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

• dilute solutions (10−4–10−5 mol/L) of the compounds were recorded at room (295 K) and low (77 K) temperatures with a luminescence spectrometer Edinburgh Instruments FLS980. Photoluminescence quantum yields (PLQY) of the solutions and thin films of the materials were measured using an integrating sphere

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

• explained by the dihedral angle between the acridanyl and naphthyl moieties, that is the largest one among all the studied compounds, leading to a reduction of π-conjugation. This observation explains the distinct ICT character of the luminescence of compound 4. The dihedral angles in the molecules of 3 and

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

• we report that the above Pd-mediated chemistry is capable of producing highly twisted dilactam boomerangs and provide first examples of α-free boomerang systems. These new derivatives are of interest as emitters for both polarized and unpolarized luminescence. Results and Discussion Synthesis The

• polarized luminescence (CPL) measurements performed for enantioenriched samples of cNMI3H reveled weak signals of opposite signs, with a maximum at ca. 570 nm consistent with the unpolarized luminescence of this system (Supporting Information File 1, Figure S6). The CPL signals rapidly decayed during the

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• , copper-based photocatalysts are often considered less efficient due to a lower luminescence lifetime compared to Ir and Ru complexes [6]. Review In this review, we summarized the recent significant advances that were made in the use of copper-based photocatalysts for synthetically useful transformations

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• characteristics in the solid state. The crystal structures of the coupling products were also evaluated by single crystal X-ray analysis and the well-ordered intermolecular stacking arrangements appeared to be responsible for the enhanced CPL. Keywords: BINOL; C–H activation; circularly polarized luminescence

• fluorophore unit in certain light-emitting functional materials (Scheme 1) [14]. Meanwhile, organic optoelectronic materials with circularly polarized luminescence (CPL) characteristics have attracted significant research interests in recent years [18][19][20][21] for their potential applications in three

• fluorescence emission bands, whereas the (R)-isomers emitted right-handed CPL to produce the mirror images. The calculated luminescence dissymmetry factors [48] glum for the solutions were all within the range of 3.80 × 10−4 to 6.90 × 10−4. On the other hand, in the dispersed solid state in Fomblin® PFPE

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• measurements using a combination of TCSPC and MCS techniques (at λPL = 550 nm) revealed two emission decay lifetimes: a prompt component, τp, of 19.4 ns and a very long delayed component, τd, of 352 μs. The two timescales of luminescence are a hallmark of delayed fluorescence behavior (Figure 6). The PL

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• luminescence characteristics (Table 5, entries 2, 4, 6 and 7). The Stokes shifts fall in a range between 5000 and 6100 cm−1 and the fluorescence quantum yields of the 1H-pyridines 5 account between 1 and 3%. Besides solution fluorescence all 1H-pyridines 5 also luminesce in the solid state (Figure 3, bottom

• (solid lines) and emission (dashed lines) spectra of 1H-pyridines 8a and 8b (recorded in dichloromethane at T = 298 K). Solid-state luminescence of 1H-pyridines 5a, 8a and 8b (λexc = 365 nm). α-Pyrones 6 as solids under daylight (top), selected derivatives under UV light (λexc = 365 nm, c(6) = 10−4 M) in

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• lanthanides used. The main application foreseen for these nanomaterials is as a substitute of quantum dots [3], since the combination of anti-Stokes emission and noncoherent absorption prevent any luminescence background. Their extreme photostability [4] make them also ideal candidates for single particle

• (Jasco, Hamamatsu). A more sophisticated approach involves microscopic techniques, enabling one to determine UCQY even at the single NP scale. A seminal report was published in 2013 by Nadort et al. [20] describing the measurement of the luminescence of Er-doped UCNPs at the single NP or cluster level

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• – Istituto Nazionale di Ottica, Largo Enrico Fermi 6, 50125 Firenze, Italy 10.3762/bjoc.15.236 Abstract In this work we apply a combination of steady state and time resolved luminescence and absorption spectroscopies to investigate the excited-state dynamics of a recently developed molecular photoswitch

• isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main

• the fluorescence band and the emission quantum yield depend on the solvent, with the emission strongly quenched in protic media [29]. Time-resolved fluorescence Detailed analysis of the fluorescence features of the two forms in toluene has been performed by time-resolved luminescence measurements in

