Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• intensity, lifetime or excitation/emission maxima. The fluorescence turn-on response offers a bright signal against a dark background, which maximizes spatial resolution than the fluorescence turn-off signal [19]. A shift in the absorption/emission spectrum is also advantageous as the changes in ratio of

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

• of water, and later they drop due to ACQ. Also, it is possible to observe that the lifetimes follow a similar trend, where an increase of the emission intensity accompanies a minor prolongation of the lifetime and subsequently a drop of the quantum yield along with a shortening of the lifetimes

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• mean lifetime of a chain before it breaks into two pieces. As expected, the scission time is independent from the concentration and amounts to τb = 0.13 s. With the knowledge of τR and τb, the reptation time τrep can be estimated from Equation 6 [32]: The reptation time is the reflection of the time

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• reported lifetimes for monomeric pyrenes [66][67]. In aqueous buffer, the lifetime of the 395 nm band decreased (≈15–35 ns, Supporting Information File 1, Table S3) probably owing to the increment in the solvent polarity [68]. The average lifetime values (τavg) of the excimeric bands of PBIm10, PBIm12 and

• exhibited lower responses (Supporting Information File 1, Figure S9). In terms of the lower limit of detection, ATP was detected at 500 nM concentration by the PBIm12 aggregates. A noticeable increase in the average lifetime (τavg) of the excimeric band was observed after ATP addition (Supporting

Synthetic approaches to bowl-shaped π-conjugated sumanene and its congeners

• Shakeel Alvi and
• Rashid Ali

Beilstein J. Org. Chem. 2020, 16, 2212–2259, doi:10.3762/bjoc.16.186

• Z-oct-4-ene in toluene was found to be a more effective alkene source for the ring-opening reaction in comparison to the gaseous ethylene, as it increases solubility and also improve the lifetime of the catalyst. 2.1 Derivatization at benzylic position As can be inferred from the architecture of

Photosensitized direct C–H fluorination and trifluoromethylation in organic synthesis

• Shahboz Yakubov and
• Joshua P. Barham

Beilstein J. Org. Chem. 2020, 16, 2151–2192, doi:10.3762/bjoc.16.183

• cleavage reactions [80] and 1,5-HAT [81] and iii) the excited state of the simple organic molecule target can possess an ultrashort lifetime [82] that precludes photochemistry in favor of photophysical or nonradiative deactivation, e.g., fluorescence or internal conversion (IC). Instead of direct UV

• principle, the photosensitizer is regenerated and therefore functions in a very similar way to a catalyst and can be deemed a photocatalyst. A common example of this concept is triplet photosensitization. The excited photocatalyst has a relatively high triplet-state energy and a long lifetime, such that it

• byproducts. It is inexpensive, sustainable (ideally not ruthenium or iridium complexes) and commercially available. Due to their comparatively high triplet energies and the long lifetime of their triplet states; organic dyes and various ruthenium and iridium complexes are well-suited photosensitizers [118

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

• 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

Heterogeneous photocatalysis in flow chemical reactors

• Christopher G. Thomson,
• Ai-Lan Lee and
• Filipe Vilela

Beilstein J. Org. Chem. 2020, 16, 1495–1549, doi:10.3762/bjoc.16.125

• measurements, TRPL spectroscopy, and density functional theory (DFT) calculations. They found that the HER efficiency correlated to the excited state lifetime and exciton binding energy. The FSO-BP and FSO-FSz hindered the charge transfer and mobility due to the phenyl–phenyl dihedral angle or sharp bends in

• shown by Ji, Zhao, Jacquemin, and co-workers [130], and may have contributed to extending the excited state lifetime and reducing the binding energy of excitons in FSO-FS relative to FSO-F. 2.3 Immobilised molecular photocatalysts A strategy that combines many of the benefits of homogenous and

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

• an inert gas (N2 or Ar) allows the triplet states to survive for a long lifetime, which possibly leads to a phosphorescence emission. Hence, the elimination of O2 gas from solutions by N2 gas bubbling (or addition of O2 gas in solutions) can judge the presence of phosphorescence, as well as the

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

• compounds 1–3 were recorded (Figure 5b). The PL decay curve of the solid sample of the carbazole-containing compound (1) was adequately described by a single-exponential function with a lifetime of 4.8 ns (prompt fluorescence). The PL decay curves of compounds 2 and 3 were found to be double exponential

Recent applications of porphyrins as photocatalysts in organic synthesis: batch and continuous flow approaches

• Rodrigo Costa e Silva,
• Luely Oliveira da Silva,
• Aloisio de Andrade Bartolomeu,
• Timothy John Brocksom and
• Kleber Thiago de Oliveira

Beilstein J. Org. Chem. 2020, 16, 917–955, doi:10.3762/bjoc.16.83

• photocatalysts. Under light irradiation, one electron from the ground state (S0) is promoted to the excited singlet state (S1) which has a short lifetime (10−9 s). Therefore, fast intersystem-crossing of one electron gives the excited triplet state (T1) with a relatively longer lifetime (10−6 s). While the

