Showing papers on "Derivative (chemistry) published in 2017"

Derivative-Free and Blackbox Optimization

Abstract: Derivative-free optimization (DFO) is the mathematical study of the optimization algorithms that do not use derivatives. While a DFO algorithm was used to test one of the worlds first computers (the MANIAC in 1952), it was not until the 1990s that DFO algorithms were studied mathematically. Blackbox optimization (BBO) is the study of optimization problems where the objective function is a blackbox. That is, no analytic description of the function is available, but given an arbitrary input the blackbox returns a function value. As BBO naturally arises whenever a computer simulation is involved in an optimization problem, BBO is one of the most rapidly expanding areas of applied optimization. BBO can naturally be approached by DFO. DFO algorithms have principally fallen into one of two categories: direct search methods and modelbased methods. Direct search methods work from an incumbent solution and examine a collection of trial points; if improvement is found, then the incumbent solution is updated, otherwise a search radius parameter is decreased and a new collection of trial points is examined. Model-based methods approximate the objective function with a model function, and use the gradients or even second derivatives of the model function to help guide optimization. (Note that while DFO studies algorithms that do not use derivatives, this does not mean that the objective function is nondifferentiable – for example the objective could be a computer simulation using numerical integration.) It was not until very recently that researchers began mixing direct search and model-based methods to create hybrid methods with improved performance.

Layered ternary M(n+1)AX(n) phases and their 2D derivative MXene: an overview from a thin-film perspective

Abstract: Inherently and artificially layered materials are commonly investigated both for fundamental scientific purposes and for technological application. When a layered material is thinned or delaminated ...

On the analysis of chemical kinetics system pertaining to a fractional derivative with Mittag-Leffler type kernel.

Abstract: The pivotal aim of this paper was to analyze a new fractional model of chemical kinetics system related to a newly discovered Atangana-Baleanu derivative with fractional order having non-singular and non-local kernel. The numerical solution is derived by making use of the iterative scheme. The existence of the solution of chemical kinetics system of arbitrary order is examined by implementing the fixed-point theorem. The uniqueness of the special solution of the studied model is shown. The effect of different variables and order of arbitrary ordered derivative on concentrations is demonstrated in tabular and graphical forms. The numerical results for chemical kinetics system pertaining to the newly derivative with fractional order are compared with the chemical kinetics system involving classical derivative.

Organotin(IV) complexes derived from proteinogenic amino acid: synthesis, structure and evaluation of larvicidal efficacy on Anopheles stephensi mosquito larvae

Abstract: Five new organotin(IV) complexes of composition [Bz2SnL1]n (), [Bz3SnL1H⋅H2O] (), [Me2SnL2⋅H2O] (), [Me2SnL3] () and [Bz3SnL3H]n () (where L1 = (2S)-2-{[(E)-(4-hydroxypentan-2-ylidene)]amino}-4-methylpentanoate, L2 = (rac)-2-{[(E)-1-(2-hydroxyphenyl)methylidene]amino}-4-methylpentanoate and L3 = (2S)- or (rac)-2-{[(E)-1-(2-hydroxyphenyl)ethylidene]amino}-4-methylpentanoate) were synthesized and characterized using 1H NMR, 13C NMR, 119Sn NMR and infrared spectroscopic techniques. The crystal structure of reveals a distorted trigonal-bipyramidal geometry around the tin atom where the oxygen atoms of the carboxylate ligand and a water ligand occupy the axial positions, while the three benzyl ligands are located at the equatorial positions. On the other hand, the analogous derivative of enantiopure L3H () consists of polymeric chains, in which the ligand-bridged tin atoms adopt the same trans-Bz3SnO2 trigonal-bipyramidal configuration and are now coordinated to a phenolic oxygen atom instead of H2O. In , the OH hydrogen of the ketoimine substituent has moved to the nearby nitrogen atom while in the salicylidene derivative , the OH is located almost midway between the phenolic oxygen atom and the nitrogen atom of the C[DOUBLE BOND]N group. For the dibenzyltin derivative , a polymeric chain structure is observed as a result of a long intermolecular Sn⋅⋅⋅O bond involving the exocyclic carbonyl oxygen atom from the tridentate ligand of a neighbouring tin-complex unit. The tin atom in this complex has distorted octahedral coordination geometry. In contrast, the racemic dimethyltin(IV) complexes and display discrete monomeric structures with a distorted octahedral- and trigonal-bipyramidal geometry, respectively. The structures show that the coordination mode of the Schiff base ligand depends primarily on the number of bulky benzyl ligands (R) at the tin atom, as indeed found in the structures of related complexes where R = phenyl. With three bulky R groups, the tridentate chelating O,N,O coordination mode is preferred, whereas with fewer or less bulky R ligands, only the carboxylate and hydroxy groups are involved, which leads to polymers. Larvicidal efficacies of two of the new tribenzyltin(IV) complexes ( and ) were assessed on the second larval instar of Anopheles stephensi mosquito larvae and compared with two triphenyltin(IV) analogues, [Ph3SnL1H]n and [Ph3SnL3H]n. The results demonstrate that the compounds containing Sn–Ph ligands are more effective than those with Sn–Bz ligands. Copyright © 2016 John Wiley & Sons, Ltd.

