p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies

• Panagiotis S. Gritzapis,
• Panayiotis C. Varras,
• Nikolaos-Panagiotis Andreou,
• Katerina R. Katsani,
• Konstantinos Dafnopoulos,
• George Psomas,
• Zisis V. Peitsinis,
• Alexandros E. Koumbis and
• Konstantina C. Fylaktakidou

Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33

• [78][80]. Acetophenone (AP) is such a compound, that when initially excited to its first singlet excited state, exhibits a singlet-to-triplet conversion quantum yield close to 100% [81] and has been used for its triplet energy transfer [82]. In order to experimentally prove that DNA dissociation

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

• with JASCO FP-8500 spectrometer. Quantum yield was determined using an integration sphere system. CD and CPL spectra were recorded with JASCO J-820AC and JASCO CPL-300 spectrometers. HPLC analysis was carried out with JASCO EXTREMA (PU4180/MD4015/CO4065) equipped with YMC CHIRAL ART Amylose-SA and YMC

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

• 3b and 3d exhibited long-wavelength absorption maxima at λabs = 404 nm and 368 nm, with emission bands at λfl = 548 nm and 419 nm. Derivative 3d was essentially nonfluorescent (Φfl < 0.01 in MeCN), whereas compound 3b (Φfl = 0.17 in MeCN) had the largest fluorescence quantum yield in comparison to

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

• photoluminescence quantum yield (ΦPL) of 3 is poor at 4%. We next investigated the solid-state PL behavior of 3 in a 10 wt %-doped thin film using PMMA as host matrix. The PL spectrum of 3 exhibited two bands, one at 550 nm, corresponding to the emission of 3 and a second high-energy band at 450 nm that was

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 absorption maxima of the Z- and E-forms. At the same time, the introduction of the second methoxy group to the phenyl ring resulted in a decrease of the Z–E isomerization quantum yield and reduced the thermal half-life of E-1c in comparison to E-1b (Table 1). Nevertheless, the dimethoxy

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

• wealth of successful variants for photodecaging calcium have been described including examples whose photochemical quantum yield approaches unity [18][19][20][21][22][23][24]. While photorelease of calcium can be efficiently achieved in micro-to-millimolar concentration and has led to new insights in

• a water-soluble molecule which has a high affinity and selectivity for calcium, allowing binding of physiological levels of calcium, whose binding can be switched reversibly as efficiently as possible both in terms of affinity and quantum yield. In principle this would offer real-time regulation of

• 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

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

• shift to 673 nm (Table 8, entry 7). Most remarkably, the regioisomers 6c and 6e differ quite significantly with respect to their fluorescence quantum yields Φf. While chromophore 6e only emits with an efficiency of 1%, the regioisomer 6c accounts for an extraordinarily high relative quantum yield of 99

• -dimethylaminophenyl derivative 6c shows an enormous redshift to 694 nm. The solid-state fluorescence quantum yield Φf of compound 6c was determined to 11%. Interestingly, the α-pyrone 6e with the N,N-dimethylaminophenyl substituent in 4-position only fluoresces weakly in solution but shows a strong fluorescence in

• quantum yield of 99% in solution and 11% in the solid state was achieved. Interestingly, the isomeric p-N,N-dimethylaminophenyl substitution in 6-position represents a system with aggregation-induced emission enhancement. These design principles of luminescent 1H-pyridines and α-pyrones as polarity

A photochemical determination of luminescence efficiency of upconverting nanoparticles

• Baptiste Amouroux,
• Clément Roux,
• Jean-Claude Micheau,
• Fabienne Gauffre and
• Christophe Coudret

Beilstein J. Org. Chem. 2019, 15, 2671–2677, doi:10.3762/bjoc.15.260

• in mol L−1 s−1, Φco is the ring opening quantum yield, i.e., the number of events divided by the number of photons absorbed and Ia is the rate of photon absorption, in mol L−1 s−1, i.e., the photon flux per volume of solution to be measured. Note that for a given reactor of volume V, the photon flux

• energy of a 540 nm photon, to the emitting power of a single nanoparticle and the number of emitted photons per erbium atom J0/nEr in photon s−1. All of these numbers are gathered in Table 2, more detailed calculations are provided in Supporting Information File 1. The as-determined quantum yield is in

A new approach to silicon rhodamines by Suzuki–Miyaura coupling – scope and limitations

• Thines Kanagasundaram,
• Antje Timmermann,
• Carsten S. Kramer and
• Klaus Kopka

Beilstein J. Org. Chem. 2019, 15, 2569–2576, doi:10.3762/bjoc.15.250

• characterization data (fluorescence spectra, quantum yield) of thienyl-substituted silicon rhodamine 30c. Acknowledgements We are very grateful to the Wilhelm Sander Stiftung for a grant on bi-modal tumor tracers (2018.024.1). We thank Yvonne Remde for synthetic support. We are thankful to Jessica Matthias (group

