Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• biexponential kinetic with a longer, dominant lifetime (τ) of 1.44 ns (83%) and a minor shorter component of 0.48 ns (17%). The decay of the 2–β-CD conjugate was more complex and was fitted by a triexponential fit with lifetimes of 4.26 ns (3%), 1.77 ns (45%) and below 0.2 ns (52%). This behavior may

Highly bulky and stable geometry-constrained iminopyridines: Synthesis, structure and application in Pd-catalyzed Suzuki coupling of aryl chlorides

• Yi Lai,
• Zhijian Zong,
• Yujie Tang,
• Weimin Mo,
• Nan Sun,
• Baoxiang Hu,
• Zhenlu Shen,
• Liqun Jin,
• Wen-hua Sun and
• Xinquan Hu

Beilstein J. Org. Chem. 2017, 13, 213–221, doi:10.3762/bjoc.13.24

• ]. Alternatively, the palladacycles reported by Herrmann and Beller in the 1990s [30] effectively elongated the lifetime of the active Pd species through employing bidentate or multidentate ligands [31][32][33][34][35][36]. Meanwhile nitrogen ligands are also widely used for palladium catalysts in coupling

A self-assembled cyclodextrin nanocarrier for photoreactive squaraine

• Ulrike Kauscher and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2016, 12, 2535–2542, doi:10.3762/bjoc.12.248

• atmospheric conditions. At these conditions the concentration of oxygen in water is 1.25 mM while the concentration of oxygen in acetonitrile is between 8.1–12.1 mM, depending on the type of measurement. [39]. The lower oxygen concentration in water can enhance the lifetime of AdSq on CDV. Conclusion We

Ionic liquids as transesterification catalysts: applications for the synthesis of linear and cyclic organic carbonates

• Maurizio Selva,
• Alvise Perosa,
• Sandro Guidi and
• Lisa Cattelan

Beilstein J. Org. Chem. 2016, 12, 1911–1924, doi:10.3762/bjoc.12.181

• allows reactions to be performed under very mild conditions and with a variety of raw materials. However, the high cost and relatively short lifetime of enzymes partly offset their advantages and an implementation of biocatalytic processes makes sense almost exclusively for the preparation of high added

A flow reactor setup for photochemistry of biphasic gas/liquid reactions

• Josef Schachtner,
• Patrick Bayer and
• Axel Jacobi von Wangelin

Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170

• organic substrate and the dye, and the solubility as well as the lifetime of oxygen in its singlet state (1O2) [76]. All reactions were performed under irradiation with an energy-saving light bulb (Osram Dulux Superstar) against a back-pressure of 2.4 bar while one parameter was varied in each experiment

On the cause of low thermal stability of ethyl halodiazoacetates

• Magnus Mortén,
• Martin Hennum and
• Tore Bonge-Hansen

Beilstein J. Org. Chem. 2016, 12, 1590–1597, doi:10.3762/bjoc.12.155

• acid was employed in all experiments. The temperature dependence in toluene-d8 as solvent was found to be similar in CD2Cl2 (Table 1, entries 11–13). Next, the effect of additives on the stability of the compounds was investigated. We first tested NEt3 (not shown), inspired by the prolonged lifetime of

• bromodiazoacetate lifetime (Table 1, entries 14–18). Thus the half-life of 2b increased ~6 times in the presence of 1 equiv TMEDA in CDCl3 solution. EDA has been reported to be stable in glacial acetic acid [4]. Halodiazoesters 2a and 2b on the other hand decomposed with half-lives of approx. 33 min (2a) and 63 min

3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells

• Wei Li,
• Munechika Otsuka,
• Takehito Kato,
• Yang Wang,
• Takehiko Mori and
• Tsuyoshi Michinobu

Beilstein J. Org. Chem. 2016, 12, 1401–1409, doi:10.3762/bjoc.12.134

• carrier lifetime or time constant (τ) is related to the recombination of an electron and a hole at the interfaces between the perovskite and TiO2 or hole-transporting layers. This parameter can be calculated according to Equation 2 [47]: where f is the maximum frequency derived from the semicircle of the

• impedance spectra, also known as the character frequency. The calculated τ values are listed in Table 2. The device based on 3,6-Cbz-EDOT displayed the longest lifetime of 3.98 μs, which is almost twice as high as that of the device based on P3HT. This result can be explained by the LUMO levels of the HTMs

• prolonged carrier lifetime. It is worth noting that there is still a room for improvement of the carrier mobility and lifetime by the increase in the molecular weights of these polymers. Overall, the Cbz-EDOT polymers, especially 2,7-Cbz-EDOT, are solution-processable promising HTMs of the PSCs

