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

• 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

• significantly decreased with the geometry relaxation at the S1 state compared to that of the S0-state structure, which could be the origin of the large Stokes shift for 6a. Therefore, in comparison with the α-substituted compounds 3a and 4a, the less emissive character of the β-ethynyl-substituted derivatives

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

• ) λmax [nm] (ε [L·mol−1·cm−1]): 274 (32000), 321 (18100), 428 (10000); emission (CH2Cl2) λmax [nm] (Stokes shift [cm−1]): 565 (5700); quantum yield (CH2Cl2) Φf: 0.01; Anal. calcd for C23H17F3N2O2 (410.1): C, 67.31; H, 4.18; N, 6.83; found: C, 67.50; H, 4.32; N, 6.70. Typical procedure for the

• ), 924 (w), 853 (m), 818 (s), 795 (m), 750 (m), 748 (m), 692 (s), 669 (m), 640 (m); UV–vis (CH2Cl2) λmax [nm] (ε [L·mol−1·cm−1]): 294 (18800), 482 (47300); emission (CH2Cl2) λmax [nm] (Stokes-shift [cm−1]): 567 (3100); quantum yield (CH2Cl2) Φf: 0.99; emission (solid) λmax [nm]: 694; quantum yield (solid

• ), 1248 (s), 1188 (w), 1169 (m), 1134 (m), 1113 (s), 1092 (m), 1067 (m), 1047 (m), 1028 (w), 1001 (w), 885 (m), 854 (m), 847 (w), 775 (w), 758 (s), 746 (m), 694 (m), 658 (w); UV–vis (CH2Cl2) λmax [nm] (ε [L·mol−1·cm−1]): 274 (20300), 324 (20100), 417 (7700); emission (CH2Cl2) λmax [nm] (Stokes shift [cm−1

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

• 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

• 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

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• compounds were nonemissive. The Stokes shift of the OFs of nonoxidized DAEs was always ca. 6000 cm−1, independent of the substitution pattern. For comparison, this value was much lower than the Stokes shift of the OF of compound 6 (10,700 cm−1) [4]. The Stokes shift of the CFs of oxidized DAEs varied

• between 3000 cm−1 and 5600 cm−1, which is comparable with the Stokes shift observed for the CF of 6 (4600 cm−1) [4]. In the case of oxidized DAEs, asymmetric compounds possessed higher Stokes shifts by ca. 1000 cm−1 than symmetric DAEs. Only compound AsOTh2 has a higher Stokes shift than the CF of

Aggregation-induced emission effect on turn-off fluorescent switching of a photochromic diarylethene

• Luna Kono,
• Yuma Nakagawa,
• Ayako Fujimoto,
• Ryo Nishimura,
• Yohei Hattori,
• Toshiki Mutai,
• Nobuhiro Yasuda,
• Kenichi Koizumi,
• Satoshi Yokojima,
• Shinichiro Nakamura and
• Kingo Uchida

Beilstein J. Org. Chem. 2019, 15, 2204–2212, doi:10.3762/bjoc.15.217

• is one of the examples which express the mechanisms of aggregation-induced emission (AIE). This compound emits orange fluorescence with a large Stokes shift derived from ESIPT in aprotic solvents such as THF or hexane, while it exhibits only a photochromic reaction in protic solvents such as methanol

• a large Stokes shift is indispensable for such a system. One of the possible choices to achieve such a large Stokes shift is to introduce the excited-state intramolecular proton transfer (ESIPT). The process of ESIPT is a fast process even comparable to the internal conversion [15][16]. This is

• because the proton transfer occurs through an intramolecular hydrogen bond. This is also an origin of a large Stokes shift (8,000–11,000 cm−1) in the emission from the ESIPT state. Consequently, yellow luminescence was observed by UV-excitation [17][18]. Mutai et al. reported an ESIPT luminescence of an

Naphthalene diimides with improved solubility for visible light photoredox catalysis

• Barbara Reiß and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201

• have only little influence on the optical properties but significantly modulate the solubility in DMF. This result agrees with other cNDIs in literature [47][48][58]. NDI 1 shows weak fluorescence in CH2Cl2 with a maximum at 384 nm and a quantum yield of 7%. The Stokes’ shift is small (413 cm−1). Based

• quantum yield of 48%. The Stokes’ shift is rather large (715 cm−1). The excitation energy E00 of cNDI 6 in the singlet state is approximately 1.98 eV and is significantly smaller than that of NDI 1 due to the visible light excitation which delivers less energy to the excited state. The redox potentials of

