Search results
Search for "emission" in Full Text gives 483 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Applications of microscopy and small angle scattering techniques for the characterisation of supramolecular gels
Beilstein J. Org. Chem. 2024, 20, 2608–2634, doi:10.3762/bjoc.20.220
- systems are indeed representative. CLSM also often has poor resolution due to the use of light used for imaging. Other fluorescent imaging techniques such as super resolution fluorescence microscopy (for example, stimulated emission depletion (STED) microscopy or point accumulation for imaging in
- between the beam and sample result in the emission of secondary scattered electrons, back-scattered electrons and X-rays which can be detected to produce an image. In contrast, TEM can measure the bright-field image, among other modes, by blocking the scattered electrons and detecting only the unscattered
Anion-dependent ion-pairing assemblies of triazatriangulenium cation that interferes with stacking structures
Beilstein J. Org. Chem. 2024, 20, 2567–2576, doi:10.3762/bjoc.20.215
- introduction of N-aryl units during the synthesis is rendered difficult owing to steric hindrances. For example, N-phenyl-substituted TATA+ cation 1b+ (Figure 1) [26] exhibited slightly red-shifted absorption and emission, with a higher quantum efficiency compared to those of N-alkyl-substituted TATA+ cations
- desorption ionization time-of-flight mass spectrometry (MALDI–TOF MS). The synthesized ion pairs showed similar electronic properties in solution state. In CH3CN, 2+-BF4− exhibited UV–vis absorptions at 273, 350, and 524 nm and fluorescence emission at 607 nm upon excitation at 524 nm. The absorption band at
Metal-free double azide addition to strained alkynes of an octadehydrodibenzo[12]annulene derivative with electron-withdrawing substituents
Beilstein J. Org. Chem. 2024, 20, 2234–2241, doi:10.3762/bjoc.20.191
- outer side (in-out-ts), but the thermodynamically stable final product is a regioselective “in-in” adduct, i.e., compound 6a. Optical properties Absorption and emission spectra of 6a were measured in CH2Cl2 (Figure 5). The conjugation is changed and a highly-twisted macrocyle forms by the double azide
- addition. Thus, compound 6a shows an ultraviolet absorption peak at 249 nm (λmax) and no absorption in the visible region was observed. When excited at 249 nm, an emission band at 513 nm (λem) appeared in the spectrum with a fluorescence quantum yield (Φ) of 7.0%. The absorption and fluorescence spectra
- were almost independent of solvents. For example, the λem in CHCl3 and THF was 514 nm (Figure S11 in Supporting Information File 1). The double benzyl azide adduct of DBA-OHex displayed similar absorption and emission spectra with a λmax of 247 nm and λem of 539 nm in CH2Cl2. Since the Stokes shift of
Novel truxene-based dipyrromethanes (DPMs): synthesis, spectroscopic characterization and photophysical properties
Beilstein J. Org. Chem. 2024, 20, 2163–2170, doi:10.3762/bjoc.20.186
- –80%) along with their preliminary photophysical (absorption, emission and time resolved fluorescence lifetime) properties. The condensation reaction for assembling the required DPMs were catalyzed with trifluoroacetic acid (TFA) at 0 °C to room temperature (rt), and the stable dipyrromethanes were
- derivatives were successfully characterized and their structures were established by means of the 1H and 13C NMR spectroscopy, besides further confirmation by mass spectrometry (see Supporting Information File 1). The UV–vis absorption, emission and time-resolved fluorescence spectra Emission and absorption
- ). Interestingly, even though we observed variations in the absorption spectra for thus prepared truxene-based molecules, but all the truxene derivatives displayed almost similar types of the emission spectra under identical conditions except the variations in the intensities of the bands. The bands observed for
A new platform for the synthesis of diketopyrrolopyrrole derivatives via nucleophilic aromatic substitution reactions
Beilstein J. Org. Chem. 2024, 20, 1933–1939, doi:10.3762/bjoc.20.169
- parts per million (ppm) and the coupling constants (J) in hertz (Hz). UV–vis spectra were recorded on a Shimadzu UV-2501PC spectrophotometer using DMF as the solvent. The emission spectra were recorded with a Jasco FP-8300 spectrofluorometer using DMF as the solvent. Mass spectra were recorded using a
