Thiophene/selenophene-based S-shaped double helicenes: regioselective synthesis and structures

• Mengjie Wang,
• Lanping Dang,
• Wan Xu,
• Zhiying Ma,
• Liuliu Shao,
• Guangxia Wang,
• Chunli Li and
• Hua Wang

Beilstein J. Org. Chem. 2022, 18, 809–817, doi:10.3762/bjoc.18.81

• obviously differ because of changes in their molecular configuration and equal to 2.86, 3.15, and 3.81 eV, respectively [27][28]. As the number of selenium atoms increases from DH-1 to DH-3, the fluorescence intensity (Figure S19 in Supporting Information File 1) and the fluorescence quantum yield (ΦF

• solutions of DH-1 and DH-2 in CHCl3/CH3OH 5:1 (v/v) were employed for growing single crystals. The fluorescence quantum yields (ΦF) of DH-1–3 are characterized in dichloromethane with quinine sulfate in 0.1 N H2SO4 as the control. Synthesis of 5a–c and DH-1–3 Synthesis of 1,3-bis(2-(5-(trimethylsilyl

Mechanochemical halogenation of unsymmetrically substituted azobenzenes

• Dajana Barišić,
• Mario Pajić,
• Ivan Halasz,
• Darko Babić and
• Manda Ćurić

Beilstein J. Org. Chem. 2022, 18, 680–687, doi:10.3762/bjoc.18.69

• of L8, fluorescence prevented a more detailed insight into this reaction. The monitoring results confirmed the complete conversion of azobenzenes L6 and L7 to their monopalladated products after about one hour of milling, as well as a reaction course similar to that of the analogous reaction of L1

• (15 μL), and SiO2 (250 mg). b) Two-dimensional (2D) plot of the time-resolved Raman monitoring of LAG of L6 (0.40 mmol) with Pd(OAc)2 (0.42 mmol), TsOH (0.42 mmol), MeCN (0.48 mmol, 25 µL), and SiO2 (250 mg). Only Raman spectra before fluorescence are shown in both parts. Halogenation of azobenzenes

Heteroleptic metallosupramolecular aggregates/complexation for supramolecular catalysis

• Prodip Howlader and
• Michael Schmittel

Beilstein J. Org. Chem. 2022, 18, 597–630, doi:10.3762/bjoc.18.62

• be performed. Supramolecular systems based on non-covalent interactions have drawn considerable attention in assembling efficient light harvesting systems (LHSs) in the last decade [60][61]. Significant attention has been centered to construct artificial LHSs via FRET (fluorescence resonance energy

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• photophysically and computationally. The photophysical studies revealed that all the synthesized compounds exhibited fluorescence in organic solvents, while N-methyl-4-((pyridin-2-yl)amino)-substituted maleimide derivatives 4a–e, which are based on an acceptor–donor–acceptor (A–D–A) system, exhibited aggregation

• -induced emission enhancement (AIEE) properties in aqueous media. Compounds 4a and 4e, bearing electron-withdrawing groups (Br and CF3, respectively) showed 7.0 and 15 times fluorescence enhancement. Time-dependent density functional theory (TD-DFT) calculations were performed to gain better insight into

• materials because of their applications in areas such as information devices, displays, and clinical diagnosis [1][2][3]. Organic compounds with planar structures and large π systems exhibit strong fluorescence in dilute solutions [4][5]. However, these compounds usually form aggregate structures in high

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• molecule overexpressed in cancer cells, through host–guest competitive substitution since TBTQ-CB6 has a stronger binding affinity toward SM than MV and DOX. The host–guest interactions of the complexes of TBTQ-CB6 with MV, DOX and SM were investigated by NMR spectroscopy and fluorescence spectroscopy. The

• competitive guest to control the release of MV and DOX. The structures of the target molecule TBTQ-CB6 and its precursors were characterized by NMR spectroscopy and mass spectrometry. The host–guest chemistry of TBTQ-CB6MV, TBTQ-CB6DOX and TBTQ-CB6SM was investigated by NMR spectroscopy and fluorescence

