Naphthalene diimide–amino acid conjugates as novel fluorimetric and CD probes for differentiation between ds-DNA and ds-RNA

• Annike Weißenstein,
• Myroslav O. Vysotsky,
• Ivo Piantanida and
• Frank Würthner

Beilstein J. Org. Chem. 2020, 16, 2032–2045, doi:10.3762/bjoc.16.170

• stronger quenching for GC-DNA and the weaker for AT(U)-polynucleotides (Figure 5a and b). Because guanine is the most electron-rich nucleobase, this behaviour points at a fluorescence quenching mechanism by charge transfer from the electron-rich purine bases to the electron-poor NDI molecular probes

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

• fluorescence quenching studies, UV–vis spectroscopy experiments, calculation of the quantum yield, a cutoff experiment below 400 nm, GC–MS analysis, and NMR spectroscopic mechanistic experiments. They also concluded that an energy transfer mechanism could not be possible since the solvent employed affected the

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

• hydroxylation of arenes (Scheme 18) [157]. They realized that the photoredox catalyst 8 possesses a great oxidizing ability (Ered vs SCE = 2.72 V) at ambient conditions. The mechanism of the reaction was studied by fluorescence quenching and transient absorption spectroscopy. They observed that the one-electron

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• paramagnetic nature of chromium(III) can cause fluorescence quenching of the fluorophore via the enhancement of spin–orbit coupling [30][31][32][33][34][35]. So far, only a few successful examples of fluorescence enhancement sensors for Cr3+ have been reported [36][37][38][39][40]. Thus, developing new and

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

• molecular aggregation in the solid state causes fluorescence quenching [16]. In recent years, we have coined diversity-oriented syntheses of functional chromophores by multicomponent strategies [17][18], opening accesses to substance libraries for systematic studies of structure–property relationships on

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

• these dyes such as intramolecular charge-transfer processes and tunable red-shifted emission bands. Generally, the so far investigated borylated arylisoquinoline dyes show principally fluorescence quenching (on-off switching) on the formation of the corresponding fluoroboronate complexes [37]. Herein

• 16–19 on the addition of tetra-n-butylammonium fluoride (Bu4NF) in acetonitrile are depicted. The dyes 16 and 17 show a strong fluorescence quenching of their LW bands, while the SW bands experience a slight increase. However, the situation for the dyes 18 and 19 is dramatically different. Here the

• residue (naphthyl, 4-methoxynaphthyl, pyrenyl, anthryl). This provides some hint that intramolecular charge-transfer phenomena are likely involved. Laser-flash photolysis studies provided insights into the existence of excited triplet states. The addition of fluoride anions led to pronounced fluorescence

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

• be responsible for the fluorescence quenching in the Z-form. A comparison of the kinetic traces recorded on the maximum of the excited state absorption band in the three analyzed solvents (Figure 6) demonstrates that the excited state decay time decreases on going from acetonitrile to toluene, and

Targeted photoswitchable imaging of intracellular glutathione by a photochromic glycosheet sensor

• Xianzhi Chai,
• Hai-Hao Han,
• Yi Zang,
• Jia Li,
• Xiao-Peng He,
• Junji Zhang and
• He Tian

Beilstein J. Org. Chem. 2019, 15, 2380–2389, doi:10.3762/bjoc.15.230

• broad and strong absorption makes the 2D MnO2 nanosheets a potential energy acceptor for the fluorophores which are stacked on the nanosheets plane, leading to the fluorescence quenching through FRET mechanism [32][34]. The transmission electron microscopy (TEM) image of the prepared product revealed

• effective FRET between the attached Glyco-DTE and 2D MnO2, which again suggested the close stacking of Glyco-DTE to the nanosheet surface. Aggregation-caused quenching might be another reason for the fluorescence quenching because of the close distance between fluorescence molecules when absorbed on the

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

• measurement of the two-photon absorption cross-section, which is a marker of the efficiency of the TPA, displayed a linear increase with the number of fluorophores (Table 1), indicative of an additive behavior. In contrast, the fluorescence properties are only weakly affected. In particular, fluorescence

• quenching is prevented thanks to the design of the fluorophore [42]. It should be noted that the largest dendrimers, in particular generation 4, display very large two-photon absorption cross-sections (σ2 up to 55,900 GM), which are comparable to those measured for the best quantum dots [43]. Thus these

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

• was dropped to the UV light irradiated crystal 1o (Supporting Information File 3, Movie 2). The rate of fluorescence quenching (τ1/2 is less than 0.2 s) in the crystalline state is much faster than those observed in solutions. This is attributed to the degree of condensation which is much higher in

