Thiazolidinones: novel insights from microwave synthesis, computational studies, and potentially bioactive hybrids

• Luan A. Martinho,
• Victor H. J. G. Praciano,
• Guilherme D. R. Matos,
• Claudia C. Gatto and
• Carlos Kleber Z. Andrade

Beilstein J. Org. Chem. 2025, 21, 2618–2636, doi:10.3762/bjoc.21.203

• -TZVPP single point calculations in CPCM water of compounds 3n and 4n in protonated, deprotonated, and neutral forms showed that there is a degree of charge transfer between a HOMO–LUMO excitation in their neutral and deprotonated forms [98]. Protonation of the nitrogen atom in the donor region shifts

• the electronic density towards the acceptor regions (Figure 10), which inhibits the intramolecular charge transfer upon excitation. It is important to note that protonation and deprotonation can significantly alter the HOMO–LUMO gap of a molecule by disrupting its electronic structure. In general

• , protonation of these compounds resulted in a lowering of the HOMO energy level, leading to an increase in the HOMO–LUMO gap and, consequently, greater molecular stability. In contrast, deprotonation led to an increase in the LUMO energy level, with little influence on the HOMO energy. Notably, the neutral

Transition-state aromaticity and its relationship with reactivity in pericyclic reactions

• Israel Fernández

Beilstein J. Org. Chem. 2025, 21, 1613–1626, doi:10.3762/bjoc.21.125

• reaction coordinate, and particularly, at the transition state region. This results from the formation of a stabilizing, intramolecular CH3–OH···O=CH2 hydrogen bond at the initial stages of the process which brings together both reactants, significantly enhancing the orbital interactions (mainly HOMO–LUMO

Thermodynamic equilibrium between locally excited and charge transfer states in perylene–phenothiazine dyads

• Issei Fukunaga,
• Shunsuke Kobashi,
• Yuki Nagai,
• Hiroki Horita,
• Hiromitsu Maeda and
• Yoichi Kobayashi

Beilstein J. Org. Chem. 2025, 21, 1577–1586, doi:10.3762/bjoc.21.121

• coupling in the ground state, consistent with the π-orthogonal molecular design. The introduction of electron-donating TPA groups raises the HOMO energy levels, while the LUMO levels remain relatively unaffected, thereby reducing the HOMO–LUMO gaps. The presence of phenyl spacers in Pe–Ph–PTZ(TPA)2 lowers

• TPA-substituted compounds, several weak absorption bands corresponding to CT transitions (primarily HOMO→LUMO) appear in the longer-wavelength region (Figure 3c), in good agreement with the experimental observations. Steady-state emission spectra of the Pe–PTZ derivatives displayed dual emission bands

Highly distinguishable isomeric states of a tripodal arylazopyrazole derivative on graphite through electron/hole-induced switching at ambient conditions

• Himani Malik,
• Sudha Devi,
• Debapriya Gupta,
• Ankit Kumar Gaur,
• Sugumar Venkataramani and
• Thiruvancheril G. Gopakumar

Beilstein J. Org. Chem. 2025, 21, 1496–1507, doi:10.3762/bjoc.21.112

• theory using Gaussian 03. The computed HOMO–LUMO gap of EEE, EEZ, EZZ and ZZZ isomers is 3.59 eV, 3.27 eV, 3.26 eV, and 3.35 eV, respectively (see details in Supporting Information File 1, section 8). The HOMO–LUMO gap obtained from the calculation is much higher than the gap obtained from the threshold

• on the surface. To understand the low threshold voltage for switching and the possible scenario of charging of molecules, we have analyzed the density of states (DOS) of positively charged and negatively charged FNAAP. The HOMO–LUMO gap of all isomers in single negative/positive charge is

• substantially reduced (see Supporting Information File 1, section 9 and section 10 for details of calculated DOS). The calculated HOMO–LUMO gap of charged FNAAP is smaller than that of the neutral FNAAP, which means the frontier molecular orbitals are closer to the Fermi level. The significantly smaller HOMO

