Search results
Search for "excited state" in Full Text gives 237 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Advances in nitrogen-containing helicenes: synthesis, chiroptical properties, and optoelectronic applications
Beilstein J. Org. Chem. 2025, 21, 1422–1453, doi:10.3762/bjoc.21.106
- displays red-shifted emission and prolonged fluorescence lifetimes as solvent polarity increases, indicating enhanced excited-state stabilization. Collectively, these studies offer valuable strategies for stabilizing long π-extended helicenes and finely tuning their chiroptical and emissive properties
- and high BCPL of 66.5 M−1 cm−1 underscore its potential for advanced chiral photonic applications. Heteroatom engineering in double helicenes has emerged as a powerful strategy for tuning chiroptical properties and excited-state dynamics. In 2021, Sakamaki’s group synthesized a novel double N,O-hetero
- sensitivity of chiral excited-state properties to heteroatom substitution within the helicene framework. Extending this design principle, the group reported a double N,S-hetero[5]helicene 58 constructed from two benzo[b]phenothiazine units in 2023 [73]. Compared to the N,O-analogue 57b, this new compound
Tautomerism and switching in 7-hydroxy-8-(azophenyl)quinoline and similar compounds
Beilstein J. Org. Chem. 2025, 21, 1404–1421, doi:10.3762/bjoc.21.105
- molecules good candidates for molecular switches [50]. Recently, we have developed a series of 7-hydroxyquinoline Schiff bases, where the tautomeric proton transfer causes intramolecular twisting upon irradiation [51]. The process happens in the excited state and the competition between proton transfer and
- forms, allowing long-range proton transfer starting from the enol, azo, (E) and finishing to the end keto form K. As described in similar compounds, ideally for switching, the process begins with excitation of E, which, in the excited state, exhibits excited-state proton transfer (PT) to KE*. This
- part is flexible, the excitation of E can lead to E/Z isomerization, which competes with the initial excited-state PT process, reducing its efficiency [52]. The theoretical data, collected in Table 1, can shed light on the potential energy landscape in the ground state for the studied compounds
Recent advances in amidyl radical-mediated photocatalytic direct intermolecular hydrogen atom transfer
Beilstein J. Org. Chem. 2025, 21, 1306–1323, doi:10.3762/bjoc.21.100
- pathway initiates with ground-state complexation 90 between HRP-12 and HFIP via hydrogen bonding. Following visible-light excitation of 90, intersystem crossing (ISC) from the S1(LE) to T2 state generates the catalytically competent triplet excited state 91. This N-centered radical species subsequently
Recent advances and future challenges in the bottom-up synthesis of azulene-embedded nanographenes
Beilstein J. Org. Chem. 2025, 21, 1272–1305, doi:10.3762/bjoc.21.99
- , it was reported that PAH 126 exhibits anti-Kasha fluorescence [80] from the S3 state in the range of 410–470 nm upon excitation at 370 nm. This was well verified by femtosecond time-resolved absorption spectroscopy (fs-TAS), with corresponding high-energy excited state absorption bands observed at
Recent advances in oxidative radical difunctionalization of N-arylacrylamides enabled by carbon radical reagents
Beilstein J. Org. Chem. 2025, 21, 1207–1271, doi:10.3762/bjoc.21.98
- intermediate B. Intermediate B undergoes cyclization to form the N-radical intermediate C, which can be further oxidized to the final product 35a by releasing a proton. Alternatively, intermediate C can be reduced by excited-state Ir(ppy)3, leading to the formation of the nitranion intermediate D. The Ir(III
- reaction mechanism was proposed (Scheme 26). The process begins with the generation of a difluoromethyl radical from S-(difluoromethyl)sulfonium salt 49 under the influence of an excited-state photocatalyst. This radical then adds to the double bond of N-arylacrylamide, forming intermediate radical 51
- -carbonyl bromide 67 through photoreduction by the excited state of the photocatalyst [IrIII*] (Scheme 33). The generated radical then undergoes addition to the diene, followed by 6-endo cyclization and deprotonation, ultimately forming the lactam product 68a. Notably, this process highlights the
Biobased carbon dots as photoreductants – an investigation by using triarylsulfonium salts
Beilstein J. Org. Chem. 2025, 21, 1024–1030, doi:10.3762/bjoc.21.84
- biocompatibility. The electrochemical properties of such materials have been then evaluated by cyclic voltammetry (CV). For all the properties mentioned above, CDs emerged as low-cost and sustainable photocatalysts. Indeed, upon visible-light irradiation, the generated excited state CD* can operate as either
