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

• not change the absorption significantly, compared to compound 11. When changing the solvent from PhMe to CH2Cl2, we observed a redshift of the longest-wavelength absorption maximum for compounds 10 and 11, indicating some charge-transfer character of the absorption (see Figure S1 in Supporting

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

• to lie lower in energy than the S0→S1 transition of (Cyc-DMBI)2 and presumably corresponds to the shoulder observed in the experimental spectrum of (N-DMBI)2, and S0→S5, which lies very close to S0→S6. For both of these transitions, the NTOs indicate considerable charge transfer from the

Anion–π catalysis on carbon allotropes

• M. Ángeles Gutiérrez López,
• Mei-Ling Tan,
• Giacomo Renno,
• Augustina Jozeliūnaitė,
• J. Jonathan Nué-Martinez,
• Javier Lopez-Andarias,
• Naomi Sakai and
• Stefan Matile

Beilstein J. Org. Chem. 2023, 19, 1881–1894, doi:10.3762/bjoc.19.140

• as with substrate 68. This result was consistent with pyrene as best interfacers for MWCNTs. For anion–π catalysis on NDI stacks, the reversed order was obtained, consistent with the preferred formation of DAN-NDI charge transfer complexes [8][100][101][102][103][104][105][106]. The efficient

Aromatic systems with two and three pyridine-2,6-dicarbazolyl-3,5-dicarbonitrile fragments as electron-transporting organic semiconductors exhibiting long-lived emissions

• Karolis Leitonas,
• Brigita Vigante,
• Dmytro Volyniuk,
• Audrius Bucinskas,
• Pavels Dimitrijevs,
• Sindija Lapcinska,
• Pavel Arsenyan and
• Juozas Vidas Grazulevicius

Beilstein J. Org. Chem. 2023, 19, 1867–1880, doi:10.3762/bjoc.19.139

• -dicarbazolyl-3,5-dicarbonitrile. The compounds are synthesized by Sonogashira coupling reactions and characterized by steady-state and time-resolved luminescence spectroscopy. The compounds show efficient intramolecular charge transfer (ICT) from the donor to the acceptor. The photoluminescence (PL) spectra of

• compounds. In general, polyaromatic π-systems with pyridine-3,5-dicarbonitrile fragments demonstrate promising potential for use in organic electronic devices, such as OLEDs. Keywords: charge transport; intramolecular charge transfer; photophysical properties; pyridine-3,5-dicarbonitrile; Introduction The

• peaks of these low-energy absorption bands are collected in Table 1. A similar band was previously observed for REF [5]. On the basis of the results of the theoretical investigations, the low-energy absorption band of REF has been attributed to the intramolecular charge transfer (ICT) caused by electron

Recent advancements in iodide/phosphine-mediated photoredox radical reactions

• Tinglan Liu,
• Yu Zhou,
• Junhong Tang and
• Chengming Wang

Beilstein J. Org. Chem. 2023, 19, 1785–1803, doi:10.3762/bjoc.19.131

• ], it was proposed that the decarboxylative cascade cyclization reaction proceeded through the formation of a charge-transfer complex (CTC) II involving PPh3, NaI, and NHP ester 3 (Scheme 20). Upon photofragmentation of the CTC complex II, two important intermediates were generated: an alkyl radical A

Active-metal template clipping synthesis of novel [2]rotaxanes

• Cătălin C. Anghel,
• Teodor A. Cucuiet,
• Niculina D. Hădade and
• Ion Grosu

Beilstein J. Org. Chem. 2023, 19, 1776–1784, doi:10.3762/bjoc.19.130

• ) [30][31], metal-ion template (coordination bonds [22][32], ion-dipol [16], donor–acceptor (charge transfer, π–π stacking) [30][33], and oligoamide macrocycle-hydrogen acceptors (hydrogen bonding) [20][34]. In active-metal template methods (Figure 1) the metal ion acts both as template and catalyst for

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

• high electron mobility and efficient charge transfer. In particular, Qx derivatives find use as non-fullerene acceptors (NFAs) in OSCs and as essential building blocks in sensitizers for DSSCs. The significance of Qx extends beyond to thermally activated delayed fluorescence (TADF) emitters and

• ). The charge transfer efficiency and device performance of Qx33 was improved by aligning its LUMO energy level with the conduction band edge of the TiO2 nanoparticles. This strategic approach highlights the importance of optimizing energy level alignment for efficient charge transport in DSSCs [40

• importance of specific substitutions. While Qx44b demonstrated favorable properties such as a superior dipole moment, narrow bandgap, and red-shifted absorption, the reduced charge transfer rate presented a challenge. This analysis emphasizes the need for a delicate balance between desirable electronic

