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

• absorption maxima (λabsmax), oscillator strengths (f), and relevant transitions and their contributions (w) are given in Table 1 and Table S1 in Supporting Information File 1). The shifts of the absorption maxima of the dyes were little dependent on the solvent polarity and there was no obvious correlation

Recent synthesis of thietanes

• Jiaxi Xu

Beilstein J. Org. Chem. 2020, 16, 1357–1410, doi:10.3762/bjoc.16.116

• -donating substituents present in the allenes enhanced the overall reaction rate. There was little effect of the solvent polarity on the reaction rate. The formation of thietanes involved the excited triplet thiones and the π-bond of allenes [66]. In 1984, Bos and co-workers realized the photocycloaddition

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

• polarities, i.e., toluene (0.099), tetrahydrofuran (0.207) and dimethylformamide (0.4) (values in parentheses are the solvent polarities relative to water) [21]. The PL spectra of the solutions of compound 3 appeared to be solvent-polarity independent as only the structured emission band of the locally

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

• microscopic solvent polarity [43][44], ET(30), increased from toluene to dimethyl sulfoxide (see also Table 3). A 141 nm red-shift was observed for 7a (from 465 nm to 606 nm) and an 86 nm red-shift was observed for 7b (from 423 nm to 509 nm). In comparison for 7b, this red-shift was more pronounced for 7a

Suzuki–Miyaura cross coupling is not an informative reaction to demonstrate the performance of new solvents

• James Sherwood

Beilstein J. Org. Chem. 2020, 16, 1001–1005, doi:10.3762/bjoc.16.89

• Supporting Information Supporting Information File 292: Synthetic procedures and calculation of reaction conversions and solvent polarity data. Funding This research was funded by the Bio-Based Industries Joint Undertaking (JU) under the European Union's Horizon 2020 research and innovation programme

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

• 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

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

• 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

Aldehydes as powerful initiators for photochemical transformations

• Maria A. Theodoropoulou,
• Nikolaos F. Nikitas and
• Christoforos G. Kokotos

Beilstein J. Org. Chem. 2020, 16, 833–857, doi:10.3762/bjoc.16.76

• state quencher, as well as by the lowered rate of the reaction in the presence of the triplet energy quencher 2,5-dimethylhexa-2,4-diene or pyridazines, additives with lower triplet state energies than 4-anisaldehyde (52). The fact that the solvent polarity did not affect the sensitivity of the process

Emission solvatochromic, solid-state and aggregation-induced emissive α-pyrones and emission-tuneable 1H-pyridines by Michael addition–cyclocondensation sequences

• Natascha Breuer,
• Irina Gruber,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2019, 15, 2684–2703, doi:10.3762/bjoc.15.262

• with increasing solvent polarity in a range from green fluorescence (529 nm) in toluene to red fluorescence in DMSO (638 nm) (Figure 12). The observed positive emission solvatochromism is a consequence of a significant change in the dipole moment from the electronic ground to the vibrationally relaxed

• , and 6g recorded in dichloromethane at T = 298 K. Absorption (top) and fluorescence (bottom) of compound 6c with variable solvent polarity (left to the right: toluene, ethyl acetate, acetone, DMF and DMSO, c(6c) = 10−4 M; λexc = 365 nm, handheld UV lamp). Absorption (solid lines) and emission (dashed

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

• 2,1,3-benzothiadiazole (BTD) core and its derivatives that are successfully applied in bioimaging experiments. (Left) UV–vis, (center) fluorescence emission and (right) solvatochromic effect (Stokes shift in wavenumbers versus solvent polarity in ETN) of the synthesized BTD-4APTEG (10 μM for all

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

• emission maximum on changing to the polar solvent (Δλ = +7 nm). However, dye 19 features a solvatofluorochromic effect of Δλ = +41 nm under the same conditions. The dyes 16 and 18 show somewhat smaller bathochromic shifts on increasing the solvent polarity (Δλ = +20–22 nm). Regarding the 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

