Exciton Dissociation In Doped Conjugated Polymers

2003 ◽  
Vol 771 ◽  
Author(s):  
Vladimir I. Arkhipov ◽  
Paul Heremans ◽  
Evgenia V. Emelianova ◽  
Heinz Bässler
Keyword(s):  
Charge Transfer ◽  
Kinetic Energy ◽  
Conjugated Polymers ◽  
Electron Acceptor ◽  
Zero Point ◽  
Exciton Dissociation ◽  
Free Carriers ◽  
Geminate Pair ◽  
Interfacial Potential ◽  
A Charge

AbstractA model of carrier photogeneration in doped conjugated polymers is formulated. The model suggests that dissociation of a relaxed exciton into a Coulombically bound geminate pair (GP) occurs at a charge transfer center that consists of a polymer chain and a nearby electron acceptor. Further dissociation of the GP into free carriers is facilitated either by the kinetic energy of the zero-point oscillation of the on-chain carrier at low dopant concentrations or by the interfacial potential barrier for geminate pair recombination in polymer/electron acceptor blends.

scholarly journals Kinetic and chemical analyses of the cytokinin dehydrogenase-catalysed reaction: correlations with the crystal structure

2006 ◽  
Vol 398 (1) ◽  
pp. 113-124 ◽  
Author(s):  
Hana Popelková ◽  
Marco W. Fraaije ◽  
Ondřej Novák ◽  
Jitka Frébortová ◽  
Kristin D. Bilyeu ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Charge Transfer ◽  
Electron Acceptor ◽  
Flow Analysis ◽  
Reduction Rate ◽  
High Rate ◽  
Side Chain ◽  
Binary Complex ◽  
Cytokinin Dehydrogenase ◽  
A Charge

CKX (cytokinin dehydrogenase) is a flavoprotein that cleaves cytokinins to adenine and the corresponding side-chain aldehyde using a quinone-type electron acceptor. In the present study, reactions of maize (Zea mays) CKX with five different substrates (N6-isopentenyladenine, trans-zeatin, kinetin, p-topolin and N-methyl-isopentenyladenine) were studied. By using stopped-flow analysis of the reductive half-reaction, spectral intermediates were observed indicative of the transient formation of a binary enzyme–product complex between the cytokinin imine and the reduced enzyme. The reduction rate was high for isoprenoid cytokinins that showed formation of a charge-transfer complex of reduced enzyme with bound cytokinin imine. For the other cytokinins, flavin reduction was slow and no charge-transfer intermediates were observed. The binary complex of reduced enzyme and imine product intermediate decays relatively slowly to form an unbound product, cytokinin imine, which accumulates in the reaction mixture. The imine product only very slowly hydrolyses to adenine and an aldehyde derived from the cytokinin N6 side-chain. Mixing of the substrate-reduced enzyme with Cu2+/imidazole as an electron acceptor to monitor the oxidative half-reaction revealed a high rate of electron transfer for this type of electron acceptor when using N6-isopentenyladenine. The stability of the cytokinin imine products allowed their fragmentation analysis and structure assessment by Q-TOF (quadrupole–time-of-flight) MS/MS. Correlations of the kinetic data with the known crystal structure are discussed for reactions with different cytokinins.

scholarly journals The 2:1 charge-transfer complex of 4,6-dimethyldibenzothiophene and 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane

IUCrData ◽  
2018 ◽  
Vol 3 (1) ◽  
Author(s):  
Takuya Fujii ◽  
Hideo Yamakado
Keyword(s):  
Charge Transfer ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Title Compound ◽  
Charge Transfer Complex ◽  
Membered Ring ◽  
Asymmetric Unit ◽  
Centroid Distance ◽  
A Charge ◽  
Tcnq Molecule

The title compound, 2C14H12S·C12N4F4, was obtained by using 4,6-dimethyldibenzothiophene (DMDBT) as an electron donor and 7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (F4TCNQ) as an electron acceptor. The asymmetric unit consists of one DMDBT molecule and one half of an F4TCNQ molecule, which lies on an inversion centre. In the crystal, the DMDBT and F4TCNQ molecules form a 2:1 unit via a charge-transfer interaction, with a centroid–centroid distance of 3.3681 (15) Å between the five-membered ring of DMDBT and the six-membered ring of F4TCNQ. An F...F contact [2.911 (1) Å] is also observed.