On the photoluminescence in triarylmethyl-centered mono-, di-, and multiradicals
Beilstein J. Org. Chem. 2025, 21, 964–998, doi:10.3762/bjoc.21.80
- excitation wavelength (see Figure 1c). Excitation at 374 nm or 544 nm both lead to fluorescence with an identical fluorescence decay profile and identical ϕ of ≈2% (see Figure 1c). This behavior hints at the fact that the relaxed excited state, from which the emission occurs, is the same for excitation at
- the excited state dynamics, there is evidence for this fast relaxation in donor-functionalized TTM radicals [26]. Moreover, transient absorption has been employed to elucidate the formation of a non-luminescent side-product in trityl radicals. During photodegradation, two halogens are lost and two
- the molecule remains mostly planar in the excited state [37]. As a result, we observe weak emission in the yellow to red spectrum, because the respective transition remains symmetry forbidden. Circularly polarized photoluminescence PTM has been developed prior to TTM, as the first stable
Study of tribenzo[b,d,f]azepine as donor in D–A photocatalysts
Beilstein J. Org. Chem. 2025, 21, 935–944, doi:10.3762/bjoc.21.76
- is a particular interest in the obtainment of organic molecules with well-balanced redox potentials in the excited state that can act as bimodal photocatalysts, facilitating their use in oxidative and reductive quenching cycles. In this sense, it is crucial to understand the molecule's structure
- density distribution in the charge transfer (CT) excited state is facilitated by the presence of an electron-rich moiety and an electron-poor part in the same molecule, increasing the lifetime in the excited state. One of the representative classes of molecules demonstrating dual use in materials
- excited state. This results in a consistently planar conformation for donor b, while donor a can exhibit either a planar or bent conformation, depending on the nature of the substituent, as previously mentioned. This duality between planar and bent shapes is significant, as it contributes to the aromatic
Recent advances in controllable/divergent synthesis
Beilstein J. Org. Chem. 2025, 21, 890–914, doi:10.3762/bjoc.21.73
- mechanistic experiments and DFT calculations, the authors proposed a possible mechanism for the reaction: first, DPZ is excited by light to form the excited state DPZ*, which then oxidizes bromide ions through single-electron transfer to generate corresponding radical anions. These radical anions undergo
Light-enabled intramolecular [2 + 2] cycloaddition via photoactivation of simple alkenylboronic esters
Beilstein J. Org. Chem. 2025, 21, 854–863, doi:10.3762/bjoc.21.69
- prohibitively high in energy for selective reactivity [5]. The inception of energy transfer catalysis (EnT) has expedited discoveries concerning the photoactivation of organic molecules [15][16][17], enabling direct access to the triplet excited state through the use of a photocatalyst (Figure 1A, top
- isomerization of alkenes [18][19], [2 + 2] cycloadditions [20][21][22][23][24], and dearomative [4 + 2] cycloadditions [25][26][27]. When considering conjugated alkenes, the triplet excited state energy and excited state lifetime are intrinsically linked to the degree of conjugation and substitution of a
- scaffold (Figure 1A, bottom), with increasing excited state energy moving from stilbenes and conjugated dienes to simple dienes, styrenes and enones (not shown) [28]. Consequently, small truncated chromophores, such as simple alkenes remain an intractable challenge for efficient EnT due to prohibitively
Substituent effects in N-acetylated phenylazopyrazole photoswitches
Beilstein J. Org. Chem. 2025, 21, 830–838, doi:10.3762/bjoc.21.66
- studies on azobenzene [32][40]. Another interesting aspect, that could point to a more complex picture in the excited state landscape of these switches, is that the QYs of NAc-PAPs with R = NO2 and R = H are lower for the π→π* than for the n→π* transition, while for the other substituents the opposite was
Photochemically assisted synthesis of phenacenes fluorinated at the terminal benzene rings and their electronic spectra
Beilstein J. Org. Chem. 2025, 21, 670–679, doi:10.3762/bjoc.21.53
- wavelength region for the corresponding parent phenacenes whereas their fluorescence bands markedly red-shifted and broadened. These observations suggest that the intermolecular interactions of excited-state F8-phenacene molecules are significantly different from those of the corresponding parent molecules
- negative (orange region) in the parent compounds, whereas the phenacene cores turned to be positive (blue) for the F8-phenacenes. Therefore, one can manipulate the polarization of the phenacene cores through the introduction of fluorine atoms without altering the electronic spectral features. The excited
