Photochromic derivatives of indigo: historical overview of development, challenges and applications

• Gökhan Kaplan,
• Zeynel Seferoğlu and
• Daria V. Berdnikova

Beilstein J. Org. Chem. 2024, 20, 228–242, doi:10.3762/bjoc.20.23

• in chloroform and carbon tetrachloride upon exposure to orange light. The lifetime of Z-11a in CCl4 was significant and the thermal backward reaction occurred in darkness with the restoration of the initial absorption of the E-isomer for 57% after 5 h and for 100% in 18 h. N,N'-Diethylindigo (11b

• particular, the lifetime of Z-11a in CCl4 was found to be only 3.1 s versus 18 h measured previously. Nevertheless, it was obvious that N,N'-dialkylindigos were prone to the reversible photochemical isomerization. In addition, it was also found that the thermal backward Z–E conversion of 11a and 12

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

• absorption intensity at 700 nm, corresponding to the triplet excited state of C60 (3C60*), was observed along with the decay of the CS state with a lifetime of 1,380 ps. Conversely, for compound 77, excitation at 387 nm was required for the formation of the CS state and an increase in the absorption

• intensity at 890 nm, indicating the emergence of 1C60* state with a lifetime of 115 ps, was accompanied by a subsequent increase in the absorption intensity at 1,021 nm, corresponding to the formation of the C60 radical anion. The lifetimes of the charge separation and charge recombination events were

• lifetime of 71 ps in toluene. Meanwhile, the absorption at 640 nm, corresponding to the ZnP radical cation, was not observed. The results obtained from Rehm–Weller’s equation [146] suggested that photoinduced electron transfer was thermodynamically permitted in 86. However, ultrafast energy transfer from

Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions

• Julika Schlosser,
• Olga Fedorova,
• Yuri Fedorov and
• Heiko Ihmels

Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11

• damage. In order to investigate the involvement of singlet oxygen in the DNA cleavage process, the samples were irradiated in the presence of NaN3 or in D2O (Table 3, Supporting Information File 1, Figure S18). The latter is known to extend the lifetime of singlet oxygen by a factor of ca. 10 as compared

Beyond n-dopants for organic semiconductors: use of bibenzo[d]imidazoles in UV-promoted dehalogenation reactions of organic halides

• Kan Tang,
• Megan R. Brown,
• Chad Risko,
• Melissa K. Gish,
• Garry Rumbles,
• Phuc H. Pham,
• Oana R. Luca,
• Stephen Barlow and
• Seth R. Marder

Beilstein J. Org. Chem. 2023, 19, 1912–1922, doi:10.3762/bjoc.19.142

• amplitude at 654 nm decays with a 1 ps lifetime. The isosbestic point in Figure 4a is consistent with a clean transformation such as monomer formation. The corresponding monomeric radicals are calculated using TD-DFT (M06/6-31G(d,p)) (Figure 4e) to have absorptions at similar energies to those seen in the

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

• efficiencies pointed out that DMB-TT-TPA (8) is among the best D–π–A modal fluorophores suitable for an OLED application. Moreover, the photophysical properties of DMB-TT-TPA (8) were investigated through time-resolved fluorescence studies (390 nm laser source in THF). The fluorescence lifetime (τ) of DMB-TT

Selectivity control towards CO versus H₂ for photo-driven CO₂ reduction with a novel Co(II) catalyst

• Lisa-Lou Gracia,
• Philip Henkel,
• Olaf Fuhr and
• Claudia Bizzarri

Beilstein J. Org. Chem. 2023, 19, 1766–1775, doi:10.3762/bjoc.19.129

• ), while a reductive quenching by BIH could be possible since the oxidation potential of BIH is 0.27 V (ΔG < −0.25 V). We performed Stern–Volmer analyses to verify our hypothesis. As expected, the lifetime of the PS* (τ0 = 14 ns in aerated DMA/TEA 7:1), is reduced upon the addition of the sacrificial

Charge carrier transport in perylene-based and pyrene-based columnar liquid crystals

• Alessandro L. Alves,
• Simone V. Bernardino,
• Carlos H. Stadtlober,
• Edivandro Girotto,
• Giliandro Farias,
• Rodney M. do Nascimento,
• Sergio F. Curcio,
• Thiago Cazati,
• Marta E. R. Dotto,
• Juliana Eccher,
• Leonardo N. Furini,
• Hugo Gallardo,
• Harald Bock and
• Ivan H. Bechtold

Beilstein J. Org. Chem. 2023, 19, 1755–1765, doi:10.3762/bjoc.19.128

• spin-coated films, the best fitting of the decay curves of 1 and 2 indicated three and two lifetimes, respectively. Compound 1 displayed a dominant and longer lifetime compared to solution, 25.9 ns (66.83%), attributed to excimer emission, which usually presents longer lifetimes compared to the