- Micromass Q-TOF-2TM mass spectrometer and CHCl3 as the solvent. The NMR, absorption and emission spectra of the new compounds are shown in Supporting Information File 1. Synthesis 3,6-Bis(4-chlorophenyl)-2,5-bis(pentafluorobenzyl)-2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione (2) A suspension of DPP 1 (1 g
- . Synthesis of new diketopyrrolopyrroles via nucleophilic aromatic substitution. Spectroscopic data for the new compounds (between 1 × 10–6 M and 4 × 10–5 M in DMF). Supporting Information Supporting Information File 18: 1H NMR, 13C NMR and 19F NMR spectra; MS, UV–vis and emission spectra. Funding Thanks
The Groebke–Blackburn–Bienaymé reaction in its maturity: innovation and improvements since its 21st birthday (2019–2023)
Beilstein J. Org. Chem. 2024, 20, 1839–1879, doi:10.3762/bjoc.20.162
Synthesis and characterization of 1,2,3,4-naphthalene and anthracene diimides
Beilstein J. Org. Chem. 2024, 20, 1767–1772, doi:10.3762/bjoc.20.155
- 8-Ph, with λmax = 489 and 499 nm, respectively. These absorption features are roughly comparable to other naphthalene and anthracene diimides that have been reported in the literature. The emission profiles of all four compounds are shown in Figure 3b. While N,N’-dibutyl-1,4,5,8-naphthalene diimide
- has low fluorescence intensity (Φ = 0.006) [20], 7-Hex emits more efficiently with Φ = 0.41. Interestingly, 7-Ph has nearly no emission intensity, as evidenced by the low signal-to-noise ratio in the data and a near-zero quantum yield when excited at 400 nm. This fluorescence quenching is likely
- related to non-radiative emission that is observed for N-phenyl-substituted imides [21]. It is possible this effect is more significant for 7-Ph than 8-Ph because the naphthalene core is less conformationally locked than the anthracene scaffold. As is expected for aromatic diimides, the title compounds
A fiber-optic spectroscopic setup for isomerization quantum yield determination
Beilstein J. Org. Chem. 2024, 20, 1684–1692, doi:10.3762/bjoc.20.150
- with narrow bandwidths, the emission spectrum can be included in the rate equations. This correction is done by multiplying Equation 5 by the spectral distribution f(λ) of the light source and integrating over all wavelengths [45]: where Setup The UV–vis irradiation experiments were performed using a
- monochromatic light at first [24][49]. We chose the peak of the emission spectrum of the LED as the approximated monochromatic wavelength, since this value can substantially differ from the nominal wavelength of the LED, e.g., the 455 nm LED from ThorLabs has a peak in the emission spectrum at 445 nm. We
- furthermore determined the quantum yields again, taking the emission spectrum of the LED into account. The emission spectra were measured using our spectrometer by connecting the LEDs to the detector (Figure S1 in Supporting Information File 1). The following input parameters were used in both methods: the
Supramolecular assemblies of amphiphilic donor–acceptor Stenhouse adducts as macroscopic soft scaffolds
Beilstein J. Org. Chem. 2024, 20, 1590–1603, doi:10.3762/bjoc.20.142
- observed compared to the THF solution (Figure 1a, black line), possibly due to supramolecular assembly in aqueous medium. Because of the broad absorption range of DA11 in aqueous medium, photoisomerization could not be effectively accomplished by a 625 nm LED light source with a narrow emission wavelength
- range, similarly to our previously studies [37]. Thus, a white-light source with a broad emission wavelength range was employed for the photoisomerization of DAn in aqueous medium. Photoisomerization of DA11 was induced by white-light irradiation for 60 min at 20 °C (Figure 2a, orange line), upon which
Benzylic C(sp3)–H fluorination
Beilstein J. Org. Chem. 2024, 20, 1527–1547, doi:10.3762/bjoc.20.137
- from financial and waste perspectives when compared to reagents such as Selectfluor and NFSI [75][76][77]. This type of fluorine source is also preferred for positron emission tomography (PET) imaging with [18F]fluoride [78]. Despite the challenges associated with nucleophilic fluoride, including
Synthesis and optical properties of bis- and tris-alkynyl-2-trifluoromethylquinolines
Beilstein J. Org. Chem. 2024, 20, 1246–1255, doi:10.3762/bjoc.20.107