Biradical vs singlet oxygen photogeneration in suprofen–cholesterol systems

• Fabrizio Palumbo,
• Francisco Bosca,
• Isabel M. Morera,
• Inmaculada Andreu and
• Miguel A. Miranda

Beilstein J. Org. Chem. 2016, 12, 1196–1202, doi:10.3762/bjoc.12.115

• luminescence at 1270 nm, using a germanium diode as detector. The singlet oxygen lifetime (Figure 7A) was found to be ca. 70 μs in all cases (in agreement with the1O2 lifetime reported in the literature [20] for the same solvent). The photosensitized singlet oxygen production was established with a quantum

Synthesis and fluorosolvatochromism of 3-arylnaphtho[1,2-b]quinolizinium derivatives

• Phil M. Pithan,
• David Decker,
• Manlio Sutero Sardo,
• Giampietro Viola and
• Heiko Ihmels

Beilstein J. Org. Chem. 2016, 12, 854–862, doi:10.3762/bjoc.12.84

• emission lifetime. Notably, a considerable number of solvatochromic molecules is based on charge-transfer (CT) processes in the excited state resulting from a pronounced donor–acceptor interplay within the fluorophore [8]. Thus, upon excitation of such compounds, a CT – or in charged species a charge shift

Dynamic behavior of rearranging carbocations – implications for terpene biosynthesis

• Stephanie R. Hare and
• Dean J. Tantillo

Beilstein J. Org. Chem. 2016, 12, 377–390, doi:10.3762/bjoc.12.41

• level, this scenario can result in bypassed intermediates, i.e., an IRC having a minimum calculated along the pathway to the product, but with a lifetime that is not long enough to allow for equilibration; some pathways/trajectories will also skirt past the deepest parts of the energy well. Additionally

• ), with no secondary carbocation found as a stationary point on the PES. However, molecular dynamics simulations initiated from the reactant revealed trajectories that predominantly followed a stepwise mechanism (Figure 5, green), with a lifetime of the secondary carbocation of up to 4000 fs. This is the

• presence of a “hidden intermediate” [47][48][49][50][51], i.e., a structure along the IRC that is not a minimum but is associated with an energy plateau and may have a substantial lifetime. Such IRCs have subsequently been observed for many reactions for which secondary carbocations are putative

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• , exploring our world together (Figure 8). Professionally, I have taken on new leadership roles at the University of Michigan and elsewhere. My lifetime love of learning has led me down a path to better understand how other people learn. This path involved starting a funded research program in chemistry

Pyridylidene ligand facilitates gold-catalyzed oxidative C–H arylation of heterocycles

• Kazuhiro Hata,
• Hideto Ito,
• Yasutomo Segawa and
• Kenichiro Itami

Beilstein J. Org. Chem. 2015, 11, 2737–2746, doi:10.3762/bjoc.11.295

• elimination steps, we believe that the strongly electron-donating PyC not only facilitates gold(I)-to-gold(III) oxidation in catalysis but also prolongs the catalyst lifetime by preventing the ligand dissociation and formation of inactive gold nanoparticles. Conclusion In summary, we have developed the

Synthesis and photophysical characteristics of polyfluorene polyrotaxanes

• Aurica Farcas,
• Giulia Tregnago,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert and
• Franco Cacialli

Beilstein J. Org. Chem. 2015, 11, 2677–2688, doi:10.3762/bjoc.11.288

• lifetime τ = 0.7 ns and 0.8 ns, whereas the 3·TM-γCD polyrotaxane shows a bi-exponential decay consisting of a main component (with a weight of 98% of the total luminescence) with a relatively short decay constant of τ1 = 0.7 ns and a minor component with a longer lifetime of τ2 = 5.4 ns (2%). The

• weights of 98 and 2%, respectively. The longer τ for the 3·TM-γCD polyrotaxane is consistent with “interchain states”. While these do not dominate the luminescence of the materials (the longer lifetime only accounts for 2% of the total PL weight), they are plausible, considered the significantly bigger

Friedel–Crafts-type reaction of pyrene with diethyl 1-(isothiocyanato)alkylphosphonates. Efficient synthesis of highly fluorescent diethyl 1-(pyrene-1-carboxamido)alkylphosphonates and 1-(pyrene-1-carboxamido)methylphosphonic acid

• Anna Wrona-Piotrowicz,
• Janusz Zakrzewski,
• Anna Gajda,
• Tadeusz Gajda,
• Anna Makal,
• Arnaud Brosseau and
• Rémi Métivier