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

• -anisaldehyde (98), which possessed a relatively long lifetime and an energetic value sufficient for C–X bond cleavage. The participation of the triplet state 4-anisaldehyde (98) in the reaction mechanism was also confirmed by the complete inhibition of the ATRA reaction in the presence of oxygen, a triplet

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

• 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

Recent advances in photocatalyzed reactions using well-defined copper(I) complexes

• Mingbing Zhong,
• Xavier Pannecoucke,
• Philippe Jubault and
• Thomas Poisson

Beilstein J. Org. Chem. 2020, 16, 451–481, doi:10.3762/bjoc.16.42

• , copper-based photocatalysts are often considered less efficient due to a lower luminescence lifetime compared to Ir and Ru complexes [6]. Review In this review, we summarized the recent significant advances that were made in the use of copper-based photocatalysts for synthetically useful transformations

• examples. Indeed, they usually possess an increased lifetime of the triplet excited state due to a particular geometry that prevents the reorganization from a tetrahedral geometry in the ground state to a square planar geometry [31]. Moreover, the synthesis of these compounds is usually facile, and they

• phenanthroline derivative and a bisisonitrile ligand, [Cu(I)(dpp)(binc)]BF4, which was fully characterized (Scheme 15) [32]. This complex proved to have a similar or higher excited state lifetime (17 μs) compared to the previously reported complexes and a redox potential of −1.88 V vs SCE in the excited state

Visible-light-induced addition of carboxymethanide to styrene from monochloroacetic acid

• Kaj M. van Vliet,
• Nicole S. van Leeuwen,
• Albert M. Brouwer and
• Bas de Bruin

Beilstein J. Org. Chem. 2020, 16, 398–408, doi:10.3762/bjoc.16.38

• their oxidized/reduced forms) can perform both opposed redox events before returning to their original oxidation state for re-excitation. If no substrate is encountered during the lifetime of the excited state the ground state is typically regenerated. Such photogenerated radical intermediates can be

Six-fold C–H borylation of hexa-peri-hexabenzocoronene

• Mai Nagase,
• Kenta Kato,
• Akiko Yagi,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2020, 16, 391–397, doi:10.3762/bjoc.16.37

• high solubility of 1. In order to analyze the optoelectronic properties of 1, the UV–vis absorption spectra, fluorescence spectrum, absolute fluorescence quantum yield and fluorescence lifetime were measured (Figure 4a and Figure S1, Supporting Information File 1). In comparison with the absorption

• , which indicated that these peaks can be assigned to 0–0 transitions. The absolute fluorescence quantum yield (ΦF) and fluorescence lifetime (τ) were 2.5% and 12.4 ns, respectively. According to the equations ΦF = kr × τ and kr + knr = τ−1, the radiative (kr) and nonradiative (knr) decay rate constants

• measured on a Shimadzu RF-6000 spectrometer with a resolution of 0.5 nm. Absolute fluorescence quantum yield (ΦF) was determined on a Shimadzu RF-6000 spectrometer using a calibrated integrating sphere system upon excitation at 340 nm. For FL lifetime measurement, a Hamamatsu Photonics Quantaurus-Tau

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

• nonradiative and radiative pathways. Light is emitted (− hv) upon modulation of radiative pathways to lower energy states, whereas in nonradiative pathways, dissipated energy is lost in the form of heat. In the case of fluorescence (a radiative pathway with a short lifetime), S1 returns to S0. On the other

• disappearance of phosphorescence, following the Frank–Condon principle [44][45]. As far as the singlet and triplet excited states of organic dyes and organometallic compounds are concerned, there is a difference in lifetimes. Usually, the lifetime of excited states of organic dyes is nanoseconds, whereas for

Synthesis and characterization of bis(4-amino-2-bromo-6-methoxy)azobenzene derivatives

• David Martínez-López,
• Amirhossein Babalhavaeji,
• Diego Sampedro and
• G. Andrew Woolley

Beilstein J. Org. Chem. 2019, 15, 3000–3008, doi:10.3762/bjoc.15.296

• enhanced in the NIR window [7]. Longer-wavelength absorption is achieved by compounds 2, 3, and related derivatives (Figure 1) [9]. However, the lifetime of thermal reversion of the cis isomer of 2 is only ≈1 ms at a neutral pH value, and the pKa for trans-azonium ion formation is ca. 2.6. The low pKa was

Synthesis and optoelectronic properties of benzoquinone-based donor–acceptor compounds

• Daniel R. Sutherland,
• Nidhi Sharma,
• Georgina M. Rosair,
• Ifor D. W. Samuel,
• Ai-Lan Lee and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2019, 15, 2914–2921, doi:10.3762/bjoc.15.285

• to the benzoquinone acceptor. Compound 3, where benzoquinone is para-conjugated to the diphenylamine donor group, exhibited thermally activated delayed fluorescence (TADF) with a biexponential lifetime characterized by a prompt ns component and a delayed component of 353 μs. Keywords: materials

