Silicon containing new salicylaldimine Pd(II) and Co(II) metal complexes as efficient catalysts in transformation of carbon dioxide (CO2) to cyclic carbonates

A new series of metal complexes of salicyladimine ligands with Pd(II) and Co(II) have been prepared and characterized by different techniques (elemental analysis, UV-vis, FT-IR, ¹H NMR spectra, magnetic susceptibility measurements). Electronic spectra and magnetic susceptibility measurements reveal square planar geometry for Pd(II) metal complex and tetrahedral geometry for Co(II) metal complex. The synthesized Pd(II) and Co(II) complexes were also tested as catalysts for the formation of cyclic organic carbonates from carbon dioxide and liquid epoxides which served as both reactant and solvent. The results showed that the [M(L₃)₂] (M = Pd or Co) complexes bearing 5-methyl substituent on the aryl ring are more efficient than the other Pd(II) and Co(II) metal complexes for the formation of cyclic organic carbonates from carbon dioxide. These catalysts, [Pd(L₃)₂] and [Co(L₃)₂] complexes and location (p-position of phenoxy) of electron donating methyl substituent in particular, effectively promote the of carbon dioxide activation with liquid epoxides under solvent-free homogeneous conditions. Furthermore, [Pd(L₃)₂] can be reused more than eight times with a minimal loss of its original catalytic activities.     

Sensitivity of Schur stability of monodromy matrix

For Schur stable linear difference equation system with periodic coefficients, we prove continuity theorems on monodromy matrix which show how much change is permissible without disturbing the Schur stability, and some examples illustrating the efficiency of the theorems are given.     

On locally finite minimal non-solvable groups

In the present work we consider infinite locally finite minimal non-solvable groups, and give certain characterizations. We also define generalizations of the centralizer to establish a result relevant to infinite locally finite minimal non-solvable groups.     

Classification of qt=P(x, t, q, qx, qxx)

The classification of q_t = P ( x ,  t ,  q ,  q_x ,  q_xx ) is given by using linearization. Two types of integrable equations which are generalizations of the integrable equations of Fokas and Svinolupov are given. Results are compared with Fokas's symmetry and the Mikhailov–Shabat–Sokolov formal symmetry approaches.     

Turn-on fluorescent probe for Zn2+ ions based on thiazolidine derivative

In this study, simple on–off fluorescent/UV–visible (UV–Vis) probes were easily prepared using 2-(2-hydroxyphenyl)thiazolidine-4-carboxylic acid ( Sen-1 ) and/or 2-(2-hydroxy-5-nitrophenyl)thiazolidine-4-carboxylic acid ( Sen-2 ) for fast detection of Zn²⁺ ions. Their sensing properties towards common metal ions were investigated using UV–Vis and fluorescence spectroscopies. Sen-1 and Sen-2 displayed a significant change with the addition of Zn²⁺ ions in the UV–Vis spectra. The addition of Zn²⁺ ions induced a 104 nm bathochromic shift for Sen-1 . The binding ratio towards Zn²⁺ metal ions was determined to be 1:1 by using Job plot analysis and fluorescence spectroscopy. The association constant and free energy (ΔG) of Sen-1 and Sen-2 towards Zn²⁺ ions were calculated by the Benesi–Hildebrand equation. The limit of detection of Sen-1 towards Zn²⁺ ions is 3.73 × 10⁻⁸ M, which is about 1/100 of the value recommended by the World Health Organization for drinking water. Sen-1 was successfully applied to detect Zn²⁺ ions in water samples and the fluorescence test strip was prepared for visual detection of Zn²⁺ ions. Finally, the quantum chemical parameters of Sen-1 and Sen-2 , such as highest occupied molecular orbital, lowest unoccupied molecular orbital, and chemical hardness, were investigated by the Becke, three-parameter, Lee–Yang–Parr, Hartree–Fock, and M062x methods.     

Cyclobutane-substituted diacetamido sulfides and 2,5-diacylthiophenes

A general and convenient route for the synthesis of 2,5-di[1-methyl-1-arylcyclobutane-3-yl]- thiophenes 4a–c and bis[1-methyl-1-arylcyclobutane-3-yl]-2-(2-oxyethtylamido)thiazole sulfides 7a–c is reported. The characterization of these compounds was obtained by elemental analyses, IR, ¹³C, and ¹H NMR techniques. © 2003 Wiley Periodicals, Inc. 15:26–31, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10207