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

• fluorescent dyes constructed of an electron-donating moiety (D) and an electron-withdrawing moiety (A), linked by a π-conjugated unit thanks to their intense photoabsorption and fluorescence emission characteristics originating from the intramolecular charge transfer (ICT) excitation from the D to the A

Introducing a new 7-ring fused diindenone-dithieno[3,2-b:2',3'-d]thiophene unit as a promising component for organic semiconductor materials

• Valentin H. K. Fell,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Eman J. Hussien and
• Peter J. Skabara

Beilstein J. Org. Chem. 2022, 18, 944–955, doi:10.3762/bjoc.18.94

• , which is considered to be an intramolecular charge transfer (ICT) transition [54]. Only the latter band is, in the solid state, shifted to lower energies compared to the one of the solution spectrum due to dipole–dipole interactions in the condensed phase, as seen for example in DPP derivatives [55

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

• and charge-transfer (HLCT) and doublet emission have been designed and demonstrated [9][10]. However, the development of these materials often requires complicated molecular design and synthesis [11][12]. Alternatively, it is also possible to produce light emission by molecular exciplexes composed of

• 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

Syntheses of novel pyridine-based low-molecular-weight luminogens possessing aggregation-induced emission enhancement (AIEE) properties

• Masayori Hagimori,
• Tatsusada Yoshida,
• Yasuhisa Nishimura,
• Yukiko Ogawa and
• Keitaro Tanaka

Beilstein J. Org. Chem. 2022, 18, 580–587, doi:10.3762/bjoc.18.60

• in many bioactive substances and medicines as one of the basic core skeletons [11][12]. In addition, pyridine is an essential skeleton for fluorescent compounds, and fluorescence can be enhanced by optimizing the internal charge transfer (ICT) state of pyridine by introducing electron-donating or

• ), intramolecular charge transfer, and twisted intramolecular charge transfer (TICT) are involved in AIEE [20][21][22]. Various AIEE-based luminogens have been developed based on these mechanisms; however, many of them are high-molecular-weight compounds (MW > 500) with bulky substituents, which limits their

• , the S0→S1 transition in both compounds is mostly dominated by charge transfer from the HOMO to the LUMO, corresponding to a π→π* electron transition. There was no significant change (≤7 nm) in the Exmax for compound 3a in the three solvents: Exmaxobs ranged from 468 to 471 nm and Exmaxcalc ranged from

Synthesis of a new water-soluble hexacarboxylated tribenzotriquinacene derivative and its competitive host–guest interaction for drug delivery

• Man-Ping Li,
• Nan Yang and
• Wen-Rong Xu

Beilstein J. Org. Chem. 2022, 18, 539–548, doi:10.3762/bjoc.18.56

• , fluorescence titration experiments were conducted. As presented in Figure 1c, the emission of TBTQ-CB6 was gradually reduced upon increasing the MV concentration, suggesting charge transfer from the electron-rich host to the electron-deficient guest. According to the fluorescence titration data, 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

• main requirement for efficient TADF is a negligible energy difference between the lowest singlet and triplet states (∆EST) which is often obtained in (hetero)aromatic compounds possessing twisted electron-donor (D) and acceptor (A) fragments with strong intramolecular charge transfer (ICT) [5][6][7

• strength of the acceptor unit, namely the energy of the LUMO (see Table 1 and Figure S28 in Supporting Information File 1), while the lower emission energy was observed for compounds with more pronounced charge-transfer (CT) character. This was also evidenced by larger FWHM values of fluorescence spectra

Comparative study of thermally activated delayed fluorescent properties of donor–acceptor and donor–acceptor–donor architectures based on phenoxazine and dibenzo[a,j]phenazine

• Saika Izumi,
• Prasannamani Govindharaj,
• Anna Drewniak,
• Paola Zimmermann Crocomo,
• Satoshi Minakata,
• Leonardo Evaristo de Sousa,
• Piotr de Silva,
• Przemyslaw Data and
• Youhei Takeda

Beilstein J. Org. Chem. 2022, 18, 459–468, doi:10.3762/bjoc.18.48

• thermally activated delayed fluorescent behavior. Keywords: charge-transfer; dibenzophenazine; donor–acceptor; organic light-emitting diodes; thermally activated delayed fluorescence; Introduction Thermally activated delayed fluorescence (TADF), which was firstly reported in 1961 by Parker and Hatchard [1