• monomeric species [34]. It agrees with the intensity inversion of the vibronic absorption bands and PL redshift in the spin-coated film compared to the solution. The intensity inversion suggests formation of H-aggregates, leading to excimer fluorescence [35]. Due to the similarity to the lifetime in

• solution, the 6.90 ns lifetime in the film is attributed to monomeric emission. The shortest lifetime of 0.90 ns can be related to the emission of aggregated species driven by π–π interactions [36], contributing to almost 20% of the total emission of 1. The longer lifetime of 2 in film (3.84 ns) can be

Radical chemistry in polymer science: an overview and recent advances

• Zixiao Wang,
• Feichen Cui,
• Yang Sui and
• Jiajun Yan

Beilstein J. Org. Chem. 2023, 19, 1580–1603, doi:10.3762/bjoc.19.116

• conventional radical polymerization. Most free radicals have an extremely short lifetime due to a diffusion-controlled termination process between two free radicals. The inevitable termination between radicals makes the synthesis of well-defined polymers and co-polymers very difficult. In addition, polymers

Organic thermally activated delayed fluorescence material with strained benzoguanidine donor

• Alexander C. Brannan,
• Elvie F. P. Beaumont,
• Nguyen Le Phuoc,
• George F. S. Whitehead,
• Mikko Linnolahti and
• Alexander S. Romanov

Beilstein J. Org. Chem. 2023, 19, 1289–1298, doi:10.3762/bjoc.19.95

• aerated MCH solution. The reduction in quantum yield on exposure to oxygen is due to quenching of the triplet excited states indicating a TADF luminescence mechanism. PLQY in Zeonex films is 39% in air, which is lower than the PLQY of 87% reported for 4CzIPN [17]. The two-component excited state lifetime

• with prompt and delayed fluorescence is characteristic for the TADF-type luminescence [1]. The excited state lifetime of 4BGIPN has a biexponential decay with a prompt fluorescence τp = 13 ns and a delayed fluorescence τd = 1655 ns components in MCH solution. Zeonex films of 4BGIPN exhibit a similar

• profile remained broad and featureless (Figure 5) in Zeonex matices. Notably, a frozen MCH glass exhibits a new vibronically resolved component at 405 and 470 nm, together with a broad CT profile. The first resolved high-energy PL component at 405 nm (Figure 5 top right) has a lifetime of 13 ns, which we

Enabling artificial photosynthesis systems with molecular recycling: A review of photo- and electrochemical methods for regenerating organic sacrificial electron donors

• Grace A. Lowe

Beilstein J. Org. Chem. 2023, 19, 1198–1215, doi:10.3762/bjoc.19.88

• range expected for photosensitizer quenching. Triethylamine has the lowest oxidation potential and is the most reducing of the 3 species (0.69 V vs SCE) which means that it can both reductively quench Ru(bpy)3 and regenerate photooxidized Ru(bpy)3 if the lifetime and electron-transfer rates are

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

• , or it is trapped with pyrrole derivatives 3 in a C–C bond formation to afford arylated products 4. Based on the ultrashort lifetime of *PDI•− (τ = 145 ps), the notion of its photochemistry has attracted skepticism and it has been suggested decomposition products of *PDI•− may instead serve as

• a halogen atom transfer (XAT) agent [101]. While yields of the monophotonic oxidative quenching route and the (biphotonic) conPET reductive quenching route were generally well comparable, the RQ route clearly benefits from a longer lifetime of the key catalytic species, shorter reaction times and

The effect of dark states on the intersystem crossing and thermally activated delayed fluorescence of naphthalimide-phenothiazine dyads

• Liyuan Cao,
• Xi Liu,
• Xue Zhang,
• Jianzhang Zhao,
• Fabiao Yu and
• Yan Wan

Beilstein J. Org. Chem. 2023, 19, 1028–1046, doi:10.3762/bjoc.19.79

• unambiguous experimental evidence that the spin–vibronic coupling of 3CS/3LE states is crucial for TADF. Without the mediating effect of the 3LE state, no TADF is resulted, even if the long-lived 3CS state is populated (lifetime τCS ≈ 140 ns). This experimental result confirms the 3CS → 1CS reverse

• emitters [32][33]. However, the most popular optical spectroscopic methods previously used in this area, such as the very often used transient photoluminescence spectral measurement or the luminescence lifetime measurement, are unable to detect the dark states of the TADF emitters, i.e., the 3LE and 3CS

