Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• their HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Besides, density functional theory calculations were carried out for further exploration of their electronic properties. Keywords: catalysis; cross-coupling; cyclization; fluorescence; palladium; Introduction π-Conjugated

• values of HOMO, LUMO, and the band gap energies of compounds 4a–d at the B3LYP level of theory with 6-31G(d) basis set using dichloromethane as a continuum solvent model are given in Figure 9. The energy gap values are affected by the type and the position of the substituent located at the phenyl groups

• 4f. Calculated energy levels for compounds 4a–d and their spatial distribution of the HOMO–LUMO frontier molecular orbitals from DFT calculations. Visualization of MEP for compounds 4a–d calculated by B3LYP method with 6-31G(d) basis set. Cyclic voltammogram for 4c in 0.1 M (n-Bu)4NBF4/acetonitrile

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• , anti-Kasha photophysics, and a small HOMO–LUMO gap when compared to its isomer, naphthalene. These properties make azulene-containing polymers an intriguing entity in the field of functional polymers, especially for organic electronic applications like organic field-effect transistors (OFET) and

• ) resulting in a relatively small electron repulsion energy in the first singlet excited state and thus, a small HOMO–LUMO (S0–S1) gap compared to naphthalene. The large energy gap between its S2 and S1 states (up to 15000 cm−1) makes internal conversion less probable, making azulene emit from the S2 state

• protonation of 17 and 18 by TFA resulted in a large red-shifted broad absorption band in the 500–900 nm region due to the formation of azulenium cations in the polymer backbone unlike the 1,3-polyazulene 5, which had no significant effect on its absorption spectrum upon protonation. The HOMO–LUMO gap for the

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• -tetrahydroacridine derivatives 4a–g. Photophysical properties of 4a,b and 4e–g in dichloromethane solutions. Visualization of HOMO, LUMO orbitals and MEP. Summary of theoretical calculations.a Supporting Information Supporting Information File 242: Additional experimental data. Acknowledgements The authors thank

Synthesis, structural characterization, and optical properties of benzo[f]naphtho[2,3-b]phosphoindoles

• Mio Matsumura,
• Takahiro Teramoto,
• Masato Kawakubo,
• Masatoshi Kawahata,
• Yuki Murata,
• Kentaro Yamaguchi,
• Masanobu Uchiyama and
• Shuji Yasuike

Beilstein J. Org. Chem. 2021, 17, 671–677, doi:10.3762/bjoc.17.56

• (DFT) calculations [27] were performed at the B3LYP/LanL2DZ level of theory to gain additional understanding of the electronic structures. The HOMO and LUMO energies of the selected compounds are listed in Table 3. The DFT calculations showed that these compounds have HOMO–LUMO gaps of 3.60–3.96 eV

• delocalized in the lone-pair orbitals on the sulfur atom, resulting in considerable destabilization and significantly small HOMO–LUMO gap compared to those of other phospholes 2, 3, 5, and 6. This result is similar to the reduction potentials of compounds 2 and 6. According to time-dependent DFT calculations

• for 4, the S0 to S1 transitions are mainly dominated by the dipole-forbidden lone pair–π* HOMO–LUMO transitions. This phenomenon may be responsible for the nonfluorescence of 4. Both the π and π* energy levels in the all-functionalized phosphole derivatives 3–6 are lower than those of parent phosphole

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• unoccupied molecular orbital (LUMO), the electron density difference between the S1 and S0 states, as well as the S0→S1 CT for compound 8a in the non-polar solvent n-hexane (Figure 6) and in a polar water solution (Figure 7). As it can be seen from the HOMO, LUMO, and electron density difference plots, the

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• for efficient TADF if the donor and acceptor moieties are poorly conjugated with each other in order to minimize J. The HOMO/LUMO separation that controls J can be modulated by introducing strong and bulky electron donors and electron acceptors to produce large torsions between the donor and acceptor