A charge-transfer salt composed of methyl viologen and hexacyanidoferrate(II)

2017 ◽  
Vol 73 (6) ◽  
pp. 476-480 ◽  
Author(s):  
Rikako Tanaka ◽  
Nobuyuki Matsushita
Keyword(s):  
Crystal Structure ◽  
Charge Transfer ◽  
Electron Acceptor ◽  
Methyl Viologen ◽  
Water Molecules ◽  
Asymmetric Unit ◽  
Hydrated Salt ◽  
Cyanide Ligands ◽  
A Charge

The methyl viologen dication, used under the name Paraquat as an agricultural reagent, is a well-known electron-acceptor species that can participate in charge-transfer (CT) interactions. The determination of the crystal structure of this species is important for accessing the CT interaction and CT-based properties. The title hydrated salt, bis(1,1′-dimethyl-4,4′-bipyridine-1,1′-diium) hexacyanidoferrate(II) octahydrate, (C12H14N2)2[Fe(CN)6]·8H2O or (MV)2[Fe(CN)6]·8H2O [MV2+ is the 1,1′-dimethyl-4,4′-bipyridine-1,1′-diium (methyl viologen) dication], crystallizes in the space group P21/c with one MV2+ cation, half of an [Fe(CN)6]4− anion and four water molecules in the asymmetric unit. The FeII atom of the [Fe(CN)6]4− anion lies on an inversion centre and has an octahedral coordination sphere defined by six cyanide ligands. The MV2+ cation is located on a general position and adopts a noncoplanar structure, with a dihedral angle of 40.32 (7)° between the planes of the pyridine rings. In the crystal, layers of electron-donor [Fe(CN)6]4− anions and layers of electron-acceptor MV2+ cations are formed and are stacked in an alternating manner parallel to the direction of the −2a + c axis, resulting in an alternate layered structure.

Determination of Epsilon Aminocaproic Acid Based on Charge Transfer Complexation with p-Nitrophenlol by Spectrophotometry

2020 ◽  
Vol 16 ◽  
Author(s):  
Sheng-Yun Li ◽  
Fang Tian
Keyword(s):  
Charge Transfer ◽  
Aminocaproic Acid ◽  
Concentration Limit ◽  
Official Method ◽  
Good Precision ◽  
Pharmaceutical Dosage Forms ◽  
Relative Standard ◽  
A Charge ◽  
Epsilon Aminocaproic Acid

: A spectrophotometry was investigated for the determination of epsilon aminocaproic acid (EACA) with p-nitrophenol (PNP). The method was based on a charge transfer (CT) complexation of this drug as n-electron donor with π-acceptor PNP. Experiment indicated that the CT complexation was carried out at room temperature for 10 minutes in dimethyl sulfoxide solvent. The spectrum obtained for EACA/PNP system showed the maximum absorption band at wavelength of 425 nm. The stoichiometry of the CT complex was found to be 1:1 ratio by Job’s method between the donor and the acceptor. Different variables affecting the complexation were carefully studied and optimized. At the optimum reaction conditions, Beer’s law was obeyed in a concentration limit of 1～6 µg mL-1. The relative standard deviation was less than 2.9%. The apparent molar absoptivity was determined to be 1.86×104 L mol-1cm-1 at 425 nm. The CT complexation was also confirmed by both FTIR and 1H NMR measurements. The thermodynamic properties and reaction mechanism of the CT complexation have been discussed. The developed method could be applied successfully for the determination of the studied compound in its pharmaceutical dosage forms with a good precision and accuracy compared to official method as revealed by t- and F-tests.

Fluorescence Quenching of Aminodiphenylamines with Chloromethanes

2002 ◽  
Vol 67 (8) ◽  
pp. 1154-1164 ◽  
Author(s):  
Nachiappan Radha ◽  
Meenakshisundaram Swaminathan
Keyword(s):  
Charge Transfer ◽  
Fluorescence Quenching ◽  
Ground State ◽  
Rate Constants ◽  
Quenching Mechanism ◽  
Quenching Rate ◽  
Charge Transfer Interaction ◽  
Electronically Excited ◽  
A Charge

The fluorescence quenching of 2-aminodiphenylamine (2ADPA), 4-aminodiphenylamine (4ADPA) and 4,4'-diaminodiphenylamine (DADPA) with tetrachloromethane, chloroform and dichloromethane have been studied in hexane, dioxane, acetonitrile and methanol as solvents. The quenching rate constants for the process have also been obtained by measuring the lifetimes of the fluorophores. The quenching was found to be dynamic in all cases. For 2ADPA and 4ADPA, the quenching rate constants of CCl4 and CHCl3 depend on the viscosity, whereas in the case of CH2Cl2, kq depends on polarity. The quenching rate constants for DADPA with CCl4 are viscosity-dependent but the quenching with CHCl3 and CH2Cl2 depends on the polarity of the solvents. From the results, the quenching mechanism is explained by the formation of a non-emissive complex involving a charge-transfer interaction between the electronically excited fluorophores and ground-state chloromethanes.

Charge-Transfer Intermediates in the Electrochemical Doping Mechanism of Conjugated Polymers

2020 ◽  
Author(s):  
Ilaria Bargigia ◽  
Lisa R. Savagian ◽  
Anna M. Österholm ◽  
John R. Reynolds ◽  
Carlos Silva
Keyword(s):  
Charge Transfer ◽  
Conjugated Polymers ◽  
Electrochemical Doping ◽  
Doping Mechanism
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