scholarly journals On Hyperfine and Fine Structure of Excited Charge-Transfer-Complexes

1976 ◽  
Vol 31 (11) ◽  
pp. 1324-1332 ◽  
Author(s):  
H. Möhwald ◽  
A. Böhm
Keyword(s):  
Charge Transfer ◽  
Theoretical Calculations ◽  
Esr Spectra ◽  
Charge Transfer Complexes ◽  
Zero Field ◽  
Phonon Coupling ◽  
Zero Field Splitting ◽  
Triplet Energy ◽  
Crystalline Complex ◽  
Ct Complexes

Abstract The charge-transfer (CT)-crystal naphthalene (N)-1,2,4,5-tetracyanobenzene (TCNB) was doped with various guest acceptors. CT-complexes of these acceptors with N are formed acting as a triplet energy trap in the crystal. This provides a method to investigate oriented CT-complexes ESR-spectroscopically. In favorable cases the hyperfine structure (Hfs) in the ESR-spectra can be resolved and interpreted. The Hfs of the complexes N-hexacyanobenzene and N-pentacyano-toluene show that in the crystalline complex the triplet electrons are distributed over no more than two molecules. This finding suggests a strong exciton-phonon-coupling which causes a breakdown of the inversion symmetry upon excitation. The spectra of naphthalene-s-trinitrobenzene (TNB) yield the spin density on the three equivalent protons of TNB and demonstrate that the triplet electrons are also equally distributed over the three nitrogen atoms.As further systems, complexes of extremely large CT-character, c12, in the triplet state are studied (e. g. N-chloranil).The data obtained from the measurements of the Hfs-and of the zero-field-splitting (ZFS) -parameters are compared, proving that previous models and approximations in deriving c12 are essentially correct. It is also shown that the ZFS-parameter D (A+D+) of the hypothetical purely ionic state is negative and for different complexes its value is very close to that obtained in earlier theoretical calculations (-0.027 cm-1).

scholarly journals Mobile and Trapped Triplet States in Single Crystals of Charge Transfer Complexes

1974 ◽  
Vol 29 (8) ◽  
pp. 1216-1228 ◽  
Author(s):  
H. Möhwald ◽  
E. Sackmann
Keyword(s):  
Charge Transfer ◽  
Delayed Fluorescence ◽  
Charge Transfer Complexes ◽  
Zero Field ◽  
Triplet States ◽  
Zero Field Splitting ◽  
Triplet Energy ◽  
Molecular Arrangement ◽  
Ct Complexes ◽  
Triplet Excitons

Homogeneously doped crystals of charge transfer (CT-) complexes were grown by incorporating aromatic guest donors in host CT-crystals. The host crystals contained 1,2.4,5-tetracyanobenzene (TCNB) as acceptor and deuterated aromatic electron donors. By using such doped crystals CT complexes in a well defined configuration may be studied. The triplet states of the guest complexes were used as ESR spectroscopic probes in order to determine the molecular arrangement in the host lattice. The zero-field-splitting (ZFS) parameters, D and E, of the triplet energy traps were determined and the degree of electron derealization in the triplet state was calculated from these values. In some cases a very strong guest host interaction (multicomplex formation) was established. A method for the determination of CT-triplet energies is described (accuracy 200 cm-1) . The phosphorescence spectrum of the anthracene-TCNB complex was obtained from the delayed emission spectra of different anthracene doped CT-crystals. The vibronic structure is identical to that of anthracene, while the O-O-band of the complex is blue shifted by 600 cm-1. It is shown that the undoped anthracene-TCNB crystal exhibits P-type delayed fluorescence and that the triplet exciton diffusion in this crystal is nearly temperature independent. In the undoped biphenyl-TCNB crystal E-type delayed fluorescence originating from the thermal depopulation of the mobile triplet excitons is established. The remarkable differences of the two types of triplet excitons are interpreted in terms of the different polarity in the triplet states of the two CT-crystals.

scholarly journals Charge Transfer Complexes of Ketotifen with 2,3-Dichloro-5,6-dicyano-p-benzoquinone and 7,7,8,8-Tetracyanoquodimethane: Spectroscopic Characterization Studies

