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

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

• . This suggests that exciplexes ([(F12SubPc–TCBD)δ−–anilineδ+]*) are generated where the negative charge is delocalized over F12SubPc and TCBD. The radiative exciplex formation was also confirmed by time-resolved fluorescence measurements. In fact, in toluene, 60 showed maximum emission at 675 nm and a

• benzonitrile, the formation of an exciplex was not observed and it was considered that the CS state ((F12SubPc–TCBD)•−–aniline•+) was formed from the singlet excited state of F12SubPc before returning to the singlet ground state. The aforementioned phenomenon, characterized by the switch in the exciplex or the

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

• at 440 nm [64], TCTA at 410 nm [65], and TPBi at 390 nm [66]) and at longer wavelengths due to the excimer/exciplex emissions at the interfaces of NPB-TCTA/EML and EML/TPBi were observed, signifying that the OLED possessed a well-balanced electron and hole transport. Moreover, due to the efficient

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

• the pyrene unit as well as combinations of pyrene with other aromatic fluorophores could improve the properties [7]. Recently, Takaishi et al. reported chiral exciplex dyes having pyrenyl, perylenyl, and 4-(dimethylamino)phenyl groups incorporated in their structure, which showed circularly polarized

• luminescence (CPL). The exciplex (excited heterodimer) formed intramolecularly proved to be conformationally rigid and consequently was not sensitive to solvent or temperature [8]. Further, pyrenoimidazole-fused phenanthridines have been reported recently, developed as fluorescence emitters for optoelectronic

• applications [9]. These compounds have a very large aromatic surface suitable to form self-assembled supramolecular structures by intermolecular π–π interactions and showed excimer fluorescence in thin film and in the solid state. Kawai et al. reported exciplex formation between pyrene and guanine in polar

Microelectrode arrays, electrosynthesis, and the optimization of signaling on an inert, stable surface

• Kendra Drayton-White,
• Siyue Liu,
• Yu-Chia Chang,
• Sakashi Uppal and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2022, 18, 1488–1498, doi:10.3762/bjoc.18.156

• pyrene to form the exciplex dimer that fluoresces in the red region of the spectrum and does not self-quench. A fluorescence microscope was then used to take an image of the array, and the image used to quantify the fluorescence, and thereby the amount of material present, at each region of the array

Post-synthesis from Lewis acid–base interaction: an alternative way to generate light and harvest triplet excitons

• Hengjia Liu and
• Guohua Xie

Beilstein J. Org. Chem. 2022, 18, 825–836, doi:10.3762/bjoc.18.83

• multiple molecules [13]. The exciplex contains new excited states through charge transfer between a donor molecule and an acceptor molecule. This provides a simple way to create new luminescence processes through the intermolecular interactions of existing molecules [14]. It has been reported that new

• (C6F5)3 (BCF) to bind to nitrogen atoms at the basic site a of π-conjugated polymer, providing a simple strategy to regulate the optical properties of the A–D–A chromophore with charge transfer excited state properties [28]. In 2019, Wang et al. constructed a novel exciplex system by using the Lewis

• intermolecular charge transfer. Compared with B(C6H5)3, the exciplex system constructed by BCF exhibited a more pronounced red-shift in the PL spectra and unexpectedly improved EL properties. The fluorescent materials, which can easily interact with Lewis acids and simultaneously exhibit significant chemical and

Metal-free synthesis of biarenes via photoextrusion in di(tri)aryl phosphates

• Hisham Qrareya,
• Lorenzo Meazza,
• Stefano Protti and
• Maurizio Fagnoni

Beilstein J. Org. Chem. 2020, 16, 3008–3014, doi:10.3762/bjoc.16.250

• synthesis of biarenes has been developed. The approach is based on the photoextrusion of a phosphate moiety occurring upon irradiation of biaryl- and triaryl phosphates. The reaction involves an exciplex as the intermediate and it is especially suitable for the preparation of electron-rich biarenes

• results and of the reported literature [58][61], to the singlet monomeric excited state and to the exciplex, respectively. While aryl phosphates have been only sparsely used as substrates in thermal cross-coupling reactions [65][66][67], their photochemical behavior has been the subject of various

• is present in the phosphates since none of the above-mentioned processes took place. In fact, our investigations, in according with early works [52][71], suggested that both diaryl and triaryl phosphates are prone to generate an intramolecular exciplex 5* under irradiation (Scheme 3, path (a)), on

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• , internal conversion, intermolecular electron transfer, as well as excimer or exciplex formation and isomerization. These phenomena significantly limit the usability of luminogens for the abovementioned purposes. Several attempts were already made to prevent or restrict these non-radiative pathways by

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• ) calculations [199]. They were able to experimentally demonstrate, for the first time, that the reaction between photoexcited AQN and Selectfluor® afforded a transient AQN–Selectfluor® triplet exciplex species by calculating the predicted TDDFT absorption spectrum that matched with the experimentally obtained

• spontaneous intramolecular reorganization process affords the AQN–Selectfluor® exciplex Int1. The AQN–Selectfluor® exciplex Int 1 possesses a longer N–F bond distance (1.98 Å) compared to the N–F bond distance (1.37 Å) of Selectfluor® (Scheme 17). This indicates that the fluorine atom in the exciplex is

• stabilized by the aromatic system of AQN and that the N–F bond becomes more labile. In this exciplex, the spin density is delocalized mostly over the AQN–F moiety (61%), and the absorption band depends mainly on the AQN–F interactions. Thus, the authors concluded that the TA spectra should not depend on the

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

Synthesis and properties of quinazoline-based versatile exciplex-forming compounds

• Rasa Keruckiene,
• Simona Vekteryte,
• Ervinas Urbonas,
• Matas Guzauskas,
• Eigirdas Skuodis,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 1142–1153, doi:10.3762/bjoc.16.101

