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

• permittivity of polymers and its spatial distribution play a crucial role in the behavior of thin films, such as those used, e.g., as sensor coatings. In an attempt to develop a conclusive approach to determine these quantities, the polarity of the model polymer poly(methyl methacrylate) (PMMA) in 600 nm thin

• 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

• NR molecules in the ground state and slow sub-glass transition (Tg) relaxations in PMMA. Keywords: charge transfer; dipole moment; fluorescence; inhomogeneous broadening; oxazine dye; polarity probe; polymer permittivity; Introduction The chain and segment mobility as well as the permittivity of

Indium-mediated C-allylation of melibiose

• Christian Denner,
• Manuel Gintner,
• Hanspeter Kählig and
• Walther Schmid

Beilstein J. Org. Chem. 2019, 15, 2458–2464, doi:10.3762/bjoc.15.238

• Zemplén-deprotection and ozonolysis compound 4-anti was obtained. Purification at this stage utilizing conventional column chromatography was not feasible due to the high polarity of the obtained compound mixture, which contained pyranoid as well as furanoid isomers in their α,β-forms. Thus, per-O

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

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• reversibly between two states comprising high amounts of (E)-11 and (Z)-11, respectively. The other part of the hypothesis was, that by this photoinduced isomerization a considerable drop of activity would occur due to the conformational change and the resulting changed geometry and polarity. However, this

• after irradiation, we would have predicted, that at least the significant difference in polarity of (E)-11 and (Z)-11 should lead to marked differences of sirtuin engagement in vitro. However, recent results from a carefully designed azologization study performed by Rustler et al. led to comparable

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

• chemistry. Different hydrogen bond donors such as pyrrole N–H and benzene C–H along with the triazolium C5–H have been successfully incorporated within a single macrocyclic framework. The complex formation of anions with the hydrogen bond donors varied according to the polarity of the solvent. It was found

• that the binding constants for interaction with monoanions become smaller as the polarity of the solvent medium increases on moving from acetonitrile to methanol. Among all of the tested anions, macrocycle 10 has shown a high selectivity for pyrophosphate HP2O73−, and tetrahedral oxyanions HSO4−, H2PO4

• 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

Archangelolide: A sesquiterpene lactone with immunobiological potential from Laserpitium archangelica

• Silvie Rimpelová,
• Michal Jurášek,
• Lucie Peterková,
• Jiří Bejček,
• Vojtěch Spiwok,
• Miloš Majdl,
• Michal Jirásko,
• Miloš Buděšínský,
• Juraj Harmatha,
• Eva Kmoníčková,
• Pavel Drašar and
• Tomáš Ruml

Beilstein J. Org. Chem. 2019, 15, 1933–1944, doi:10.3762/bjoc.15.189

• domain between the helices 3, 5 and 7 [7][21]. Comparing the polarity of these compounds with compound 1 based on the formation of hydrogen bonds, the most polar compound capable of forming the highest number of hydrogen bonds is thapsigargin, the least polar is compound 1 (for details, see Supporting

Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

• Jing Li,
• Qiang Shi,
• Ying Han and
• Chuan-Feng Chen

Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173

• different polarity can also affect the complexation between the hosts and the guests. As shown in Table 2, we found that performing the 1H NMR titrations of the host–guest complexation in CDCl3/acetone-d6 1:2 (v/v), the Ka values of the 1:1 host–guest complexes were about 103 M−1 except for H2 that showed

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

• polarity (i.e., positive fluorescence solvatochromism). The Lippert–Mataga plots for OUY-2, OUK-2 and OUJ-2 indicate that the Δμ (= μe − μg) value, which is the difference in the dipole moment of the dye between the excited (μe) and the ground (μg) states, increases in the order of OUY-2 < OUK-2 < OUJ-2

• < 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

Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

• Stiliyana Pereva,
• Valya Nikolova,
• Silvia Angelova,
• Tony Spassov and
• Todor Dudev

Beilstein J. Org. Chem. 2019, 15, 1592–1600, doi:10.3762/bjoc.15.163

• structures possessing less elaborate hydrogen bond networks (compare ΔH1/ΔH78 for reaction 2 with those of reactions 1 and 3 in Table 1). Generally, increasing the polarity of the medium (higher dielectric constant) attenuates the energies of complex formation although the enthalpies remain negative. Adding

Transient and intermediate carbocations in ruthenium tetroxide oxidation of saturated rings

• Manuel Pedrón,
• Laura Legnani,
• Maria-Assunta Chiacchio,
• Pierluigi Caramella,
• Tomás Tejero and
• Pedro Merino

Beilstein J. Org. Chem. 2019, 15, 1552–1562, doi:10.3762/bjoc.15.158

• tetrahydrothiophene reflects the same situation, but to a greater degree (Figure 3B). Interestingly, the ELF analyses evidence the high polarity of Ru–O bonds by assigning about 7e to the oxygen atoms. Because of this, during the reaction coordinate an increase of only 1e is assigned to Ru for which about 12e (coming

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

• ], constructing supramolecular dye lasers [18][19], protecting fluorophores from photodegradation [20][21] and manufacturing organic luminescent materials [22][23][24]. Also, variations of luminescence have been utilized to obtain information about the hydrophobicity, polarity, and polarizability of the inner

• -accepting structures. An increase in charge separation within ICT probes would occur upon excitation which results in a larger dipole moment in the excited state. The energy of the excited state with a larger dipole moment could be reduced by interaction with a high polarity environment and could be

• elevated by interaction with non-polar environment. Thus, the S1–S0 energy gap increases as the polarity decreases resulting in a blue-shifted emission in a hydrophobic environment. Their pronounced solvatochromic effect makes them perfect environmental sensitive probes. 1,8-ANS and 2,6-TNS are essentially

