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

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

• spectra was observed at 77 K, which we attribute to the dominance of the CT character for the emissive singlet state, independently of the conformation of the phenyl groups. As NMe2 contains strong donor and acceptor moieties, the partial role of a Twisted Intramolecular Charge Transfer (TICT) character

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

• tune intramolecular charge transfer (ICT) intensity and it can increase NLO properties [11][12][13][14]. Some ions such as proton (H+) and hydroxide (OH−), in aqueous environments, play significant roles in industrial, biological, and environmental processes [15][16][17]. Their presence in aqueous

Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• molecular ground-state electrical dipole (µ = 7.04 D), which is an evidence for an intramolecular charge transfer (CT) character of the chromophore [34]. The predicted UV–vis spectra by TD-DFT are in excellent agreement with the experimental one (Figure 3, Table 1, the vibrational coupling is neglected

Clickable azide-functionalized bromoarylaldehydes – synthesis and photophysical characterization

• Dominik Göbel,
• Marius Friedrich,
• Enno Lork and
• Boris J. Nachtsheim

Beilstein J. Org. Chem. 2020, 16, 1683–1692, doi:10.3762/bjoc.16.139

• facilitate the ISC process from S1 to Tn and thus increase the spin-orbital coupling [38][39][40][41][42][43][44][45][46][47]. Also, decreasing the singlet–triplet splitting energy (ΔEST) caused by intramolecular charge-transfer (ICT) interactions is an approved method [48][49]. (2) Significant reduction of

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

• moieties, respectively [19]. Additionally, a weak absorption band (shoulder) at ca. 348 nm was detected for compound 2, evidencing an intramolecular charge transfer (ICT) between the phenothiazine and quinazoline units. The energy band gap values determined from the edges of the experimental UV spectra of

Synthesis of novel multifunctional carbazole-based molecules and their thermal, electrochemical and optical properties

• Nuray Altinolcek,
• Ahmet Battal,
• Mustafa Tavasli,
• William J. Peveler,
• Holly A. Yu and
• Peter J. Skabara

Beilstein J. Org. Chem. 2020, 16, 1066–1074, doi:10.3762/bjoc.16.93

• distinctive absorption bands: high and mid energy bands due to locally excited (LE) transitions and low energy bands due to intramolecular charge transfer (ICT) transitions. In dichloromethane solutions compounds 7a and 7b gave emission maxima at 561 nm and 482 nm with quantum efficiencies of 5.4% and 97.4

• Fluorescence and Absorbance Spectrometer. Each compound (7a/7b) displayed three distinctive absorption bands in the UV–vis spectra: high energy bands and mid energy bands were assigned to π–π* and n–π* transitions, whereas the low energy bands were assigned to an intramolecular charge transfer (ICT) transition

• dependent on the excitation wavelength chosen and the solvent used. It is believed that the dual emission was due to mixed locally excited (LE) and intramolecular charge transfer (ICT) states and the single emission was due to the ICT state. Photoluminescence (PL) spectra of compounds 7a and 7b in different

Cation-induced ring-opening and oxidation reaction of photoreluctant spirooxazine–quinolizinium conjugates

• Phil M. Pithan,
• Sören Steup and
• Heiko Ihmels

Beilstein J. Org. Chem. 2020, 16, 904–916, doi:10.3762/bjoc.16.82

• extended π system or an intramolecular charge transfer (ICT). This property may allow to use visible light with longer wavelength to induce the ring-opening reaction, which would be favorable, e.g., for biological applications. The stilbene etheno bridge, however, may also lead to an intricate photochromic

One-pot synthesis of dicyclopenta-fused peropyrene via a fourfold alkyne annulation

• Ji Ma,
• Yubin Fu,
• Junzhi Liu and
• Xinliang Feng

Beilstein J. Org. Chem. 2020, 16, 791–797, doi:10.3762/bjoc.16.72

• -membered ring B. The large difference between the LUMO and HOMO leads to an intramolecular charge transfer, resulting in broad absorption bands in the UV–vis spectrum (Figure 3a) [36]. In addition, the LUMO energy of 1 (−2.98 eV) is significantly lower than that of 6 (−2.38 eV), which is responsible for

Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• , the strong donor–acceptor system in 3a led to an intramolecular charge-transfer (ICT) state that did not lead to a subsequent photoreaction [77]. In contrast, the absorption bands of the substrates 3b–d decreased relatively fast upon irradiation, but the maxima did not disappear completely (Figure 5B

Plasma membrane imaging with a fluorescent benzothiadiazole derivative

• Pedro H. P. R. Carvalho,
• Jose R. Correa,
• Karen L. R. Paiva,
• Daniel F. S. Machado,
• Jackson D. Scholten and
• Brenno A. D. Neto

Beilstein J. Org. Chem. 2019, 15, 2644–2654, doi:10.3762/bjoc.15.257

• agreement with the experimental data and helped to understand the stabilizing intramolecular charge-transfer process from the first excited state. The new fluorescent derivative could be applied as selective bioprobe in several cell lines and displayed plasma-membrane affinity during the imaging experiments

