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

• -type compound (λPL = 521 nm for POZ-DBPHZ) in cyclohexane. These data indicate that the effective length of π-conjugation is not affected by the number of donors, probably due to the right D–A dihedral angle for both compounds in the ground state. In contrary, the slight blue-shift of the PL spectra of

Efficient synthesis of ethyl 2-(oxazolin-2-yl)alkanoates via ethoxycarbonylketene-induced electrophilic ring expansion of aziridines

• Yelong Lei and
• Jiaxi Xu

Beilstein J. Org. Chem. 2022, 18, 70–76, doi:10.3762/bjoc.18.6

• p–π conjugation. This stabilization is not possible with alkyl groups, explaining why 2-alkylaziridines did not generate the corresponding products. Intermediates C undergo an intramolecular nucleophilic attack to yield ethyl (oxazolidin-2-ylidene)alkanoates D, which further isomerize to more stable

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

• 3,5-dibromoanthranilic acid (1) [61] with cyclohexanone in POCl3 through an adapted reported procedure [62] (Scheme 1). With precursor 2 in hand, we intended to expand the π-conjugation of the tetrahydroacridine core by adding diversely substituted aryl groups using the Suzuki–Miyaura cross-coupling

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

• stability as well. The absorption maxima displayed by polymer 18 (409 nm) in dichloromethane solution was comparable to the above-discussed 1,3-polyazulene 5 (404 nm), however, the long alkyl substituents present at the 6-position of 19 and 20 were disrupting the effective π-conjugation along the polymer

Cationic oligonucleotide derivatives and conjugates: A favorable approach for enhanced DNA and RNA targeting oligonucleotides

• Mathias B. Danielsen and
• Jesper Wengel

Beilstein J. Org. Chem. 2021, 17, 1828–1848, doi:10.3762/bjoc.17.125

• better hybridization properties than LNA-thymidine; however, only modification 22 gave significant increases in Tm relative to modification 19 used as control. This finding was ascribed to both the extended π-conjugation of the alkynyl-functionalized nucleobase and stabilizing electrostatic interactions

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

• catalysis. With this precursor in hand, we intended to expand the π-conjugation by introducing two arylethynyl groups by Sonogashira reactions [66][67][68][69]. For the optimization, we studied the reaction of 2 with phenylacetylene (3a) and we obtained the desired product 4a in up to 72% as best yield

• )-9-chloro-5,6,7,8-tetrahydroacridine derivatives via a double Sonogashira cross-coupling method. The arylethynyl groups expand the π-conjugation of the tetrahydroacridine core. The substituents located at the aryl group influenced the photophysical properties of the prepared molecules. In particular

Recent advances in the application of isoindigo derivatives in materials chemistry

• Andrei V. Bogdanov and
• Vladimir F. Mironov

Beilstein J. Org. Chem. 2021, 17, 1533–1564, doi:10.3762/bjoc.17.111

• ][103][104][105]. Thus, two polymers 56 were obtained in which isoindigo fragments are condensed on the indacenedione scaffold [102]. Despite the presence of an extended π-conjugation system, which determines the ambipolar properties of a transistor based on these polymers, the charge mobility values

• polymers for OFETs. Isoindigoid homopolymers with differing rigidity. Isoindigo-based materials with extended π-conjugation. Poly(isoindigothiophene) compounds as sensors for ammonia. Sensor devices based on poly(isoindigoaryl) compounds. Isoindigo polymers for miscellaneous applications. Mono-, rod-like

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• electron-accepting group coupled with various donors connected via a π-conjugation bridge [31][32][33]. Such dyes offer good NLO characteristics when compared to Disperse Red 1 as well as remarkable thermal stabilities with dissociation temperatures up to 300 °C [31][32]. Schiff bases containing an

• organic NLO chromophore is related to the presence of donor (D) and acceptor (A) groups linked through a π-conjugation path and is characterized by a large first-order hyperpolarizability value (β). However, a small energy gap between the HOMO and the LUMO (Egap) is an important indicator for high NLO

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• mono-substituted sumanene derivatives 49b–d in a stereoselective manner as can be inspected from Scheme 10 [41][42]. In another event, Amaya, Ito, Katoh and Hirao reported a vital building block 53 to extend the π-conjugation bidirectionally through regioselective functionalization (Scheme 11) [43]. To

Aryl-substituted acridanes as hosts for TADF-based OLEDs

• Naveen Masimukku,
• Dalius Gudeika,
• Oleksandr Bezvikonnyi,
• Ihor Syvorotka,
• Rasa Keruckiene,
• Dmytro Volyniuk and
• Juozas V. Grazulevicius

Beilstein J. Org. Chem. 2020, 16, 989–1000, doi:10.3762/bjoc.16.88

• explained by the dihedral angle between the acridanyl and naphthyl moieties, that is the largest one among all the studied compounds, leading to a reduction of π-conjugation. This observation explains the distinct ICT character of the luminescence of compound 4. The dihedral angles in the molecules of 3 and

