Understanding the origin of stereoselectivity in the photochemical denitrogenation of 2,3-diazabicyclo[2.2.1]heptene and its derivatives with non-adiabatic molecular dynamics

• Leticia A. Gomes and
• Steven A. Lopez

Beilstein J. Org. Chem. 2025, 21, 2007–2020, doi:10.3762/bjoc.21.156

• fluorescence decay, suggesting that the N2 is not released at S1 state [80]. Roth and co-workers discovered a preference to form the inverted product exo-2 from deuterated diazabicyclo[2.1.1]hex-2-ene (1) (Scheme 2) [71]. Adam and co-workers performed photochemical reactions with derivatives of 1, including 3

• static MEP calculation, the experimental quantum yield (Φ = 0.97–1.00) is inconsistent with this static analysis, since it suggests a non-productive and fluorescence pathway. We hypothesize that these S1 minima are shallow excited-state minima that can be escaped towards a productive region of the

Synthesis of N-doped chiral macrocycles by regioselective palladium-catalyzed arylation

• Shuhai Qiu and
• Junzhi Liu

Beilstein J. Org. Chem. 2025, 21, 1917–1923, doi:10.3762/bjoc.21.149

• revealed the formation of isomeric products depending on the substituents on the N atoms. Notably, two intrinsically chiral macrocycles MC1 and MC3 with C1 symmetry were successfully obtained. These macrocycles exhibit exceptional photophysical properties, particularly remarkable high fluorescence quantum

• , these macrocycles show blue to green emissions with high fluorescence quantum yields (ΦF up to 0.69). Owing to the existence of inherent chirality, two enantiomers of N-doped macrocycle MC1 were successfully isolated by chiral resolution, enabling detailed investigation of its chiroptical properties

• demonstrated the synthesis and characterizations of N-doped macrocycles MC1–3 by palladium-catalyzed arylations. The molecular structures of the macrocyclic precursors and targets were unambiguously revealed by X-ray crystallographic characterization. These macrocycles exhibit strong fluorescence with ΦF

Photoswitches beyond azobenzene: a beginner’s guide

• Michela Marcon,
• Christoph Haag and
• Burkhard König

Beilstein J. Org. Chem. 2025, 21, 1808–1853, doi:10.3762/bjoc.21.143

• ) [112]. Examples The Aprahamian group reported hydrazone 121, which is emissive in its Z-isomer. The fluorescence can be switched on and off by irradiation with 442 nm and 340 nm, respectively (Scheme 37) [114]. The photophysical and emissive properties were also maintained in bovine serum, in the solid

Research progress on calixarene/pillararene-based controlled drug release systems

• Liu-Huan Yi,
• Jian Qin,
• Si-Ran Lu,
• Liu-Pan Yang,
• Li-Li Wang and
• Huan Yao

Beilstein J. Org. Chem. 2025, 21, 1757–1785, doi:10.3762/bjoc.21.139

• maintain water solubility. This assembly approach not only suppresses the fluorescence self-quenching of AnPy in the aggregated state (enhancing the yield of singlet oxygen) [115], but also boosts its photo-sensitivity – under light irradiation, the anthracene in the complex can be efficiently converted to

On the aromaticity and photophysics of 1-arylbenzo[a]imidazo[5,1,2-cd]indolizines as bicolor fluorescent molecules for barium tagging in the study of double-beta decay of ¹³⁶Xe

• Eric Iván Velazco-Cabral,
• Fernando Auria-Luna,
• Juan Molina-Canteras,
• Miguel A. Vázquez,
• Iván Rivilla and
• Fernando P. Cossío

Beilstein J. Org. Chem. 2025, 21, 1627–1638, doi:10.3762/bjoc.21.126

• in the optimized S1 state, thus suggesting a less modular aromatic character. Unfortunately, since the HOMA parameters for excited states [29] are available for triplet 3ππ* states only and we are interested in fluorescence emission spectra, this kind of quantitative assessment of aromaticity was not

• + prompted us to compare the photophysical properties of unbound compound 18 in the presence of Ba(ClO4)2. The values corresponding to the adiabatic absorption (S0(optimized) → S1*, adiabatic absorption) and emission (S1(optimized) → S0, fluorescence) are reported in Table 2, together with the differences

• responsible for the bicolor behavior of the sensor. Interaction with barium perchlorate results in a slightly different coordination pattern, although the bicolor behavior observed in the experimental fluorescence spectra is preserved. These photophysical properties were observed in DFT and TDDFT calculations

