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

• 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

• . Electron-donating N,N-dimethylaminophenyl substituents led to bathochromically shifted absorption and emission spectra accompanied by strongly elevated fluorescence quantum yields (up to 83%). Further studies will be devoted to the synthesis of novel polycyclic uracil derivatives with potential biological

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

• overcoming scalability challenges in quantum technologies. Despite their potential, achieving high luminescence quantum yields has largely been limited to donor-functionalized monoradicals, and a detailed understanding of the luminescent behavior of open-shell organic molecules remains elusive. This review

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

• discovered that simple acylation of the pyrazole moiety leads to increased quantum yields of isomerization, long Z-isomer life-times, good spectral separation, and high photostability. Keywords: azobenzenes; azopyrazoles; photochromism; photoswitches; substituent effects; Introduction Organic photoswitches

• often show higher quantum yields and increased thermal half-life of the metastable state. For the half-life, the choice of the heterocycle is crucial, as revealed through density functional theory (DFT) calculations, which showed that a 5-membered ring promotes the stability of the Z isomer [30]. Within

• irradiation with 445 nm can be explained by the presence of a competing E→Z isomerization at the same wavelength. In general, NAc-PAPs show only a minor substitution effect on the PSD upon irradiation with 365 or 445 nm LED light. Next, we studied the photoisomerization quantum yields (QYs) ΦE→Z and ΦZ→E and

Synthesis and photoinduced switching properties of C₇-heteroatom containing push–pull norbornadiene derivatives

• Daniel Krappmann and
• Andreas Hirsch

Beilstein J. Org. Chem. 2025, 21, 807–816, doi:10.3762/bjoc.21.64

• to QC conversions were either incomplete due to photodecomposition or led to the formation of additional species, it was not feasible to ascertain isomerization quantum yields. Conclusion In summary, we have presented the synthesis and photophysical properties of a library of heterocyclic push–pull

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 UV–vis and fluorescence spectral behavior was similar to those reported for fluorinated [7]helicenes [38]. The fluorescence quantum yields, ΦF of F8-phenacenes were ca. 0.1 (0.08 for F8PIC, 0.12 for F8FUL, and 0.08 for F87PHEN) which were similar to those of the corresponding parent phenacenes

• that, through the fluorination, one can tune the MO energy levels without changing the apparent electronic spectral features in solution, such as, electronic spectral shapes, wavelengths, and fluorescence quantum yields. Such fluorine-substitution effects on electronic spectra and MO levels were

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

• concentrations used for ANTH, 9,10-ANTH(BnF)2, and quinine sulfate were 1.89, 1.14, and 1.94 (10−5 M), respectively. Relative quantum yields were calculated using the following equation referenced to quinine sulfate (Φf = 0.55 in 0.1 M H2SO4): X-ray crystallography The diffraction-quality single crystals of 9

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

• "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

• shown in Table 2. These properties help to explain the variation in photoreactivity. Quantum yields were measured using Me2B as an internal reference, with a value of 33% in acetonitrile, as initially determined by Kosower [19]. While tentative, the low fluorescence quantum yields of these compounds may

• diradical. This triplet diradical undergoes another ISC, returning to the singlet state, which then forms a second single bond (Figure 8). This mechanism, involving both singlet-excited states and triplet states via ISC, is consistent with the relatively low fluorescence quantum yields observed for Cl2B

Synthesis of N-acetyl diazocine derivatives via cross-coupling reaction

• Thomas Brandt,
• Pascal Lentes,
• Jeremy Rudtke,
• Michael Hösgen,
• Christian Näther and
• Rainer Herges

Beilstein J. Org. Chem. 2025, 21, 490–499, doi:10.3762/bjoc.21.36

• contrast to the solubilized parent diazocine. These superior properties make N-acetyl diazocine 1 an ideal candidate for application in the field of photopharmacology especially in aqueous environments [13][14]. The same applies for the quantum yields. While the quantum yields ΦZ→E and ΦE→Z of the parent

