Unexpected polymorphism during a catalyzed mechanochemical Knoevenagel condensation

• Sebastian Haferkamp,
• Andrea Paul,
• Adam A. L. Michalchuk and
• Franziska Emmerling

Beilstein J. Org. Chem. 2019, 15, 1141–1148, doi:10.3762/bjoc.15.110

• concentrations of catalyst. To better observe this transformation pathway, the reaction (2 µL catalyst) was repeated at 30 Hz in order to extend the lifetime of m3a. The in situ XRPD pattern and Raman spectra are shown in Figure 4b and d, respectively. Decreasing the milling frequency has a number of notable

• effects. First, the lifetime of the initial molten/liquid phase was nearly doubled, suggesting that mechanical treatment has an important effect on this largely solution-phase reaction. This may be a result of heating, mechanical activation of the fluid-phase molecules or differences in energy for

• nucleation. While further work is required in this area, it is clear that mechanical treatment can have notable influence on ‘solution-phase’ chemistry. Second, the lifetime of the intermediate phase was extended. This allowed us to collect higher resolution XRPD data by extracting a sample from the milling

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• concentration (1 × 10−4 M) for all dyes. The kinetic data were found to fit well to a single exponential function (Equation 1), giving a rate constant (k) corresponding to a lifetime (1/k) [18]: where A0 and A∞, are the initial and final absorptions, A is the absorption at 500 nm at a time t after termination

• dyes are summarized in Table 2. Generally, the addition of Ba2+ ions was found to increase substantially the lifetime of the cis isomers. Under the abovementioned conditions the cis-4b–Ba2+ complex was detected to be most stable, while dye 4d formed stable cis-4d–Ba2+ complex only at a higher

• ) → LUMO (lowest unoccupied molecular orbital) transitions. The simulated spectra with spectral lifetime broadening (Gaussian function) with a full width at half-maximum (FWHM) of 0.15 eV and a height proportional to the oscillator strength for each transition spectrum for dye 4b and its Ba2+ complex

Photochemical generation of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical from caged nitroxides by near-infrared two-photon irradiation and its cytocidal effect on lung cancer cells

• Ayato Yamada,
• Manabu Abe,
• Yoshinobu Nishimura,
• Shoji Ishizaka,
• Masashi Namba,
• Taku Nakashima,
• Kiyofumi Shimoji and
• Noboru Hattori

Beilstein J. Org. Chem. 2019, 15, 863–873, doi:10.3762/bjoc.15.84

• reactivity of the singlet excited states of 2a and 2b. Time-correlated single photon counting (TCSPC) measurement was performed at 298 K in DMSO to estimate the fluorescence lifetime (τ) of 2 and 5 (Table 1). Single-exponential decay curves were observed for 5a and 5b, respectively (Supporting Information

• irradiation (Figure 2h). In DMSO, the quantum yield for the formation of TEMPO increased significantly to 13.1% (from 2a) and 12.8% (from 2b) at ≈1% conversion of 2 under atmospheric conditions (Figure 1). The notable effect of the solvent on the TEMPO generation may be due to the increase in the lifetime of

Catalysis of linear alkene metathesis by Grubbs-type ruthenium alkylidene complexes containing hemilabile α,α-diphenyl-(monosubstituted-pyridin-2-yl)methanolato ligands

• Tegene T. Tole,
• Johan H. L. Jordaan and
• Hermanus C. M. Vosloo

Beilstein J. Org. Chem. 2019, 15, 194–209, doi:10.3762/bjoc.15.19

• Grubbs 2-type (5) metal carbenes with pyridinyl alcoholato ligands for the 1-octene metathesis reaction (Figure 3) [10][11][12][13][14]. The incorporation of pyridinyl-alcoholato ligands in the Grubbs-type precatalysts has shown an increase in the thermal stability, activity and lifetime of the

N-Arylphenothiazines as strong donors for photoredox catalysis – pushing the frontiers of nucleophilic addition of alcohols to alkenes