• small ΔEST (0.02 eV) and short delayed fluorescence lifetime (τd = 16.4 μs) in zeonex [20]. These two studies illustrate that ortho-substituted D–A molecules possess highly twisted geometries, leading to spatially separated HOMO/LUMO distributions and, thus, small ΔESTs, while maintaining high energy

• value of 5CzOCF3 is 0.37 eV, which is reduced by 0.11 eV compared to 2CzOCF3 (0.46 eV). This reduction results from the greater CT character in both S1 and T1. However, as the HOMO/LUMO overlap includes a small distribution on para-disposed carbazole in the Type II emitters with the exception of 5CzOCF3

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• heteroacenes exhibited one vibronically well-resolved strong absorption band in the UV-regime of 250–360 nm which we address to the π–π* transition corresponding to the HOMO–LUMO energy gap. The absorption maximum is gradually red-shifted from 318 nm for TTA and with increasing number of pyrrole rings to 330

Synthesis of 6,13-difluoropentacene

• Matthias W. Tripp and
• Ulrich Koert

Beilstein J. Org. Chem. 2020, 16, 2136–2140, doi:10.3762/bjoc.16.181

• HOMO–LUMO gap of 6,13-difluoropentacene was determined via UV–vis spectroscopy and compared to other fluorinated pentacenes. Keywords: fluorinated acenes; Friedel–Crafts reaction; ortho-lithiation; synthesis; Introduction Pentacenes are a prototype in the field of organic semiconductors due to their

• expanded π-systems and low HOMO–LUMO gaps with applications in different molecular-based organic electronics like OFETs, OLEDs or organic photovoltaics [1][2][3]. An advantage of organic molecular electronics over inorganic alternatives is the versatility in design of new molecular materials by

• -positions resulted in a larger HOMO–LUMO gap compared to PEN, while PFP showed a smaller gap than PEN. Another example for a partially fluorinated pentacene is the F6PEN 4 [9]. Its unilateral substitution pattern leads to a disctinct electronic structure and a criss-cross packing motif, unlike the

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• wide-band gap semiconductor towards visible light excitation [95]. The photosensitiser can inject electrons to the semiconductor conduction band via direct HOMO–CB transition (type II excitation) or indirectly by exciting the photosensitiser HOMO–LUMO transition, followed by a LUMO–CB charge transfer

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• following equations; [39] EHOMO= −(4.8 + E1/2ox) and ELUMO= −(4.8 + Eonsetred). The HOMO–LUMO energy gap was calculated both from electrochemical data using Equation 1 and from optical data using Equation 2 [25][40][41]. The optical energy gap (Ego) was higher than the electrochemical energy gap (Ege) for

• compounds 7a and 7b. The oxidation and reduction potentials and the HOMO–LUMO energy levels of both compounds are summarised in Table 2 and the energy levels are depicted in Figure 3. Optical properties The absorption properties of compounds 7a and 7b were investigated in dichloromethane using a Duetta

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• CV analysis, compound 1 exhibits one reversible oxidation wave with half-wave potentials (E1/2ox) at 1.12 V and four reduction waves with half-wave potentials (E1/2red) at −0.65, −0.92, −1.15, and −1.37 V (vs Ag/AgCl). The HOMO/LUMO energy levels are estimated to be −5.37 /−3.80 eV, respectively

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• extended conjugation present between the two linearly linked porphyrin units. Extended conjugation causes increased planarity and conjugation in the system, along with a reduction in the HOMO–LUMO gap resulting in the red-shifted spectra. In contrast to the porphyrin emission spectra, BODIPYs exhibit a

• blue-shifted spectrum with lower Stokes Shift values, enabling a different frequency of light to be accessed. Overall, there is a significant difference in the HOMO–LUMO gap of the three porphyrin dimers. The meso–meso-linked dimer 19 has the largest gap of 2.21 eV, followed by the triptycene-linked