• fluorescence spectroscopy (Figure S10 in Supporting Information File 1). The corresponding Job plot curve (Figure 1b) showed the maximum value at a molar fraction of 0.5 for MV, indicating that TBTQ-CB6 encapsulated MV in a 1:1 stoichiometry. To further evaluate the association affinity of TBTQ-CB6 and MV

Chemistry of polyhalogenated nitrobutadienes, 17: Efficient synthesis of persubstituted chloroquinolinyl-1H-pyrazoles and evaluation of their antimalarial, anti-SARS-CoV-2, antibacterial, and cytotoxic activities

• Viktor A. Zapol’skii,
• Isabell Berneburg,
• Ursula Bilitewski,
• Melissa Dillenberger,
• Katja Becker,
• Stefan Jungwirth,
• Aditya Shekhar,
• Bastian Krueger and
• Dieter E. Kaufmann

Beilstein J. Org. Chem. 2022, 18, 524–532, doi:10.3762/bjoc.18.54

• of the malaria parasite P. falciparum (3D7 strain) using the SYBR Green I-based fluorescence assay [35]. Table 1 summarizes the activity of the compounds against the red blood cell stages of P. falciparum with EC50 values ranging from high nanomolar (200 nM) to low micromolar concentrations (4 µM

BINOL as a chiral element in mechanically interlocked molecules

• Matthias Krajnc and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2022, 18, 508–523, doi:10.3762/bjoc.18.53

• ) and two NH donors (on the macrocycle). For the anion-recognition experiments, the binding of selected dicarboxylate anions ((S/R)-glutamate, fumarate, and maleate) was investigated by fluorescence titrations. This revealed an impressive chiral discrimination towards (S)-Glu2− with a selectivity of K(S

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• .18.52 Abstract The interest in organic materials exhibiting thermally activated delayed fluorescence (TADF) significantly increased in recent years owing to their potential application as emitters in highly efficient organic light emitting diodes (OLEDs). Simple modification of the molecular structure

• attached through a phenylene bridge. A modification of the pyrimidine unit with CN, SCH3, and SO2CH3 functional groups at position 2 is shown to enhance the emission yield up to 0.5 with pronounced TADF activity. Keywords: carbazole; pyrimidine; RTP; synthesis; thermally activated delayed fluorescence

• ; Introduction The first reports on highly efficient thermally activated delayed fluorescence (TADF) mechanism and its successful realization in organic light emitting diodes (OLEDs) by Adachi and co-workers [1][2] have drawn the attention to the design and synthesis of various emissive donor–acceptor organic

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• of Chemistry, Silesian University of Technology, Strzody 9, 44-100 Gliwice, Poland Department of Energy Conversion and Storage, Technical University of Denmark, Anker Engelunds Vej 301, 2800 Kongens Lyngby, Denmark 10.3762/bjoc.18.48 Abstract A new thermally activated delayed fluorescence (TADF

• thermally activated delayed fluorescent behavior. Keywords: charge-transfer; dibenzophenazine; donor–acceptor; organic light-emitting diodes; thermally activated delayed fluorescence; Introduction Thermally activated delayed fluorescence (TADF), which was firstly reported in 1961 by Parker and Hatchard [1

• ], is a fundamental photophysical phenomenon that refers to delayed fluorescence radiated from the singlet excited state (S1) as a consequence of a brief detour to a triplet excited state (Tn) [i.e., intersystem crossing (ISC) and reverse intersystem crossing (rISC)]. Since the revisit of TADF in

Tetraphenylethylene-embedded pillar[5]arene-based orthogonal self-assembly for efficient photocatalysis in water