• ps [40], with efficiency close to unity [41][42], implying that the nonradiative ISC channel of excitons from S1 to T1 is always preferred over the radiative decay from the S1 state. For compound 3, we observed a prompt lifetime of 19.4 ns, which indicated there was not ultrafast ISC. This is

• theoretical, electrochemical, and photophysical properties of the donor–acceptor compounds 2–5 were determined in solution and thin film. While compounds 2, 4, and 5 were very poorly emissive, 3 showed a green emission with a biexponential lifetime characterized by a prompt nanosecond component and a delayed

Iodine-mediated hydration of alkynes on keto-functionalized scaffolds: mechanistic insight and the regiospecific hydration of internal alkynes

• Zachary Lee,
• Brandon R. Jones,
• Nyochembeng Nkengbeza,
• Michael Phillips,
• Kayla Valentine,
• Alexis Stewart,
• Brandon Sellers,
• Nicholas Shuber and
• Karelle S. Aiken

Beilstein J. Org. Chem. 2019, 15, 2747–2752, doi:10.3762/bjoc.15.265

• resulted in the generation of 10 (Figure 1d). Changes in the resonances for the phenyl protons, H-8, H-9, and H-10, if any, were indiscernible. To increase the lifetime of the intermediate 9 so that more detailed analyses could be performed, the iodonium source was changed from I2 to ICl (Figure 1c). The

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

• quantum yields (Φfluo) of the dyes, the highest values were determined for the compounds 16 and 18, being in the range of 0.35–0.59 in the investigated solvents. The dyes 17 and 19 show smaller values for Φfluo (ca. 0.15–0.30). The fluorescence lifetime of the SW emission was measured as 300–900 ps, being

• . Based on the microsecond lifetime (τT = 3.1 μs (18) and 2.4 μs (19)), oxygen quenching (kq ca. 2.9-3.1 × 109 M−1s−1), and β-carotene triplet sensitization experiments the signals at 410 nm (dye 18) and 430 nm (dye 19) were assigned to excited triplet states as well. An additional signal at 470 nm for

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

• fluorescence was used to detect a lipid droplet in monkey aortic smooth muscle cells [16], for visualizing different proteins, such as lactoglobulin, casein and albumin [17]. In fluorescence lifetime imaging microscopy τf as a viable contrast parameter was employed to image lipid droplets in living HeLa cells

• polarization (rearrangement of atomic bonds and valence angles) a certain dipolar orientation degree of freedom take place in PMMA within the lifetime of excited state of NR. The restriction of the orientational relaxation causes an inhomogeneous broadening of the fluorescence spectrum of NR and its excitation

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

• the picosecond time regime (see Materials and Methods for details). Upon excitation of 1 in the Z form at 400 nm, the fluorescence is characterized by a mono-exponential decay on the whole emission spectral range, with an average lifetime of 173 ps (Figure 2, bottom). It can be pointed out that the

• obtained lifetime value is in accordance with the excited state lifetime previously measured for the Z-isomer [29]. After complete Z/E isomerization, obtained by irradiating the solution at 440 nm, the time-resolved luminescence of the E-form was analyzed upon excitation at 350 nm. The spectral

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• A. PIC generates the biradical species upon UV-light irradiation and shows the broad transient absorption spectrum over the visible- to near infrared-light regions. The half-life of the thermal back reaction of the biradical in benzene is 250 ns (the lifetime is 360 ns) at 298 K. To investigate the

• of microseconds. The transient absorption dynamics at 590 nm can be fitted with a single exponential decay function and the lifetime is 220 ns (Figure 2d), which is almost identical to that of the fast decay component under argon atmosphere. Because the transient absorption spectrum at 0.5 ns is

• measurements was limited to 2 ns, it was difficult to determine the time constant of nanosecond time scale exactly. Therefore, the lifetimes of the intersystem crossing (ISC) of benzil and the benzil unit of Benzil-PIC were fixed to a reported value of benzil (2.5 ns) [44]. The lifetime of the T1 state of

Synthesis of a dihalogenated pyridinyl silicon rhodamine for mitochondrial imaging by a halogen dance rearrangement

• Jessica Matthias,
• Thines Kanagasundaram,
• Klaus Kopka and
• Carsten S. Kramer

Beilstein J. Org. Chem. 2019, 15, 2333–2343, doi:10.3762/bjoc.15.226

• features with their optical properties and control the latter by rational dye design [15][24][25][26]. These investigations led to new silicon rhodamine dyes with enhanced and fine-tuned properties (quantum yield, lifetime, brightness, absorption and emission maxima). A recent review compared the

• experiments (supported by DFT calculations) on the orbital effects of both halogens and the nitrogen position in the pyridine ring are needed to explain these effects with confidence. In addition, our SiR dye 15 displays photophysical properties (extinction coefficient, quantum yield, lifetime) in the same