• interactions will be probed with NR. Dipole moments With increasing solvent polarity, the maxima in the fluorescence spectra of NR in liquid solvents at 25 °C were observed to gradually shift to the red, from 17660 cm−1 in nonpolar n-hexane to 16090 cm−1 in polar acetonitrile, showing no indication of dual

• (μe) than that in the ground state (μg). To calculate the value of μe, the frequencies of emission (νf) and absorption (νa) are plotted [39][42] in Figure 3a against the Lippert solvent polarity function f(ε) − f(n2) [43], where ε is the dielectric constant and n is the refractive index of the solvent

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• isomerization occurs on a fast <1 ps timescale in both toluene and acetonitrile, while the excited state lifetime of the Z-form depends on solvent polarity, suggesting a partial charge transfer nature of its low lying excited state. Time-resolved luminescence measurements evidence the presence of a main

• solvent polarity. On the contrary, the excited state lifetime of the Z-isomer depends on the solvent properties and is especially short in MeOH, suggesting that the excited state of the molecule could have a partial charge transfer nature. Finally, transient absorption spectroscopy was employed as an

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• 504 nm in toluene, while a hypsochromic shift of 14 nm was observed in acetonitrile. This influence of solvent polarity was detected for all ligands [39]. The carbonyl group in the ethene bridge of 3 causes a significant bathochromic shift (68 nm in toluene) of the closed-ring isomer maximum in

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• illustrated the way of utilizing different types of noncovalent interactions including hydrogen bonding, halogen and chalcogen bonding for the selective detection of anions by triazolium macrocycles. The selectivity and the ability of detection of anions are highly dependent on the solvent polarity. We have

A golden opportunity: benzofuranone modifications of aurones and their influence on optical properties, toxicity, and potential as dyes

• Joza Schmitt and
• Scott T. Handy

Beilstein J. Org. Chem. 2019, 15, 1781–1785, doi:10.3762/bjoc.15.171

• at the 5-position resulted in a shift to longer wavelength by roughly 20 nm compared to a methoxy substituent at the 4-position and a strong dependence upon solvent polarity. While this shift was quite reasonably attributed to the inductive effect of the oxygen, no other substitution was studied

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

• characteristic band of the (D–π–)2A fluorescent dyes show bathochromic shifts in the order of OUY-2 < OUK-2 < OUJ-2. Moreover, the photoabsorption bands of the (D–π–)2A fluorescent dyes are nearly independent of solvent polarity, while the fluorescence bands showed bathochromic shifts with increasing solvent

• < OUJ-2, which is in agreement with the increase in the electron-withdrawing ability of the azine ring in the order of pyridyl group < pyrazyl group < triazyl group. The photoabsorption spectra of the three dyes are nearly independent of solvent polarity. This indicates that the electronic and

• structural characteristics of both the ground and Franck–Condon (FC) excited states do not differ much with a change in solvent polarity. The molar extinction coefficient (εmax) for the ICT band is ca. 100000 M−1 cm−1 for OUY-2, 75000 M−1 cm−1 for OUK-2 and 80000 M−1 cm−1 for OUJ-2. The corresponding

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

• , respectively, by plotting the maximum emission wavenumbers of 2,6-TNS/1,8-ANS in a set of solvents as a function of solvent polarity ET(30) (Figure 1e and 1f). ET(30) values for the involved solvents (water, methanol, ethanol, propanol, butanol, glycerol and ethylene glycol) and the maximum emission

• point on the titration curve indicates a 1:1 binding stoichiometry between GC5A and P-TPE. Ka was fitted according to a 1:1 binding model giving a value of (8.4 ± 1.1) × 107 M−1 (Figure 2b, Table 1). The emission wavelengths of classical AIEgens are scarcely affected by solvent polarity, which is a

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• methanol-d4. The conformational preference was affected neither by the solvent polarity nor the halogen size, suggesting the presence of strong stereoelectronic effects being responsible for the conformational behavior in these systems. Theoretical calculations are in agreement with experimental data, the

