Electronic structure modifications induced by increased molecular complexity: from triphenylamine to m-MTDATA

Zhang, Teng; Brumboiu, Iulia Emilia; Lanzilotto, Valeria; Grazioli, Cesare; Guarnaccio, Ambra; Johansson, Fredrik; Coreno, Marcello; Simone, Monica de; Santagata, A.; Brena, Barbara; Puglia, Carla

doi:10.1039/c9cp02423a

Cited by 10 publications

(30 citation statements)

References 56 publications

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“…This motivated the use of a full core-hole on the core-excited atom or alternatively a full core hole in combination with an electron placed in the lowest unoccupied MO (excited-state core hole) . Owing to the low computational cost of TP-DFT, X-ray absorption spectra of rather large molecules can be calculated with reasonable accuracy in comparison to experiment. ,, However, TP-DFT is essentially a ground-state single-particle approach, where orbital relaxation is not included rigorously but via the adjustable core-hole occupation parameter.…”

Section: Introductionmentioning

confidence: 99%

“…91 Owing to the low computational cost of TP-DFT, Xray absorption spectra of rather large molecules can be calculated with reasonable accuracy in comparison to experiment. 92,126,127 However, TP-DFT is essentially a ground-state single-particle approach, where orbital relaxation is not included rigorously but via the adjustable core-hole occupation parameter.…”

Section: ■ Introductionmentioning

confidence: 99%

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XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions

Fransson

Brumboiu

Vidal

et al. 2021

J. Chem. Theory Comput.

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The performance of several standard and popular approaches for calculating X-ray absorption spectra at the carbon, nitrogen, and oxygen K-edges of 40 primarily organic molecules up to the size of guanine has been evaluated, focusing on the low-energy and intense 1s → π* transitions. Using results obtained with CVS-ADC(2)-x and fc-CVS-EOM-CCSD as benchmark references, we investigate the performance of CC2, ADC(2), ADC(3/2), and commonly adopted density functional theory (DFT)-based approaches. Here, focus is on precision rather than on accuracy of transition energies and intensities—in other words, we target relative energies and intensities and the spread thereof, rather than absolute values. The use of exchange–correlation functionals tailored for time-dependent DFT calculations of core excitations leads to error spreads similar to those seen for more standard functionals, despite yielding superior absolute energies. Long-range corrected functionals are shown to perform particularly well compared to our reference data, showing error spreads in energy and intensity of 0.2–0.3 eV and ∼10%, respectively, as compared to 0.3–0.6 eV and ∼20% for a typical pure hybrid. In comparing intensities, state mixing can complicate matters, and techniques to avoid this issue are discussed. Furthermore, the influence of basis sets in high-level ab initio calculations is investigated, showing that reasonably accurate results are obtained with the use of 6-311++G**. We name this benchmark suite as XABOOM (X-ray absorption benchmark of organic molecules) and provide molecular structures and ground-state self-consistent field energies and spectroscopic data. We believe that it provides a good assessment of electronic structure theory methods for calculating X-ray absorption spectra and will become useful for future developments in this field.

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Section: Introductionmentioning

confidence: 99%

Section: ■ Introductionmentioning

confidence: 99%

XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions

Fransson

Brumboiu

Vidal

et al. 2021

J. Chem. Theory Comput.

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“…m -MTDATA (4,4′,4″-tris( N -3-methylphenyl- N -phenylamino)triphenylamine, C 57 H 48 N 4 ) belongs to a group of molecules called “starburst π-conjugated systems”, for which the triphenylamine (TPA) is regarded as their building block (Figure ). − Starburst molecules are quite often found in organic optoelectronic devices, like organic light emitting diodes (OLEDs), organic photovoltaics (OPVs), and more recently, solid dye sensitized solar cells (DSSCs), proving to be a key factor of their high efficiency. − Our study of gas-phase m -MTDATA showed that the good electron-donating and charge-transfer properties of this starburst molecule are largely related to its building block triphenylamine (TPA), particularly involving the lone pair electrons of the N atoms. Moreover, the more complex molecular structure of m -MTDATA with respect to TPA potentially promotes the formation of homogeneous amorphous and glassy molecular films with higher thermal stability and better electron transport properties than films of TPA. − …”