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• the mechanism of action of anticancer compounds, and for safer photodynamic therapy. Keywords: bioimaging; dendrimer; fluorescence; phosphorus; two-photon absorption; Introduction Natural luminescence phenomena such as the bioluminescence of fireflies or of certain marine microorganisms, or the

• phosphorescence of certain minerals after being exposed to sun light, have fascinated Men for a long time. An important part of luminescence phenomena is due to the influence of light (generally visible or ultra-violet light) on matter, such as for instance a molecule, which can emit light at a wavelength

• classical fluorophores in their structure, have been already synthesized [13]. Besides, some types of dendrimers have shown non-traditional intrinsic luminescence, i.e., luminescence in the absence of known fluorophores [14]. Dendrimers functionalized with fluorophores having two-photon absorption

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• crystals are inherently capable of photo-reversible luminescence switching because the electronic structures of photochromic molecules reversibly change upon photoisomerization [13][14]. However, such a fluorescent system in condensed phase emits fluorescence often absorbed in adjacent molecules, therefore

• because the proton transfer occurs through an intramolecular hydrogen bond. This is also an origin of a large Stokes shift (8,000–11,000 cm−1) in the emission from the ESIPT state. Consequently, yellow luminescence was observed by UV-excitation [17][18]. Mutai et al. reported an ESIPT luminescence of an

• (phenylethynyl)anthracene in hexane (Φf = 1.0) [31]. The luminescence quantum yields of crystalline solids were measured using a JASCO ILF-533 integral sphere attached to a JASCO FP-6600 spectrofluorophotometer. The mixture of microcrystalline compounds (2 mg) and powdered sodium chloride (1 g) were put into a 5

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• luminescent dye by a suitable receptor leads to a readily detectable change of its luminescence property, prominently its intensity. An analyte then displaces the luminescent dye from the complex, resulting in a detectable luminescence response converting a receptor–analyte binding event into an easily

• course of an enzymatic reaction. Thus, the progress of the reaction can be signaled by a luminescence increase or decrease with time, which enables a highly sensitive real-time luminescence monitoring of the enzymatic activity [6]. STA has been applied to screening enzyme inhibitors or activators

• binding of the analyte gives rise to an extraordinary luminescence response of the reporter dye. Macrocyclic hosts constitute a family of well-studied artificial receptors with a discrete cavity that is selective for complementary binding to certain guests [9]. Modulation of properties of organic

Selective detection of DABCO using a supramolecular interconversion as fluorescence reporter

• Indrajit Paul,
• Debabrata Samanta,
• Sudhakar Gaikwad and
• Michael Schmittel

Beilstein J. Org. Chem. 2019, 15, 1371–1378, doi:10.3762/bjoc.15.137

• to the fact, that the interconversion is accompanied by a diagnostic change in the fluorescence spectra, the present system represents a supramolecular reporter for the selective detection of DABCO. It is thus a rare example of DABCO sensing by luminescence [41]. Molecular structures of ligands 1, 2

A convenient and practical synthesis of β-diketones bearing linear perfluorinated alkyl groups and a 2-thienyl moiety

• Ilya V. Taydakov,
• Yuliya M. Kreshchenova and
• Ekaterina P. Dolotova

Beilstein J. Org. Chem. 2018, 14, 3106–3111, doi:10.3762/bjoc.14.290

• ]. Diketones bearing perfluorinated radicals are very important for the design of highly effective luminescent materials based on lanthanide coordination compounds. Substitution of aliphatic radicals by perfluorinated ones in the molecules of ligands led to a significant increase in luminescence intensity due

• MS measurements was provided by the Russian Foundation for Basic Research (grants No. 18-29-04029 and 18-02-00653). IVT is also grateful to Volkswagenstiftung (Project «Multifunctional molecular materials – bridging magnetism and luminescence»). The authors are thankful to Dr. Yu. Belousov (LPI) for

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• by thermal activation. Thus, the excited states can be thermally upconverted to the singlet state by reverse intersystem crossing (RISC), giving rise to a luminescence process arising from the singlet state (fluorescence). The concept of delayed fluorescence is based on the unusual and transient