Molecules ◽  
2021 ◽  
Vol 26 (7) ◽  
pp. 2039
Author(s):  
Gamal A. E. Mostafa ◽  
Ahmed Bakheit ◽  
Najla AlMasoud ◽  
Haitham AlRabiah
Keyword(s):  
Charge Transfer ◽  
Spectroscopic Characterization ◽  
Molar Ratio ◽  
Charge Transfer Complexes ◽  
Physical Parameters ◽  
Spectrophotometric Methods ◽  
Theoretical Approaches ◽  
The Stability ◽  
Ct Complexes

The reactions of ketotifen fumarate (KT) with 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as π acceptors to form charge transfer (CT) complexes were evaluated in this study. Experimental and theoretical approaches, including density function theory (DFT), were used to obtain the comprehensive, reliable, and accurate structure elucidation of the developed CT complexes. The CT complexes (KT-DDQ and KT-TCNQ) were monitored at 485 and 843 nm, respectively, and the calibration curve ranged from 10 to 100 ppm for KT-DDQ and 2.5 to 40 ppm for KT-TCNQ. The spectrophotometric methods were validated for the determination of KT, and the stability of the CT complexes was assessed by studying the corresponding spectroscopic physical parameters. The molar ratio of KT:DDQ and KT:TCNQ was estimated at 1:1 using Job’s method, which was compatible with the results obtained using the Benesi–Hildebrand equation. Using these complexes, the quantitative determination of KT in its dosage form was successful.

One-dimensionality and neutral-to-ionic transition of some mixed-stack charge-transfer complexes

2002 ◽  
Vol 12 (9) ◽  
pp. 357-360
Author(s):  
M. Buron ◽  
E. Collet ◽  
M. H. Lemée-Cailleau ◽  
H. Cailleau ◽  
T. Luty ◽  
...  
Keyword(s):  
Phase Transition ◽  
Charge Transfer ◽  
Charge Transfer Complexes ◽  
X Ray Diffraction ◽  
One Dimensional ◽  
Giant Dielectric ◽  
Ionic Transition ◽  
The One ◽  
Ct Complexes ◽  
Dimerization Process

Mixed-stack charge-transfer (CT) complexes undergoing the neutral-ionic (N-I) phase transition are molecular materials formed of stacks where electron donor (D) and acceptor (A) molecules regularly alternate. In the N phase, the CT is low and molecules are situated on inversion centers, while in the I phase, the increase of CT is accompanied by a lattice distortion (dimerization process and symmetry breaking). The one-dimensional (1D) architecture triggers the chain multistability by stabilizing lattice-relaxed (LR)-CT excitations ...D° A° D° A° $(D^+A^-)(D^+A^-)(D^+A^-)$ Do A" D° A° D°... These 1D nano-scale objects are at the heart of the equilibrium N-I phase transition and govern the fascinating physical properties such as giant dielectric response or photo-induced phase transformations. In this contribution, the 1D character of these critical excitations will be demonstrated by direct observation using high resolution X-Ray diffraction.

Charge Transfer Complexes of N-Arylcarbamates with π-Acceptors

1987 ◽  
Vol 42 (3) ◽  
pp. 284-288 ◽  
Author(s):  
Aboul-fetouh E. Mourad
Keyword(s):  
Charge Transfer ◽  
Electron Density ◽  
Nmr Spectra ◽  
Charge Transfer Complexes ◽  
H Nmr ◽  
Ct Complexes

The charge-transfer (CT) complexes of some N-arylcarbamates as donors with a number of π-acceptors have been studied spectrophotometrically. The Lewis basicities of the N-arylcarbamates as well as the types of interactions are discussed. The 1H-NMR spectra of some CT complexes with both 2,3-dichloro-5,6-dicyanobenzoquinone (DDQ) and 7,7,8,8 tetracyanoquinodimethane (TCNQ) indicate a decrease of the electron density on the donor part of the complex.

