Automated high-content imaging for cellular uptake, from the Schmuck cation to the latest cyclic oligochalcogenides

• Rémi Martinent,
• Javier López-Andarias,
• Dimitri Moreau,
• Yangyang Cheng,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2020, 16, 2007–2016, doi:10.3762/bjoc.16.167

• striking even for the naked eye. A comparison of the respective images confirmed a massive off-target emission of 26 in the former, with r2 = 0.626 (Figure 10b, red, arrows) and little off-target emission in the latter, with r2 = 0.983 (Figure 7b, red, arrows). Masking of the regions with the intense GFP

• Figure 10c). This selection removed about 80% of all cells, and only the top 20% were kept for further analysis. However, applying a cell body mask to this remaining 20%, the fitting of r2 = 0.621 of the GFP and the 26 emission did not improve either (Figure 10c, cyan, including yellow and Figure 11c

• ). The inspection of the images confirmed that even the selected cells showed a significant off-target emission of 26 (Figure 10d, red, arrows). The masking of the Golgi apparatus, based on the GFP emission in the selected cells, was applied next to remove this off-target staining from 26 (Figure 11c

Controlling the stereochemistry in 2-oxo-aldehyde-derived Ugi adducts through the cinchona alkaloid-promoted electrophilic fluorination

• Yuqing Wang,
• Gaigai Wang,
• Anatoly A. Peshkov,
• Ruwei Yao,
• Muhammad Hasan,
• Manzoor Zaman,
• Chao Liu,
• Stepan Kashtanov,
• Olga P. Pereshivko and
• Vsevolod A. Peshkov

Beilstein J. Org. Chem. 2020, 16, 1963–1973, doi:10.3762/bjoc.16.163

• -triggered complexation with boron trifluoride diethyl etherate. The resulting O,O-chelated boron complexes 11 turned out to be strong solid-state emitters featuring clear aggregation-induced emission (AIE) characteristics [61]. Encouraged by these results, we decided to attempt the reaction of 2-oxo

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• chemosensors, ligands, and fluorescent probes. In order to investigate the fluorescence properties, compound 2bA was chosen as the model substrate for optimization of various parameters like time, concentration, and solvent. In order to obtain the maximum emission, various solvents were screened. The

• measurement of UV–vis absorption and fluorescence emission of the samples, stock solutions of 1.0 mM concentration were prepared using analytical grade CHCl3 as the solvent, and diluted to the final concentration of 4.0 μM. Next, we carefully measured the photophysical properties at room temperature including

• absorption, excitation, emission, Stokes shift, fluorescence quantum efficiency, molar extinction coefficient, and brightness. The photophysical data of the β-carboline C1 or C3-tethered benzothiophenone derivatives are summarized in Table 2, and their graphical data are depicted in Figure 3 and Figure 4

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• emission behavior. Keywords: bromoarylaldehydes; click-chemistry; fluorenes; fluorescence; phosphorescence; Introduction Small organic luminophores exhibiting room-temperature phosphorescence (RTP) have attracted great attention due to promising applications in optoelectronic devices [1][2][3][4][5][6][7

• inert conditions [28] are necessary to facilitate an afterglow emission. Most phosphorescence studies are focused on metal complexes due to a strong heavy atom-induced spin-orbit coupling [29][30][31][32][33]. Considering the high price and the toxicity of many metal complexes, pure organic phosphors

• azide state and the linked triazole state, on the emission properties of these compounds (Figure 1). Results and Discussion Syntheses para- and ortho-bromobenzaldehyde 3 and 4 We initiated our synthetic investigations towards azide-functionalized para-bromobenzaldehyde 3 with a two-step sequence

Pauson–Khand reaction of fluorinated compounds

• Jorge Escorihuela,
• Daniel M. Sedgwick,
• Alberto Llobat,
• Mercedes Medio-Simón,
• Pablo Barrio and
• Santos Fustero

Beilstein J. Org. Chem. 2020, 16, 1662–1682, doi:10.3762/bjoc.16.138

• use, fluorine-containing molecules have also found key applications in the field of medical diagnosis. Two of the most powerful imaging techniques used nowadays, positron-emission tomography (PET) and magnetic resonance imaging (MRI), are routinely carried out using fluorine-containing organic