Synthesis of optically active folded cyclic dimers and trimers

• Ena Kumamoto,
• Kana Ogawa,
• Kazunori Okamoto and
• Yasuhiro Morisaki

Beilstein J. Org. Chem. 2025, 21, 1603–1612, doi:10.3762/bjoc.21.124

• -handed double helical compounds [31][32][33][34] and chiral nanohoops [35][36] emitting circularly polarized fluorescence have been reported. In this study, enantiopure ribbon-shaped compounds based on planar chiral tetrasubstituted [2.2]paracyclophane were used as chiral monomers, and optically active

• solutions (1.0 × 10−5 M) of (Sp)-6 and (Sp)-7 were photo-excited around their absorption peak maxima, and both oligomers emitted blue fluorescence as shown in Figure 1. Their PL spectra with vibrational structures were identical, and the PL quantum efficiencies (ΦPL) of both (Sp)-6 and (Sp)-7 were estimated

• lifetime measurement was performed on a Hamamatsu Photonics Quantaurus-Tau fluorescence lifetime spectrometer system. Specific rotations ([α]Dt) were measured with a HORIBA SEPA-500 polarimeter: concentration “c” is g/dL. Circular dichroism (CD) spectra were recorded on a JASCO J-1500 spectropolarimeter

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

• local excited (LE) and charge-transfer (CT) states can be experimentally observed as dual fluorescence: a structured, higher-energy emission from the LE state and a broad, red-shifted emission from the CT state [8][9]. Classical systems such as 4-(N,N-dimethylamino)benzonitrile (DMABN) and pyrene-o

• LE band of the Pe moiety. This result suggests that a stronger CT character leads to a lower overall fluorescence quantum yield. The Φf in other solvents are shown in Table S1 (Supporting Information File 1). In addition, a gradual increase in the emission intensity around 500–520 nm is observed with

• based on fluorescence lifetime measurements in the following section. Since the CT states of these molecules exhibit emissive properties, their excited-state lifetimes were determined from emission decay measurements. Time-resolved fluorescence measurements revealed that the decays of the CT emission

Synthesis of an aza[5]helicene-incorporated macrocyclic heteroarene via oxidation of an o-phenylene-pyrrole-thiophene icosamer

• Yusuke Matsuo,
• Aoi Nakagawa,
• Shu Seki and
• Takayuki Tanaka

Beilstein J. Org. Chem. 2025, 21, 1561–1567, doi:10.3762/bjoc.21.119

• in detail. Keywords: cyclophane; fluorescence; heterohelicene; intramolecular oxidative coupling; Introduction Conjugated macrocyclic polyarenes have attracted significant attention due to their stimuli-responsive optoelectronic properties, dynamic structural changes, and host–guest interactions [1

• structural relaxation in the excited state. The fluorescence quantum yield (ΦF) was determined as 0.078 (λex = 300 nm), and the fluorescence lifetime (τ) using biexponential decay model fitting as 1.7 and 4.4 ns. The partially fused structure of 5 exhibited a well-defined lowest-energy absorption band peaked

• , the ΦF value was modest (0.072), which is lower than those of related aza[n]helicene analogs [27][28]. The fluorescence lifetime (τ) was determined by biexponential decay model fitting as 0.65 and 3.2 ns. DFT calculation was conducted to investigate the electronic structure. The HOMO and HOMO−1 are

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

• containing one or two exocyclic olefin units. Owing to the transformation of carbonyl groups, the resulting products exhibit several unique physical and chemical properties: (1) the enhancement of configurational stability, (2) the appearance of fluorescence, and (3) the reductive carbon–carbon-bond

• peripherally modified CBBC derivatives have also been prepared and were shown to have fascinating properties [17][18][19][20][21]. For example, carbazole-substituted donor–acceptor-type CBBC derivatives exhibit both efficient circularly polarized luminescence (CPL) and thermally activated delayed fluorescence

Advances in nitrogen-containing helicenes: synthesis, chiroptical properties, and optoelectronic applications

• Meng Qiu,
• Jing Du,
• Nai-Te Yao,
• Xin-Yue Wang and
• Han-Yuan Gong

Beilstein J. Org. Chem. 2025, 21, 1422–1453, doi:10.3762/bjoc.21.106

• fluorescence (TADF), and chiral sensing. Notably, recent developments have yielded π-extended, structurally robust, and stimuli-responsive azahelicenes exhibiting record-high dissymmetry factors (|gabs| and |glum|), elevated CPL brightness (BCPL), and efficient integration into CPL-OLEDs and redox-switchable

