Overview of DWDM/ODC Project

This article introduces the main achievements resulting from the DWDM/ODC project. The five areas of research activity within the DWDM/ODC project cover some of the main issues of design and development of dense wavelength division multiplexing systems for transparent optical networks. These issues are: performance assessment with arbitrary optical filtering; performance of signaling formats; dispersion compensation strategies for directly and externally modulated systems in presence of nonlinear transmission-induced degradation; and the impact of noise and crosstalk in the extent of transparent optical networks. All five areas of research activity have contributed significantly to a better understanding of the limitations present in dense wavelength division multiplexing systems.     

Molecular associations of 5-membered benzofused heterocyclic donors with organic acceptors

Benzofused heterocycles like 10H-[1]benzo thieno[3,2-b] indole and thieno[3,2-b]benzo[b]thiophene form molecular associations with ^* organic acceptors. The weak interactions involved are viewed in terms of UV-Vis and IR techniques. The results, mainly in the case of complexes of 10H-[1]benzo thieno[3,2-b] indole, are in some disagreement with the literature. The structure of the complex 10H-[1]benzo thieno[3,2-b] indole/tetracyanoethylene is also reported. The four condensed rings constitute a conjugate system with significant lengthenings of the aromatic ring bonds and a shortening of those of the five-membered rings. The fragment as a whole is almost planar, and forms a dihedral angle of 39.9(1)° with the planar tetracyanoethylene molecule.     

A one-step solvothermal route for the synthesis of nanocrystalline anatase TiO2 doped with lanthanide ions

A one-step solvothermal synthesis is proposed for the preparation of nanocrystalline single-phase TiO₂ in the anatase form doped with lanthanide ions Eu³⁺, Er³⁺ and Sm³⁺. The structural properties of these products have been investigated by using X-ray powder diffraction, electron microscopy and Raman spectroscopy. Furthermore, the laser-excited luminescence spectra of the samples have been measured and analyzed. Following this route, the doping process turns out to be highly favorite and the resulting materials show an efficient luminescence in the visible region.     

C—H⋯π and π–π interactions in the supramolecular structure of 3‐methyl‐1,4‐diphenyl‐1H‐pyrazolo[3,4‐b]pyridine

The supramolecular structure of the title compound, C₁₉H₁₅N₃, is defined by π–π‐stacking and C—H?π interactions. There are no conventional hydrogen bonds in the structure.     

Supramolecular structures of 5‐[3‐(4‐methyl­phenyl)‐ and 5‐[3‐(4‐chloro­phenyl)‐2‐propenyl­idene]‐2,2‐di­methyl‐1,3‐dioxane‐4,6‐dione

2,2‐Di­methyl‐5‐[3‐(4‐methyl­phenyl)‐2‐propenyl­idene]‐1,3‐di­ox­ane‐4,6‐dione, C₁₆H₁₆O₄, crystallizes in the triclinic space group , with two mol­ecules in the asymmetric unit. These mol­ecules and a centrosymmetrically related pair, linked together by weak C—H?O hydrogen bonds, form a tetramer. 5‐[3‐(4‐Chloro­phenyl)‐2‐propenyl­idene]‐2,2‐di­methyl‐1,3‐dioxane‐4,6‐dione, C₁₅H₁₃ClO₄, also crystallizes in the triclinic space group , with one mol­ecule in the asymmetric unit. Centrosymmetrically related mol­ecules are linked together by weak C—H?O hydrogen bonds to form dimers which are further linked by yet another pair of centrosymmetrically related C—H?O hydrogen bonds to form a tube which runs parallel to the a axis.     

Lanthanide(III) Complexes with Pyridine Head Macrocyclic Ligands

The ability of lanthanide(III) ions to form stable complexeswith three different macrocyclic ligands, L¹ , L² and L³ , has been investigated.The Schiff base macrocycle L¹ and its corresponding reduced ligand L² arederived from 2,6-bis(2-formylphenoxymethyl)pyridine and diethylentriamine;the reduced ligand L³ is derived from 2,6-diformylpyridine and N,N-bis(3-aminopropyl)methylamine. Lanthanide nitrate complexes of L¹ and L² have beenprepared by direct reaction between each ligand and the appropriate hydrated lanthanidenitrate; attempts to obtain the corresponding perchlorate complexes have been unsuccessful.All nitrate complexes of L¹ give the expected [1:1, Ln:L¹ ] stoichiometry; however, complexes obtained with L² show a [2:1, Ln:L² ] stoichiometry. Finally, complexation reactions with L³ have been carried out in order to investigatethe coordination capability of this small and flexible ligand towards the Ln(III) ions.     