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• dipole moments and, consequently, the conformer populations are expected to change with the solvent polarity [29]. Indeed, the 1H NMR outcomes in C6D12 (dielectric constant ε = 2.2), CDCl3 (ε = 4.8) and C5D5N (ε = 12.4) solutions are informative on the rotation of H–C2–C1–F and conformational equilibrium

• 1C is not expected when the solvent varies, because of their similar molecular dipole moments. In turn, the populations of conformer 1A are not prone to increase by increasing the solvent polarity, because of their smaller molecular dipole moments compared to 1B and 1C. So, the observed changes in

• Ishikawa´s reagent. In addition, this equilibrium shifts from 1Ab to 1Cc when increasing the solvent polarity. These findings are in complete agreement with the conformational energy data provided in Table 2, which were obtained from high level DFT calculations (1Cb is not a minimum-energy conformer). The

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

• increases with the increase of solvent polarity. Additionally, X-ray analysis of 2,6-diazidopurine 2'-deoxyribonucleoside revealed the exclusive existence of the azido tautomer in the solid state [41]. The discovered ability of the azido group to be substituted with amines at C(2) position was used for the

• showed pronounced changes with solvent polarity in terms of emission maxima and quantum yields, though the absorption spectra showed minor or no changes with increasing solvent polarity indicating small dipole moment in the ground state. A good linear correlation between the fluorescence QY and the

• same solvents (Table 4). Non-linear dependency in increase of emission maxima is observed (Table 4) with increasing polarity parameter (ET(30)), thus indicating that the sensitivity to solvent polarity is not the only major solute–solvent interaction and the emission maxima are also influenced by other

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• liquid layer could be recycled for further reactions. More interestingly, the catalytic ability of 1 increased nearly four times the reaction using DMF as solvent. This was consistent with the Hughes–Ingold prediction of solvent polarity effects on reaction rates [111]. We also developed a visible-light

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

• properties. Indeed, bathochromic shifts in the emission energy were observed upon either grinding or incrementing solvent polarity. This emission was attributed to a radiative transition with triplet metal–metal-to-ligand charge transfer character (3MMLCT), which ultimately strongly depends on the platinum

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• , for the cycloaddition of the structurally similar ethyl phenylpropiolate in various solvents only a small decrease of the bimolecular rate constant with increasing solvent polarity (in terms of relative permittivity) was observed excluding a transition state having a polarized character. Finally

• , substitution effects in the 3-(4-substituted phenyl) group of sydnones were studied and a relatively low Hammett reaction constant ρ ≈ +0.8 was estimated from four derivatives (MeO, Me, H and Cl). An even smaller dependence of the rate constants on the solvent polarity and substituent effect sensitivity (ρ

Regioselective decarboxylative addition of malonic acid and its mono(thio)esters to 4-trifluoromethylpyrimidin-2(1H)-ones

• Sergii V. Melnykov,
• Andrii S. Pataman,
• Yurii V. Dmytriv,
• Svitlana V. Shishkina,
• Mykhailo V. Vovk and
• Volodymyr A. Sukach

Beilstein J. Org. Chem. 2017, 13, 2617–2625, doi:10.3762/bjoc.13.259

• , unique heterocyclic ketimines, react with malonic acid under organic base catalysis to regioselectively provide either Michael- or Mannich-type decarboxylative addition products depending on solvent polarity. Malonic mono(thio)esters give exclusively Michael-type products. The two regioisomeric products

• supported by the known effect of solvent polarity on the decarboxylation rate of malonic acid derivatives which was claimed to be faster in polar media [40]. To study the substrate scope of the regioselective additions of malonic acid, we introduced substituted pyrimidones 2b–m in the reaction and performed

• . Presumably, in this case, the kinetically controlled Michael-type intermediate C is even far more prone to decarboxylation than the dicarboxylate intermediate A (Table 1) and hence, the reaction is sufficiently regioselective irrespective of the solvent polarity (Table 3, entries 1, and 6–9). Performing the