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

• -dioctylfluorene 3 and compared with those of the corresponding non-rotaxane 4 counterpart. Rotaxane formation results in improvements of the solubility, the thermal stability, and the photophysical properties. Polyrotaxanes 4a and 4b exhibited slightly red-shifted absorption bands with respect to the non-rotaxane

• “insulation” of the individual molecular wires. Moreover, recently reported results have shown improvements of the thermal stability, solubility, luminescence and surface characteristics of polyrotaxanes compared to those of non-rotaxane counterparts [8][13][19][20][21][22][23][24][25]. This approach has also

• polyrotaxanes exhibited a thermal decomposition temperature around 412 °C, whereas the thermal decomposition temperature of reference 4 was around 414 °C at 5% weight loss (Figure 4 and Table 1). It is noteworthy that the polyrotaxane formation increases the thermal stability of the macrocycle molecules

Second generation silver(I)-mediated imidazole base pairs

• Susanne Hensel,
• Nicole Megger,
• Kristina Schweizer and
• Jens Müller

Beilstein J. Org. Chem. 2014, 10, 2139–2144, doi:10.3762/bjoc.10.221

• artificial metal-mediated base pairs. We show here that its stability can be further improved by formally replacing the imidazole moiety by a 2-methylimidazole or 4-methylimidazole moiety. A comparison of the thermal stability of several double helices shows that the addition of one equivalent of Ag(I) leads

• absolute melting temperature. In the presence of one equivalent of Ag(I), the thermal stability of the duplexes increases significantly. Notably, the increase in Tm is larger by about 50% for the methylated imidazole nucleosides compared with the non-methylated one, amounting to about 8.5 °C per silver(I

• )-mediated base pair. The significantly increased thermal stability of the duplexes comprising either 2-methylimidazole or 4-methylimidazole therefore cannot be attributed to the above-mentioned hydrophobic interaction only but must also be a direct effect of the formation of the metal-mediated base pairs

Photo, thermal and chemical degradation of riboflavin

• Muhammad Ali Sheraz,
• Sadia Hafeez Kazi,
• Sofia Ahmed,
• Zubair Anwar and
• Iqbal Ahmad

Beilstein J. Org. Chem. 2014, 10, 1999–2012, doi:10.3762/bjoc.10.208

• stable complexes are formed with Zn and Ni, showing higher degradation temperatures as compared to pure RF whereas the remaining complexes showed similar or lower thermal stability to that of the pure RF with the Fe-complex found to be most rapidly degraded [161]. The presence of various metal ions

Efficient CO₂ capture by tertiary amine-functionalized ionic liquids through Li⁺-stabilized zwitterionic adduct formation

• Zhen-Zhen Yang and
• Liang-Nian He

Beilstein J. Org. Chem. 2014, 10, 1959–1966, doi:10.3762/bjoc.10.204

• . These efforts include the development of liquid and solid absorbents and membranes [2][3][4][5][6][7]. Ionic liquids (ILs), which have attractive properties such as negligible vapor pressure, a wide liquid temperature ranges, good thermal stability, high ionic conductivity, and versatile solvation

• . The thermal stability of the chelated ILs was strongly increased compared to the corresponding neutral ligands. The decomposition temperature increased by 90 °C and 60 °C for PEG150MeTMG and PEG150MeBu2N, respectively, after coordination with LiNTf2 (Figure 2a). In the 1H NMR spectrum, the proton

• . Indeed, the thermal stability and the CO2 capacity of the neutral ligands (e.g., PEG150MeBu2N) was highly increased after coordination with lithium salts to form chelated ILs (e.g., [PEG150MeBu2NLi][NTf2]). Experimental Materials All reagents used in this work were purchased from Sigma-Aldrich and used

Aryl substitution of pentacenes

• Andreas R. Waterloo,
• Anna-Chiara Sale,
• Dan Lehnherr,
• Frank Hampel and
• Rik R. Tykwinski

