Photomechanochemistry: harnessing mechanical forces to enhance photochemical reactions

• Francesco Mele,
• Ana M. Constantin,
• Andrea Porcheddu,
• Raimondo Maggi,
• Giovanni Maestri,
• Nicola Della Ca’ and
• Luca Capaldo

Beilstein J. Org. Chem. 2025, 21, 458–472, doi:10.3762/bjoc.21.33

• transform molecules. Intriguingly, photocatalysts typically absorb harmless visible light and can be chosen ad hoc to trigger the desired chemistry. Indeed, the photocatalyst–substrate interaction can occur via energy transfer [4][5][6][7][8], single-electron transfer [9][10][11][12], or hydrogen-atom

Red light excitation: illuminating photocatalysis in a new spectrum

• Lucas Fortier,
• Corentin Lefebvre and
• Norbert Hoffmann

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

• organic photocatalysts. Unlike metal-based systems, organic photocatalysts such as phthalocyanins, squaraines and cyanins, offer effective electron and energy transfer under red-light irradiation without relying on transition metals. This shift towards organic catalysts opens new possibilities for

• plausible mechanisms: a photoinduced electron transfer (PET) between the 3MLCT state of the copper complex and DCA or a triplet–triplet energy transfer (TTET) between the 3MLCT state of the copper complex and DCA. In both of these mechanisms, the involvement of a doublet excited-state of the radical anion

• raises the energy of metal-centered states and minimizes non-radiative decay pathways. This design results in prolonged MLCT excited states, making these complexes suitable for challenging triplet–triplet energy transfer (TTET) and photoredox catalysis reactions such as hydrodehalogenation of aryl

Multicomponent reactions driving the discovery and optimization of agents targeting central nervous system pathologies

• Lucía Campos-Prieto,
• Aitor García-Rey,
• Eddy Sotelo and
• Ana Mallo-Abreu

Beilstein J. Org. Chem. 2024, 20, 3151–3173, doi:10.3762/bjoc.20.261

• conducted at a concentration of 10 μM, with donepezil serving as a positive control. To measure their impact on cellular tau oligomerization, the fluorescence resonance energy transfer (FRET) signal intensity was quantified in a cellular tau FRET assay at the same 10 μM concentration, using MK-886, a known

Controlled oligomerization of [1.1.1]propellane through radical polarity matching: selective synthesis of SF₅- and CF₃SF₄-containing [2]staffanes

• Jón Atiba Buldt,
• Wang-Yeuk Kong,
• Yannick Kraemer,
• Masiel M. Belsuzarri,
• Ansh Hiten Patel,
• James C. Fettinger,
• Dean J. Tantillo and
• Cody Ross Pitts

Beilstein J. Org. Chem. 2024, 20, 3134–3143, doi:10.3762/bjoc.20.259

• nanotechnology [5], liquid crystal design [6][7][8][9][10], and the study of energy-transfer [11][12] or electron-transfer [13][14][15][16][17] processes. We also posit that lower-order [n]staffanes (i.e., n = 2 or 3) are potentially valuable C(sp3)-rich bioisosteres [18][19] that have been seemingly overlooked

Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts

• Mandeep K. Chahal

Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257

• to absorb significant amounts of visible light photons, which allows them to reach an excited state. The excited porphyrin molecule is likely to undergo energy transfer (ET; photosensitization) or single-electron transfer (SET; photoredox catalysis) to substrate molecules (Figure 13). In

• and a photosensitizer, facilitating photoinduced electron transfer (PET) to form the active cation radical B, and intersystem crossing (ISC) for energy transfer to generate the triplet carbene C. Radical B then reacted with biradical C, producing the new radical D, which accepted an electron from the

• macrocycles as photocatalysts in organic synthesis, involving both single electron transfer (SET) and energy transfer (ET) mechanistic approaches [84]. This review does not only focus on the metal-free porphyrin macrocycles, but it also covers the area of different porphyrinoid systems, such as heteroatom

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

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

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

• spectra were observed. In the case of compounds 1j and 1n, the endpoint of the photoreaction could not be identified, as a steady decrease of the whole absorption spectra during irradiation indicated secondary decomposition reactions. We previously reported triplet energy transfer between 3[Ru(phen)3](PF6

• alkynylbenzene and alkynylnaphthalene core is also feasible. Quenching experiments of [Ru(phen)3](PF6)2 (triplet energy ET = 2.19 eV [39]) with 1i in acetonitrile yielded a triplet energy transfer rate of kEnT = 5.8 × 109 M−1 s−1 indicating very efficient deactivation of the triplet sensitizer (Figure S4 in

Cyclodextrin-based rotaxanes for polymer materials: challenge on simultaneous realization of inexpensive production and defined structures

• Yosuke Akae

Beilstein J. Org. Chem. 2024, 20, 3026–3049, doi:10.3762/bjoc.20.252

• were observed from the TPA to the conjugative polymer backbone included by perfectly arylated β-CD. TPA units located near the axle polymer are likely to induce an electron transfer, while those located far from the axle polymer tend to cause an excitation energy transfer. Thus, the polymer unit

• excited by the excitation energy transfer is located far from the TPA units, preventing quenching via electron transfer. Meanwhile, around 200 TPA units were included in one polymer molecule. The abovementioned property is induced by the nature of CD, which has many modifiable substituents (hydroxy groups