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• ] or its 4-isomer, as optimal fluorescent light-up probes characterized by high fluorimetric response (I/I0 of up to 550-fold), excellent selectivity with respect to double-stranded DNA or single-stranded RNA controls, high quantum yield in the presence of G4 analytes (up to 0.32), large Stokes shift

• the design of G4-based logic gates could also be envisaged. Taking into account the favorable optical properties, in particular high brightness and large Stokes shift, the same probes could be utilized to proceed to cellular imagining of G4 structures, certainly with caution regarding the inherent

• acid samples used in the first screening round. Optical parameters (absorption and emission maxima, Stokes shift, molar absorptivity coefficient at the absorption maximum, fluorescence quantum yield and brightness) of dyes 1p, 1u, 17a and 18a in the absence of DNA or in the presence of G4-DNA

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

• . Therefore, the fact explains our findings that OUJ-2 shows large bathochromic shifts of the fluorescence maxima in polar solvents, as well as the Stokes shift values of OUJ-2 in polar solvents are much larger than those in nonpolar solvents. The cyclic voltammetry of OUY-2, OUK-2 and OUJ-2 demonstrated that

• , the three dyes showed a bathochromic shift of the fluorescence band with increasing solvent polarity from toluene to DMF (i.e., positive fluorescence solvatochromism). Thus, the Stokes shift (SS) values of the three dyes increase with increasing solvent polarity. Compared with OUY-2, OUK-2 and OUJ-2

• can easily be evaluated from the slope of a plot of νst against Δf (the Lippert–Mataga plot), where νst is the Stokes shift (Table 1), ε0 is the vacuum permittivity, h is Planck’s constant, c is the velocity of light, a is the Onsager radius of the dye molecule (7.81 Å, 7.99 Å and 7.91 Å for OUY-2

Diaminoterephthalate–α-lipoic acid conjugates with fluorinated residues

• Leon Buschbeck,
• Aleksandra Markovic,
• Gunther Wittstock and
• Jens Christoffers

Beilstein J. Org. Chem. 2019, 15, 981–991, doi:10.3762/bjoc.15.96

• NH2 and NHBoc group is the most electron-deficient one with absorption and emission wavelength at 408 nm and 487 nm, respectively (Stokes shift ca. 80 nm). A bathochromic shift of 16 nm of both, absorption and emission wavelengths, is achieved by introduction of a benzyl residue at one nitrogen atom

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

• development does not allow yet to introduce arylamino moieties at C(2) due to the diminished nucleophilicity of anilines. The 7-deazapurine derivatives were characterized with a somewhat larger Stokes shift and bathochromic shift of the lowest energy absorption band in comparison to purine derivatives, but

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• observed upon duplex formation with DNA or RNA. The fused ring fluorescence cytosine analogue 5,6-benzo-pC gave a large Stokes shift (113 nm) and good quantum yield (0.79) as a monomer. Unfortunately, severe fluorescence quenching was observed upon incorporation of this monomer into PNA sequences and no

Development of a fluorogenic small substrate for dipeptidyl peptidase-4

• Futa Ogawa,
• Masanori Takeda,
• Kanae Miyanaga,
• Keita Tani,
• Ryuji Yamazawa,
• Kiyoshi Ito,
• Atsushi Tarui,
• Kazuyuki Sato and
• Masaaki Omote

Beilstein J. Org. Chem. 2017, 13, 2690–2697, doi:10.3762/bjoc.13.267

• quantum yield to 0.03. In spectroscopic terms, the fluorescence emission peaks of these compounds red-shifted with increasing TFPE substitution. Additionally, a large Stokes shift was observed for 1, which is important in view of the biomedical use of fluorescent compounds. Next, we changed the solvent

One-pot syntheses of blue-luminescent 4-aryl-1H-benzo[f]isoindole-1,3(2H)-diones by T3P^® activation of 3-arylpropiolic acids

• Melanie Denißen,
• Alexander Kraus,
• Guido J. Reiss and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2017, 13, 2340–2351, doi:10.3762/bjoc.13.231

• vibrationally relaxed excited state. This is even more the case in the nearly perfect linear correlation of the Stokes shift with σR (r2 = 0.989) and can be interpreted as a significant structural change upon photonic excitation and excited state relaxation resulting from a considerable charge transfer

Synthesis and application of trifluoroethoxy-substituted phthalocyanines and subphthalocyanines

• Satoru Mori and
• Norio Shibata

Beilstein J. Org. Chem. 2017, 13, 2273–2296, doi:10.3762/bjoc.13.224

• strong, and the Stokes shift is small, about 10 nm. On the other hand, metal-free trifluoroethoxy-substituted phthalocyanine (TFEO-H2Pc) shows a split in the Q band due to its low symmetry [47]. In metal-free phthalocyanine, the four pyrrole units in the center of the macrocycle have two protons