Wittig reaction of cyclobisbiphenylenecarbonyl

• Taito Moribe,
• Junichiro Hirano,
• Hideaki Takano,
• Hiroshi Shinokubo and
• Norihito Fukui

Beilstein J. Org. Chem. 2025, 21, 1454–1461, doi:10.3762/bjoc.21.107

• optical HOMO–LUMO gap of 5 despite the presence of 26 sp2 carbons is due to the cross-conjugation at the exocyclic olefins. Mono-olefin 3 is virtually non-emissive, similarly to CBBC 1, which could originate from the non-radiative decay via intersystem crossing due to the carbonyl group. In sharp contrast

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

• in 1,2-dichloroethane giving PAHs 134–137 in high yields (71–85%). All the new PAHs exhibit characteristics typical for “true” π-extended azulenes, such as azulene-like optical absorption and narrow HOMO–LUMO gaps. In addition, compounds 134–137 show reversible stimuli-responsiveness against the acid

• (89%). Interestingly, the fusion of two azulene units at peri-position induces the significant orbital interaction, resulting in a very narrow HOMO–LUMO gap in 172. Consequently, 172 exhibits NIR absorption properties (λmax = 1180 nm, tail to 1720 nm) and reversible redox behaviours (electrochemical

Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts

• Katy Medrano-Uribe,
• Jorge Humbrías-Martín and
• Luca Dell’Amico

Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76

• experimentally in the solvatochromism study of fluorescence using solvents with diverse polarities (see Supporting Information File 1, Figure S9). Indeed, the density functional theory (DFT) calculation performed at WB97XD/Def2TZVP level of theory showed the lowest value for the HOMO–LUMO energy gap in compound

• behavior is supported by the DFT studies, which suggested a better spatial separation between the HOMO and LUMO. As expected, the HOMO–LUMO energy gap followed a trend that is dependent on the electron-donating capacity of the nitrogen heterocycles and amine present in compounds 5e (2.9 eV), 5d (3.5 eV

Substituent effects in N-acetylated phenylazopyrazole photoswitches

• Radek Tovtik,
• Dennis Marzin,
• Pia Weigel,
• Stefano Crespi and
• Nadja A. Simeth

Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66

• compared to classical azobenzenes and remains to be better understood. Interestingly, Leistner et al. recently reported that introducing a formyl group in the para position of tetra-ortho-fluoro or -chloro-substituted azobenzenes leads to the decrease of the HOMO–LUMO gap resulting in a significant 50 nm

Deep-blue emitting 9,10-bis(perfluorobenzyl)anthracene

• Long K. San,
• Sebastian Balser,
• Brian J. Reeves,
• Tyler T. Clikeman,
• Yu-Sheng Chen,
• Steven H. Strauss and
• Olga V. Boltalina

Beilstein J. Org. Chem. 2025, 21, 515–525, doi:10.3762/bjoc.21.39

• , whereas 9,10-ANTH(BnF)2 loses vibronic structure in the emission spectrum. This may be the result of different conformations upon relaxation [31]. The HOMO–LUMO gap (Eg) decreases from ANTH (3.28 eV) to 9,10-ANTH(BnF)2 (3.05 eV). A decrease in Eg is regarded as one of the methods for improving the

Synthesis and characterizations of highly luminescent 5-isopropoxybenzo[rst]pentaphene

• Islam S. Marae,
• Jingyun Tan,
• Rengo Yoshioka,
• Zakaria Ziadi,
• Eugene Khaskin,
• Serhii Vasylevskyi,
• Ryota Kabe,
• Xiushang Xu and
• Akimitsu Narita

Beilstein J. Org. Chem. 2025, 21, 270–276, doi:10.3762/bjoc.21.19

• (Supporting Information File 1, Table S2). The longest-wavelength absorption maximum (S0 → S1), attributed to the HOMO → LUMO transition, was calculated to be at 432 nm (f = 0.5674) for 4. Compared to the S1 states in BPP 2 (ε = 1200 M−1 cm−1) and BPP-OiPr 3 (ε = 1800 M−1 cm−1), corresponding to forbidden

