(Bio)isosteres of ortho- and meta-substituted benzenes

• H. Erik Diepers and
• Johannes C. L. Walker

Beilstein J. Org. Chem. 2024, 20, 859–890, doi:10.3762/bjoc.20.78

• substituents. It is therefore unsurprising that the number of methods seeking to access these has increased in recent times. In 2022 Brown and co-workers reported a strain release [2π + 2σ] cycloaddition induced by triplet energy transfer for the synthesis of 1,2,4-BCHs and 1,2,5-BCHs [38]. Some earlier

• was also employed for the synthesis of 1,2,4-BCHs [35]. Heterocycle-substituted BCHs were accessed by [2π + 2σ] photocycloaddition by Glorius and co-workers [79] and Houk, Glorius and co-workers [80]. This reactivity was enabled by triplet energy transfer catalysis activating the heterocyclic

• by Lewis acid-catalysed cyclisation of bicyclobutanes with aldehydes [84] and polysubstituted 2-oxa-BCHs bearing more complex substitution patterns were synthesised by triplet energy transfer catalysis from benzoylformate esters and bicyclobutanes [85]. Reports of polysubstituted scaffolds larger

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

• ) addition because of a photoinduced energy transfer between porphyrins and the copper center. The fluorescence can be recovered by the addition of a bidentate pyrophosphate guest ligand, which disturbs the geometry of the system (octahedral complex) and thus lowers the energy transfer. Jang and co-workers

Mechanisms for radical reactions initiating from N-hydroxyphthalimide esters

• Carlos R. Azpilcueta-Nicolas and
• Jean-Philip Lumb

Beilstein J. Org. Chem. 2024, 20, 346–378, doi:10.3762/bjoc.20.35

• electronically excited substrate (*S) through an energy transfer (EnT) mechanism (path c). In addition to these mechanistic blueprints, the formation of charge-transfer complexes involving NHPI esters, as well as examples of photoinduced transition metal-catalyzed activation will be discussed. Depending on the

• photosensitizer in an energy-transfer (EnT) mechanism. This proposal was supported by fluorescence quenching measurements, as well as the direct excitation of 44 by UV irradiation, resulting in the formation of 45 in a 45% yield. According to this hypothesis, NHPI ester 44 would adopt a favorable conformation (46

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

• TCBD, donor–acceptor conjugated systems have been systematically developed by coupling the TCBD motif with an electron donor, resulting in the experimental observation of photoinduced electron- and energy-transfer events. In 2014, comprehensive investigations on the photophysical properties of

• the plausible energy transfer from the local charge-separated (CS) state of the push–pull chromophore (namely N,N-diethylanilino (DEA)•+–TCBD•−) to the singlet excited state of C60 (1C60*). In transient absorption spectral measurements conducted via the femtosecond laser-flash photolysis of compound

• determined to be 2 and 165 ps, respectively, via multiwavelength analyses. The excitation at 640 nm, a wavelength proximate to the CT band, failed to induce any discernible electron or energy transfer from the DEA moiety to the C60 core. When compound 77 underwent photoexcitation at 640 nm, the CT band

Electron-beam-promoted fullerene dimerization in nanotubes: insights from DFT computations

• Laura Abella,
• Gerard Novell-Leruth,
• Josep M. Ricart,
• Josep M. Poblet and
• Antonio Rodríguez-Fortea

Beilstein J. Org. Chem. 2024, 20, 92–100, doi:10.3762/bjoc.20.10

• electron microscopy (TEM) is a technique that has been used for a long time to provide images of molecules, but also to monitor the reactions triggered by the energy transfer of the electron beam to the atoms that build the molecules. In particular, the advances in TEM as well as in methods to anchor

Thienothiophene-based organic light-emitting diode: synthesis, photophysical properties and application

• Recep Isci and
• Turan Ozturk

Beilstein J. Org. Chem. 2023, 19, 1849–1857, doi:10.3762/bjoc.19.137

• (excitation at λmax), respectively, leading to a mega Stokes shift (>100 nm) of 109 nm, which could be explained to be due to a fast relaxation from the excited state to the ground state as a result of a powerful intramolecular energy transfer between the TPA and boron groups through the thieno[3,2-b

