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

• transformation from a conceptual standpoint. Another fundamental law in photochemistry is the Beer–Lambert law, which describes a negative exponential correlation between the transmittance of a solution containing chromophores (i.e., a light-absorbing species) and the optical path length (Figure 1). In essence

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

Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety

• Anastasia I. Ershova,
• Sergey V. Fedoseev,
• Konstantin V. Lipin,
• Mikhail Yu. Ievlev,
• Oleg E. Nasakin and
• Oleg V. Ershov

Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251

• chemistry. This type of chromophores is of particular interest in the fields of organic electronics, photonics, and optoelectronics due to their unique optical and electronic properties [1][2][3][4][5][6][7][8][9][10][11][12][13]. Among heteroaromatic push–pull molecules, stilbazole derivatives

• and acceptor groups arranged in a specific sequence, such as in D–π–A chromophores. This creates the conditions for efficient intramolecular charge transfer (ICT), which plays a key role in the DSE phenomenon. Also, additional substituents can affect the geometry and conformation of the molecule

Synthesis and reactivity of the di(9-anthryl)methyl radical

• Tomohiko Nishiuchi,
• Kazuma Takahashi,
• Yuta Makihara and
• Takashi Kubo

Beilstein J. Org. Chem. 2024, 20, 2254–2260, doi:10.3762/bjoc.20.193

• . Keywords: anthracene; cation; dimerization; radical; reactivity; Introduction Organic radicals have garnered significant attention in various research fields, including catalysis [1][2][3][4], chromophores [5][6][7][8], and as agents in dynamic nuclear polarization [9][10][11][12]. Recently, highly stable

Metal-free double azide addition to strained alkynes of an octadehydrodibenzo[12]annulene derivative with electron-withdrawing substituents

• Naoki Takeda,
• Shuichi Akasaka,
• Susumu Kawauchi and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2024, 20, 2234–2241, doi:10.3762/bjoc.20.191

• ] cycloaddition–retroelectrocyclization (CA-RE) between electron-rich alkynes and electron-deficient olefins [8]. The [2 + 2] CA-RE click reactions were employed to produce a variety of functional materials, such as nonlinear optical chromophores [9][10], super acceptors [11][12], ion sensing D–A systems [13

Understanding X-ray-induced isomerisation in photoswitchable surfactant assemblies

• Beatrice E. Jones,
• Camille Blayo,
• Jake L. Greenfield,
• Matthew J. Fuchter,
• Nathan Cowieson and
• Rachel C. Evans

Beilstein J. Org. Chem. 2024, 20, 2005–2015, doi:10.3762/bjoc.20.176

• spatiotemporal control. To build responsive materials, surfactants are particularly attractive due to their ability to self-assemble into different morphologies depending on their molecular structure and chemical environment. To that end, photoswitchable chromophores can be incorporated into amphiphilic

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

• classes have been investigated, including second-generation cyanoarenes [8], arylamines [26], phenothiazines, phenazines and phenoxazines [9][27][28], which can act as excited state reductants comparable to precious metal-based photoredox catalysts. Singlet-excited organic chromophores often have short

• -component reactions (3-CRs) and it has been shown that substituting the helicene core with functional groups is a viable approach to fine-tune the photochemical properties [45][46], as has been demonstrated for other organic and metal-based chromophores. Our study focused on investigating the reaction

• chromophores (as listed above). Results and Discussion A thorough understanding of the operation principles of a photocatalyst is essential for the development of improved catalysts and efficient photoreactions. To this end, the photochemical properties of photocatalysts such as metal complexes and organic

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

• a closed “U”-shaped conformation. This type of switch was first described with the molecular tweezers 7 bearing two pyrene chromophores on the position 6 and 6” of the terpyridine, resulting in an open “W” conformation [33][34]. In this state, the system exhibits luminescence properties that are

• quenched when the tweezers are closed by the addition of a Zn2+ cation because of intramolecular π–π stacking interactions between the chromophores. The system can be reopened and its luminescence properties restored by introducing tris(2-aminoethyl)amine (TREN), which has a better affinity for Zn2+ and

• ligands. This strategy led to elaborated dissymmetric systems that have been used as switchable chromophores [87] and in counterion-controlled phase-transfer processes [88]. To summarize, coordination-responsive molecular tweezers have been developed using a variety of switching units with a predominance