• compounds [8][9]. The former takes advantage of the superb properties of the 18F-radioisotope as positron emitter (t1/2 = 109 min, 97% β+ emission), while the latter benefits from the excellent performance of the 19F isotope in NMR (100% natural abundance, high sensitivity, lack of endogenous background

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

Synthesis of new fluorescent molecules having an aggregation-induced emission property derived from 4-fluoroisoxazoles

• Kazuyuki Sato,
• Akira Kawasaki,
• Yukiko Karuo,
• Atsushi Tarui,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2020, 16, 1411–1417, doi:10.3762/bjoc.16.117

• synthesized and investigated for their photochemical properties. The introduction of a fluorine substituent into 3,5-diarylisoxazoles led to an increase of fluorescence intensity and exhibited a redshift in the emission intensity. α-Fluorinated boron ketoiminates (F-BKIs) were also synthesized via a ring

• -opening reaction of 4-fluoroisoxazoles and exhibited highly fluorescent luminescence and aggregation-induced emission (AIE), showing promise as a new fluorophore. Keywords: aggregation-induced emission; boron ketoiminates; fluorescent probe; α-fluorinated boron ketoiminates; 4-fluoroisoxazoles

• concentrated solutions by aggregation-caused quenching (ACQ) [8]. On the other hand, there are molecules that exhibit strong emission even in poor solvents or in the solid state. This property is referred to as aggregation-induced emission (AIE) and has attracted much attention in the field of fluorescence

Distinctive reactivity of N-benzylidene-[1,1'-biphenyl]-2-amines under photoredox conditions

• Shrikant D. Tambe,
• Kwan Hong Min,
• Naeem Iqbal and
• Eun Jin Cho

Beilstein J. Org. Chem. 2020, 16, 1335–1342, doi:10.3762/bjoc.16.114

• quenched by single-electron transfer from Cy2NMe, resulting in the generation of the highly reducing [IrII] species and the radical cation A. To validate the reductive quenching pathway, we carried out Stern−Volmer quenching experiments (Figure S1, Supporting Information File 1). The emission intensity of

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

• Shigeyuki Yamada,
• Takuya Higashida,
• Yizhou Wang,
• Masato Morita,
• Takuya Hosokai,
• Kaveendra Maduwantha,
• Kaveenga Rasika Koswattage and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

• intersystem crossing (ISC), resulting in the emission of phosphorescence [9]. Phosphorescent molecules generate two excitons (i.e., 25% S1 excitons and 75% T1 excitons) by application of an electric field, which is well known for organic light-emitting diodes. S1 excitons are converted to T1 excitons via an

• (e.g., Ru [14], Ir [15][16], Pt [17], and Au [18][19][20][21]) (Figure 1A), and this offers a molecular design approach for phosphorescence emission. However, it is becoming necessary to explore alternatives to rare metals because of the latter’s scarcity and toxicity. Owing to recent considerable

• of the toluene solutions (1.0 × 10−3 M) were acquired after bubbling with N2 or O2 gas for 30 min. In general, an O2-saturated environment strongly deactivates the triplet states; thus, PL emission stems only from fluorescence. On the other hand, elimination of O2 gas from a solution by bubbling with

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• ; quinazoline; Introduction Organic luminescent materials are extensively used in a wide range of optoelectronic devices. For the design of compounds, potentially exhibiting properties such as bipolar charge transport, delayed fluorescence or aggregation-induced emission enhancement (AIEE), a useful strategy

• properties [8]. A quinazoline-based emitter exhibiting thermally activated delayed fluorescence (TADF) was also reported [6] and green to yellow TADF OLEDs were fabricated with EQEs from 17.6 to 20.5%. The multicolor emission of a quinazoline–carbazole compound was employed in white OLEDs. White

• the derivatives 1–3 correlated with electrochemically estimated ones and with the ionization potential values discussed above. The photophysical characteristics determined from the UV–vis absorption and photoluminescence spectra are collected in Table 2. The emission spectra of diluted toluene

