Convenient and Efficient One-Pot Method for the Synthesis of 2-Amino-tetrahydro-4H-chromenes and 2-Amino-4H-benzo[h]-chromenes Using Catalytic Amount of Amino-Functionalized MCM-41 in Aqueous Media

A convenient and efficient one-pot method for the synthesis of 2-amino-tetrahydro-4H-chromene and 2-amino-4H-benzo[h]-chromene derivatives has been developed using a catalytic amount of amino-functionalized MCM-41 in aqueous medium. This efficient technique has the advantages of giving 4H-tetrahydro-chromene and 4H-benzo[h]chromene building blocks using a reusable catalyst in good to excellent yields, to be completed in short reaction times with a simple product isolation procedure.     

Studies on Co(II) and Cu(II) complexes of a ligand derived from 1,3-phenylenediamine and 5-bromosalicylaldehyde synthesis, characterisation, thermal properties and use as new precursors for preparation cobalt and copper oxide nano-particles

A symmetric tetradentate Schiff base ligand, N,N′-bis(5-bromosalicylaldehyde)-1,3-phenylenediamine [(Brsal)₂-1,3-phen) and its Cu(II) and Co(II) complexes with general formula M₂((Brsal)₂-1,3-phen)₂, where M=Co (1) and Cu (2)], have been synthesized and characterized by elemental analyses and FTIR spectroscopy. In addition, Schiff base ligand has been characterized by ¹HNMR spectroscopy. Thermogravimetric analysis of the ligand and its metal complexes reveals their thermal stability and decomposition pattern.     

Evidence for side-chain π-delocalization in a planar substituted benzene: an experimental and theoretical charge density study on 2,5-dimethoxybenzaldehyde thiosemicarbazone

The charge density in 2,5-dimethoxybenzaldehyde thiosemicarbazone (1) has been studied experimentally using Mo-K(α) X-ray diffraction at 100 K, and by theory using DFT calculations at the B3LYP/6-311++G(2d,2p) level. The quantum theory of atoms in molecules (QTAIM) was used to investigate the extent of π-delocalization in the thioamide side-chain, which is virtually coplanar with the benzene ring. The experimental and theoretical ellipticity profiles along the bond paths were in excellent agreement, and showed that some of the formal single bonds in the side-chain have significant π-bond character. This view was supported by the magnitudes of the topological bond orders and by the delocalization indices δ(Ω(A), Ω(B)). An orbital decomposition of δ(Ω(A), Ω(B)) demonstrated that there was significant π-character in all the interchain non-H chemical bonds. On the other hand, the source function referenced at the interchain bond critical points could not provide any evidence for π-delocalization, showing instead only limited σ-delocalization between nearest neighbors. Overall, the topological evidence and the atomic graphs of the oxygen atoms did not provide convincing evidence for π-delocalization involving the methoxy substituents.     

Bis[(2,3,4-Trimethoxy-Benzylidenepropylideneamino)Phenyl]Ether: Synthesis,Characterization and Crystal Structure

Abstract  

New Schiff base compound bis[(2,3,4-trimethoxy-benzylidenepropylideneamino)phenyl]-ether (1) was synthesized and characterized by elemental analyses (CHN), FT-IR and ¹H-NMR spectroscopy and single-crystal X-ray diffraction. The title compound 1 crystallizes in triclinic system, space group P-1, with a = 6.8255(4) Å, b = 10.4346(4) Å, c = 19.4166(8) Å, α = 86.588(3)°, β = 85.019(4)°, γ = 89.042(4)°, V = 1375.12(11) Å³ and Z = 2. It displays a trans configuration about the C=N double bonds.     

MHD flows of UCM fluids above porous stretching sheets using two-auxiliary-parameter homotopy analysis method

The performance of a two-auxiliary-parameter homotopy analysis method (HAM) is investigated in solving laminar MHD flow of an upper-convected Maxwell fluid (UCM) above a porous isothermal stretching sheet. The analysis is carried out up to the 20th-order of approximation, and the effect of parameters such as elasticity number, suction/injection velocity, and magnetic number are studied on the velocity field above the sheet. The results will be contrasted with those reported recently by Hayat et al. [Hayat T, Abbas Z, Sajid M. Series solution for the upper-convected Maxwell fluid over a porous stretching plate. Phys Lett A 358;2006:396–403] obtained using a third-order one-auxiliary-parameter homotopy analysis method. It is concluded that the flow reversal phenomenon as predicted by Hayat et al. (2006) may have arisen because of the inadequacies of using just one-auxiliary-parameter in their analysis. That is, no flow reversal is predicted to occur if instead of using one-auxiliary-parameter use is made of two auxiliary parameters together with a more convenient set of base functions to assure the convergence of the series used to solve the highly nonlinear ODE governing the flow.     

