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Search for "triplet state" in Full Text gives 66 result(s) in Beilstein Journal of Organic Chemistry.
Photophysics and photochemistry of NIR absorbers derived from cyanines: key to new technologies based on chemistry 4.0
Beilstein J. Org. Chem. 2020, 16, 415–444, doi:10.3762/bjoc.16.40
- these into the triplet state and brings benefits known from UV systems to NIR systems either. This can be the generation of singlet oxygen and would enable the use of NIR absorbers in photodynamic therapy. Another benefit can be seen to increase the efficiency of photoinduced electron transfer needed in
p-Pyridinyl oxime carbamates: synthesis, DNA binding, DNA photocleaving activity and theoretical photodegradation studies
Beilstein J. Org. Chem. 2020, 16, 337–350, doi:10.3762/bjoc.16.33
- affinity of selected both active and non-active derivatives. Preliminary theoretical studies were performed, in an effort to explain the reasons why some derivatives cause photocleavage and some others not, which were experimentally verified using triplet state activators and quenchers. These theoretical
- . For the dissociation reaction of compound 12 in the triplet state, the molecule passes through a very small energy barrier and dissociates finally into its photoproducts which are the two ground state radicals indicated in Scheme 2. The almost negligible change in geometry on going from T1 min to T1
- barriers are very large, 29.37 kcal/mol for T1 and 31 kcal/mol for the S1 state. Hence, 11 does not show any photoreactivity, in accordance with our experimental results. Photoexcitation in the presence of a triplet state energy activator and a triplet state quencher Triplet photosensitizers (TPSs) or
Recent developments in photoredox-catalyzed remote ortho and para C–H bond functionalizations
Beilstein J. Org. Chem. 2020, 16, 248–280, doi:10.3762/bjoc.16.26
- Figure 3, E0,0 is the energy gap between the ground state and the lowest triplet state, corresponding to the band gap in semiconductors. C–H acylation Decarboxylative acylation of acetanilides: In 2015, Wang and co-workers first reported the acylation of acetanilides via C–H functionalization using
Experimental and computational electrochemistry of quinazolinespirohexadienone molecular switches – differential electrochromic vs photochromic behavior
Beilstein J. Org. Chem. 2019, 15, 2473–2485, doi:10.3762/bjoc.15.240
- calculating excited and ground-states, the triplet T0 state was used instead of the singlet S1 state as the photochemical intermediate (SW*) for computational purposes. Since T0 is the lowest energy triplet state, it is amenable to a ground-state computation. While the real SW* photochemical intermediate may
Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex
Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229
- of the photochromic reactions to visible light are to extend the π-conjugation and to utilize photosensitizers. Especially, triplet photosensitizers, which form the triplet state of a molecule by the triplet–triplet energy transfer, have been frequently used in photoresists, photodynamic therapy, and
Fluorescent phosphorus dendrimers excited by two photons: synthesis, two-photon absorption properties and biological uses
Beilstein J. Org. Chem. 2019, 15, 2287–2303, doi:10.3762/bjoc.15.221
- intersystem conversion towards a triplet state (T1), from which there will be emission of phosphorescence, having generally a lifetime longer than that of fluorescence. This classical one-photon excited fluorescence has led to the design of numerous types of chemical entities since the XIX century. For
Synthesis and properties of sulfur-functionalized triarylmethylium, acridinium and triangulenium dyes
Beilstein J. Org. Chem. 2019, 15, 2133–2141, doi:10.3762/bjoc.15.210
- enhanced internal conversion or intersystem crossing to the triplet state. Further photophysical work will have to settle this issue and thereby suggest structural improvements and/or the best applications of these dyes. Conclusion The effective introduction of alkylthiol groups into the para-positions of
Naphthalene diimides with improved solubility for visible light photoredox catalysis
Beilstein J. Org. Chem. 2019, 15, 2043–2051, doi:10.3762/bjoc.15.201
- catalysis is mainly [Ru(bpy)3]2+ [21], due to its strong MLCT (metal-to-ligand charge transfer) absorption, the excellent yield of its triplet state and the long lifetime, the versatile redox behavior (Ru3+ vs Ru+) in quenching processes and the chemical and photochemical robustness. Despite their positive
- fluorescence quantum yields are rather low and fluorescence lifetimes are rather short due to ISC into the triplet state [50][51]. NDIs are reversibly reducible and their stable radical anions absorb in the visible to NIR light range [37]. The aromatic core of NDIs can be easily modified by substituents in
Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response
Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139
- aggregation and the shielding effect of PMCD against quenching of the TPPS triplet state [37]. Also, it has been employed in the construction of photovoltaic materials and light-harvesting systems [38][39]. The complexation of GC5A with ACQ dyes generally has the advantage of strong binding affinities
- singlet state 1MLCT can undergo ultrafast intersystem crossing leading to the formation of the triplet state 3MLCT which could emit phosphorescence. Ru(dcbpy)3 was employed as a representative candidate in this work to study the photophysical response upon complexation with GC5A. Almost no appreciable
Degenerative xanthate transfer to olefins under visible-light photocatalysis
Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283
- is initiated through triplet-sensitization of xanthates by the long-lived triplet state of the iridium-based photocatalyst. Keywords: energy transfer; olefin; photocatalysis; radical; xanthate; Introduction A degenerative radical transfer of xanthates to olefins has been developed as a robust
- report a photocatalytic degenerative radical transfer of xanthates to olefins using an iridium-based photocatalyst under blue LED irradiation (Scheme 1C). A series of mechanistic investigations identified that the process involves a triplet-sensitization of the xanthates by the long-lived triplet state
- previously been ascribed to the absorption of the xanthic acid radical formed plausibly from homolytic C–S bond cleavage of the short-lived triplet state of xanthate 1a [22]. The ns-TA spectra of photocatalyst 8 (25 μM) in the presence of xanthate 1a (40 mM) in degassed DMSO at various delay times are shown
Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region
Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282
- mechanisms. From a single or triplet state of the photoredox catalyst, an electron is transferred. According to Rehm–Weller, an electron can be transferred from the electron donor to the electron acceptor in the excited state if the free energy change ∆Get is negative. ∆Get can be calculated from the
- localization of the electrons on the triplet state, which upconvert to the singlet state thermally (i.e., at room temperature) and can promote a radiative decay from the singlet excited state. This property gives to TADF complex lifetime of their excited state comparable to the lifetime of the excited state of
- example [80]. The triplet excited state is obtained. From the triplet state of carbazole, similar reactions with ruthenium triplet state (reactions 1, 2, and 3 in Section 2.1.1) can be observed. Moreover, as both oxidation and reduction potential are compatible with additives presented in Scheme 1, both
Novel photochemical reactions of carbocyclic diazodiketones without elimination of nitrogen – a suitable way to N-hydrazonation of C–H-bonds
Beilstein J. Org. Chem. 2018, 14, 2250–2258, doi:10.3762/bjoc.14.200
- Michler’s ketone, with different levels of triplet state energy were tested. Furthermore, to clearly demonstrate the difference of light-induced reactions of diazo compounds 1 in the triplet and singlet excited states, the direct photolysis of diazodiketones 1a-c without sensitizers was also examined
Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)
Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18
- delayed fluorescence (TADF) emitters. As specificity, these materials can thermally repopulate the singlet state from the triplet state by reverse intersystem crossing (RISC), leading to an increase of the luminescence intensity. From the OLEDs viewpoint, TADF emitters behave by harvesting both singlet
- and triplet excitons for radiative transition, excepted that the emission occurs from the singlet state and not from the triplet state (as observed for metal complexes) and that the triplet–triplet annihilation commonly observed with phosphorescent OLEDs [10] can be drastically reduced (see Figure 1
- , demonstrating their T1 states to be 3LE states. Conversely, only a broad spectrum was obtained for T21, and its triplet state was assigned to a 3CT state. Precisely, by its large dihedral angle, T21 differs from T20, T22 and T23 by the order of its orbitals, 3LE and 3CT being inverted in this case. Analysis of
Pyrene–nucleobase conjugates: synthesis, oligonucleotide binding and confocal bioimaging studies
Beilstein J. Org. Chem. 2017, 13, 2521–2534, doi:10.3762/bjoc.13.249
- fluorescence intensity and fast decay of fluorescence were rationalized by the presence of low-energy nπ* excited states. In particular, for the lowest excited singlet state 1ππ* efficient intersystem crossing to a triplet state 3nπ* close in energy can be expected according to the El-Sayed rule. Then, this
- carbonyl compound 3 as compared to the hydroxy compound 5. The computations reveal several triplet states below the lowest singlet excited state. In particular, the carbonyl pyrene derivative 3 displays a triplet state of nπ* character being lower in energy than the emissive singlet state S1 (being a
Novel β-cyclodextrin–eosin conjugates
Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52
- being excited with visible light, the PS – while reverting to the ground state – transfers the energy of its lowest excited triplet state to nearby molecular oxygen. This leads to an in situ generation of singlet oxygen (1O2), which is the main responsible species for cytotoxic reactions in cells [6
- tentatively be attributed to populations of fluorophores probably interacting in a different way with the CD cavity. As outlined in the introduction, singlet oxygen, 1O2, is the key species involved in PDT and it is generated by energy transfer from the excited triplet state of a PS and the nearby molecular
- dye in the same solvent (ΦΔ = 0.49) [31]. This result excludes any significant intra- or interencapsulation of the excited triplet state of the dye within the β-CD. If this was the case, the reduced quenching by oxygen due to steric hindrance would have resulted in a much smaller value for ΦΔ. The
A self-assembled cyclodextrin nanocarrier for photoreactive squaraine
Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248
- appropriate wavelength. Irradiation of the PS causes its transition to the excited singlet state and, via intersystem crossing; the PS reaches its triplet state. Electron transfer occurs upon relaxation to the ground state. This process can take place in two ways distinguished as type I and II mechanisms [5