Photoredox catalysis harvesting multiple photon or electrochemical energies

• Mattia Lepori,
• Simon Schmid and
• Joshua P. Barham

Beilstein J. Org. Chem. 2023, 19, 1055–1145, doi:10.3762/bjoc.19.81

• which strategy is a more suitable fit for a given purpose. In order to do so, the scope of our Review is thus restricted to electron transfer redox processes and does not include energy transfer or atom/group transfer processes. Particularly interesting are instances where the same active catalytic

• where the photoredox-active species is generated by an initial energy transfer process – such as triplet-triplet annihilation (TTA) upconversion – are excluded from this Review as i) they are comprehensively and elegantly reviewed elsewhere [17], and ii) comparisons are not straightforward to make with

Light-responsive rotaxane-based materials: inducing motion in the solid state

• Adrian Saura-Sanmartin

Beilstein J. Org. Chem. 2023, 19, 873–880, doi:10.3762/bjoc.19.64

• direction, one potential strategy is the approach followed by Feringa and co-workers [72], in which palladium-porphyrin photosensitizer-based struts were employed within a metal-organic material, allowing the use of green light as irradiation source because of the effective energy transfer between these

Phenanthridine–pyrene conjugates as fluorescent probes for DNA/RNA and an inactive mutant of dipeptidyl peptidase enzyme

• Josipa Matić,
• Tana Tandarić,
• Marijana Radić Stojković,
• Filip Šupljika,
• Zrinka Karačić,
• Ana Tomašić Paić,
• Lucija Horvat,
• Robert Vianello and
• Lidija-Marija Tumir

Beilstein J. Org. Chem. 2023, 19, 550–565, doi:10.3762/bjoc.19.40

• ) compared to neutral pH (unprotonated phenanthridine nitrogen) caused more efficient stacking and the hypochromic effect. However, the energy transfer between chromophores and resulting excimer fluorescence was increased at neutral and basic conditions. The excimer fluorescence was obviously sensitive to

CuAAC-inspired synthesis of 1,2,3-triazole-bridged porphyrin conjugates: an overview

• Dileep Kumar Singh

Beilstein J. Org. Chem. 2023, 19, 349–379, doi:10.3762/bjoc.19.29

• treatment of free-base porphyrins with zinc acetate. The photophysical studies of these synthesized conjugates revealed that some of them show substantial intramolecular energy transfer between porphyrin and coumarin moieties. Similar to coumarins, synthetic and naturally occurring xanthones also possess

• °C [34] (Scheme 8). Further, nickel derivatives 44b–48b were also obtained from their zinc analogues by demetallation with concentrated HCl and metalation with nickel acetate. The preliminary photophysical results revealed a significant intramolecular energy transfer between the porphyrin core and

• a similar synthetic protocol to link porphyrin 71 to a fluorescein 72 through a 1,2,3-triazole linker to form the porphyrin-fluorescein conjugate 73 in 91% yield (Scheme 14). Furthermore, the fluorescence study of conjugate 73 revealed an intramolecular energy transfer between fluorescein and

Supramolecular approaches to mediate chemical reactivity

• Pablo Ballester,
• Qi-Qiang Wang and
• Carmine Gaeta

Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152

• supramolecular nanostructures, displayed aggregation-induced emission (AIE) due to the restricted phenyl-ring rotation of m-TPEWP5 component. Inspired by natural photosynthesis and following an energy transfer process, the supramolecular nanorod assembly was employed as a nanoreactor for a photocatalytic

Ionic multiresonant thermally activated delayed fluorescence emitters for light emitting electrochemical cells

• Merve Karaman,
• Abhishek Kumar Gupta,
• Subeesh Madayanad Suresh,
• Tomas Matulaitis,
• Lorenzo Mardegan,
• Daniel Tordera,
• Henk J. Bolink,
• Sen Wu,
• Stuart Warriner,
• Ifor D. Samuel and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2022, 18, 1311–1321, doi:10.3762/bjoc.18.136