• noted in all tested solvents (134–173 nm), thus pointing to efficient stabilizations through intramolecular charge-transfer (ICT) processes from the excited states. The largest Stokes shift was noted in the aqueous solution, indicating the dye’s stability in this solvent. The solvatochromic analyses of

Arylisoquinoline-derived organoboron dyes with a triaryl skeleton show dual fluorescence

• Vânia F. Pais,
• Tristan Neumann,
• Ignacio Vayá,
• M. Consuelo Jiménez,
• Abel Ros and
• Uwe Pischel

Beilstein J. Org. Chem. 2019, 15, 2612–2622, doi:10.3762/bjoc.15.254

• these dyes such as intramolecular charge-transfer processes and tunable red-shifted emission bands. Generally, the so far investigated borylated arylisoquinoline dyes show principally fluorescence quenching (on-off switching) on the formation of the corresponding fluoroboronate complexes [37]. Herein

• situated in between. These trends support that for the herein investigated dyes intramolecular charge-transfer (ICT) phenomena might play a role in the observation of the LW emission features. According to our previous observations the electron-acceptor moiety is likely constituted by the isoquinolinyl

• residue (naphthyl, 4-methoxynaphthyl, pyrenyl, anthryl). This provides some hint that intramolecular charge-transfer phenomena are likely involved. Laser-flash photolysis studies provided insights into the existence of excited triplet states. The addition of fluoride anions led to pronounced fluorescence

Probing of local polarity in poly(methyl methacrylate) with the charge transfer transition in Nile red

• Aydan Yadigarli,
• Qimeng Song,
• Sergey I. Druzhinin and
• Holger Schönherr

Beilstein J. Org. Chem. 2019, 15, 2552–2562, doi:10.3762/bjoc.15.248

• films on a glass support was probed by the energy of the charge transfer transition in the oxazine dye Nile red (NR) at 25 °C. The absorption and fluorescence spectra of NR were observed to shift to the red with increasing solvent polarity, because of the intramolecular charge transfer character of the

• the phenomenon is still far from accurate. Fortunately, a contribution of solute to the large amplitude motion of the diethylamino group (twisting) in intramolecular charge transfer excited state of NR, postulated in references [21][24][25] was later associated with an artefact [26]. However, the

• intramolecular charge transfer state of 4-(diisopropylamino)benzonitrile (DIABN). Data for all solvents except for the alcohols are fitted well to the linear Equation 8 with a positive slope βf = 0.434. The value of 19.16 ± 0.19 D agrees well with that determined from the solvatochromic expressions (Equations 1

1,2,3,4-Tetrahydro-1,4,5,8-tetraazaanthracene revisited: properties and structural evidence of aromaticity loss

• Arnault Heynderickx,
• Sébastien Nénon,
• Olivier Siri,
• Vladimir Lokshin and
• Vladimir Khodorkovsky

Beilstein J. Org. Chem. 2019, 15, 2059–2068, doi:10.3762/bjoc.15.203

• –C8–N9 atom chains and the respective bond lengths of the second independent molecule of 3 reveals a contribution of the intramolecular charge transfer from the electron donating ethylenediamino moiety (D) toward the electron accepting ethylenediimino (A) moiety as shown by the narrow range of the C–N

• aromaticity of quinoxaline derivative 3 decreases compared to aromatic and planar 1 [23][24] because of the presence of the amino groups that give rise to intramolecular charge transfer. This effect is even stronger in 6a and 7a because of delocalization of the positive charge. The equilibrium geometries of 3

• , 6a and 7a obtained by calculations are in good agreement with the X-ray structural data (Table 1). The geometry optimized structures confirm that the bond lengths equalization and the aromaticity loss observed in the X-ray structures stem from the intramolecular charge transfer from the electron

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

• properties of the three dyes were investigated by photoabsorption and fluorescence spectroscopy, Lippert–Mataga plots, cyclic voltammetry and density functional theory calculations. The photoabsorption maximum (λmax,abs) and the fluorescence maximum (λmax,fl) for the intramolecular charge-transfer

• . Thus, the D–π–A dyes exhibit intense photoabsorption and fluorescence emission properties based on the intramolecular charge transfer (ICT) excitation from the D moiety to the A moiety [1][2][3][4]. Moreover, the D–π–A structure possesses considerable structural characteristics: the increase in the

• pyridine, pyrazine or triazine ring as the electron-withdrawing group (electron-accepting group, A), and their photophysical and electrochemical properties were investigated. It was found that the intramolecular charge-transfer (ICT)-based photoabsorption and fluorescence bands of the three dyes appear at

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• intramolecular charge-transfer dyes. Phosphated tetraphenylethylene was involved as the classical aggregation-induced emission dye. Sulfonated acedan representing one example of two-photon fluorescent probes, was also investigated. A ruthenium(II) complex with carboxylated bipyridyl ligands was included as a

