scholarly journals Layered Structures of Assembled Imine-Linked Macrocycles and Two-Dimensional Covalent Organic Frameworks Give Rise to Prolonged Exciton Lifetimes

2021 ◽  
Author(s):  
Waleed Helweh ◽  
Nathan Flanders ◽  
Shiwei Wang ◽  
Brian Phelan ◽  
Pyosang Kim ◽  
...  
Keyword(s):  
Excited State ◽  
Diffusion Processes ◽  
Transition Dipole Moment ◽  
Layered Structures ◽  
Structural Factors ◽  
Covalent Organic Frameworks ◽  
Transition Dipole ◽  
Exciton Dynamics ◽  
Optoelectronic Applications ◽  
Excited State Lifetimes

Ordered organic materials and assemblies have great potential to be tailored to have desirable properties for optoelectronic applications, such as long exciton lifetime and high directional exciton mobility. Framework materials, such as twodimensional covalent organic frameworks (2D COFs), as well as their truncated macrocyclic analogues, are versatile platforms to organize functional aromatic systems into designed assemblies and robust materials. Here we investigate the exciton dynamics in a 2D COF, its corresponding hexagonal macrocycle, and extended nanotubes comprised of stacked macrocycles. The excitonic behavior of these three systems provide an understanding of excitonic processes that occur in the plane of the covalently bonded 2D macromolecules and between layers of the nanotubes and 2D COF. The nanotube and analogous 2D COF exhibit longer excited-state lifetimes (~100 ps) compared to the individual, solvated macrocycles (<0.5 ps). These differences are attributed to the internal conversion facilitated by the internal motions of the imine linkages which are significantly reduced in the assembled macrocycles in the nanotube and 2D COF sheets in the layered structures. The exciton diffusion processes in the assembled nanotubes and 2D COF systems were characterized by the autocorrelations of the transition dipole moment of the excitons, giving the depolarization time constants for both systems to be ~1 ps. This work also reveals the anisotropic exciton dynamics related to the in-plane and inter-plane structural factors in these systems. These studies provide guidance for the design of future COF materials, where the longer excited state lifetimes imparted by assembly are beneficial for optoelectronic applications.

Excited-State Mixed Valence in a Diphenyl Hydrazine Cation:  Spectroscopic Consequences of Coupling and Transition Dipole Moment Orientation

2005 ◽  
Vol 109 (6) ◽  
pp. 1205-1215 ◽  
Author(s):  
Jenny V. Lockard ◽  
Jeffrey I. Zink ◽  
Dwight A. Trieber ◽  
Asgeir E. Konradsson ◽  
Michael N. Weaver ◽  
...  
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Mixed Valence ◽  
Transition Dipole Moment ◽  
Transition Dipole

The Determination of Molecular Quantities from Measurements on Macroscopic Systems.III. Electro-optical Absorption Measurements on Michler's Ketone

1982 ◽  
Vol 37 (12) ◽  
pp. 1409-1415 ◽  
Author(s):  
Wolfgang Liptay ◽  
Jürgen Becker
Keyword(s):  
Dipole Moment ◽  
Excited State ◽  
Optical Absorption ◽  
Dipole Moments ◽  
Transition Dipole Moment ◽  
Spherical Approximation ◽  
Approximation Model ◽  
Transition Dipole ◽  
Absorption Measurements

AbstractSome bulk quantities appropriate for the description of electro-optical absorption measurements on macroscopic systems are defined and their properties are discussed. Based on three molecular models (Lorentz model, Onsager model in spherical approximation and in ellipsoidal approximation) model molar quantities are introduced, which depend on intrinsic properties of the molecule (dipole moments and polarizabilities in the ground and excited state, transition dipole moment and transition polarizability). The relations will be applied for the evaluation of the results of electro-optical absorption measurements on Michler's ketone in cyclohexane in a wavenumber interval near 30 · 105 m-1 . The angles between the dipole moments in the ground and the excited state and the transition dipole moment will be determined; the magnitude of the dipole moment in the corresponding excited state is μaG = 30 · 10-30 Cm. The data show that the symmetry of a solute Michler's ketone molecule most probably corresponds, at least approximately, to the pointgroup Cs.