• of the derivatives were in the range of 5.22–5.87 eV. The 3,6-di-tert-butylcarbazole-substituted quinazoline-based compound forms a sky-blue emitting exciplex in solid mixture with the acceptor 2,4,6-tris[3-(diphenylphosphinyl)phenyl]-1,3,5-triazine as well as an orange emitting exciplex with the

• donor 4,4′,4″-tris[3-methylphenyl(phenyl)amino]triphenylamine. A white OLED based on these versatile exciplex systems with a relatively high maximum brightness of 3030 cd/m2 and an external quantum efficiency of 0.5% was fabricated. Keywords: carbazole; dimethyldihydroacridine; exciplex; phenothiazine

• OLEDs could be obtained with easy modulation of the electroluminescent properties. Recently, the first examples of versatile exciplex-forming materials which can form two different types of exciplexes, donor–acceptor/donor and acceptor/donor–acceptor, were reported for simplified non-doped white OLEDs

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• /70s, and Lewis identified exciplex states as key intermediates [13][14]. The corresponding photohydration worked only if the aromatic olefins as starting material were directly excited by UV light [15][16]. The first approach towards a photocatalytic version of this type of reaction came from Arnold

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

• Dae Won Cho,
• Patrick S. Mariano and
• Ung Chan Yoon

Beilstein J. Org. Chem. 2014, 10, 514–527, doi:10.3762/bjoc.10.47

• results in a close facial approach of the benzamide aromatic rings in 60, which results in intramolecular exciplex formation (Scheme 16). Conclusion Direct and indirect approaches, which rely on the use of SET-promoted photocyclization reactions of α-silyl ether-terminated, polydonor-linked, imides (e.g

• . Photoreactions of bis-donor-linked bisphthalimides. Indirect approach to the preparation of lariat-type crown ethers. SET-based fluorescence sensing modes according to guest binding. Enhancement of the exciplex formation and fluorescence of bis-crown ether 60 with a Mg2+ sandwich-type binding. Acknowledgements

Electron and hydrogen self-exchange of free radicals of sterically hindered tertiary aliphatic amines investigated by photo-CIDNP

• Martin Goez,
• Isabell Frisch and
• Ingo Sartorius

Beilstein J. Org. Chem. 2013, 9, 437–446, doi:10.3762/bjoc.9.46

• varying involvement of polar intermediates. Often, they are true two-step processes with an initial full charge transfer to give a radical ion pair, which then undergoes a proton transfer [1][2][3][4][5][6][7]; partial charge transfer (i.e., formation of an exciplex) as the first step has also been

Diarylethene-modified nucleotides for switching optical properties in DNA

• Sebastian Barrois and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2012, 8, 905–914, doi:10.3762/bjoc.8.103

• chromophores to oligonucleotides offers potentially interesting optical characteristics, among these being solvatochromism and red-shifted exciplex-type fluorescence [38]. Such absorption and fluorescence readouts are potentially suitable for DNA probing [39][40][41]. On the other hand, with respect to

The arene–alkene photocycloaddition

• Ursula Streit and
• Christian G. Bochet

Beilstein J. Org. Chem. 2011, 7, 525–542, doi:10.3762/bjoc.7.61

• of mechanistic suggestions and debates up to that date. The now commonly accepted mechanism of this reaction involves the excitation of the benzene moiety to its first excited-state (1B2u) and subsequent formation of an exciplex with the alkene moiety (Scheme 5). The occurrence of such exciplexes has

• been detected by emission spectroscopy [22][27]. The two new sigma C–C bonds are formed concertedly from the exciplex. The reaction is thought to proceed through a slightly polarized intermediate, which explains the observed regioselectivity when the arene is disymmetrically substituted. While the

• to the regioselectivity. The addition can either occur from the exo or endo exciplex to the aromatic moiety (Scheme 9). The observed preference for endo photocycloaddition [34][35][36] has been rationalized by secondary orbital overlap, which supports attack on the olefin from the endo position [37

Fluorometric recognition of both dihydrogen phosphate and iodide by a new flexible anthracene linked benzimidazolium-based receptor

• Kumaresh Ghosh and
• Debasis Kar

Beilstein J. Org. Chem. 2011, 7, 254–264, doi:10.3762/bjoc.7.34

• tetrabutylammonium salts of H2PO4−, F−, Br− and I−, the emission of 1 was quenched by 72, 18, 14 and 30%, respectively. During titration experiments, no other changes such as excimer or exciplex formation were observed. The large quenching in emission of 1 upon increasing H2PO4− concentration is illustrated in

Anthracene appended pyridinium amide–urea conjugate in selective fluorometric sensing of L-N-acetylvaline salt

• Kumaresh Ghosh,
• Tanmay Sarkar and
• Asoke P. Chattopadhyay

Beilstein J. Org. Chem. 2010, 6, 1211–1218, doi:10.3762/bjoc.6.139

• exciplex or charge transfer complex in CH3CN is the key feature in the present study for the selective detection of a L-N-acetylvaline salt from other anionic guests. To explain the formation of an exciplex or charge transfer complex in 1 upon complexation of L-N-acetylvaline salt, compound 2 was

Anthracene coupled adenine for the selective sensing of copper ions

• Kumaresh Ghosh and
• Tanushree Sen

Beilstein J. Org. Chem. 2010, 6, No. 44, doi:10.3762/bjoc.6.44

• between Cu2+ ion and the other metal ions investigated. During interaction of 1 with metal ions no additional peak at higher wavelengths either for excimer or exciplex formation should be observed. Figure 4 shows the spectral change of 1 upon titration with Cu2+ metal ions. A similar trend in emission