A smart deoxyribozyme-based fluorescent sensor for in vitro detection of androgen receptor mRNA

• Ekaterina A. Bryushkova,
• Erik R. Gandalipov and
• Julia V. Nuzhina

Beilstein J. Org. Chem. 2020, 16, 1135–1141, doi:10.3762/bjoc.16.100

• resulting from the 60-AR_RNA cleavage. Prediction of the RNA secondary structure with the folding energy before and after cleavage was performed by MFold open source [21]. The SDFS functional activity. A–C) Emission spectra of the assembled SDFS (green line), T1–T5 chains mix without annealing (green dotted

• line indicates the threshold fluorescence value of the buffer with malachite green dye and 60-AR_RNA. Emission spectra of SDFS activity on total cellular RNA. The green line represents a spectrum of SDFS incubated with total HDPC RNA. The black line is a spectrum of SDFS incubated with total HeLa cells

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

• spectroscopy, mass spectrometry, FTIR, thermogravimetric analysis, differential scanning calorimetry, cyclic voltammetry, and absorption and emission spectroscopy. Compounds 7a and 7b, both of which were amorphous solids, were stable up to 291 °C and 307 °C, respectively. Compounds 7a and 7b show three

• distinctive absorption bands: high and mid energy bands due to locally excited (LE) transitions and low energy bands due to intramolecular charge transfer (ICT) transitions. In dichloromethane solutions compounds 7a and 7b gave emission maxima at 561 nm and 482 nm with quantum efficiencies of 5.4% and 97.4

• yields (Scheme 1). Compounds 7a and 7b were fully characterised by NMR, FTIR, MS, elemental analysis, TGA, DSC, CV, and absorption and emission spectroscopy. The data are given in Supporting Information File 1. Thermal properties The thermal properties of compounds 7a and 7b were investigated by

Fluorinated phenylalanines: synthesis and pharmaceutical applications

• Laila F. Awad and
• Mohammed Salah Ayoup

Beilstein J. Org. Chem. 2020, 16, 1022–1050, doi:10.3762/bjoc.16.91

• -difluorophenylalanine derivatives 42a,b in quantitative yields [45] (Scheme 9). The radiolabeled 2-[18F]-fluoro-ʟ-phenylalanine 46 was synthesized as a promising radiopharmaceutical agent for molecular imaging by positron emission tomography (PET). The three-step synthesis of 46 started from [18F]-fluoride exchange in

• stability and substrate selectivity. 5.1. Applications of FPhe derivatives in positron emission tomography (PET) The molecular imaging technique positron emission tomography (PET) provides information on tumor metabolism, which allows for a more accurate diagnostic and therapy response in neuro-oncology

• . Synthetic protocols and strategies varied according to the position of the fluorine substituent. Also included were 18FPhe derivatives, some of which emerged as promising radiotracers in positron emission tomography (PET). Finally, it is notable that there are a significant number of FPhe derivatives which

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• to polarity and aggregation effects. Despite these observations, emission of compounds 3–6 can mainly be assigned to π–π* transitions of local excited states. However, a slight contribution of charge transfer (CT) can be also recognized in the emission of the studied compounds 3–6 (Figure 3a). The

• accompanied by intermolecular CT state relaxation. Such emission is evidenced by solvatochromic effects, i.e., a bathochromic shift of the emission peak due to the change of the environment to a more polar one. By replacement of the solvent toluene with THF, the solution of 4 exhibited a bathochromic shift of

• the PL peak from 407 to 425 nm. Thus, compound 4 clearly exhibited an intermolecular CT emission. In contrast, the PL peaks related to π–π* states of the solutions of the other studied compounds were only slightly affected by the solvent replacement. The different behavior of compound 4 may be

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• formation of the respective oxidation product caused the development of a broad absorption band between 425 nm and 500 nm and a new emission band at λfl = 628 nm, so that it may be employed as a selective chemosensor or chemodosimeter for the colorimetric and fluorimetric detection of Cu2+ and Fe3

• Information File 1). The compound 3a is essentially nonfluorescent in solution. The addition of 3.0 equiv of Cu2+, however, led to the development of a new, broad emission band at λfl = 628 nm (Φfl = 0.12 relative to rhodamine 6G [72], Figure 3B and Table 1). As supported by the corresponding excitation