- -state electronic characteristics were also calculated, and the electronic transitions for the first two vertical absorption bands are summarized in Table 2. Although the calculated S1←S0 and S2←S0 electronic transition energies were slightly overestimated to show a systematic difference between the
Unprecedented visible light-initiated topochemical [2 + 2] cycloaddition in a functionalized bimane dye
Beilstein J. Org. Chem. 2025, 21, 500–509, doi:10.3762/bjoc.21.37
- )bimane (DMOCDO10) and syn-(Me,Me)bimane (DXABIM10) [26], a room temperature structure of Me4B (TNZBCO10) [27], and a planar syn-(H,ethynyl)bimane (WAYHEJ) [28]. Optical properties The optical properties of the three bimanes were measured to investigate differences in their excited state properties, as
- proposed pathway begins with the excitation of a bimane molecule to its singlet-excited state, followed by intersystem crossing (ISC) to the triplet state. The triplet state then forms an excimer complex with a neighboring bimane molecule, leading to the formation of a single bond and generating a triplet
Synthesis, structure, ionochromic and cytotoxic properties of new 2-(indolin-2-yl)-1,3-tropolones
Beilstein J. Org. Chem. 2025, 21, 358–368, doi:10.3762/bjoc.21.26
- the 7,8 (OH) form and is caused by the excited-state intramolecular proton transfer (ESIPT) process due to intramolecular O→N proton migration in the singlet excited state [26][27]. The ionochromic sensitivity of compounds 7a,b and 8a,b to anions was investigated in acetonitrile upon addition of tetra
Red light excitation: illuminating photocatalysis in a new spectrum
Beilstein J. Org. Chem. 2025, 21, 296–326, doi:10.3762/bjoc.21.22
- , where the low-lying excited state often corresponds to the metal-to-ligand charge transfer (MLCT) transition. As the atomic number increases, relativistic effects become more pronounced, leading to the contraction of s and p orbitals while the d and f orbitals expand and become more diffuse. While these
- excitation to the triplet state from the ground state S0. This effect mitigates rapid back-electron transfer from the singlet excited state to the ground state, extending the excited-state lifetime of the photocatalyst. Since the T1 → S0 transition is spin-forbidden, the process increases the overall
- study, the authors have developed a complementary ground-state- and excited-state-driven aryl oxidative addition platform based on an N,C,N-bismuthinidene complex, showing the unique capacity of this main-group element to engage in reactivity typically associated with d-block metals [21]. The study
Synthesis, structure and π-expansion of tris(4,5-dehydro-2,3:6,7-dibenzotropone)
Beilstein J. Org. Chem. 2025, 21, 1–7, doi:10.3762/bjoc.21.1
- in 3, which consume the energy of the excited state. Figure 4 shows the UV–vis absorption spectrum of 3 in cyclohexane with the absorption edge at 561 nm and its emission spectrum with a peak at 580 nm. In the test windows of cyclic voltammetry (Supporting Information File 1, Figure S1), 3 exhibits
Synthesis, characterization, and photophysical properties of novel 9‑phenyl-9-phosphafluorene oxide derivatives
Beilstein J. Org. Chem. 2024, 20, 3299–3305, doi:10.3762/bjoc.20.274
- the CT feature in the excited state. Further, the solvent dependence of 7-H exhibits good consistence with that reported by the Nishida group [31]. The PLQY and τDF values of the PhFlOP-based emitters 7 were measured in degassed toluene, and the corresponding data are included in Table 2, showing a
Advances in the use of metal-free tetrapyrrolic macrocycles as catalysts
Beilstein J. Org. Chem. 2024, 20, 3085–3112, doi:10.3762/bjoc.20.257
- to absorb significant amounts of visible light photons, which allows them to reach an excited state. The excited porphyrin molecule is likely to undergo energy transfer (ET; photosensitization) or single-electron transfer (SET; photoredox catalysis) to substrate molecules (Figure 13). In
- photochemistry, porphyrins are mainly used for the generation of singlet oxygen (1O2) or other reactive oxygen species. Porphyrins in the triplet excited state can relax to the ground state by transferring energy to molecular oxygen (triplet state) forming 1O2 (Figure 13b) [67]. Photosensitized singlet oxygen
- initiated the reaction pathway. The authors proposed that under light irradiation, the porphyrin transitioned to its excited state, generating a phenyl radical through photoinduced single-electron transfer (Figure 15c). This phenyl radical then added to the furan (heteroarene), forming an aryl radical
Extension of the π-system of monoaryl-substituted norbornadienes with acetylene bridges: influence on the photochemical conversion and storage of light energy
Beilstein J. Org. Chem. 2024, 20, 3061–3068, doi:10.3762/bjoc.20.254