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• identify an expanded range of synthetic ligands for SdiA. Herein, we report the screening of a focused library of AHL analogs for activity in the SdiA receptor from S. Typhimurium. Compound efficacies and potencies were measured in agonism and antagonism assays using an SdiA luminescence reporter system

• the positive control based on raw luminescence. Further, for the E. coli JLD271 reporter, the negative control was at 50% the level of the positive control; we reason that this higher background relative to S. Typhimurium is due to the overexpression of SdiA in this reporter. Conditions for both

• changing the expression of SdiA or by inhibiting the luminescence reporter. Conversely, the inability of F45 and 16 to even partially inhibit SdiA in the E. coli reporter system indicates that the means by which they inhibit SdiA activity in the S. Typhimurium reporter is dependent on either the expression

Synthesis of aryl sulfides via radical–radical cross coupling of electron-rich arenes using visible light photoredox catalysis

• Amrita Das,
• Mitasree Maity,
• Simon Malcherek,
• Burkhard König and
• Julia Rehbein

Beilstein J. Org. Chem. 2018, 14, 2520–2528, doi:10.3762/bjoc.14.228

• showed that an aryl disulfide could be cleaved by irradiation with visible light [49]. Some spectroscopic investigations (Figure 3) gave valuable information about the mechanism of the photoredox catalytic cycle. The luminescence intensity of [Ir(dF(CF3)ppy)2(dtbpy)]PF6 was quenched upon successive

• addition of 1,2,4-trimethoxybenzene (oxidation potential 1.02 V vs SCE, Figure 3a). The values are similar to the estimated excited state oxidation potential of [Ir(dF(CF3)ppy)2(dtbpy)]PF6 ( +1.21 V vs SCE in acetonitrile). On the other hand, the luminescence was quenched negligible on addition of diphenyl

• disulfide (Figure 3b). Stern–Volmer quenching studies showed that the arene is quenched at a much higher rate than the disulfide (Figure 3c). This indicates that the oxidation of the arene is the key step in the C–H sulfenylation reaction. Anisole does not quench the luminescence of [Ir(dF(CF3)ppy)2(dtbpy

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• . Barton et al. demonstrated in 1990 that [Ru(bpy)2(dppz)]2+ behaves as a light-switch for DNA [5]: this complex is not luminescent in water but upon intercalation within the DNA base pairs stack, the complex luminescence is restored. Derivatives of [Ru(bpy)2(dppz)]2+ and complexes bearing similar aromatic

• luminescence lifetime and determined the quantum yield of luminescence under air and argon atmosphere for conjugate 9 and reference [Ru(TAP)2phen]2+ in water with 5% DMSO in order to avoid any formation of aggregates. The data gathered in Table 1 clearly indicate that the tethering of the [Ru(TAP)2phen]2

• cyclic pentapeptide units c-[RGDfK] 8 (see Supporting Information File 1). No modification of the luminescence by intermolecular quenching was observed, confirming the absence of internal quenching in the conjugate 9. Photoreactivity of RuII-calixarene conjugate 9 The photoreactivity of Ru-TAP complexes

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• chemical structure is sketched in Figure 9 [41]. Depending on the π-conjugation of the NHC-based bidentate ligand, emitting complexes with luminescence varying from blue (19 and 20) to yellow (21) were obtained. Several devices were prepared following a remote phosphor configuration, which places the

• nonradiative deactivation channels [25][44]. Nevertheless, the use of multidentate chromophoric ligands that are able to provide metal–ligand bonds with higher covalent character, as for instance cyclometalating ligands, has proven to be a successful strategy for improving the luminescence properties due to

• , together with the use of heterocyclic moieties such as thiophene or carbazole, clearly favours the luminescence properties of these type of platinum(II) complexes [68]. As aforementioned, N-deprotonable azole units constitute a compelling alternative to C-cyclometalating ligands [16]. In this regard

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• one peak at 593 nm was observed for the dilute toluene solutions of both molecules with the typical PL spectra from the radiative transition of ICT states, which could be the evidence of the existence of strong ICT states of both molecules. More importantly, both materials achieve orange luminescence

• . PLQY measurements of 1:CBP and 2:CBP are 7% and 26%, respectively. The PLQY measurements of the doped films with lower concentration show varying degrees of deviation due to the incomplete energy transfer and the obvious luminescence from CBP (PLQY of 1 and 2 doped in CBP with 1 wt % are 2% and 10

