scholarly journals Unraveling the electrochemical and spectroscopic properties of neutral and negatively charged perylene tetraethylesters

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Christian Wiebeler ◽  
Joachim Vollbrecht ◽  
Adam Neuba ◽  
Heinz-Siegfried Kitzerow ◽  
Stefan Schumacher
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Energy Levels ◽  
Spectroscopic Properties ◽  
Absorption Bands ◽  
Functional Theory ◽  
Vertical Excitation ◽  
Hartree Fock ◽  
Tauc Plot ◽  
Electrochemical Approach

AbstractA detailed investigation of the energy levels of perylene-3,4,9,10-tetracarboxylic tetraethylester as a representative compound for the whole family of perylene esters was performed. It was revealed via electrochemical measurements that one oxidation and two reductions take place. The bandgaps determined via the electrochemical approach are in good agreement with the optical bandgap obtained from the absorption spectra via a Tauc plot. In addition, absorption spectra in dependence of the electrochemical potential were the basis for extensive quantum-chemical calculations of the neutral, monoanionic, and dianionic molecules. For this purpose, calculations based on density functional theory were compared with post-Hartree–Fock methods and the CAM-B3LYP functional proved to be the most reliable choice for the calculation of absorption spectra. Furthermore, spectral features found experimentally could be reproduced with vibronic calculations and allowed to understand their origins. In particular, the two lowest energy absorption bands of the anion are not caused by absorption of two distinct electronic states, which might have been expected from vertical excitation calculations, but both states exhibit a strong vibronic progression resulting in contributions to both bands.

STRUCTURES AND SPECTROSCOPIC PROPERTIES OF THREE AROMATIC HETEROCYCLIC DYE PHOTOSENSITIZERS

2013 ◽  
Vol 12 (06) ◽  
pp. 1350055
Author(s):  
YUANZUO LI ◽  
CHAOFAN SUN ◽  
LINPO YANG
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectra ◽  
Density Functional ◽  
Energy Levels ◽  
Electron Transition ◽  
Spectroscopic Properties ◽  
Molecular Orbitals ◽  
Functional Theory ◽  
Solvent Phase ◽  
Charge Difference Density

The ground-state structures and absorption spectra of three dyes, carbazole, phenothiazine and diphenylamine, were studied by the density functional theory (DFT) and time-dependent density functional theory (TD-DFT). The strong absorption peak, electron transition as well as the energy levels of molecular orbitals were obtained and compared in the gas and solvent phase. Furthermore, we further calculated the effect of the expanding conjugated bridge on the absorption spectra and the energy levels of molecular orbitals. Visualized method of charge difference density (CDD) was used to show the direction of charge transfer in the molecules of interest during photo-excitation.

scholarly journals Terahertz Absorption Spectroscopy of Benzamide, Acrylamide, Caprolactam, Salicylamide, and Sulfanilamide in the Solid State

2014 ◽  
Vol 2014 ◽  
pp. 1-9 ◽  
Author(s):  
Ye Jiang ◽  
Fengshan Zhou ◽  
Xiaodong Wen ◽  
Limin Yang ◽  
Guozhong Zhao ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Solid State ◽  
Absorption Spectra ◽  
Density Functional ◽  
Room Temperature ◽  
Solid Phase ◽  
Absorption Bands ◽  
Functional Theory ◽  
Terahertz Absorption ◽  
Thz Absorption

Terahertz (THz) absorption spectra of the similarly structured molecules with amide groups including benzamide, acrylamide, caprolactam, salicylamide, and sulfanilamide in the solid phase at room temperature and 7.8 K for salicylamide are reported and compared to infrared vibrational spectral calculations using density functional theory. The results of THz absorption spectra show that the molecules have characteristic bands in the region of 0.2–2.6 THz (~7–87 cm−1). THz technique can be used to distinguish different molecules with amide groups. In the THz region benzamide has three bands at 0.83, 1.63, and 1.73 THz; the bands are located at 1.44 and 2.00 THz for acrylamide; the bands at 1.24, 1.66 and 2.12 THz are observed for caprolactam. The absorption bands are located at 1.44, 1.63, and 2.39 THz at room temperature, and at 1.22, 1.46, 1.66, and 2.41 THz at low temperature for salicylamide. The bands at 1.63, 1.78, 2.00, and 2.20 THz appear for sulfanilamide. These bands in the THz region may be related to torsion, rocking, wagging, and other modes of different groups in the molecules.

A theoretical investigation of tetrahydroquinoline dyes with different spacers used for sensitized solar cells

2011 ◽  
Vol 89 (8) ◽  
pp. 978-986 ◽  
Author(s):  
Jie Xu ◽  
Lei Wang ◽  
Li Liu ◽  
Zikui Bai ◽  
Luoxin Wang ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Density Functional ◽  
Photovoltaic Performance ◽  
Molecular Structures ◽  
Absorption Bands ◽  
Functional Theory ◽  
Spacer Length ◽  
Solvent Interaction ◽  
Td Dft ◽  
Sensitized Solar Cells

