Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes

• Bartłomiej Pigulski

Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99

• due to the dominance of surrounding benzenoid rings or the presence of biradical character. As a result, these PAHs despite, possessing formal azulene may exhibit properties typical of benzenoid molecules rather than the characteristic azulene features such as red-shifted absorption, a small HOMO–LUMO

• gap, aromaticity of azulene subunit and anti-Kasha’s emission from higher excited states. In such cases, the azulene unit merely acts as a linker within a more complex benzenoid framework. This review covers all types of azulene-embedded molecular scaffolds, regardless of whether they contain a

Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps

• Qian Liu and
• Glen P. Miller

Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97

• gaps is achievable. As such, these molecules deserve increased attention as potential p-type organic semiconductors. Keywords: acene; DFT calculation; highly delocalized π-system; isoacenofuran; isobenzofuran; kinetically stabilized; organic semiconductor; small HOMO–LUMO gap; synthesis; Introduction

• –LUMO gap to 1.65 eV. Even in the presence of sterically congesting, non-planar 1,3-dimesityl groups, the corresponding isotetracenofuran (15) possesses an unusually small HOMO–LUMO gap of 1.59 eV. Among the isoacenofurans studied here, the smallest calculated HOMO–LUMO gaps are observed in the

Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• -chromophores” after the shape of the main structural fragment resembling the Latin letter “H” (Figure 4) [19]. The small HOMO–LUMO gap and, thus, the long-wavelength absorption are responsible for the purple color of indigo in vapors, which changes into deep blue color in the crystalline state due to formation

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

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

• 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

Direct estimate of the internal π-donation to the carbene centre within N-heterocyclic carbenes and related molecules

• Diego M. Andrada,
• Nicole Holzmann,
• Thomas Hamadi and
• Gernot Frenking

Beilstein J. Org. Chem. 2015, 11, 2727–2736, doi:10.3762/bjoc.11.294

• coefficient at the Ccarb atom that makes it suitable for π-backdonation. The LUMOs of compounds 1, and 7–10 which are not displayed in Figure 2 are also π-orbitals which have a node at the Ccarb atom. The HOMO–LUMO energy difference varies considerably between 4.58 eV (4) and 1.55 eV (15). The small HOMO–LUMO

• gap of the diamidocarbene 15 comes from the very low lying LUMO which has been noted before [42]. There is clearly a correlation between the HOMO–LUMO energy difference and the calculated singlet–triplet gap of the compounds which are given at the bottom of Figure 2. The largest singlet–triplet (S/T