• Zhihang Bai,
• Krishnasamy Velmurugan,
• Xueqi Tian,
• Minzan Zuo,
• Kaiya Wang and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2022, 18, 429–437, doi:10.3762/bjoc.18.45

• –guest interactions between m-TPEWP5 and G, fluorescence titration studies were carried out in aqueous solution. As shown in Figure 2a, the free host m-TPEWP5 showed a maximum emission at 465 nm. Upon gradually increasing the concentration of G (0 to 1 equiv) into m-TPEWP5, the fluorescence intensities

• enhanced AIE effect [33][34]. To examine the binding stoichiometric ratio of the host–guest complex, Job’s plot [35] method was employed by using fluorescence titration experiments. As shown in Figure S3 (see Supporting Information File 1), the maximum mole fraction was observed at 0.5 (Figure 2b), which

• , respectively. Initially, we compared the overlapping efficiencies of both donor and acceptor systems by using UV–vis and fluorescence spectroscopy. The absorption band of the EsY acceptor shows good overlapping with the emission band of m-TPEWP5G donor (Figure 4a). We therefore speculated, that there may be an

Four bioactive new steroids from the soft coral Lobophytum pauciflorum collected in South China Sea

• Di Zhang,
• Zhe Wang,
• Xiao Han,
• Xiao-Lei Li,
• Zhong-Yu Lu,
• Bei-Bei Dou,
• Wen-Ze Zhang,
• Xu-Li Tang,
• Ping-Lin Li and
• Guo-Qiang Li

Beilstein J. Org. Chem. 2022, 18, 374–380, doi:10.3762/bjoc.18.42

• (Sigma-Aldrich, St. Louis, MO, USA) was added to the drug groups and incubated for 1 h after treatment with different compounds for 2 h. All treatments were performed in triplicate. Each zebrafish larva was photographed by a fluorescence microscope (AXIO, Zoom. V16), and the number of macrophages was

Anomeric 1,2,3-triazole-linked sialic acid derivatives show selective inhibition towards a bacterial neuraminidase over a trypanosome trans-sialidase

• Peterson de Andrade,
• Sanaz Ahmadipour and
• Robert A. Field

Beilstein J. Org. Chem. 2022, 18, 208–216, doi:10.3762/bjoc.18.24

• and 4.79 ppm in 1H NMR, respectively. High-resolution mass spectra were acquired using electrospray ionisation in a Waters Vion spectrometer with Waters Acquity LC–MS (positive mode). Fluorescence measurements were performed on a FLUOstar Omega Multi-Mode Microplate Reader. Expression and purification

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

• Ruan Carlos B. Ribeiro,
• Patricia G. Ferreira,
• Amanda de A. Borges,
• Luana da S. M. Forezi,
• Fernando de Carvalho da Silva and
• Vitor F. Ferreira

Beilstein J. Org. Chem. 2022, 18, 53–69, doi:10.3762/bjoc.18.5

• exhibiting solid-state fluorescence, although the fluorescence partially disappears in solution, and there is a large shift to red and blue [98][99]. Carbon–carbon bond formation The main steps in a synthesis usually involve C–C bond formation, which is usually the main reaction step, or functional group

• was produced in an 85% yield [104][105]. Then, Ooyama and co-workers [99] transformed the 1,2-dicarbonyl group into the fused imidazo[4,5-a] heterocycle via a reaction of 56b with 4-cyanobenzaldehyde and an NH3 source in a 75% yield. The crystal of 57 exhibits a sensitive color change and fluorescence

Peptide stapling by late-stage Suzuki–Miyaura cross-coupling

• Hendrik Gruß,
• Rebecca C. Feiner,
• Ridhiwan Mseya,
• David C. Schröder,
• Michał Jewgiński,
• Kristian M. Müller,
• Rafał Latajka,
• Antoine Marion and
• Norbert Sewald