• Fabienne Speck,
• David Rombach and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2019, 15, 52–59, doi:10.3762/bjoc.15.5

• fast access to a wide variety of catalysts. Recently it was shown that the radical cation of the photoredox catalyst can play a key role in photoinduced oxidation chemistry [16]. This is rather unusual due to the usually short lifetime of radical cations in solution attributed to their low-lying

Degenerative xanthate transfer to olefins under visible-light photocatalysis

• Atsushi Kaga,
• Xiangyang Wu,
• Joel Yi Jie Lim,
• Hirohito Hayashi,
• Yunpeng Lu,
• Edwin K. L. Yeow and
• Shunsuke Chiba

Beilstein J. Org. Chem. 2018, 14, 3047–3058, doi:10.3762/bjoc.14.283

• agreement with the lower process efficiency (Table 1, entry 1) observed in the reaction with fac-Ir(ppy)3 (6) that possesses a lower triplet energy (ET = 55.2 kcal/mol [50]). The optimal photocatalyst 8 [47] has a longer excited state lifetime than 7 does [46], suggesting that the lifetime of the excited

• = 1.25 × 107 M−1s−1 (see Supporting Information File 1). On the other hand, the addition of 1-octene (2a, 40 mM), in place of xanthate 1a, resulted in only a small PL quenching of photocatalyst 8 (<8%, Figure 1B). The time-resolved PL lifetime decay profiles of photocatalyst 8 (25 μM solution in degassed

• DMSO, 410 nm pulse excitation and monitoring emission at 480 nm) were recorded in the absence of a quencher, and in the presence of xanthate 1a and 1-octene (2a, 40 mM, Figure 1C). The lifetime profiles were described using a mono-exponential decay function with a lifetime of 1.40 μs in the absence of

Organometallic vs organic photoredox catalysts for photocuring reactions in the visible region

• Aude-Héloise Bonardi,
• Frédéric Dumur,
• Guillaume Noirbent,
• Jacques Lalevée and
• Didier Gigmes

Beilstein J. Org. Chem. 2018, 14, 3025–3046, doi:10.3762/bjoc.14.282

• react, the PC must have a lifetime of its triplet excited state that is long enough. The bond dissociation energy of the Si–H of (TMS)3SiH has been calculated: 79.8 kcal/mol (methods of calculation optimized at the B3LYP/6-31G* level as referred in [32]). Polymerization performances of photoredox

• cycles can be observed with Ru(bpy)3. Other ruthenium complexes which can be used into photocatalytical cycles have been described in the literature and more particularly with other type of ligands. Modification of the ligands has an influence on the redox potentials and the lifetime of the excited

• photopolymerization initiation as shown in [53] (see Part 3). For this purpose, the Ir complex was more interesting than the Ru one because of the longer excited state lifetime, lower oxidation potential leading to higher interaction rate constants with additives used for ring-opening photopolymerization (e.g

Photocatalyic Appel reaction enabled by copper-based complexes in continuous flow

• Clémentine Minozzi,
• Jean-Christophe Grenier-Petel,
• Shawn Parisien-Collette and
• Shawn K. Collins

Beilstein J. Org. Chem. 2018, 14, 2730–2736, doi:10.3762/bjoc.14.251

• of −1.93 V vs. SCE, much greater than that of Ru(bpy)3+2 (−0.81 V vs SCE), albeit the copper complex has a much shorter excited state lifetime (≈4 ns vs ≈1100 ns for Ru(bpy)3+2). The excited state reduction potential should match favorably with CBr4 (E½ = 0.30 V vs SCE) in DMF [29]. Note that many of

Learning from B₁₂ enzymes: biomimetic and bioinspired catalysts for eco-friendly organic synthesis

• Keishiro Tahara,
• Ling Pan,
• Toshikazu Ono and
• Yoshio Hisaeda

Beilstein J. Org. Chem. 2018, 14, 2553–2567, doi:10.3762/bjoc.14.232

• (II) species and an alkyl radical intermediate A [54]. The prolonged lifetime of the radical intermediate A could be provided by the channel of MOF, enabling conversion to the acetyl-migrated radical B. The radicals A and B may abstract hydrogen radicals to form the reduced product and the acetyl