• the non-doped device, at 2.0% demonstrated 100% exciton utilization efficiency in the device and efficient energy transfer from the host to the guest cyanine emitter. Deep blue emission in LEECs is challenging. We also reported a blue-emitting LEEC employing a cationic sulfone-based donor–acceptor

• presence of emissive aggregates in the emissive layer [19]. Interestingly, in the host–guest system the energy transfer is not complete and both molecules are responsible for the electroluminescence, with a λEL at 586 nm, between the emission of the neat films. JVL characterization (from −2 to 8 V) was

Thermally activated delayed fluorescence (TADF) emitters: sensing and boosting spin-flipping by aggregation

• Ashish Kumar Mazumdar,
• Gyana Prakash Nanda,
• Nisha Yadav,
• Upasana Deori,
• Upasha Acharyya,
• Bahadur Sk and
• Pachaiyappan Rajamalli

Beilstein J. Org. Chem. 2022, 18, 1177–1187, doi:10.3762/bjoc.18.122

• developed mainly by focusing on photophysical processes, such as photoinduced electron transfer (PET), excited-state intramolecular proton transfer (ESIPT), fluorescence resonance energy transfer (FRET), etc. [21][22][24][25]. Several literature reports have also demonstrated the switching of fluorescence

Radical cation Diels–Alder reactions of arylidene cycloalkanes

• Kaii Nakayama,
• Hidehiro Kamiya and
• Yohei Okada

Beilstein J. Org. Chem. 2022, 18, 1100–1106, doi:10.3762/bjoc.18.112

• trend is observed in photosensitized [2 + 2] cycloadditions [48]. Since their report was not a [4 + 2] but a [2 + 2] reaction and they proposed an energy transfer mechanism as opposed to an electron transfer pathway, it cannot be directly compared to our results. Even so, it would be fair to say that

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

• transfer) that include organic materials and supramolecular assemblies. Recently, FRET phenomena have been successfully demonstrated in supramolecular architectures based on metal organic frameworks and covalent organic frameworks [62][63][64]. However, poor solubility of such polymeric systems in common

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

• intramolecular phenyl-ring rotations and functioned as an ideal donor. After the loading of eosin Y (EsY) as acceptor on the surface of the assembly of m-TPEWP5 and G, the worm-like nanostructures changed into nanorods, which facilitates a Förster resonance energy transfer (FRET) from the m-TPEWP5 and G

• photosynthesis and exhibited a high catalytic efficiency for the photocatalytic dehalogenation reaction of various bromoketone derivatives with good yields in short reaction time in water. Keywords: aggregation-induced emission; Förster resonance energy transfer; host–guest interaction; photocatalysis

• chemical energy [4][5][6]. Mainly, both antenna molecules and proteins on the thylakoid membrane are combined to form a light-harvesting system through noncovalent interactions. Inspired by photosynthesis, extensive research has been devoted to construct energy transfer systems for the better utilization

Visible-light-mediated copper photocatalysis for organic syntheses

• Yajing Zhang,
• Qian Wang,
• Zongsheng Yan,
• Donglai Ma and
• Yuguang Zheng

Beilstein J. Org. Chem. 2021, 17, 2520–2542, doi:10.3762/bjoc.17.169

• chemical energy via photosynthesis [1]. Photochemical reactions mimic natural photosynthesis, and photoredox catalysis plays a key role in energy-transfer processes [2][3][4][5]. Over the past decades, photoredox catalysis has attracted an increasing amount of attention [6][7][8][9], and a series of

Photoredox catalysis in nickel-catalyzed C–H functionalization

• Lusina Mantry,
• Rajaram Maayuri,
• Vikash Kumar and
• Parthasarathy Gandeepan

Beilstein J. Org. Chem. 2021, 17, 2209–2259, doi:10.3762/bjoc.17.143

• reaction times (24–96 h). The authors proposed a catalytic cycle to account for the mode of operation as depicted in Figure 5 [57]. Thus, the in situ-generated nickel(0) complex 5-III undergoes oxidative addition into aryl bromide 3a to form nickel(II) complex 5-IV. The triplet–triplet energy transfer from