• Table S6 and Figure S1 in Supporting Information File 1, the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of BPP-OiPr 3 were calculated to be at −5.15 and −2.00 eV, respectively, with a slightly smaller HOMO–LUMO gap of 3.15 eV compared to that of BPP 2

• (3.24 eV). BPP-dione 4 was revealed to have lower HOMO (−6.18 eV) and LUMO (−3.31 eV) and an even smaller HOMO–LUMO gap of 2.87 eV in agreement with the experimental optical spectra. Nano- and microcrystals of organic semiconductors exhibit great potential in next-generation nanoscale optoelectronics

Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)

• Yongming Xiong,
• Xue Lin Ma,
• Shilong Su and
• Qian Miao

Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1

• to Cs-1 (4.37 eV) as calculated at the B3LYP/6-311++G(d,p) level of DFT. The reduced HOMO–LUMO gap of C2-1 can be attributed to the greater conjugation in the essentially flat dibenzotropone moiety. This finding aligns with the fact that the yellow crystal of C2-1 absorbs light of a longer wavelength

Efficient synthesis of fluorinated triphenylenes with enhanced arene–perfluoroarene interactions in columnar mesophases

• Yang Chen,
• Jiao He,
• Hang Lin,
• Hai-Feng Wang,
• Ping Hu,
• Bi-Qin Wang,
• Ke-Qing Zhao and
• Bertrand Donnio

Beilstein J. Org. Chem. 2024, 20, 3263–3273, doi:10.3762/bjoc.20.270

• possesses higher HOMO and LUMO energy levels than that of the monomer F1, with a smaller HOMO–LUMO energy gap (3.92 eV for F1 versus 4.11 eV for PH1). The DFT results thus agree pretty well with the fluorescence spectra in solution: G66 shows a fluorescence peak at 470–500 nm, while F6 has peaks located

The charge transport properties of dicyanomethylene-functionalised violanthrone derivatives

• Sondos A. J. Almahmoud,
• Joseph Cameron,
• Dylan Wilkinson,
• Michele Cariello,
• Claire Wilson,
• Alan A. Wiles,
• Peter J. Skabara and
• Graeme Cooke

Beilstein J. Org. Chem. 2024, 20, 2921–2930, doi:10.3762/bjoc.20.244

• p-type semiconductors with low HOMO–LUMO gaps (≈1.25 eV). The hole mobilities, measured from fabricated organic field-effect transistors, range from 3.6 × 10−6 to 1.0 × 10−2 cm2 V−1 s−1. We found that the compounds featuring linear alkyl chains (3b and 3c) displayed a higher mobility compared to the

• intermolecular interactions which might result in a narrower HOMO–LUMO gap than that of PDI, and an absorption band extending to the near-infrared (NIR) region [26]. This makes violanthrone and its derivatives potential candidates for NIR optoelectronic applications. In fact, the intrinsic semiconducting

• exhibit a narrow HOMO–LUMO gap (1.46–1.47 eV), with a wide absorption range exceeding 800 nm compared to their previously reported precursors [30]. The electrochemical studies of the three materials show reversible oxidation and reduction waves with EA values that are in a similar range (from −3.70 to

C–C Coupling in sterically demanding porphyrin environments

• Liam Cribbin,
• Brendan Twamley,
• Nicolae Buga,
• John E. O’ Brien,
• Raphael Bühler,
• Roland A. Fischer and
• Mathias O. Senge

Beilstein J. Org. Chem. 2024, 20, 2784–2798, doi:10.3762/bjoc.20.234

• ][5]. Nonplanar porphyrins offer a marked difference in chemical and physical properties when compared to their planar compatriots [6], with relatively smaller HOMO–LUMO gaps resulting in an observed bathochromic shift in the UV–vis absorption spectrum [7]. The phenomenon of nonplanarity results from