Beilstein J. Org. Chem. 2014, 10, 1692–1705, doi:10.3762/bjoc.10.178

• (vide infra). Thermal analysis The thermal stability of selected aryl pentacenes has been explored by traditional melting point analysis (MPA) in open capillary tubes, thermal gravimetric analysis (TGA), and differential scanning calorimetry (DSC) measurements; the results are summarized in Table 2. TGA

Improving the reactivity of phenylacetylene macrocycles toward topochemical polymerization by side chains modification

• Simon Rondeau-Gagné,
• Jules Roméo Néabo,
• Maxime Daigle,
• Katy Cantin and
• Jean-François Morin

Beilstein J. Org. Chem. 2014, 10, 1613–1619, doi:10.3762/bjoc.10.167

• groups lead to a significant decrease of solubility, even in hot solvents, limiting the formation of organogels. In order to investigate the crystallization temperature of solvents within the gel and to compare the influence of the 2-hydroxyethoxy side chains on the thermal stability of the gel, two gel

Photoswitchable precision glycooligomers and their lectin binding

• Daniela Ponader,
• Sinaida Igde,
• Marko Wehle,
• Katharina Märker,
• Mark Santer,
• David Bléger and
• Laura Hartmann

Beilstein J. Org. Chem. 2014, 10, 1603–1612, doi:10.3762/bjoc.10.166

• phenylamine one for two reasons: first, its higher nucleophilicity allows for a smoother synthesis and second, the resulting Z-azobenzene exhibits a high thermal stability as compared to the fully conjugated push-pull azobenzene based on the phenylamine fragment. In total, five precision glycooligomers were

• , demonstrating the reversibility of the systems. Finally, the thermal stability of Z-Azo-Gal(1,3)-3 in the buffer solution is quite high. Indeed, after 48 h at 25 °C only 12% of the Z-isomers converted back to the E-isomer (see Supporting Information File 1). The thermal stability of the trivalent Azo-Gal(1,3,5

Influence of perylenediimide–pyrene supramolecular interactions on the stability of DNA-based hybrids: Importance of electrostatic complementarity

• Christian B. Winiger,
• Simon M. Langenegger,
• Oleg Khorev and
• Robert Häner

Beilstein J. Org. Chem. 2014, 10, 1589–1595, doi:10.3762/bjoc.10.164

• pyrene–pyrene interactions, whereas duplex 1*6 has the maximum number pyrene–PDI interactions. Thermal denaturation experiments Thermal denaturation experiments revealed a clear trend in duplex stability (Figure 2). The thermal stability correlates with the number of pyrene–PDI interactions [56] and

Pyrene-modified PNAs: Stacking interactions and selective excimer emission in PNA₂DNA triplexes

• Alex Manicardi,
• Lucia Guidi,
• Alice Ghidini and
• Roberto Corradini

Beilstein J. Org. Chem. 2014, 10, 1495–1503, doi:10.3762/bjoc.10.154

• using standard Fmoc-based manual solid phase protocol. The crude products were purified by RP-HPLC and characterized by HPLC–UV–MS (Supporting Information File 1, Figures S6–S11). Thermal stability of PNA:DNA complexes The introduction of a modification in a PNA stand can lead to different effects

• the presence of DNA was found to be in accordance with the UV melting measurements (Supporting Information File 1, Figure S15). Fluorescence studies Beside the modification of thermal stability and selectivity induced by the incorporation of pyrene moieties described above, we evaluated the

• hybridization, a property which is very important also in the case of more elaborated methods such as gated detection. These characteristics make PNA2 a very good fluorescent probe, with very high single-base selectivity in both thermal stability and excimer formation upon binding to target DNA. Thus, the

Multichromophoric sugar for fluorescence photoswitching

• Stéphane Maisonneuve,
• Rémi Métivier,
• Pei Yu,
• Keitaro Nakatani and
• Juan Xie