Rhenium-catalysed hydroboration of aldehydes and aldimines

Abstract: The first examples for the rhenium-catalysed hydroboration of aldehydes, ketones and aldimines, including heteroaromatic quinoline, are reported herein Reactions are remarkably chemoselective and tolerant of several functional groups A wide array of rhenium complexes were efficient pre-catalysts for these hydroborations, including new low-valent complexes of the formula [Re(N–N)(CO)3(L)]X (N–N = bipy derivative, L = labile ligand/solvent, and X = [BArF4]− and [B(3,5-di-tBu-cat)2]−), which have been characterized fully including an X-ray diffraction study for [Re(bipy)(CO)3(quin)][BArF4] (2) A new silver spiroboronate ester Ag[B(3,5-di-tBu-cat)2](NCCH3)3 (3) was prepared and characterized fully, including an X-ray diffraction study, and used to make one of the new rhenium complexes

Fluoride Anion Complexation by a Triptycene-Based Distiborane: Taking Advantage of a Weak but Observable C−H⋅⋅⋅F Interaction

Abstract: Fluoride anion complexation impacts a number of areas ranging from sensing to nucleophilic fluorination chemistry. Described here is a new bidentate Lewis acid consisting of two stiborane units connected by a 1,8-triptycenediyl backbone. This neutral derivative captures fluoride with an unprecedented affinity for a neutral, water-compatible Lewis acid. Structural, spectroscopic and computational studies demonstrate that fluoride anion binding is assisted by the formation of a C-H⋅⋅⋅F hydrogen bond which involves a methine group of the 1,8-triptycenediyl backbone.

A new approach to switchable photochromic materials by combining photochromism and piezochromism together in an AIE-active molecule

Abstract: A carbazole containing triphenylethylene derivative (TrPEBCar) has been designed and synthesized, which combines aggregation-induced emission (AIE), piezochromism and photochromism together In the crystalline state, an intensive emission band at 448 nm was detected After pressing the crystalline solid, a [crystalline–amorphous] morphological transition takes place, in which the resulting amorphous state of TrPEBCar exhibits a different color and a red-shifted emission band at 470 nm Photochromic behavior of TrPEBCar is achieved by utilizing a stilbene-type intramolecular photocyclization in the crystalline state In addition, we report for the first time morphology-dependent photochromism, in which the photochromic properties of TrPEBCar are only observed in the crystalline state but not in the amorphous state Therefore, the methods of pressing/fuming and heating/fuming act as gates to switch the photochromic properties by changing the aggregation states between the crystalline and amorphous states By combining the piezochromic properties with the photochromic properties, the ON/OFF states of TrPEBCar can easily be observed by the different colors and emission properties The triphenylethylene derivative with simple molecular structure provides a new approach for gated photochromic materials with both switch and indicator

The derivative NLS equation: global existence with solitons

Abstract: We extend the global existence result for the derivative NLS equation to the case when the initial datum includes a finite number of solitons. This is achieved by an application of the B\"{a}cklund transformation that removes a finite number of zeros of the scattering coefficient. By means of this transformation, the Riemann--Hilbert problem for meromorphic functions can be formulated as the one for analytic functions, the solvability of which was obtained recently.