Synergistic electrodeposition of bilayer films and analysis by Raman spectroscopy

• Saadeldin E. T. Elmasly,
• Luca Guerrini,
• Joseph Cameron,
• Alexander L. Kanibolotsky,
• Neil J. Findlay,
• Karen Faulds and
• Peter J. Skabara

Beilstein J. Org. Chem. 2018, 14, 2186–2189, doi:10.3762/bjoc.14.191

• two layers. Successful PEDOT/PEDTT bilayer formation has been confirmed by Raman spectroscopy. Electrodeposition of the bilayer has advantages over traditional processing methods including avoiding the acidity of PSS which is detrimental to the lifetime of devices containing PEDOT:PSS [18] and the

Applications of organocatalysed visible-light photoredox reactions for medicinal chemistry

• Michael K. Bogdos,
• Emmanuel Pinard and
• John A. Murphy

Beilstein J. Org. Chem. 2018, 14, 2035–2064, doi:10.3762/bjoc.14.179

• process through which energy is transferred between chromophores via non-radiative dipole–dipole coupling. It is generally assumed that the non-radiative processes occur at a much slower rate than radiative processes. As such, the lifetime of S1 (τs1) is roughly equal to the lifetime of fluorescence (τf

• comparable to or larger than the Φf and, more importantly, the rate constant for ISC (kISC) must be similar to the rate constant for fluorescence (kf). The lifetime of the T1 state (τT1) is generally orders of magnitude longer than the timescale of electron transfer (ET), meaning that τT1 does not alter the

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• luminescence lifetime and determined the quantum yield of luminescence under air and argon atmosphere for conjugate 9 and reference [Ru(TAP)2phen]2+ in water with 5% DMSO in order to avoid any formation of aggregates. The data gathered in Table 1 clearly indicate that the tethering of the [Ru(TAP)2phen]2

• excited state lifetime of conjugate 9 as function of the concentration of guanosine monophosphate (GMP, Figure 4). Stern–Volmer analyses indicate that a dynamic quenching is occurring, with a quenching rate close to the diffusion limit (kQ = 5.6 108 M−1s−1 in intensity and kQ = 5.3 108 M−1s−1 in lifetime

• -SPC) technique with the Edinburgh Instruments LifeSpecII Picosecond Fluorescence Lifetime Spectrometer equipped with a laser diode (λ = 439 nm, pulse = 100 ps). The samples were thermostatted at 20 ± 2 °C with a Haake Model NB22 temperature controller. The data were collected by a multichannel

Natural and redesigned wasp venom peptides with selective antitumoral activity

• Marcelo D. T. Torres,
• Gislaine P. Andrade,
• Roseli H. Sato,
• Cibele N. Pedron,
• Tania M. Manieri,
• Giselle Cerchiaro,
• Anderson O. Ribeiro,
• Cesar de la Fuente-Nunez and
• Vani X. Oliveira Jr.

Beilstein J. Org. Chem. 2018, 14, 1693–1703, doi:10.3762/bjoc.14.144

• , Cambridge, 02139, MA, United States of America 10.3762/bjoc.14.144 Abstract About 1 in 8 U.S. women (≈12%) will develop invasive breast cancer over the course of their lifetime. Surgery, chemotherapy, radiotherapy, and hormone manipulation constitute the major treatment options for breast cancer. Here, we

The phenyl vinyl ether–methanol complex: a model system for quantum chemistry benchmarking

• Dominic Bernhard,
• Fabian Dietrich,
• Mariyam Fatima,
• Cristóbal Pérez,
• Hannes C. Gottschalk,
• Axel Wuttke,
• Ricardo A. Mata,
• Martin A. Suhm,
• Melanie Schnell and
• Markus Gerhards