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

• structures connected by an ethylene bridge, and the electronic transition responsible for the color takes place within this structural element of the indigo molecule (Figure 4). To emphasize the special nature of the indigo-type systems, Klessinger and Lüttke proposed to call their chromophores “H

• -chromophores” after the shape of the main structural fragment resembling the Latin letter “H” (Figure 4) [19]. The small HOMO–LUMO gap and, thus, the long-wavelength absorption are responsible for the purple color of indigo in vapors, which changes into deep blue color in the crystalline state due to formation

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

• Michio Yamada Department of Chemistry, Tokyo Gakugei University, Nukuikitamachi 4-1-1, Koganei, Tokyo 184-8501, Japan 10.3762/bjoc.20.13 Abstract Various push–pull chromophores can be synthesized in a single and atom-economical step through [2 + 2] cycloaddition–retroelectrocyclization (CA–RE

• ) reactions involving diverse electron-rich alkynes and electron-deficient alkenes. In this review, a comprehensive investigation of the recent and noteworthy advancements in the research on push–pull chromophores prepared via the [2 + 2] CA–RE reaction is conducted. In particular, an overview of the

• chromophores, wherein both electron-donating and electron-accepting substituents are incorporated into a π-electron-conjugated system, exhibit exceptional optical and electronic properties. They hold significant promise for applications in diverse fields, particularly materials science (specifically in

Multi-redox indenofluorene chromophores incorporating dithiafulvene donor and ene/enediyne acceptor units

• Christina Schøttler,
• Kasper Lund-Rasmussen,
• Line Broløs,
• Philip Vinterberg,
• Ema Bazikova,
• Viktor B. R. Pedersen and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2024, 20, 59–73, doi:10.3762/bjoc.20.8

• a subsequent Glaser–Hay coupling reaction, a RA acceptor unit was introduced to provide a DTF-IF-RA donor–acceptor scaffold with a low-energy charge-transfer absorption and multi-redox behavior. Keywords: alkynes; chromophores; fused-ring systems; heterocycles; redox chemistry; Introduction

• pyrrole unit to one of the dithiole rings of an IF-TTF, allowing for dimerization of extended TTFs via the nitrogen atom by different linkers [14]. Donor–acceptor chromophores can be obtained by replacing one of the dithiafulvene (DTF) rings of the IF-TTF by an electron acceptor. Cyclic and acyclic

• ) expanding to ca. 680 nm. UV–vis absorption spectra of compounds 22, 23, 26, and 27 are depicted in Figure 5. By comparing donor–acceptor chromophores 22 and 23, it is observed that the RA moiety of DTF-IF-RA scaffold 23 induces a significant redshift, presumably due to the stronger electron-accepting

Quinoxaline derivatives as attractive electron-transporting materials

• Zeeshan Abid,
• Liaqat Ali,
• Sughra Gulzar,
• Faiza Wahad,
• Raja Shahid Ashraf and
• Christian B. Nielsen

Beilstein J. Org. Chem. 2023, 19, 1694–1712, doi:10.3762/bjoc.19.124

• devices is discussed in detail. Additionally, their significance as thermally activated delayed fluorescence emitters and chromophores for OLEDs, sensors and electrochromic devices is explored. The review emphasizes the remarkable characteristics and versatility of quinoxaline derivatives in electron

• chromophores in the development of organic light-emitting diodes (OLEDs), sensors, and electrochromic devices [8][13][14]. In this review, we have comprehensively examined the recent advancements of Qx-derived ETMs in various applications within the organic semiconductor device field over the past five to six

• shows the prominent examples of recently reported Qx based dyes and TDAF emitters. Table 5 lists device properties and relevant information of devices employing Qx derivatives. Quinoxalines as chromophores Qx derivatives have emerged as promising chromophores due to their distinctive optical and

A deep-red fluorophore based on naphthothiadiazole as emitter with hybridized local and charge transfer and ambipolar transporting properties for electroluminescent devices

• Suangsiri Arunlimsawat,
• Patteera Funchien,
• Pongsakorn Chasing,
• Atthapon Saenubol,
• Taweesak Sudyoadsuk and
• Vinich Promarak

