Synthesis of dibenzosuberenone-based novel polycyclic π-conjugated dihydropyridazines, pyridazines and pyrroles

• Ramazan Koçak and
• Arif Daştan

Beilstein J. Org. Chem. 2021, 17, 719–729, doi:10.3762/bjoc.17.61

• absorption and emission maxima values and compounds 3f and 3k, with low conjugation, show the lowest absorption and emission maxima values (Figure 3, Figure 4, and Figure 5). All these molecules (3c–f and 3k) have Stokes shifts greater than 100 nm. The fluorescence quantum yields of 3c–f and 3k were

• shifts, and good fluorescence quantum yields. The dihydropyridazines were oxidized into pyridazines and then converted to pyrroles. Moreover, p-quinone methide derivatives of dibenzosuberenone-based pyridazines and pyrroles were synthesized. We continue intensively to perform various photochemical and

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

• carbazoles was disposed meta or para to the cyano acceptor [19]. OLEDs fabricated using 2,6-2CzBN as the emitter exhibited deep blue emission with λEL = 418 nm and CIE coordinate of (0.15, 0.05); however, due to the low photoluminescence quantum yields (ΦPLs) (28% in 10 wt % DPEPO films) and relatively slow

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

• -containing substituents such as NMe2 possess more electron-donating ability than the S-based moieties such as SMe. Moreover, it was found that NMe2 showed higher luminescence quantum yields (ΦF) in comparison to SMe, indicating that N-substituted groups could enhance the fluorescence intensity. Therefore

• , the π-donor nature of the substituents on the phenyl ring constitutes the main parameter that influences the photophysical properties, such as excited state lifetimes and photoluminescence quantum yields. Hence, a series of highly luminescent materials from deep blue to red emission depending on

• aromatic rings that emit efficiently in very dilute solutions. However, the photoluminescence quantum yields tend to decrease or even fully quench in the aggregated or solid states, due to the well-known effect of aggregation caused quenching (ACQ) [9][10]. This is mainly related to intersystem crossing

Synthesis and characterization of S,N-heterotetracenes

• Astrid Vogt,
• Florian Henne,
• Christoph Wetzel,
• Elena Mena-Osteritz and
• Peter Bäuerle

Beilstein J. Org. Chem. 2020, 16, 2636–2644, doi:10.3762/bjoc.16.214

• (Table 1). Fluorescence quantum yields were far below 1% except for hexacene 22, which showed a very moderate value of 1.9%. This result is in line with the series of S,N-heteroacenes where noticeable fluorescence started with heptacene SN7 (ϕem = 19%) reaching 93% for the longest tridecamer SN13 [17][37

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• chemical yield and enantioselectivity (all values converted to nearest per cent enantiomeric ratio (er) for clarity) will be the common data for comparison; however, where possible the quantum yields of the photochemical reactions will also be provided as this latter metric provides the most accurate

• inefficient initiation step (i.e., Φinitiation << 1) (Equation 1). A less common use of quantum yields by organic synthetic chemists is as a measure of how efficiently the reaction uses the light source. Considering photocatalysis is often purported as a green chemistry because it uses light, a more efficient

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

• with different polarities and showed absorption in the visible region and green-red emission with low quantum yields. The absorption and the emission maxima were shifted bathocromically by increasing the solvent’s polarity. However, there was no correlation with the polarity parameters of the solvents

• of all dyes was high in solvents with low polarities such as PhMe and THF, while it decreased with increasing solvent polarities such as DMSO and MeOH. The fluorescence quantum yields of the dyes were found to be very low as compared to fluorescein (ΦF= 0.95 at pH 9). For example, the quantum yield

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

• with significant Stokes shifts (+60 nm) and quantum yields of 10–32% (Table 1). Theoretical calculations To get insight into the electronic and optical properties of the 2-amino-6-chloro-substituted NDIs, we carried out computational investigations by using the Gaussian 09 program suite [32]. In

• spectrofluorimeter and CD spectra on JASCO J815 spectrophotometer at 25 °C using appropriate 1 cm path quartz cuvettes. For study of interactions with DNA and RNA, aqueous solutions of compounds buffered to pH 5.0 (buffer sodium cacodylate, I = 0.05 mol dm−3) were used. The fluorescence quantum yields were