Catalysing (organo-)catalysis: Trends in the application of machine learning to enantioselective organocatalysis

• Stefan P. Schmid,
• Leon Schlosser,
• Frank Glorius and
• Kjell Jorner

Beilstein J. Org. Chem. 2024, 20, 2280–2304, doi:10.3762/bjoc.20.196

• properties via descriptors. Apart from molecular vibrations, electronic influences are commonly modelled via global properties of a molecule (such as HOMO/LUMO energies) or local properties (such as natural population analysis (NPA) charges/NMR shifts), as shown in Figure 5 [69][72][88][89]. With respect to

Multicomponent syntheses of pyrazoles via (3 + 2)-cyclocondensation and (3 + 2)-cycloaddition key steps

• Ignaz Betcke,
• Alissa C. Götzinger,
• Maryna M. Kornet and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2024, 20, 2024–2077, doi:10.3762/bjoc.20.178

Radical reactivity of antiaromatic Ni(II) norcorroles with azo radical initiators

• Siham Asyiqin Shafie,
• Ryo Nozawa,
• Hideaki Takano and
• Hiroshi Shinokubo

Beilstein J. Org. Chem. 2024, 20, 1967–1972, doi:10.3762/bjoc.20.172

• to the characteristic forbidden HOMO–LUMO transition of the antiaromatic compound, nonconjugated macrocycle 2a did not possess such an absorption band, indicating the loss of antiaromaticity in 2a. Macrocycle 2a possessed new absorption bands from 600 to 800 nm. The simulated absorption spectrum of

• CH2Cl2 were examined using cyclic voltammetry (Figure 4). Macrocycle 2a exhibited one reversible oxidation wave at 0.44 V and two reversible reduction waves at −0.85 V and −1.14 V. The electrochemical HOMO–LUMO gap of 2a is 1.29 V, which is larger than that of 1a (1.08 V) [2]. DFT calculations We next

2-Heteroarylethylamines in medicinal chemistry: a review of 2-phenethylamine satellite chemical space

• Carlos Nieto,
• Alejandro Manchado,
• Ángel García-González,
• David Díez and
• Narciso M. Garrido

Beilstein J. Org. Chem. 2024, 20, 1880–1893, doi:10.3762/bjoc.20.163

• )-[3H]-baclofen displacement. QSAR studies have been developed in order to examine the pivotal role of the aromatic moiety of baclofen-like compounds [25]. In this sense, the QSAR equation revealed HOMO/LUMO orbital energies are critical for a high correlation with binding strength. An in vivo

Hetero-polycyclic aromatic systems: A data-driven investigation of structure–property relationships

• Sabyasachi Chakraborty,
• Eduardo Mayo Yanes and
• Renana Gershoni-Poranne

Beilstein J. Org. Chem. 2024, 20, 1817–1830, doi:10.3762/bjoc.20.160

• distributions of five molecular properties: highest occupied molecular orbital (HOMO) energy, lowest unoccupied molecular orbital (LUMO) energy, HOMO–LUMO gap (Gap), adiabatic ionization potential (AIP), and adiabatic electron affinity (AEA). As shown in the violin plots in Figure 3B, for all properties, the

• the effect of global structural features on the set of electronic properties detailed above (HOMO, LUMO, Gap, AIP, AEA). At this lowest resolution analysis, we aim to ascertain to what extent the overall molecular size and geometry determines molecular properties. Molecular size The molecular size of

• the HOMO, the lower the LUMO, etc., and the apparent size dependency arises simply because larger molecules have more opportunities to create longer linear stretches. The scatter plot of the HOMO/LUMO space showed that a similar trend does exist for COMPAS-2, albeit weaker than the COMPAS-1 case (see

Synthesis of polycyclic aromatic quinones by continuous flow electrochemical oxidation: anodic methoxylation of polycyclic aromatic phenols (PAPs)

