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

• (λirr = 660 nm). The excited state dynamics of 18c was later studied in detail by Nagasawa and co-workers using femtosecond time-resolved transient absorption spectroscopy [44]. In 2022, Qiao and co-workers attempted to extend the thermal relaxation half-life of compound 18c by addition of cations such

• the Z-isomers in comparison with the E-forms [62]. In 2018, Nagasawa and co-workers provided a detailed investigation of the influence of solvent polarity and intermolecular hydrogen bonding on the photoisomerization of N,N'-diacetylindigo (9a) by transient absorption spectroscopy [63]. In principle

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

• potentials of the halides that can be reduced in this way, quantum-chemical calculations, and steady-state and transient absorption spectroscopy suggest that UV irradiation accelerates the reactions via cleavage of the dimers to the corresponding radical monomers. Keywords: dehalogenation; n-dopant

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

• obtained by transient absorption spectroscopy with femtosecond pulsed laser excitation and were 2–3 orders of magnitude greater (e.g., keT (*PC1•−) = 6.8 × 1010 s−1) than the diffusion rate in DMSO (kdiff = 4.0 × 108 s−1 of 0.12 M 1d) confirming a preassociation of PC1•− and the substrate prior to PET

• reducing enough to engage the model substrate perfluorooctyl iodide and instead *[FeII(btz)3]2+ was verified as the key catalytic species by transient absorption spectroscopy; even though the strongly reducing α-amino alkyl radical intermediate might also engage in the reduction of alkyl halides or act as

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

• states. Femtosecond transient absorption spectroscopy (fs-TA) was rarely used for the study of the photophysics of the TADF emitters [12][34][35][36][37], since it suffers from the limitation of the time window of detection (up to a few ns). On the other hand, nanosecond transient absorption spectroscopy

• were studied by steady state UV–vis absorption spectroscopy, transient photoluminescence spectroscopy, nanosecond/femtosecond transient absorption spectroscopy, electrochemistry, as well as DFT/TDDFT computations. We observed experimental evidence for the spin–vibronic coupling effect in the TADF

• internal reference. Femtosecond transient absorption spectroscopy Femtosecond transient absorption spectra (fs-TA) were acquired on a system based on a Ti:sapphire regenerative amplifier (Coherent Astrella). The system produces 40 fs pulses at 800 nm, with a repetition rate of 1 kHz. The instrument

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

• recorded with an Agilent 8453E UV–vis spectrophotometer (Agilent Technologies Inc., USA). Samples were deaerated with N2 for ca. 5 min before measurement and the N2 atmosphere was kept during the measurements. Nanosecond transient absorption spectroscopy The nanosecond transient absorption spectra were

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

• plunged at t = 1 min was used again at t = 5 min and t = 30 min in order to elucidate the structural evolution of the self-assembled crystals. Femtosecond transient absorption Femtosecond transient absorption spectroscopy was performed by a methodology analogous as described previously [36], using a

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• hydroxylation of arenes (Scheme 18) [157]. They realized that the photoredox catalyst 8 possesses a great oxidizing ability (Ered vs SCE = 2.72 V) at ambient conditions. The mechanism of the reaction was studied by fluorescence quenching and transient absorption spectroscopy. They observed that the one-electron

• observed that hydroxylation of the fluoro-, chloro-, and bromobenzene derivatives provided low yields. The photocatalytic mechanism for this reaction was inspected by time-resolved transient absorption spectroscopy to detect the triplet–triplet photoredox catalyst spectrum via nanosecond laser flash

• [163]. They exploited the potent photoredox catalyst 2 for the excitation of the substrate. The mechanism was detected by nanosecond transient absorption spectroscopy. The substrate scope and mechanism are shown in Scheme 22 and Figure 22. Furthermore, König and co-workers synthesized monochlorinated

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

• , Supporting Information File 1). Transient absorption spectroscopy To get more insights into the isomerization and fluorescence mechanism of 1, we measured transient absorption spectra of the molecule in different solvents. A fresh solution of the Z-form was excited using 400 nm light, and spectra were

• the excited state lifetime. Two-photon excitation Earlier experiments revealed that hydrazone 1 is able to isomerize also upon two-photon excitation [29]. In the present study we used transient absorption spectroscopy as an alternative method to determine the two-photon absorption cross section of the

• -state fluorescence of the E-isomers in most solvents. Transient absorption spectroscopy measurements, repeated in different solvents, allowed us to estimate the timescale of the Z/E isomerization process, which is about 0.5 ps in both toluene and acetonitrile, thus showing a negligible dependence on the

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• switching speed of PIC opened up various potential applications, no photosensitivity to visible light limits its applications. In this study, we synthesized a visible-light sensitized PIC derivative conjugated with a benzil unit. Femtosecond transient absorption spectroscopy revealed that the benzil unit

• ; sensitizer; transient absorption spectroscopy; Introduction Photochromism, which is defined as the reversible transformation of a chemical species between two structural isomers by light, has been extensively studied over decades [1][2][3][4]. Recently, visible-light sensitized photochromic materials have

• femtosecond transient absorption measurements using a 400 nm excitation pulse. The instrumental response function is ≈170 fs. It is noted that the excitation wavelength for femtosecond transient absorption spectroscopy (400 nm) is slightly different from that for nanosecond transient absorption spectroscopy

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

• (1,3,5-TMB•+) is formed indeed during the quenching process of the catalyst by 1,3,5-TMB (Scheme 5) ns-time-resolved transient absorption spectroscopy was used [50]. To allow for a decomposition of the multicomponent spectra we conducted laser flash photolysis (LFP) experiments on the single components

Photocatalytic formation of carbon–sulfur bonds

• Alexander Wimmer and
• Burkhard König

Beilstein J. Org. Chem. 2018, 14, 54–83, doi:10.3762/bjoc.14.4

• from alkyl and aryl thiosulfates and aryl diazonium salts (Scheme 39) [74]. They confirmed by transient absorption spectroscopy that a single-electron transfer occurs between [Ru(bpy)3]Cl2 and the aryl diazonium salt. Additionally, electron paramagnetic resonance studies showed that K2CO3 interacts

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• the electronic ground state, whereas the emission of the donor moieties is efficiently quenched according to static fluorescence spectroscopy. The observed peculiar fluorescence quenching was previously studied by femtosecond transient absorption spectroscopy of a related model dyad indicating a photo

• anthraquinone-substituted aldehyde together with acetic acid and tert-butyl isocyanide for rapidly assembling a donor–acceptor conjugate 1 displaying a photo-induced electron transfer leading to a charge-separated state with a lifetime of >2 ns (Figure 1), as elucidated by femtosecond transient absorption

• spectroscopy [56]. The donor-only (2) and acceptor-only (3) models for spectroscopic comparison were obtained analogously. For enabling rapid accesses to functional π-systems, such as Do–Acc dyads for photo-induced charge separation, besides a robust, flexible diversity-oriented one-pot reaction, such as the

On the mechanism of photocatalytic reactions with eosin Y

• Michal Majek,
• Fabiana Filace and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97

• possible without further spectroscopic, kinetic, and theoretical experiments. The studied systems are mostly too complex for transient absorption spectroscopy. We have so far failed to obtain any insight from photo-CIDNP NMR experiments. Therefore, we have decided to evaluate the efficiency of the