An acyclic monoanionic tetradentate nitrogen ligand was prepared through the condensation of 2-(4-tolyl)-malondialdehyde and 8-aminoquinoline to give (BDI(QQ))H where (BDI(QQ))H = (8-quinolyl)-NCHC(4-tolyl)CHNH-(8-quinolyl). Metal complexes, (BDI(QQ))MX, were prepared where MX = MgBr 2, ZnCl 3, and CdOAc 4. The spectroscopic and crystallographic properties of compounds 2, 3, and 4 were explored. Structures of complexes 2, 3, 4, and the tridentate ligand, (BDI(Q))OH, 5, are reported. 相似文献
Nitrogen is an element of utmost importance in chemistry, biology and materials science. Of its two NMR‐active isotopes, 14N and 15N, solid‐state NMR (SSNMR) experiments are rarely conducted upon the former, due to its low gyromagnetic ratio (γ) and broad powder patterns arising from first‐order quadrupolar interactions. In this work, we propose a methodology for the rapid acquisition of high quality 14N SSNMR spectra that is easy to implement, and can be used for a variety of nitrogen‐containing systems. We demonstrate that it is possible to dramatically enhance 14N NMR signals in spectra of stationary, polycrystalline samples (i.e., amino acids and active pharmaceutical ingredients) by means of broadband cross polarization (CP) from abundant nuclei (e.g., 1H). The BR oadband A diabatic IN version C ross‐ P olarization ( BRAIN–CP ) pulse sequence is combined with other elements for efficient acquisition of ultra‐wideline SSNMR spectra, including W ideband U niform‐ R ate S mooth‐ T runcation ( WURST ) pulses for broadband refocusing, C arr– P urcell M eiboom– G ill ( CPMG ) echo trains for T2‐driven S/N enhancement, and frequency‐stepped acquisitions. The feasibility of utilizing the BRAIN–CP/WURST–CPMG sequence is tested for 14N, with special consideration given to (i) spin‐locking integer spin nuclei and maintaining adiabatic polarization transfer, and (ii) the effects of broadband polarization transfer on the overlapping satellite transition patterns. The BRAIN–CP experiments are shown to provide increases in signal‐to‐noise ranging from four to ten times and reductions of experimental times from one to two orders of magnitude compared to analogous experiments where 14N nuclei are directly excited. Furthermore, patterns acquired with this method are generally more uniform than those acquired with direct excitation methods. We also discuss the proposed method and its potential for probing a variety of chemically distinct nitrogen environments. 相似文献
A vapoluminescent triarylboron-functionalized platinum(II) complex that displays a mechanism of vapochromism differing from all previously reported platinum(II) compounds has been synthesized. The luminescence color of 1 switches in response to many volatile organic compounds in the solid state, including hexanes, CH(2)Cl(2), benzene, and methanol. While vapochromism due to changes in Pt-Pt or π-π stacking interactions has been commonly observed, absorption and luminescence studies and single-crystal and powder X-ray diffraction data as well as multinuclear solid-state NMR experiments ((195)Pt, (13)C, (11)B, (2)H, and (1)H) revealed that the vapochromic response of 1 is instead due to changes in the excited-state energy levels resulting from local interactions of solvent molecules with the complex. Furthermore, these interactions result in inversion of the lowest-energy excited states of the complex in some cases, the first observation of this phenomenon in the solid state. 相似文献
Pore-scale finite-volume continuum models of electrokinetic processes are used to predict the Debye lengths, velocity, and potential profiles for two-dimensional arrays of circles, ellipses and squares with different orientations. The pore-scale continuum model solves the coupled Navier–Stokes, Poisson, and Nernst–Planck equations to characterize the electro-osmotic pressure and streaming potentials developed on the application of an external voltage and pressure difference, respectively. This model is used to predict the macroscale permeabilities of geomaterials via the widely used Carmen–Kozeny equation and through the electrokinetic coupling coefficients. The permeability results for a two-dimensional X-ray tomography-derived sand microstructure are within the same order of magnitude as the experimentally calculated values. The effect of the particle aspect ratio and orientation on the electrokinetic coupling coefficients and subsequently the electrical and hydraulic tortuosity of the porous media has been determined. These calculations suggest a highly tortuous geomaterial can be efficient for applications like decontamination and desalination.
The abs‐normal form (ANF) is a compact algebraic representation for piecewise linear functions. These functions can be used to approximate piecewise smooth functions and contain valuable information about the nonsmoothness of the investigated function. The information helps to define step directions within general Newton methods that obey the structure of the original function and typically yield better convergence. However, the computation of the generalized Newton directions requires the solution of a piecewise linear equation in ANF. It was observed that the ANF can become very large, even for simple functions. Hence, if a solver is based on the ANF and uses the (Schur‐complement) matrices of the explicit ANF representation, it has to be considered computationally expensive. In this paper, we will address this question and present the first (almost) matrix‐free versions of some solver for ANFs. The theoretical discussion is supported by some numerical run‐time experiments. 相似文献
The Wittig reaction to synthesize olefins is a very attractive method in organic synthesis. Recently, this methodology has been achieved utilizing simple metal catalysts and diazo compounds in addition to a phosphine and an aldehyde. The following work investigates the use of a variety of metallophthalocyanines (MPc’s) to catalyze Wittig-like reactions from ethyldiazoacetate. We also examine the influence of substitution on the aromatic ring of the aldehyde as well as various phosphines, arsines and antimony complexes. We have been able to exclusively synthesize the trans-olefins in excellent yields in short periods of time (1?h). 相似文献