Beilstein J. Org. Chem. 2014, 10, 1471–1481, doi:10.3762/bjoc.10.151

• photostationary state (PSS) under 335 nm illumination, isolated 9-CF; (d) emission spectrum of 9-OF (λexc = 325 nm); (e) absorption spectra of 2-OF, 2 at the photostationary state (PSS) under 335 nm illumination (no noticeable change has been observed over 5 days, indicating the thermal stability of 2), 2-CF

Solid-phase-supported synthesis of morpholinoglycine oligonucleotide mimics

• Tatyana V. Abramova,
• Sergey S. Belov,
• Yulia V. Tarasenko and
• Vladimir N. Silnikov

Beilstein J. Org. Chem. 2014, 10, 1151–1158, doi:10.3762/bjoc.10.115

• positively charged centers in oligonucleotide analogues results in increased water solubility and higher thermal stability of complementary duplexes of such oligonucleotide mimics with nucleic acids [14][15]. Some conformationally restricted protonated PNA or pyrrolidine oligonucleotide mimics exhibit

• dependence of the thermal stability of complementary complexes formed by the MorGly oligomers on the heterocyclic base composition (uracil or adenine) of the modified chain. It was shown while studying their tandem complexes that the impact of cooperative interactions at oligomer junctions on the thermal

• stability was higher for modified oligomers than for native oligodeoxyriboadenylates. This result may indicate that the contribution of nucleobase stacking to the thermal stability of complementary complexes is more important for the oligonucleotide mimics than for native oligonucleotides. The substitution

The influence of intraannular templates on the liquid crystallinity of shape-persistent macrocycles

• Joscha Vollmeyer,
• Ute Baumeister and
• Sigurd Höger

Beilstein J. Org. Chem. 2014, 10, 910–920, doi:10.3762/bjoc.10.89

• substituents influence the thermal stability of the gel. As pointed out before, the ring interior can also have a dramatic effect on the mesophase stability of thermotropic liquid crystalline shape-persistent macrocycles [40][43][44][45]. However, more detailed studies on that issue are still scarcely found in

N-Alkylated dinitrones from isosorbide as cross-linkers for unsaturated bio-based polyesters

• Oliver Goerz and
• Helmut Ritter

Beilstein J. Org. Chem. 2014, 10, 902–909, doi:10.3762/bjoc.10.88

• . Efforts have also been undertaken to employ nitrones in the realm of polymer chemistry. For instance, our former reports describe the cycloaddition of bis(N-methylnitrone)s and bis(N-phenylmaleimide)s , which yielded linear polymers bearing isoxazolidine units with high thermal stability [6]. The

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

• Yuta Takano,
• Yuki Nagashima,
• M. Ángeles Herranz,
• Nazario Martín and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

• demonstrated the boat-to-boat inversions of the addend. In addition, 5b revealed remarkable thermal stability in comparison with the reported [4 + 2] cycloadduct of pentamethylcyclopentadiene and La@C82 (6). These findings demonstrate the utility of sultines to afford thermodynamically stable endohedral

• , respectively, was achieved by the selective thermal decomposition of unstable isomers. The thermal stability of 5b was also evaluated in comparison with 6, and 5b shows remarkable thermal stability. The molecular structures of the resulting compounds were characterized by spectroscopic analyses. Dynamic 1H NMR

Total synthesis and cytotoxicity of the marine natural product malevamide D and a photoreactive analog

• Werner Telle,
• Gerhard Kelter,
• Heinz-Herbert Fiebig,
• Peter G. Jones and
• Thomas Lindel

Beilstein J. Org. Chem. 2014, 10, 316–322, doi:10.3762/bjoc.10.29

• ) and acidic deprotection afforded diazirine diol 25. Figure 2 shows the DSC (differential scanning calorimetry) profile of 25, which melts at 54 °C and starts to decompose above 80 °C, indicating sufficient thermal stability for biological studies. Monosilylation of the primary hydroxy group of 25

Cyclic phosphonium ionic liquids

• Sharon I. Lall-Ramnarine,
• Joshua A. Mukhlall,
• James F. Wishart,
• Robert R. Engel,
• Alicia R. Romeo,
• Masao Gohdo,
• Sharon Ramati,
• Marc Berman and
• Sophia N. Suarez