Beilstein J. Org. Chem. 2015, 11, 2451–2458, doi:10.3762/bjoc.11.266

• species. Table 2 shows that 3a displays a slightly shorter excited state lifetime (10.6 ns) than its alkyl analogue 5 (12.3 ns). The higher emission quantum yield of 3a results from a ≈2.3 times higher value of kr and a concomitant ca. 1.8 times lower value of knr. Notably, compound 4 displays a kr value

Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

• Kazuaki Kato,
• Daisuke Matsui,
• Koichi Mayumi and
• Kohzo Ito

Beilstein J. Org. Chem. 2015, 11, 2194–2201, doi:10.3762/bjoc.11.238

• -links that have finite lifetime. On the other hand, the infinite network exhibited an abnormally low Young’s modulus, ~1 kPa, which is not explainable by traditional rubber theory. In addition, the composite gels were tough enough to completely maintain the network structure under 80% compression strain

• independent of the strain. These results clearly indicate that the silica nanocomposite polyrotaxane gels form an infinite network structure with negligible physical cross-links that have finite lifetime to exhibit stress relaxation, similar to ideal chemical gels. At the same time, the negligible relaxation

Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2015, 11, 913–929, doi:10.3762/bjoc.11.103

• residue within a nucleic acid [24][25]. This results in a hydration of 1 g of H2O per gram. However, Bloomfield et al. in 2000 [26] as well as Fernandes et al. in 2002 [23] reported hydration degrees of 0.35 [26] or 0.3 g of water per gram of nucleotide (Table 5). Confocal fluorescence lifetime analysis

• (cFLA) Next, the fluorescence lifetime values of the LONs 10–15 were measured and are listed in Figure 17A–C as well as in Table 6. The fluorescence lifetime of the free Cy5 dye is reported to be 0.91 ns [27], 1.0 ns [28][29], and 1.0–1.4 ns [30]. In the literature, fluorescence lifetimes of free Cy5

• dye attached to ssDNA as well as to dsDNA, respectively, also exist. The fluorescence lifetime, τF, of two 5’-Cy5-ssDNA conjugates were measured as 1.8 ± 0.1 ns [31] for a 36mer and a 23mer [32]. For a Cy5-labeled 25mer, a value of 1.26 ns [27] was reported. For the LONs 10–15 described here, longer

Design, synthesis and photochemical properties of the first examples of iminosugar clusters based on fluorescent cores

• Mathieu L. Lepage,
• Antoine Mirloup,
• Manon Ripoll,
• Fabien Stauffert,
• Anne Bodlenner,
• Raymond Ziessel and
• Philippe Compain

Beilstein J. Org. Chem. 2015, 11, 659–667, doi:10.3762/bjoc.11.74

• the decrease of fluorescence versus the concentration of quencher. The Stern–Volmer equation facilitates the calculation of the rates of bimolecular collisional quenching kq = 1.8 × 1013 M−1·s−1 and 1.5 × 1013 M−1·s−1, respectively for 13a and 15a dyes using a lifetime τ = 5.31 ns for the 4

Photocatalytic nucleophilic addition of alcohols to styrenes in Markovnikov and anti-Markovnikov orientation

• Martin Weiser,
• Sergej Hermann,
• Alexander Penner and
• Hans-Achim Wagenknecht

Beilstein J. Org. Chem. 2015, 11, 568–575, doi:10.3762/bjoc.11.62

• . Spectroelectrochemistry measurements (see Supporting Information File 1) revealed that the blue colored intermediate could be assigned to the radical anion of PDI as photocatalyst whose half-lifetime was determined to be approximately 4 min (Figure 3). The appearance of this intermediate strongly supported the proposed

Come-back of phenanthridine and phenanthridinium derivatives in the 21st century

• Lidija-Marija Tumir,
• Marijana Radić Stojković and
• Ivo Piantanida

Beilstein J. Org. Chem. 2014, 10, 2930–2954, doi:10.3762/bjoc.10.312

• properties in comparison to other phenanthridinium analogues by means of signal brightness, signal-to-background noise and increased fluorescence half-lifetime. The same dye was also applied as convenient reporter for si-RNA (Figure 8, right) [84]. In parallel the designed and tested covalently linked

• ethidium bromide–ruthenium(II) complex also proved to be an imaging probe whose fluorescence intensity and lifetime changes substantially in the presence of RNA [85], thus supporting a strategy of phenanthridinium incorporation into the heterogenic two-chromophore system. Phenanthridines are rarely

The effect of permodified cyclodextrins encapsulation on the photophysical properties of a polyfluorene with randomly distributed electron-donor and rotaxane electron-acceptor units