• dimer 9 with a gap of 2.03 eV and the butadiyne-linked dimer 20 with 1.87 eV. These values give an initial indication of the extent of π-conjugation occurring within these systems, as the more conjugation present in the system the lower the HOMO–LUMO gap. A spectroscopic comparison of the porphyrin

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• estimated to be 2.30, 2,14, 2.35, and 2.21 V, respectively, which is consistent with the calculated HOMO–LUMO energy gaps (vide infra, Figure S24, Supporting Information File 1). Theoretical calculations To gain insight into the substitution effect on the electronic properties of the BODIPY derivatives

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• withdrawing moieties. Quantum chemical calculations showed only small contributions of the substituent placed at the meso-position to the electron density in the HOMO/LUMO pattern [81]. Presumably, coupling of lower occupied molecular orbitals with the HOMO on the one hand side and higher unoccupied MOs with

Six-fold C–H borylation of hexa-peri-hexabenzocoronene

• Mai Nagase,
• Kenta Kato,
• Akiko Yagi,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2020, 16, 391–397, doi:10.3762/bjoc.16.37

• its LUMO and LUMO+1 are degenerate. The HOMO and LUMO energies of 1 increase under the influence of the σ-donation of the boryl groups, resulting in a decrease of the HOMO–LUMO energy gap. This is in line with the bathochromic shift observed in the absorption spectrum of 1 from that of HBC. Conclusion

• showed that the boryl groups increased the energies of frontier molecular orbitals and decreased the HOMO–LUMO energy gap. Compound 1 will contribute to a step-economical synthesis of various HBC derivatives as a platform, and furthermore, the currently developed borylation method gives insight into the

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• of 3 and 4. HOMO/LUMO and S1/T1 energies as well as HOMO/LUMO electron density distribution profiles of 2–5. Cyclic voltammograms and differential pulse voltammograms of 2–5 in degassed DCM (scan rate = 100 mV·s−1). UV–vis absorption spectra of 2–5 in DCM and photoluminescence spectrum of 3 in

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• characteristically, for all 1H-pyridines 5 and 8 the longest wavelength maxima representing the Franck–Condon S1 states are characterized by HOMO–LUMO transitions and S2 states are represented by HOMO–LUMO+1 transitions. The computed Kohn–Sham frontier molecular orbitals show that the coefficient density of the HOMO

• maxima are characterized by Franck–Condon S1 states representing HOMO–LUMO transitions (Figure 17). The computed Kohn–Sham frontier molecular orbitals show that the coefficient density of the HOMO in the parent α-pyrone 6a is localized on the α-pyrone core and on the phenyl substituent in the 6-position

Plasma membrane imaging with a fluorescent benzothiadiazole derivative

• Pedro H. P. R. Carvalho,
• Jose R. Correa,
• Karen L. R. Paiva,
• Daniel F. S. Machado,
• Jackson D. Scholten and
• Brenno A. D. Neto

Beilstein J. Org. Chem. 2019, 15, 2644–2654, doi:10.3762/bjoc.15.257

• bands showed an excellent agreement with those obtained experimentally in both terms the peak positions as well as their relative intensities. The π–π* band is entirely described by a HOMO–LUMO vertical transition as visualized in Figure 4C. The LUMO orbital is strictly distributed over the BTD core in

An overview of the cycloaddition chemistry of fulvenes and emerging applications

• Ellen Swan,
• Kirsten Platts and
• Anton Blencowe

Beilstein J. Org. Chem. 2019, 15, 2113–2132, doi:10.3762/bjoc.15.209

• , particularly at the exocyclic C6 position [1][2][6][42][71]. Considering molecular orbital theory, pentafulvenes have a high-energy highest occupied molecular orbital (HOMO) and low-energy lowest unoccupied molecular orbital (LUMO) [1][2][6][42] (HOMO–LUMO) energy gap that is small enough to allow the

• throughout this article [34]. Generic structures of commonly referenced heteropentafulvenes, named according to the heteroatom substitution: oxafulvene, azafulvene, phosphafulvene, thiafulvene and silafulvene. A representation of HOMO–LUMO orbitals of pentafulvene and the influence of EWG and EDG