• charge-transfer dyes. P-TPE was included in the study as a classical aggregation-induced emission (AIE) dye and TPS as a representative of a two-photon fluorescent probe. Ru(dcbpy)3 was involved as a member of luminescent transition-metal complexes. Of our special interest in the present study is to

• with carboxylated bipyridyl ligands (Ru(dcbpy)3), were screened as model guests on account of the desired strong host–guest binding affinity (Scheme 2). Fl, EY, RB, TPPS and AlPcS4 were employed as classical aggregation-caused quenching (ACQ) dyes; 2,6-TNS and 1,8-ANS were selected as intramolecular

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• higher energy form has to be with quite small molar absorptivity in comparison to the lower one; (iv) the quantum yield of the photoisomerization has to be as high as possible, which requires the design of MOST systems with completely suppressed or minimal fluorescence, intramolecular charge transfer or

Synthesis and fluorescent properties of N(9)-alkylated 2-amino-6-triazolylpurines and 7-deazapurines

• Andrejs Šišuļins,
• Jonas Bucevičius,
• Yu-Ting Tseng,
• Irina Novosjolova,
• Kaspars Traskovskis,
• Ērika Bizdēna,
• Huan-Tsung Chang,
• Sigitas Tumkevičius and
• Māris Turks

Beilstein J. Org. Chem. 2019, 15, 474–489, doi:10.3762/bjoc.15.41

• heterocycles, which were additionally extended by triazole moieties, the compounds with electron-donating groups showed intramolecular charge transfer character (ICT/TICT) of the excited states which was proved by solvatochromic dynamics and supported by DFT calculations. In the 7-deazapurine series this led

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• for 3, which showed a broadening and a marked decrease of the absorption band (Figure S17, Supporting Information File 1). This presumably originates from a deprotonation of the terminal alkylammonium group of the putrescine chain, which could fold back and enable an intramolecular charge transfer

A pyridinium/anilinium [2]catenane that operates as an acid–base driven optical switch

• Sarah J. Vella and
• Stephen J. Loeb

Beilstein J. Org. Chem. 2018, 14, 1908–1916, doi:10.3762/bjoc.14.165

• of [8DB24C8]6+ and [8-HDB24C8]7+ are shown in Figure 5 for 2.0 × 10−5 M solutions in CH3CN. The molar absorptivity (ε) of [8DB24C8]6+ was calculated to be 22,680 L mol−1 cm−1 with λmax at 412 nm. The large absorption is due to an intramolecular charge transfer (ICT) band arising from charge transfer

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

• between these donor-acceptor groups, namely meta- and para-substitution. As expected, the intramolecular charge transfer character was less prominent in the absorption features of compounds with meta-linkages. Nevertheless, all compounds showed a 3IL/3MLCT emission in the green region, that resembled well

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

• donors (D) and electron acceptors (A) are introduced into the molecule to form an intramolecular charge transfer (ICT) state with a large twisting angle between the donor and the acceptor to achieve the separation of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO

• , but also a weaker oscillator strength from its local excited (LE) states. It could be considered that 2 has a better configuration, which is advantageous to intramolecular charge transfer compared with 1, which coincides with the conclusion from DFT calculation. The PL spectra of the materials in

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

• generated, resulting in a greater intramolecular charge transfer and an increase of the oscillator strength. As a result, EQE of corresponding OLEDs increased from 13.5% (459 nm, (0.13, 0.09)) for B9-based devices to 20.2% (467 nm, (0.12, 0.13)) for B10-based devices. If the electron-to-photon conversions

• problem is commonly observed if the isolation of the electron-donating and electron-accepting parts is obtained upon extension of the distance between the two moieties. Indeed, as a consequence of this strategy, a weaker intramolecular charge transfer takes place and a reduction of the oscillator strength

• donor and the 4,6-diphenylpyrimidine fragment. Due to the smaller overlap of the two wavefunctions, a weaker intramolecular charge transfer was attended, enabling to provide an emission in the blue or sky-blue region. Optical properties were evaluated in solution confirming this trend, with an emission

Structure–property relationships and third-order nonlinearities in diketopyrrolopyrrole based D–π–A–π–D molecules

• Jan Podlesný,
• Lenka Dokládalová,
• Oldřich Pytela,
• Adam Urbanec,
• Milan Klikar,
• Numan Almonasy,
• Tomáš Mikysek,
• Jaroslav Jedryka,
• Iwan V. Kityk and
• Filip Bureš

Beilstein J. Org. Chem. 2017, 13, 2374–2384, doi:10.3762/bjoc.13.235

• eventually intramolecular charge-transfer (ICT) [9][10] from the peripheral donors to the central DPP acceptor. Due to their generally D–π–A–π–D character and thus resulting centrosymmetric arrangement, the DPP derivatives were most frequently studied as third-order optical NLOphores, in particular as two