• diazocine drop significantly in aqueous media, the corresponding quantum yields of the N-acetyl diazocine stay the same or even slightly improve (Table 1). In general, the quantum yields of parent diazocine and its’ nitrogen bridged derivative exceed the quantum yields of other molecular photoswitches like

• of amino-N-acetyl diazocine by deprotection of the carbamate. Reaction conditions for the attempted Ullmann-type reaction with sodium azide. Reaction conditions for the palladium-catalyzed introduction of a nitrile functionality. Quantum yields of N-acetyl diazocine 1 in organic and aqueous media

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22

• ]. These new isoelectronic tris(diisocyanide)Cr(0) complexes, [Cr(LMes)3] (Mes = mesityl) and [Cr(LPyr)3] (Pyr = pyrenyl), display remarkably high metal-to-ligand charge transfer (MLCT) lifetimes of up to 47 ns and photoluminescence quantum yields as high as 1.04%. This surpasses previously reported first

• transition-metal-based photosensitizers acting by triplet energy transfer for which high singlet oxygen quantum yields are crucial, the silicon phthalocyanins in this study have exhibited relatively low singlet oxygen quantum yield values (around 0.27 for the silicon-based photocatalysts used in this work

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

• fluorescence emission spectroscopies reveal green photoluminescence with fluorescence quantum yields of up to 33% for the Fn derivatives. The J-aggregation for the inner fluorine-substituted dimers Gnm is energetically and stereoelectronically more favorable and G66 exhibits thin-film fluorescence with a large

• (λem = 402 nm for PH8) and 460–500 nm for G66, with absolute quantum yields of 30% and 32%, respectively. Further, their fluorescence spectra in solutions show some solvent polarity influence, with a substantial red shift as the solvent polarity is increased. In thin film, the single luminescence

Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energy

• Robin Schulte,
• Dustin Schade,
• Thomas Paululat,
• Till J. B. Zähringer,
• Christoph Kerzig and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 3061–3068, doi:10.3762/bjoc.20.254

• -bromonorbornadiene and the corresponding arylacetylenes. The norbornadienes showed absorption maxima in the range of 310–345 nm and long-wavelength zero onsets of up to 420 nm. The photoisomerization quantum yields were as high as 59% per photoisomerization event and the resulting quadricyclanes showed half-lives of

• be investigated in the presence of the photosensitizer because these substrates have no sufficient solubility in acetonitrile. To assess the efficiency of the photoreactions, photoisomerization quantum yields were determined in cyclohexane by actinometry (λex = 310 nm or 340 nm) [41][42]. The quantum

• yields varied from only 1% per conversion event, i.e. per norbornadiene unit, for the naphthyl-substituted derivative 1n to 59% for the m-phenyl-linked derivative 1k (Table 1). In general, the derivatives 1h–l,n showed significantly lower quantum yields than the 3-cyano-substituted derivatives 1d and 1f

Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide

• Parvathy Mini,
• Michael R. Grace,
• Genevieve H. Dennison and
• Kellie L. Tuck

Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237

• glutathione. The change in luminescence emission spectra (λex = 250 nm) of the solutions was also investigated after the subsequent addition of 1.0 molar equivalent of 1 mM Na2S(aq). Quantum yields. The quantum yield (φ) was determined using a quinine sulfate standard (φ = 0.55) for Tb·1, in water at pH 7.4

Synthesis of benzo[f]quinazoline-1,3(2H,4H)-diones

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

Beilstein J. Org. Chem. 2024, 20, 2708–2719, doi:10.3762/bjoc.20.228

• displayed in Figure 3. The corresponding photophysical data and quantum yields are described in Table 2. The analysis of the absorption spectra revealed well-resolved bands for derivatives 5a, 5d, 5f, 5g, and 5i for short wavelengths (250–300 nm). At higher wavelength (300–450 nm) broad absorption bands

• , the presence of N,N-dimethylamino groups leads to strongly enhanced quantum yields up to 71%. The highest quantum yield is observed for 5d (71%), followed by 5f with 51%. However, the presence of a pair of donor and acceptor groups appears to be disadvantageous in terms of quantum yield and the