• zero or even negative [12][13], while the SOC is as large as possible. One of the promising molecular design strategies to meet the above-mentioned criteria involves a highly twisted (D)n–(A)m (D: electron donor; A: electron acceptor) system, in which efficient intramolecular charge transfer (ICT

• typical to the emission from a charge–transfer excited state (CT). The CT emission was totally quenched in a solvent that is more polar than toluene (Figure 2). These photophysical observations are consistent with those of the D–A–D-type compound POZ-DBPHZ [17], indicating that one D–A pair is sufficient

Site-selective reactions mediated by molecular containers

• Rui Wang and
• Yang Yu

Beilstein J. Org. Chem. 2022, 18, 309–324, doi:10.3762/bjoc.18.35

• reaction, the anthracene moiety stacks onto the planar triazine of B through π–π stacking and possible charge-transfer interaction between each other, which stabilizes the complex. However, after the reaction, the framework of the product is bent at the 9,10-position, which undermines the host–guest

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

• separation of the HOMO and LUMO on donor and acceptor, respectively, will result in an S1→S0 transition with predominantly charge transfer (CT) character. Highly twisted donor–acceptor architectures are typically employed to realize small ΔEST [4][8]. SOC can be enhanced by ensuring that the nature of the S1

Photophysical, photostability, and ROS generation properties of new trifluoromethylated quinoline-phenol Schiff bases

• Inaiá O. Rocha,
• Yuri G. Kappenberg,
• Wilian C. Rosa,
• Clarissa P. Frizzo,
• Nilo Zanatta,
• Marcos A. P. Martins,
• Isadora Tisoco,
• Bernardo A. Iglesias and
• Helio G. Bonacorso

Beilstein J. Org. Chem. 2021, 17, 2799–2811, doi:10.3762/bjoc.17.191

• ultraviolet range, the observed transitions can be attributed to the π → π* transitions and refer to the heterocyclic ring. Transitions above 350 nm can be attributed to the n → π* transition referring to the imine moiety, causing an intramolecular charge-transfer type (ICT) transition [27]. Complementary

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

• the photocatalyst RuII is irradiated by light, an electron is transferred from the frontier metal d orbital (t2g orbital) to the ligand-centered π* orbital (RuII*). A metal-to-ligand charge transfer (MLCT) results in the excited singlet state. Through rapid intersystem crossing (ISC), the singlet

Synthesis and investigation on optical and electrochemical properties of 2,4-diaryl-9-chloro-5,6,7,8-tetrahydroacridines

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 2450–2461, doi:10.3762/bjoc.17.162

• . Their bands at lower energy may be attributed to the intramolecular charge transfer (ICT) from the electron-donating methoxy groups to the tetrahydroacridine core. The Stokes shifts of 4a–d were calculated based on their absorption and emission spectra. Derivative 4b, containing an electron-donating

Chemical syntheses and salient features of azulene-containing homo- and copolymers

• Vijayendra S. Shetti

Beilstein J. Org. Chem. 2021, 17, 2164–2185, doi:10.3762/bjoc.17.139

• of the spectrum, the largest shift of 2500 nm was displayed by the polymer 56. The origin of such absorption bands in the near-IR region can be attributed to an intramolecular charge transfer (ICT) process leading to the lowering of the HOMO–LUMO bandgap [34]. The azulene moiety plays a pivotal role

• here as it is polar resonance stabilized and protonation leads to a drift in its electron density from the seven-membered ring to the five-membered ring generating a stable tropylium cation making it a strong electron acceptor during the intramolecular charge transfer (ICT) process. These protonated

Cerium-photocatalyzed aerobic oxidation of benzylic alcohols to aldehydes and ketones

• Girish Suresh Yedase,
• Sumit Kumar,
• Jessica Stahl,
• Burkhard König and
• Veera Reddy Yatham

Beilstein J. Org. Chem. 2021, 17, 1727–1732, doi:10.3762/bjoc.17.121

• benzylic alcohol selectively to the aldehyde or ketone is still desirable. Recently, cerium photocatalysis was introduced as a robust alternative to generate oxygen or carbon-centered radicals under mild reaction conditions [57][58][59][60][61][62][63][64]. CeCl3 reacts via ligand-to-metal charge transfer