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

• , belonging to the hydrazone family. The outstanding properties of this molecule, involving fluorescence toggling, bistability, high isomerization quantum yield and non-negligible two-photon absorption cross section, make it very promising for numerous applications. Here we show that the light induced Z/E

• the fluorescence band and the emission quantum yield depend on the solvent, with the emission strongly quenched in protic media [29]. Time-resolved fluorescence Detailed analysis of the fluorescence features of the two forms in toluene has been performed by time-resolved luminescence measurements in

• scale is shown in Figure 2). The short lifetime of 1.3 ps can be ascribed to the fluorescence of the E-form, mainly centered in the 440–460 nm region, which accounts for the very low emission quantum yield of this form observed in the steady-state experiment. The emission from the Z-form is detected

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

• spectra, see section VI in Supporting Information File 1). This allowed us to determine the quantum yields of photochemical reactions. Cyclopentene (4) and cyclopentenone (3) derivatives show the highest photocyclization quantum yields up to 0.42 in toluene. In polar acetonitrile the cyclization quantum

• yield is lower [40]. The quantum yields for cyclohexenone derivatives 6 and 7 are in the 0.22–0.27 range. Similar to some other cyclopentene derivatives [41], diarylethene 4 possesses low cycloreversion quantum yields at 4–6%. However, in accordance with previous results on imidazole derivatives [42], 3

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

• state according to previous studies [39][40][41]. The quantum yield of the formation of the triplet excited state was reported as 92% [42], indicating that most of the S1 state is converted to the T1 state in benzil. Figure 3b shows the transient absorption spectra of Benzil-PIC in benzene (2.2 × 10−3 M

• faster than this time scale (hundreds of femtoseconds), the time constant of 38 ps reflects the singlet–singlet energy transfer process from the benzil unit to the PIC unit. It should be noted that the fluorescence quantum yield of benzil was quite low (<0.001) [43] and the PIC unit has no absorption in

• spectroscopy revealed that the benzil unit acts as a singlet photosensitizer for Benzil-PIC by the Dexter-type energy transfer. It was reported that benzil was often used as a triplet photosensitizer because the quantum yield for the T1 state formation is 92% [42]. To investigate the possibility for the

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

• large fluorescence quantum yield, compound SyOTh1 emerged as a candidate for single-molecule based super-resolution fluorescence microscopy. Keywords: diarylethenes; dyes; fluorescence; organic synthesis; photochromism; photoswitching; Introduction Reversibly photoswitchable diarylethenes (DAEs) with

• fluorescence quantum yields. They exceeded lifetimes measured for the fluorescence of the unsubstituted DAE 6 by a factor of 4, and the fluorescence quantum yield of the CF of 6 was surpassed by the oxidized DAEs with thiophene side rings by a factor of 3–8 [4]. The open forms of the substituted oxidized

• – fluorescence and off-switching – compete for the depopulation of the same excited state [10]. Hence, the ratio of fluorescence quantum yield and off-switching quantum yield is proportional to the number of emitted photons (Nph) per cycle or per incursion into the fluorescent state (i.e., before off-switching

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

• the use in multimodal (PET/OI) medical imaging of mitochondria in cancerous cells. Results: A dihalogenated fluorinatable pyridinyl rhodamine could be successfully synthesized with the high yield of 85% by application of a halogen dance (HD) rearrangement. The near-infrared dye shows a quantum yield

• 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

• photophysical properties of numerous silicon rhodamines leading to further insights into the correlation of the dyes’ chemical structure with their fluorogenic behavior [27]. Regarding the quantum yield, Hanaoka et al. have shown that introduction of methyl, methoxy or dimethylamine groups into the benzene

Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses

• Anne-Marie Caminade,
• Artem Zibarov,
• Eduardo Cueto Diaz,
• Aurélien Hameau,
• Maxime Klausen,
• Kathleen Moineau-Chane Ching,
• Jean-Pierre Majoral,
• Jean-Baptiste Verlhac,
• Olivier Mongin and
• Mireille Blanchard-Desce

Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221

• dimer and 33% for the G1 dendrimer, but a 15% decrease of the TPA response was measured for the G2 dendrimer [53]. In addition, in that case, also the fluorescence quantum yield was found to decrease dramatically with an increasing number of fluorophores. TPA fluorophore as core of dendrimers None of

• has a large influence on the λmax of the fluorescence for the dendrimer with P(S)Cl2 terminal functions, which ranges from 443 nm in AcOEt to 501 nm in DMSO. Furthermore, the quantum yield (Φf) of the dendrimer with ammonium terminal groups was 0.42 in DMSO (to be compared with 0.78 for the