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

• aggregation-induced emission (AIE) luminogen. The experimental (solvatochromic and emission in THF/water mixtures studies) and theoretical investigations prove that TPECNz retains cooperative hybridized local and charge transfer (HLCT) and weak AIE features. Thanks to its D–A–D-type structure with a proper

• coordinates of (0.664, 0.335)), an EQEmax of 3.32% and exciton utilization efficiency (EUE) of 47%. Keywords: ambipolar material; deep red fluorophore; hybridized local and charge transfer; naphthothiadiazole; OLED; organic light-emitting diode; Introduction Recently, organic fluorophores with efficient

• charge-transport properties, which could be done by selecting different D and A moieties [22][26][27][28]. In these fluorophores, the emission generally derives from intramolecular charge-transfer (CT) states at lower energy. Nonetheless, the formed CT state between D and A in such materials normally

Complexes of resorcin[4]arene with secondary amines: synthesis, solvent influence on “in-out” structure, and theoretical calculations of non-covalent interactions

• Waldemar Iwanek

Beilstein J. Org. Chem. 2023, 19, 1525–1536, doi:10.3762/bjoc.19.109

• studied complexes, categorized as electrostatic, exchangeable, dispersion, and charge-transfer interactions. From the data presented in Table 2, it is evident that electrostatic interactions in the form of hydrogen bonds primarily contribute to the formation of R[4]:sec-amine complexes with a 1:1

• the non-covalent interactions stabilizing the formation of 1:1 stoichiometry complexes was noted for the charge-transfer interactions. They are only slightly higher in CHCl3 than in DMSO, ranging from 1.4 to 2.9%. In general, it can be concluded from these calculations that the reduction of

• individual types of NCI in DMSO are as follows: approx. 88% electrostatic, 7% exchangeable, 3.6% dispersion, and 1.5% charge transfer. It is noteworthy that despite the presence of relatively large aliphatic chains in these amine molecules, electrostatic interactions strongly dominate in these complexes

Visible-light-induced nickel-catalyzed α-hydroxytrifluoroethylation of alkyl carboxylic acids: Access to trifluoromethyl alkyl acyloins

• Feng Chen,
• Xiu-Hua Xu,
• Zeng-Hao Chen,
• Yue Chen and
• Feng-Ling Qing

Beilstein J. Org. Chem. 2023, 19, 1372–1378, doi:10.3762/bjoc.19.98

• light-induced charge transfer event to give trifluoroethoxyl radical B, followed by a 1,2-hydrogen atom transfer (HAT), producing the stable radical C. For the nickel cycle, it is initiated by oxidative addition of Ni(0) catalyst E to acyl electrophile D formed in situ from carboxylic acid 1 with

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

• vibronically resolved carbazole absorption peaks which are commonly present at 325 nm [15]. Similar to 4CzIPN [14][15], the UV–vis profile has two broad regions: localized charge transfer (loCT) over 320–380 nm region with ε up to 14000 M−1 cm−1 and a delocalized charge transfer (deCT) broad shoulder over the

• to 60 K. However, only marginal increase of lifetime measured in the range of 60 to 16 K indicating a phosphorescence PL nature below 60 K. The charge transfer singlet (1CT) and local excited singlet (1LE), triplet (3LE) state energies were estimated from the onset values of the blue emission edge of

Radical ligand transfer: a general strategy for radical functionalization

• David T. Nemoto Jr,
• Kang-Jie Bian,
• Shih-Chieh Kao and
• Julian G. West

Beilstein J. Org. Chem. 2023, 19, 1225–1233, doi:10.3762/bjoc.19.90

• charge transfer (LMCT) which, following cage escape, could add to the alkene to generate an alkyl radical. This alkyl radical could then be chlorinated via RLT from a second Cu(II) chloride species, furnishing the dichlorinated product. While copper was unable to be used catalytically in this early

• with different elementary steps, including hydrogen atom transfer (HAT) and ligand-to-metal charge transfer (LMCT), enabling new transformations to be unlocked with unprecedented modularity. Further, the privileged position of earth abundant elements such as iron and manganese in RLT has made reactions

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

• oxidation products are positively charged. This will stabilize the charge-transfer complex formed during quenching and combined with fast electron transfer will likely increase the rate of recombination and decrease their effectiveness as donors. The oxidation potentials of the viologens (Figure 4) are

• during carbon dioxide reduction to be reoxidized. Because viologens are positively charged and are reduced to neutral compounds, it is likely that the resulting charge-transfer complex will have a higher cage escape yield than a complex where the oxidized donor has a positive charge. However, in some