Beilstein J. Org. Chem. 2014, 10, 271–275, doi:10.3762/bjoc.10.22

• synthesize ILs with improved properties (such as viscosity, thermal stability, melting point, etc.) to expand their applications into larger scale processes in diverse areas. Along that vein, phosphonium ILs have been observed to have favorable characteristics, including lower costs [2][3][4][5][6], lower

• viscosity (by ~50%) [7][8][9][10][11], greater thermal stability (by ~100 °C) [10][11][12], and wider electrochemical windows compared to their ammonium congeners. The family of ILs bearing cyclic cations (pyrrolidinium, piperidinium, and azepanium) [13][14] have been shown to have better transport and

• cations have greater thermal stability than the ammonium ones. One trend observed for both cation types is that the ILs with five-membered rings have greater thermal stability than those with six-membered rings. Further work will be required to determine if the observed TGA behaviors are due to actual

Synthesis, characterization and initial evaluation of 5-nitro-1-(trifluoromethyl)-3H-1λ³,2-benziodaoxol-3-one

• Nico Santschi,
• Roman C. Sarott,
• Elisabeth Otth,
• Reinhard Kissner and
• Antonio Togni

Beilstein J. Org. Chem. 2014, 10, 1–6, doi:10.3762/bjoc.10.1

• . Consequently in light of these results, DSC measurements of 2 and 3 were carried out in order to assess the thermal stability of the new derivative. These measurements were performed in punctured Al2O3 pans with a heating rate of 10 K/min. For reagent 2, a decomposition energy of 138 kJ/mol (438 J/g, slightly

• lability of 3 was noted such that it decayed almost one order of magnitude faster than 2 under similar conditions. Therefore, the incorporation of an electron-withdrawing group into the reagent scaffold leads to an enhanced thermal stability that is paralleled by increased lability of the I–CF3 bond under

Charge-transfer interaction mediated organogels from 18β-glycyrrhetinic acid appended pyrene

• Jun Hu,
• Jindan Wu,
• Qian Wang and
• Yong Ju

Beilstein J. Org. Chem. 2013, 9, 2877–2885, doi:10.3762/bjoc.9.324

• in the formation of CT gels is demonstrated through the formation of gels in a variety of solvents. Thermal stability, stoichiometry, scanning electron microscopy (SEM), optical micrographs, and circular dichroism (CD) are performed on these CT gels to investigate their thermal and assembly

• observation suggested the presence of a CT complex in the gel system. Thermal stability Sol to gel transition temperature (Tgel) was measured as a function of the total concentration of the 1:1 (molar ratio) donor–acceptor mixture. These were done by inverted test tube experiments after gels were stabilized

• in sealed test tubes for 1–2 h [15][48][49][50]. It was observed that the thermal stability of these CT gels based on 3 and 4 increased with an increase in the total concentration (Figure 2), no matter in what kind of solvent. Based on the Tgel values at different concentrations, the thermodynamic

Less reactive dipoles of diazodicarbonyl compounds in reaction with cycloaliphatic thioketones – First evidence for the 1,3-oxathiole–thiocarbonyl ylide interconversion

• Valerij A. Nikolaev,
• Alexey V. Ivanov,
• Ludmila L. Rodina and
• Grzegorz Mlostoń

Beilstein J. Org. Chem. 2013, 9, 2751–2761, doi:10.3762/bjoc.9.309

• 3b was two times lower (Table 1, entry 2). Increasing the temperature to 80 °C slightly speeded up the process. However, due to the relatively low thermal stability of diazodiketone 2b [7][8][18], side reactions resulting in the formation of oxathiinone 4b (17%) and tetrasubstituted olefin 5b (11

• additional signals could be observed. To clarify the possibility of a thermal decomposition of the diazodicarbonyl compounds and the alternative ‘carbene pathway’ (C), the thermal stability of a series of diazo compounds 2 was examined [7][8][17]. The obtained results allow us to conclude that at room