Synthesis and characterization of fluorinated azadipyrromethene complexes as acceptors for organic photovoltaics
Beilstein J. Org. Chem. 2016, 12, 1925–1938, doi:10.3762/bjoc.12.182
- fluorinated derivatives allow access to triplet state blue light-emitters [13]. This work further investigates the effects of fluorination in n-type materials for OPVs. A series of selectively fluorinated ADP derivatives based on WS3 were synthesized (Figure 2). To understand the effect of the fluorination
On the cause of low thermal stability of ethyl halodiazoacetates
Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155
- obtain an energy difference between the singlet and triplet electronic spin state (Figure 3). The singlet–triplet energy gap is 4.1 kcal/mol in favor of the triplet state for the EDA-generated carbene. All three carbenes generated from 2a–c on the other hand have singlet ground states. The singlet
Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems
Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115
- ], whereas tiaprofenic acid (TPA) is a related drug that includes the 2-benzoylthiophene (BZT, Figure 1) chromophore and has a π,π* lowest triplet excited state [9][10]. Generally, the photochemical reactivity of the n,π* triplet state is higher than that of π,π* triplet state. It is also accepted that
Synthesis of 2,1-benzisoxazole-3(1H)-ones by base-mediated photochemical N–O bond-forming cyclization of 2-azidobenzoic acids
Beilstein J. Org. Chem. 2016, 12, 874–881, doi:10.3762/bjoc.12.86
- through a 1,5-electrocyclization reaction [56][57]. Nonreacted singlet nitrenes A may undergo intersystem crossing (ISC) into the less reactive triplet state (Scheme 1, intermediate D). Although a multiplicity change is a spin-forbidden transition, it can be partially allowed in some cases. According to
- intersystem crossing for the initially formed singlet nitrenes (Scheme 1, intermediate A) to the triplet state (Scheme 1, intermediate D), thus resulting in decreased yields of the cyclization products 2c–e. In these cases, the formation of the triplet nitrene D should lead to increased yields of primary
Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions
Beilstein J. Org. Chem. 2016, 12, 549–563, doi:10.3762/bjoc.12.54
- several clinical diseases [12][21]. One of the most commonly used thiobase for PDT applications is S4TdR, whose triplet state is generated upon photoexcitation with a quantum yield of one [22][23][24][25][26]. Under these conditions the production of reactive oxygen species (ROS), well-known toxic agents
Surprisingly facile CO2 insertion into cobalt alkoxide bonds: A theoretical investigation
Beilstein J. Org. Chem. 2015, 11, 1340–1351, doi:10.3762/bjoc.11.144
- -unrestricted calculations, a triplet state was considered and the minima of the corresponding spin-restricted calculations were used as initial structures. It turned out that the total energy of the geometrical optimised structures with triplet state was higher than the total energy of the spin-restricted
Photorelease of phosphates: Mild methods for protecting phosphate derivatives
Beilstein J. Org. Chem. 2014, 10, 2038–2054, doi:10.3762/bjoc.10.212
- benzyl (30b–d) moieties, and naphthylacetyl [37] reportedly lowered the singlet and triplet state energies only modestly [10][11] and were unsuitable because these chromophores remained intact and in competition for incident radiation. Photolysis of 1,4-HNA DEP (14a) in 1% aq MeOH released DEP with
- favored by aqueous-based solvents that serve both as a proton donor and an acceptor to the conjugate base generated from the chromophore’s triplet state heterolytic cleavage of the leaving group. The dual behavior of H2O is manifest in accepting a proton from the naphthol OH while simultaneously solvating
- -Favorskii rearrangement and release of DEP is initiated at the triplet state of 14 and proceeds according to the more extensively characterized rearrangement for pHP DEP. Due to a more favorable excitation wavelength of 350 nm for 1,4-HNA (vs 280 nm for pHP), it is anticipated that the 4-hydroxy-1
Photo, thermal and chemical degradation of riboflavin
Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208
- excited triplet state of RF [24][36][59] whereas the excited singlet state plays a role in the formation of LC and CDRF [14][24][35][42]. The excitation of the RF molecule on the absorption of light takes place very rapidly as the life spans of flavin excited singlet and triplet states are approximately 5
- the involvement of two pathways causing direct formation of LC (through excited singlet state) as well as through FMF (by excited triplet state) where the dominant role is played by the excited singlet state. Such formation of LC has also been reported by Song and Metzler [80] and Cairns and Metzler
- found to be much affected by an increase in buffer concentration which could be due to the involvement of the excited triplet state in the reaction. The same may also be hypothesized for LC as some of its fractions could be formed directly from FMF [21][23][25][26][30][35]. On the contrary, some buffers
On the mechanism of photocatalytic reactions with eosin Y
Beilstein J. Org. Chem. 2014, 10, 981–989, doi:10.3762/bjoc.10.97
- redox potential can be obtained indirectly via analysis of the thermodynamic cycle involving the energy of the triplet state eosin Y* (T1) (derived from fluorescence measurements) and the energy of the radical cation eosin Y+• (derived from cyclovoltammetric experiments, for more details see Supporting
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