Cd-Based metal-organic frameworks from solvothermal reactions involving in situ aldimine condensation and the highly sensitive detection of Fe3+ ions.

Abstract: Four Cd(II)-based compounds (1–4) were synthesized from solvothermal reactions involving the in situ aldimine condensation of an o-diamino-functionalized precursor 3,6-di(4H-imidazol-4-yl)benzene-1,2-diamine (L), Cd(NO3)2·4H2O and aldehyde. Two modes of cycloaddition ([4 + 1] cycloaddition and [4 + 2] cycloaddition) occurred during condensation, causing the in situ generation of two benzimidazole derivative ligands (L1 and L3) and a quinoxaline derivative ligand (L2). Furthermore, the chemical selectivity of the condensation was studied, where the condensation of o-diamino and the aldehyde is more stable and easy to operate. This strategy enriches the synthesis method of MOFs. Additionally, compound 2 containing uncoordinated quinoxaline N atoms showed excellent luminescent sensitivity for Fe3+ detection.

The influence of halogen type on structural features of compounds containing α-halo-α,α-dinitroethyl moieties

Abstract: We report the synthesis, as well as the molecular and crystal structures of N-(2-halo-2,2-dinitroethyl)pyrrolidine-2,5-diones (Hal = F, Cl, Br). A combination of X-ray structural analysis and quantum chemistry calculations was used for comparative analysis of molecular packing in the crystals of the synthesized compounds. It was shown that the fluorinated derivative contained a shortened F···F halogen bond of the first type, and in the bromo derivative the bromine atoms formed a relatively strong Br···O=C halogen bond of the second type, while the chlorine atom in the structure of chloro derivative interacted with a nitro group oxygen atom, also forming a weak Cl···O2N halogen bond of the second type. These variations in the “preferences” of different halogen atoms resulted in observable differences in the crystal structures of the studied compounds.

Synthesis, radiolabeling and biological distribution of a new dioxime derivative as a potential tumor imaging agent

Abstract: A novel dioxime derivative (2E,2′E,3E,3′E)-3,3′-(pyrimidine-4,5-diylbis(azanylylidene))bis(butan-2-one)dioxime was synthesized with a yield of 65%. IR, elemental analysis, mass spectroscopy and 1H-NMR were used to characterize the structure of the synthesized compound. 99mTc-dioxime was radio-synthesized with a high radiochemical yield of 97.8 ± 0.5% and in vitro stability of 6 h under the optimum conditions. The preclinical evaluation of 99mTc-dioxime in solid tumor-bearing mice showed high accumulation in solid tumor cells with a high Target/Non-Target ratio of 5.14 at 30 min post-injection. This study suggests that 99mTc-dioxime derivative is a promising candidate as a new 99mTc-based tumor-imaging agent after further preclinical studies.

Defluorination and covalent grafting of fluorinated graphene with TEMPO in a radical mechanism

Abstract: Fluorinated graphene (FG) can be regarded as the representative two-dimensional (2D) material to study the characteristics of “2D chemistry”, whereas its derivative reaction mechanism is still required to be revealed for the destination of deciduous fluorine atoms after defluorination of FG. Herein, we proposed a particular derivative reaction of FG by employing 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) as the attacking reagent, and the products were characterized via Electron Paramagnetic Resonance Spectroscopy (EPR), Mass Spectrometry (MS) and X-ray photoelectron spectroscopy (XPS). It was demonstrated that the defluorination caused by TEMPO occurred in a radical mechanism, thus leading to formations of new spin centers on graphene nanosheets as well as CC bonds. More importantly, the deciduous fluorine atoms after defluorination, which existed in TEMPO fluoride molecules, have been detected for the first time. Meanwhile, some TEMPO molecules were covalently grafted on the nanosheet, which resulted from the coupled reaction between TEMPO radical and the spin center on the FG nanosheet. These findings deepen the research of derivative reactions of FG, meanwhile providing a particular view to investigate the chemistry characteristics of 2D materials from a radical mechanism.

Increased oxidative stress and plasma Hsp70 levels among gasoline filling station attendants.

Abstract: Objectives:Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organic derivative of manganese (Mn) and is used as an antiknock agent and octane enhancer in gasoline. In this article, we teste...