Ab Initio Design of Two-Photon Absorbing Materials

1999 ◽  
Vol 597 ◽  
Author(s):  
Paul N. Day ◽  
Kiet A. Nguyen ◽  
Ruth Pachter
Keyword(s):  
Excited State ◽  
Ab Initio ◽  
Nonlinear Optical ◽  
Dipole Moments ◽  
Transition Dipole Moment ◽  
Photon Absorption ◽  
Transition Dipole ◽  
Two Photon Absorption ◽  
Two Photon ◽  
Absorbing Materials

AbstractTwo-photon absorbing materials such as conjugated polyenes show promise as nonlinear optical materials. Prediction of two-photon absorption frequencies and cross-sections has been limited by the high level of ab initio calculations that must be carried out in order to accurately calculate excited state energies and transition dipole moments, by the size of many of the compounds of interest, and by the difficulty of handling condensed phase effects in the calculations. We have carried out geometry optimizations at the multi-configurational selfconsistent field level on a small polyene, hexatriene, both in the gas-phase and in solution, with the solvent effects being modeled by the effective fragment potential. The excited-state energies have been calculated by the multiconfigurational quasidegenerate perturbation theory. Transition dipole moment calculations have also been carried out, from which the two-photon absorption cross-section can be estimated. The results indicate that just one or two solvent molecules can have a large effect on the nonlinear optical properties of two-photon absorbing materials.

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.

Dibenzochrysene Enables Tightly Controlled Docking and Stabilizes Photoexcited States in Dual-Pore Covalent Organic Frameworks

2019 ◽  
Author(s):  
Torben Sick ◽  
Niklas Keller ◽  
Nicolai Bach ◽  
Andreas Koszalkowski ◽  
Julian Rotter ◽  
...  
Keyword(s):  
Molecular Docking ◽  
Photophysical Properties ◽  
Visible Spectrum ◽  
Large Family ◽  
Building Blocks ◽  
Band Gaps ◽  
Docking Site ◽  
Covalent Organic Frameworks ◽  
Connected Node ◽  
Optoelectronic Applications

Covalent organic frameworks (COFs), consisting of covalently connected organic building units, combine attractive features such as crystallinity, open porosity and widely tunable physical properties. For optoelectronic applications, the incorporation of heteroatoms into a 2D COF has the potential to yield desired photophysical properties such as lower band gaps, but can also cause lateral offsets of adjacent layers. Here, we introduce dibenzo[g,p]chrysene (DBC) as a novel building block for the synthesis of highly crystalline and porous 2D dual-pore COFs showing interesting properties for optoelectronic applications. The newly synthesized terephthalaldehyde (TA), biphenyl (Biph), and thienothiophene (TT) DBC-COFs combine conjugation in the a,b-plane with a tight packing of adjacent layers guided through the molecular DBC node serving a specific docking site for successive layers. The resulting DBC-COFs exhibit a hexagonal dual-pore kagome geometry, which is comparable to COFs containing another molecular docking site, namely 4,4′,4″,4‴-(ethylene-1,1,2,2-tetrayl)-tetraaniline (ETTA). In this context, the respective interlayer distances decrease from about 4.60 Å in ETTA-COFs to about 3.6 Å in DBC-COFs, leading to well-defined hexagonally faceted single crystals sized about 50-100 nm. The TT DBC-COFs feature broad light absorption covering large parts of the visible spectrum, while Biph DBC-COF shows extraordinary excited state lifetimes exceeding 10 ns. In combination with the large number of recently developed linear conjugated building blocks, the new DBC tetra-connected node is expected to enable the synthesis of a large family of strongly p-stacked, highly ordered 2D COFs with promising optoelectronic properties.

scholarly journals Ê-μ-V Correlation In One-Colour Photolysis/Ionization Of Tert-Butyl Nitrite

1990 ◽  
Vol 10 (3) ◽  
pp. 197-206 ◽  
Author(s):  
P. Marcus ◽  
I. Platzner ◽  
I. Bar ◽  
S. Rosenwaks
Keyword(s):  
Transition Dipole Moment ◽  
Laser Polarization ◽  
Experimental Conditions ◽  
Transition Dipole ◽  
Vector Correlation ◽  
Peak Splitting ◽  
Tert Butyl ◽  
Spatial Velocity ◽  
Fragment Peak ◽  
532 Nm

An anisotropic spatial velocity distribution was observed for NO+ produced following one-color photolysis/ionization of tert-butyl nitrite (TBN) by a pulsed polarized laser at 266, 355 and 532 nm in a time-of-flight mass spectrometer. The dependence of the NO+ fragment mass peak profile on the wavelength and on the polarization was monitored. The most striking feature is the varying fragment peak splitting obtained under the same experimental conditions by changing the laser polarization direction. This phenomenon is a result of the vector correlation between the laser polarization,Ê, at a given wavelength, the electronic transition dipole moment of TBN,μ, and the direction of the NO fragment velocity, v. The dynamics of the photodissociation process and, in particular, its directional properties are discussed in view of these results.

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