Friedel–Crafts approach to the one-pot synthesis of methoxy-substituted thioxanthylium salts

• Kenta Tanaka,
• Yuta Tanaka,
• Mami Kishimoto,
• Yujiro Hoshino and
• Kiyoshi Honda

Beilstein J. Org. Chem. 2019, 15, 2105–2112, doi:10.3762/bjoc.15.208

• ) (Figure 3a,b). Based on these calculations, it was found that tetramethoxy substituents at the thioxanthylium core lead to an up-shift of both HOMO/LUMO energy levels compared to thioxanthylium salts without methoxy groups (Figure 3c,d). The maximum absorption wavelength of thioxanthylium salt 3b (λmax

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• predominantly the charge transfer type HOMO -> LUMO transitions (Supporting Information File 1, Tables S1 and S2). The easiness of protonation and stability of salts 6 evidenced the behavior of THTAA (3) as a strong base. Indeed, our DFT calculations of the proton affinity of THTAA (3) produced ΔH298 = 235.9

Reactions of 2-carbonyl- and 2-hydroxy(or methoxy)alkyl-substituted benzimidazoles with arenes in the superacid CF₃SO₃H. NMR and DFT studies of dicationic electrophilic species

• Dmitry S. Ryabukhin,
• Alexey N. Turdakov,
• Natalia S. Soldatova,
• Mikhail O. Kompanets,
• Alexander Yu. Ivanov,
• Irina A. Boyarskaya and
• Aleksander V. Vasilyev

Beilstein J. Org. Chem. 2019, 15, 1962–1973, doi:10.3762/bjoc.15.191

• the formation of heteroaromatic benzyl-type dications IV, VI, and IX, respectively. Electronic characteristics, energies of HOMO/LUMO, electrophilicity indices ω [25][26], charge distribution, and contribution of atomic orbital into the LUMO of species I–IX were calculated by DFT method to estimate

Functional panchromatic BODIPY dyes with near-infrared absorption: design, synthesis, characterization and use in dye-sensitized solar cells

• Quentin Huaulmé,
• Cyril Aumaitre,
• Outi Vilhelmiina Kontkanen,
• David Beljonne,
• Alexandra Sutter,
• Gilles Ulrich,
• Renaud Demadrille and
• Nicolas Leclerc

Beilstein J. Org. Chem. 2019, 15, 1758–1768, doi:10.3762/bjoc.15.169

• sensitizer has to display high molar absorption coefficients, ideally along the entire visible range. Additionally, it must display appropriate positioning of frontier molecular orbitals (highest occupied molecular orbital/lowest unoccupied molecular orbital, HOMO/LUMO) energy levels with respect to the

• and 4, explaining the deeper unoccupied levels in the former molecules. Thus, our calculations suggest that, in case of an allowed HOMO–LUMO transition, 1 and 3 should show a bathochromically shifted optical absorption spectrum, thereby hopefully allowing for a more efficient sunlight absorption, yet

Selenophene-containing heterotriacenes by a C–Se coupling/cyclization reaction

• Pierre-Olivier Schwartz,
• Sebastian Förtsch,
• Astrid Vogt,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2019, 15, 1379–1393, doi:10.3762/bjoc.15.138

• electronic transitions in a very narrow range of the spectrum: HOMO → LUMO transition, S1, whose transition dipole is oriented along the long-axis of the molecule and a HOMO-1 → LUMO transition, S2, whose transition dipole orients perpendicular to the long axis of the molecule (Table 3). In Figure 5 (right

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• ), oscillator strength (f) HOMO and LUMO energies and energy difference (HOMO–LUMO gap, HLG) for the trans isomers of compounds 4a–d in acetonitrile. Supporting Information Supporting Information File 436: Experimental procedures for the synthesis of compounds 2–4 and characterization data of the new compounds