Beilstein J. Org. Chem. 2018, 14, 1642–1654, doi:10.3762/bjoc.14.140

• temporally overlapping laser pulses, the spectrum contains transitions from the S0 state, the electronically excited (S1, at 3637 cm−1) and also the ionic D0 state (at 3667 cm−1). This could not be avoided, as the lifetime of the excited state, which is estimated to be in the order of 5–7 ns, is shorter than

Recent advances in phosphorescent platinum complexes for organic light-emitting diodes

• Cristina Cebrián and
• Matteo Mauro

Beilstein J. Org. Chem. 2018, 14, 1459–1481, doi:10.3762/bjoc.14.124

• ) derivatives undoubtedly play leading roles as electro-active materials in light-emitting devices. Their outstanding photophysical and electrochemical features enabled fabrication of PhOLEDs and LEECs [11] with enhanced device performances in terms of efficiency, operating lifetime and colour purity. In

• shorter exciton lifetime that contributes to reduce detrimental nonradiative processes such as triplet–triplet annihilation (TTA) and triplet–polaron annihilation (TPA). On the other hand, strong σ-donor NHC carbenes ligands could be regarded as the neutral variant of phenylate-like counterparts [28][29

• electroluminescence with remarkable estimated 97% operational lifetime, LT97, over 600 hours at 1000 cd cm−2 and peak EQE of 10.8%. Nonetheless, further improvement of the device efficiency upon variation of host material increased the EQE value up to 21.5% when a dopant concentration of 2 wt % and the ambipolar

One hundred years of benzotropone chemistry

• Arif Dastan,
• Haydar Kilic and
• Nurullah Saracoglu

Beilstein J. Org. Chem. 2018, 14, 1120–1180, doi:10.3762/bjoc.14.98

Two novel blue phosphorescent host materials containing phenothiazine-5,5-dioxide structure derivatives

• Feng-Ming Xie,
• Qingdong Ou,
• Qiang Zhang,
• Jiang-Kun Zhang,
• Guo-Liang Dai,
• Xin Zhao and
• Huai-Xin Wei

Beilstein J. Org. Chem. 2018, 14, 869–874, doi:10.3762/bjoc.14.73

• lifetime. Carbazole groups are widely used in host materials because of their high triplet energy levels and high hole mobility [15]. The Lee group [16] linked carbazolyl groups to diphenyl phosphoramines to design asymmetric (9-phenyl-9H-carbazole-2,5-diyl)bis(diphenylphosphine oxide) (PCPOs) with a

• intermolecular forces of molecules. The high thermal values ensure high thermostability and that the amorphous structure can form homogeneous and stable films by vacuum deposition to improve the lifetime of the PhOLEDs. The photophysics, electrochemical and thermal properties of CEPDO and CBPDO are summarized in

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

• intermediate [31]. The lifetime for the dianionic pentacoordinated species obtained by the attack of the hydroxide ion on the phosphorus has been argued to represent an energy minimum between the transition states for the attack of HO− and the departure of EtO− and to have a lifetime of 1 picosecond. With

• leaving groups that are less basic than EtO−, such as 5´-O− of nucleoside, the lifetime expectedly is shorter. If the leaving group is very good, such as an aryl group, a synchronous concerted mechanism (ANDN) may take over the stepwise mechanism (AN + DN). Model compounds and experimental tools Studies

D–A–D-type orange-light emitting thermally activated delayed fluorescence (TADF) materials based on a fluorenone unit: simulation, photoluminescence and electroluminescence studies

• Lin Gan,
• Xianglong Li,
• Xinyi Cai,
• Kunkun Liu,
• Wei Li and
• Shi-Jian Su

Beilstein J. Org. Chem. 2018, 14, 672–681, doi:10.3762/bjoc.14.55

• lifetime of the prompt and delayed components of the time-resolved transient PL decay curves at room temperature, the PLQY of their respective components and rate constant of different kinetic processes were calculated, as shown in Table 4. The rate constants were calculated following Equations 1–4 below