- –10°. Optical properties Steady-state absorption and fluorescence measurements were carried out. Compounds 6a, 9a, and 12a were selected to study the impact of the position of the alkynyl group on the optical properties. Comparison of the absorption and emission features of 12a, 12b and 12c gives
- , respectively. A bathochromic shift is observed from 9a over 6a to 12a in the first absorption maximum with a total of 0.29 eV. This trend can be observed in the emission spectrum as well. All three emission spectra are characterized by a single broad emission peak which is almost identical for 6a and 12a and
- and 12a are almost identical in their emission. The influence of the type of substituent located at the alkyne moieties of 12a, 12c, and 12e was also studied. The intensity increases from 12a to 12e and a bathochromic shift of the absorption maxima can be observed. Interestingly, the emission spectra
Mechanistic investigations of polyaza[7]helicene in photoredox and energy transfer catalysis
Beilstein J. Org. Chem. 2024, 20, 1236–1245, doi:10.3762/bjoc.20.106
- potentials of Aza-H and the substrates and initial steady-state fluorescence quenching experiments (Scheme 1, left), but detailed mechanistic insights and direct evidence of the transient radical ions could not be obtained yet [45]. Figure 1A illustrates the absorption and emission spectra of Aza-H in MeCN
- radical ions of polyazahelicenes. The moderate fluorescence quantum yield of 48% (in MeCN) [46] implies that a non-emissive triplet-excited state (at room temperature) could also be generated via intersystem crossing, potentially initiating electron transfer reaction sequences. 77 K emission measurements
- were thus carried out and they showed short-lived fluorescence and long-lived emission (phosphorescence) that was assigned to the triplet state of Aza-H with an energy of 2.32 eV (Figure 1A). Quantum mechanical computations of the Aza-H triplet state yielded a triplet energy of 2.17 eV (adiabatic
Kinetically stabilized 1,3-diarylisobenzofurans and the possibility of preparing large, persistent isoacenofurans with unusually small HOMO–LUMO gaps
Beilstein J. Org. Chem. 2024, 20, 1099–1110, doi:10.3762/bjoc.20.97
- isobenzofurans 2, 3 and 23 were studied by UV–vis and fluorescence spectroscopies (Figure 5). Compound 2 is devoid of ortho groups on its 1,3-diphenyl substituents and shows the longest wavelengths of absorption (λmax = 415 nm) and emission (emission λmax = 484 nm) in this series, consistent with a more highly
- conjugated π-system in which the 1,3-diphenyl substituents lie flat or nearly flat relative to the isobenzofuran backbone. Likewise, compound 2 is yellow while compounds 3 and 23 are colorless. Compounds 3 and 23 show similar absorption (λmax = 364 and 360 nm for 3 and 23, respectively) and emission (λmax
- solutions of 1,3-diarylisobenzofurans 2, 3 and 23 in CH2Cl2 solvent. The vials of 2, 3 and 23 showing fluorescence emission (bottom) were excited at 365 nm. Calculated HOMO and LUMO orbitals for parent isobenzofuran (1) and 1,3-diarylisobenzofuran derivatives 2, 3, 23, 24 and 25 using a DFT method performed
Light on the sustainable preparation of aryl-cored dibromides
Beilstein J. Org. Chem. 2024, 20, 1076–1087, doi:10.3762/bjoc.20.95
- evaluated, through the use of different types of lamps, particularly those with partial UV emission. In a specific implementation, in consideration of the glass filter’s capabilities, some UV emitting diodes were inserted inside the vessel. Anyway, no significant modulation was observed, probably due to the
Auxiliary strategy for the general and practical synthesis of diaryliodonium(III) salts with diverse organocarboxylate counterions
Beilstein J. Org. Chem. 2024, 20, 1020–1028, doi:10.3762/bjoc.20.90
- presence or absence of transition metal catalysts under thermal or photochemical conditions [2][3][4][5]. Furthermore, these compounds have practical applications in the synthesis of radiochemicals utilized in positron emission tomography (PET) imaging [6], as well as serving as photoacid generators for
- benzoate in 70% yield (Scheme 6A). Furthermore, iodonium salt 7aj with an umbelliferone-3-carboxylate counterion displayed extremely weak blue fluorescence emission under 365 nm UV light compared to free carboxylic acid 6j. This unique property was utilized for tracing the counterion exchange process of