• ), acetonitrile (orange line). The absorption at the excited wavelength of each solution was adjusted to 0.05. (emission peaks at 740 nm is attributed to the 2nd order diffracted excitation light.) (a) The energy diagram of the ESIPT process of 1. (b) ESIPT fluorescence quenching upon UV light (λ = 313 nm

• solutions (λex = 370 nm). (c) The fluorescence quenching of THF 100 vol % (water 0 vol %) solution at 670 nm (broken line) and that of THF/water = 10:90 (v/v) at 585 nm (solid line) upon UV irradiation. (a) Crystals of 1o before UV light irradiation, (b) Green fluorescence of 1o observed under UV light (λ

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

• maximum of 1 is located at 350 nm (Figure S22, Supporting Information File 1). It is known that the binding of metal ions could cause fluorescence quenching through photo-induced electron transfer [44]. Indeed, the fluorescence intensity of 1 is quenched gradually upon addition of TBA[AuCl4] (Figure 6a

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

• ground-state complex, with drastic changes in both, band shapes and intensities. The calculated rate constant of PET is faster than that of fluorescence and intersystem crossing, which makes it a more favorable deactivation pathway of the first excited singlet state leading to both fluorescence quenching

• solutions benefiting from the high affinities and the corresponding drastic fluorescence quenching, which is desirable from the viewpoints of economy, sensitivity and interference [8][26]. With regard to the treating application, high affinities with PSs avoid undesired off-target leaking during its

• employed (Table 1), indicating its privileged ability to form stable inclusion complexes with a variety of guest molecules. As for Fl, EY, RB, TPPS, AlPcS4 and TPS, a drastic complexation-induced fluorescence quenching without wavelength shifting was observed, which was assumed as the PET mechanism. 2,6

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

• , quenching performance can be contributed to the energy transfer between ions and the materials [26]. Meanwhile, the UV–vis absorption peaks of CCDs exhibited no shift and regeneration before and after Fe3+ sensing, indicating that the fluorescence quenching is not resulted from the formation of new

• nm, Em. 5 nm. Fluorescence quenching degrees of a) CCDs and b) CN-dots in the presence of different metal ions. The concentrations of metal ions were 400 μМ. c) Fluorescence spectra of a CCDs system in the presence of different concentrations of Fe3+ ions (0–500 μM). d) Linear curve of the relative

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

• -assembly behavior in various solvents was investigated particularly in aqueous medium, due to the recently discovered hydrophilic properties of B21C7 crown macrocycle. An unexpected fluorescence quenching phenomenon was observed in the PDI-B21C7 macrocycle conjugate in chloroform. The detailed UV–vis

• their UV–vis absorption and fluorescence properties. An unexpected fluorescence quenching phenomenon was observed in the PDI-B21C7 macrocycle conjugate in chloroform. Through TEM characterization, it was illustrated that in aqueous medium, both PDI and NDI derivatives containing crown ether units could

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

• with a possible character of TICT [55], which could explain a dual-fluorescence and fluorescence quenching in the high polarity media. The charge transfer nature of the transitions for the compounds 8c and 11c, compared to reference compounds 8a and 11a, was confirmed by quantum chemical calculations

Rational design of boron-dipyrromethene (BODIPY) reporter dyes for cucurbit[7]uril

• Mohammad A. Alnajjar,
• Jürgen Bartelmeß,
• Robert Hein,
• Pichandi Ashokkumar,
• Mohamed Nilam,
• Werner M. Nau,
• Knut Rurack and
• Andreas Hennig

Beilstein J. Org. Chem. 2018, 14, 1961–1971, doi:10.3762/bjoc.14.171

• stability under various conditions, particularly under physiological conditions. Although most BODIPYs are insensitive to pH changes, pH-activatable optical probes for cancer imaging have been reported, in which an aniline substituent in the meso-position of the BODIPY core led to efficient fluorescence

• quenching by photoinduced electron transfer (PET), whereas the protonated form was brightly fluorescent [31]. We report herein the synthesis and photophysical characterization of BODIPY derivatives with an aniline substituent in the meso-position to which different anchor groups have been attached, and we

Strong binding and fluorescence sensing of bisphosphonates by guanidinium-modified calix[5]arene

• Jie Gao,
• Zhe Zheng,
• Lin Shi,
• Si-Qi Wu,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2018, 14, 1840–1845, doi:10.3762/bjoc.14.157

• , we employed fluorescein (Fl) as the reporter dye according to our previously published result [26]. Fl of high brightness is strongly encapsulated into the GC5A cavity (Ka = 5.0 × 106 M−1), accompanied with a drastic complexation-induced fluorescence quenching (Ifree/Ibound = 37). Taken together