BODIPY-based fluorescent liposomes with sesquiterpene lactone trilobolide

• Ludmila Škorpilová,
• Silvie Rimpelová,
• Michal Jurášek,
• Miloš Buděšínský,
• Jana Lokajová,
• Roman Effenberg,
• Petr Slepička,
• Tomáš Ruml,
• Eva Kmoníčková,
• Pavel B. Drašar and
• Zdeněk Wimmer

Beilstein J. Org. Chem. 2017, 13, 1316–1324, doi:10.3762/bjoc.13.128

• and fluorescence spectra of compounds 3–6. UV spectra (part A) were recorded with a concentration of 10 μM in DCM and fluorescence spectra (part B) with a concentration of 0.1 μM in DCM using an excitation wavelength of 475 nm. A typical Stokes shift (10 nm) is demonstrated for construct 6 (part C

Synthesis and optical properties of new 5'-aryl-substituted 2,5-bis(3-decyl-2,2'-bithiophen-5-yl)-1,3,4-oxadiazoles

• Anastasia S. Kostyuchenko,
• Tatyana Yu. Zheleznova,
• Anton J. Stasyuk,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2017, 13, 313–322, doi:10.3762/bjoc.13.34

• ). Moderate to large values of Stokes shifts are observed for compounds 15b–g originating from bond order switching (benzenoid to quinoid) in the excited state. Moderate values of Stokes shifts (0.52–0.63 eV) are observed for 15b–e and the Stokes shift increases with an increase of the aryl substituent size

• . As expected, the largest Stokes shift values of 0.85 eV and 0.79 eV are observed for 15f and 15g, i.e., the derivatives with the largest substituents anthracen-9-yl (0.85 eV) and pyren-1-yl (0.79 nm), respectively. Note the clear vibrational structure in the spectra of 15b–e which is nonexistent in

Benzothiadiazole oligoene fatty acids: fluorescent dyes with large Stokes shifts

• Lukas J. Patalag and
• Daniel B. Werz

Beilstein J. Org. Chem. 2016, 12, 2739–2747, doi:10.3762/bjoc.12.270

• ; membrane; Stokes shift; Introduction The membrane of living cells consists of a variety of lipids. More than 40 years ago, biological membranes were first described as Fluid Mosaic in which proteins were embedded [1]. During recent decades it became more and more clear that such a simple model is not

Thiophene-forming one-pot synthesis of three thienyl-bridged oligophenothiazines and their electronic properties

• Dominik Urselmann,
• Konstantin Deilhof,
• Bernhard Mayer and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2016, 12, 2055–2064, doi:10.3762/bjoc.12.194

• -cyclization synthesis of thienyl-bridged oligophenothiazine dumbbells 3. UV–vis and emission data and oxidation potentials of thienyl-bridged oligophenothiazines 3 (recorded in CH2Cl2, T = 298 K; bold values: absorption and emission maxima used for determining the Stokes shift). Supporting Information The

Synthesis and fluorosolvatochromism of 3-arylnaphtho[1,2-b]quinolizinium derivatives

• Phil M. Pithan,
• David Decker,
• Manlio Sutero Sardo,
• Giampietro Viola and
• Heiko Ihmels

Beilstein J. Org. Chem. 2016, 12, 854–862, doi:10.3762/bjoc.12.84

• nm or 538 in DMSO, respectively (Table 1, Figure 3A–D). Derivative 6e is also fluorosolvatochromic, whereas the emission band is red-shifted by 78 nm from CHCl3 (λfl = 485 nm) to MeCN (λfl = 563 nm) (Figure 3D, Figure 4). Moreover, 6e exhibits the highest Stokes shift in MeCN (Δλ = 63 000 cm−1

Design, synthesis and photochemical properties of the first examples of iminosugar clusters based on fluorescent cores

• Mathieu L. Lepage,
• Antoine Mirloup,
• Manon Ripoll,
• Fabien Stauffert,
• Anne Bodlenner,
• Raymond Ziessel and
• Philippe Compain

Beilstein J. Org. Chem. 2015, 11, 659–667, doi:10.3762/bjoc.11.74

• of 24% (in aqueous glycine buffer at pH 10.7), the profile of the band mirrors the absorption with a maximum at 558 nm which is in keeping with little reorganization in the excited state and characteristic of a singlet emitter. The modest Stokes shift (Δss = 1020 cm−1) and the short excited state

