scholarly journals Gold Catalyzed Asymmetric Transformations

2021 ◽  
Author(s):  
Susana Porcel García
Keyword(s):  
Active Site ◽  
Coordination Mode ◽  
Ion Pairing ◽  
The Other ◽  
Chiral Ligands ◽  
Linear Arrangement ◽  
Asymmetric Transformations ◽  
Secondary Interactions ◽  
Square Planar ◽  
Bifunctional Ligands

In this chapter, the strategies developed to attain asymmetric reactions with gold are disclosed. Because of its preferred linear arrangement, to induce asymmetry, gold(I) needs to fulfill one of the following requirements: a) the use of bulky chiral ligands, that create a chiral pocket around the active site, b) the coordination to bifunctional ligands capable to establish secondary interactions with substrates, or c) tight ion pairing with chiral counteranions. On the other hand, gold(III) profits of a square-planar coordination mode, which approaches chiral ligands to substrates. However, its tendency to be reduced leads to difficulties for its applications in catalytic asymmetric transformations. Pioneering works using cyclometaled structures, have found the balance between stability and activity, showing its potential in asymmetric transformations.

Octabutanol(dodecaoxidododecaphenyl[18.4.0]dodecasiloxane)tetracopper(II)tetrasodium(I)

2006 ◽  
Vol 62 (4) ◽  
pp. m705-m707 ◽  
Author(s):  
Christian Bauch ◽  
Larissa Zherlitsyna ◽  
Norbert Auner ◽  
Michael Bolte
Keyword(s):  
Hydrogen Bonds ◽  
Title Compound ◽  
Coordination Mode ◽  
Molecular Conformation ◽  
The Other ◽  
Site Symmetry ◽  
Other Hand ◽  
Square Planar

Molecules of the title compound, [Cu4Na4(C6H5O2Si)12(C4H10O)8], are located on special positions of site symmetry \overline{4}. The Cu atoms are coordinated in a square planar fashion. The Na atoms, on the other hand, show an irregular sixfold coordination mode. The molecular conformation is stabilized by O—H...O hydrogen bonds.

scholarly journals Flower-Shaped C-Dots/Co3O4{111} Constructed with Dual-Reaction Centers for Enhancement of Fenton-Like Reaction Activity and Peroxymonosulfate Conversion to Sulfate Radical

Catalysts ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 135
Author(s):  
Zhibin Wen ◽  
Qianqian Zhu ◽  
Jiali Zhou ◽  
Shudi Zhao ◽  
Jinnan Wang ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Active Site ◽  
High Surface ◽  
High Surface Area ◽  
Reaction Centers ◽  
Organic Radicals ◽  
The Other ◽  
High Catalytic Activity ◽  
High Adsorption ◽  
High Turnover

Novel flower-shaped C-dots/Co3O4{111} with dual-reaction centers were constructed to improve the Fenton-like reaction activity and peroxymonosulfate (PMS) conversion to sulfate radicals. Due to the exposure of a high surface area and Co3O4{111} facets, flower-shaped C-dots/Co3O4{111} could provide more Co(II) for PMS activation than traditional spherical Co3O4{110}. Meanwhile, PMS was preferred for adsorption on Co3O4{111} facets because of a high adsorption energy and thereby facilitated the electron transfer from Co(II) to PMS. More importantly, the Co–O–C linkage between C-dots and Co3O4{111} induced the formation of the dual-reaction center, which promoted the production of reactive organic radicals (R•). PMS could be directly reduced to SO4−• by R• over C-dots. On the other hand, electron transferred from R• to Co via Co–O–C linkage could accelerate the redox of Co(II)/(III), avoiding the invalid decomposition of PMS. Thus, C-dots doped on Co3O4{111} improved the PMS conversion rate to SO4−• over the single active site, resulting in high turnover numbers (TONs). In addition, TPR analysis indicated that the optimal content of C-dots doped on Co3O4{111} is 2.5%. More than 99% of antibiotics and dyes were degraded over C-dots/Co3O4{111} within 10 min. Even after six cycles, C-dots/Co3O4{111} still remained a high catalytic activity.

scholarly journals Di-μ-chlorido-bis{[2-(di-tert-butylphosphanyl)biphenyl-3-yl-κ2C3,P]palladium(II)} dichloromethane disolvate