• absorption and emission maxima (λabs = 399 nm, λem = 405 nm), a fluorescence quantum yield (ΦF) of 0.13, and high dissymmetry factors (|gabs| = 1.9 × 10−2, |gabs| = 9.5 × 10−3 at 403 nm) [18] (Table 2). Miura and co-workers employed Pd(II)/Ag(I)-catalyzed cyclizations to construct azahelicenes, with compound

• intramolecular Scholl reactions [24] (Table 3). All compounds exhibited strong absorption in the UV–vis region (250–450 nm) and fluorescence emission between 400–550 nm. Among these, compound 11c, a saddle-shaped dibenzodiaza[8]circulene, was particularly noteworthy as the first example of its kind synthesized

Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds

• Lidia Zaharieva,
• Vera Deneva,
• Fadhil S. Kamounah,
• Nikolay Vassilev,
• Ivan Angelov,
• Michael Pittelkow and
• Liudmil Antonov

Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105

• crystal was used and the samples were scanned 128 times. The UV–vis spectra were measured on a Jasco V-570 UV–vis–NIR spectrophotometer using spectral grade solvents in the concentration range ≈10−5 mol/L. The steady-state fluorescence spectra were recorded with a FluoroLog 3-22 (HORIBA

N-Salicyl-amino acid derivatives with antiparasitic activity from Pseudomonas sp. UIAU-6B

• Joy E. Rajakulendran,
• Emmanuel Tope Oluwabusola,
• Michela Cerone,
• Terry K. Smith,
• Olusoji O. Adebisi,
• Adefolalu Adedotun,
• Gagan Preet,
• Sylvia Soldatou,
• Hai Deng,
• Rainer Ebel and
• Marcel Jaspars

Beilstein J. Org. Chem. 2025, 21, 1388–1396, doi:10.3762/bjoc.21.103

• cell line are given below), after which the Alamar Blue cell viability reporter was added and the fluorescence recorded using an FLx 800 plate reader (BioTek) with excitation wavelength 535/540 nm and emission wavelength at 590/610 nm using Gen5 Reader Control 2.0 Software (BioTek). EC50 values were

• 20 μL Alamar Blue (0.125 mg/mL resazurin salt in PBS) was added to all wells and incubated for a further 6 hours before fluorescence recording. Structures of the pseudomonins D–G (1–4), pseudomonine (5), pseudomonin B (6) and salicylic acid (7). Key HMBC, 1H-1H COSY and NOE correlations. Extracted

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

• , it was reported that PAH 126 exhibits anti-Kasha fluorescence [80] from the S3 state in the range of 410–470 nm upon excitation at 370 nm. This was well verified by femtosecond time-resolved absorption spectroscopy (fs-TAS), with corresponding high-energy excited state absorption bands observed at

• optical absorption. The UV–vis absorption spectra, fluorescence properties and 1H NMR spectroscopy, indicate that 150 and 151 can be protonated to form the corresponding tropylium cation and consecutive dication under acidic conditions, with reversible protonation−deprotonation capabilities. Additionally

• benzenoid part of the precursor (Scheme 23) [106]. As a result, the reaction of precursor 177 with P(OEt)3 gave fused π-scaffold 178 in 40% yield. Compound 178 features a highly planar geometry, narrow optical band gaps, anti-Kasha fluorescence, and reversible stimuli-responsiveness to acid and base. Gao

Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents

• Jiangfei Chen,
• Yi-Lin Qu,
• Ming Yuan,
• Xiang-Mei Wu,
• Heng-Pei Jiang,
• Ying Fu and
• Shengrong Guo

Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98

Investigations of amination reactions on an antimalarial 1,2,4-triazolo[4,3-a]pyrazine scaffold

• Henry S. T. Smith,
• Ben Giuliani,
• Kanchana Wijesekera,
• Kah Yean Lum,
• Sandra Duffy,
• Aaron Lock,
• Jonathan M. White,
• Vicky M. Avery and
• Rohan A. Davis

Beilstein J. Org. Chem. 2025, 21, 1126–1134, doi:10.3762/bjoc.21.90

• °C in 5% CO2. At 6 h, 5 µL of 600 µM resazurin, diluted in growth media, was added. Plates were further incubated for 6 h and measured for fluorescence at 530 nm excitation and 595 nm emission. The % inhibition was calculated using 0.4% DMSO (no inhibition) and 50 μM puromycin (100% inhibition) data