• determined by the optically dilute method (A < 0.05) by using N,N′-di(n-octyl)-2-chloro-6-n-octylamino-1,4,5,8-naphthalenetetracarboxylic acid diimide (Φfl = 0.58 in CH2Cl2) as standard [25][59]. The reported quantum yields are averaged values obtained at four different excitation wavelengths for each NDI

Et₃N/DMSO-supported one-pot synthesis of highly fluorescent β-carboline-linked benzothiophenones via sulfur insertion and estimation of the photophysical properties

• Dharmender Singh,
• Vipin Kumar and
• Virender Singh

Beilstein J. Org. Chem. 2020, 16, 1740–1753, doi:10.3762/bjoc.16.146

• excellent light-emitting properties with quantum yields (ΦF) up to 47%. Keywords: benzothiophene; β-carboline; metal-free; photophysical properties; sulfur insertion; Introduction The pyrido[3,4-b]indole moiety, commonly referred as β-carboline, is the core unit of about one quarter of all natural

• . The quantum yields were calculated based on Equation 1. where R means reference and S sample, respectively. Generally weak fluorescence emissions were observed for the thiophene-based chromophores due to a remarkable spin–orbit coupling which is originating from the heavy atom effect of sulfur [73][74

• quantum yields (up to 47%), and high brightness (up to 11196). The brightness of the fluorophores was calculated by multiplication of the quantum yield (Φ) with its molar extinction coefficient (ε). In case of the β-carboline C1-substituted benzothiophenones 2aA–nA, 2bB, and 2hB, the substituents R1 and

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

• determined by time correlated single photon counting (TCSPC), indicating low lifetimes of 2.21 ns (for compound 3) and 3.23 ns (for compound 34) for lower populated species (see Figure S6, Supporting Information File 1). Quantum yields (Φ) of both derivatives are below 1% in the solid-state. In chloroform

• maxima at 510 nm and 540 nm (see Figure 3c). However, TCSPC demonstrated that solely fluorescence was observed in all physical states for all investigated compounds with a maximum lifetime τ of 11.6 ns for methylated triazole 45 in chloroform (see Figure 3d). Quantum yields Φ were determined to be <1

• defined up to 8.66 ns for iminium bromide 25, with quantum yields Φ below 1% (see Figure S32, Supporting Information File 1). The absence of any long living triplet species in all fluorene derivatives in solution as well as in the solid-state again indicates undesirable quenching events, induced by the

Development of fluorinated benzils and bisbenzils as room-temperature phosphorescent molecules

• Shigeyuki Yamada,
• Takuya Higashida,
• Yizhou Wang,
• Masato Morita,
• Takuya Hosokai,
• Kaveendra Maduwantha,
• Kaveenga Rasika Koswattage and
• Tsutomu Konno

Beilstein J. Org. Chem. 2020, 16, 1154–1162, doi:10.3762/bjoc.16.102

• bisbenzil molecules cause significant retardation of ISC, leading to a weaker phosphorescence intensity. Additionally, the quantum yields (ΦPL) of the PL bands in the range of 350–600 nm were acquired using an absolute quantum yield measurement system with a calibrated integrating sphere. All samples have a

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

• -transfer (CT) transitions [20]. The PLQY quantum yields of the dilute solutions did not exceed 2%. The dependence of the emission wavelengths of the derivatives on the solvent polarity was also tested. Figure 5 shows the emission spectra of the compounds dissolved in three solvents with increasing

• dilute solutions (10−4–10−5 mol/L) of the compounds were recorded at room (295 K) and low (77 K) temperatures with a luminescence spectrometer Edinburgh Instruments FLS980. Photoluminescence quantum yields (PLQY) of the solutions and thin films of the materials were measured using an integrating sphere

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

• properties such as high hole-transporting mobility [12][25][26][27], pronounced thermal stability [2] and high fluorescent quantum yields [28][29] our attention was focused on carbazole derivatives. In addition to that, carbazole is a rigid aromatic molecule [30] with many different modification sites for

• . This indicates that the excited state dipole moment is much greater than the ground state dipole moment. Quantum yields The relative fluorescent quantum yields (ϕFL) of compounds 7a and 7b were determined in dichloromethane by using rhodamine B (ϕFL = 49% at λexc=355 nm) in ethanol as reference [45