Synthesis of 6‐(2‐hydroxybenzoyl)pyrazolo[1,5‐a]pyrimidines by reaction of 5‐amino‐1h‐pyrazoles and 3‐formylchromone

Reaction of 3‐formylchromone ( 1 ) with 5‐amino‐1H‐pyrazoles ( 2 ) in ethanol, afforded 6‐(2‐hydroxy‐benzoyl)pyrazolo[1,5‐a]pyrimidines ( 3a‐g ) in good yields. The structures and the regiospecificity of the reaction were established by nmr measurements and X‐ray analysis, in which soft intermolecular hydrogen‐bonded networks were found.     

Benzene hydrogenation on nickel/honeycomb catalysts

Monolithic supported nickel catalysts were investigated in benzene hydrogenation between 100 and 280 °C. The conversion of benzene to cyclohexane reaches a maximum around 210 °C with a maximum yield at a ratio p^oH₂/p^oBz=3. The experimental results and some kinetic aspects are discussed.

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100 280 °C. 210 °C p^oH₂/p^oB=3. .

     

A calix(4)arene pyridine derivative and its monomeric component: structural and thermodynamic aspects of their complexation with metal cations

The interaction of a calix(4)arene derivative, namely 5,11,17,23-tetra-tert-butyl-25,26,27,28-tetra[2-(4-pyridyl)methoxy]calix(4)arene, 1a, and its monomeric component, p-tert-butylphenoxy-4-pyridine, 1b, with metal cations has been investigated in acetonitrile and methanol. (1)H NMR measurements carried out in CD(3)CN show the primary role played by the pyridyl nitrogens in their complexation with metal cations. Conductance measurements demonstrated that for all cations (except mercury) the composition of the metal ion complexes of 1a is 1:1 (ligand:metal cation). However, 1a hosts two mercury cations per unit of ligand. For the monomer 1b, complexes of 2:1 (ligand:metal cation) stoichiometries are formed with the exception of Pb(2+) (1:1 composition). The thermodynamics of complexation of these systems are reported in acetonitrile. Data in methanol are limited to stability constant values for mercury(II) and these ligands. This paper demonstrates for the first time that thermodynamic data for the complexation of the monomeric component of the ligand and metal cations contribute significantly to the interpretation of systems involving cation-calixarene interactions in solution.     

The mechanism of neutral amino acid decomposition in the gas phase. The elimination kinetics of N,N‐dimethylglycine ethyl ester,ethyl 1‐piperidineacetate,and N,N‐dimethylglycine

The gas‐phase elimination kinetics of the ethyl ester of two α‐amino acid type of molecules have been determined over the temperature range of 360–430°C and pressure range of 26–86 Torr. The reactions, in a static reaction system, are homogeneous and unimolecular and obey a first‐order rate law. The rate coefficients are given by the following equations. For N,N‐dimethylglycine ethyl ester: log k₁(s^?1) = (13.01 ± 3.70) ? (202.3 ± 0.3)kJ mol^?1 (2.303 RT)^?1 For ethyl 1‐piperidineacetate: log k₁(s^?1) = (12.91 ± 0.31) ? (204.4 ± 0.1)kJ mol^?1 (2.303 RT)^?1 The decompositon of these esters leads to the formation of the corresponding α‐amino acid type of compound and ethylene. However, the amino acid intermediate, under the condition of the experiments, undergoes an extremely rapid decarboxylation process. Attempts to pyrolyze pure N,N‐dimethylglycine, which is the intermediate of dimethylglycine ethyl ester pyrolysis, was possible at only two temperatures, 300 and 310°C. The products are trimethylamine and CO₂. Assuming log A = 13.0 for a five‐centered cyclic transition‐state type of mechanism in gas‐phase reactions, it gives the following expression: log k₁(s^?1) = (13.0) ? (176.6)kJ mol^?1 (2.303 RT)^?1. The mechanism of these α‐amino acids differs from the decarbonylation elimination of 2‐substituted halo, hydroxy, alkoxy, phenoxy, and acetoxy carboxylic acids in the gas phase. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33:465–471, 2001