Biobased carbon dots as photoreductants – an investigation by using triarylsulfonium salts

• Valentina Benazzi,
• Arianna Bini,
• Ilaria Bertuol,
• Mariangela Novello,
• Federica Baldi,
• Matteo Hoch,
• Alvise Perosa and
• Stefano Protti

Beilstein J. Org. Chem. 2025, 21, 1024–1030, doi:10.3762/bjoc.21.84

• tail extending to the visible region. The emission properties of the synthesized CDs were also investigated and the results are summarized in Table 2. The fluorescence quantum yield strongly depends on the nature of the starting substrates, as is apparent by comparison of the value obtained for

• product was detected. Conclusion The results arising from cyclic voltammetry analyses, along with the Stern–Volmer fluorescence quenching data and with the isolated products and the GC yields obtained when irradiating the carbon dots in the presence of triarylsulfonium salts, indicate that carbon dots are

• the examined CDs. Quenching constants of the CDs calculated on the fluorescence intensity. Light-mediated reduction of triarylsulfonium salts in the presence of the CDs examined in this work. Supporting Information Supporting Information File 22: Experimental details, photophysics of CDs, cyclic

Synthesis of pyrrolo[3,2-d]pyrimidine-2,4(3H)-diones by domino C–N coupling/hydroamination reactions

• Ruben Manuel Figueira de Abreu,
• Robin Tiedemann,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2025, 21, 1010–1017, doi:10.3762/bjoc.21.82

• Abstract A variety of pyrrolo[3,2-d]pyrimidine-2,4(3H)-diones were prepared by a combination of Sonogashira reaction and subsequent cyclization by domino C–N coupling/hydroamination reaction. The optical properties (UV–vis absorption and fluorescence) depend on the substitution pattern of the compounds

• amino group. The corresponding fluorescence quantum yields were also strongly affected by the substitution pattern of the pyrrolouracils. Compounds 4k and 4l show very high fluorescence quantum yields of 83% and 71%, respectively, what might be reasoned by the strong donor ability of the NMe2-functional

• groups of those compounds. In contrast, compounds 4a and 4m showed only weak fluorescence with quantum yields of 9 and 4%, respectively. Compound 4j exhibited almost no emission (Φ = 0.1%). [30]. Conclusion In summary, we developed a new methodology for the synthesis of pyrrolo[3,2-d]pyrimidine-2,4(3H

On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals

• Daniel Straub,
• Markus Gross,
• Mona E. Arnold,
• Julia Zolg and
• Alexander J. C. Kuehne

Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80

• perchlorotriphenylmethyl (PTM) or tris(2,4,6-trichlorophenyl)methyl (TTM) radicals degrades to half of their intensity within just a few minutes, while for their corresponding di- and multiradicals no fluorescence data is reported at all (see Figure 1a for chemical structures) [5][6]. However, research on fluorescent

• demonstration of LEDs with 100% internal quantum efficiency [8][12]. Modern approaches also incorporate light-emitting TTM radical derivatives into LEDs based on thermally activated delayed fluorescence to moderate excited triplet, doublet, and singlet states in an attempt to improve the overall device and

• mechanisms and reasons behind the fluorescence color and the fluorescence quantum yield and derive structure–optical property relationships. We will provide the reader with an overview of the perspectives and challenges of open-shell light-emitting radicals and discuss what to do to solve the remaining

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

• (RAFT) polymerization [18]. Moreover, in 2022, Zysman-Colman and collaborators showed that molecule 3, initially synthesized as a TADF (thermally activated delayed fluorescence) emitter [14], can be used as a PC under electron-transfer (ET) and energy-transfer (EnT) processes (Figure 1a) [19]. All the

• transfer (CT) character in scaffolds 4a and 6a can be attributed to the absence of a complete conjugated system. On the other hand, the fluorescence profile showed more differences in the analysis of the three members of the D–A family. Again, 5a revealed a bathochromic effect compared with the less

• 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

Orthogonal photoswitching of heterobivalent azobenzene glycoclusters: the effect of glycoligand orientation in bacterial adhesion

• Leon M. Friedrich and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2025, 21, 736–748, doi:10.3762/bjoc.21.57

• protocol [41], the fluorescent GFP (green fluorescent protein)-expressing strain PKL1162 was applied to mannan-coated microtiter plates. In this assay, fluorescence intensity correlates with the number of adhered bacterial cells. The photoswitches 1–5 (cf. Figure 1) were used as inhibitors of bacterial