- the diaryliodonium(III) salt by irradiating with 365 nm UV light. The counterion exchange in umbelliferone carboxylate salt 7aj with trifluoroacetic acid was rapid, and after 30 s, the completion of the reaction was confirmed by the emergence of strong blue fluorescence emission due to the liberation
Synthesis and properties of 6-alkynyl-5-aryluracils
Beilstein J. Org. Chem. 2024, 20, 898–911, doi:10.3762/bjoc.20.80
- already discussed for 5d, this again reinforces the assumption that this phenomenon could be caused by a π-donor at 5-position, regardless of its structure. Further investigation is required, but if confirmed, this could be used to create specific desired absorption behaviors. Subsequently, the emission
- spectra were investigated. As explained in the previous section, a similar behavior was observed in the emission spectra with respect to the substitution pattern. In general, a bathochromic shift of the emission was observed in the presence of a dimethylamino group at the 5-position. The bathochromic
- bathochromic shift of 5m is 57 nm and lies between the two emission peaks of 5d and 5k. Therefore, it can be concluded that combining the two substitution patterns leads to this intermediate behavior. Substitution of the 5-π-donor with a π-acceptor group reduced the bathochromic shift from 57 nm to 18 nm
SOMOphilic alkyne vs radical-polar crossover approaches: The full story of the azido-alkynylation of alkenes
Beilstein J. Org. Chem. 2024, 20, 701–713, doi:10.3762/bjoc.20.64
- to 80 °C instead of using light to form the radical only afforded traces of the product (Table 1, entry 2). Changing the solvent to DCE slightly increased the yield (Table 1, entry 3). Blue light with an emission spectrum centered around 467 nm was initially selected since Ph-EBX is known to absorb
Isolation and structure determination of a new analog of polycavernosides from marine Okeania sp. cyanobacterium
Beilstein J. Org. Chem. 2024, 20, 645–652, doi:10.3762/bjoc.20.57
- in 100 mL phosphate-buffered saline) was added to each well. The plates were incubated for an additional 3 h. The plates were read in a SpectraMax Gemini XS microplate fluorescence scanner (Molecular Devices) using an excitation wavelength of 536 nm and an emission wavelength of 588 nm. WI-38 cells
Synthesis of photo- and ionochromic N-acylated 2-(aminomethylene)benzo[b]thiophene-3(2Н)-ones with a terminal phenanthroline group
Beilstein J. Org. Chem. 2024, 20, 552–560, doi:10.3762/bjoc.20.47
- change of the solutions from yellow to dark orange. Subsequent selective interaction with AcO− led to the restoration of the initial absorption and emission properties. Thus, the obtained compounds represent dual-mode “on–off–on” switches of optical and fluorescent properties under sequential exposure to
- absorption spectra, induced in one or both directions by absorption of electromagnetic radiation [1][2][3][4]. Due to the different structures and the different optical and emission properties of these forms, photochromic compounds are used in 3D optical memory devices, photoswitches of different types
- -Acylated compounds 2a–c in solutions exhibited fluorescence in the region of 465–468 nm, and the excitation emission spectra agreed well with the absorption spectra (Figure 1). Compounds 2a–c in solutions demonstrated a typical negative photochromism [1][16] when irradiated with visible light of 436 nm
Switchable molecular tweezers: design and applications
Beilstein J. Org. Chem. 2024, 20, 504–539, doi:10.3762/bjoc.20.45
- arms with planar Pt complexes are parallel and the distance between them allows for the intercalation of another terpy-Pt complex. The guest intercalation coupled with the induction of short-range Pt–Pt interactions was followed by UV–vis absorption and emission spectroscopies with characteristic MMLCT
- using a similar principle [24]. The protection from the solvent of the intercalated Pt guest enables its fluorescence emission and is accompanied by the induction of chirality in the resulting host–guest complex. A significant enhancement of the circular dichroism response of the chiral guest is
- chiroptical properties with a large change in the absorption spectra and a bathochromic shift in the emission maximum. This system represents a rare example of a multi-output readout system, showing responses in ECD, fluorescence, and CPL activity. The authors later reported a similar system with a bipyridine