Synthesis and properties of tetrathiafulvalenes bearing 6-aryl-1,4-dithiafulvenes

• Aya Yoshimura,
• Hitoshi Kimura,
• Kohei Kagawa,
• Mayuka Yoshioka,
• Toshiki Itou,
• Dhananjayan Vasu,
• Takashi Shirahata,
• Hideki Yorimitsu and
• Yohji Misaki

Beilstein J. Org. Chem. 2020, 16, 974–981, doi:10.3762/bjoc.16.86

• systems; electrochemical properties; extended π-conjugation; digital simulation analysis; tetrathiafulvalene; Introduction Tetrathiafulvalenes (TTFs) with extended π-conjugation have attracted attention as possible components of functional materials, such as molecular conductors, field-effect transistors

Towards triptycene functionalization and triptycene-linked porphyrin arrays

• Gemma M. Locke,
• Keith J. Flanagan and
• Mathias O. Senge

Beilstein J. Org. Chem. 2020, 16, 763–777, doi:10.3762/bjoc.16.70

• emission at 617 nm (16207 cm−1) with two equally intense bands (a characteristic of symmetric porphyrins). The nearly similar λmax of both these dimers reinforces the lack of extended π-conjugation or communication that is present in these molecules. Comparatively, the zinc dimer 9 has an increased

• dimer 9 with a gap of 2.03 eV and the butadiyne-linked dimer 20 with 1.87 eV. These values give an initial indication of the extent of π-conjugation occurring within these systems, as the more conjugation present in the system the lower the HOMO–LUMO gap. A spectroscopic comparison of the porphyrin

Direct borylation of terrylene and quaterrylene

• Haruka Kano,
• Keiji Uehara,
• Kyohei Matsuo,
• Hironobu Hayashi,
• Hiroko Yamada and
• Naoki Aratani

Beilstein J. Org. Chem. 2020, 16, 621–627, doi:10.3762/bjoc.16.58

• tetra-borylated quaterrylene despite a low yield. The post modification of rylenes enables us to prepare their borylated products as versatile units after creating the rylene skeletons. Keywords: borylation; π-conjugation; oligorylene; single crystal X-ray structure; solubility; Introduction Compared

Regioselectively α- and β-alkynylated BODIPY dyes via gold(I)-catalyzed direct C–H functionalization and their photophysical properties

• Takahide Shimada,
• Shigeki Mori,
• Masatoshi Ishida and
• Hiroyuki Furuta

Beilstein J. Org. Chem. 2020, 16, 587–595, doi:10.3762/bjoc.16.53

• comparative NMR analysis and mass spectrometry (see Supporting Information File 1). Optical properties The α- and β-ethynyl-substituted BODIPYs exhibit large bathochromic shifts in the absorption and fluorescence spectra relative to the unsubstituted 1a with extended π-conjugation (Figure 4 and Figure 5). The

Copper-catalyzed remote C–H arylation of polycyclic aromatic hydrocarbons (PAHs)

• Anping Luo,
• Min Zhang,
• Zhangyi Fu,
• Jingbo Lan,
• Di Wu and
• Jingsong You

Beilstein J. Org. Chem. 2020, 16, 530–536, doi:10.3762/bjoc.16.49

• fluorescence, and have been widely applied in many scientific areas including chemistry, biomedicine and materials science [1][2][3][4][5][6]. The arylation reaction of PAHs is an important strategy to further extend the π-conjugation length, which can effectively adjust the photophysical properties of

Formal preparation of regioregular and alternating thiophene–thiophene copolymers bearing different substituents

• Atsunori Mori,
• Keisuke Fujita,
• Chihiro Kubota,
• Toyoko Suzuki,
• Kentaro Okano,
• Takuya Matsumoto,
• Takashi Nishino and
• Masaki Horie

Beilstein J. Org. Chem. 2020, 16, 317–324, doi:10.3762/bjoc.16.31

• copolymer; nickel(II) catalyst; oligosiloxane; regioregular polythiophene; solubility; Introduction Polythiophenes attract much attention in materials science because of their extended π-conjugation, which is applied for a wide range of electronic materials. In particular, the regioregular polymers with a

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

• of the photochromic reactions to visible light are to extend the π-conjugation and to utilize photosensitizers. Especially, triplet photosensitizers, which form the triplet state of a molecule by the triplet–triplet energy transfer, have been frequently used in photoresists, photodynamic therapy, and

• assigned to the transient absorption of the benzil unit of Benzil-PIC. The absorption is slightly shifted to the red as compared to those of benzil probably due to the extended π-conjugation of the benzil unit connected to the PIC unit. The two peaks continuously shift to the shorter wavelength (503 and

Small anion-assisted electrochemical potential splitting in a new series of bistriarylamine derivatives: organic mixed valency across a urea bridge and zwitterionization

• Keishiro Tahara,
• Tetsufumi Nakakita,
• Alyona A. Starikova,
• Takashi Ikeda,
• Masaaki Abe and
• Jun-ichi Kikuchi