• large Stokes shift of 6850 cm−1 and a longer excited state life time (τ = 71.7 ns) [72]. Again the excitation spectrum matches the absorption one proving that aggregation is unlikely under the used aqueous conditions. From a general point of view, fluorescent probes have been used for the detection of

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• photobleaching, a significant overlap of the absorption and emission spectrum (minor Stokes shift) and the chemical stability in stock solution is often declared by the producer to last only several months. Although the phenanthridine/phenanthridinium system in principle does not show the ideal combination of

• non-emissive form in the free state/very strong emission in the bound state, it has several advantages over cyanine dyes: phenanthridine/phenanthridinium fluorescence is characterised by a large Stokes shift (up to 100 nm) allowing the full use of absorption maxima as well as easy incorporation in

Synthesis and properties of novel star-shaped oligofluorene conjugated systems with BODIPY cores

• Clara Orofino-Pena,
• Diego Cortizo-Lacalle,
• Joseph Cameron,
• Muhammad T. Sajjad,
• Pavlos P. Manousiadis,
• Neil J. Findlay,
• Alexander L. Kanibolotsky,
• Dimali Amarasinghe,
• Peter J. Skabara,
• Tell Tuttle,
• Graham A. Turnbull and
• Ifor D. W. Samuel

Beilstein J. Org. Chem. 2014, 10, 2704–2714, doi:10.3762/bjoc.10.285

• lowers the luminescence efficiency of the material. Due to this aggregation and a low Stokes shift, BODIPY dyes with efficient emission in the solid state are still rare [16]. One of the strategies to suppress the aggregation of π-functional emissive units is to incorporate them into star-shaped

• pyrrole unit as well. It is known that attaching aromatic units to the β-positions of BODIPY increase the Stokes shift due to more pronounced structural relaxation of the excited state [29]. Therefore, incorporating the BODIPY unit as the core could improve the separation between absorption and emission

• spectra of the material and thereby decrease its self-absorption. We have recently shown among oligofluorene–BODIPY diads that compounds with oligofluorenes attached at the β-position of BODIPY have a significantly higher Stokes shift than those with oligofluorenes at the meso-position [30]. In this paper

A small azide-modified thiazole-based reporter molecule for fluorescence and mass spectrometric detection

• Stefanie Wolfram,
• Hendryk Würfel,
• Stefanie H. Habenicht,
• Christine Lembke,
• Phillipp Richter,
• Eckhard Birckner,
• Rainer Beckert and
• Georg Pohnert

Beilstein J. Org. Chem. 2014, 10, 2470–2479, doi:10.3762/bjoc.10.258

• yield and compared it with other commercially available fluorophores of similar size (Figure 2). We chose N-(3-azidopropyl)-5-(dimethylamino)naphthalene-1-sulfonamide (DNS, 8) with a fluorophore system exhibiting a large stokes shift [1] suitable for fluorescence detection with UV filters

Synthesis of new, highly luminescent bis(2,2’-bithiophen-5-yl) substituted 1,3,4-oxadiazole, 1,3,4-thiadiazole and 1,2,4-triazole

• Anastasia S. Kostyuchenko,
• Vyacheslav L.Yurpalov,
• Aleksandra Kurowska,
• Wojciech Domagala,
• Adam Pron and
• Alexander S. Fisyuk

Beilstein J. Org. Chem. 2014, 10, 1596–1602, doi:10.3762/bjoc.10.165

• of each molecule, in which the order of bonds connecting the heteroaromatic units increases. The energy dissipated upon geometric relaxation of the excited molecule following the vertical HOMO–LUMO transition, prior to the return transition from S1 to S0 state, is manifested as a Stokes shift. Since

• 0−0 transitions are rarely observed in room temperature solution spectra, it is acceptable to use Δ = λem − λmax (see Table 1 and Table 2) as the Stokes shift magnitude index [15]. Moderate values of Stokes shifts are observed for the investigated compounds indicating that the geometric

Synthesis, characterization and DNA interaction studies of new triptycene derivatives

• Sourav Chakraborty,
• Snehasish Mondal,
• Rina Kumari,
• Sourav Bhowmick,
• Prolay Das and
• Neeladri Das

Beilstein J. Org. Chem. 2014, 10, 1290–1298, doi:10.3762/bjoc.10.130

• present in the former. Exited state properties: The DMSO solutions of the ethynyl derivatives 1 and 2 are found to be weakly fluorescent with an emission maximum at 311 nm upon excitation at 260 nm. The corresponding Stokes shift is ~51 nm (Supporting Information File 1, Figure S7) for both 1 and 2. The