Beilstein J. Org. Chem. 2023, 19, 1664–1676, doi:10.3762/bjoc.19.122

• [11], laser dyes [12], and DR/NIR electroluminescent devices [13][14][15][16][17][18]. However, DR/NIR chromophores typically suffer from low photoluminescent quantum yields (PLQY) because of their intrinsic small band-gap energy causing larger vibronic coupling between the ground and excited states

Tying a knot between crown ethers and porphyrins

• Maksym Matviyishyn and
• Bartosz Szyszko

Beilstein J. Org. Chem. 2023, 19, 1630–1650, doi:10.3762/bjoc.19.120

• incorporated four pyrrole rings functionalised at their β positions with 18-crown-6 pockets. The research sparked interest in crown ether-annulated porphyrins to be used as potential multitopic chromophores, with the conjoined porphyrin and crown ether frameworks for electron transfer systems [51]. Regardless

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

• chromophores, which are coupled through a Buchwald–Hartwig coupling reaction (another NI-PTZ paper) [39]. The oxidation of the PTZ unit was readily performed by treatment with H2O2 as oxidant (Scheme 1). All compounds were obtained with satisfactory yields and the molecular structures were fully characterized

Synthesis, structure, and properties of switchable cross-conjugated 1,4-diaryl-1,3-butadiynes based on 1,8-bis(dimethylamino)naphthalene

• Semyon V. Tsybulin,
• Ekaterina A. Filatova,
• Alexander F. Pozharskii,
• Valery A. Ozeryanskii and
• Anna V. Gulevskaya

Beilstein J. Org. Chem. 2023, 19, 674–686, doi:10.3762/bjoc.19.49

• us to undertake the current study. X-ray crystallography, UV–vis spectroscopy and cyclic voltammetry were applied to analyze the extent of π-electron conjugation and the efficiency of the particular donor–acceptor conjugation path in chromophores 5. Results and Discussion Synthesis The target

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

• RNA, single or double-stranded polynucleotides, particular base composition…) and signalize binding by specific spectroscopic response is of great importance [1][2]. Pyrene derivatives are among the earliest known fluorescent probes for biomolecules. These chromophores are often used due to their high

• emission change upon binding to proteins, and a cyanine fluorescence that was selective for polynucleotides. Moreover, the FRET pair of chromophores was activated upon binding to biomolecules [18]. Continuing our previous work, two phenanthridine–pyrene conjugates Phen-Py-1 and Phen-Py-2 (Scheme 1

• chromophores enabled intramolecular contacts between the phenanthridine and pyrene chromophore. This stacking interaction minimized the surface area that was exposed to water. As a result, mutual shielding of chromophores and coulombic interaction between induced dipoles could cause hypochromism and consequent

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

• -dipolar cycloaddition reaction between an azide and a terminal alkyne, also popular as "click reaction" or CuAAC reaction. Moreover, the 1,2,3-triazole ring also serves as a spacer and an electron transfer bridge between the porphyrin and the attached chromophores. In order to provide a critical overview

• relatively inefficient quenching of the ZnP singlet excited state, slow charge separation, and fast charge recombination processes on the visible excitation of ZnP and UV excitation of NDI chromophores. On the other hand, excitation of the NDI chromophore leads to the charge separation via both singlet and

• . The CuAAC click reaction has been shown to bind a variety of chromophores bearing azide or alkyne groups to the porphyrin periphery, including coumarin, xanthone, DNA, ferrocene, corrole, fluorescein, carborane, BODIPY, graphene, carboline, fullerene, NDI, β-cyclodextrin, cholic acid, quinolone, etc

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

• originating from the peri-H atoms on the two chromophores. We also tuned the redox potentials by oxidation of the electron donor PTZ (NI-PTZ-O). Thus, the energy of CT states and the matching with their 3LE counterpart can be altered. We underline that the approach of oxidation of the PTZ unit, which has

• . The synthesis of the dyads is based on the ordinary derivatization of the NI and PTZ chromophores [20]. The molecular structures were confirmed by 1H NMR, 13C NMR, and HRMS methods (Experimental section). UV–vis absorption and fluorescence emission spectra The UV–vis absorption spectra of the

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

• in designing heteroatom-containing (N, O, S, etc.) chromophores [26]. The lone-pair electrons of heteroatoms can possess a certain degree of basicity, which results in sensitivity to acid. Consequently, the lone pair may be protonated and deprotonated by consecutively adding acid and base. The

