Search results for "Polar"

Electrosynthesis of Stable Betulin‐Derived Nitrile Oxides and their Application in Synthesis of Cytostatic Lupane‐Type Triterpenoid‐Isoxazole Conjuga…

2021

Localized states in wide-gap oxide glasses

1997

Localized states manifest themselves by light absorption at the optical gap of a glass and by luminescence excited there with Stoke's shift. They are created by the minority structural motifs of one or many structural modifications in which a material can exist, and which can provide electronic states absorption at the optical gap. Their wavefunctions overlapping determine the luminescence intensity dependence on the temperature [I(T)on the order of magnitude exp(- T/T 0 )] and power law (t -1 ) of luminescence decay kinetics, which include intra-center processes due to triplet-singlet transitions and recombination processes due to a tunnel and overbarrier transitions, as well as a fast com…

Book Review: Preparative Polar Organometallic Chemistry. Vol. 1. By L. Brandsma and H. D. Verkruijsse

1990

Time-dependent monomerization of gramicidin A, enhanced by phosphatidylcholine in non-polar solvents

1986

Abstract The usefulness of size-exclusion high-performance liquid chromatography for the study of gramicidin A dimer—monomer conformational equilibrium in non

ChemInform Abstract: Preparation and Nonlinear Optics of Monodisperse Oligo(1,4-phenyleneethynylene)s.

2010

Oligo(1,4-phenyleneethynylene)s 1a−e, with solubilizing propoxy side chains, were prepared by use of Hagihara−Sonogashira coupling reactions. The synthetic strategy was based on a building block system and on the use of trimethylsilyl and triisopropylsilyl protecting groups that could be cleaved selectively. The extension of the conjugation with an increasing number of repeat units provokes a bathochromic shift of the long wavelength absorption and a superlinear increase of the second hyperpolarizability |γ|. The corresponding third harmonic generation (THG) measurements were performed using polystyrene matrices and variable laser wavelengths. We conclude that the conjugation length is much…

Synthesis and characterization of a new spirooxindole grafted pyrrolidino/piperidine moiety

2021

In this text, we synthesized and characterized a new spirooxindole grafted pyrrolidino/piperidine moieties. The new hit obtained via one-pot reaction of the chalcone based cyclohexanone with the isatin and (R)-piperidine-2-carboxylic acid in MeOH under reflux for 48 h. The compound exclusively obtained in regio-selective and diastereo-selective manner. The chemical feature of the target compound is confirmed by 1H NMR and 13C NMR spectroscopy. In addition, we reported for the first time the X-ray single crystal structure of isatin. Its molecular packing  depends mainly on strong O…H hydrogen bonds and π-π stacking interactions as well as weak H…H and H…C contacts. Using DFT calculations, is…

Effect of structural parameters on the polarizabilities of methanol clusters: a hirshfeld study

2008

The polarizabilities of fifty methanol clusters (CH3OH)n, n = 1 to 12, were calculated at the B3LYP/6-311++G** level of theory and partitioned into molecular contributions using the Hirshfeld-I method. The resulting molecular polarizabilities were found to be determined by the polarizabilities of the two parts of the molecule, the hydrophilic hydroxyl group and the hydrophobic methyl group, each exhibiting a different dependency upon the local environment. The polarizability of the hydroxyl group was found to be dependent on the number, type, and strength of the hydrogen bonds a methanol molecule makes, whereas the polarizability of the methyl groups is mostly influenced by sterical hindran…

Magneto-Transport Results in Alq3 Based OSVs

2015

The achievement of good magnetoresistance signal at room temperature is an important requirement for the possible future development of organic devices for applications. However, until now only few works reported room temperature MR effect in organic spin valves (OSVs). In this regard, this chapter is dedicated to the investigation of Alq3-based OSVs where Alq3 molecule was chosen since it is a standard material in the field. A systematic study on Co/Alq3/Co OSVs will be presented showing room temperature MR results. Moreover, inelastic electron tunneling spectroscopy (IETS) technique will be used to prove spin injection into the organic layer. Finally, an insulating oxide barrier (Al2O3 or…

Magnetic moment investigations of epitaxial magnetite thin films

2008

In this report, we provide an x-ray magnetic circular dichroism (XMCD) study for 100nm thick epitaxial magnetite (Fe3O4) films on MgO (001) and Al2O3 (0001) substrates. For XMCD, we recorded the surface sensitive total electron yield and the bulk sensitive transmission spectra. From the analysis of the XMCD data, we find an increased Fe spin moment (10% larger) at the surface of the film on MgO (100) with respect to the corresponding bulk value of the film. Surface and bulk spin moments of the film on Al2O3(0001) are almost equal. For both films, the bulk orbital to spin moments ratio increases from zero at 70K to 0.03–0.04 at 300K. For Fe3O4∕MgO (001), the surface orbital to spin moment ra…

Development of MR active contrast agents via Parahydrogen Induced Polarization

2009

Parahydrogen Induced Polarization provides dramatic MR signal enhancement that can be exploited for molecular imaging. This method allows amongst others for Magnetic Resonance Imaging of 13C and 15N, which is usually constrained by the low MR sensitivity of these nuclei. By combining hydrogenation of barbiturates with parahydrogen under special experimental conditions (PASADENA under pressure) with a polarization transfer sequence we demonstrate the transfer of the initial 1H polarization to 13C. The polarization transfer yields a signal increase for 13C of more than 1000. Hence, the role of certain target compounds such as anesthetics like the barbituric acid derivatives could be investiga…