Beilstein J. Org. Chem. 2019, 15, 2277–2286, doi:10.3762/bjoc.15.220

• )•+ radical cations having dithienylethene bridges [21][22]. This was achieved by a regulation of the π-conjugation length through photoinduced formation/dissociation of σ bonds in the bridge, which was accomplished with changeovers from a localized system (class I) to a moderately delocalized one (class II

• means that the π orbital of the central C=O moiety does not contribute to the π-conjugation in the HOMOs. Such HOMO properties would be understood by comparison with a well-known reference bis(NAr3) derivative MeO-TPD, in which the NAr3 units are directly connected through a σ-bond [6]. MeO-TPD shows a

Synthesis, photophysical and electrochemical properties of pyridine, pyrazine and triazine-based (D–π–)₂A fluorescent dyes

• Keiichi Imato,
• Toshiaki Enoki,
• Koji Uenaka and
• Yousuke Ooyama

Beilstein J. Org. Chem. 2019, 15, 1712–1721, doi:10.3762/bjoc.15.167

• electron-donating and electron-accepting abilities of the D and A moieties and the expansion of π conjugation, respectively, can lead to a decrease in the energy gap between the HOMO and LUMO because the highest occupied molecular orbital (HOMO) is localized over the π-conjugated system containing the D

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• the metal surface [11][18]. With increasing π-conjugation from the azobenzene into the platform, and thus coupling to the gold surface, the activation barrier drops to almost zero (≈8 kJ mol−1) and the frequency factors (log A) become negative [11]. Vanishing barriers and low frequency factors are

• the azo group, providing a full π-conjugation path of the N=N unit through the ethynyl spacer into the platform. Diazocine-TATA 2 is connected in meta-position and thus interrupting conjugation [24][25]. Both diazocine-TATAs are equipped with methoxy groups, which serve as “reporter units” indicating

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• approximation reflecting the HOMO–LUMO gap. The sole exception to this trend is the only derivative with an H-substituted double bond ethene-Me, which exhibit the expected behavior of a less facile oxidation of the Z-isomer due to its somewhat twisted π-system leading to less pronounced π-conjugation and

• , similarly to what is known for normal DAEs [40][41]. The differences between the first and second oxidation wave seem to depend on the nature of the substituents with donors reducing the gap, presumably by more efficient stabilization of the dication, and on conformational rigidity dictating the extent of π

• -conjugation between both hemispheres. Similar to the model compound sDTE66-Me, all available sDTE66 derivatives as well as both Z-configured sDTE77 derivatives undergo electrocyclization upon oxidation. This also holds true for all cyclopentene-bridged DTE derivatives. However, in butene-Me the formation of

Synthesis and characterization of π–extended “earring” subporphyrins

• Haiyan Guan,
• Mingbo Zhou,
• Bangshao Yin,
• Ling Xu and
• Jianxin Song

Beilstein J. Org. Chem. 2018, 14, 1956–1960, doi:10.3762/bjoc.14.170

• 1400 nm with several observable peaks. This remarkable absorption in the NIR region is comparable with that of the analogue “earring” porphyrins and reveals the π-conjugation between the subporphyrin and tripyrrin moiety. Conclusion In summary, we synthesized a π-extended “earring” subporphyrin from β

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• chemical structure is sketched in Figure 9 [41]. Depending on the π-conjugation of the NHC-based bidentate ligand, emitting complexes with luminescence varying from blue (19 and 20) to yellow (21) were obtained. Several devices were prepared following a remote phosphor configuration, which places the

• state. Nevertheless, Che and co-workers demonstrated that extending the π-conjugation of the cyclometalated ligand led to enhanced phosphorescence quantum yields [51][52]. Indeed, the increased conjugation resulted in a modification of the frontier molecular orbitals and prevention of Jahn–Teller

• in spite of the stronger ligand-field exerted. Similar to the case of C^N^N type of ligands, a significant structural distortion is the main factor that accounts for this low emission efficiency. However, Che and co-workers demonstrated that extension of the π-conjugation at the tridentate ligand

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• around 345 and 456 nm. The peaks at around 456 nm result from their ICT states from the donor to the acceptor, while the absorption below 380 nm is caused by their short π-conjugation. It is obvious that 2 has not only a higher oscillator strength (f) than 1 from its transition of charge-transfer states

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• a suitable steric hindrance that introduces an internal twist and interrupts the π-conjugation but also by a sufficient distance between the electron-donating and the electron-accepting moieties [22][23][24][25]. In the design of TADF materials, it should be mentioned the major importance of the

• be realized by totally blocking the structure, what was done with B9 and B10 in which two of the three aromatic rings of triphenylamine were connected to the boron center [39]. By elongating the π-conjugation of the electron-donating group in B10 compared to B9, a more delocalized HOMO level could be

• and triazine derivatives. In this field, the contribution of the Adachi’s group is remarkable. The first report mentioning a pure blue emission with a diphenylsulfone derivative was reported in 2012 [40]. By a careful control of the π-conjugation length between the donor and the acceptor, D3-based