Theoretical Prediction of the Donor/Acceptor Site-Dependence on First Hyperpolarizabilities in Conjugated Systems Containing Azomethine Bonds

1992 ◽  
Vol 291 ◽  
Author(s):  
Azuma Matsuura ◽  
Tomoaki Hayano
Keyword(s):  
Considerable Effect ◽  
Acceptor Site ◽  
Pockels Effect ◽  
Conjugated Molecules ◽  
No Donors ◽  
Electro Optic ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Site Dependence ◽  
The Relationship

ABSTRACTWe calculated frequency-dependent first hyperpolarizabilities for electro-optic Pockels effect, β(ω; 0, ω), in π-conjugated molecules containing azomethine bonds using the CNDO/S-CI sum-over-states method. First, we examined the dependence of static β on formulas for the two-center Coulomb integral, γAB. The choice of the γAB formula has little effect on the relative β value, but a considerable effect on the absolute value. Then we investigated the relationship between the magnitude of β(ω; 0, ω) and the donor/acceptor substitution sites. We found that the molecule with no donors or acceptors can be divided into donor and acceptor regions whose existence causes the donor/acceptor site-dependence of β(ω; 0, ω).

The Investigation of Donor and Acceptor States in the Nanoparticles of PbI2 Layered Semiconductor

1996 ◽  
Vol 452 ◽  
Author(s):  
E. Lifshitz
Keyword(s):  
Donor Site ◽  
Sol Gel ◽  
Spin Lattice Relaxation ◽  
Acceptor Site ◽  
Relaxation Processes ◽  
Nonradiative Recombination ◽  
Layered Semiconductor ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Optically Detected

AbstractThe nanoparticles of PbI2 layered semiconductor, embedded in Sio2 films, were prepared by the sol-gel method. The low-temperature luminescence of PbI2 nanoparticles consists of a series of exciton lines in the region of ∼2.5eV and additional donor-acceptor recombination luminescent bands at lower energies, centered at 2.44eV (Green) and 2.07 eV (red), respectively. This paper reports the investigation of the nonexcitonic transitions, associated with of the Green and Red bands. The correlation between donor-acceptor recombination emission processes and lattice imperfections was examine, utilizing optically detected magnetic resonance (ODMR) spectroscopy. The results identified the following imperfection sites of both the Green and Red bands: an acceptor site associates with an isotropie Lead vacancy defect, [V]Pb2+ and a donor site, associate with an anisotropie Iodine vacancy, [V°]jodine. However, the results pointed on differences in relaxation processes of these bands. The relaxation processes correspond to the existence of competitive nonradiative recombination, spin-lattice relaxation and thermalization among the spin substrates. Thus, the results suggest that the Red band corresponds to stoichiometric defects at the surface, while the Green band corresponds to the same stoichiometric defects at the interior part of the nanoparticles.

scholarly journals Donor/Acceptor Properties of Purine and Рyrimidine Bases

2017 ◽  
Author(s):  
Nataliya Obernikhina ◽  
Marina Kachaeva ◽  
Volodymir Shchodryi ◽  
Yaroslav Prostota ◽  
Oleksiy Kachkovsky ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Energy Gap ◽  
Dna Bases ◽  
Frontier Molecular Orbitals ◽  
Fundamental Characteristic ◽  
Conjugated Molecules ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Donor Ability ◽  
The Difference

We have studied the relative positions of the frontier levels determine the main electronic properties and reaction ability, there is important necessity to compare the MO of the purine and рyrimidine bases: adenine (A), guanine (G), cytosine (C), thymine (T) and uracil (U). The donor and acceptor properties are the fundamental characteristic of the conjugated molecules and can be quantitatively estimated by relative positions of the frontier molecular orbitals. The MO’s energies can be estimated experimentally or quantum-chemically. Analysis of the relative position of the frontier levels (calibrated by the energy gap) enables the investigation of the donor/acceptor properties of the RNA/DNA bases more detailed. The index φ0 is proposed for the quantitative quantum-chemical estimation of the donor ability of the conjugated molecules: it points on the shifting of the energy gap relative to the reference electron balanced system. The RNA/DNA bases divided strictly by two groups: predominantly donors (φ0 > 0.5) and predominantly acceptors (φ0 > 0.5). Each representative base of the first group forms the stable base pair the representative base of the second group the difference of indices Δφ0 should be optimal to enables the DNA replication.

scholarly journals Charge–Transfer Fluorescence and Room-Temperature Phosphorescence from a Bisamide-Based Derivative

Crystals ◽  
2021 ◽  
Vol 11 (11) ◽  
pp. 1370
Author(s):  
Chengjian Li ◽  
Chaozheng Zhuo ◽  
Jingwei Sun ◽  
Mi Ouyang
Keyword(s):  
Charge Transfer ◽  
Room Temperature ◽  
Luminescent Properties ◽  
Luminescent Materials ◽  
Room Temperature Phosphorescence ◽  
Single Crystal Structures ◽  
Singlet States ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
The Relationship