• Hiwot M. Tiruye,
• Solon Economopoulos and
• Kåre B. Jørgensen

Beilstein J. Org. Chem. 2024, 20, 1746–1757, doi:10.3762/bjoc.20.153

• estitmation of the HOMO/LUMO energies to shed more light on this transformation. The easy separation of the supporting electrolyte from the product will allow recycling and makes this a green transformation. Keywords: acetal formation; cyclic voltammetry; flow electrochemistry; green oxidation; polycyclic

Synthesis and optical properties of bis- and tris-alkynyl-2-trifluoromethylquinolines

• Stefan Jopp,
• Franziska Spruner von Mertz,
• Peter Ehlers,
• Alexander Villinger and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 1246–1255, doi:10.3762/bjoc.20.107

• different fine structures. However, TD-DFT calculations using the long-range correlated CAM-B3LYP/6-311G(d,p) level of theory reveal that the lowest energy band for all three derivatives 6a, 9a and 12a originate mainly from a HOMO→LUMO transition with some admixture of HOMO−1→LUMO+1 and HOMO−1→LUMO

Competing electrophilic substitution and oxidative polymerization of arylamines with selenium dioxide

• Vishnu Selladurai and
• Selvakumar Karuthapandi

Beilstein J. Org. Chem. 2024, 20, 1221–1235, doi:10.3762/bjoc.20.105

• process, an electron is transferred from the HOMO of an arylamine donor to the LUMO of the SeO2 acceptor. The computed HOMO–LUMO energy difference (∆E) between arylamines and SeO2 decreased in the following order: o-anisidine − SeO2 > aniline − SeO2 > methyl anthranilate − SeO2. It revealed that the HOMO

Two-fold addition reaction of silylene to C₆₀: structural and electronic properties of a bis-adduct

• Masahiro Kako,
• Masato Kai,
• Masanori Yasui,
• Michio Yamada,
• Yutaka Maeda and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2024, 20, 1179–1188, doi:10.3762/bjoc.20.100

• . Conditions: glassy carbon working electrode; Pt wire counter electrode; SCE reference electrode; 50 mV/s scan rate. Synthesis of silylene adducts 2 and 3. Selected bond lengths and angles of 3. Redox potentialsa (V) of C60, 2, and 3. Calculated HOMO/LUMO levels (eV)a. Supporting Information Supporting

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

• Qian Liu Glen P. Miller Department of Chemistry, University of New Hampshire, 23 Academic Way, Durham, New Hampshire 03864-3598, USA 10.3762/bjoc.20.97 Abstract DFT calculations demonstrate that an isoacenofuran of any size possesses a smaller HOMO–LUMO gap than the corresponding acene bearing an

• -di(2’,4’,6’-triethylphenyl)isobenzofuran are significantly less reactive than 1,3-diphenylisobenzofuran toward the strong dienophiles DMAD and acrylonitrile. The insights gained here suggest that the synthesis of large, persistent, kinetically stabilized isoacenofurans with unusually small HOMO–LUMO

• 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

Structure–property relationships in dicyanopyrazinoquinoxalines and their hydrogen-bonding-capable dihydropyrazinoquinoxalinedione derivatives

• Tural N. Akhmedov,
• Ajeet Kumar,
• Daken J. Starkenburg,
• Kyle J. Chesney,
• Khalil A. Abboud,
• Novruz G. Akhmedov,
• Jiangeng Xue and
• Ronald K. Castellano

Beilstein J. Org. Chem. 2024, 20, 1037–1052, doi:10.3762/bjoc.20.92

• displaying some localization on the dicyanopyrazinopyrazine acceptor. Notably, compound 3a displays the highest orbital density separation between donors and acceptors – an attribute relevant to efficient intramolecular charge transfer processes. This aligns with the observed lower optical HOMO–LUMO gap for

• derivatives 1b–7b, a balance is achieved, characterized by a HOMO with an energy level below –6.0 eV and moderately low LUMO with an energy level below −2.7 eV. The notable computed HOMO–LUMO difference between DCPQs and DPQDs amounting to more than 1.0 eV in certain cases, correlates well with optical gaps