• presence of only one donor group is advantageous. Interestingly, the quantum yields of 5a (12%), 5g (13%), 5h (8%), and 5i (3%) are comparatively lower than in case of 5g and 5f. It is reasonable to assume that this large difference is caused by the chosen substitution pattern and can be used for further

Photoluminescence color-tuning with polymer-dispersed fluorescent films containing two fluorinated diphenylacetylene-type fluorophores

• Kazuki Kobayashi,
• Shigeyuki Yamada,
• Motohiro Yasui and
• Tsutomu Konno

Beilstein J. Org. Chem. 2024, 20, 2682–2690, doi:10.3762/bjoc.20.225

• crystalline state. The PL wavelengths (λPL), fluorescence quantum yields (ΦPL), fluorescence lifetimes (τPL), and Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of the PMMA dispersion films containing 1 wt % of compounds 1a–g are summarized in Table 1. The PMMA dispersion films

• 10 s. For photophysical measurements, thin and smooth films were prepared by spin-coating followed by solvent evaporation. Photophysical properties The PL spectra and quantum yields were measured using a Quantaurus-QY C11347-01 absolute PL quantum yield spectrometer (Hamamatsu Photonics, Japan). The

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

• synthesized 4 halopyrazoles 111 and their Suzuki products 110 fluoresce blue in solution and have quantum yields of 29–72 % (Scheme 40) [137]. The Suzuki coupling can also be used for the functionalization of pyrazoles. For this purpose, p-bromo-substituted terminal alkynes 112, acyl chlorides 114, and

• pathway enables the synthesis of 3,5-bis(biphenyl)-1-methyl pyrazole. To stabilize the catalyst, additional triphenylphosphane is added as a ligand during the Suzuki coupling. The resulting products fluoresce blue, with the five biaryl-substituted derivatives 113 showing the highest quantum yields of up

A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions

• Vitor A. S. Almodovar and
• Augusto C. Tomé

Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169

• region [3][4]. In turn, N-substituted DPP derivatives are soluble in common organic solvents, exhibit large molar extinction coefficients, Stokes shifts in the range of 10–70 nm and high fluorescence quantum yields [5][6][7]. Due to their outstanding photophysical properties, DPP-based dyes have been

• fluorescence quantum yields, ranging from 0.66 to 0.83, confirming their potential applications in fluorescence imaging, sensors, and optoelectronic devices. A comprehensive discussion of the potential uses of these fluorescent substances in areas such as materials science, biology, or chemistry may provide a

• the resulting compounds were isolated in reasonable yields. The newly synthesized compounds display high fluorescence quantum yields and moderate Stokes shifts, which are crucial attributes for their potential application in diverse fields, particularly in biological or technical applications

The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)

• Cristina Martini,
• Muhammad Idham Darussalam Mardjan and
• Andrea Basso

Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162

A fiber-optic spectroscopic setup for isomerization quantum yield determination

• Anouk Volker,
• Jorn D. Steen and
• Stefano Crespi

Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150

• setup for isomerization quantum yield determination is reported. The setup combines fiber-coupled LEDs, a commercially calibrated thermopile detector for measurement of the photon flux, and a fiber-coupled UV–vis spectrometer. By solving the rate equations numerically, isomerization quantum yields can

• be obtained from the UV–vis absorption spectra. We show that our results for the prototypical photoswitch azobenzene are in excellent agreement with the literature. The analysis of the errors showed that the quantum yields determined using this method are in the same order of magnitude as when using

• εtrans/εcis is the highest, results in the formation of >95% cis-azobenzene [17]. The quantum yields (Φ) of isomerization of this process have been determined using different irradiation wavelengths, solvents, and methods [18][19][20][21][22][23][24]. One of the most interesting properties of azobenzene

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

• first insights on how the optical properties can be fine-tuned by the substitution pattern of the arylalkyne. The key optical properties are summarized in Table 2. All molecules display relatively high quantum yields (QYs) with the highest being 0.66 for 6a and the lowest 0.54 for 12a. This is in

• investigated via steady-state absorption and fluorescence spectroscopy and gives first insights into the structure–optical property relationship of polyalkynylated quinolines. In particular, high fluorescence quantum yields have been determined for all studied compounds. Variation of the substitution pattern

Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis

• Johannes Rocker,
• Till J. B. Zähringer,
• Matthias Schmitz,
• Till Opatz and
• Christoph Kerzig

Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106

• cage escape quantum yields [67][68]. Aza-H exhibits a relatively long singlet lifetime of 9.6 ns (see Figure 4E), which is sufficient for diffusion-controlled energy or electron transfer at moderate substrate concentrations. Transient absorption (TA) spectra of an Ar-saturated Aza-H solution were

Synthesis and properties of 6-alkynyl-5-aryluracils

• Ruben Manuel Figueira de Abreu,
• Till Brockmann,
• Alexander Villinger,
• Peter Ehlers and
• Peter Langer

Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80

• photophysical properties is displayed in Figure 4. Corresponding photophysical data and quantum yields are described in Table 2. The analysis of the absorption spectra revealed that the spectra can be divided into a short-wave and long-wave region. In the long wavelength region (350–500 nm) all measured

• observed, despite the presence of the π-donor group at the same position. However, a shoulder on the emission peak was observed, which may indicate the influence of the double bond. Finally, the quantum yields of all compounds were determined and compared. Compound 5f afforded the highest quantum yield

Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group

• Vladimir P. Rybalkin,
• Sofiya Yu. Zmeeva,
• Lidiya L. Popova,
• Irina V. Dubonosova,
• Olga Yu. Karlutova,
• Oleg P. Demidov,
• Alexander D. Dubonosov and
• Vladimir A. Bren

Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47

• cells (l = 1 cm, V = 2 mL). Fluorescence quantum yields were determined relatively to (Z)-N-((3-oxobenzo[b]thiophen-2(3H)-ylidene)methyl)-N-phenylacetamide as a standard (φfl = 0.16 ± 0.005) [14][33]. Stock solutions of compounds 2a–c (c 1.0 × 10–4 mol⋅L−1) and metal perchlorates (c 2.0 × 10–4 mol⋅L−1

• , and quantum yields of the 2a–c→3a–c rearrangementa. Supporting Information Supporting Information File 26: Experimental procedures and characterization data for all new compounds 1, 2a–c and 3a–c. Supporting Information File 27: 1H and 13C NMR, IR and HRMS spectra of all novel compounds. Supporting

Switchable molecular tweezers: design and applications

• Pablo Msellem,
• Maksym Dekthiarenko,
• Nihal Hadj Seyd and
• Guillaume Vives

Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45

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

• the reaction of A ↔ B using experimental absorption spectra of the initial form A and two photostationary states (PSS) obtained at two different wavelengths [48]. In 1968, Ross and Blanc for the first time applied the Fischer method to calculate the extinction coefficients and quantum yields of the

• nm laser, compound 17a exhibited pronounced negative photochromism. The thermal backward reaction occurred within 120 min in the dark in acetonitrile. The photoisomerization quantum yields for compounds 17a (φZ→E = 0.13, φE→Z = 0.46), 17b (φZ→E = 0.01, φE→Z = 0.02), and 17c (φZ→E = 0.06, φE→Z = 0.20

• the photoreaction, is advantageous for applications in bulk materials because the photoisomers have decreased absorbance at the excitation wavelength [9]. Depending on the substitution pattern, the quantum yields for the E–Z photoisomerization of indigo photochromes vary from 0.001 to 0.46 and the

Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes

• Michio Yamada

Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13

• , 639, and 594 nm, with fluorescence quantum yields of 6.1%, 7.5%, 1.6%, and 7.8%, respectively, when dissolved in cyclohexane. Notably, the photoluminescence characteristics of these compounds depend on the solvent polarities, as evidenced by the observed decrease in the fluorescence quantum yields in

• broad emission spectra encompassing the entire visible region, featuring two peaks centered at 430–472 and 633 nm. The fluorescence quantum yields estimated for 73, 74, and 75 in acetonitrile are 3.4%, 3.3%, and 4.3%, respectively. Notably, in the case of 74 and 75, the intensity of the long-wavelength