Synthesis,Characterization, Luminescence,and Electrochemistry of the Tetranuclear Gold(I) Amidinate Clusters,Precursors to CO Oxidation Catalysts: Au4[(ArNC(H)NAr)]4, Au4[(PhNC(Ph)NPh)]4 and Au4[PhNC(CH3)NPh)4]

A summary of the chemistry of the tetranuclear Au(I) amidinate complexes is presented. Tetranuclear Au(I) amidinate clusters are produced by the reaction of the sodium salt of a amidine ligand with the gold precursor Au(THT)Cl in a (1:1) stoichiometry. The structures of the tetranuclear Au₄[ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, C₆H₃‐3,5‐Cl, C₆H₄‐4‐Me, C₆H₄‐3‐CF₃, C₆F₅, C₁₀H₇ and the tetranuclear Au₄[(PhNC(Ph)NPh]₄ and Au₄[PhNC(CH₃)NPh]₄ have been characterized by X‐ray crystallography. The average Au···Au distance between adjacent Au(I) atoms is ?3.0 Å, typical of compounds having an aurophilic interaction. The four gold atoms are located at the corner of a rhomboid with the amidinate ligands bridged above and below the near plane of the four Au(I) atoms. The angles at Au···Au···Au in the cyclic units are between 70° and 116°. The tetranuclear gold(I) amidinate clusters each show different luminescence behavior. The tetranuclear clusters Au₄[(ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, Ar = C₆H₄‐3‐CF₃, Ar = C₆H₄‐4‐Me and Ar = C₆H₄‐3,5‐Cl are the first tetranuclear gold(I) cluster species from group 11 elements that show fluorescence at room temperature. The tetranuclear naphthyl derivative Ar = C₁₀H₇ is luminescent only at 77 K. The pentafluorophenyl derivative Ar = C₆F₅ does not show any photoluminescence in the solid state nor in the solution. The lifetimes of the naphthyl and trifluoromethylphenyl complexes are in the millisecond range indicating phosphorescent processes. Electrochemical and chemical oxidation studies of the tetranuclear Au(I) amidinate clusters are presented. The tetranuclear complexes Au₄[ArNC(H)NAr]₄, Ar = C₆H₄‐4‐OMe, Ar = C₆H₄‐4‐Me, and Ar = C₆H₃‐3,5‐Cl, show three reversible waves at 0.75, 0.95, 1.09 V vs. Ag/AgCl at a scan rate of 500 mV/s in 0.1 M Bu₄NPF₆/CH₂Cl₂ at a Pt working electrode in CH₂Cl₂. Three reversible waves at 0.87, 1.19, 1.42 V vs. Ag/AgCl at a scan rate of 100 mV/s are also observed for the tetranuclear complex Au₄[PhNC(Ph)NPh]₄ in CH₂Cl₂. The pentafluorophenyl amidinate derivative, Au₄[ArNC(H)NAr]₄, Ar = C₆F₅ shows no oxidation wave below 1.8 V. Recently it has been shown that Au₄[ArNC(H)NAr]₄ is a very effective catalyst precursor for room temperature CO oxidation.     

Spectroscopic studies on some phenylethylamine drugs: Molecular orbital calculations

The electronic absorption spectra of some phenylethylamine drugs, namely, d-pseudoepherine, l-pseudoephedrine, l-ephedrine, dl-ephedrine dl-norephedrine, phenylethylamine, methoxyphenamine, and l-noradrenaline were investigated in polar and nonpolar solvents. The observed transitions were interpreted, and the role of σ-π interaction was explored. Molecular orbital calculations were performed on representatives of the above group of compounds, namely, d-pseudoephedrine, l-ephedrine, and l-noradrenaline using the INDO procedures and adopting the best conformer of the molecule. The transition energy, band intensity, and dipole moments were calculated and corresponded satisfactorily with the experimental values.     

New solitons and periodic wave solutions for nonlinear physical models

In this paper, an extended tanh method with computerized symbolic computation is used for constructing the traveling wave solutions of coupled nonlinear equations arising in physics. The obtained solutions include solitons, kinks, and plane periodic solutions. The applied method will be used in further works to establish more entirely new solutions for other kinds of nonlinear evolution equations arising in physics.     

New copper(II) complexes produced by the template reaction of acetoacetic-2-pyridylamide and amino-aliphatic alcohols

The template condensation of acetoacetic-2-pyridylamide with amino aliphatic alcohols such as 2-aminoethanol (HL1) and 3-amino propanol (HL2) in the presence of copper(II) ions gave octahedral complexes, which have been characterized by elemental analyses, u.v.-vis. and i.r. spectra, conductivity, d.t.a, magnetic and e.s.r. measurements. The molar conductance in DMF indicate that the complexes are non-ionic in character. The e.s.r. spectra of solid complexes (2) and (5) at room temperature indicate axial type symmetry (dx2-y2) with covalent bond character.     

Reaction with hydrazonoyl halides XXIII [1]: Synthesis and reactions of C‐coumarinoyl‐N‐arylformohydrazonoyl bromides

C‐Coumarinoyl‐N‐arylformohydrazonoyl bromides ( 3 ) were synthesized by reaction of N‐nitrosoarylacetamides with an appropriate sulfonium bromide in ethanol at room temperature. The reactions of potassium thiocyanate, potassium selenocyanate, thiourea, methyl phenylthiocarbomate, and methyl phenylhydrazinedithioate with hydrazonoyl bromide 3a were examined. © 1999 John Wiley & Sons, Inc. Heteroatom Chem 10: 355–362, 1999     

Non-Gravitational Effects with Density-Matching in Evaluating the Influence of Sedimentation on Colloidal Coagulation

The method of density matching between the solid and liquid phases is often adopted to effectively eliminate the effect of sedimentation of suspensions in studies on dynamic behaviour of a colloidal system. However, the associated changes in the solvent composition may bring side effects to the properties investigated and therefore might lead to a faulty conclusion if the relevant correction is not made. To illustrate the importance of this side effect, we present an example of the sedimentation influence on the coagulation rate of suspensions of 2μm （diameter） polystyrene. The liquid mixtures, in the proper proportions of water （H2O）, deuterium oxide （D2O） and methanol （MeOH） as the liquid phase, density-matched and unmatched experiments are performed. Besides the influence of viscosity, the presence of methanol in solvent media, used to enhance the sedimentation effect, causes significant changes （reduction） in rapid coagulation rates compared to that in pure water. Without the relevant corrections for those non-gravitational factors it seems that gravitational sedimentation would retard the coagulation. The magnitude of the contribution from the non-gravitational factor is quantitatively determined, making the relevant correction possible. After necessary the influence of the sedimentation on coagulation rates at corrections for all factors, our experiments show that the initial stage of the coagulation is not observable.     

Utility of 2-(5-methyl-1-phenyl-1H-pyrazol-4-yl)-2-oxo-N′-phenylaceto-hydrazonoyl bromide as precursor for synthesis of new functionalized heterocycles

2-(5-Methyl-1-phenyl-1H-pyrazol-4-yl)-2-oxo-N′-phenylaceto-hydrazonoyl bromide was synthesized and used as precursor for synthesis of some new 1,3,4-thiadiazoles, pyrrolo[3,4-c]pyrazoles, and 1,2,4-triazolo[4,3-a]pyrimidines. The mechanisms that account for formation of products were discussed. Also, the structures of all the newly synthesized products were confirmed based on elemental analysis, spectral data and by alternative methods.