Origami with small molecules: exploiting the C–F bond as a conformational tool

• Patrick Ryan,
• Ramsha Iftikhar and
• Luke Hunter

Beilstein J. Org. Chem. 2025, 21, 680–716, doi:10.3762/bjoc.21.54

Photochemically assisted synthesis of phenacenes fluorinated at the terminal benzene rings and their electronic spectra

• Yuuki Ishii,
• Minoru Yamaji,
• Fumito Tani,
• Kenta Goto,
• Yoshihiro Kubozono and
• Hideki Okamoto

Beilstein J. Org. Chem. 2025, 21, 670–679, doi:10.3762/bjoc.21.53

• fluorination on the electronic features of phenacene molecules. F8-Phenacenes were conveniently synthesized by the Mallory photoreaction of the corresponding fluorinated diarylethenes as the key step. Upon fluorination on the phenacene cores, the absorption and fluorescence bands of the F8-phenacenes in CHCl3

• systematically red-shifted by ca. 3–5 nm compared to those of the corresponding parent phenacenes. The vibrational progressions of the absorption and fluorescence bands were little affected by the fluorination in the solution phase. In the solid state, the absorption band of F8-phenacenes appeared in the similar

• wavelength region for the corresponding parent phenacenes whereas their fluorescence bands markedly red-shifted and broadened. These observations suggest that the intermolecular interactions of excited-state F8-phenacene molecules are significantly different from those of the corresponding parent molecules

Binding of tryptophan and tryptophan-containing peptides in water by a glucose naphtho crown ether

• Gianpaolo Gallo and
• Bartosz Lewandowski

Beilstein J. Org. Chem. 2025, 21, 541–546, doi:10.3762/bjoc.21.42

• binds free tryptophan selectively in aqueous media. Furthermore, it is capable of binding to tryptophan within model tripeptides. The naphthalene functionality in the glucose-derived receptor enables the study of guest binding using fluorescence spectroscopy. Keywords: amino acids; macrocyclic

• in water [21]. Crown ether 1 is particularly suited for the sensing of Trp methyl ester, which it binds with a higher affinity than the Phe and Tyr esters. Additionally, the binding of Trp-OMe results in a highly efficient fluorescence quenching of the naphthalene unit in the receptor. Herein, we

• acids in H2O by 1 was investigated by ITC measurements and titration experiments monitored by fluorescence spectroscopy. The results are summarized in Table 1. Receptor 1 binds tryptophan with the highest affinity among the investigated amino acids (entry 1, Table 1). The Ka of the complex between 1 and

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

• photostability compared to ANTH and 9,10-ANTH derivatives, and a simple synthetic access makes it an attractive material as a deep-blue OLED emitter and an efficient fluorescent probe. Keywords: anthracene; dibromoanthracene; electron poor polyaromatic systems; fluorescence; perfluoroalkylation

• to suppress undesirable fluorescence self-quenching [15]. Not only do bulky substituents disrupt intermolecular interactions of this type, they can also provide higher chemical stability and reduce or prevent the photodimerization and photo-oxidation to which all acenes are prone [13]. Furthermore

• because isolated electronically excited molecules are more likely to undergo fluorescence instead of non-radiative relaxation, as discussed in some literature [13]. At the same time, it should be noted that emission properties in the crystalline phase and amorphous films, which are often used in OLED

Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye

• Metodej Dvoracek,
• Brendan Twamley,
• Mathias O. Senge and
• Mikhail A. Filatov

Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37

• promising strategy for synthesizing substituted cyclobutanes without the need for ultraviolet irradiation. Keywords: bimane; [2 + 2] cycloaddition; fluorescence; topochemical polymerization; X-ray crystallography; Introduction Topochemical polymerizations refer to polymerization reactions occurring in the

• "bimanes" is derived from the Latin ‘bi’ (two) and ‘manus’ (hand). syn-Bimanes are often characterized by high fluorescence quantum yields, ranging from 60% to 100% [17], while anti-isomers typically exhibit phosphorescence [18]. Figure 1b illustrates the two isomers along with their simplified naming

• ¹H NMR spectra remained unchanged compared to the neat compounds (Figures S1, S3, and S5, Supporting Information File 1), confirming that the reaction occurs selectively in the solid state. Cl2B was also irradiated in DCM with the same 405 nm LEDs, in a quartz fluorescence cuvette. A UV–vis spectrum