• ) techniques. UV, PL and photoluminescence quantum yields were measured on a Duetta two-in-one fluorescence and absorbance spectrometer from Horiba Scientific. Both absorption and emission solutions for reference and samples had a concentration of 10−6 M. CV measurements were obtained using a CH Instruments

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

• stabilizes the twist conformers stimulating the formation of intermolecular CT states. Consequently, in the PL spectra of neat films of the derivatives the emission band assigned to CT is more prominent. The PL quantum yields of neat films of compound 3, 4, 5, and 6 were found to be 0.03, 0.08, 0.32 and 0.08

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

• functional compounds and materials through the irradiation with light [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. These classes of compounds possess advantageous properties, such as good synthetic accessibility, which allows a broad range of structural modifications and high quantum yields of the

• position of the absorption maximum and the quantum yields or the rate constants of the forward and reverse reaction also depend largely on the solvent polarity as well as on the position and the nature of the substituents either at the indoline or the chromene unit. Surprisingly, there are only a few

• 500 V and 600 V, depending on the fluorescence intensity. The emission spectra were smoothed with the implemented moving-average function by a factor of 5. Emission spectra in the range between 600 nm and 850 nm were corrected with an instrument-specific correction curve. The fluorescence quantum

Bipyrrole boomerangs via Pd-mediated tandem cyclization–oxygenation. Controlling reaction selectivity and electronic properties

• Liliia Moshniaha,
• Marika Żyła-Karwowska,
• Joanna Cybińska,
• Piotr J. Chmielewski,
• Ludovic Favereau and
• Marcin Stępień

Beilstein J. Org. Chem. 2020, 16, 895–903, doi:10.3762/bjoc.16.81

• activation, and a double α-oxygenation. The latter reaction can be partly suppressed for the least reactive systems, providing access to α-unsubstituted boomerangs for the first time. These “α-free” systems are highly efficient fluorophores, with emission quantum yields exceeding 80% in toluene. Preliminary

• bipyrroles are very efficient fluorophores (Table 2), noticeably more emissive than the lactam analogues and the other previously reported boomerangs [32]. Highest fluorescence quantum yields were observed in toluene (83 and 80%, respectively). For comparison, the Φfl values for the lactams cNMI2O and cNMI3O

• fluorescence was only moderately quenched with increasing solvent polarity, and the quantum yields of 64 and 66% were recorded in acetonitrile for cNMI2H and cNMI3H, respectively. To explore the chiral properties of the helically distorted boomerangs, the separation of enantiomers was attempted for all of them

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

• spectrophotometer V-570, and fluorescence spectra were measured with a JASCO PL spectrofluorometer FP-6600. Fluorescence quantum yields were measured on a HAMAMATSU Absolute PL Quantum Yield Measurement System C9920-02G. TLC and gravity column chromatography were performed on Art. 5554 (Merck KGaA) plates and

• spectra of terrylene (black) and TB4 (red) in toluene. λex = 489 nm. Fluorescence intensity reflects the absolute fluorescence quantum yields. MO diagrams of terrylene and TB4 based on calculations at the B3LYP/6-31G(d). UV–vis absorption spectrum of QB4 in toluene. MO diagrams of terrylene and QB4 based

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

• , while the emission quantum yields of the β-ethynylated derivatives are significantly lower than those of α-ethynylated ones. The current method should be useful for fine-tuning of the photophysical properties of BODIPY dyes as well as for constructing BODIPY-based building cores for functional π

• fluorescence quantum yields of 3a and 4a remain high (Φf = 0.95 and 0.56, respectively) and are comparable to that of 1a (Table 1). The smaller Stokes shift values of ≈178 cm−1 and longer emission lifetimes of ≈7.83 ns indicate the rigid scaffolds of α,α-disubstituted 4a in the excited state. In the case of β

• emission bands were observed with lowered quantum yields, Φf of 0.25 and 0.16, respectively (Figure 5b and Table 1). The larger Stokes shift and shorter emission lifetime suggest a rapid decay of the excited species after structural relaxation (vide infra, Table 1). Also, intersystem crossing to the

Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0

• Bernd Strehmel,
• Christian Schmitz,
• Ceren Kütahya,
• Yulian Pang,
• Anke Drewitz and
• Heinz Mustroph

Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40

• . Moreover, structures based on IV and V additionally provided absorbers with fluorescence quantum yields of up to 20% yield. Cyanines comprising at the meso-position either a phenyl or phenoxy group resulted in a Φf of about 15–20% (derivatives comprising PhO-: 14, 15, 22, and 30; derivatives comprising Ph

