9 research outputs found
Diâ and TetracyanoâSubstituted PyreneâFused Pyrazaacenes: Aggregation in the Solid State
Means to stream: Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown, and the crystal packing was studied by XRD and DFT calculations of transfer integrals and reorganization energies with a view to their possible use as n-type semiconductors.
Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport
Quinoxalinophenanthrophenazine Based Cruciforms
Quinoxalinophenanthrophenazines (QPPs) and related structures are an emerging class of stable fused N-heteropolycyclic aromatics. By vertical attachment of aromatic substituents at the pyrene core, cruciform QPPs are accessible, which open new opportunities to adjust HOMO and LUMO levels of the QPPs nearly independent from each other.
A series of cruciform aryl-substituted quinoxalinophenanthrophenazine derivatives (QPPs) was synthesized through Suzuki-Miyaura cross-coupling of a 2,7-diborylated pyrene tetraketal building block. The QPPs were analyzed for their optoelectronic properties by absorption and emission spectroscopy, cyclic voltammetry and quantum-chemical calculations. The solid-state packing was investigated as well and evaluated for its charge transport properties by calculated charge transfer integrals
Triptycene EndâCapped Benzothienobenzothiophene and Naphthothienobenzothiophene
Previously it was demonstrated that triptycene endâcapping can be used as a crystal engineering strategy to direct the packing of quinoxalinophenanthrophenazines (QPPs) towards cofacially stacked Ï dimers with large molecular overlap resulting in high charge transfer integrals. Remarkably, this packing motif was formed under different crystallization conditions and with a variety of derivatives bearing additional functional groups or aromatic substituents. Benzothienobenzothiophene (BTBT) and its derivatives are known as some of the best performing compounds for organic fieldâeffect transistors. Here, the triptycene endâcapping concept is introduced to this class of compounds and polymorphic crystal structures are investigated to evaluate the potential of triptycene endâcaps as synthons for crystal engineering
Two Dimensional Triptycene EndâCapping and Its Influence on the SelfâAssembly of Quinoxalinophenanthrophenazines â
In this report we investigated two-dimensionally triptycene end-capped QPPs in terms of their solution and solid-state behavior. For this purpose, a triphenylene based ortho-diamine decorated with two triptycenyl units as well as a phenylene diamine with two non-annulated triptycene units have been synthesized. Sequences of condensation reactions with a pyrene-based tetraketone and ortho-diamines yielded a series of QPPs and UV/Vis investigations of the corresponding compounds led to the conclusion, that the QPPs form dimers in solution, which was further supported by MALDI-TIMS-TOF-MS. Single-crystal X-ray analysis of the triply and quadruply triptycene end-capped QPPs furthermore showed short Ï-Ï-distances of 3.3â3.4 Ă
and a perfect shape match during the dimerization of the triply triptycenyl end-capped QPP making it possible synthon fo
Interplay of structural dynamics and electronic effects in an engineered assembly of pentacene in a metalâorganic framework
Charge carrier mobility is an important figure of merit to evaluate organic semiconductor (OSC) materials. In aggregated OSCs, this quantity is determined by inter-chromophoric electronic and vibrational coupling. These key parameters sensitively depend on structural properties, including the density of defects. We have employed a new type of crystalline assembly strategy to engineer the arrangement of the OSC pentacene in a structure not realized as crystals to date. Our approach is based on metalâorganic frameworks (MOFs), in which suitably substituted pentacenes act as ditopic linkers and assemble into highly ordered Ï-stacks with long-range order. Layer-by-layer fabrication of the MOF yields arrays of electronically coupled pentacene chains, running parallel to the substrate surface. Detailed photophysical studies reveal strong, anisotropic inter-pentacene electronic coupling, leading to efficient charge delocalization. Despite a high degree of structural order and pronounced dispersion of the 1D-bands for the static arrangement, our experimental results demonstrate hopping-like charge transport with an activation energy of 64 meV dominating the band transport over a wide range of temperatures. A thorough combined quantum mechanical and molecular dynamics investigation identifies frustrated localized rotations of the pentacene cores as the reason for the breakdown of band transport and paves the way for a crystal engineering strategy of molecular OSCs that independently varies the arrangement of the molecular cores and their vibrational degrees of freedom
Evaluating the Effects of Geometry and Charge Flux in Force Field Modeling
We apply a model
for analyzing the importance of conformational
charge flux to 11 molecules with the Râ(CH<sub>2</sub>)<sub><i>n</i></sub>âR structure (R = Cl, F, OH, SH, COOH,
CONH<sub>2</sub>, and NH<sub>2</sub> and <i>n</i> = 4â6).