Robust perfluorophenylboronic acid-catalyzed stereoselective synthesis of 2,3-unsaturated O-, C-, N- and S-linked glycosides

• Madhu Babu Tatina,
• Xia Mengxin,
• Rao Peilin and
• Zaher M. A. Judeh

Beilstein J. Org. Chem. 2019, 15, 1275–1280, doi:10.3762/bjoc.15.125

• over a shorter reaction time (Table 1, entries 4 vs 3). Under the same conditions, the reaction did not proceed in THF or DCM due to the lower polarity of these solvents in comparison to CH3CN and CH3NO2 (Table 1, entry 2 vs 3 and 4). Attempts to reduce the amount of perfluorophenylboronic acid to 5

Self-assembly behaviors of perylene- and naphthalene-crown macrocycle conjugates in aqueous medium

• Xin Shen,
• Bo Li,
• Tiezheng Pan,
• Jianfeng Wu,
• Yangxin Wang,
• Jie Shang,
• Yan Ge,
• Lin Jin and
• Zhenhui Qi

Beilstein J. Org. Chem. 2019, 15, 1203–1209, doi:10.3762/bjoc.15.117

• CHCl3/MeCN (v/v = 2:1), were recorded to investigate its self-assembly behavior. Figure 1a shows the UV–vis absorption spectra of 1 in solvents with different polarity. The spectrum of 1 in the less polar solvent CHCl3 shows a well-resolved vibronic structure (0–0, 0–1, and 0–2 transitions of PDI

• observed but with an overall hypsochromic shift (Figure 1c). The aggregation of 2 also takes place in the solvents with high polarity, such as MeOH and H2O, in which 2 shows weak or even no UV–vis absorption. Similar to 1, 2 also shows a strong fluorescence in CHCl3 and mixed CHCl3/MeCN (v/v = 2:1, Figure

• were investigated. As shown in Figure 2a, micelle-like assemblies of 1 were observed, while, because of the higher polarity of MeCN, the aggregation of 1 through π–π stacking was considerably enhanced forming linear assemblies (Figure 2b). Interestingly, when imposed to an aqueous medium through adding

Insertion of [1.1.1]propellane into aromatic disulfides

• Robin M. Bär,
• Gregor Heinrich,
• Martin Nieger,
• Olaf Fuhr and
• Stefan Bräse

Beilstein J. Org. Chem. 2019, 15, 1172–1180, doi:10.3762/bjoc.15.114

• disulfides used in this reaction to 10a and 10e (Scheme 6). With the bigger difference in polarity of the substituents, the products 6a, 16 and 6e could be separated by column chromatography and preparative TLC. Again, we observed a deviation from the expected product ratio. This leads to the assumption that

• similar polarity. However, the reaction conditions can be tuned to obtain solely the BCP compound in high yields. By mixing two aromatic disulfides in this reaction three different products can be obtained, with the unsymmetrically substituted compound as the main product. This method will become

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• inclusion guest (1,4-dioxane), the lattice solvent molecules, regardless of their polarity, insert between two N-hexyl arms using an OH/CH···Br− hydrogen bond (Figure 2) [32]. To better understand whether this is fundamental to these systems, or a result of the enforced geometry caused by the included guest

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

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• photo-induced trans–cis isomerization representing the time of birth of the azobenzene photoswitch. Benefiting of their accessible synthesis, large change in polarity and geometry upon switching, excellent photochromic properties and tuneability, azobenzenes are amongst the most widely used photochromic

Tuning the stability of alkoxyisopropyl protection groups

• Zehong Liang,
• Henna Koivikko,
• Mikko Oivanen and
• Petri Heinonen

Beilstein J. Org. Chem. 2019, 15, 746–751, doi:10.3762/bjoc.15.70

• slightly more acidic than the 5’-hydroxy group, but absolute values for the acidity constants could not be reliably determined. The hydrolysis of the acetals is suggested to follow most often the A-1 mechanism via formation of an oxocarbenium ion [11]. Polarity effects and the stability of the formed

• directly reflected by the observed hydrolysis rate, whereas the changes in polarity of the leaving alcohol do not give marked changes on the rate. The latter is due to the fact that the kinetic effects on the protonation step and the leaving group ability largely cancel each other. In our study, the

• was shown to be 4 minutes in methanol and 7 minutes in acetonitrile. The polarity of the solvent has a significant effect on the stability. Slower reactions were observed using 3% acetic acid in dioxane, where the half-lives for 4a and 4c were 80 minutes and 5 minutes, respectively. These results

Synthesis and SAR of the antistaphylococcal natural product nematophin from Xenorhabdus nematophila

• Frank Wesche,
• Hélène Adihou,
• Thomas A. Wichelhaus and
• Helge B. Bode

Beilstein J. Org. Chem. 2019, 15, 535–541, doi:10.3762/bjoc.15.47

• ) could be observed for at least MSSA. This observation may correlate to the molecular polarity, and thus hydrophilicity of the cyclic moiety, whereas almost all hydrophobic moieties showed good antistaphylococcal activity as seen for naphthyl (4 and 5) and indene (6). However, the increase of

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

• polarity plays a significant role in the condensed phase. Thus, it is appropriate to study the conformations of Ishikawa´s reagent in different media, of low and high polarity. This is a challenging task, since the conformational analysis of flexible acyclic organic compounds using NMR SSCCs is more

• 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

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

• was studied in detail in solvents of different polarity (THF, CHCl3, DMSO, MeCN and MeOH). The study was performed on two model compounds, 8c from the purine class and 11c from the 7-deazapurine class (Figure 5 and Figure 6). As illustrated in Figure 5 and Figure 6 the emission of compounds 8c and 11c

• 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