Beilstein J. Org. Chem. 2022, 18, 1–12, doi:10.3762/bjoc.18.1

• 9% for aAxWt, 15% for P5.1, and 21% for P5.2 (see Supporting Information File 1). Biological evaluation Competitive fluorescence polarisation (FP) assays were performed to evaluate whether the increased helicity of peptide P5 also results in an increased binding affinity to its native binding

• partner β-catenin. The N-terminal FITC-labelled RCM-stapled peptide fStAx-3 was synthesised as tracer for this study and its dissociation constant was determined to be 63 ± 6 nM in a direct fluorescence polarisation assay, which is in agreement with previously reported data [77]. Noteworthy, the isomer

• water. In vitro binding affinities to β-catenin determined by competitive fluorescence polarisation assays. Cleavage sites of Proteinase K digestion indicated by a red arrow. Principal component analysis (PCA) of the macrocycle’s non-hydrogen atoms in the two isomers of P5. The upper panel depicts the

Effect of a twin-emitter design strategy on a previously reported thermally activated delayed fluorescence organic light-emitting diode

• Ettore Crovini,
• Zhen Zhang,
• Yu Kusakabe,
• Yongxia Ren,
• Yoshimasa Wada,
• Bilal A. Naqvi,
• Prakhar Sahay,
• Tomas Matulaitis,
• Stefan Diesing,
• Ifor D. W. Samuel,
• Wolfgang Brütting,
• Katsuaki Suzuki,
• Hironori Kaji,
• Stefan Bräse and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 2894–2905, doi:10.3762/bjoc.17.197

• %, with Commission Internationale de l’Éclairage coordinate of (0.22, 0.47), at 1 mA cm−2. Keywords: blue emitters; dimer; indolocarbazole; orientation; outcoupling effect; solution-processed OLEDs; TADF emitters; triazine; Introduction Organic thermally activated delayed fluorescence (TADF) materials

• present high photoluminescence quantum yields, ΦPL, of 75.2% and 71.9%, respectively, and delayed fluorescence lifetimes, τd, of 25.48 μs and 34.31 μs, respectively. The devices produced with these materials reached maximum external quantum efficiencies (EQEmax) values of 14.5% and 30% at low brightness

• degassed toluene show mono-exponential prompt and delayed fluorescence decays at 8.94 ns and 28.83 µs, respectively (Supporting Information File 1, Figure S4c,d). After exposure to oxygen, the delayed fluorescence disappears while the prompt decay lifetime, τp, is slightly reduced to 6.80 ns, implying the

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• produced the desired amidobenzene-containing hemicucurbituril. As an original fluorescent chemosensor, it exhibited strong interactions with Fe3+ over other metal cations. The experimental evidence of fluorescence spectra suggested that a 1:1 complex was formed between this macrocycle and Fe3+ with an

• association constant up to (2.1 ± 0.3) × 104 M−1. Meanwhile, this macrocycle showed no obvious or only slight enhancement of the fluorescence intensity with selected anions. Keywords: amidobenzene-containing macrocycle; hemicucurbituril; host–guest interaction; macrocycle; modification; Introduction

• ions at submicromolar concentrations always by means of NMR spectroscopy [33]. Nevertheless, sensing by UV–vis or fluorescence spectra was hard to realize, for there is no chromophore in the frameworks. While hemicucurbit[n]urils with improvement in solubility, they still remain poor in derivatization

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• , 4-NO2C6H4, and 2-furyl, and R1-substituents are 5-NEt2, 5-OCH3, 4-Br, and 4-NO2. Complementarily, the Schiff bases showed low to good quantum fluorescence yield values in CHCl3 (Φf = 0.12–0.80), DMSO (Φf = 0.20–0.75) and MeOH (Φf = 0.13–0.85). Higher values of Stokes shifts (SS) were observed in

• coefficients of the derivatives studied here. All absorption spectra are listed in Supporting Information File 1 (Figures S2–S7). The steady-state fluorescence emission spectra of the Schiff base compounds from their absorption in the UV–vis region was carried out. Derivatives 3aa–fa and 3bb–be were analyzed