Atomic charges were obtained by fitting to results from density functional
theory calculations using the HLY procedure, and their geometry dependence
is decomposed into contributions from changes in bond lengths, bond
angles, and torsional angles. The torsional degrees of freedom are
the main contribution to the conformational dependence of atomic charges
and molecular dipole moments, but indirect effects due to changes
in bond distances and angles account for âŒ15% of the variations.
While the magnitude of charge flux and geometry effects have been
found to be independent of the number of internal degrees of freedom,
the nature of the R- group has a moderate influence. The indirect
effects are comparable for all of the R-groups and are approximately
one-half the magnitude of the corresponding effects in peptide models.
However, the magnitudes are different, yet the relative importance
of geometry and charge flux effects are completely similar to those
of the peptide models, which suggests that modeling the charge flux
effects for changes in bond lengths, bond angles, and torsional angles
should be considered for developing improved force fields
Evaluating the Effects of Geometry and Charge Flux in Force Field Modeling
We apply a model
for analyzing the importance of conformational
charge flux to 11 molecules with the Râ(CH<sub>2</sub>)<sub><i>n</i></sub>âR structure (R = Cl, F, OH, SH, COOH,
CONH<sub>2</sub>, and NH<sub>2</sub> and <i>n</i> = 4â6).
Atomic charges were obtained by fitting to results from density functional
theory calculations using the HLY procedure, and their geometry dependence
is decomposed into contributions from changes in bond lengths, bond
angles, and torsional angles. The torsional degrees of freedom are
the main contribution to the conformational dependence of atomic charges
and molecular dipole moments, but indirect effects due to changes
in bond distances and angles account for âŒ15% of the variations.
While the magnitude of charge flux and geometry effects have been
found to be independent of the number of internal degrees of freedom,
the nature of the R- group has a moderate influence. The indirect
effects are comparable for all of the R-groups and are approximately
one-half the magnitude of the corresponding effects in peptide models.
However, the magnitudes are different, yet the relative importance
of geometry and charge flux effects are completely similar to those
of the peptide models, which suggests that modeling the charge flux
effects for changes in bond lengths, bond angles, and torsional angles
should be considered for developing improved force fields
Modeling Exciton Transport in Organic Semi-conductors Using Machine Learned Hamiltonian and its Gradients
In this study, we present a multiscale method to simulate the propagation of Frenkel singlet excitons in Organic Semi-conductors(OSCs). The approach uses advanced neural network models to train Frenkel-type Hamiltonian and its gradient, obtained by the Long-Range Correction version of Density Functional Tight-Binding with Self-Consistent Charges (LC-DFTB2). Our models accurately predict site energies, excitonic couplings, and corresponding gradients, essential for the non-adiabatic molecular dynamics simulations. Combined with Fewest Switches Surface Hopping (FSSH) algorithm, the method was applied to four representative OSCs: Anthracene (ANT), Pentacene (PEN), Perylenediimide (PDI), and Diindenoperylene (DIP). The simulated exciton diffusion constants align well with experimental and reported theoretical values, and offer valuable insights into exciton dynamics in OSCs
Diâ and TetracyanoâSubstituted PyreneâFused Pyrazaacenes: Aggregation in the Solid State
Means to stream: Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown, and the crystal packing was studied by XRD and DFT calculations of transfer integrals and reorganization energies with a view to their possible use as n-type semiconductors.
Five di- and tetracyano-substituted pyrene-fused pyrazaacenes were synthesized and studied as potential electron acceptors in the solid state. Single crystals of all compounds were grown and the crystal packing studied by DFT calculations (transfer integrals and reorganization energies) to get insight into possible use for semiconducting charge transport