• inhibition of the catalytic cycle upon the addition of TEMPO revealed that the reaction proceeds through radical intermediates. Next, we carried out UV–vis monitoring experiments in order to verify whether the interaction with the substituted benzyl alcohols and CeIV could lead to a ligand-to-metal charge

• transfer (LMCT) process, which reduces the CeIV species to CeIII, similarly as reported by Zuo and co-workers [57]. We chose (n-Bu4N)2CeIVCl6 as the CeIV source to ensure a sufficient solubility in organic solvents and to facilitate the detection of the species. The CeIV(OBn)Cln complex was prepared by

2,4-Bis(arylethynyl)-9-chloro-5,6,7,8-tetrahydroacridines: synthesis and photophysical properties

• Najeh Tka,
• Mohamed Adnene Hadj Ayed,
• Mourad Ben Braiek,
• Mahjoub Jabli,
• Noureddine Chaaben,
• Kamel Alimi,
• Stefan Jopp and
• Peter Langer

Beilstein J. Org. Chem. 2021, 17, 1629–1640, doi:10.3762/bjoc.17.115

• attributed to intermolecular charge transfer between the oxygen lone pair electrons and the quinoline core. The unsubstituted derivative 4a presents an onset of absorption (λonset) at 389 nm and its optical band gap was deduced to be around 3.18 eV. Tetrahydroacridines 4e and 4f showed approximately the same

Design, synthesis and photophysical properties of novel star-shaped truxene-based heterocycles utilizing ring-closing metathesis, Clauson–Kaas, Van Leusen and Ullmann-type reactions as key tools

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2021, 17, 1374–1384, doi:10.3762/bjoc.17.96

• role as donors in the intramolecular partial charge-transfer cascade to transfer the extra electronic density. Apart from pure affection besides many more reasons for the constant fascination and utility of this beautifully simple yet much effective heteroaromatic system, this unique nitrogen

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• -aryl substituent to the berberine chromophore. The latter has been shown to operate also in resembling cationic, biaryl-type dyes [42][43]. Along the same lines, the low intrinsic emission quantum yield of the parent berberine (1a) has been suggested to result from an internal charge transfer (ICT

Prins cyclization-mediated stereoselective synthesis of tetrahydropyrans and dihydropyrans: an inspection of twenty years

• Asha Budakoti,
• Pradip Kumar Mondal,
• Prachi Verma and
• Jagadish Khamrai

Beilstein J. Org. Chem. 2021, 17, 932–963, doi:10.3762/bjoc.17.77

• DDQ and the subsequent abstraction of hydride from the benzylic or allylic position generated a charge-transfer complex 298. The complex 298 formed a tin-containing ate oxocarbenium ion complex 299 with SnBr4, and then rapid C–C bond formation took place to generate the cyclic intermediate 300. The

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• phenomena based on the electron-donor–acceptor (EDA) complex [1][2][3]. Significantly, a broad absorption peak unrelated to the structure, called charge-transfer band, is typically located in the visible region of the UV–vis spectrum [4], which manifests the color variability of the mixed solution of the

• that the EDA complex not only undergoes charge transfer but also proton transfer in this approach. The optimization experiment showed that the wavelength of the light source must overlap with the absorption spectrum of the EDA complex. Most importantly, given that the best yield was achieved when the

• the fact that diamine can condense with the enol substrate, forming an imine-ion intermediate absorbing in the visible region. The direct excitation of the intermediate leads to a charge-transfer excited state, completing the stereocontrolled intermolecular cycloaddition reaction with a good ratio of

[2 + 1] Cycloaddition reactions of fullerene C₆₀ based on diazo compounds

• Yuliya N. Biglova

Beilstein J. Org. Chem. 2021, 17, 630–670, doi:10.3762/bjoc.17.55

• ) and cobaltocene (Cp2Co) in order to create charge-transfer complexes with the purpose of searching for efficient magnetic materials based on fullerenes. It can be seen in Scheme 16 that methanofullerene 52 was obtained from the initial, also para-substituted, ethyl diazo(4-nitrophenyl)acetate in 32

Amino- and polyaminophthalazin-1(2H)-ones: synthesis, coordination properties, and biological activity

• Zbigniew Malinowski,
• Emilia Fornal,
• Agata Sumara,
• Renata Kontek,
• Karol Bukowski,
• Beata Pasternak,
• Dariusz Sroczyński,
• Joachim Kusz,
• Magdalena Małecka and
• Monika Nowak