2013 ◽  
Vol 69 (2) ◽  
pp. m86-m86 ◽  
Author(s):  
Cedric W. Holzapfel ◽  
Bernard Omondi
Keyword(s):  
Palladium Complex ◽  
Solvent Molecule ◽  
Membered Ring ◽  
The Other ◽  
Coordination Geometry ◽  
Inversion Center ◽  
Asymmetric Unit ◽  
Coordination Sites ◽  
Square Planar ◽  
Cl Atoms

The asymmetric unit of the title compound, [Pd2Cl2(C20H26P)2]·2CH2Cl2, contains one half-molecule of the palladium complex and a dichloromethane solvent molecule. In the complex, two PdIIatoms are bridged by two Cl atoms, with the other two coordination sites occupied by a C atom of the biphenyl system and a P atom, resulting in a distorted square-planar coordination geometry of the PdIIatom and a cyclometallated four-membered ring. The Pd2Cl2unit is located about an inversion center. The planes of the rings of the biphenyl system make a dihedral angle of 66.36 (11)°.

scholarly journals Kinetic probes for inter-domain co-operation in human somatic angiotensin-converting enzyme

2005 ◽  
Vol 391 (3) ◽  
pp. 641-647 ◽  
Author(s):  
Olga E. Skirgello ◽  
Peter V. Binevski ◽  
Vladimir F. Pozdnev ◽  
Olga A. Kost
Keyword(s):  
Angiotensin Converting Enzyme ◽  
Enzymatic Activity ◽  
Active Site ◽  
The Other ◽  
Converting Enzyme ◽  
Human Enzyme ◽  
Independent Functions ◽  
The Common ◽  
The Individual ◽  
Hydrolysis Of

s-ACE (the somatic form of angiotensin-converting enzyme) consists of two homologous domains (N- and C-domains), each bearing a catalytic site. Negative co-operativity between the two domains has been demonstrated for cow and pig ACEs. However, for the human enzyme there are conflicting reports in the literature: some suggest possible negative co-operativity between the domains, whereas others indicate independent functions of the domains within s-ACE. We demonstrate here that a 1:1 stoichiometry for the binding of the common ACE inhibitors, captopril and lisinopril, to human s-ACE is enough to abolish enzymatic activity towards FA {N-[3-(2-furyl)acryloyl]}-Phe-GlyGly, Cbz (benzyloxycarbonyl)-Phe-His-Leu or Hip (N-benzoylglycyl)-His-Leu. The kinetic parameters for the hydrolysis of seven tripeptide substrates by human s-ACE appeared to represent average values for parameters obtained for the individual N- and C-domains. Kinetic analysis of the simultaneous hydrolysis of two substrates, Hip-His-Leu (S1) and Cbz-Phe-His-Leu (S2), with a common product (His-Leu) by s-ACE at different values for the ratio of the initial concentrations of these substrates (i.e. σ=[S2]0/[S1]0) demonstrated competition of these substrates for binding to the s-ACE molecule, i.e. binding of a substrate at one active site makes the other site unavailable for either the same or a different substrate. Thus the two domains within human s-ACE exhibit strong negative co-operativity upon binding of common inhibitors and in the hydrolysis reactions of tripeptide substrates.

scholarly journals Bis(μ-diisopropylphosphanido-κ2 P:P)bis[hydrido(triisopropylphosphane-κP)platinum(II)]

2012 ◽  
Vol 68 (6) ◽  
pp. m808-m808
Author(s):  
Nicole Arnold ◽  
Holger Braunschweig ◽  
Alexander Damme
Keyword(s):  
Molecular Structure ◽  
Title Compound ◽  
The Other ◽  
Planar Structure ◽  
Square Planar

In the centrosymmetric molecular structure of the title compound [Pt2(C6H14P)2H2(C9H21P)2], each PtII atom is bound on one side to a phosphane ligand (PiPr3) and a hydrido ligand. On the other side, it is bound to two phosphanide ligands (μ-PiPr2), which engage a bridging position between the two PtII atoms, forming a distorted square-planar structure motif. The Pt...Pt distance is 3.6755 (2) Å. A comparable molecular structure was observed for bis(μ-di-tert-butylphosphanido)bis[hydrido(triethylphosphane)platinum(II)] [Itazaki et al. (2004). Organometallics, 23, 1610–1621].

scholarly journals Understanding the Interaction Modes and Reactivity of Trimedoxime toward MmAChE Inhibited by Nerve Agents: Theoretical and Experimental Aspects

