Transition Dipole Orientation of Linear Polyenes:  Semiempirical Models and Extrapolation to the Infinite Chain Limit

1999 ◽  
Vol 103 (14) ◽  
pp. 2251-2255 ◽  
Author(s):  
Robert R. Birge ◽  
Marek Z. Zgierski ◽  
Luis Serrano-Andres ◽  
Bruce S. Hudson
Keyword(s):  
Infinite Chain ◽  
Dipole Orientation ◽  
Transition Dipole ◽  
Linear Polyenes ◽  
Semiempirical Models

scholarly journals Probing intramolecular vibronic coupling through vibronic-state imaging

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Fan-Fang Kong ◽  
Xiao-Jun Tian ◽  
Yang Zhang ◽  
Yun-Jie Yu ◽  
Shi-Hao Jing ◽  
...  
Keyword(s):  
Single Molecule ◽  
Molecular Spectroscopy ◽  
Transition Density ◽  
Real Space ◽  
Vibronic Coupling ◽  
Vibronic State ◽  
Dipole Orientation ◽  
Transition Dipole ◽  
Franck Condon ◽  
Strong Dynamic

AbstractVibronic coupling is a central issue in molecular spectroscopy. Here we investigate vibronic coupling within a single pentacene molecule in real space by imaging the spatial distribution of single-molecule electroluminescence via highly localized excitation of tunneling electrons in a controlled plasmonic junction. The observed two-spot orientation for certain vibronic-state imaging is found to be evidently different from the purely electronic 0–0 transition, rotated by 90°, which reflects the change in the transition dipole orientation from along the molecular short axis to the long axis. Such a change reveals the occurrence of strong vibronic coupling associated with a large Herzberg–Teller contribution, going beyond the conventional Franck–Condon picture. The emergence of large vibration-induced transition charges oscillating along the long axis is found to originate from the strong dynamic perturbation of the anti-symmetric vibration on those carbon atoms with large transition density populations during electronic transitions.

Electronic Structure of Long Polyenes: States and Transition Dipoles

1989 ◽  
Vol 173 ◽  
Author(s):  
Bryan E. Kohler
Keyword(s):  
Electronic Structure ◽  
Repeat Unit ◽  
Excitation Energies ◽  
Transition Dipole ◽  
Maximum Value ◽  
Linear Polyenes ◽  
Highly Correlated ◽  
Chain Lengths ◽  
Effective Conjugation Length ◽  
Insight Into

ABSTRACTElectronic excitation energies and transition dipoles measured for symmetrically substituted linear polyenes (R-(CH=CH)N-R) with chain lengths n ranging from 2 to 8 are well fit by the functional form A+B/N. Extrapolation to the long chain limit correlates the band gap transition of polyacetylene with the polyene 11Ag to 11Bu transition. The amount by which the highly correlated polyene 21Ag state is lower than the 11Bu state increases with increasing chain length, extrapolating to roughly half of the 11Bu excitation energy. The 11Ag to 11Bu transition dipole magnitude per chain repeat unit attains a maximum value of 3.0 Debye at an effective conjugation length 5 double bonds.Careful studies on linear polyenes provides insight into the electronic structure of polyacetylene.

scholarly journals Identification of the Key Parameters for Horizontal Transition Dipole Orientation in Fluorescent and TADF Organic Light‐Emitting Diodes

2021 ◽  
pp. 2100677
Author(s):  
Francisco Tenopala‐Carmona ◽  
Oliver S. Lee ◽  
Ettore Crovini ◽  
Ana M. Neferu ◽  
Caroline Murawski ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Organic Light Emitting Diodes ◽  
Dipole Orientation ◽  
Transition Dipole ◽  
Light Emitting ◽  
Organic Light

Molecular Characterization of the Surface Excess Charge Layer in Droplets

2020 ◽  
Author(s):  
Victor Kwan ◽  
Styliani Consta
Keyword(s):  
Hydrogen Bonds ◽  
Surface Charge ◽  
Droplet Size ◽  
Chloride Ions ◽  
Total Charge ◽  
Excess Charge ◽  
Surface Excess ◽  
High Concentration ◽  
Dipole Orientation ◽  
Charge Layer

<div>Charged droplets play a central role in native mass spectrometry, atmospheric aerosols and in serving as micro-reactors for accelerating chemical reactions. The surface excess charge layer in droplets has often been associated with distinct chemistry. Using molecular simulations for droplets with Na+ and Cl- ions we have found that this layer is ≈ 1.5−1.7 nm thick and depending on the droplet size it includes 33%-55% of the total number of ions. Here, we examine the effect of droplet size and nature of ions in the structure of the surface excess charge layer by using molecular dynamics. We find that in the presence of simple ions the thickness of the surface excess charge layer is invariant not only with respect to droplet size but also with respect to the nature of the simple ions and it is not sensitive to fine details of different force fields used in our simulations.</div><div> In the presence of macroions the excess surface charge layer may extend to 2.0. nm. For the same droplet size, iodide and model hydronium ions show considerably higher concentration than the sodium and chloride ions. <br></div><div>We also find that differences in the average water dipole orientation in the presence of cations and anions in this layer are reflected in the charge distributions. Within the surface charge layer, the number of hydrogen bonds reduces gradually relative to the droplet interior where the number of hydrogen bonds is on the average 2.9 for droplets of diameter < 4 nm and 3.5 for larger droplets. The decrease in the number of hydrogen bonds from the interior to the surface is less pronounced in larger droplets. In droplets with diameter < 4 nm and high concentration of ions the charge of the ions is not compensated only by the solvent polarization charge but by the total charge that also includes the other free charge. This finding shows exceptions to the commonly made assumption that the solvent compensates the charge of the ions in solvents with very high dielectric constant. The study provides molecular insight into the bi-layer droplet structure assumed in the equilibrium partitioning model of C. Enke and assesses critical assumptions of the Iribarne-Thomson model for the ion-evaporation mechanism. <br></div>