Beilstein J. Org. Chem. 2021, 17, 558–568, doi:10.3762/bjoc.17.50

• the coordination of copper(II) through nitrogen atoms of the pyridin-2-yl substituent, the pyridazin-3-one moiety, and the 2-(dimethylamino)ethyl group. In the vis–NIR spectrum recorded in methanol, based on TD-DFT calculations, the d–d, metal–ligand charge transfer (MLCT), ligand–metal charge

• transfer (MLCT), and intraligand charge transfer (ILCT) transitions were identified. The vis–NIR spectroscopy revealed that in complex 17 the metal-to-ligand stoichiometry is equal to 1:1. In turn, cyclic voltammetry was used to investigate the electrochemical behavior of complex 17. The measurements on a

Mesoionic tetrazolium-5-aminides: Synthesis, molecular and crystal structures, UV–vis spectra, and DFT calculations

• Vladislav A. Budevich,
• Sergei V. Voitekhovich,
• Alexander V. Zuraev,
• Vadim E. Matulis,
• Vitaly E. Matulis,
• Alexander S. Lyakhov,
• Ludmila S. Ivashkevich and
• Oleg A. Ivashkevich

Beilstein J. Org. Chem. 2021, 17, 385–395, doi:10.3762/bjoc.17.34

• structure in Figure 4c). For more details, see Supporting Information File 1. Charge transfer (CT) during excitation plays a key role in many technological applications because CT states correspond to a light-activated electron–hole separation where the positive and negative charges are distant enough to

• –vis spectra and charge transfer were carried out within density functional theory for ground states and time-dependent density functional theory (TD-DFT) for excited states using the τ-dependent hybrid tHCTHhyb functional [37] with the 6-311+G(2d,p) basis set [38]. The chosen functional allows to

• , methanol, water. Solvation effects were considered using the SMD [40] model in terms of Linear Response scheme [41]. The analysis of charge transfer during S0→S1 transition was carried out by using the Multiwfn software [36]. The NBO analysis and MESP calculations were performed using the B3LYP/6-31G(d

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• -dependent density functional theory calculations indicate that when only two ortho-disposed carbazole donors are used (Type I molecules), the lowest-lying triplet state possesses locally excited (LE) character while the lowest-lying singlet state possesses charge-transfer character. When five carbazole

• (HONTOs) and the lowest unoccupied natural transition orbitals (LUNTOs) show good agreement with the HOMOs and LUMOs (Figure 5 and Figure 6). As the HOMOs and LUMOs of the seven molecules are sufficiently separated, the nature of the S1 is charge-transfer (CT) in character. The S1 energies of 2CzCF3

• ]. We analysed the higher excited states of the fluorinated acceptor-containing emitters in both Type I and Type II structures. For 2CzCF3, the T1 is locally excited; further, T2 (3.46 eV) to T6 (3.58 eV) all exhibited significant LE character. The lowest triplet state that exhibits charge transfer

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

• introducing bulky substituents [11][12][13][14], enhanced Intramolecular Charge Transfer (ICT) character [15][16], cross-dipole packing [17] and J-aggregate formation [18][19][20][21][22]. Specifically, in 2001, Tang's group reported an exactly opposite phenomenon to ACQ, namely aggregation-induced emission

• (methyl and tertiary butyl), it is possible to change the energy content of the emissive states with predominant π–π* character. On the other hand, by introduction of increasingly stronger π-donors (methoxy, methylsulfanyl and dimethylamino) it is possible to progressively enhance the charge transfer (CT

• reported for these kind of compounds. At 77 K, non-radiative decays caused by the interaction with the solvent are suppressed and charge transfer states are destabilized. Therefore, the emission at low temperature is originated by singlet states with higher π–π* character, if compared with rt. Except for

Changed reactivity of secondary hydroxy groups in C8-modified adenosine – lessons learned from silylation

• Jennifer Frommer and
• Sabine Müller

Beilstein J. Org. Chem. 2020, 16, 2854–2861, doi:10.3762/bjoc.16.234

• charge transfer [23][24]. In the course of monomer synthesis, we encountered unexpected results regarding the reactivity and selectivity of the two secondary hydroxy groups of the adenosine derivative 7 (Scheme 1) in the silylation step, leading to non-satisfactory overall reaction yields. Therefore, the