06 Ag/Ti nominal atomic ratios. After drying at 80°C, the films were fired at 300°C and 500°C for 30 min. The films were analysed by X-ray diffraction (XRD) with glancing angle, and X-ray photoelectron spectroscopy (XPS), with depth profiling of the concentration. XPS analysis showed the presence of C and N as impurities in the nanocomposite films. Their concentration decreased with increasing the firing temperature. Chemical state analysis showed that Ag was present in metallic state, except for the very outer layer where it was present as Ag⁺. For the films prepared with a Ag/Ti concentration of 0.06, depth profiling measurements of the film fired at 300°C showed a strong Ag enrichment at the outer surface, while composition remained almost constant within the rest of the film, at 0.019. For the films heated to 500°C, two layers were found, where the Ag/Ti ratios were 0.015 near the surface and 0.026 near the substrate.