Highly Efficient One‐Pot Preparation of 1,2,4‐Oxadiazoles in the Presence of Diazabicycloundecene

New highly efficient method for the cyclization of acylamidoximes in the presence of diazabicycloundecene was developed and incorporated into a general and practical one‐pot synthesis of 1,2,4‐oxadiazoles (11 examples, 85–97% yields).     

Dimethylaminoalkyl chalcogenolate palladium(II) complexes as an efficient copper- and phosphine-free catalyst for Sonogashira reaction

N,N-Dimethylaminoalkyl chalcogenolate Pd(II) complexes [PdCl(E^∩NMe₂)]_n has been investigated as a moisture/air-stable and robust catalyst for Sonogashira cross-coupling reaction in the absence of copper and phosphine ligand. The dimeric palladium(II) complex of selenium containing ligand shows the best catalytic activity as compared with monomeric and trimeric complexes. The variety of functional groups are tolerated under optimized catalytic systems and provide excellent yields of the products.     

MAS-NMR study of lithium zinc silicate glasses and glass-ceramics with various ZnO content

Lithium zinc silicate glasses of composition (mol%): 17.5Li₂O-(72−x)SiO₂-xZnO−5.1Na₂O−1.3P₂O₅−4.1B₂O₃, 5.5?x?17.7, were prepared by conventional melt-quenched technique and converted to glass-ceramic by controlled crystallization process. ²⁹Si and ³¹P MAS-NMR was used to characterize the structure of both glass and glass-ceramic samples. Despite the complex glass composition, Q², Q³ and Q⁴ sites are identified from ²⁹Si MAS-NMR, which relative intensities are found to vary with the ZnO content, indicating a network depolymerization by ZnO. Moreover, well separated Q³ and Q⁴ resonances for low ZnO content indicates the occurrence of phase separation. From ³¹P MAS-NMR, it is seen that phosphorus is mainly present in the form of ortho-(Q⁰) and pyro-phosphate (Q¹) structural units and variation of ZnO content did not have much effect on these resonances, which provides an additional evidence for phase separation in the glass. On conversion to glass-ceramics, lithium disilicate (Li₂Si₂O₅), lithium zinc ortho-silicate (Li₃Zn_0.5SiO₄), tridymite (SiO₂) and cristobalite (SiO₂) were identified as major silicate crystalline phases. Using ²⁹Si MAS-NMR, quantification of these silicate crystalline phases is carried out and correlated with the ZnO content in the glass-ceramics samples. In addition, ³¹P spectra unambiguously revealed the presence of crystalline Li₃PO₄ and (Na,Li)₃PO₄ in the glass-ceramics.     

Multinuclear complexes containing [Pt2(μ-S)2(Ptolyl3)4] as a metallo-ligand

Treatment of [PtCl₂(Ptolyl₃)₂] (tolyl = 4-MeC₆H₄) with Na₂S in benzene gave [Pt₂(μ₂-S)₂(Ptolyl₃)₄] (1), which is soluble in common organic solvents. Reactions of (1) with various metal complexes have been studied and several polynuclear metal aggregates isolated. These new complexes were characterized by elemental analysis and n.m.r. spectroscopy. This revised version was published online in June 2006 with corrections to the Cover Date.     

LMI approach to the global robust stability of a larger class of neural networks with delay

Sufficient conditions in the form of linear matrix inequality for the uniqueness and global asymptotic stability of the equilibrium point of a large class of uncertain neural networks with delay are presented. The conditions are based on norm-bounded uncertainties. An example is given to show the effectiveness of the obtained results. A comparison is made between the present approach and an earlier approach due to Lu, Rong and Chen. An error is corrected in an earlier publication.     

Modified criteria for global robust stability of interval delayed neural networks

Two simple criteria for global robust stability of Hopfield-type interval neural networks with delay are presented. The criteria turn out to be modified versions of an earlier criterion due to Cao, Huang, and Qu. Examples show the effectiveness of the modified criteria. Numerical simulations are carried out to confirm the applicability of the modified criteria.     

Photoinduced Intramolecular Electron Transfer and Electronic Coupling Interactions in π- Expanded Imidazole Derivatives

An intramolecular excited charge transfer (CT) analysis of imidazole derivatives has been made. The determined electronic transition dipole moments has been used to estimate the electronic coupling interactions between the excited charge transfer singlet state (¹CT) and the ground state (S₀) or the locally excited state (¹LE). The properties of excited ¹CT state imidazole derivatives have been exploited by the significant contribution of the electronic coupling interactions. The excited state intramolecular proton transfer (ESIPT) analysis has also been discussed.     

Setting sensitivity in Talbot interferometry with modified gratings

A dual field grating has been introduced for use in Talbot interferometry. We report here results of an experimental investigation on setting sensitivity when using these gratings for testing.     

Three-beam heterodyne interferometer

The heterodyne technique has been applied to three-beam interference, and three interferometer arrangements are discussed. These arrangements are suitable for electronic measurement of optical phase. A three-beam heterodyne interferometer is demonstrated.