Synthesis, characterization and crystal structures of dipyridyl-N-methylimine and cloro-bis (N,N′-2,2′-dipyridyl-N-methylimine)lithium complex

The preparation and characterization by X-ray crystallography and NMR spectroscopy of the 2,2′-dipyridyl-N-methylimine (dpNmei) and the complex [cloro-bis(N,N′-2,2′-dipyridyl-N-methylimine)]lithium [Li(dpNmei)₂(Cl)] is reported. The dpNmei was prepared from the reaction of the 2,2′-dipyridyl ketone (dpk) and methylamine and crystallizes in the monoclinic P21/n space group with a = 6.3887(6), b = 10.1709(10), c = 16.7594(17) (Å), β = 100.918(2)^∘ and V = 1069.29(18) ų. The lithium complex was obtained from the reaction of dpNmei and LiCl in a molar ratio 2:1. [Li(dpNmei)₂Cl] crystallizes in the orthorhombic Pbcn space group with a = 10.0092(12), b = 9.8201(12), c = 23.669(3) (Å) and V = 2326.4(5) ų. The crystallographic data show that the lithium ion is five-coordinated with four coordination bonds N→Li due the chelation of dpNmei and one Li–Cl bond.     

X-ray structural and spectroscopic investigation of 1-piperidine-2,4-dinitrobenzene

The crystal structure of the title compound (C₁₁H₁₃N₃O₄) has been determined by single-crystal X-ray diffraction. The compound is monoclinic, space group P2₁/n, witha=9.968(2),b=9.156(2),c=13.249(2)Å, =102.05(2)°, andD _x=1.563 gcm^–3 forZ=4. The aromatic ring shows a slight boat deformation. Theo- andp-NO₂ groups are twisted out of the plane of the phenyl ring by 39.0(2)° and 4.4(1)°, respectively. The piperidine ring exhibits a slightly deformed chair conformation. Short C–H...O intermolecular contacts stabilize the three dimensional structure. UV and NMR data indicate that the molecule in solution presents a conformation similar to that of the the solid state.     

A Visual Tagging Process for Mix and Sort Combinatorial Chemistry

Colored glass beads and caps provide a simple color-coding strategy adapted to porous plastic containers and allow visual identification of the individual constituents of combinatorial libraries.     

Amperometric Detection and Quantification of 8‐Hydroxy‐2′‐deoxyguanosine (8‐OHdG) Using Dendrimer Modified Electrodes

8‐Hydroxy‐2′‐deoxyguanosine (8‐OHdG) detection by high performance liquid chromatography (HPLC) with amperometric detection was studied using a Au electrode modified with different dendrimer based thin films. Gold electrode is thiol‐modified, forming self‐assembled monolayers on which different generation PAMAM dendrimers with terminal functional groups ? COOH and ? NH₂ have been attached using peptidic bonds. Results obtained in synthetic samples show low limits of detection and quantification for 8‐OHdG (1.2×10^?9 and 3.7×10^?9 M respectively), with matrix interference elimination, thus avoiding sample pretreatment. Best results are obtained with electrodes modified with aliphatic amino thiols and 3.5 and 4.5 generation carboxylated dendrimers (Au/AET/DG^3.5 and Au/AET/DG^4.5), demonstrating that these materials constitute a good alternative for 8‐OHdG determination in biological fluids.     

Direct femtosecond laser writing of waveguides in As2S3 thin films

Single-channel waveguides and Y couplers were fabricated in chalcogenide thin films by use of femtosecond laser pulses from a 25-MHz repetition rate Ti:sapphire laser. Refractive-index differentials (delta n > 10(-2)) were measured through interferometric microscopy and are higher than the typical values reported for oxide glasses. The dependence of the index differential on the peak intensity reveals the nonlinear nature of the photosensitivity in arsenic trisulfide below its bandgap energy, and the refractive-index change is correlated to the photoinduced structural changes inferred by Raman spectroscopy data. A free-electron model to predict the parametric dependence of delta n is proposed.     

Tellurite glasses with peak absolute Raman gain coefficients up to 30 times that of fused silica

An experimental system has been assembled to measure the absolute values of the Raman gain spectrum for millimeter-thick glass samples. Results are reported for two new oxide glasses with Raman gain coefficients as much as 30 times larger than that of fused silica and more than twice its spectral coverage.     

An in-depth look at the effect of Lewis acid catalysts on Diels-Alder cycloadditions in ionic liquids

The present work explores in detail the Diels-Alder reaction between cyclopentadiene and a series of dienophiles, performed in an innovative medium such as an ionic liquid. The potential activation of different Lewis acid catalysts and their load effect when used in combination with this solvent have been explored, in order to settle the improvement on rates and selectivities.