The development of organic luminescent materials with bimodal emissions of both fluorescence and room-temperature phosphorescent (RTP) remains a challenge. The investigation of the relationship between fluorescence and RTP performance is especially rare. In this work, we obtained an organic luminescent molecule, 1,4-phenylenebis((9H-carbazol-9-yl)methanone) (PBCM), which exhibits bimodal emissions of cyan fluorescence and yellow RTP in its crystalline state through adopting an electron donor–acceptor–donor (D–A–D) structure. The charge–transfer (CT) effects in the bimodal luminescent properties of PBCM, as well as the single-crystal structures and thermal properties, were investigated. It was found that the CT effect in the singlet states effectively reduces the ∆Est and promotes the ISC processes, resulting in an efficient phosphorescence of PBCM at room temperature. In addition, many strong intermolecular interactions are formed between the donor and acceptor parts of adjacent molecules, leading to the rigid configurations and compact packing of molecules in crystals, which was also confirmed to facilitate the efficient bimodal emissions of PBCM.

The Relationship Between Second-Order Nonlinear Optical Properties And Ground-State Polarization

1993 ◽  
Vol 328 ◽  
Author(s):  
Grant Bourhill ◽  
Lap-Tak Cheng ◽  
Ging Lee ◽  
Seth R. Marder ◽  
Joseph W. Perry ◽  
...  
Keyword(s):  
Ground State ◽  
Second Harmonic ◽  
Solvent Polarity ◽  
Second Order ◽  
X Ray Diffraction ◽  
H Nmr ◽  
Electro Optic ◽  
Theoretical Predictions ◽  
Donor Acceptor ◽  
The Relationship

ABSTRACTA review is presented describing our recent work to correlate the first hyperpolarizability, β, of organic materials with the molecular parameter bond length alternation (BLA). Donor-acceptor polyenes displaying a wide BLA range were synthesized. For a particular chromophore, BLA was fine-tuned by varying solvent polarity. The degree of BLA was analyzed by X-ray diffraction, 1H-NMR and electronic absorption spectroscopy. Non-resonant, solvent-dependent, electric field induced second harmonic generation (EFISH) Measurements were performed to probe the variation in the second-order nonlinearity as a function of ground-state polarization. The resulting trend, which is fully consistent with theoretical predictions, identified chromophores possessing optimized positive and negative hyperpolarizabilities. An optimized chromophore was incorporated in a polymer matrix and poled. The resulting electro-optic coefficient was found to be significantly enhanced relative to the longer chromophore Disperse Red 1.

scholarly journals Thermochromic aggregation-induced dual phosphorescence via temperature-dependent sp3-linked donor-acceptor electronic coupling

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Tao Wang ◽  
Zhubin Hu ◽  
Xiancheng Nie ◽  
Linkun Huang ◽  
Miao Hui ◽  
...  
Keyword(s):  
Excited State ◽  
Room Temperature ◽  
Electronic Coupling ◽  
Temperature Dependent ◽  
Molecular Systems ◽  
Donor And Acceptor ◽  
Theoretical Investigations ◽  
Donor Acceptor ◽  
And Control ◽  
Two Temperature

AbstractAggregation-induced emission (AIE) has proven to be a viable strategy to achieve highly efficient room temperature phosphorescence (RTP) in bulk by restricting molecular motions. Here, we show that by utilizing triphenylamine (TPA) as an electronic donor that connects to an acceptor via an sp3 linker, six TPA-based AIE-active RTP luminophores were obtained. Distinct dual phosphorescence bands emitting from largely localized donor and acceptor triplet emitting states could be recorded at lowered temperatures; at room temperature, only a merged RTP band is present. Theoretical investigations reveal that the two temperature-dependent phosphorescence bands both originate from local/global minima from the lowest triplet excited state (T1). The reported molecular construct serves as an intermediary case between a fully conjugated donor-acceptor system and a donor/acceptor binary mix, which may provide important clues on the design and control of high-freedom molecular systems with complex excited-state dynamics.

scholarly journals Electro-Optic Control of Lithium Niobate Bulk Whispering Gallery Resonators: Analysis of the Distribution of Externally Applied Electric Fields

Crystals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 298
Author(s):  
Yannick Minet ◽  
Hans Zappe ◽  
Ingo Breunig ◽  
Karsten Buse
Keyword(s):  
Lithium Niobate ◽  
Electric Field ◽  
Electric Fields ◽  
Frequency Comb ◽  
Parametric Oscillation ◽  
Pockels Effect ◽  
Optical Mode ◽  
Cylindrical Resonator ◽  
Whispering Gallery ◽  
Electro Optic