Two-Dimensional Near-Infrared and Shortwave Infrared Molecular Aggregates: Taking Kasha’s Model to the Next Dimension

2019 ◽  
Author(s):  
Arundhati Deshmukh ◽  
Danielle Koppel ◽  
Chern Chuang ◽  
Danielle Cadena ◽  
Jianshu Cao ◽  
...  
Keyword(s):  
Near Infrared ◽  
Photophysical Properties ◽  
Satellite Telemetry ◽  
Transition Dipole Moment ◽  
Short Wave ◽  
Tissue Imaging ◽  
Transition Dipole ◽  
Deep Tissue Imaging ◽  
Excitonic States ◽  
Shortwave Infrared

Technologies which utilize near-infrared (700 – 1000 nm) and short-wave infrared (1000 – 2000 nm) electromagnetic radiation have applications in deep-tissue imaging, telecommunications and satellite telemetry due to low scattering and decreased background signal in this spectral region. However, there are few molecular species, which absorb efficiently beyond 1000 nm. Transition dipole moment coupling (e.g. J-aggregation) allows for redshifted excitonic states and provides a pathway to highly absorptive electronic states in the infrared. We present aggregates of two cyanine dyes whose absorption peaks redshift dramatically upon aggregation in water from ~ 800 nm to 1000 nm and 1050 nm with sheet-like morphologies and high molar absorptivities (e ~ 10<sup>5 </sup>M<sup>-1</sup>cm<sup>-1</sup>). To describe this phenomenology, we extend Kasha’s model for J- and H-aggregation to describe the excitonic states of <i> 2-dimensional aggregates</i> whose slip is controlled by steric hindrance in the assembled structure. A consequence of the increased dimensionality is the phenomenon of an <i>intermediate </i>“I-aggregate”, one which redshifts yet displays spectral signatures of band-edge dark states akin to an H-aggregate. We distinguish between H-, I- and J-aggregates by showing the relative position of the bright (absorptive) state within the density of states using temperature dependent spectroscopy. Our results can be used to better design chromophores with predictable and tunable aggregation with new photophysical properties.

Geometrically isomeric [Ir(iqbt)(ppy)(hpa)] complexes with differential molecule orientations for efficient near-infrared (NIR) polymer light-emitting diodes (PLEDs)

2021 ◽  
Vol 9 (36) ◽  
pp. 12068-12072
Author(s):  
Wentao Li ◽  
Jiaxiang Liu ◽  
Baowen Wang ◽  
Siyu Hou ◽  
Xingqiang Lü ◽  
...  
Keyword(s):  
Near Infrared ◽  
Light Emitting Diodes ◽  
Dipole Transition ◽  
Transition Dipole ◽  
Light Emitting ◽  
Horizontal Orientation ◽  
Polymer Light Emitting Diodes

Based on geometrical isomerisation of [Ir(C^N1)(C^N2)((N^O))]-tris-heteroleptic Ir(iii)-complexes, the augmented transition dipole transition (TMD) with a preferential horizontal orientation, which is beneficial for their NIR-phosphorescence, is reported.

Insight into the formation of H-bonds propagating the monomeric zinc complexes of a tridentate reduced Schiff base to form an infinite chain

CrystEngComm ◽  
2021 ◽  
Author(s):  
Mainak Karmakar ◽  
Antonio Frontera ◽  
Shouvik Chattopadhyay
Keyword(s):  
Schiff Base ◽  
Solid State ◽  
Dft Calculations ◽  
Zinc Complexes ◽  
Infinite Chain ◽  
State Structure ◽  
Computational Tools ◽  
Solid State Structure ◽  
Reduced Schiff Base ◽  
Insight Into

The formation of an infinite 1D assembly is governed by the H-bonding interactions in the solid state structure of the two zinc complexes. It has been analyzed energetically using DFT calculations and several computational tools.

Influence of metal phthalocyanine molecular orientation on charge separation at organic donor/acceptor interface

2021 ◽  
Author(s):  
Heeseon Lim ◽  
Sena Yang ◽  
Sang-Hoon Lee ◽  
Jung-Yong Lee ◽  
Yeunhee Lee ◽  
...  
Keyword(s):  
Solar Cell ◽  
Charge Separation ◽  
Molecular Orientation ◽  
Organic Solar Cell ◽  
Metal Phthalocyanine ◽  
Dipole Orientation ◽  
Highly Efficient ◽  
Donor Acceptor

To achieve a highly efficient organic solar cell (OPVs), control of molecular orientation is one of prime important factors, for interfacial dipole orientation and energy offset at donor/acceptor (D/A) interface...

A free-electron theory of conjugated molecules

1953 ◽  
Vol 49 (4) ◽  
pp. 650-658 ◽  
Author(s):  
J. Stanley Griffith
Keyword(s):  
Free Electron ◽  
Wave Functions ◽  
Electron Charge ◽  
Algebraic Equations ◽  
Electron Wave ◽  
Electron Theory ◽  
Conjugated Molecules ◽  
Electron Charge Density ◽  
Linear Polyenes ◽  
Alternant Hydrocarbons

ABSTRACTThe values of a free-electron eigenfunotion at the carbon nuclei of a conjugated hydrocarbon are found to satisfy a system of algebraic equations. These equations are similar in form to those obtained in the method known as the linear combination of atomic orbitale but only coincide with them for linear polyenes and benzene. The symmetry, degeneracy and energy of the eigenvectors of these free-electron equations correspond exactly to those of the free-electron wave functions found by the usual methods. From this correspondence, a theorem is deduced about the free-electron charge density in alternant hydrocarbons.

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