• G2 PEG. Thus, both compounds exhibit similar performances, the lower quantum yield being counter-balanced by a higher TPA cross-section, and vice versa [45]. TPA fluorophores at two levels of the dendrimer’s structure Having in hand the methods to introduce TPA fluorophores either on the surface, at

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

• quantum yield (Φf) of 0.027. The fluorescent emission spectra of 1o in several solvents were shown in Figure 4, and λmax of the emission spectra and the fluorescence quantum yields in the solvents are summarized in Table 2. These emission spectra of 1o were largely red-shifted, indicating the ESIPT

• mm quartz cell, which was then placed in the integral sphere. The quantum yield was calculated using an installed software. The solid-state absorption spectrum was obtained by Kubelka–Munk conversion of a diffractive reflectance spectrum of the above mixture measured on a JASCO FP-6600

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

• solution of 7 in CHCl3/CH3OH (3:1, v/v), a remarkable naked-eye recognizable color change from red to orange was observed. According to fluorescence spectroscopy, the emission intensity of PDI increased considerably (quantum yield enhancement factor of 57%). Anions are recognizable by catenane 7 at low

Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes

• Marco Santella,
• Eduardo Della Pia,
• Jakob Kryger Sørensen and
• Bo W. Laursen

Beilstein J. Org. Chem. 2019, 15, 2133–2141, doi:10.3762/bjoc.15.210

• less bright fluorophores. Thus, the dialkylamino-substituted analogue of 5a (A3-ADOTA+) has a reported quantum yield as high as 64% in acetonitrile [17], on par with A3-TOTA+ and A2-TOTA+ which display quantum yields from 50–100% depending on the solvent [31]. A similar reduction in fluorescence

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

• and quantum yield, low background fluorescence) are still poorly understood, mostly due to the lack of comparative studies. To explore this aspect, we report the synthesis and systematic study of a library of 61 di- and mono-styryl dyes, as potential “light-up” probes for G4 structures. The study aims

• varying content of guanine and a wealth of duplex structures, and (2) discriminating G4 structures based on their topology, with the exception of a few notable cases presenting structural peculiarities. Quantum yield and brightness of the probes Four highly responsive and G4-selective dyes, namely 1p, 1u

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

• exhibit significant fluorescence solvatochromic properties, that is, the two dyes show a significant decrease in the fluorescence quantum yield (Φf) in a polar solvent such as DMF (Φf = 0.59, 0.14 and 0.09 for OUY-2, OUK-2 and OUJ-2, respectively), although in relatively low polar solvents OUK-2 and OUJ-2

Synthesis, enantioseparation and photophysical properties of planar-chiral pillar[5]arene derivatives bearing fluorophore fragments

• Guojuan Li,
• Chunying Fan,
• Guo Cheng,
• Wanhua Wu and
• Cheng Yang

Beilstein J. Org. Chem. 2019, 15, 1601–1611, doi:10.3762/bjoc.15.164

• derivatives (P5A-DPA and P5A-Py) bearing bulky fluorophores were obtained in high yield by click reaction. The photophysical properties of both compounds were investigated in detail. P5A-DPA with two 9,10-diphenylanthracene (DPA) pigments grafted on the pillar[5]arene showed a high fluorescence quantum yield

• of 89.5%. This is comparable to the monomer DPA-6, while P5A-Py with two perylene (Py) pigments grafted on the pillar[5]arene showed a significantly reduced quantum yield of 46.4% vs 78.2% for the monomer Py-6. The oxygen-through-annulus rotation of the phenolic units was inhibited for both compounds

• quantum yield are beneficial for the application of pillar[5]arene in these fields. Perylene (Py) and 9,10-diphenylanthracene (DPA) are well known for their desirable absorption and high fluorescence quantum yield. These chromophores possess unique photophysical properties and have been widely used as

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• precious metal chloride complexes. The UV–vis absorption spectrum was shown in Figure S21 (Supporting Information File 1), and the absorption maxima are located at 241 nm and 290 nm. However, the optimal excitation wavelength is at 310 nm with a quantum yield of 6.6% in dichloromethane. The emission

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

• internal conversion from S1 to S0 is responsible for the increase in the fluorescence quantum yield in these hydrophobic environments [44][45]. The fluorescence intensity of 2,6-TNS was extremely low with a maximum emission wavelength at 495 nm in aqueous solution [46]. Its fluorescence was dramatically

N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe³⁺ sensing

• Jia Gao,
• Ming-Xue Wu,
• Dihua Dai,
• Zhi Cai,
• Yue Wang,
• Wenhui Fang,
• Yan Wang and
• Ying-Wei Yang

Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123

• nm and 365 nm, which coincides with the blue light emission. The obvious blue shift was due to the modification of CP[5], which led to the increase of n–π* transition energy with the formation of new amide bonds [4][25]. The PL quantum yield (QY) of the CCDs aqueous solution was determined to be 4