Substituent effect on TADF properties of 2-modified 4,6-bis(3,6-di-tert-butyl-9-carbazolyl)-5-methylpyrimidines

• Irina Fiodorova,
• Tomas Serevičius,
• Rokas Skaisgiris,
• Saulius Juršėnas and
• Sigitas Tumkevicius

Beilstein J. Org. Chem. 2022, 18, 497–507, doi:10.3762/bjoc.18.52

• confirm the structures of the synthesized compounds (see Figures S1–S27 in Supporting Information File 1). DFT analysis To assess the structural and electronic properties of the chromophores tCbz-mPYR and 1–6, quantum chemical calculations were performed. DFT analysis revealed that all studied compounds

• the similar molecular structures, the studied chromophores showed somewhat different electronic properties, mainly due to the variation of the acceptor structure. The DFT computed spatial distribution of frontier molecular orbitals (FMOs) of compounds tCbz-mPYR and 1–6 is presented in Figure 2. A

Synthesis of a novel aminobenzene-containing hemicucurbituril and its fluorescence spectral properties with ions

• Qingkai Zeng,
• Qiumeng Long,
• Jihong Lu,
• Li Wang,
• Yuting You,
• Xiaoting Yuan,
• Qianjun Zhang,
• Qingmei Ge,
• Hang Cong and
• Mao Liu

Beilstein J. Org. Chem. 2021, 17, 2840–2847, doi:10.3762/bjoc.17.195

• domains, such as chemosensors [21], drug delivery [22], and nano materials preparation [23]. Although cucurbiturils with their rigid hydrophobic cavities have found broad application in host–guest chemistry, they suffer from insolubility, difficulty in derivatization, and lack of chromophores

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

• velocity, and the quantum yield. Therefore, a new criterion needs to be investigated for the physical parameters of these specific reactions. 2) We also need to develop novel macrocycles with chromophores. Most of the current macrocycles only provide the suitable cavities for the reactions, however, if a

• macrocycle has inherent chromophores that can function as photosensitizers, the efficiency of the energy transfer will be higher and the systems will be simplified. 3) Other kinds of macrocycle-based catalysis need to be explored, such as esterification, polymerization, redox reaction, etc. 4) Hyperbranched

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• to an n-alkyl chain at the other, underwent self-assembly in aqueous media depending on the length of the alkyl segment. The amphiphilic derivatives having n-decyl or longer chains, formed nano-assemblies with cyanic–green emission resulting from the stacked pyrene chromophores in the aggregates. The

• vibronic bands at 343–345 nm and 327–329 nm, respectively) generally indicates a possible mode of organization of the pyrene chromophores upon self-assembly [63]. It was found that in the concentration range of 5–50 µM [65], although a decrease in this ratio was observed for PBIm4; much more pronounced

• and in the aggregates, the pyrene chromophores had ground state interactions and were possibly stacked in co-facial manner as found in H-aggregates [63]. The aggregate formation was further supported by FESEM images (Figure 3a and Supporting Information File 1, Figure S7) which revealed the formation

Formation of an exceptionally stable ketene during phototransformations of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores

• Asitanga Ghosh

Beilstein J. Org. Chem. 2020, 16, 2297–2303, doi:10.3762/bjoc.16.190

• Asitanga Ghosh Deptartment of Chemistry, Hooghly Mohsin College, Chinsurah, Hooghly, West Bengal, 712101, India 10.3762/bjoc.16.190 Abstract Photochemical reactions of bicyclo[2.2.2]oct-5-en-2-ones having mixed chromophores like a 5,6 dibenzoyl moiety and bulky electron-deficient substituents

• position; ketene; mixed chromophores; Introduction Enones exhibit a rich and diverse photochemistry. The deep-seated photochemical rearrangements found in these systems have attracted numerous mechanistic studies. In this context, the photochemistry of α,β-enones A and β,γ-enones B (Figure 1) has become

• near 350 nm (log ε ≈ 2.0). Probably this is due to interactions of these two chromophores [7]. In many cases probable unselective populations of the excited states owing to the presence of these two individual chromophores are expected to give rise to different photoproduct(s) and in some cases