scholarly journals The charge percolation mechanism and simulation of Ziegler-Natta polymerizations. Part III. Oxidation states of transition metals

2006 ◽  
Vol 71 (4) ◽  
pp. 357-372 ◽  
Author(s):  
Branka Pilic ◽  
Dragoslav Stoiljkovic ◽  
Ivana Bakocevic ◽  
Slobodan Jovanovic ◽  
Davor Panic ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Oxidation States ◽  
Support Surface ◽  
Active Centers ◽  
Active Centre ◽  
Whole Process ◽  
Oxidation Reduction ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
A Charge

The oxidation state of the transition metal (Mt) active centre is the most disputable question in the polymerization of olefins by Ziegler-Natta (ZN) and metallocene complexes. In this paper the importance and the changes of the Mt active centers are presented and discussed on the basis of a charge percolation mechanism (CPM) of olefin polymerization. Mt atoms can exist in different oxidation states and can be easily transformed from one to another state during activation. In all cases, the Mt atoms are present in several oxidation states, i.e., Mt+(n-1), Mt+(n) to Mt+(n+1), producing an irregular charge distribution over the support surface. There is a tendency to equalize the oxidation states by a charge transfer from Mt+(n-1) (donor) to Mt+(n+1) (acceptor). This cannot occur since the different oxidation states are highly separated on the support. However, monomer molecules are adsorbed on the support producing clusters with stacked ?-bonds, making a ?-bond bridge between a donor and an acceptor. Once a bridge is formed (percolation moment), charge transfer occurs. The donor and acceptor equalize their oxidation states simultaneously with the polymerization of the monomer. The polymer chain is desorbed from the support, freeing the surface for subsequent monomer adsorption. The whole process is repeated with the oxidation-reduction of other donor-acceptor ensembles.

scholarly journals Nanopore-induced host–guest charge transfer phenomena in a metal–organic framework

2018 ◽  
Vol 9 (13) ◽  
pp. 3282-3289 ◽  
Author(s):  
S. Yamamoto ◽  
J. Pirillo ◽  
Y. Hijikata ◽  
Z. Zhang ◽  
K. Awaga
Keyword(s):  
Charge Transfer ◽  
Self Assembly ◽  
Metal Organic Framework ◽  
Donor And Acceptor ◽  
Organic Electron ◽  
Donor Acceptor ◽  
Metal Organic ◽  
Bulk Scale ◽  
A Charge ◽  
Organic Framework

Using the “crystal sponge” approach, weak organic electron donor molecules were impregnated and evenly distributed in a crystal of a metal–organic framework (MOF), with the self-assembly of the donor–acceptor pairs with electron acceptor ligands. The nanopores of the MOF confined them and induced a charge transfer phenomenon, which would not occur between donor and acceptor molecules in a bulk scale.

scholarly journals Electronics Communication and Photoinduced Intramolecular Electron Transfer in Hybrid Ru(II)-Re(I) Complexes Using Eigenstate-Based and Diabatic-State-Based Models

2021 ◽  
Author(s):  
Rangsiman Ketkaew
Keyword(s):  
Electron Transfer ◽  
Density Functional ◽  
Reduction Reaction ◽  
Vital Role ◽  
Energy Curve ◽  
Intramolecular Electron Transfer ◽  
Oxidation Reduction ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Adiabatic State

Photoinduced intramolecular electron transfer (PIET) plays a vital role in the efficiency of electronics communication in transition metal complexes catalysing oxidation-reduction reaction. In this work, we theoretically calculate the rate of electron transfer(ET) in Ru(II)-BL-Ru(I) hybrid complexes; where BL is bridging ligand. A brief concept of ET in the basis of Marcus theory, which is extended to address a variety of different type of ET, is provided. We show that, in the case of Ru(II)-BL-Ru(I) complex, ET involves a non-adiabatic state which thanks to a fast electronics communication between donor and acceptor connected by BL and becomes rigid complex. Single electron transferring in Ru(II)-BL-Ru(I) complex governed by PIET constructed by potential energy curve as change of structural transformation over time-evolution. We also investigate the mechanism of PIET involving a redox reaction in excited state, wherein the oxidation state of Ru(II) (donor) and Ru(I) (acceptor) changes. To access non-adiabatic state of Ru(II)-BL-Ru(I), we use constrained density functional theory to allow ground state calculation to be performed along with geometry constraints. We also systematically study the role of distance of donor-acceptor separation on kinetics of PIET

scholarly journals Ultra-Weak Cell Radiation as an Impulse to Activate Biological Signal Transmission Paths