• is a promising acceptor for orange TADF materials, which aids in the design of the TADF behavior and luminescence color of 1 and 2. Owing to the strong electron-withdrawing ability and extended conjugation length of fluorenone unit, the emission peaks of both materials show obvious red-shifts from

Investigating radical cation chain processes in the electrocatalytic Diels–Alder reaction

• Yasushi Imada,
• Yohei Okada and
• Kazuhiro Chiba

Beilstein J. Org. Chem. 2018, 14, 642–647, doi:10.3762/bjoc.14.51

• luminescence quenching experiments [19]. With such an understanding in hand, radical ion chain processes could be further optimized to realize greener transformations. We have been developing anodic cycloadditions [20][21][22][23][24][25] enabled by lithium perchlorate/nitromethane electrolyte solution [26

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• reducing the global energy demand on Earth, two parameters govern the power consumption of OLEDs, namely the quantum yield of luminescence of the light emitting material and the device stacking. Indeed, the driving voltage of OLEDs is highly sensitive to the thickness of the different layers, the charge

• delayed fluorescence (TADF) emitters. As specificity, these materials can thermally repopulate the singlet state from the triplet state by reverse intersystem crossing (RISC), leading to an increase of the luminescence intensity. From the OLEDs viewpoint, TADF emitters behave by harvesting both singlet

• . The decay time of the delayed component of luminescence was determined as being 2.36 μs and 6.71 μs for B1 and B2, respectively. When evaluated in multilayered OLEDs, a blue electroluminescence (EL) peaking at 466 nm and 479 nm, an external quantum efficiency (EQE) of 15.1% and 16.0% were obtained for

Polarization spectroscopy methods in the determination of interactions of small molecules with nucleic acids – tutorial

• Tamara Šmidlehner,
• Ivo Piantanida and
• Gennaro Pescitelli

Beilstein J. Org. Chem. 2018, 14, 84–105, doi:10.3762/bjoc.14.5

• , which is ideal for the selective study of DNA ligands that strongly change fluorescence upon binding [3]. In a sense complementary to FDCD, also circularly polarized luminescence (CPL) is a chiroptical emission technique which has been employed in the same context for the first time recently [12]. The

Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies

• Artur Jabłoński,
• Yannic Fritz,
• Hans-Achim Wagenknecht,
• Rafał Czerwieniec,
• Tytus Bernaś,
• Damian Trzybiński,
• Krzysztof Woźniak and
• Konrad Kowalski

Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249

• . Confocal microscopy confirmed that 5 predominantly stains mitochondria but it also accumulates in the nucleoli of the cells. Keywords: confocal microscopy; luminescence; nucleobases; oligonucleotide binding; pyrene; X-ray; Introduction Pyrene is a planar, polycyclic aromatic hydrocarbon which shows well

• geometry, ten excitations, five without spin flip and five to triplet excited states, respectively, were computed. The results for luminescence relevant transitions are summarized in Table 2. The TD-DFT computations predict, in particular, that the fluorescent state S1 of hydroxy compound 5 with the

• determined by Analytical Services of the Polish Academy of the Sciences, Łódź. Experimental details Luminescence measurements UV–vis absorption spectra were recorded with a Varian Cary 300 double beam spectrometer. Luminescence spectra were measured for air-saturated and degassed diluted (c ≈ 5·10–5 M

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• and materials sciences, including organic solids [2] with pharmaceutical, luminescence- and thermoactive properties; studies of biomolecular recognition, asymmetric catalysis, interlocked systems and racemic resolution [2]. More recently mechanochemical methods were again successfully applied to the

• ], luminescence [67], non-linear optics [68] and magnetism [69], as well as contrast agents for magnetic resonance imaging (MRI) [70] and as drug carriers in systems for controlled drug delivery and release [64][71][72][73][74][75][76][77][78][79][80]. Also under development are new systems with potential use in

• water at approximately 80 °C and melt/decompose above 200–250 °C [124]. This type of BioMOFs enclosing lanthanides and cations with potential luminescence properties can be explored for theranostic applications. Figure 1 shows some examples of the networks obtained. Braga et al. synthesized new BioMOFs