Development of a chemical scaffold for inhibiting nonribosomal peptide synthetases in live bacterial cells
Beilstein J. Org. Chem. 2024, 20, 445–451, doi:10.3762/bjoc.20.39
- fluorescence scanning (excitation wavelength, 532 nm; emission wavelength, 580 nm). The labeling of GrsA by probe 3 was completely suppressed by the addition of inhibitors 1, 2, 4, 5, and 7 (Figure 4a). In contrast, inhibitors 6, 8, and 9 moderately inhibited labeling, which was consistent with the decreased
Facile approach to N,O,S-heteropentacycles via condensation of sterically crowded 3H-phenoxazin-3-one with ortho-substituted anilines
Beilstein J. Org. Chem. 2024, 20, 336–345, doi:10.3762/bjoc.20.34
- -phenoxazin-3-ones 4, compounds 5 and 6 display intense fluorescence in solution at room temperature (Figure 5). The excitation spectra of the compounds (Figures S7–S11, Supporting Information File 1) correspond to the longest-wavelength absorption bands. The absorption and emission spectra of benzo[5,6][1,4
- , angles, and important crystallographic parameters are given in Tables S6 and S7, Supporting Information File 1. Hydrogen atoms are omitted for clarity. a) UV–vis (solid lines) and fluorescence emission (λex = 365 nm, dashed) spectra of compounds 5a–c (toluene, c = 2 10−5 M, l = 1 cm). b) Solutions of
- compounds 5a–c in toluene before irradiation (no emission) and c) during irradiation (photoluminescence, λex = 365 nm) at room temperature. UV–vis (solid lines) and fluorescence emission (dashed, λex = 365 nm) spectra of compounds 6a,b in toluene (c = 2 10−5 M, l = 1 cm) at room temperature. UV–vis
Catalytic multi-step domino and one-pot reactions
Beilstein J. Org. Chem. 2024, 20, 254–256, doi:10.3762/bjoc.20.25
- in the Full Research Paper by Nath and co-workers. The newly synthesized porphyrin derivatives displayed significant red-shifted absorption and emission compared to simple meso-tetraarylporphyrins [14]. The Carlone group reports an Enders-type triple cascade reaction toward cyclohexenals, using
Perspectives on push–pull chromophores derived from click-type [2 + 2] cycloaddition–retroelectrocyclization reactions of electron-rich alkynes and electron-deficient alkenes
Beilstein J. Org. Chem. 2024, 20, 125–154, doi:10.3762/bjoc.20.13
- -emission (AIE)-active aggregates exhibit emissive behavior in hexane, with an emission peak at 679 nm and a shoulder at 717 nm along with a fluorescence quantum yield of 8.5%. This luminescence phenomenon can be aptly considered to be AIE, considering the pronounced constraints imposed on molecular
- rotation in the aggregate state, including rotation around the central single bond of the TCBD moiety. Regarding the anthracene-embedded TCBD 19 in dichloromethane, no emission signal was observed. However, in the powdered form or sparsely distributed rigid matrices, a broad emission spectrum was observed
- [138]. Compounds 55 and 56 remain devoid of emissive characteristics even when in a solution or a solid state [129]. When compound 50 was characterized using a standard steady-state fluorimeter, no emission signals were observed across the visible and NIR regions extending up to 1,600 nm, both in a
Photoinduced in situ generation of DNA-targeting ligands: DNA-binding and DNA-photodamaging properties of benzo[c]quinolizinium ions
Beilstein J. Org. Chem. 2024, 20, 101–117, doi:10.3762/bjoc.20.11
- points were measured with a melting point apparatus BÜCHI 545 (Büchi, Flawil, CH) and are uncorrected. The absorption spectra were recorded on a Varian Cary 100 Bio absorption spectrometer with Hellma quartz glass cuvettes 110-QS (layer thickness d = 10 mm). The emission spectra were recorded on a
- titration of ct DNA to 3c (A), 3e (B), 3f (C), and 3g (D) (c = 20 µM) in Na phosphate buffer (pH 7.0, T = 20 °C, cNa+ = 16 mM). The arrows indicate the development of the emission bands during titration. Inset: plot of relative emission intensity versus cDNA. CD (A) and LD (B) spectra of 3f and ct DNA (cDNA
- ]quinolizinium ions 3b–g (yields in % refer to isolated products). Proposed mechanisms for the photoinduced DNA damage initiated by photoexcitation of benzoquinolizinium 3f. Absorption and emission maxima of 3c–g in the absence and presence of ct DNA and binding constants of their complexes with ct DNA. Gel
Other Beilstein-Institut Open Science Activities