Whispering gallery resonators made out of lithium niobate allow for optical parametric oscillation and frequency comb generation employing the outstanding second-order nonlinear-optical properties of this material. An important knob to tune and control these processes is, e.g., the linear electro-optic effect, the Pockels effect via externally applied electric fields. Due to the shape of the resonators a precise prediction of the electric field strength that affects the optical mode is non-trivial. Here, we study the average strength of the electric field in z-direction in the region of the optical mode for different configurations and geometries of lithium niobate whispering gallery resonators with the help of the finite element method. We find that in some configurations almost 100% is present in the cavity compared to the ideal case of a cylindrical resonator. Even in the case of a few-mode resonator with a very thin rim we find a strength of 90%. Our results give useful design considerations for future arrangements that may benefit from the strong electro-optic effect in bulk whispering gallery resonators made out of lithium niobate.

scholarly journals Supramolecular Systems Containing B–N Frustrated Lewis Pairs of Tris(pentafluorophenyl)borane and Triphenylamine Derivatives

2021 ◽  
Vol 03 (02) ◽  
pp. 174-183
Author(s):  
P. Chidchob ◽  
S. A. H. Jansen ◽  
S. C. J. Meskers ◽  
E. Weyandt ◽  
N. P. van Leest ◽  
...  
Keyword(s):  
Materials Science ◽  
Supramolecular Polymers ◽  
Frustrated Lewis Pairs ◽  
Paramagnetic Resonance ◽  
Donor And Acceptor ◽  
Donor Acceptor ◽  
Noncovalent Polymers ◽  
Electron Paramagnetic ◽  
Supramolecular Polymerization ◽  
Lewis Pairs

The introduction of a chemical additive to supramolecular polymers holds high potential in the development of new structures and functions. In this regard, various donor- and acceptor-based molecules have been applied in the design of these noncovalent polymers. However, the incorporation of boron–nitrogen frustrated Lewis pairs in such architectures is still rare despite their many intriguing properties in catalysis and materials science. The limited choices of suitable boron derivatives represent one of the main limitations for the advancement in this direction. Here, we examine the use of the commercially available tris(pentafluorophenyl)borane with various triphenylamine derivatives to create supramolecular B–N charge transfer systems. Our results highlight the importance of a proper balance between the donor/acceptor strength and the driving force for supramolecular polymerization to achieve stable, long-range ordered B–N systems. Detailed analyses using electron paramagnetic resonance and optical spectroscopy suggest that tris(pentafluorophenyl)borane displays complex behavior with the amide-based triphenylamine supramolecular polymers and may interact in dimers or larger chiral aggregates, depending on the specific structure of the triphenylamines.

INFLUENCE OF THE SUPPRESSION OF SELF-DISCREPANT THOUGHTS ON THE VIVIDNESS OF PERCEP TION OF AUDITORY ILLUSIONS

2003 ◽  
Vol 31 (1) ◽  
pp. 33-44 ◽  
Author(s):  
José M. García-Montes ◽  
Marino Pérez-Álvarez ◽  
Ángel M. Fidalgo
Keyword(s):  
Auditory Stimulation ◽  
Considerable Effect ◽  
Psychological Therapy ◽  
Auditory Hallucinations ◽  
Clinical Population ◽  
Self Discrepancy ◽  
The Relationship ◽  
Percep Tion ◽  
Different Levels

Based on the relationship between cognitive intrusions and auditory hallucinations established by Morrison and Baker (2000) and Morrison, Haddock and Tarrier (1995) the present study examines the possible effect of the repeated suppression of self-discrepant thoughts on the vividness of auditory illusions in a sample from a non-clinical population. Sixty-one participants were randomly assigned to a suppression of thoughts group (n = 31) or a focalization of thoughts group (n = 30) with different levels of self-discrepancy. After carrying out the task over a period of 48 hours, participants were presented with non-vocal auditory stimulation and asked to state whether they heard any verbalizations, and if so, how clearly. Results show how the repeated suppression of self-discrepant thoughts has a considerable effect on the vividness of illusions (F(1, 50) = 16.09; p < 0.001). The implications of these results for psychological therapy are analysed, with special emphasis on the importance of a research line based on acceptance.

scholarly journals An investigation of the interrelationships between linear and nonlinear polarizabilities and bond-length alternation in conjugated organic molecules

1993 ◽  
Vol 90 (23) ◽  
pp. 11297-11301 ◽  
Author(s):  
C B Gorman ◽  
S R Marder
Keyword(s):  
Bond Length ◽  
Organic Molecules ◽  
Computational Method ◽  
Bond Length Alternation ◽  
Conjugated Molecules ◽  
Conjugated Organic Molecules ◽  
Alpha Beta ◽  
Relationship Of ◽  
The Relationship ◽  
Observable Parameter

A computational method was devised to explore the relationship of charge separation, geometry, molecular dipole moment (mu), polarizability (alpha), and hyperpolariz-abilities (beta, gamma) in conjugated organic molecules. We show that bond-length alternation (the average difference in length between single and double bonds in the molecule) is a key structurally observable parameter that can be correlated with hyperpolarizabilities and is thus relevant to the optimization of molecules and materials. By using this method, the relationship of bond-length alternation, mu, alpha, beta, and gamma for linear conjugated molecules is illustrated, and those molecules with maximized alpha, beta, and gamma are described.

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