The molecular structures and absorption spectra of three tetrahydroquinoline dyes (C2–1, C1–1, and C1–5) with a tetrahydroquinoline moiety as the electron donor, a cyanoacrylic acid moiety as the electron acceptor, and different thiophene-containing electron spacers were investigated by density functional theory (DFT) and time-dependent DFT (TD-DFT). The calculated geometries indicate that a strong conjugation is formed in the dyes and the conjugate length increases with the increase of spacer length. The interfacial charge transfer between the semiconductor electrode and the tetrahydroquinoline dyes are electron-injection processes from the excited dyes to the semiconductor conduction band. The simulated absorption bands are assigned to π–π* transitions, which exhibit appreciable red-shift with respect to the experimental bands owing to the lack of direct solute–solvent interaction and the inherent approximations in TD-DFT. Moreover, the effect of different spacers on the molecular structures, absorption spectra, and photovoltaic performance were comparatively discussed.

scholarly journals Density Functional Theory Study on the Electronic Structures of Oxadiazole Based Dyes as Photosensitizer for Dye Sensitized Solar Cells

2015 ◽  
Vol 2015 ◽  
pp. 1-8 ◽  
Author(s):  
Umer Mehmood ◽  
Ibnelwaleed A. Hussein ◽  
Khalil Harrabi ◽  
Shakeel Ahmed
Keyword(s):  
Density Functional Theory ◽  
Absorption Spectra ◽  
Density Functional ◽  
Energy Levels ◽  
Dye Sensitized Solar Cells ◽  
Electron Injection ◽  
Molecular Structures ◽  
Visible Absorption ◽  
Functional Theory ◽  
Oxidation Potentials

The molecular structures and UV-visible absorption spectra of complex photosensitizers comprising oxadiazole isomers as theπ-bridges were analyzed by density functional theory (DFT) and time-dependent DFT. The ground state and excited state oxidation potentials, HOMOs and LUMOs energy levels, and electron injection from the dyes to semiconductor TiO2have been computed in vacuum here. The results show that all of the dyes may potentially be good photosensitizers in DSSC. To justify the simulation basis, N3 dye was also simulated under the similar conditions. Simulated absorption spectrum, HOMO, LUMO, and band gap values of N3 were compared with the experimental values. We also computed the electronic structure properties and absorption spectra of dye/(TiO2)8systems to elucidate the electron injection efficiency at the interface. This work is expected to give proper orientation for experimental synthesis.

Fe(dppe)(η5-C5Me5)-Based Phenylalkynyl Complexes Featuring an NO2 End Group: A Theoretical Analysis

2015 ◽  
Vol 68 (9) ◽  
pp. 1352 ◽  
Author(s):  
Hiba Sahnoune ◽  
Nicolas Gauthier ◽  
Katy Green ◽  
Karine Costuas ◽  
Frédéric Paul ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Energy Absorption ◽  
Density Functional ◽  
Spectroscopic Properties ◽  
Carbon Chain ◽  
Absorption Bands ◽  
Functional Theory ◽  
Ligand Charge Transfer ◽  
Group A ◽  
End Group

Electronic structures and optical properties of a series of compounds Fe(dppe)(η5-C5Me5){[C≡C(1,4-C6H4)]nNO2} (1–3; n = 1–3, dppe = 1,2-bis(diphenylphosphino)ethane) were investigated with the aid of density functional theory and time-dependent density functional theory computations. The results reveal that the extension of the carbon-rich chain has a moderate influence on the electronic properties of the studied compounds in their ground state, but affects notably their spectroscopic properties, with some unexpected hypsochromic shift of the lower energy absorption bands upon carbon chain lengthening. The appropriate excitations responsible for the low-energy absorption bands involve mainly HOMO–LUMO transitions dominated by important metal-to-ligand charge transfer. A functional including long-range corrections is necessary to reproduce the experimental results.

Polaronic and Bipolaronic Enhancement of Second Hyperpolarizabilities in Dithienyl Polyenes from Ab Initio Quantum Methods

1999 ◽  
Vol 597 ◽  
Author(s):  
Steven Trohalaki ◽  
Robert J. Zellmer ◽  
Ruth Pachter
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Valence Bond ◽  
Closed Shell ◽  
Functional Theory ◽  
Molecular Conformations ◽  
Hartree Fock ◽  
Molecular Charge ◽  
Field Methodology ◽  
Moller Plesset

AbstractSpangler and He [1,2] have shown that dithienyl polyenes form extremely stable bipolaronic dications when oxidatively doped in solution. Previous theoretical studies applied empirical methods to predict bipolaronic enhancement of hyperpolarizabilities for simple polyenes [3,4]. Here, we employ density functional theory to optimize the gas-phase molecular conformations of neutral, cationic, and dicationic forms of a series of dithienyl polyenes, where the number of ethene units, N, is varied from 1–5. Ab initio Hartree-Fock, generalized valence bond, configuration interaction, and Møller-Plesset calculations demonstrate that the dications are farily well described with a closed shell and therefore have little biradicaloid character. Second hyperpolarizabilities, γ, are subsequently calculated using ab initio Hartree-Fock theory and a finite field methodology. As expected, γ increases with the number of ethene units for a given molecular charge. The cations also show the largest increase in γ with N. For a given value of N, the cations display the largest γ values. However, if we treat the dication as a triplet, which might be present in solution, then it displays the largest γ.

Sign in / Sign up

Export Citation Format

Share Document