• products were observed when unsubstituted and electron-rich aryl bromides were used. Based on their experimental results, the authors proposed that a triplet–triplet energy transfer occurs between the nickel(II)–aryl species 7-IV and the excited acridinium photocatalyst *Mes-Acr-Me+ 7-II (Figure 7) [64

• involves an energy-transfer pathway generating an electronically excited nickel complex as a key reactive intermediate (Figure 11). Photochemical nickel catalysis was used to synthesize 1,1-diarylalkanes 39 from unactivated alkyl bromides 38 and aryl bromides 3 through a reductive migratory cross-coupling

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• monitoring of the temperature-dependent Förster resonance energy transfer (FRET) between the dyes [46]. The particular oligonucleotide sequences were chosen because they are known to be involved in biologically relevant processes, namely in the transcription regulation of myc (FmycT) [47][48], kit (FkitT

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

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

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• with various macrocyclic hosts as well as on the role of macrocyclic-hosts-assisted hybrid materials in energy transfer. To keep the clarity of this review, the macrocycles are categorized into the most commonly used supramolecular hosts, including crown ethers, cyclodextrins, cucurbiturils

• -assisted hybrid materials in energy transfer. To date, several supramolecular hosts have been developed that can provide defined properties of, and exert catalytic control on reactive substrates (guests) [7][8][9]. To keep the clarity, we categorized this into the five most universally used important

• supramolecular hosts to recognize guests through hydrophobicity, π–π stacking, cation–π interactions, ion–dipole interactions, etc. [31][32]. Due to the cavity-shape limitation of calixarenes, most calixarene-based photocatalytic systems are mainly based on the fabrication of hybrid materials for energy transfer

Control over size, shape, and photonics of self-assembled organic nanocrystals

• Chen Shahar,
• Yaron Tidhar,
• Yunmin Jung,
• Haim Weissman,
• Sidney R. Cohen,
• Ronit Bitton,
• Iddo Pinkas,
• Gilad Haran and
• Boris Rybtchinski

Beilstein J. Org. Chem. 2021, 17, 42–51, doi:10.3762/bjoc.17.5

• upon drying, as was evidenced by TEM and atom force microscopy. Photophysical studies, including femtosecond transient absorption spectroscopy, revealed a distinct influence of the ONC morphology on their photonic properties (excitation energy transfer was observed only in the high-aspect ONCs

Molecular basis for protein–protein interactions

• Brandon Charles Seychell and
• Tobias Beck

Beilstein J. Org. Chem. 2021, 17, 1–10, doi:10.3762/bjoc.17.1

• resonance (SPR) spectroscopy [27][28], gel filtration [29], isothermal titration calorimetry (ITC) [30][31], fluorescence resonance energy transfer [32], and microscale thermophoresis [33]. In SPR spectroscopy, one of the protein molecules that make up the complex is first immobilised on a metal surface

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• intensities of absorption or emission at two wavelengths minimizes the error from the physical or chemical fluctuations in the sample. Conventional peptide probes based on environment-sensitive fluorophores [20][21][22], fluorescence resonance energy transfer (FRET) pairs [13] and pyrene excimer/monomer [23

• ). Fluorescence resonance energy transfer (FRET) relies on the distance-dependent transfer of energy from a donor fluorophore to an acceptor fluorophore. Genetically encoded fluorophores, such as green fluorescent protein (GFP) and related blue, cyan, yellow and red fluorescent proteins have provided the ability

• arms attached through their C-terminus to a central lysine. Two heparin sensors 10 and 11 are developed by attaching the N-terminus of the peptide beacon with pyrenes and fluorescence resonance energy transfer (FRET) pair (naphthalene and dansyl), respectively for ratiometric detection of heparin

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• nucleic acids via Förster Resonance Energy Transfer (FRET) [20]. More recently, we started an effort to develop an efficient strategy for the preparation of a linker-modified adenosine building block, which in a future project is to be used for post synthetic conjugation of reporters or functional

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• experiments. For that purpose, the DNA melting temperature Tm of the dye-labeled oligonucleotides F21T and Fa2T (for sequence see caption of Figure 2) was monitored by fluorescence spectroscopy, as the thermally induced unfolding of the quadruplex disrupts the Förster resonance energy transfer (FRET) between