Heterogeneous Pd catalysts as emulsifiers in Pickering emulsions for integrated multistep synthesis in flow chemistry

• Katharina Hiebler,
• Georg J. Lichtenegger,
• Manuel C. Maier,
• Eun Sung Park,
• Renie Gonzales-Groom,
• Bernard P. Binks and
• Heidrun Gruber-Woelfler

Beilstein J. Org. Chem. 2018, 14, 648–658, doi:10.3762/bjoc.14.52

• and lifetime. Apart from that, ligand-free Pd catalysts are also known in the literature [11][12]. However, homogeneous Pd catalysis often requires catalyst loadings in the order of mol % to achieve effective coupling and suffers from catalyst re-use and recycling problems [11][13]. Furthermore

Recent advances on organic blue thermally activated delayed fluorescence (TADF) emitters for organic light-emitting diodes (OLEDs)

• Thanh-Tuân Bui,
• Fabrice Goubard,
• Malika Ibrahim-Ouali,
• Didier Gigmes and
• Frédéric Dumur

Beilstein J. Org. Chem. 2018, 14, 282–308, doi:10.3762/bjoc.14.18

• dramatic efficiency roll-off at high current density was observed, as the result of a long TADF lifetime (270 μs). This issue was addressed with D4 [41]. By replacing the tert-butyl groups of D3 by methoxy groups in D4, a significant decrease of ΔEST was obtained (0.21 eV instead of 0.32 eV for D3

• ), reducing the TADF lifetime and efficiency roll-off. More precisely, the higher electron-donating ability and the longer conjugation length of the 3,6-dimethoxycarbazole compared to the 3,6-di-tert-butylcarbazole lowered the S1 state and to a greater extend the T1 state of D4, furnishing in turn a molecule

• with a smaller ΔEST than D3. Jointly, due to the reduction of ΔEST, a TADF lifetime of 93 μs was determined for D4, far from the value measured for D3 (270 μs). When tested in a similar device structure than that previously used for D3, a maximum EQE of 14.5% and a smaller efficiency roll-off was

Fluorogenic PNA probes

• Tirayut Vilaivan

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

• monomer–excimer switching beacons are also fluorescent in the unbound state, and therefore it is possible to monitor the success of cellular delivery. In the case of pyrene monomer–excimer switching, the long fluorescence lifetime of the pyrene excimers allows facile elimination of background signals from

Fluorescent nucleobase analogues for base–base FRET in nucleic acids: synthesis, photophysics and applications

• Mattias Bood,
• Sangamesh Sarangamath,
• Moa S. Wranne,
• Morten Grøtli and
• L. Marcus Wilhelmsson

Beilstein J. Org. Chem. 2018, 14, 114–129, doi:10.3762/bjoc.14.7

• decays of tC are all monoexponential in single- as well as in double-stranded DNA resulting in a single lifetime of 5–7 ns depending on the sequence surroundings [30]. For tCO single-stranded surroundings generally result in biexponential decays, whereas duplex surroundings, as in the case for tC, result

Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

• Carmen Moreno-Marrodan,
• Francesca Liguori and
• Pierluigi Barbaro

Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73

• terms of productivity per unit active metal, volume or time, absence of additives or catalyst lifetime [26][27]. In the present paper we shortly review the heterogeneous catalytic systems engineered for the partial hydrogenation reaction of substituted and unsubstituted alkynes under continuous flow and

Membrane properties of hydroxycholesterols related to the brain cholesterol metabolism

• Malte Hilsch,
• Ivan Haralampiev,
• Peter Müller,
• Daniel Huster and
• Holger A. Scheidt

Beilstein J. Org. Chem. 2017, 13, 720–727, doi:10.3762/bjoc.13.71

• astrocytes and neurons [5]. The tight control of the cholesterol concentration and homeostasis is of paramount importance for the functions of all cells of the body but particularly for the brain. More so as the rate of cholesterol accumulation and synthesis is subject to subtle alterations over the lifetime