Section: Introductionmentioning

confidence: 99%

m-MTDATA on Au(111): Spectroscopic Evidence of Molecule–Substrate Interactions

et al. 2022

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The starburst π-conjugated molecule based on triphenylamine (TPA) building blocks, 4,4′,4″-tris(N-3-ethylphenyl-N-phenylamino)triphenylamine (C 57 H 48 N 4 , m-MTDATA), is widely used in optoelectronic devices due to its electron-donating properties. The electronic structure of m-MTDATA adsorbed on an Au(111) surface was investigated by means of photoelectron spectroscopy (PES) and near edge X-ray absorption fine structure (NEXAFS) spectroscopy. The results were further compared to gasphase measurements and DFT calculations. Our results clearly indicate a significant molecule−substrate interaction that induces considerable modifications on the electronic structure of the adsorbate compared to the isolated molecule. The energy level alignment analysis shows that the HOMO−LUMO gap is filled by new interface states.

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“…We can easily find that the C 1s spectrum of B2PyMPM is composed of two peaks, one with a higher intensity at 284.87 eV and the other with a lower intensity at 285.93 eV (see Table 1 ). Although there are a dozen types of carbon atoms theoretically in a molecule, 33 the two peaks are roughly assigned to the C atoms that are not directly attached (C=C) and attached (C=N) to the N atom, corresponding to the atoms marked in green and blue, respectively, in Figure 3 e. This is because the ortho C atoms are susceptible to the electronegative N atom and become electron deficient. The area ratio of the two peaks is 2.33:1, fitting neatly into the stoichiometric ratio (26 C=C carbon atoms and 11 C=N carbon atoms in one molecule).…”

Section: Results and Discussionmentioning

confidence: 99%

Understanding Interface Dipoles at an Electron Transport Material/Electrode Modifier for Organic Electronics

Chen

Liu

Fahlman

2021

ACS Appl. Mater. Interfaces

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Interface dipoles formed at an electrolyte/electrode interface have been widely studied and interpreted using the “double dipole step” model, where the dipole vector is determined by the size and/or range of motion of the charged ions. Some electron transport materials (ETMs) with lone pairs of electrons on heteroatoms exhibit a similar interfacial behavior. However, the origin of the dipoles in such materials has not yet been explored in great depth. Herein, we systematically investigate the influence of the lone pair of electrons on the interface dipole through three pyridine derivatives B2–B4PyMPM. Experiments show that different positions of nitrogen atoms in the three materials give rise to different hydrogen bonds and molecular orientations, thereby affecting the areal density and direction of the lone pair of electrons. The interface dipoles of the three materials predicted by the “double dipole step” model are in good agreement with the ultraviolet photoelectron spectroscopy results both in spin-coated and vacuum-deposited films. These findings help to better understand the ETMs/electrode interfacial behaviors and provide new guidelines for the molecular design of the interlayer.

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Electronic structure modifications induced by increased molecular complexity: from triphenylamine to m-MTDATA

Abstract: The comprehensive electronic structure of a starburst molecule (m-MTDATA) is thoroughly characterized for the first time, unveiling its good electron donor properties.

Cited by 10 publications

References 56 publications

XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions

XABOOM: An X-ray Absorption Benchmark of Organic Molecules Based on Carbon, Nitrogen, and Oxygen 1s → π* Transitions

m-MTDATA on Au(111): Spectroscopic Evidence of Molecule–Substrate Interactions

Understanding Interface Dipoles at an Electron Transport Material/Electrode Modifier for Organic Electronics

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