Exploring the role of halogen bonding in iodonium ylides: insights into unexpected reactivity and reaction control

• Carlee A. Montgomery and
• Graham K. Murphy

Beilstein J. Org. Chem. 2023, 19, 1171–1190, doi:10.3762/bjoc.19.86

• halogen bond is influenced by multiple factors including polarization, electrostatic attraction, charge transfer, dispersion and molecular orbital interactions [59][60][61][62][63]. The charge transfer nature (donation into the σ* orbital of the R–X bond) of the halogen bond leads to elongation and

• more complex theories as to why such adducts evolve differently. As previously stated, the strength of a halogen bond interaction is impacted by various factors (e.g., electrostatics, charge transfer abilities, dispersion), where the extent of their influence depends on both the halogen bond donor and

• acceptor [61]. Beyond simply considering the strength of these bonds, other characteristics of this interaction should directly impact the outcomes of the reactions that they undergo. For instance, Mulliken’s initial description of an intermolecular halogen bond was of a charge transfer complex (also known

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

• -BF4 as a suitable conPET catalyst. Following the conPET catalytic cycle, the Mes-Acr+ cation is excited and reductively quenched by DIPEA to yield the acridine radical Mes-Acr• (Figure 10C) [54]. Upon excitation to its twisted intramolecular charge-transfer (TICT) state, Mes-Acr• has an excited-state

• individual compounds but does in fact show additional charge-transfer bands from the preassembly. After electron transfer from *PC1•− to 1d, the C(sp2)–Br bond is cleaved and the aryl radical readily reacts with B2pin2 in a radical substitution reaction yielding the borylated product 17k and a Bpin radical

• excited state lifetimes [95][96], most reactions employing such photocatalysts require special reaction design (e.g., coordination of substrates as ligands to enable intramolecular metal to ligand charge transfer (MLCT)). Only recently have a few examples been reported that observed bimolecular quenching

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

• capability of the PTZ and NI moieties, respectively, by oxidation of the PTZ unit, or by using different aryl substituents attached to the NI unit. This tuning effect was manifested in the UV–vis absorption and fluorescence emission spectra, e.g., in the change of the charge transfer absorption bands. TADF

• intersystem crossing (rISC) is slow, without coupling with an approximate 3LE state. These studies are useful for an in-depth understanding of the photophysical mechanisms of the TADF emitters, as well as for molecular structure design of new electron donor–acceptor TADF emitters. Keywords: charge-transfer

• small energy gap (2J) of the S1/T1 states. Moreover, the orthogonal geometry is beneficial for the intersystem crossing (ISC) of the dyads, i.e., via the spin–orbit charge transfer ISC (SOCT-ISC) [14][15][16][17][18]. It can be considered as a generalization of the El-Sayed’s rule for ISC. This SOCT-ISC

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

• proposed for D–π–A systems. This parameter is a good indication for intramolecular charge transfer from the donor to the acceptor moiety in the ground state. In benzene, the qr value is equal to 0. In a fully quinoid ring, the qr was found to be equal to 0.10–0.12. Calculations based on the bond lengths in

• the aryl fragments determined by X-ray diffraction analysis gave the following average values of the qr parameter: 0.012 for 5d and 0.014 for 5e. For comparison, the same parameter calculated for N,N-dimethyl-4-nitroaniline is 0.038 (X-ray data from reference [33]). Therefore, the π-charge transfer

• . Noncovalent interactions of molecules in crystals and packing effects do not allow one to strictly judge the charge transfer in the oligomers 5. Therefore, we analyzed their UV–vis spectra (Table 3, Figure 8). The functional groups R are located at the far ends of the oligomeric chain and, from the steric

Direct C2–H alkylation of indoles driven by the photochemical activity of halogen-bonded complexes

• Martina Mamone,
• Giuseppe Gentile,
• Jacopo Dosso,
• Maurizio Prato and
• Giacomo Filippini

Beilstein J. Org. Chem. 2023, 19, 575–581, doi:10.3762/bjoc.19.42

• charge transfer state which results in a bathochromic shift of the absorption towards the visible range [19][20]. Upon light irradiation, the EDA complex may undergo an intramolecular single-electron-transfer (SET) process to produce a radical ion pair (D•+, A•−). To avoid the occurrence of a back

Computational studies of Brønsted acid-catalyzed transannular cycloadditions of cycloalkenone hydrazones

• Manuel Pedrón,
• Jana Sendra,
• Irene Ginés,
• Tomás Tejero,
• Jose L. Vicario and
• Pedro Merino