• Aurica Farcas,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert,
• Flavian Farcas,
• Iuliana Stoica and
• Anton Airinei

Beilstein J. Org. Chem. 2014, 10, 2145–2156, doi:10.3762/bjoc.10.222

• lifetime of τ2 = 1.56 ns (42.92%) were determined. The optical and electrochemical band gaps (ΔEg) as well as the ionization potential and electronic affinity characterized by smaller values compared to the values of any of the constituents. AFM reveals that the film surface of 4a and 4b displays a

• interaction between macrocyclic molecules and conjugated cores [26][40]. The decay traces of 4 non-rotaxane counterpart obtained from the fluorescence lifetime measurements follow a bi-exponential decay, which consists of a main component with a relative short time of τ1 = 0.88 (57.08%) and a minor component

• with a longer lifetime of τ2 = 1.56 ns (42.92%) (Figure S7 in Supporting Information File 1 and Table 2). The observed behavior suggests that the bi-exponential decay of the non-rotaxane 4 may be caused by the intrachain emission and excitonic lifetime, whereas in the case of the polyrotaxanes it may

The Ugi four-component reaction as a concise modular synthetic tool for photo-induced electron transfer donor-anthraquinone dyads

• Sarah Bay,
• Gamall Makhloufi,
• Christoph Janiak and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 1006–1016, doi:10.3762/bjoc.10.100

• anthraquinone-substituted aldehyde together with acetic acid and tert-butyl isocyanide for rapidly assembling a donor–acceptor conjugate 1 displaying a photo-induced electron transfer leading to a charge-separated state with a lifetime of >2 ns (Figure 1), as elucidated by femtosecond transient absorption

Tailoring of organic dyes with oxidoreductive compounds to obtain photocyclic radical generator systems exhibiting photocatalytic behavior

• Christian Ley,
• Julien Christmann,
• Ahmad Ibrahim,
• Luciano H. Di Stefano and
• Xavier Allonas

Beilstein J. Org. Chem. 2014, 10, 936–947, doi:10.3762/bjoc.10.92

• . Intersystem crossing rate constant kISC was obtained from the triplet state quantum yield and singlet state lifetime according to [59]: which leads to: and to At this RB concentration, and in the absence of quencher, the triplet state lifetime was measured around 80 µs, leading to kdes3= 1.25·104 M−1s−1

• under argon bubbling at room temperature. The quenching rate constants kq of the excited states were obtained according to the Stern–Volmer analysis where the reciprocal lifetime is plotted as a function of quencher concentration: [57]. Chemicals: Rose Bengal extra (RB) and ethyl 4-(dimethylamino

Metal and metal-free photocatalysts: mechanistic approach and application as photoinitiators of photopolymerization

• Jacques Lalevée,
• Sofia Telitel,
• Pu Xiao,
• Marc Lepeltier,
• Frédéric Dumur,
• Fabrice Morlet-Savary,
• Didier Gigmes and
• Jean-Pierre Fouassier

Beilstein J. Org. Chem. 2014, 10, 863–876, doi:10.3762/bjoc.10.83

• panchromatic behavior in the 400–650 nm range. The PIC/Ph2I+/NVK system The photochemical properties of Ir(piq)2(tmd) A triplet-state lifetime of 1.1 μs has been determined for Ir(piq)2(tmd) by laser flash photolysis experiments. A relatively similar lifetime (1.3 μs) was previously measured for 3Ir(ppy)3 [68

One-pot three-component synthesis and photophysical characteristics of novel triene merocyanines

• Christian Muschelknautz,
• Robin Visse,
• Jan Nordmann and
• Thomas J. J. Müller

Beilstein J. Org. Chem. 2014, 10, 599–612, doi:10.3762/bjoc.10.51

• the outcome of the sequence. The latter hypothesis of the iminium-ion stabilization obviously influences the lifetime of the zwitterion 13. Furthermore the enamine formed by deprotonation of 9 is a S,N-ketene acetal, which is significantly more nucleophilic than Fischer’s base (7). The higher

Flow synthesis of phenylserine using threonine aldolase immobilized on Eupergit support

• Jagdish D. Tibhe,
• Hui Fu,
• Timothy Noël,
• Qi Wang,
• Jan Meuldijk and
• Volker Hessel

Beilstein J. Org. Chem. 2013, 9, 2168–2179, doi:10.3762/bjoc.9.254

• . It was anticipated that at lower temperatures the lifetime of the immobilized enzyme would be extended and would allow long term operation of the flow system. Indeed, the product yield was almost constant at around 30–35% even after 10 hours of continuous operation (Figure 8). Here, the inhibitory