• in CHCl3, DMSO, and MeOH solutions by the emission and excitation spectra and exemplified in the Supporting Information File 1 (Figures S2–S7). For emission measurements, the maximum wavelength with the lowest absorption energy was used for excitation for the fluorescence measurements. The quantum

The ethoxycarbonyl group as both activating and protective group in N-acyl-Pictet–Spengler reactions using methoxystyrenes. A short approach to racemic 1-benzyltetrahydroisoquinoline alkaloids

• Marco Keller,
• Karl Sauvageot-Witzku,
• Franz Geisslinger,
• Nicole Urban,
• Michael Schaefer,
• Karin Bartel and
• Franz Bracher

Beilstein J. Org. Chem. 2021, 17, 2716–2725, doi:10.3762/bjoc.17.183

• compounds 2a–f, 3a–c and 4 regarding their P-glycoprotein blocking potential. For that, we used the P-glycoprotein substrate calcein as reporter dye and analyzed intracellular calcein fluorescence of P-glycoprotein overexpressing VCR-R CEM cells by flow cytometry. An increase of the calcein-positive

• adjusted to pH 9 with NaOH or neutral as mobile phase. Details of the syntheses and spectroscopic data are presented in Supporting Information File 1. Fluorometric Ca2+ measurements Concentration–response curves of 1-benzyltetrahydroisoquinolines were generated by using a custom-made fluorescence imaging

• . After recording a baseline for 60 s, serially prediluted compounds were added with a 384-tip multichannel arm (MCA384, Tecan) at the indicated concentrations and incubated for 5 min. In a second step, all 384 wells were stimulated with 10 µM TPC2-A1-N or 30 µM TPC2-A1-P. Finally, fluorescence

Exfoliated black phosphorous-mediated CuAAC chemistry for organic and macromolecular synthesis under white LED and near-IR irradiation

• Azra Kocaarslan,
• Zafer Eroglu,
• Önder Metin and
• Yusuf Yagci

Beilstein J. Org. Chem. 2021, 17, 2477–2487, doi:10.3762/bjoc.17.164

• polymer has similar absorption characteristic to bare anthracene (Figure 4b). The fluorescence spectrum of diluted solution of PCL-Anth in THF excited at λexc = 350 nm showed the characteristic emission bands of the excited (singlet) anthracene at 595, 655, and 725 nm (Figure 4c). These observations

• acetylene proton around 4.42 ppm. a) 1H NMR spectrum of chain end modified PCL-Anth; b) UV–vis spectra of (azidomethyl)anthracene (black) and PCL-Anth (red); c) fluorescence emission spectrum of PCL-Anth. a) GPC traces of PS-Az, PCL-Alk and block copolymer (Ps-b-PCL) b) 1H NMR spectrum of the block

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• /bjoc.17.162 Abstract A facile synthesis of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridine derivatives is reported which is based on POCl3-mediated cyclodehydration followed by double Suzuki–Miyaura cross-coupling. The absorption and fluorescence properties of the obtained products were investigated and

• their HOMO/LUMO energy levels were estimated by cyclic voltammetry measurements. Besides, density functional theory calculations were carried out for further exploration of their electronic properties. Keywords: catalysis; cross-coupling; cyclization; fluorescence; palladium; Introduction π-Conjugated

• absorption spectra were measured in diluted dichloromethane solutions (c = 1 × 10−5 M) at room temperature. Table 2 summarizes the obtained spectral data, fluorescence quantum yields, stokes shifts, and optical band gap energies. As shown in Figure 2, most of the compounds show a broad band at around 320–360

Post-functionalization of drug-loaded nanoparticles prepared by polymerization-induced self-assembly (PISA) with mitochondria targeting ligands