• dyads containing native PTZ units in HEX show an obvious double exponential feature. For example, the lifetime of NI-PTZ-F is 24 ns (96.3%)/1.2 µs (3.7%) under N2 atmosphere (Figure 4a). The short-lived component can be attributed to the prompt fluorescence of 1CS → S0, while the long-lived component is

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

• extinction coefficient and long emission lifetime (>100 ns) [3]. Their large aromatic hydrophobic surface allows the intercalation between DNA/RNA base pairs and binding within the minor groove. Pyrenes are also prominent protein probes that can monitor protein conformational changes because of pyrene

Transition-metal-catalyzed domino reactions of strained bicyclic alkenes

• Austin Pounder,
• Eric Neufeld,
• Peter Myler and
• William Tam

Beilstein J. Org. Chem. 2023, 19, 487–540, doi:10.3762/bjoc.19.38

• ) catalyst producing 179 which undergoes a cis addition to the azaspirotricyclic alkene resulting in intermediate 180. C–H cleavage at the ortho-position followed by an intramolecular reductive elimination affords in 182. Unlike previous reports [80], this arylrhodium complex has a long enough lifetime to

Naphthalimide-phenothiazine dyads: effect of conformational flexibility and matching of the energy of the charge-transfer state and the localized triplet excited state on the thermally activated delayed fluorescence

• Kaiyue Ye,
• Liyuan Cao,
• Davita M. E. van Raamsdonk,
• Zhijia Wang,
• Jianzhang Zhao,
• Daniel Escudero and
• Denis Jacquemin

Beilstein J. Org. Chem. 2022, 18, 1435–1453, doi:10.3762/bjoc.18.149

• can be controlled. The singlet oxygen quantum yield (ΦΔ) of NI-PTZ is moderate in n-hexane (HEX, ΦΔ = 19%). TADF was observed for the dyads, the biexponential luminescence lifetime are 16.0 ns (99.9%)/14.4 μs (0.1%) for the dyad and 7.2 ns (99.6%)/2.0 μs (0.4%) for the triad. Triplet state was

• , one should be careful with the interpretation of such data, as the quenching of the fluorescence in aerated solution does not necessarily imply TADF, since fluorescence species with long fluorescence lifetime can be also quenched by O2 (a paramagnetic species). This is in particular relevant for the

• lifetime is 16.0 ns (99.9%)/14.4 μs (0.1%) in deaerated n-hexane (Figure 4a). In aerated solution, the luminescence lifetime is reduced to 7.6 ns (99.8%)/0.19 μs (0.2%) (Figure 4d). These are footprints for TADF. Similar features were reported for an analogous NI-PTZ dyad [20]. NI-PTZ2 displays similar

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

• of TADF. Unlike the delayed emission lifetime of DiKTa (15 μs in 3.5 wt % mCP, 23 μs in PhMe) [27], and its derivatives such as Cz-DiKTa (τD = 196 μs, 2 wt % mCP), DMAC-DiKTa (τD = 6.6 μs, 2 wt % mCP), and QAD-mTDPA (τD = 168 μs, in 2 wt % mCP) in Figure 1b [28][40], the delayed lifetimes from DiKTa

• in mCP as the emitter layer were prepared. The devices showed no turn-on, both in lifetime measurements and in current density and luminance versus voltage sweeps (JVL) up to 8 V. Most likely the low content of ionic species in the neutral matrix hindered the required ionic transport for LEEC

Mechanochemical bottom-up synthesis of phosphorus-linked, heptazine-based carbon nitrides using sodium phosphide

• Blaine G. Fiss,
• Georgia Douglas,
• Michael Ferguson,
• Jorge Becerra,
• Jesus Valdez,
• Trong-On Do,
• Tomislav Friščić and
• Audrey Moores

Beilstein J. Org. Chem. 2022, 18, 1203–1209, doi:10.3762/bjoc.18.125

• lifetimes showed a marked increase upon replacement of the nitrogen linker for phosphorus. Nitrogen-linked g-CN showed exciton lifetimes of 4.2 µs, while the introduction of a phosphorus linker in g-h-PCN increases the lifetime to 67 µs, with g-h-PCN300 showing lifetimes of 42 µs. We have also observed a

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

• enhancement of the PF and DF lifetimes, respectively, for BPy-pTC in the aggregated state as compared to the THF solutions (Figure 5a and Table 2). However, only the PF lifetime was enhanced in BPy-p3C (3.5-fold), and no significant change was obtained in the DF lifetime of the aggregates (Figure 5b and Table

•  2). Therefore, it is evident that the aggregation helped to suppress the fluorescence quenching as well as to boost the DF by reducing the ΔEST in BPy-pTC. At the same time, the significant enhancement of the PF lifetime was due to the molecular rigidification and restriction of D–A rotation in BPy