2021 ◽  
Vol 4 (3) ◽  
Keyword(s):  
Quantum Mechanics ◽  
Charge Transfer ◽  
20Th Century ◽  
Signal Transmission ◽  
Molecular Structures ◽  
Atoms And Molecules ◽  
Biological Signal ◽  
Donor Acceptor ◽  
Molecular Signal ◽  
A Charge

Basic physical research at the beginning of the 20th century developed concepts of the energetic properties of atoms and molecules with quantum mechanics, which increasingly also included biological structures. Considerations of a “charge transfer” or also known as “donor-acceptor interactions” of the movement of electrons between molecular structures developed. This energetic process is the basis of the ultra-weak cell radiation, which is to be discussed as the basis for the activation of the molecular signal transmission.

Interaction of manganese corroles with TCNQ and related acceptor molecules

2020 ◽  
Vol 24 (05n07) ◽  
pp. 705-711
Author(s):  
Benedikt Wolfram ◽  
Çağla Baş ◽  
Christian Kleeberg ◽  
Martin Bröring
Keyword(s):  
Charge Transfer ◽  
Single Crystals ◽  
High Reactivity ◽  
Geometric Parameters ◽  
Oxidation States ◽  
Stacking Interactions ◽  
Oxygenated Compounds ◽  
Axial Ligands ◽  
Donor Acceptor ◽  
New Compounds

Manganese corroles with the Mn atom in the oxidation states +III and +IV have been probed as donor moieties for supramolecular stacked donor–acceptor complexes with the typical acceptor units TCNQ (tetracyanoquinone), TCNP (tetracyanopyrazine), and TCNB (tetracyanobenzene). Four new compounds formed as single crystals from different co-crystallization attempts. In those cases where a Mn(III) corrole was used as the donor component, hydrolyzed and/or oxygenated compounds [(cor)Mn(TCNQ*)] and [(cor*)Mn(TCNP*)] were obtained as the exclusive products. With chloridomanganese(IV) corroles, sandwich-like 2:1 complexes [(cor)MnCl][Formula: see text][TCNQ] and [(cor)MnCl][Formula: see text][TCNB] form, with both components left intact. Crystallographic analyses reveal partial or complete charge transfer to unusual axial ligands and thus prove the high reactivity of Mn(III) corroles in the first two cases. For the sandwich arrangements, almost-unaltered geometric parameters of the Mn(IV) corroles are observed, pointing to negligible structural consequences for metal corroles when engaged in stacking interactions.

Synthesis and X-Ray Study of a Charge-Transfer Complex of Pyrido[2,3-H]pyrrolo[1,2-a]quinoxaline - 7,7,8,8-Tetracyano-p-quinodimethane (1:1)

1988 ◽  
Vol 41 (6) ◽  
pp. 971 ◽  
Author(s):  
B Viossat ◽  
NH Dung ◽  
JC Daran ◽  
JC Lancelot ◽  
M Robba
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complex ◽  
Three Dimensional ◽  
Direct Methods ◽  
Title Complex ◽  
Full Matrix ◽  
X Ray ◽  
Donor And Acceptor ◽  
A Charge ◽  
Tcnq Molecule

The structure of the title complex has been determined by a three-dimensional X-ray analysis. Triclinic crystals in space group Pī have lattice parameters a 7.0912(8), b 7.692(2), c 19.119(3)Ǻ, α 87.09(2),β 84.01(1),γ 82.72(1)°, Z 2. The structure was solved by means of direct methods and refined by full matrix least squares to R 0.039 and Rw 0.035 for 1671 observed reflections. Almost parallel tetracyanoquinodimethane (tcnq ) and pyridopyrroloquinoxaline molecules are stacked alternately along the a axis. Differences in C-C distances for the complexed tcnq molecule suggest a certain amount of charge-transfer interaction between donor and acceptor molecules.