• Janina-Miriam Noy,
• Fan Chen and
• Martina Stenzel

Beilstein J. Org. Chem. 2021, 17, 2302–2314, doi:10.3762/bjoc.17.148

• incubation, the penetration profiles of the micelles into the spheroids can be visualized as seen in Figure 3. The PEG-based micelle, PPM-NP4-TPP, reveals no significant change in fluorescence compared to the non TPP-conjugated micelle, PPM-NP4 (green and red curves respectively, Figure 3A II and B II)). No

• dominant improvement in spheroid penetration could therefore be detected. Interestingly, for MPM-NP2-TPP significant higher fluorescence intensities were measured, when the TPP-micelle was subjected to 143B and SW982 MCTS (Figure 3). As a result, high spheroid uptake and deep spheroid penetration were

• MPM-NP2-TPP are overlapping. Representative 31P NMR (top) and 1H NMR (bottom) spectrum of PP3-TPP conjugation product in D2O. Penetration of PPM-NP4-TPP and MPM-NP2-TPP micelles and fluorescence intensity profile on (A I, II) 143B and (B I, II) SW982 spheroids (scale bars = 300 µm). The results of the

(Phenylamino)pyrimidine-1,2,3-triazole derivatives as analogs of imatinib: searching for novel compounds against chronic myeloid leukemia

• Luiz Claudio Ferreira Pimentel,
• Lucas Villas Boas Hoelz,
• Henayle Fernandes Canzian,
• Frederico Silva Castelo Branco,
• Andressa Paula de Oliveira,
• Vinicius Rangel Campos,
• Floriano Paes Silva Júnior,
• Rafael Ferreira Dantas,
• Jackson Antônio Lamounier Camargos Resende,
• Anna Claudia Cunha,
• Nubia Boechat and
• Mônica Macedo Bastos

Beilstein J. Org. Chem. 2021, 17, 2260–2269, doi:10.3762/bjoc.17.144

• dissolved in DMSO (Sigma-Aldrich) were added and further incubated for 47 hours. After this period, resazurin was added at a final concentration per well of 0.01 mg/mL, and the first fluorescence reading was immediately performed (λex = 560 nm; λex = 590 nm) (time zero) using FlexStation 3 microplates

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

• region. Also, the protonated polymer 61 showed strong fluorescence at 480 nm with a large Stokes shift of 155 nm. In 2015, Zhang, Liu, and co-workers [36] reported the synthesis of conjugated donor–acceptor (D–A)-type azulene-dithienyldiketopyrrolopyrrole (DPP) polymers 69, 71, and 72. The synthesis of

• displayed fluorescence emission at 385 nm in the protonated state. The electrochemical bandgap of these polymers was in the impressive range of 1.57–1.62 eV. In 2014, Hawker, Robb, and co-workers [35] also reported the synthesis of azulene-fluorene copolymers 117–121, containing varying ratios of 1,3-and

• the substitution pattern of the azulene units on this behavior. The polymer containing entirely 1,3-substituted azulene, 117, exhibited a strong fluorescence at 420 nm in the protonated state and the attenuation of the fluorescence signals took place with the increasing population of 4,7-disubstitued

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• triplex, most likely due to reduced ability of R to π-stack [103]. As expected, fluorescence microscopy showed improved cellular uptake of the cationic guanidinium-modified PNAs [103]. PNA nucleobases for Hoogsteen recognition of adenine: Because the T•A–T triplets are reasonably stable under

• ]. Melting of a duplex formed by 2-aminopurine-modified PNA and complementary DNA increased the fluorescence signal, which had likely been quenched by adjacent nucleobases in the duplex [142]. Interestingly, quenching was also observed in a single stranded PNA alone, which diminished the applicability of 2

• emission intensity (dependent on the sequence context) upon hybridization with complementary DNA and RNA [145]. Another analogue, 5,6-BenzopC (Figure 10) had high quantum yield and superior base pairing properties, but its fluorescence was completely quenched upon hybridization with DNA and RNA [146