Investigations of alkynylbenziodoxole derivatives for radical alkynylations in photoredox catalysis

• Yue Pan,
• Kunfang Jia,
• Yali Chen and
• Yiyun Chen

Beilstein J. Org. Chem. 2018, 14, 1215–1221, doi:10.3762/bjoc.14.103

• benziodoxole have opposite effects for the radical alkynylation, we first conducted the fluorescence quenching experiments of tolylacetylenic benziodoxole derivatives 3a–f and found none of them oxidatively quenched the photoexcited Ru(bpy)32+* complex (see Supporting Information File 1, Scheme S1). We next

Carbohydrate inhibitors of cholera toxin

• Vajinder Kumar and
• W. Bruce Turnbull

Beilstein J. Org. Chem. 2018, 14, 484–498, doi:10.3762/bjoc.14.34

• tryptophan fluorescence quenching assay to show that octavalent lactose-based dendrimer 34 (Figure 16) had a Kd value of 33 µM as compared to monovalent lactose derivative having a Kd value of 18,000 µM [51]. Hence, compound 34 displayed 545 fold more potency per lactose unit than monovalent lactose. In

Fluorogenic PNA probes

• Tirayut Vilaivan

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

• monomer–excimer switching approaches have some advantages over fluorescence quenching because of the large Stokes shifts and the ability to measure the signals at two different wavelengths, thereby providing a means for self-referencing. Furthermore, unlike the fluorophore-quencher beacons, the FRET and

• dT in the DNA strand with comparable affinity to that for A, and the base pairing resulted in fluorescence quenching. While the quenching of 2-AP can be useful for probing the structure and dynamics of the PNA and its DNA/RNA hybrids, the quenching effect is small and not highly specific as quenching

• was accompanied by fluorescence quenching, and Vg-modified aegPNA has been used to probe the interaction between RNA quadruplexes and PNA [181]. Another example of a nucleobase with extended conjugation that has been incorporated into PNA is 1,3-diaza-2-oxophenothiazine (tC), which is a tricyclic

Aminosugar-based immunomodulator lipid A: synthetic approaches

• Alla Zamyatina

Beilstein J. Org. Chem. 2018, 14, 25–53, doi:10.3762/bjoc.14.3

• antagonist) and the fluorescence intensity of 25 and its tetraacylated counterpart was comparable with the fluorescence of the labeling reagent alone. Aggregation-mediated fluorescence quenching was not observed which confirmed the advantage of application of highly hydrophilic linker molecules and non

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• indicating the interception of an excited CD state by the Fe3+ ion that leads to fluorescence quenching. The group exemplified the applicability of the material by demonstrating the ability of the B-CD to sense Fe3+ in tap water samples with a limit of detection of 242 nM, which complies with U.S

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• a complex formation, namely a hypochromic effect and red shift of the absorption as well as fluorescence quenching upon addition of the host (Figure 6 and Supporting Information File 1, Figure S3). Furthermore, the significant line broadening of the absorption bands occurs most likely due to

Formose reaction accelerated in aerosol-OT reverse micelles

• Makoto Masaoka,
• Tomohiro Michitaka and
• Akihito Hashidzume

Beilstein J. Org. Chem. 2016, 12, 2663–2667, doi:10.3762/bjoc.12.262

• the cases of AOT and CTAB, the radius of the water pools (Rw) was evaluated by dynamic light scattering, whereas, in the case of TX, Rw was estimated by the fluorescence quenching technique. As can be seen in Supporting Information File 1, Figure S1, Rw for AOT and CTAB is almost proportional to the

Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu²⁺

• Rahman Hosseinzadeh,
• Mohammad Nemati,
• Reza Zadmard and
• Maryam Mohadjerani

Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163

• a pronounced selectivity towards Cu2+ over other mono and divalent ions. The formation of the complex between L and Cu2+ was evaluated by absorption, fluorescence and 1H NMR spectroscopy. The sensor L showed a remarkable color change from colorless to purple and a fluorescence quenching only upon

• when excited at 280 nm. Upon addition 10 equiv of Cu2+ to the MeCN solution of sensor L, a remarkable fluorescence quenching was observed (Figure 4). In order to explore the selectivity of sensor L, similar experiments were carried out in the presence of other perchlorate salts of Cu2+, Hg2+, Pb2+, Zn2

• considerable fluorescence variations in comparison with L, and addition of Cu2+ ions to the corresponding solutions resulted in fluorescence quenching. Therefore, L can recognize Cu2+ even in the presence of other metal ions in acetonitrile solution. 1H NMR titration of L with Cu2+ In order to understand the