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

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

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

• proposed to function by Cu2+ sequestration. The remaining report is of a terbium(III) complex [Tb(DPA-N3)3]3− (Figure 7), which contains an aryl azide-functionalized ligand. In this system the azide functionality prohibits the energy transfer to the lanthanide ion, effectively quenching luminescence. In

• did with ([Eu(triazole-DPA)3·Cu]3+, however for the terbium(III) complexes, the electronic state of the ligand, [triazole-DPA]2− is altered, resulting in the energy gap of the ligand and the excited energy level of the Tb3+ ion being smaller. This would facilitate efficient back-energy transfer from

Interaction of a pyrene derivative with cationic [60]fullerene in phospholipid membranes and its effects on photodynamic actions

• Hayato Takagi,
• Çetin Çelik,
• Ryosuke Fukuda,
• Qi Guo,
• Tomohiro Higashino,
• Hiroshi Imahori,
• Yoko Yamakoshi and
• Tatsuya Murakami

Beilstein J. Org. Chem. 2024, 20, 2732–2738, doi:10.3762/bjoc.20.231

• the 1O2 adduct of 4-oxo-TEMP (4-oxo-TEMPO) were observed in the dispersion of catC60-lip ([catC60] = 5 µM) in PBS(–) showing an evidence of energy transfer reaction by the photoexcited catC60 (Figure 5a(ii)). In the presence of electron donor (NADH) under photoirradiation, •OH generation was observed

• same time, unusually fast conversion of O2•– to •OH was also suggested in this system. The results above suggest that catC60-lip generated both types of ROS (1O2 and •OH) via energy transfer and electron transfer mechanisms. The present results are in line with previous studies of photoinduced ROS

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

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

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

• white-light-emitting materials. Keywords: energy transfer; fluorinated diphenylacetylenes; photoluminescence; polymer-dispersed films; white luminescence; Introduction Luminescent materials in lighting and display devices have become indispensable in daily life [1][2][3]. In recent years, organic

• λPLs at approximately 504 and 390 nm, respectively. The fluorescent color of the PMMA film mixed in a 50:50 ratio showed light green–yellow PL with chromaticity coordinates of (0.24, 0.45), which suggests a rapid energy transfer of the excitation energy from blue fluorophore 1a to green–yellow

• absorption spectrum of 1a in the two-component film. This result also clearly suggests an energy transfer from 1a to 1c. The fluorescence resonance energy transfer efficiency (EFRET) [30][31] was calculated from the ratio of the fluorescence lifetimes of the two- and high-energy-component films (Equation 1

Novel truxene-based dipyrromethanes (DPMs): synthesis, spectroscopic characterization and photophysical properties

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2024, 20, 2163–2170, doi:10.3762/bjoc.20.186

• ), organogels, molecular wires, self-assembly and so forth [14][15][16][17][18][19][20][21][22][23][24][25]. Moreover, nowadays these invaluable compounds have also received great attention of supramolecular chemists, and finds applications in sensing, catalysis, donor–acceptor systems, energy transfer and

Generation of alkyl and acyl radicals by visible-light photoredox catalysis: direct activation of C–O bonds in organic transformations

• Mithu Roy,
• Bitan Sardar,
• Itu Mallick and
• Dipankar Srimani

Beilstein J. Org. Chem. 2024, 20, 1348–1375, doi:10.3762/bjoc.20.119

• catalysis In recent times, visible-light-mediated photoredox chemistry has evolved as a unique tool for various organic transformations. In contrast to traditional catalysis, the photochemical process uses an electron or energy transfer mechanism to form reactive intermediates. Typically, a photocatalyst is

• triggered to carry out energy transfer and electron transfer or proton-coupled electron transfer when it absorbs light of an appropriate wavelength (Figure 2). These processes generate highly reactive species, such as radical cations or anions, which can initiate the desired organic transformations

Diameter-selective extraction of single-walled carbon nanotubes by interlocking with Cu-tethered square nanobrackets

• Guoqing Cheng and
• Naoki Komatsu

Beilstein J. Org. Chem. 2024, 20, 1298–1307, doi:10.3762/bjoc.20.113

• mechanically interlocking cyclic molecules are reported not to be removed with washing [11][22][23][24]. In addition, these Raman signals of 1b shift to higher frequencies at e- and i-SWNTs, similarly to our previous report [11], probably due to the structural change of Cu-nanobrackets 1b, or the energy

• transfer between the interlocked SWNTs and the cyclic Cu-nanobrackets. After thorough removal of the host molecules with DTT, weak signals are remained at p-SWNTs, known as intermediate frequency modes (IFM) of SWNTs [25]. The IFM signals are also observed in e- and i-SWNTs, showing the coexistence of both

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

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

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

• catalyst in the sulfonylation/arylation of styrenes and as a triplet sensitizer in energy transfer catalysis. The singlet lifetime is sufficiently long to exploit the exceptional excited state reduction potential for the activation of 4-cyanopyridine. Photoinduced electron transfer generating the radical

• increased when the triplet efficiently reacts in a catalytic cycle such that turnover numbers exceeding 4400 are achievable with this organocatalyst. Keywords: energy transfer; laser spectroscopy; organocatalyst; photoredox; time-resolved spectroscopy; Introduction The emergence of photoredox chemistry in

• lifetimes, limiting their use in collision-based electron/energy transfer reactions unless high substrate concentrations are used [29][30]. In contrast, triplet states populated via intersystem crossing (ISC) have much longer lifetimes and can efficiently react at lower substrate concentrations [30

(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