• -: 18 – 20, 23, 25, 28, 31, and 32). Absorbers with a barbiturate group at the same position resulted in fluorescence quantum yields between 10–16% (compare 24, 26, 27, 29, 33, 34, 42, 43, 47–51). Diphenylamino substitution at the meso-position showed a slight decrease of Φf (compare 35). Replacement

• with thiol moieties such as phenylmercapto and phenylmercapto-tetrazole substituents resulted in Φf of 7% (compare 64–68) and 3% (compare 78), respectively. Thus, one can roughly draw the following order for the decrease fluorescence quantum yields located at the meso-position: PhO-; Ph- ≥ barbiturate

Synthesis and circularly polarized luminescence properties of BINOL-derived bisbenzofuro[2,3-b:3’,2’-e]pyridines (BBZFPys)

• Ryo Takishima,
• Yuji Nishii,
• Tomoaki Hinoue,
• Yoshitane Imai and
• Masahiro Miura

Beilstein J. Org. Chem. 2020, 16, 325–336, doi:10.3762/bjoc.16.32

• diluted CHCl3 solutions (1.0 × 10−5 M) and in the solid states. The quantum yields of these molecules were around 0.15 in solution, which is typical for binaphthyl compounds [47]. In contrast, 4a–c as well as 6 exhibited fluorescence at around 390 nm in solution, with relatively higher quantum yields of

Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations

• Rafia Siddiqui and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26

• benzene are difficult to oxidize with nonphotochemical processes, whereas with photoredox catalyst 5 and TBN in the presence of oxygen, benzene can be easily be oxidized (Scheme 19) [158]. Remarkably, photoredox catalyst 5 offered a one-step oxygenation of arenes to phenol with high quantum yields. It was

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

• emission intensity of 3d was too low to identify a maximum, as usually observed with nitro-substituted fluorophores. Unfortunately, the emission quantum yields of 3a–c could not be determined in water because of the compounds’ tendency to dimerize even at very low concentrations (see below). Overall, the

Design, synthesis and investigation of water-soluble hemi-indigo photoswitches for bioapplications

• Daria V. Berdnikova

Beilstein J. Org. Chem. 2019, 15, 2822–2829, doi:10.3762/bjoc.15.275

• , the photoisomerization quantum yields as well as the half-lifes of the photoinduced forms appeared to be almost independent of the presence of the alkylamino substituent. Interestingly, a comparison with the data obtained for Z-2 in aqueous 10 mM Na-phosphate buffer containing 0.1 M NaCl, pH 7.0 [12

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• the quantum yield of the photoisomerization reaction (λex = 365 nm) [40]. For solutions of 1E in the absence and presence of Ca2+, the measured quantum yields were identical (0.08) suggesting that the ion does not influence the efficiency of the photoreaction. In order to unambiguously prove the

• switching in terms of quantum yields (0.08) and PSS composition (88% cis). The calcium binding affinity of the cis-form was diminished by circa 2.5-fold with respect to the trans-form as the chelator was stretched rendering the binding pocket ill-adapted to accommodate the calcium, as suggested by molecular

• spectrofluorometer fitted with a PMT detector and exciting with a 450 W Xe lamp across a double monochromator, and were corrected for instrumental response. Photoreaction quantum yields were determined upon excitation at 365 nm using the couple potassium ferrioxalate–phenanthroline as a chemical actinometer on an

Dyes in modern organic chemistry

• Heiko Ihmels

Beilstein J. Org. Chem. 2019, 15, 2798–2800, doi:10.3762/bjoc.15.272

• as high molar extinction coefficients and emission quantum yields. Along these lines, numerous new methods and synthetic routes were developed to either functionalize established dye cores or to design new classes of dyes [13][14]. To add to that, efforts were spent to isolate and identify dyes that

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• ] is accompanied by large variations in their absorption spectra. However, azobenzenes remain one of the most popular photoswitches owing to their stability, reliability and tunability: azobenzenes provide high extinction coefficients and quantum yields, allowing switching between Z- and E-isomers with

• the differences observed, differences in the excited-state profiles and quantum yields for the photoisomerization pathway may also contribute to the lack of correlation between band overlap and photoisomerization efficiency [35]. Conclusion We aimed to combine two features now known to significantly