Beilstein J. Org. Chem. 2023, 19, 477–486, doi:10.3762/bjoc.19.37

• also carried out an analysis of the electron localization function (ELF) [31][32] and the charge transfer along the reaction coordinate to determine the different stages and the polarity of the reaction. Results and Discussion The enantioselective intermolecular cycloaddition between hydrazones and

• groups the global charge transfer is not so high to be considered a polar process. The reaction, as previously reported by the classical intermolecular reaction takes place smoothly by the action of the organocatalyst that renders a protonated hydrazone as the reacting functional group. However, in

Functionalization of imidazole N-oxide: a recent discovery in organic transformations

• Koustav Singha,
• Imran Habib and
• Mossaraf Hossain

Beilstein J. Org. Chem. 2022, 18, 1575–1588, doi:10.3762/bjoc.18.168

• perfluoroaryl-substituted 2H-imidazole products, a push–pull fluorophore system was discovered, which can be useful for the preparation of fluorometric sensor materials because of the solvent-dependent intramolecular charge transfer effect (ICT). Here, two reaction pathways were designed: (A) addition

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

• investigate the joint influence of the conformation flexibility and the matching of the energies of the charge-transfer (CT) and the localized triplet excited (3LE) states on the thermally activated delayed fluorescence (TADF) in electron donor–acceptor molecules, a series of compact electron donor–acceptor

• : charge-transfer; electron donor; intersystem crossing; TADF; triplet state; Introduction Thermally activated delayed fluorescence (TADF) has attracted much attention in recent years, not only for its application in organic light emitting diodes (OLED) [1][2][3] but also as a mean for studying of charge

• that dyad was to study the spin–orbit charge-transfer ISC (SOCT-ISC), i.e., to determine, if the ISC is enhanced by the charge recombination (CR) in the orthogonal dyad. Indeed, CR is accompanied by orbital angular momentum change, which off-sets the electron spin angular momentum change, allowing the

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

• where the emissive layer also contained an inorganic salt and a conducting polymer. Recently, a step-change in device performance were achieved by He et al. who employed a cationic TADF compound that possesses low-lying through-space and through-bond charge transfer excited states [23]. The LEEC showed

• of TADF emitters in LEECs, the emission in these devices is typically broad, reflective of the charge transfer (CT) character of the emission, and so colour purity suffers. Narrowband emission has, however, been demonstrated in multiresonant TADF (MR-TADF) materials. MR-TADF compounds, first

• DiKTa as the acceptor [28]. Long range charge transfer is not apparent here and instead the coupled cluster calculations predict a compound that is MR-TADF but where the electron density distribution is delocalized over the entire molecule. Compared to DiKTa-OMe, both S1 and T1 of DiKTa-DPA-OMe are

Dienophilic reactivity of 2-phosphaindolizines: a conceptual DFT investigation

• Nosheen Beig,
• Aarti Peswani and
• Raj Kumar Bansal

Beilstein J. Org. Chem. 2022, 18, 1217–1224, doi:10.3762/bjoc.18.127

• catalyst [14]. As discussed later, this can be rationalized on the basis of the local hardness represented by the Fukui function. The electronic chemical potential (µ) is another useful descriptor that reveals efficacy of charge transfer from the species of higher chemical potential to a species with lower

• unsubstituted 2-phosphaindolizine, the electronic chemical potentials of the other 2-phosphaindolizines are smaller than the electronic chemical potential of 1,3-butadiene indicating the possibility of an effective charge transfer from the latter to the former. Furthermore, the gap between the chemical

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

• similar effect in triazine-based phosphorus-linked graphitic CN structures, with lifetimes of 4.7 and 39 µs seen for g-PCN and g-PCN300, respectively [38]. Improved charge transfer was further confirmed through photocurrent and Nyquist measurements, comparing to pristine g-CN. Photocurrent measurements

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

• donor size and strength: the emitter BPy-pTC with tert-butylcarbazole (TC) as the donor and BPy-p3C with bulky tricarbazole (3C) as the donor unit. Both BPy-pTC and BPy-p3C exhibited prominent emission with TADF properties in solution and in the solid phase. The stronger excited-state charge transfer

• as well as the relevance for fluorescence-based acid–base sensing. Keywords: intramolecular charge transfer; molecular aggregates; sensing; thermally activated delayed fluorescence (TADF); Introduction Metal-free organic solid-state emitters have gained increasing interest in recent years due to

• solution and in the solid state and with multicolor tunability by external stimuli are crucial for task-specific applications. Recently, donor–acceptor (D–A)-based organic emitters have shown tunable optical and electrochemical properties due to alteration of the intermolecular charge-transfer (ICT