• spectrum (Figure S1B, Supporting Information File 1), this emission most likely originated from the excitation of the new absorption band between 425 nm and 500 nm (Figure 3A) and can also be seen by the naked eye under UV light (Figure 4). It should be noted, however, that the excitation at lower

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• activation, and a double α-oxygenation. The latter reaction can be partly suppressed for the least reactive systems, providing access to α-unsubstituted boomerangs for the first time. These “α-free” systems are highly efficient fluorophores, with emission quantum yields exceeding 80% in toluene. Preliminary

• are about 1%. Interestingly, the fluorescence of cNMInH boomerang bipyrroles showed a stronger solvatochromic dependence than observed in their absorption spectra (Figure 2). In the more polar solvents, the emission profiles became significantly red shifted and broadened. At the same time, the

• measurements, without any significant loss of the unpolarized emission intensity. This behavior, which precluded a quantitative analysis of the CPL properties, may be attributed to a photoinduced racemization process. The differences in configurational stability of boomerangs are reproduced by DFT calculations

A method to determine the correct photocatalyst concentration for photooxidation reactions conducted in continuous flow reactors

• Clemens R. Horn and
• Sylvain Gremetz

Beilstein J. Org. Chem. 2020, 16, 871–879, doi:10.3762/bjoc.16.78

• can be delivered to the catalyst. These limitations are defined by the photoflow setup, specifically the channel height and the emission peak of the light source. This method was tested and shown to work well for three catalysts with different absorption properties through using LEDs with emission

• sources over mercury arcs and other light sources commonly used in industry and classical synthetic organic photochemistry. LEDs typically have much narrower emission spectra when compared to these light sources, all of which have broad emission spectra except for low-pressure sodium vapor lamps [15][16

• ]. These broad emission spectra pose some further complications as they are ultimately a rather inefficient way to use the energy and provide wavelengths that can effectively increase the risk of side reactions [17]. The fact that only a portion of the emitted light is used in the reaction can further

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• aldehyde catalyst to the haloalkanes. Using cutoff filters for certain wavelengths, the authors found that the near-UV part of the CFL emission was necessary for the excitation of 4-anisaldehyde (52) through a n→π* transition. No ground state association between the reaction components was detected

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

• 1.78 eV from the onset of its UV–vis absorption spectrum. Similar to the cyclopenta-fused pyrene derivatives [28][29], compound 1 does not show detectable fluorescence emission. Furthermore, the electrochemical properties of 1 was probed by cyclic voltammetry (CV) in DCM (Figure 3b). According to the

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

•  1). This is seen between the associative interactions (a) and (b) with a centroid-to-plane distance 2.031(9) Å and a shift distance of 4.294(5) Å and interactions (c) and (d) with a centroid-to-plane distance 3.418(11) Å and a shift distance of 2.446(14) Å. Absorption and steady-state emission

• dimers and 8 nm (1.25 × 106 cm−1) for the monomer. The difference in properties of the unsymmetric zinc-nickel dimer 16 is observed significantly more in the corresponding fluorescence emission spectrum (Figure 7). The emission observed for the zinc monomer and dimer, 14 and 9, respectively, was

• nickel porphyrin is acting as the acceptor. An electron/energy transfer is occurring between the two porphyrins, therefore, when the molecule is excited at the wavelength of the zinc porphyrin, the fluorescence emission ordinarily observed for the zinc porphyrin does not occur as the energy has been

Synthesis of C₇₀-fragment buckybowls bearing alkoxy substituents

• Yumi Yakiyama,
• Shota Hishikawa and
• Hidehiro Sakurai

Beilstein J. Org. Chem. 2020, 16, 681–690, doi:10.3762/bjoc.16.66

• hydrogen bonds (C37∙∙∙O1, C11∙∙∙O2, C40∙∙∙O4) (Figure 5c). Photophysical properties of the dialkoxides were investigated by UV–vis and emission spectroscopies (Figure 6). UV–vis spectra of 5a and 5b well reflected the electric property of 1, showing two strong bands observed at around 280–300 nm and 330