Stereoselectively fluorinated N-heterocycles: a brief survey

• Xiang-Guo Hu and
• Luke Hunter

Beilstein J. Org. Chem. 2013, 9, 2696–2708, doi:10.3762/bjoc.9.306

• -exo ring pucker of 12 was demonstrated in spectacular fashion: Raines and co-workers showed that the thermal stability of collagen was increased when 12 was incorporated in place of collagen’s naturally-present (4R)-hydroxyproline residues [25]. This hyperconjugation effect has also been exploited in

Recent advances in transition metal-catalyzed Csp²-monofluoro-, difluoro-, perfluoromethylation and trifluoromethylthiolation

• Grégory Landelle,
• Armen Panossian,
• Sergiy Pazenok,
• Jean-Pierre Vors and
• Frédéric R. Leroux

Beilstein J. Org. Chem. 2013, 9, 2476–2536, doi:10.3762/bjoc.9.287

• trifluoromethylations and the recent results of the Cu-catalyzed reaction described above, that of difluoromethylation has been more slowly developed. This is probably due to the lack of thermal stability of CuCHF2 [42]. To the best of our knowledge, the direct cross-coupling of CuCHF2 with aromatic halides has not

Biosynthesis of rare hexoses using microorganisms and related enzymes

• Zijie Li,
• Yahui Gao,
• Hideki Nakanishi,
• Xiaodong Gao and
• Li Cai

Beilstein J. Org. Chem. 2013, 9, 2434–2445, doi:10.3762/bjoc.9.281

• extensively studied, particularly from D-galactose by L-arabinose isomerase (AI, EC 5.3.1.4) (Scheme 1) [14][15][16][17][18][19][20]. As the interconversion equilibrium between D-galactose and D-tagatose shifts toward D-tagatose at higher temperatures, biocatalysts with greater thermal stability are preferred

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

• enzyme. This multipoint attachment provides enhanced conformational stability, which translates to long term operational stability. Fu et al. have already investigated the thermal stability of TA on different supports [48] and found that the enzyme stability increases after immobilization on Eupergit

• support. In continuation of our previous work [48], this paper includes further investigation of the thermal stability of TA on Eupergit by a so-called direct and indirect method. Also, a flow synthesis of Eupergit-immobilized TA in a packed bed microreactor was established and compared to the use of free

• demonstrate a high activity to those reported in the literature. There, only 52.4% enzyme retention and activity retention of 20.7% were achieved while for the indirect method 37% enzyme loading with 31% of activity retention was observed [49]. Comparison of thermal stability of TA immobilized by two

Sequential Diels–Alder/[3,3]-sigmatropic rearrangement reactions of β-nitrostyrene with 3-methyl-1,3-pentadiene

• Peter A. Wade,
• Alma Pipic,
• Matthias Zeller and
• Panagiota Tsetsakos

Beilstein J. Org. Chem. 2013, 9, 2137–2146, doi:10.3762/bjoc.9.251

• well involve zwitterion 15 as the intermediate since nitronic esters 5 and 6 equilibrate under these conditions presumably through 15. The thermal stability of nitronic esters 4–7 appears to be roughly similar to nitronic esters 2 and 3: all have half-life’s greater than one hour at 100 °C with the

Synthesis of enantiomerically pure (2S,3S)-5,5,5-trifluoroisoleucine and (2R,3S)-5,5,5-trifluoro-allo-isoleucine

• Holger Erdbrink,
• Elisabeth K. Nyakatura,
• Susanne Huhmann,
• Ulla I. M. Gerling,
• Dieter Lentz,
• Beate Koksch and
• Constantin Czekelius

Beilstein J. Org. Chem. 2013, 9, 2009–2014, doi:10.3762/bjoc.9.236

• CF3 resulted in an approximately eight-fold higher thermal stability of the respective GCN4 analogue than the replacement of the γ-CH3 group of Val by CF3 [12]. This finding was explained by the substantial loss of side-chain entropy of Val due to steric restriction between the significantly larger γ