Elementorganische Verbindungen mit o-Phenylenresten, XXXI [1]. Charge-transfer-Komplexe von 2,3,7,8-Tetrakis(methylthio)chalkogenanthrenen mit 7,7,8,8-Tetracyanchinodimethan und Tetracyanethen / Organometalloidal Compounds with o-Phenylene Substituents, Part XXXI [1]. Charge-transfer Complexes of 2,3,7,8-Tetrakis(methylthio)chalkogenanthrenes with 7,7,8,8-Tetracyanoquinodimethane and Tetracyanoethene

1998 ◽  
Vol 53 (11) ◽  
pp. 1316-1322 ◽  
Author(s):  
Marc Dötze ◽  
Hendrik Czepat ◽  
Jens Kudnig ◽  
Günter Klar
Keyword(s):  
Charge Transfer ◽  
Columnar Structure ◽  
Charge Transfer Complexes ◽  
Slow Evaporation ◽  
Dilute Solutions ◽  
Donor And Acceptor ◽  
Mndo Calculations ◽  
Donor Acceptor ◽  
Type Character ◽  
Tcnq Molecule

The title compounds are prepared by slow evaporation of dilute solutions of the components. 2,3,7,8-Tetrakis(methylthio)thianthrene and -selenanthrene give isostructural 2:1 complexes with 7,7,8,8-tetracyanoquinodimethane (TCNQ) built up by donor/acceptor/donor units in which the TCNQ molecule is inserted into the cavity formed by two of the folded, oppositely arranged chalcogenanthrene molecules. These units are connected to chains by S -S contacts via the methylthio groups. From 2,3,7,8-tetrakis(methylthio)thianthrene and tetracyanoethene again a 2:1 complex is obtained, however, with a columnar structure in which two donor stacks are slightly interlinked by an acceptor stack thus forming a structure with alternating donor and acceptor molecules. The molecules are arranged in such a way that an optimum overlap of the HOMOs of the donors and the LUMOs of the acceptors, all of which are of π-type character according to MNDO calculations, is secured.

scholarly journals A general design approach toward covalent organic frameworks for highly efficient electrochemiluminescence

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Ya-Jie Li ◽  
Wei-Rong Cui ◽  
Qiao-Qiao Jiang ◽  
Qiong Wu ◽  
Ru-Ping Liang ◽  
...  
Keyword(s):  
Charge Transfer ◽  
High Speed ◽  
Intramolecular Charge Transfer ◽  
High Sensitivity ◽  
Covalent Organic Frameworks ◽  
Transport Networks ◽  
Promising Direction ◽  
Highly Efficient ◽  
Donor And Acceptor ◽  
Donor Acceptor

AbstractElectrochemiluminescence (ECL) plays a key role in analysis and sensing because of its high sensitivity and low background. Its wide applications are however limited by a lack of highly tunable ECL luminophores. Here we develop a scalable method to design ECL emitters of covalent organic frameworks (COFs) in aqueous medium by simultaneously restricting the donor and acceptor to the COFs’ tight electron configurations and constructing high-speed charge transport networks through olefin linkages. This design allows efficient intramolecular charge transfer for strong ECL, and no exogenous poisonous co-reactants are needed. Olefin-linked donor-acceptor conjugated COFs, systematically synthesized by combining non-ECL active monomers with C2v or C3v symmetry, exhibit strong ECL signals, which can be boosted by increasing the chain length and conjugation of monomers. The present concept demonstrates that the highly efficient COF-based ECL luminophores can be precisely designed, providing a promising direction toward COF-based ECL phosphors.

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