• –350 nm, and a broad one at around 350–480 nm, which was attributable to the indenopyrene moiety of 1 (Figure 6a) [18]. Meanwhile, 5a and 5b showed emission bands at 564 nm and 566 nm, respectively, which were red shifted around 50 nm from that of 1, clearly indicating the effect of the introduction of

• dialkoxides (Figure 6b). In contrast, 5c exhibited different features in both UV–vis and emission spectra from the other two. In the UV–vis spectrum of 5c, the splitted sharp absorptions at 266 and 287 nm and a broad band at 320 nm together with a relatively strong broad band at 409 nm are visible. The

Design and synthesis of diazine-based panobinostat analogues for HDAC8 inhibition

• Sivaraman Balasubramaniam,
• Sajith Vijayan,
• Liam V. Goldman,
• Xavier A. May,
• Kyra Dodson,
• Sweta Adhikari,
• Fatima Rivas,
• Davita L. Watkins and
• Shana V. Stoddard

Beilstein J. Org. Chem. 2020, 16, 628–637, doi:10.3762/bjoc.16.59

• the positive control consisted of HDAC8 without inhibitor added. The substrate concentration was 5 µM, and HDAC8 concentration per well was 4 ng/µL. The reaction was initiated by addition of enzyme. The fluorogenic substrate was excited at 360 nm and the emission signal was detected at 460 nm using a

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

• , while the emission quantum yields of the β-ethynylated derivatives are significantly lower than those of α-ethynylated ones. The current method should be useful for fine-tuning of the photophysical properties of BODIPY dyes as well as for constructing BODIPY-based building cores for functional π

• optical features such as intense and narrow S0–S1 absorption and emission bands in the visible-to-near-infrared region, a high fluorescence quantum yield, and good photostability. For the applications mentioned above, various BODIPY dyes functionalized at the meso-, α-, and β-pyrrolic positions have been

• molar absorption coefficients (ε) of the S0–S1 bands of the α-ethynyl-substituted BODIPYs are substantially enhanced as the number of substituted groups increases (Figure 4a). Along with the absorption spectral profiles of 3a and 4a, sharp emission bands emerge with mirror structures (Figure 5a). The

Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)

• Anping Luo,
• Min Zhang,
• Zhangyi Fu,
• Jingbo Lan,
• Di Wu and
• Jingsong You

Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49

• , which corresponds to π−π* electron transition (Figure 1a and Table S2, Supporting Information File 1). The measurement of emission spectra demonstrates that 4k and 4n emit violet fluorescence with emission maxima at 395 nm and 390 nm, respectively, while 4o exhibits a sky-blue emission with an emission

• development of diverse organic photoelectrical materials. a) UV-visible absorption spectra of 4k, 4n and 4o in toluene (1 × 10−5 mol/L). b) Emission spectra of 4k, 4n and 4o in toluene (1 × 10−5 mol/L). Direct C–H arylation of PAHs. Scope of aryliodonium salts. Reaction conditions: 1a (0.2 mmol), 2 (0.3 mmol

Synthesis of triphenylene-fused phosphole oxides via C–H functionalizations

• Md. Shafiqur Rahman and
• Naohiko Yoshikai

Beilstein J. Org. Chem. 2020, 16, 524–529, doi:10.3762/bjoc.16.48

• via 1,4-cobalt migration. The resulting 7-hydroxybenzo[b]phosphole derivative was used for further π-extension through Suzuki–Miyaura couplings and a Scholl reaction, the latter closing the triphenylene ring. The absorption and emission spectra of the thus-synthesized compounds illustrated their

• phosphole oxides, which are distinct from Saito’s compounds [15] as well as from other reported examples [26][27][28] in terms of the mode of fusion of the phosphole and triphenylene units. The present phosphole/triphenylene hybrid molecules displayed absorption and emission profiles that reflected the

• successful synthesis of the triphenylene-fused phosphole oxides 8, we studied the absorption and emission properties of these compounds in CH2Cl2 solution. Figure 3 shows the absorption and emission spectra of compounds 8a–c, and Table 1 provides a summary of these spectra and reported spectral data of