Synthesis, optical and electrochemical properties of (D–π)₂-type and (D–π)₂Ph-type fluorescent dyes

• Kosuke Takemura,
• Kazuki Ohira,
• Taiki Higashino,
• Keiichi Imato and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2022, 18, 1047–1054, doi:10.3762/bjoc.18.106

• decay measurements were performed on a HORIBA DeltaFlex modular fluorescence lifetime system using a Nano LED pulsed diode excitation source (451 nm). Cyclic voltammetry (CV) curves were recorded in DMF/Bu4NClO4 (0.1 M) solution with a three-electrode system consisting of Ag/Ag+ as the reference

DABCO-promoted photocatalytic C–H functionalization of aldehydes

• Bruno Maia da Silva Santos,
• Mariana dos Santos Dupim,
• Cauê Paula de Souza,
• Thiago Messias Cardozo and
• Fernanda Gadini Finelli

Beilstein J. Org. Chem. 2021, 17, 2959–2967, doi:10.3762/bjoc.17.205

• a common inexpensive organic base with two nitrogen atoms in a bicyclic cage structure. The interaction between these two nitrogen atoms makes DABCO easier to oxidize and improves the lifetime of the radical cation species when compared to quinuclidine [7]. Investigation of DABCO as a hydrogen

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

• 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

• involvement of triplet states in the emission. When compared to ICzTRZ in degassed toluene, DICzTRZ presents comparable τp (9.0 ns for ICzTRZ), while we observe a substantial one order of magnitude decrease in the delayed lifetime, τd, (229.2 µs for ICzTRZ [14]), reflective of a more efficient RISC process

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

• state is transformed to the lowest-energy triplet MLCT state, which has a sufficient lifetime for initiating single-electron transfer. In the triplet species, the electron in the higher singly occupied molecular orbital (SOMO) is transferred from RuII* to an external acceptor (A), thereby yielding

• -planar geometry, thereby resulting in a shorter excited state lifetime compared with ruthenium and iridium-based photocatalysts and thus limiting the application of CuI complexes to visible-light-mediated organic syntheses [22][31]. Homoleptic CuI bisphenanthroline complexes were designed with

• the homoleptic and heteroleptic CuI complexes [22][31][36]. The introduction of bulky ligand substituents might efficiently prevent the reorganization of the excited state. Thus, changing the nature of the chelating ligand can improve the photostability and lifetime of the excited state to meet the

In-depth characterization of self-healing polymers based on π–π interactions

• Josefine Meurer,
• Julian Hniopek,
• Johannes Ahner,
• Michael Schmitt,
• Jürgen Popp,
• Stefan Zechel,
• Kalina Peneva and
• Martin D. Hager

Beilstein J. Org. Chem. 2021, 17, 2496–2504, doi:10.3762/bjoc.17.166

• compared to other self-healing supramolecular polymers, e.g., metallopolymers [25]. Supramolecular polymers feature certain temperature ranges, in which the noncovalent bond is activated. The degree of reversibility can be determined by the supramolecular bond lifetime [26]. For example, a study regarding

• ionomers revealed a strong correlation of the bond lifetime with the healing behavior [27]. A similar behavior was also observed for metallopolymers [13]. Consequently, the polymers P1 and P2 were also studied by frequency sweeps at certain temperatures (see Figure 3). At temperatures below the endothermic

• supramolecular bond lifetime was determined to be 15.87 s at 135 °C (P1) and 10.18 s at 130 °C (P2), respectively. The calculation was performed according to literature and Equation 1 [27]. However, at higher temperatures also no crossover could be observed, which is also in line with findings for other

Development of N-F fluorinating agents and their fluorinations: Historical perspective

• Teruo Umemoto,
• Yuhao Yang and
• Gerald B. Hammond

Beilstein J. Org. Chem. 2021, 17, 1752–1813, doi:10.3762/bjoc.17.123

Synthesis of 1-indolyl-3,5,8-substituted γ-carbolines: one-pot solvent-free protocol and biological evaluation

• Premansh Dudhe,
• Mena Asha Krishnan,
• Kratika Yadav,
• Diptendu Roy,
• Krishnan Venkatasubbaiah,
• Biswarup Pathak and
• Venkatesh Chelvam

Beilstein J. Org. Chem. 2021, 17, 1453–1463, doi:10.3762/bjoc.17.101

• single-photon counting (TCSPC) experiments. The average fluorescence lifetime of compound 3ac was found to be 8.35 ns and 4.73 ns in DMSO and DCM, respectively (Table 2, Figure 4). Biological evaluation of γ-carbolines as anticancer agents A panel of carboline derivatives 3ac, 3bc, 3ca, and 3ga, along