Novel method for the fast preconcentration and monitoring of a ppt level of lead and copper with a modified hexagonal mesoporous silica compound and inductively coupled plasma atomic emission spectrometry.

A novel method for the rapid extraction and determination of a ppt level of Pb2+ and Cu2+ ions using partial silylated MCM-41 modified by a new salophen and inductively coupled plasma atomic emission spectrometry (ICP-AES) is introduced. The preconcentration factor of the method is 500, and the detection limits of Pb2+ and Cu2+ are 335 and 34 ng L(-1), respectively. The time and efficiency of extraction, the pH and flow rate, the type and minimum amount of acid for stripping of Pb2+ and Cu2+ from modified MCM-41 and the break-through volume were investigated. The maximum capacity of 4 mg of silylated MCM-41 modified by salophen used was found to be 150 +/- 4 and 117 +/- 3 microg of Pb2+ and Cu2+, respectively.     

Cobalt(III) Complex [CoL3] Derived from an Asymmetric Bidentate Schiff Base Ligand L (L=(5‐Bromo‐2‐hydroxybenzyl‐2‐furylmethyl)‐imine): Synthesis,Characterization and Crystal Structure

Cobalt(III) complex [CoL₃], where L=(5‐bromo‐2‐hydroxybenzyl‐2‐furylmethyl)imine, has been synthesized by reacting cobalt(II) nitrate with L. The complex has been characterized by elemental analysis and FT‐IR spectroscopy. The crystal structure of [CoL₃] was determined by X‐ray crystallography from single crystal data. It crystallizes in the triclinic space group$ P {\bar 1} $ with unit cell parameters:a=9.6644(10) Å,b=11.5657(11) Å,c=16.5809(17) Å,α=102.833(4)°,β=102.999(3)°,γ=105.480(3)°,V=1659.9(3) ųandZ=2. Thermal decomposition of [CoL₃] was studied by thermogravimetry in order to evaluate its thermal stability and thermal decomposition pathways.     

Synthesis and Characterization of Zinc(II) Complexes with 3,4-Dimethoxybenzaldehyde Thiosemicarbazone: The Crystal Structure of [Zn(34-MBTSC)2Cl2]

Abstract

The synthesis and characterization of three zinc(II) complexes [Zn(34-MBTSC)₂Cl₂] (1), [Zn(34-MBTSC)₂Br₂] (2), and [Zn(34-MBTSC)₂I₂] (3) of 3,4-dimethoxybenzaldehyde thiosemicarbazone (34-MBTSC) are reported. Elemental analysis (CHN) and spectral (FT-IR and ¹H-NMR) measurements have been used to characterize the complexes. In addition, the structure of the complex 1 has been determined by X-ray diffraction methods. In these complexes, the zinc(II) ion is bonded to two thioketonic sulfur donors in η¹-S bonding mode and to two halide ions in tetrahedral geometry.

Supplementary materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfer, and Silicon and the Related Elements for the following free supplemental files: Additional figures.     

A novel mononuclear square-planar copper(II) complex (Pip-H+)2[CuL4]2? with 2-cyano-3-(2,5-dimethoxyphenyl)acrylic acid as ligand: synthesis, crystal structures, spectral and thermal studies

Abstract  

2-Cyano-3-(2,5-dimethoxyphenyl)acrylic acid and its novel mononuclear square-planar copper(II) complex dipiperidinium tetrakis[2-cyano-3-(2,5-dimethoxyphenyl)acrylic acid]copper(II) ((Pip-H⁺)₂[CuL₄]²⁻) were synthesized and characterized by elemental analyses, FT–IR, UV–Vis spectroscopy, and thermogravimetric analysis. Moreover, the ligand was characterized by ¹H and ¹³C NMR spectroscopy. The structures of the ligand and its copper(II) complex were confirmed by single-crystal X-ray crystallography. Whereas the ligand crystallizes in the triclinic space group Pī with unit cell parameters a = 4.6911(2) ?, b = 9.0181(4) ?, c = 13.7084(6) ?, α = 74.946(4)°, β = 87.152(4)°, γ = 89.220(4)°, V = 559.34(4) ?³, and Z = 2, the complex crystallizes in the orthorhombic space group Pccn with unit cell parameters a = 27.5486(5) ?, b = 12.9484(2) ?, c = 15.8822(3) ?, V = 5,665.34(17) ?³, and Z = 4.