Charge Transfer Complexes of Aromatic Nitrocompounds with Disubstituted Naphthalenes. I.Spectroscopic Investigation of the Donor Behaviour of the 2,6- and 23-Dimethylnaphthalene

1984 ◽  
Vol 39 (12) ◽  
pp. 1274-1278 ◽  
Author(s):  
M. H. Abdel-Kader ◽  
R. M. Issa ◽  
M. M. Ayad ◽  
M. S. Abdel-Mottaleb
Keyword(s):  
Charge Transfer ◽  
Spectral Characteristics ◽  
Charge Transfer Complexes ◽  
Element Analysis ◽  
H Nmr ◽  
Aromatic Nitrocompounds ◽  
Donor Acceptor ◽  
The Difference ◽  
Donor Behaviour ◽  
Ct Complexes

The charge transfer complexes of 2,3- (I) and 2,6-Dimethylnaphthalenes (II) as electron donors with tri- and di-nitrobenzenes as electron acceptors are prepared and investigated by element analysis, IR. 1H nmr and electronic absorption spectroscopy. The results showed that I yields CT complexes of 1:1 type only while II is capable of forming 1 : 1 and 1 : 2 (donor: acceptor) compounds. The spectral characteristics of the CT complexes are pointed out and discussed. The difference in the donor behaviour between I and II is explained in the light of PPP-MO calculations.

Organic charge-transfer complexes for the selective accommodation of aromatic isomers using anthracene derivatives and TCNQ

2016 ◽  
Vol 40 (6) ◽  
pp. 5277-5284 ◽  
Author(s):  
Arshad Khan ◽  
Mingliang Wang ◽  
Rabia Usman ◽  
Jiao Lu ◽  
Hao Sun ◽  
...  
Keyword(s):  
Charge Transfer ◽  
Charge Transfer Complexes ◽  
Anthracene Derivatives ◽  
Ct Complexes

Four organic-charge transfer (CT) complexes (Ct1–Ct4) have been reported. Ct1 discerns p-xylene in the presence of a xylene mixture.

scholarly journals Über die Bildung von Molekülkomplexen bei der Feldionisation organischer Moleküle

1971 ◽  
Vol 26 (12) ◽  
pp. 2063-2066
Author(s):  
H. D. Beckey ◽  
M. D. Migahed
Keyword(s):  
Charge Transfer ◽  
Hydrogen Bonds ◽  
Sandwich Structure ◽  
Mass Spectra ◽  
Field Ionization ◽  
Charge Transfer Complexes ◽  
Ionization Mass ◽  
Organic Substances ◽  
Ct Complexes

Hetero-dimer ions are observed in the field ionization mass spectra of aniline-nitrobenzene mixtures, and also in mixtures of some other organic substances which yield charge-transfer complexes in solutions. It is shown that the structure of the hetero-dimer ions is different from the sandwich structure of the corresponding CT-complexes in solutions. Arguments are given for assuming hydrogen bonds between the components of the complexes, with an additional weak CT-bond

Characterization of the Phenanthrene-Tetrachlorophthalic Anhydride (P/TCPA) 1:1 Charge-Transfer Crystal: Spectroscopic and Structural Investigations

1987 ◽  
Vol 42 (6) ◽  
pp. 622-629 ◽  
Author(s):  
J. Krzystek ◽  
J. U. von Schütz ◽  
H. C Wolf ◽  
R.-D. Stigler ◽  
J. J. Stezowski
Keyword(s):  
Charge Transfer ◽  
Low Temperature ◽  
Structural Model ◽  
Emission Spectra ◽  
Optical Emission ◽  
Delayed Fluorescence ◽  
Zero Field ◽  
Zero Field Splitting ◽  
Structural Investigations ◽  
Space Group

The 1:1 phenanthrene-tetrachlorophthalic anhydride (P/TCPA) charge-transfer complex crystalizes with monoclinic symmetry, space group P21, with two magnetically inequivalent stacks in the unit cell. The noncentrosymmetric space group is very unusual for CT-complexes. The optical emission spectra at low temperature are characterized by a strong CT phosphorescence and a weak CT fluorescence and delayed fluorescence.The S1 band lies at 22 800 ± 100 cm-1, the T1 band at 21 200 ± 100 cm-1. Above 15 K triplet excitons, moving along the stacks are revealed by ESR. They have a CT character of about 30%, coinciding with that of the shallow X-traps found by ODMR at low temperatures. A further trap, with zero-field-splitting (zfs) parameters of D = ± 0.0617, E = + 0.0116 cm-1 has a much larger CT character of 50% as found in the isolated complex in low-temperature glass [1]. A structural model is proposed.

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