- ones. This lack of correlation may indicate that several different factors and processes contribute to different extent to the course of the photoreaction, for example, steric hindrance and resulting torsion angles between the arene unit and norbornadiene, deactivation of the excited state by
Tunable full-color dual-state (solution and solid) emission of push–pull molecules containing the 1-pyrindane moiety
Beilstein J. Org. Chem. 2024, 20, 3016–3025, doi:10.3762/bjoc.20.251
- , indicating that the more polar singlet excited state (S1) was much better stabilized by polar solvents than the ground state (S0). The highest fluorescence quantum yield of about 87% was observed in toluene. Then, the solvatochromic properties of stilbazole 1i, bearing a stronger electron-donating
- S4, Supporting Information File 1) and the Kawski–Chamma–Viallet plots [59][60] (Figure 4, see Supporting Information File 1 for details) showed good linearity. This also indicated that the excited-state dipole moment of the molecules was much higher than that in the ground state. This phenomenon was
Advances in radical peroxidation with hydroperoxides
Beilstein J. Org. Chem. 2024, 20, 2959–3006, doi:10.3762/bjoc.20.249
- -AcrClO4 as the photocatalyst has been disclosed (Scheme 24) [67]. According to the authors, the irradiation of the photocatalyst (Acr+-Mes) A with a blue LED leads to the excited state (Acr·-Mes·+) B. The aliphatic carboxylic acid 66 is converted by deprotonation to the corresponding carboxylate, which is
- excited state [*IrIII(ppy)3] is likely to initiate a plausible catalytic cycle. Then TBHP is reduced by [*IrIII(ppy)3] through SET, which results in the generation of the tert-butoxy radical. Subsequently, the tert-butoxy radical abstracts a hydrogen atom from substrate 68 to give radical A
- –peroxidation of alkenes 155 with TBHP and aldehydes 156 through visible-light photocatalysis was developed using fac-Ir(ppy)3 as the photoredox catalyst (Scheme 49) [113]. Under visible light irradiation, the excited state Ir(III)* is generated, and the single electron transfer of Ir(III)* with TBHP results in
Recent advances in transition-metal-free arylation reactions involving hypervalent iodine salts
Beilstein J. Org. Chem. 2024, 20, 2891–2920, doi:10.3762/bjoc.20.243
- state, eosin Y*. This excited state further undergoes oxidation via a single-electron-transfer (SET) reaction with Ar2IBF4 26, producing eosin Y+ and a phenyl radical 30 (Scheme 10). The radical intermediate 30 selectively binds to the C2 position of either quinoline or pyridine N-oxide, forming
- mechanism by adding 2 equivalents of TEMPO to the reaction mixture. The absence of the desired product indicated the involvement of a radical pathway in the process. The proposed reaction mechanism begins with the activation of eosin Y by visible light from 5 W blue LEDs, transitioning it to its excited
Investigation of a bimetallic terbium(III)/copper(II) chemosensor for the detection of aqueous hydrogen sulfide
Beilstein J. Org. Chem. 2024, 20, 2818–2826, doi:10.3762/bjoc.20.237
- exhibited high luminescence (with a quantum yield of 68%) and displayed the characteristic trivalent terbium emission bands with emission peaks at 491 nm, 545 nm, 583 nm, and 621 nm, corresponding to transitions from the 5D4 excited state to the 7F6, 7F5, 7F4, and 7F3 ground states, respectively (Figure 2
Photoluminescence color-tuning with polymer-dispersed fluorescent films containing two fluorinated diphenylacetylene-type fluorophores
Beilstein J. Org. Chem. 2024, 20, 2682–2690, doi:10.3762/bjoc.20.225
- diphenylacetylene structure as the π-conjugated core. As a part of our research projects, we have begun to explore diphenylacetylene-based luminescent molecules despite diphenylacetylene not exhibiting fluorescence at room temperature because it undergoes a πσ* excited state that rapidly forms a trans-bend
- structure (Figure 1a) [14][15][16]. Our extensive efforts have revealed that introducing electron-donating alkoxy and electron-withdrawing cyano groups at both ends of the diphenylacetylene scaffold slows the internal conversion to the πσ* excited state. Further incorporating four fluoro substituents in the
A review of recent advances in electrochemical and photoelectrochemical late-stage functionalization classified by anodic oxidation, cathodic reduction, and paired electrolysis
Beilstein J. Org. Chem. 2024, 20, 2500–2566, doi:10.3762/bjoc.20.214
- excited state, Mes-Acr+*. This excited state then reductively interacts with the sulfinate anion to produce a CF3 radical. The CF3 radical subsequently attacks the target substrate, forming an intermediate radical, which undergoes further oxidation to yield the desired product (Scheme 47a). The Wu group
Other Beilstein-Institut Open Science Activities