2020 ◽  
Vol 21 (18) ◽  
pp. 6510
Author(s):  
Alexandre A. de Castro ◽  
Daniel A. Polisel ◽  
Bruna T. L. Pereira ◽  
Elaine F. F. da Cunha ◽  
Kamil Kuca ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mus Musculus ◽  
Active Site ◽  
Theoretical Calculations ◽  
Nerve Agents ◽  
The Other ◽  
Chemical Weapons ◽  
Reactivation Process ◽  
Other Hand

Organophosphorus (OP) compounds are used as both chemical weapons and pesticides. However, these agents are very dangerous and toxic to humans, animals, and the environment. Thus, investigations with reactivators have been deeply developed in order to design new antidotes with better efficiency, as well as a greater spectrum of action in the acetylcholinesterase (AChE) reactivation process. With that in mind, in this work, we investigated the behavior of trimedoxime toward the Mus musculus acetylcholinesterase (MmAChE) inhibited by a range of nerve agents, such as chemical weapons. From experimental assays, reactivation percentages were obtained for the reactivation of different AChE–OP complexes. On the other hand, theoretical calculations were performed to assess the differences in interaction modes and the reactivity of trimedoxime within the AChE active site. Comparing theoretical and experimental data, it is possible to notice that the oxime, in most cases, showed better reactivation percentages at higher concentrations, with the best result for the reactivation of the AChE–VX adduct. From this work, it was revealed that the mechanistic process contributes most to the oxime efficiency than the interaction in the site. In this way, this study is important to better understand the reactivation process through trimedoxime, contributing to the proposal of novel antidotes.

scholarly journals Crystal structure of dichlorido{4-[(E)-(methoxyimino-κN)methyl]-1,3-thiazol-2-amine-κN3}palladium(II)

2015 ◽  
Vol 71 (1) ◽  
pp. m10-m11 ◽  
Author(s):  
Viktorita V. Dyakonenko ◽  
Olga O. Zholob ◽  
Svitlana I. Orysyk ◽  
Vasily I. Pekhnyo
Keyword(s):  
Bidentate Ligand ◽  
The Other ◽  
Mean Deviation ◽  
Amino Group ◽  
Methyl Group ◽  
Square Planar ◽  
The Mean ◽  
Van Der Waals Radii ◽  
Cl Atoms ◽  
Coordination Plane

In the title compound, [PdCl2(C5H7N3OS)], the PdIIatom adopts a distorted square-planar coordination sphere defined by two N atoms of the bidentate ligand and two Cl atoms. The mean deviation from the coordination plane is 0.029 Å. The methyl group is not coplanar with the plane of the metallacycle [torsion angle C—O—N—C = 20.2 (4)°]. Steric repulsion between the methyl group and atoms of the metallacycle is manifested by shortened intramolecular H...C contacts of 2.27, 2.38 and 2.64 Å, as compared with the sum of the van der Waals radii of 2.87 Å. The amino group participatesviaone H atom in the formation of an intramolecular N—H...Cl hydrogen bond. In the crystal, the other H atom of the amino group links moleculesviabifurcated N—H...(Cl,O) hydrogen bonds into chains parallel to [001].

Enhanced single-ion magnetic and ferroelectric properties of mononuclear Dy(iii) enantiomeric pairs through the coordination role of chiral ligands

2017 ◽  
Vol 53 (28) ◽  
pp. 3998-4001 ◽  
Author(s):  
Xi-Li Li ◽  
Ming Hu ◽  
Zhigang Yin ◽  
Cancan Zhu ◽  
Cai-Ming Liu ◽  
...  
Keyword(s):  
Ferroelectric Properties ◽  
The Other ◽  
Chiral Ligands ◽  
Chiroptical Properties

Mononuclear Dy(iii) enantiomeric pair with coordinated chiral ligands exhibit enhanced single-ion magnet, ferroelectric and chiroptical properties with respect to the other one with protonated chiral ligands.

R67, the Other Dihydrofolate Reductase:  Rational Design of an Alternate Active Site Configuration†

Biochemistry ◽  
2008 ◽  
Vol 47 (2) ◽  
pp. 555-565 ◽  
Author(s):  
Jian Feng ◽  
Sumit Goswami ◽  
Elizabeth E. Howell
Keyword(s):  
Dihydrofolate Reductase ◽  
Active Site ◽  
Rational Design ◽  
The Other
Sign in / Sign up

Export Citation Format

Share Document